The posterior aspect of the shoulder is covered by two muscular sleeves. The posterior part of the deltoid muscle forms the outer sleeve of muscle. The inner sleeve consists of two muscles of the rotator cuff, the INFRASPINATUS and TERES MINOR. The INFRASPINATUS muscle occupies and takes origin the medial three fourths of infraspinous fossa of scapula. It is inserted into the central facet on greater tuberosity of humerus. The infraspinatus forms its tendon just before crossing the back of the shoulder joint, a small bursa lies between the muscle and the posterior aspect of the scapular neck to help the tendon glide over the bone. The muscle also inserts into the capsule of the shoulder join, mechanically increasing the capsule’s strength. The TERES MINOR runs side by side with the infraspinatus. Its fibers run parallel with one another in contrast to the multipennate fibers of the supraspinatus, a difference that may help you pick up the interval between the two muscles. The AXILLARY NERVE enters the muscle from it inferior border. The superior border (the boundary between the infraspinatus and the teres minor) is, therefore, the safe side of the muscle.
The axillary nerve is a branch of the posterior cord of the brachial plexus. It runs down along the posterior wall of the axilla on the surface of the subscapularis muscle. The nerve then runs through the quadrangular space, where it touches the surgical neck of the humerus. At that point, it can be easily damaged by surgery, by fractures of the surgical neck of the humerus, or by anterior dislocation of the shoulder. The boundaries of the quadrangular space differ when viewed from the front and from the back. POSTERIOR VIEW. The boundaries of the quadrangular space are: Superiorly: lower border of the teres minor Laterally: the surgical neck of the humerus Medially: the long head of triceps Inferiorly: the upper border of the teres major ANTERIOR VIEW: The boundaries of the quadrangular space are: Superiorly: subscapularis muscle Laterally: the surgical neck of the humerus medially: long head of triceps inferiorly: the upper border of the teres major
The deltoid muscle is responsible for the roundness of the shoulder. It is a multipennate muscle that cloaks the shoulder from the front to the back. Anteriorly, the muscle originates from the anterior border and upper surface of the clavicle. The lateral part of the deltoid muscle consists of oblique fibers arising in a multipennate fashion from tough tendinous bands that originate from the upper surface of the acromiom. Posterior part of the deltoid arises from the lower border of the spine of the scapula.
There are two triangular spaces existing in the inner sleeve of shoulder muscles as viewed from the back. The first triangular space is located just below the quadrangular space. It is bounded superiorly by the lower border of teres major; laterally by the shaft of the humerus; medially by the long head of triceps. This triangular space transmit the radial nerve which is one of the major branches of the posterior cord of the brachial plexus. The second triangular space is medial to the quadrangular space. It is bounded superiorly by the lower border of the teres minor; laterally by the long head of triceps; medially by the upper border of the teres major. This triangular space contains the circumflex scapular vessels, which form part of the extremely rich blood supply to the scapula. In posterior surgical approach to the shoulder, dissection carried out between the teres minor and teres major may damage these vessels, causing profused hemorrhage that is difficult to control.
The axillary nerve disappears beneath the lower border of the subscapularis and, after traversing the quadrangular space, emerges in the back of the shoulder beneath the lower border of the teres minor. The POSTERIOR CIRCUMFLEX vessels run with it. In posterior surgical approach to the shoulder, dissection carried out above the teres minor do not damage the axillary nerve; however, if the dissection strays out of the plane and below the teres minor, the axillary nerve can be damaged. Because the axillary nerve is the sole nerve supply to the deltoid muscle, any damage to it is serious. Within the quadrangular space, the axillary nerve divides into 2 branches after giving off a twig to the shoulder. The deep branch enters and supplies the deep surface of the deltoid muscle. The superficial branch supplies the teres minor and sends a cutaneous branch to the lateral aspect of the upper arm, namely, the UPPER LATERAL CUTANEOUS NERVE of the arm, which supplies the skin over the insertion of the deltoid.
The anterior view of the quadrangular space is shown in this slide. It is bounded superiorly by the lower border of the subscapularis; laterally by the surgical neck of the humerus; medially, the long head of the triceps; inferiorly, the upper border of teres major. In this anterior view, the axillary nerve passes through the lower border of the subscapularis into the quadrangular space and emerges posteriorly. Accompanying the axillary nerve are the posterior circumflex vessels.
The supraspinatus muscle occupies the supraspinous fossa, arising from the medial ¾, and from the supraspinatus fascia. The muscle fibers pass under the acromiom, and converge to a tendon which crosses the upper part of the shoulder joint and is inserted into the highest of the three impressions on the greater tubercle of the humerus; at its insertion the tendon is intimately adherent to the capsule of the shoulder joint. The supraspinatus muscle is supplied by the suprascapular nerve (C4, 5, 6)
The tendon of the supraspinatus is separated from the coracoacromial ligament, acromiom, deltoid by the SUBACROMIAL BURSA. When this bursa is inflamed, abduction of the shoulder joints is very painful. The tendon is the most frequently injured portion of the rotator (or musculotendinous) cuff around the shoulder joint.
The slide shows the supraspinatus muscle and other muscles of the rotator cuff as viewed from the top of the shoulder. It also shows the relationship of the rotator cuff muscles as they approach their insertion at the proximal humerus.
The acromioclavicular articulation is a plane joint between the acromial end of the clavicle and the medial margin of the acromiom of the scapula. The articular surface of the acromial end of the clavicle is covered with fibrocartilage, and forms a narrow , oval area, which is directed downwards and laterally so as to overlap the corresponding area on the medial border of the acromiom. The long axis of the A-C joint lies in an anteroposterior plane. Its ligaments are: 1. Fibrous capsule which completely surrounds the articular margins, and is strengthen above by the acromioclavicular ligament. 2. The acromioclavicular ligament is a quadrilateral band, covering the superior part of the joint, and extending between the upper part of the acromial end of the clavicle and the adjoining part of the upper surface of the acromiom. It is composed of parallel fibers, which interlace with the aponeuroses of the trapezius and Deltoid. 3. An articular disc is usually found in this joint; when present, it occupies the upper part of the articulation, and only partially separates the articular surfaces. More rarely, it divides the joint completely into two cavities. 4. The coracoclavicular ligament connects the clavicle with the coracoid process of the scapula. It does not properly belong to the A-C joint, but is usually described with it since it forms a most efficient means of preventing the clavicle from losing contact with the acromiom. It consists of the TRAPEZOID and the CONOID, which are usually separated by a bursa. This bursa thus intervenes between the medial end of the horizontal part of the coracoid process and the lateral end of the groove for the subclavius muscle on the clavicle. The trapezoid part, which forms the posterior and lateral fasciculus, is broad, thin and quadrilateral. It is attached below to the upper surface of the coracoid process; above, to the trapezoid line on the under surface of the clavicle. The ligaments run almost horizontally. Its anterior border is free; it posterior border is joined with the conoid part, the two forming, by their junction, an angle projecting backwards. The conoid part, which forms the posterior and medial fasciculus, is a dense band of fibers, triangular in form, with its base directed upwards. Its apex is attached to the medial and posterior edge of the root of the coracoid process just infront of the scapular notch; its base is fixed to the conoid tubercle on the under surface of the clavicle, and to a line proceeding medially from it for short distance. The arteries supplying the A-C joint are derived from the scapular and thoracoacromial arteries; the nerves from the suprascapular and thoraco-acromial arteries; the nerves from suprascapular and lateral pectoral nerves.
The deltoid, together with the pectoralis major and latissimus dorsi (the two great muscles of the axillary fold), supplies most of the power required for shoulder movement. The muscles of the inner sleeve can all act as prime movers of the humerus, but their most important action
Anteriorly, two muscular sleeves cover the shoulder joint. The outer muscular sleeve is the deltoid muscle. The inner sleeve consist of one of the rotator cuff muscles, the subscapularis. The rotator cuff muscles are the following: supraspinatus, infraspinatus, teres minor and the subcapularis. The first three are found in the posterior part of the shoulder, while the subscapularis is located anteriorly. Anteriorly, access to the shoulder joint involves reflecting the outer sleeve laterally and incising the outer sleeve which is the subscapularis muscle. However, a third group of muscles intervenes between the two muscular sleeves when the joint is approached from the front. These muscles are short head of biceps, the coracobrachialis, and the pectoralis minor. All are attached to the coracoid process. The tendon of the short head of biceps and the coracobrachialis are often conjoined.
The form and function of the upper extremity can be understood by simulate the primitive position; that is, by abducting the arm until it is horizontal, with the palm facing forward, so that the whole upper extremity approximates the pectoral fin of a fish. The primitively ventral surface generally corresponds to the anterior or flexor side. The primitively dorsal surface generally corresponds to the posterior or extensor side. An imaginary plane drawn from side to side through the long axis of the extremity differentiates between a cephalad preaxial border and a caudal postaxial border. Although there generally is overlap between sequential dermatomes, there is no overlap across the axial borders.
In the course of evolution when the vertebrates started to invade the land and behave like the amphibians and the reptiles, the upper extremities also underwent changes. These adaptations includes flexing the elbow 90 degrees and extending the wrist 90 degrees so that the upper extremities assume the position from fin-like position to one that approximates the amphibian/reptile upper extremity. In mammals and humans, the amphibian/reptile upper extremity has rotated 90 degrees caudally, bringing the upper extremity alongside the lateral body wall with the flexor surface facing anteriorly. The upper extremity is then in the anatomic position.
In humans, there are several adaptations that made the upper extremity a versatile region of the human body. First, upon assuming an upright position the upper extremity is freed from its original functions-that is, support/weight bearing and propulsion, and has developed high intrinsic mobility. The function of the upper human extremity is to place its effector end, the hand, in a position to manipulate the environment. The hand can also be positioned so that it reaches and touches every part of the body. The hand is developed for and is characterized by PREHENSION. Only the human has a sophisticated two-point grasp between the thumb and index finger. Comes with PREHENSION is the development of the hand as a sophisticated sensory organ that can discriminate texture, pain, two-point discrimination, etc. In manipulating the environment, the upper extremity is intrinsically endowed with strength.
The upper extremity has two portions- the free portion which is composed of the arm, forearm, wrist and the hand; the embedded portion which is the pectoral girdle. The free portion of the upper extremity is suspended from the axial skeleton by the embedded portion. The only bony articulation between the pectoral girdle and the axial skeleton is through the clavicle at the sternoclavicular joint. The attachment of the upper extremity to the thorax is primarily muscular. The muscles of the pectoral girdle provide support as well as stability and produce movement. They consist of extensors on the primitively dorsal side and the flexors on the primitively ventral side. The pectoral girdle is mobile at the expense of stability. Strenuous activity that involves extreme lateral rotation may result in dislocation at the glenohumeral joint.
The pectoral girdle consisting of the clavicle and the scapula. The scapula articulates with the clavicle through the acromioclavicular joint. However, the scapulo-clavicular complex articulates with the axial skeleton through the sternoclavicular joint. The shoulder, which includes the pectoral, scapular, and lateral supraclavicular regions and is built on half of the pectoral girdle. The pectoral(shoulder) girdle is a bony ring, incomplete posteriorly, formed by the scapulae and clavicles and completed anteriorly by the manubrium of the sternum.
The upper extremity is attached to the axial skeleton through the pectoral girdle (shoulder). The attachment of the upper extremity to the axial skeleton is primarily muscular and, the pectoral girdle is embedded into these muscles. The muscles that support the upper extremity for stability are also responsible for the extreme mobility of the upper extremity.
The muscles located at the pectoral part of the shoulder are mainly to move the free part of the upper extremity. On the other hand, the pectoral girdle at the back consisting of the scapula is fixed to the posterior part of the upper part of the vertebral column by the extrinsic muscles of the back. The muscles originating from the surfaces of the scapula like the supraspinatus, infraspinatus, teres minor, teres major, subscapularis all function to move the free portion of the upper extremity
The upper extremity is divided into 5 regions and a total of 32 bones including a sesamoid bone composed the each upper extremity. The regions are the ff: 1. Pectoral girdle (or shoulder) consisting of 2 bones, the clavicle and the scapula. 2. The arm or brachium containing 1 bone, the humerus. 3. The forearm or antebrachium contains 2 bones, the radius and the ulna. 4. The wrist or carpus containing 7 carpal bones arranged in 2 rows and a sesamoid bone. 5. The hand containing 5 metacarpals and 14 phalanges.
The clavicle is a superficial bone that can be palpated easily. It is an S-shaped strut interposed between the sternum anteriorly and the scapula posteriorly. It connects the scapula to the sternum through the sternoclavicular joint. It articulates with the scapula at acromioclavicular joint. The clavicle is the first bone to begin to ossify starting at the 5th week of fetal life but it is also the last bone to complete ossification at the age of 21. It is the only long bone formed by intermembranous ossification
The clavicle(collar bone) connects the upper limb to the trunk. Its sternal end articulates with the manubrium of the sternum at the sternoclavicular(SC) joint. Its acromial end articulates with the acromium of the scapula at the acromioclavicular(AC) joint. The medial 2/3 of the shaft of the clavicle are convex anteriorly, whereas the lateral third is flattened and concave anteriorly. These curvatures increase the resilience of the clavicle. Although designated as a long bone, the clavicle has no medullary(marrow) cavity. It consists of spongy(trabecular) bone with a shell of compact bone. The right slide shows the muscular and ligamentous attachments to the clavicle. There 3 muscles that take origin from the clavicle- 1. the anterior part of the deltoid muscle which originates from the anterior lateral third; 2. the pectoralis major at the medial anterior third; 3. the clavicular head of the sternocleidomastoid muscle at the superior medial 1/3. There are two muscles that take insertion at the clavicle- the trapezius at the posterior lateral third; 2. the subclavius muscle occupying the middle third of the inferior border of the clavicle. The ligaments that attach to the clavicle are the coracoclavicular ligaments (the trapezoid and the conoid ligaments) at the lateral third of the inferior border of the clavicle; 2. the costoclavicular ligament located at the medial 1/5 of the inferior border.
The sternoclavicular joint is the articulation of the sternal end of the clavicle with the manubrium of the sternum. This joint is responsible for the articulation of the upper extremity to the axial skeleton through the pectoral girdle. The joint has a fibrocartilaginous articular disk that divides the joint into two synovial capsules. The sternoclavicular joint has a joint capsule that is reinforced by strong ligaments. These ligaments are so strong that dislocation of this joint is uncommon. These ligaments are: 1. The anterior and posterior sternoclavicular ligaments that run between the clavicle and the manubrium. 2. The costoclavicular clavicular ligament that runs between the clavicle and the first rib. 3. Interclavicular ligament that runs from one sternoclavicular joint to the other and traversing the superior part of the manubrium sterni.
The clavicle serves as a strut(rigid support) from which the scapula and free limb as suspended and keeping the limb away from the thorax so that the arm has maximum freedom of motion. Fixing the strut in position, especially after its elevation, enables elevation of the ribs for deep inspiration. The clavicle also forms one of the boundaries of the CERVICOAXILLARY CANAL (passageway between the neck and arm), affording protection to the neurovascular bundle supplying the upper limb. The clavicle also transmits shocks (traumatic impact) or load from the upper extremity to the axial skeleton.
The clavicle is one of the most commonly fractured bone in young individuals. It is the most commonly fractured bone associated with birth(obstetrical fracture). It is often caused by an indirect force transmitted from an outstretched hand through the bones of the forearm and arm to the shoulder during a fall. A fracture may also result from a force applied directly to the clavicle. The weakest part of the clavicle is at the junction of its middle and lateral thirds. After the fracture of the clavicle, the sternocleidomastoid muscle elevates the medial fragment of the bone. The distal fragment is displaced downward due to the pull of the deltoid muscle. The shoulder drops because the trapezius muscle is unable to hold up the lateral fragment owing to the weight of the upper limb. In addition to being depressed, the lateral fragment of the clavicle may be pulled medially by the adductor muscles of the arm such as the pectoralis major. Overriding of the bone fragments shortens the clavicle.
The SCAPULA( shoulder blade) is an inverted triangular bone located at the posterolateral aspect of the thorax, overlying the 2nd to the 7th ribs. The triangular body(blade) of the scapula is thin and translucent superior and inferior to the scapular spine. It has 3 angles: inferior, superior, and lateral angles. It has also 3 borders: the lateral or the axillary border; the superior border; the medial or vertebral border. With the arm resting by the side of the body, the medial or vertebral border runs almost parallel to the spinal column. The lateral or axillary border runs from the inferior angle to the lateral angle of the scapula. The superior border extends from the superior angle laterally toward the coracoid process. It has two surfaces: the concave costal or anterior surface and the convex posterior surface. The anterior surface has a large subscapular fossa is occupied by the subscapularis muscle, while the posterior surface is unevenly divided by the spine of the scapula into a small supraspinous fossa which is occupied by the supraspinatus muscle and the larger infraspinous fossa which houses the infraspinatus muscle.
The spine of the scapula can be palpated as a transverse subcutaneous ridge located at the posterior aspect. It divides the posterior surface in a supraspinous and a infraspinous fossa. The medial end of the spine diminishes in height at the root of the spine. In contrast, the lateral end of the spine gains considerable height and flattens into the broad and prominent acromiom. The acromium process is the lateral expansion of the spine. The acromiom extends in a lateral and anterior direction forming a horizontal shelf over the glenoid fossa. The clavicular facet on the acromiom marks the surface of the acromioclavicular joint. It articulates with the clavicle and provides an attachment for the trapezius and deltoid muscles, as well as for one end of the coracoacromial ligament. The coracoid process (from the word corax, meaning crow’s beak) projects anteriorly, laterally and inferiorly towards the glenoid cavity. It is a remnant of the third bone of the pectoral girdle and is palpable anteriorly just medial to the head of the humerus. It provides attachment to five clinically important structures- the pectoralis minor, coracobrachialis, short head of biceps, coracoacromial ligament, the coracoclavicular ligaments. The GLENOID FOSSA is the site of articulation with the humerus. The articular surface faces laterally but slightly anteriorly and slightly superiorly. This shallow fossa is deepened slightly by the GLENOID LABRUM(lip of fibrocartilage). The supraglenoid tubercle and infraglenoid tubercle provide attachments for the long heads of the biceps and triceps muscles, respectively.
The GLENOID FOSSA(or, glenoid cavity) articulates with the head of the humerus at the glenohumeral (shoulder) joint. It is located at the superolateral portion of the scapula. The glenoid (Greek word: socket) cavity is a shallow, concave, oval fossa, which is directed anterolaterally and slightly superiorly and is considerably smaller than the head of the humerus for which it serves as a socket. The glenoid fossa is slightly deepened by the glenoid labrum (lip of fibrocartilage).
The glenohumeral joint is the articulation between the glenoid fossa of the scapula and the head of the humerus. It is the most mobile of all the joints of the body and gives the upper extremity almost extreme degrees of freedom of movement. It is considered a ball and socket joint although the socket part of the joint is not a true socket into which the humeral head is embedded. Rather, it is a ball and saucer joint since the glenoid fossa is just a shallow depression. Because of this peculiar structure the glenohumeral joint is considered to be one of the most unstable joints that is susceptible to dislocation.
The left slide shows the coronal section of the glenohumeral joint. Take note of the portion of the humeral head that articulates with the shallow glenoid fossa. The shallowness of the glenoid fossa is augmented by the glenoid labrum. Even with the presence of the glenoid labrum the area of the humeral head covered by the glenoid fossa is less than 50%.
The superior, middle and inferior glenohumeral ligaments run from the glenoid lip to the anatomic neck of the humerus. The coracoacromial ligament runs between the coracoid process of the scapula to the humerus. This ligament is short and stubby and acts as a suspension that supports the dead weight of the free portion of the upper extremity.
The coracoacromial ligament runs between the coracoid process and the acromiom process. This ligament together with the acromiom process forms the CORACOACROMIAL ARCH which buttresses the superior aspect of the glenohumeral joint to prevent the superior displacement of the humeral head. The space between the humeral head and the coracoacromial arch is necessary to permit the rotation of the humeral head during full abduction. This space is occupied by the SUBACROMIAL BURSA. The coracoacromial ligament transmit tensile force from the muscles that originate from the coracoid process to the acromial process and spine of the scapula. These muscles are the short head of the biceps muscle and the pectoralis minor muscle.
The glenohumeral joint per se is inherently unstable joint that is reinforced by the ligaments and the musculotendinous cuff of the muscles attaching to the anatomic neck and the greater and lesser tuberosities of the humerus. The ligamentous structures provide immediate but static stability while the musculotendinous cuff provide joint stability by the muscle action acting on the shoulder joint. The Rotator (musculostendinous) Cuff composed on the Supraspinatus, Infraspinatus, Subscapularis and Teres Minor muscles act as a dynamic “ligament”, keeping the humeral head pressed into the glenoid fossa.
The long head of the biceps brachii muscle, passing over the humeral head en route to the supraglenoid tubercle of the scapula, also give dynamic stability to the glenohumeral joint by keeping the humeral head medially into the glenoid fossa.
The stability of the glenohumeral joint is provided by the ligaments and the muscles. The ligaments provide static stability-that is, stability due to the inherent strength of the ligaments. Since a bundle of ligaments do not contract and relax, its strength reside by its length and size. The longer the ligament bundle, the more mobile is the structure that the ligament bundle is stabilizing. The shorter the ligament bundle the lesser is the motion allowed. The muscles provide dynamic stability by virtue of their action. The rotator cuff for example is a structure to which contribute the following muscles: Subscapularis, Supraspinatus, Infraspinatus and the Teres minor.
One of the most common traumatic conditions of the shoulder seen in the emergency room and in PT clinic is acute shoulder dislocation. It may occur once in a patient but the most common is the recurrent type. The patient is usually young with age ranging from 15 years to 25 years. In acute shoulder dislocation the normal relationship of the humeral with the glenoid fossa is lost. The head is out of the glenoid fossa. Despite the musculotendinous cuff and other stabilizing structures, the shallowness of the glenoid fossa and the extreme mobility of the glenohumeral joint predispose the shoulder to dislocation. The humeral head may be displaced anterior to the glenoid fossa or posterior to it. The most common form of shoulder dislocation is the anterior type wherein the humeral head comes to lie inferior to the coracoid process. The axillary nerve is sometimes injured. Dislocation stretches the anterior part of the capsule and may avulse the glenoid labrum, which increases the likelihood of recurrence. Posterior shoulder dislocation is rare and the humeral head is displaced posterior to the glenoid fossa. Since the humeral head is displaced away from the brachial plexus the incidence of neurovascular injury is low
In the normal axillary view of the shoulder, the relationship of the humeral head to the glenoid fossa is also shown. The humeral head is seated on the glenoid fossa like a golf ball seated on a golf tee. The Coracoid process together with the clavicular shaft- 2 structures located anterior to the glenoid fossa are clearly delineated. The spine of the scapular which is located posterior to the glenoid fossa is also clearly shown. The rounded soft tissue contour overlying the glenohumeral joint is very clearly projected.
The left slide shows the normal antero-posterior projection of the shoulder. It shows the following structures: 1. the glenohumeral joint with the humeral head seated on the glenoid fossa. 2. The distal ¾ of the clavicle articulating with the acromial process of the scapula at the acromioclavicular joint. 3. The scapula 4. Part of the thoracic cage. 5. Rounded soft tissue contour overlying the humeral head. 6. The space between the superior part of the humeral head and the inferior surface of the acromiom process of the scapula. This projection does not usually show clearly the coracoid process and the scapular spine. At the right slide is an AP projection of a dislocated shoulder. Take note of the following: 1. The relationship of the humeral head with the glenoid fossa is lost. Note that the medial aspect of the humeral head is displaced inferiorly and medial to the glenoid fossa. 2. The space between the inferior surface of the acromiom process of the scapula and the superior part of the humeral head is very wide and increased several times compared to the normal. 3. The rounded soft tissue contour overlying the humeral head is lost and becomes flattened.
The ACROMIOCLAVICULAR joint is the articulation of the distal end of the clavicle with the acromial process of the scapula.
Bursae are fluid-filled cavities interposed between bone and muscle, between muscle tendon and bone, between bone and ligament. The purpose is to reduce friction and promotes smooth motion. In the shoulder, there are two major bursae- the subacromial bursa and the subdeltoid bursa. The subacromial bursa separates the acromiom process from the underlying supraspinatus muscle. The subdeltoid bursa is interposed between the deltoid muscle from the humeral head and the insertion of the rotator cuff.
Shoulder pain is one of the most common complaints that bring a patient to a physician. It could be due to trauma, inflammatory conditions, infection, etc. The most common is an inflammatory condition involving the subacromial bursa or the musculotendinous cuff surrounding the shoulder joint. Subacromial bursitis is common among persons engaged in repetitive activities like lifting, gardening, farm workers engaged in long manual activities like weeding. Or it could be a part of medical problems like diabetes. Same is true with tendonitis involving the rotator musculotendinous cuffs.
The superficial layer of muscle at supporting the shoulder girdle at the back is the trapezius which is a large muscle occupying the proximal half of the back. It is a diamond-shaped flat muscle the upper end of it point to its origin at the superior nuchal line, ligamentum nuchae, and spine of 7th cervical vertebra. The other end points to the origin of the lower portion which are the spines of the 1st thoracic to the 12th thoracic vertebrae. The 2 side corners of the diamond point to its insertion to the left and right lateral third of the clavicle and the acromiom process and the spine of the scapula. The Trapezius muscle is divided into two parts- the upper and lower portions based on its origin, insertion and action on the shoulder girdle. The upper portion has its origin at the superior nuchal line, ligamentum nuchae, and the spinous process of 7th cervical vertebra. It has its insertion at the lateral third of the clavicle and at the acromiom process of the scapula. The upper portion of the trapezius acts on the scapula by elevating and rotating it upward during elevation of the arm The lower part of the trapezius originates from the spinous processes of the 1st thoracic to the 12th thoracic vertebrae. It is has its insertion at the spine of the scapula. Its action is opposite that of the upper portion since the lower part depresses and rotates the scapula downward. The trapezius is mainly innervated by Cranial Nerve 11- the Spinal Accessory. Its upper portion also receives innervation from the spinal nerves C3-C4, while the lower part receives innervation from the lower cervical nerves. The deeper layer of posterior muscle groups acting on the shoulder girdle are composed of the Levator Scapulae, the Rhomboids(major and minor). These muscles can be seen during cadaver dissection by taking out the trapezius muscle. The Levator scapulae occupies the more superior part then followed by the rhomboid minor; the rhomboid major occupies the distal part. The Levator scapulae muscle has its origin from the transverse processes of the cervical vertebrae C1-C4 and is inserted to the superior portion of the vertebral border of the scapula. It is innervated by a nerve to the levator scapula. The nerve fibers come from the spinal nerves of C3-C4. The Levator Scapula muscle is one of the elevators of the scapula. The Rhomboid Minor muscle has its origin from the lower part of the ligamentum nuchae and from the spines of C7-T1 vertebrae and is inserted at the proximal portion of the spine of the scapula. It is innervated by the Dorsal Scapular nerve. It acts as retractor and elevator of the scapula. The Rhomboid Major muscle has its origin from the spinous processes of T2-T5 vertebrae and is inserted to the vertebral border of the scapula inferior to the spine. It is also innervated by the Dorsal Scapular Nerve. It retracts and elevates the scapula.
The trapezius muscle fibers are divided into parts that have different actions at the scapulothoracic joint between the scapular and the thoracic. The descending (superior) and ascending (inferior) parts of trapezius act together in rotating the scapula on the thoracic wall. The trapezius also braces the shoulder by pulling the scapulae posteriorly and superiorly, fixing them in position with tonic contraction; consequently weakness of this muscle causes drooping of the shoulder.
The anterior muscles acting on the shoulder girdle are also arranged into superficial and deep layers. The superficial layer of muscles are composed of the Pectoralis minor muscle and the sternocleidomastoid muscle. The deep layer are the Serratus anterior and the Subclavius muscles.
The long name of sternocleidomastoid muscle indicates its origin and insertion. The “cleido” part of its name is derived from the Greek word “kleis” meaning clavicle. The sternocleidomastoid muscle is a long robust muscle that is the key muscular landmark in the neck. Running obliquely upward from the sternum and the clavicle to the lateral surface of the mastoid process, it divides the side of the neck into anterior and posterior triangles for purposes of description. Hence, swellings and other lesions in the neck can be described with reference to these cervical triangles. To make your sternocleidomastoid stand out, put your chin upward and to one side. Palpate the anterior border of the rounded band of muscle on the other side. Origin: the sternocleidomastoid muscle has to heads- the sternal head originates from the anterior surface of the manubrium sterni; the clavicular head from the upper surface of the medial third of the clavicle. Insertion: mastoid process of the temporal bone and the lateral half of the superior nuchal line of the occipital bone. Innervation: from the Spinal accessory (CN XI) and from the ventral (anterior) ramus of the second cervical spinal nerve directly. Actions: Elevates the sternum and clavicle; rotates the head. Acting alone, it tilts the head to its own side (laterally bends) and rotates it so the face is turned upward toward the opposite side. Acting together they flex the neck (e.g. when raising the head from a pillow against gravity).
This large, thin, foliate, powerful muscle overlies the lateral portion of the thorax and the intercostal muscles. It was given its name (L. serratus, a saw) because of the saw-toothed appearance of the fleshy digitations at its origin. Origin: Outer surfaces of first eight ribs, about midway between their angles and costal cartilages. Its lower 3 digitations interdigitate with the origin of the external oblique muscle of the abdomen. Insertion: Entire anterior surface of the medial border of the scapula. Innervation: Long thoracic nerve (C5-C7). Actions: it protracts (abducts) scapula and holds it against chest wall. Because it acts when pushing or punching, it is often called “the boxer’s muscle.” By fixing the scapula to the chest, it acts as an anchor for this bone allowing other muscles to use it as a fixed bone for producing movements of the humerus. Its lower fibers help to rotate glenoid cavity of the scapula upward (e.g. when arm is raised above the head.
The Pectoralis minor muscle is a flat, triangular muscle that lies in the anterior wall of the axilla, deep to the much larger pectoralis major. The pectoralis minor is a landmark of the axilla. Together with the Subclavius muscle, it is surrounded by the CLAVIPECTORAL FASCIA which is a thin sheet of fibrous tissue that runs from the clavicle to the floor of the axilla. This connection of the clavipectoral fascia with the clavicle supports and suspends the floor of the axilla which is composed of the axillary fascia and the skin. Origin: Upper margins and outer surfaces of ribs 3,4, and 5 and fascia of associated intercostal spaces. Insertion: Medial border of coracoid process of scapula. Innervation: from the medial pectoral nerve. Actions: Stabilizes the scapula by drawing it forward and downward. The chief importance of this muscle is that it is a useful landmark for many structures in the axilla because, with the coracoid process, it forms an arch deep to which pass the vessels and nerves to the arm.
The Subclavius muscle, as its name indicates, lies below the clavicle. It is a small and relatively unimportant muscle. However, because of its location it may serve as a protective cushion between the fractured clavicle and the subclavian vessels.
The SCAPULOTHORACIC JOINT is actually not a true joint since no bony articulation exists between the scapula and the thoracic cage. It is a conceptualized pseudojoint, which lies between the Subscapularis muscle and the Serratus Anterior muscle, and appears to function as a joint, although its movement pairs actually occur at the sternoclavicular and the acromioclavicular joints. This “joint” has 3 degrees of freedom which allow for considerable motion of the scapula on the posterolateral thoracic cage. These movements are: 1. Protraction/Retraction- motion occurs through a vertical axis at the sternoclavicular joint so that the scapula slides anterolaterally / posteromedially on the thoracic cage. 2. Elevation/ depression- this motion occurs through an anterior-posterior axis at the sternoclavicular joint so that the scapula slides cranially/ caudally on the posterior thoracic wall. 3. Rotation- this motion occurs through an anterior-posterior axis at the acromioclavicular joint so that the scapula rotates on the posterior thoracic wall. This pseudojoint is supported by the clavicle and reinforced dynamically by the muscles that insert on the scapula from the axial skeleton, such as the rhomboids, serratus anterior, trapezius, and levator scapula.
The HUMERUS (arm bone), the largest bone in the upper limb, articulates proximally with the scapula at the glenohumeral joint(or, SCAPULOHUMERAL JOINT) and the radius and ulna distally at the elbow joint. Proximally, the ball-shaped humeral head which is covered with hyaline cartilage articulates with the glenoid cavity of the scapula. The INTERTUBERCULAR GROOVE (bicepital groove) of the proximal end of the humerus separates the lesser tubercle from the greater tubercle. It contains the tendon of the long head of biceps brachii muscle. It is bridged by the TRANSVERSE HUMERAL LIGAMENT. The lateral lip of the groove provides muscular attachment for the pectoralis major muscle; the floor for the latissimus dorsi muscle, the medial lip for the teres major muscle. The LESSER TUBEROSITY lies on the anterior surface of the humerus, just distal to the anatomic neck, and provides attachment for the SUBSCAPULARIS MUSCLE. The GREATER TUBEROSITY lies on the lateral surface of the humerus, just distal to the anatomic neck, and provides attachments for the SUPRASPINATUS, INFRASPINATUS, and TERES MINOR muscles. The ANATOMIC NECK separates the humeral head from the proximal metaphysis where the tubercles(GREATER AND LESSER TUBEROSITY) are located. The anatomic neck marks the location of an epiphyseal plate that normally fuses between the 19th and 21st years. The shaft(body) of the humerus has two prominent features: the DELTOID TUBEROSITY laterally and the RADIAL GROOVE ( groove for the radial nerve, spiral f groove) posteriorly for the RADIAL NERVE and DEEP artery of the arm. The inferior end of the shaft widens as the sharp medial and lateral supraepicondylar(supracondylar) ridges form and then end distally in the prominent medial and lateral epicondyle. The distal end of the humerus involved in forming the elbow joint consist of the TROCHLEA, CAPITULUM, OLECRANON, CORONOID and RADIAL FOSSA. This distal end is collectively called the CONDYLE of the HUMERUS.
The distal end of the humerus which forms an articulation with the proximal radius and ulna consists of the trochlea, capitulum, olecranon, the coronoid and radial fossae. These parts are collectively known as the humeral condyle. It has two articular surfaces: a lateral CAPITULUM (L. Latin- means little head) for articulation of with the head of the radius and the medial TROCHLEA( L. pulley) for the articulation with the trochlear notch of the ulna. Superior to the trochlea anteriorly is CORONOID FOSSA which receives the coronoid process of the ulna during full flexion of the elbow. Posteriorly, the OLECRANON FOSSA accomodates the olecranon of the ulna during extension of the elbow. Superior to the capitulum anteriorly, the shallow radial fossa accomodates the edge of the radial head when the elbow is fully flexed.
The humerus is a frequent site of traumatic affliction. Most common of these conditions is the frequent occurrence of fracture. Fracture of the surgical neck in young people requires a considerable force. Among the elderly, however, only a minimal force is required to fracture this part of the humerus due to OSTEOPOROSIS. Fracture involving the middle third of the humerus maybe associated with injury to the radial nerve where it passes through the radial groove. Any fracture of the middle third of the humerus should alert a treating physician the possibility of radial nerve injury. One should look for the familiar sign of radial nerve injury- the WRIST DROP POSITION of the hand. This sign is due to the paralysis of the wrist and common digital extensors with intact wrist and finger flexors. The patient can flex his fingers and wrist but unable to extent actively his wrist and his fingers. In young children, fracture of the distal part of the humerus(supracondylar fracture) may be associated with neurovascular injury and the occurrence of compartment syndrome.
The acromioclavicular joint is the articulation between the distal lateral end of the clavicle with the acromial process of the scapula. The placement of this joint in the shoulder girdle contributes to the hypermobility of the upper extremity at the shoulder region and increases the efficiency of the shoulder motion. Motion at the shoulder without involving the free part of the upper extremity is effectively carried out at the A-C joint. In other word, the A-C joint isolate the movement of the shoulder when motion at the glenohumeral joint is not needed. This joint is a sliding articulation with two degrees of freedom. Rotation of the scapula occurs primarily at this joint about and anterior-posterior axis. Other motions at this joint are mainly accommodations to motions that occur at the sternoclavicular joint. The A-C joint has a joint capsule that is reinforced by the following ligaments: 1. the CORACOCLAVICULAR LIGAMENT runs from the coracoid process of the scapula to the clavicle. It is subdivided into a CONOID LIGAMENT and a TRAPEZOID ligament, both of which provide superior-inferior stability, that is, these two ligaments prevent excessive displacement of the clavicle and the acromium upward or downward. 2. The ACROMIOCLAVICULAR ligament bridges the joint and provides anterior-posterior stability.
The elbow joint function is intimately associated with the function of the forearm and, as such, it is called the elbow and forearm complex. It consists of 3 bones and 4 joints. The HUMEROULNAR AND HUMERORADIAL joints form the elbow. The radius and ulna articulate with one another within the forearm at the proximal and distal RADIOULNAR joints. This set of articulations (i.e., the proximal and distal radioulnar joints) allows the palm of the hand to be turned up (supinated) or down (pronated), without requiring motion of the shoulder. Pronation and supination can be performed in conjunction with, or independent from, elbow flexion and extension. The interaction between the elbow and forearm joints greatly increases the range of effective hand placement.
The HUMEROULNAR AND HUMERORADIAL JOINTS form the elbow. The tight fit between the trochlea and the trochlear notch at the humeroulnar joint provides most of the elbow’s structural stability. Early anatomists classified the elbow as GINGLYMUS or HINGED joint owing to its predominant uniplanar motion of flexion and extension. The term MODIFIED HINGE JOINT is actually more appropriate since the ulna experiences slight amount of axial rotation (i.e., rotation about its own longitudinal axis) and side-to-side motion as it flexes and extends. These minor motions of the ulna are called “extra-sagittal” accessory motions. The humeroradial joint is the articulation with the concave superior surface of the radial head known as FOVEA with the capitulum of the humerus. The radial head is a disclike structure located at the extreme proximal end of the radius. Most of the outer rim is covered with articular cartilage and articulates with the radial notch of the ulna forming the proximal radioulnar joint. Just a little distal to the radial head at the antero-medial edge of the proximal radius, a roughened region known as the bicepital tuberosity. This is the site of insertion of the biceps brachii muscle. The motions of flexion and extension of the elbow provide a means to adjust the overall functional length of the upper limb. This function is used for many important activities, such as feeding, reaching, and throwing, and personal hygiene.
Elbow flexion and extension occur about a medial-lateral axis of rotation, passing through the vicinity of the lateral epicondyle. From medial to lateral, the axis courses slightly superiorly owing in part to the distal elongation of the medial lip of the trochlea. The asymmetry in the trochlea causes the ulna to deviate laterally relative to the humerus. The natural frontal plane angle made by the extended elbow is referred to as CUBITUS VALGUS. The term “carrying angle” is often used, reflecting the fact that the valgus angle tends to keep carried objects away from the sides of the thigh while walking. In full elbow extension , the normal carrying angle is about 15 to 18 degrees.
The anterior surfaces of the mid-to-distal humerus provide proximal attachments for the brachialis and, at the posterior surface, the medial head of the triceps brachii. The distal end of the shaft of the humerus terminates medially as the TROCHLEA and the MEDIAL EPICONDYLE, and laterally as the CAPITULUM and LATERAL EPICONDYLE. The trochlea resembles a rounded, empty spool of thread. On either side of the trochlea are its medial and lateral lip. The medial lip is prominent and extends farther distally than the adjacent lateral lip. Midway between the medial and the lateral lips is the TROCHLEAR GROOVE which, when looking from posterior to anterior, spirals slightly toward the medial direction. The CORONOID FOSSA is located just proximal to the anterior side of the trochlea. Directly lateral to the trochlea is the rounded CAPITULUM which forms nearly one half of a sphere. A small RADIAL FOSSA is located just proximal to the anterior side of the capitulum. The MEDIAL EPICONDYLE of the humerus projects medially from the trochlea. This prominent and easily palpable structure serves as the proximal attachment of the MEDIAL COLLATERAL LIGAMENT of the elbow as well as the FOREARM PRONATOR and WRIST FLEXOR muscles. The LATERAL EPICONDYLE of the humerus, less prominent than the medial epicondyle, serves as the proximal attachment for the LATERAL COLLATERAL LIGAMENT of the elbow as well as the FOREARM SUPINATOR and WRIST EXTENSOR MUSCLES. Immediately proximal to both epicondyles are the MEDIAL AND LATERAL SUPRACONDYLAR RIDGES. On the posterior side of the humerus, just proximal to the trochlea, is the very deep and broad OLECRANON FOSSA. Only a thin sheet of bone or membrane separates the olecranon from the coronoid fossa.
The ulna has a thick proximal end with distinct processes. The OLECRANON PROCESS forms the blunt, proximal tip of the ulna, making up the “POINT” of the elbow. The roughened posterior surface of the olecranon process accepts the attachment of the TRICEPS BRACHII. The CORONOID PROCESS projects sharply from the anterior body of the proximal ulna. The TROCHLEAR NOTCH of the ulna is the large jawlike process located between the anterior tips of the olecranon and coronoid processes. This concave notch articulates firmly with the reciprocally shaped trochlea of the humerus, forming the HUMEROULNAR JOINT. A thin raised LONGITUDINAL CREST divides the trochlear notch down its midline. The RADIAL NOTCH of the ulna is an articular depression just lateral to the inferior aspect of the trochlear notch. Extending distally, and slightly dorsally, from the radial notch is the SUPINATOR CREST, marking the distal attachments for part of the lateral collateral ligament and the supinator muscle. The TUBEROSITY OF THE ULNA is a roughened impression just distal to the coronoid process, formed by the attachment of the BRACHIALIS MUSCLE. The ULNAR HEAD is located at the distal end of the ulna. Most of the rounded ulnar head is lined with articular cartilage. The pointed STYLOID (from the Greek root stylos, pillar, + eidos; resembling) process projects distally from the posterior-medial region of the extreme distal ulna.
The above illustration is the front view of the articular surface of the trochlear notch of the ulna. This notch articulates firmly with the trochlea of the humerus forming the humeroulnar joint. At the middle of the articular surface is a raised longitudinal crest that divides the trochlear notch in its midline. This part of the trochlear notch fits into the trochlear groove of the trochlea of the distal humerus. Laterally is the radial head which articulates with the radial notch of the ulna to form the proximal radioulnar joint. This proximal radioulnar joint is maintained and stabilized by the ANNULAR LIGAMENT. The superior surface of the radial head consists of a shallow, cup-shaped depression known as the FOVEA. This cartilage-lined concavity articulates with the capitulum of the humerus, forming the humeroradial joint.
In the fully supinated position, the radius lies parallel and lateral to the ulna. The proximal end of the radius is small and as such constitutes a relatively small structural component of the elbow. Its distal end, however, is enlarged, forming a major part of the wrist joint. The RADIAL HEAD is a disclike structure located at the extreme proximal end of the radius. Most of the outer rim of the radial head is covered with a layer of articular cartilage. The rim of the radial head contacts the RADIAL NOTCH of the ulna, forming the PROXIMAL RADIOULNAR JOINT. The superior surface of the radial head consists of a shallow, cup-shaped depression known as the FOVEA. This cartilage-lined concavity articulates with the CAPITULUM of the humerus forming the HUMERORADIAL JOINT. The biceps brachii muscle attaches to the radius at the BICIPITAL TUBEROSITY, a roughened region located at the antero-medial edge of the proximal radius. The distal end of the radius articulates with the carpal bones to form the RADIOCARPAL JOINT at the wrist. The ULNAR NOTCH of the distal radius accepts the ULNAR HEAD at the DISTAL RADIOULNAR JOINT. The prominent STYLOID PROCESS projects from the lateral surface of the distal radius.
Above slide is schematic representation of the anterior view of the distal radioulnar joint in which the ulnar head has been pulled off from the concavity form by the proximal surface of the articular disc and the ulnar notch of the radius. Note that lateral end of the bone is extended into a structure known as the RADIAL STYLOID. The distal portion of the radial bone is enlarged. It is articular surface is concave and has several articulating facets to accommodate the carpals of the wrist.
The articular capsule of the elbow encloses 3 different articulations: the humeroulnar joint, the humeroradial joint and the proximal radioulnar joint. The capsule is thin and reinforced anteriorly by oblique bands of fibrous tissue. The elbow, being a synovial (diarthrodial) joint, a synovial membrane lines the internal surface of the capsule.
The articular capsule of the elbow is strengthened by an extensive set of collateral ligaments which provide an important source of stability to the elbow joint. 1. Medial collateral ligament consists of anterior, posterior and transverse fiber bundles. The anterior fibers are the strongest and the stiffest of the medial collateral ligament. As such, these fibers provide the most significant resistance against a valgus(abduction) force at the elbow joint. The anterior fibers arise from the anterior part of the medial epicondyle and insert on the medial part of the coronoid process of the ulna. The majority of the anterior fibers, however, become taut at full extension. A few fibers, however, become taut at full flexion. The anterior fiber bundle, as a whole, therefore, provides articular stability throughout the entire range of motion. The posterior fibers of the medial collateral ligament attach on the posterior part of the medial epicondyle and insert on the medial margin of the olecranon process. The posterior fibers become taut in the extremes of elbow flexion. A third and poorly developed set of transverse fibers of the medial collateral ligament cross from the olecranon to the coronoid process of the ulna. Because these fibers originate and insert on the same bone, they do not provide significant articular stability.
The lateral collateral ligament of the elbow is less defined and more variable in form that the medial collateral ligament. The ligament originates on the lateral epicondyle and immediately splits into two fiber bundles. One fiber bundle, traditionally known as the RADIAL COLLATERAL LIGAMENT, fans out to blend with the ANNULAR LIGAMENT. A second fiber bundle, called the lateral (ulnar) collateral ligament, attaches distally to the supinator crest of the ulna. These fibers become taut at full flexion. All the fibers of the lateral collateral ligament and the posterolateral aspect of the capsule stabilize the elbow against a varus-directed force. By attaching to the ulna, the lateral(ulnar) collateral ligament and the anterior fibers of the medial collateral ligament function as collateral “Guy Wires” to the elbow, stabilizing the path of the ulna during sagittal plane motion. The ligaments around the elbow are endowed with mechanoreceptors, consisting of GOLGI organs, RUFFINI terminals, PACINIAN corpuscles, and free nerve endings. These receptors may supply important information to the nervous system for augmenting proprioception and detecting safe limits of passive tension in the structures around the elbow joint.
Attempts at catching oneself from a fall may induce a severe valgus force, overstretching or rupturing the medial collateral ligament. Injury to the collateral ligaments of the elbow can result in marked elbow instability. The medial collateral ligament is susceptible to injury when fully extended elbow receives a violent valgus force, often from a fall. The anterior capsule may be involved with the valgus injury if the joint is also forced into hyperextension. The medial collateral ligament is also susceptible to injury from repetitive valgus forces in non-weight-bearing activities, such as pitching a baseball and spiking a volleyball.
Elbow flexion and extension is very important in the activities of daily living. Elbow flexion provides several important physiologic functions, such as pulling, lifting, feeding and grooming. The inability to actively bring the hand to the mouth for feeding, for example, significantly limits the level of functional independence. Persons with spinal cord injury above the C5 nerve root have this profound disability due to total paralysis of elbow flexor muscles. Elbow extension occurs with activities such as throwing, pushing, and reaching. Loss of complete extension due to an elbow flexion contracture is often caused by marked stiffness in the elbow flexor muscles. The muscles become abnormally stiff after long periods of immobilization in a flexed and shortened position. Long-term flexion may be the result of casting following a fractured bone, an elbow joint inflammation, an elbow flexor spasticity, a paralysis of the triceps muscle, or a scarring of the skin over the anterior elbow. In addition to the tightness in the flexor muscles, increased stiffness may occur in the anterior capsule and anterior parts of the collateral ligaments. The maximal range of passive motion generally available to the elbow is from 5 degrees of hyperextension through 145 degrees of flexion. Research indicates, however, that several common activities of daily living use only a limited arc of motion, usually between 30 degrees and 130 degrees of flexion. The loss of the extremes of motion of the elbow usually results in only minimal functional impairment.
The above slide shows the relationship between the degree of elbow flexion contracture and the loss of forward reach. One of the most disabling consequences of an elbow flexion contracture is reduced reaching capacity. The loss of forward reach varies with the degree of elbow flexion contracture. A fully extendable elbow (i.e., with a 0-degree contracture) demonstrates a 0-degree loss in area of forward reach. The area of forward reach diminishes only slightly (less than 6%) with a flexion contracture of less than 30 degrees. A flexion contracture that exceeds 30 degrees, however, results in a much greater loss of forward reach. As noted in the graph, flexion contracture of 90 degrees reduces total reach by almost 50%. Minimizing flexion contracture to less than 30 degrees is therefore an important functional goal for patients following trauma, prolonged immobilization, or joint replacement.
The above slide shows the functional range of motion at the elbow. A typically healthy elbow showing the extent of range of motion from 5 degrees beyond extension (hyperextension) through 145 degrees of flexion. The 100-degree “functional arc” from 30 degrees to 130 degrees of flexion in red based on the histogram. The histogram shows the range of motion at the elbow typically needed to perform the following activities of daily living: opening a door, pouring from a pitcher, rising from the chair, holding a newspaper, cutting with a knife, bringing a fork to the mouth, bringing a glass to the mouth.
The humeroulnar joint is the articulation of the concave trochlear notch of the ulna around the convex trochlea of the humerus. From a sagittal section, the humeroulnar joint resembles a ball-and-socket joint. The firm mechanical link between the trochlea and trochlear notch, however, limits the motion to essentially the sagittal plane(that is, to predominantly flexion-extension). Hyaline cartilage covers about 300 degrees of articular surface on the trochlea compared with only 180 degrees on the trochlear notch.
The above slide shows the mechanics of elbow extension and flexion. In order for the humeroulnar joint to be fully, passively extended, sufficient extensibility is required in the dermis, flexor muscles, anterior capsule, and the anterior fibers of the medial collateral ligament. Once in full extension, the humeroulnar joint is stabilized by the increased tension in the following structures: 1. most of the anterior fibers of the medial collateral ligament 2. anterior capsule 3. flexor muscles particularly the broad tendon of the brachialis 4. the prominent tip of the olecranon process becomes wedged into the olecranon fossa During flexion at the humeroulnar joint, the concave surface of the trochlear notch roles and slides on the convex trochlea. Full passive elbow flexion requires elongation of the posterior, extensor muscles, ulnar nerve, and certain collateral ligaments, especially the posterior fibers of the medial collateral ligament.
The humeroradial joint is an articulation between the cuplike fovea of the radial head and the reciprocally shaped rounded capitulum. At rest in full extension, little if any physical contact exists at the humeroradial joint. During active flexion, however, muscle contraction pulls the radial fovea against the capitulum. The motion of flexion and extension consist of the fovea of the radius rolling and sliding across the convexity of the capitulum Compared with the humeroulnar joint, the humeroradial joint provides minimal structural stability of the elbow. The humeroradial joint does, however, provide an important bony resistance against a valgus force.
The radius and ulna are bound together by the interosseous membrane and the proximal and distal radioulnar joints. This set of joints, situated at either end of the forearm allows the forearm to rotate into pronation and supination. Forearm supination places the palm up, or supine, and pronation places the palm down, or prone. This forearm rotation occurs about an axis of rotation that extends from the radial head through the head of the ulna-an axis that intersects and connects both radioulnar joints.
The above slide illustrates supination and pronation movement of the forearm. In full supination (A) the radius and ulna are parallel to each other. Moving in full pronation(B) the radius crossing over the ulna. The axis of rotation (illustrated by a dashed line) extends obliquely across the forearm from the radial head to the ulnar head. The radius and hand (shown in red) is the distal segment of the forearm complex. The humerus and ulna (shown in gray) is the proximal segment of the forearm complex. Note that the thumb stays with the radius during pronation. It is apparent that pronation and supination provide a mechanism that allows independent “rotation” of the hand without an obligatory rotation of the ulna or humerus. A person with limited pronation or supination range of motion must rely on greater internal or external rotation of the shoulder to perform activities such as tightening a screw and turning a doorknob. The movements of pronation and supination is actually more complicated than the concept of “palm up and palm down”. The palm does indeed rotate, but only because the hand and wrist connect to the radius and not to the ulna. The space between the distal ulna and the medial side of the carpus allows the carpal bones to rotate freely-along with the radius-without interference from the distal ulna. In the anatomic position, the forearm is fully supinated when the ulna and radius lie parallel to one another. During pronation, the distal segment of the forearm complex (that is, the radius and hand) rotates and crosses over an essentially fixed ulna. The ulna, through its firm attachment to the humerus at the humeroulnar joint, remains essentially stationary during pronation and supination movements. A stable ulna provides an important link that the radius, wrist and hand can pivot upon.
The distal radioulnar joint consists of the convex head of the ulna fitting into a shallow concavity formed by the ulnar notch on the radius and the proximal surface of an articular disc. This important joint stabilizes the distal forearm during pronation and supination. The articular disc at the distal radioulnar joint is also known as the triangular fibrocartilage, indicating its shape and predominant tissue type. The lateral side of the disc attaches along the entire rim of the ulnar notch of the radius. The main body of the disc fans out horizontally into a triangular shape, with its apex attaching medially into the depression on the head of the ulna and adjacent styloid process. The anterior and posterior edges of the disc are continuous with the palmar(anterior) and dorsal (posterior) radioulnar joint capsular ligaments. The proximal surface of the disc, along with the attached capsular ligaments, holds the head of the ulna snugly against the ulnar notch of the radius.
The proximal radioulnar joint, the humeroulnar joint, and the humeroradial joint all share one articular capsule. Within this capsule, the radial head is held against the proximal ulna by a fibro-osseous ring. This ring is formed by the radial notch of the ulna and the annular ligament. About 75% of the ring is formed by the annular ligament and 25% by the radial notch of the ulna. The annular (from the Latin annulus; ring) ligament is a thick circular band of connective tissue, attaching on either side of the radial notch. The ligament fits snugly around the radial head, holding the proximal radius against the ulna. The internal circumference of the annular ligament is lined with cartilage to reduce the friction against the radial head during pronation and supination. The external surface of the annular ligament receives attachment from the elbow capsule, the radial collateral ligament, and the supinator muscles. The quadrate ligament is a short, stout ligament that arises below the radial notch of the ulna and attaches to the medial surface of the neck of the radius. This ligament gives structural support to the capsule of the proximal radioulnar joint.
Of the four arm muscles, three flexors (biceps brachii, brachialis, coracobrachialis) are in the anterior(flexor) compartment and are supplied by the musculocutaneous nerve, and one extensor(triceps brachii) is in the posterior (extensor) compartment, supplied by the radial nerve. A small triangular muscle in the posterior aspect of the elbow, the ANCONEUS, covers the posterior aspect of the ulna posteriorly. The biceps brachii has two heads, a long head and a short head. The long head has it proximal attachment at the supraglenoid tubercle of the scapula; the short head at the tip of the coracoid process of the scapula. Distally, it attaches at the bicipital tuberosity on the radius. Secondary distal attachments are made into the deep fascia of the forearm through an aponeurotic sheet known as the FIBROUS LACERTUS. The fibrous lacertus is also called the bicipital aponeurosis. This triangular membranous band runs from the bicep tendon across the cubital fossa and merges with the antebrachial (deep)fascia covering the flexor muscles in the medial side of the forearm. The biceps brachii acts strongly when performing both flexion and supination simultaneously. It is weak when flexion is done with the forearm in pronation.
The brachialis muscle lies deep (posterior) to the biceps brachii, originating on the distal one half of the anterior surface of the humerus and insert to the coronoid process and tuberosity of the ulna. The brachialis is considered as a pure flexor muscle and flexes the elbow with the forearm in all positions and during slow and quick movements. When the forearm is extended slowly the brachialis steadies the movement by slowly relaxing. The brachialis is strongest flexor of the elbow and the forearm being the largest muscle crossing the elbow joint. It is called the “the work-horse” of the elbow flexors due to, in part, its large work capacity, but also to its active involvement in all types of elbow flexion activities, whether performed fast or slow, or combined with supination or pronation. Since its distal attachment is to the proximal part of the ulna, the motion of pronation or supination has no influence on its length, line-of-force, or internal moment arm.
The brachioradialis is the longest of all the elbow muscles. It proximal attachment is on the lateral supracondylar ridge of the humerus; its distal attachment is near the styloid process of the radius. Due to its length, maximal shortening of the brachioradialis causes full elbow flexion and rotation of the forearm to the near neutral position. Studies shows that the brachioradialis is a primary elbow flexor, especially during rapid movements against high resistance. The brachioradialis is a major exception to the generalization that the radial nerve supplies only extensor muscles and that all flexors lie in the anterior compartment. As previously mentioned, the brachioradialis is functionally a flexor of the forearm but is located in the (posterolateral) or extensor compartment and is thus supplied by the radial nerve.
The brachioradialis muscle can be readily palpated on the antero-lateral aspect of the forearm. Resisted elbow flexion, from a position of about 90 degrees and neutral forearm rotation, causes the muscle to stand out or “bowstring” sharply across the elbow. The bowstringing of this muscle increases its flexion moment arm to a length that exceeds all other flexor muscles.
The triceps brachii has 3 heads: long, lateral, and medial. The long head has its proximal attachment on the infraglenoid tubercle of the scapula, thereby allowing the muscle to extend and adduct the elbow. The long head has an extensive volume, exceeding all other muscles of the elbow. The lateral and medial heads have their proximal attachments on the humerus, on either side and along the radial groove. The medial head has an extensive proximal attachment on the posterior side of the humerus, occupying a location relatively similar to that of the brachialis on the bone’s anterior side. It is considered as the “workhorse” of the extensors. The anconeus muscle is a small triangular muscle spanning the posterior side of the elbow. The muscle is located between the lateral epicondyle of the humerus and a strip along the posterior aspect of the humerus. The anconeus appears as the 4th head of the extensor mechanism, similar to the quadriceps at the knee. The triceps brachii produces the majority of the total extensor torque at the elbow. Compared with the triceps muscle, the anconeus has a relatively a small moment arm for extension.
Elbow extension generates different levels of activation for the extensor muscles. During submaximal efforts of elbow extension, different muscles are recruited only at certain levels of effort. The anconeus is usually the first muscle to initiate and maintain low levels of elbow extension force. As extensor effort gradually increases, the medial head of the triceps is usually next in line to join the anconeus. The medial head remains active for most elbow extension movements. The medial head has been termed the “the workhorse” of the extensors, functioning as the extensor counterpart of the brachialis muscle. Only after extensor demands at the elbow increase to moderate-to-high levels does the nervous system recruit the lateral head of the triceps, followed closely by the long head. The long head functions as a “reserve” elbow extensor, equipped with a large volume suited for tasks that require high work performance.
The borders of the DELTOID MUSCLE are visible when the arm is abducted against resistance. The DISTAL ATTACHMENT OF THE DELTOID MUSCLE can be palpated on the lateral surface of the humerus. The THREE HEADS OF TRICEPS form a bulge on the posterior aspect of the arm and are identifiable when the forearm is extended from the flexed position against resistance. The TRICEPS TENDON may be palpated as it descends along the posterior aspect of the arm to the olecranon. The BICEPS BRACHII form a bulge on the anterior aspect of the arm; its belly becomes more prominent when the elbow is flexed and supinated against resistance. MEDIAL AND LATERAL BICIPITAL GROOVES separate the bulges formed by the biceps and the triceps. The CEPHALIC VEIN runs superficially in the lateral bicipital groove and the BASILIC VEIN ascends in the medial bicipital groove. The BICEPS TENDON can be palpated in the cubital fossa, immediately lateral to the midline. The PROXIMAL PART OF THE BICIPITAL APONEUROSIS can be palpated where it passes obliquely over the brachial artery and the median nerve. The BRACHIAL ARTERY may be felt pulsating deep to the medial border of the biceps.
The anterior surface of the elbow is characterized by an area of shallow triangular depression known as the CUBITAL FOSSA. This area is important as it contains the important neurovascular structures, the muscles and the tendons that subserve the effector organ of the upper limb which is the hand. The boundaries of the cubital fossa are: 1. Superiorly- an imaginary line connecting the medial and lateral epicondyles 2. Medially- the pronator teres 3. Laterally- the brachioradialis The floor of the cubital fossa is formed by the brachialis and supinator muscles. The roof of the cubital fossa is formed by the continuity of brachial and antebrachial (deep) fascia.
The contents of the cubital fossa are: 1. Terminal part of the BRACHIAL ARTERY and the commencement of its terminal branches, the RADIAL AND THE ULNAR ARTERIES; the brachial artery lies between the bicep tendon and the median nerve. 2. The (deep) accompanying veins of the arteries; 3. the BICEPS BRACHII tendon; 4. the MEDIAN NERVE; 5. RADIAL NERVE, dividing into its superficial and deep branches
The forearm lies between the elbow and the wrist and contains two bones- the radius and ulna, which are bound by the INTEROSSEOUS MEMBRANE. The role of the forearm movement, occurring at the elbow and radioulnar joints, is to assist the shoulder in the application of force and in controlling the placement of the hand in space.
Distally directed force as in holding a heavy suitcase with the elbow extended causes a distracting force almost entirely through the radius. The predominant fiber direction of the interosseous membrane is not aligned to resist distally applied forces on the radius. The distal pull on the radius slackens rather than tenses the interosseous membrane, thereby necessitating the less capable tissues, such as the oblique cord and annular ligament, to accept the weight of the load. Contraction of the brachioradialis or other muscles normally involved with the grasp can assist with holding the radius and the load against the humeroradial joint. Complaints of a deep aching in the forearm from persons who carry heavy loads for extended periods may be from fatigue in these muscles. Supporting loads through the forearm at shoulder level, for example, like a waiter carrying a tray of food, directs the weight proximally through the radius where the interosseous membrane can assist with dispersing these loads more evenly through the forearm.
Most of the fibers of the INTEROSSEOUS MEMBRANE of the forearm are directed away from the radius in an oblique medial and distal direction. One of these bands, the OBLIQUE CORD, runs from the lateral side of the tuberosity of the ulna to just distal to the bicipital tuberosity. One of the functions of the interosseous membrane is force transmission through the upper limb. As illustrated in the right side slide, a compression force through the hand is transmitted primarily through the wrist at the radiocarpal joint and to the radius. About 80% of the compression force due to bearing weight through the forearm crosses the wrist between the lateral side of the carpus and the radius. The remaining 20% of the compression force passes across the medial side of the carpus and the ulna at the “ulnocarpal space.” Because of the fiber direction of the interosseous membrane, part of the proximal directed force through radius is transferred across the membrane to the ulna. This mechanism allows a share of the compression force at the wrist to cross the elbow via the humeroulnar joint, thereby reducing the amount of force that must cross the limited surface area of the humeroradial joint.
The flexor-pronator muscles occupy the anterior compartment of the forearm and, the tendons of these muscles pass across the anterior surface of the wrist and are held in place by the PALMAR CARPAL LIGAMENT and the FLEXOR RETINACULUM (or, the TRANSVERSE CARPAL LIGAMENT). Both the palmar carpal ligament and the transverse carpal ligament are thickenings of the antebrachial fascia.
The above slide shows the anterior and posterior compartments of the forearm and the structures included in its compartment. Take note that the osseofibrous structures composed of the radius, ulna and the interosseous membrane effectively separate the extensor and posterior compartments. Also take note that there are more neurovascular structures in the anterior (or, flexor- pronator compartment) compared to the extensor compartment. The muscles and the neurovascular structures in each compartment are fully separated from each other by enclosing fascia coming from the deep fascia. Such peculiar arrangement makes the forearm susceptible to increase compartment syndrome secondary to traumatic causes.
The flexor muscles are arrange in 3 layers or groups. 1. A superficial layer or group of 4 muscles: pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. These muscles are all attached proximally by a common tendon to the medial epicondyle of the humerus, the common flexor origin. 2. An intermediate layer consisting of one muscle, the flexor digitorum superficialis 3. A deep layer consisting of 3 muscles, namely: flexor digitorum profundus, flexor pollicis longus, and pronator quadratus. Functionally, the brachioradialis is a flexor of the forearm but is located in the posterolateral, or, extensor compartment and is thus supplied by the radial nerve. Therefore, the brachioradialis is a major exception to the generalization that the radial nerve supplies only the extensor muscles and that all flexors lie in the anterior compartment. The 5 superficial and intermediate muscles cross the elbow joint; the 3 deep muscles do not. The long flexors of the digits (FDS and FDP) also flex the metacarpophalangeal joint and wrist joints. The FDP flexes the fingers in slow action; this action is reinforced by the FDS when speed and flexion against resistance are required. When the wrist is flexed at the same time as the metacarpophalangeal and interphalangeal joints are flexed, the long flexors of the fingers are operating over a shortened distance between attachment, and the action resulting from their contraction is consequently weaker. Extending the wrist increases their operating distance, and thus their contraction is more efficient in producing a strong grip. Tendons of the long flexors of the digits pass through the distal part of the forearm, wrist, and palm and continue to the medial 4 fingers. The FDS flexes the middle phalanges; the FDP flexes the distal phalanges. The pronator quadratus is the prime mover for pronation. The pronator quadratus initiates pronation and is assisted by the pronator teres when more speed and power is needed. The pronator quadratus also helps the interosseous membrane hold the radius and ulna together, particularly when upward thrusts are transmitted through the wrist (e.g., during a fall on the hand).
The above slide shows the surface projection of the superficial layer of the flexor pronator group of muscles using the four fingers. The index finger represents the position of the pronator teres muscle; the middle finger represents the position of the flexor carpi radialis; the ring finger represents the palmaris longus, and; the small finger represents the position of the flexor carpi ulnaris.
The above slide shows the surface projection of the tendons of the different forearm muscles at the anterior aspect of the wrist. Some of the tendons can be palpated or seen clearly.
The 2nd layer, or intermediate layer, of flexor muscle is composed only of the FLEXOR DIGITORUM SUPERFICIALIS (FDS) has the following proximal attachment: the medial epicondyle of the humerus(the common flexor origin), medial ligament of the elbow, the medial border of the coronoid process of ulna, the fibrous arch connecting coronoid process of ulna with anterior oblique line of radius. It is inserted to the volar aspect of the middle phalanges of the medial four fingers.
The 3rd, or deep, layer of flexor muscles are composed of the FLEXOR DIGITORUM PROFUNDUS and the FLEXOR POLLICIS LONGUS. The flexor digitorum profundus has its origin at the upper three fourths of anterior surface of the ulna and the interosseous membrane and, is inserted into the bases of the distal phalanges the four medial fingers. The flexor pollicis longus has its origin at the upper three fourths of anterior surface of radius. It is inserted to the base of the distal phalanx of the thumb.
The above slide shows the proximal attachments (blue areas) and distal attachments (red areas) of the forearm muscles at the anterior (or flexor-pronator) compartment.
The 3 primary wrist flexors are the flexor carpi radialis, the flexor carpi ulnaris, and, when present and fully formed the palmaris longus. The palmaris longus is missing in about 10% of people, however. When present, it is extremely variable and may have several small tendons. The palmar carpal ligament, which is analogous to the extensor retinaculum, stabilizes the tendons of the wrist flexors and prevents excessive bowstringing during flexion. Other secondary muscles capable of flexing the wrist are the extrinsic flexors of the digits- FDS, FDP, FPL. With the wrist in neutral position, the abductor pollicis longus and the extensor pollicis brevis have a small moment arm for wrist flexion. The proximal attachment of the primary wrist flexors are located on and near the medial (“flexor-pronator”) epicondyle of the distal humerus and the dorsal border of the ulna. The flexor carpi radialis and flexor carpi ulnaris function synergistically to flex the wrist; however, they oppose each other’s radial and ulnar deviation ability.
Distally, the tendon of the flexor carpi radialis does not cross the wrist the carpal tunnel( that is, it does not enter the carpal tunnel); rather, the tendon passes in a separate tunnel formed by a groove in the trapezium and fascia from the adjacent transverse carpal ligament. The tendon of the flexor carpi radialis attaches distally to the palmar base of the second and, sometimes, the third metacarpal. The palmaris longus tendon has an extensive distal attachment primarily to the thick aponeurosis of the palm of the hand. The tendon of the flexor carpi ulnaris courses distally to attach to the pisiform bone and, in a plane superficial to the transverse carpal ligament, into the pisohamate and pisometacarpal ligaments and the palmar base of the 5th metacarpal bone.
In the neutral wrist position, the extensor carpi radialis longus possesses the radiation torque or power, followed by the abductor pollicis longus and the extensor pollicis brevis. The abductor pollicis longus and the extensor pollicis brevis provide stability to the radial side of the wrist along with the radial collateral ligament.
The slide above shows the radial deviator muscles are contracting while using a hammer. All these muscles pass laterally to the wrist’s anterior-posterior axis rotation. The action of the extensor carpi radialis longus and the flexor carpi radialis are synergistic in nature. The two muscles cooperating as synergist for one action and acting as antagonists in another. By opposing each other’s flexion and extension potential, these muscles stabilize the wrist in an extended position necessary to grasp the hammer effectively.
The primary muscles capable of ulnar deviation of the wrist are the extensor carpi ulnaris and the flexor carpi ulnaris. In the above slide, both muscles are contracting to drive a nail with a hammer. Both muscles contract synergistically to perform ulnar deviation, but also to stabilize the wrist in a slightly extended position. Because of the strong functional association of the extensor carpi ulnaris and flexor carpi ulnaris muscles, injury to either muscle can incapacitate the overall kinetics of ulnar deviation. For example, rheumatoid arthritis often causes inflammation and pain in the extensor carpi ulnaris near its distal attachment. Attempts at active ulnar deviation with minimal to no activation in the painful extensor carpi ulnaris causes the action of the flexor carpi ulnaris to remain unopposed. The resulting flexed posture of the wrist is thereby not suitable for an effective grasp.
The extensor muscles are in the posterior (extensor-supinator) compartment of the forearm, and all are innervated by branches of the radial nerve. These muscles may be organized into 3 functional groups, namely 1. Muscles that extend and abduct or adduct the hand at the wrist joints- extensor carpi radialis longus and brevis, extensor carpi ulnaris. 2. Muscles that extend the medial four digits- extensor digitorum, extensor indicis, and extensor digiti minimi 3. Muscles that extend or abduct the thumb- abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus.
Anatomically, however, the extensor muscles are organized into SUPERFICIAL AND DEEP LAYERS. Four superficial extensors (namely, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris) are attached proximally by a common extensor tendon to the lateral epicondyle. Two other superficial belonging to the extensor compartment- the brachioradialis and the extensor carpi radialis longus have their proximal attachment to the lateral supraepicondylar ridge of the humerus and to the lateral intermuscular septum. The brachioradialis muscle is technically a flexor elbow muscle. The 4 flat tendons of the extensor digitorum pass deep to the extensor retinaculum to the medial 4 fingers. The common tendons of the index and little fingers are joined on their medial sides near the knuckles by the respective tendons of the extensor indicis and extensor digiti minimi (extensors of index and little fingers, respectively). The deep extensor muscles of the forearm (APL, EPB, EPL) act on the thumb. The extensor indicis confers independence to the index finger it may act alone or act together with the extensor digitorum to extend the index finger. The 3 muscles acting on the thumb (APL, EPL, and EPB) are deep to the superficial extensors and emerge ( “crop out”) from a furrow in the lateral part of the forearm that divides the extensors. Because of this characteristics, they are referred to as OUTCROPPING MUSCLES. The tendons of the APL and EPB bound the triangular ANATOMICAL SNUFF BOX laterally, and the tendon of the EPL bounds it medially. The ANATOMICAL SNUFF BOX is a visible hollow on the lateral aspect of the wrist when the thumb is fully extended. During full thumb extension, the tendons of APL, EPB, and EPL are raised and produce a concavity between them.
The three primary wrist extensors are the EXTENSOR CARPI RADIALIS LONGUS, EXTENSOR CARPI RADIALIS BREVIS, EXTENSOR CARPI ULNARIS. The extensor digitorum communis is capable of generating significant wrist extension torque, but is primarily involved in finger extension. Other secondary wrist extensors are the extensor indicis, extensor digiti minimi and the extensor pollicis longus. The proximal attachments of the primary wrist extensors are located on and near the lateral (extensor-supinator) epicondyle of the humerus and dorsal border of the ulna. Distally, the extensor carpi radialis longus and brevis attach side by side to the dorsal bases of the second (for the ECRL) and 3rd (for the ECRB) metacarpals; the extensor carpi ulnaris attaches to the dorsal base of the 5th metacarpal.
The main function of the wrist extensors is to position and stabilize the wrist for activities involving the fingers. Of particular importance is the role of the wrist extensor in making fist. To demonstrate this, rapidly tighten and release the fist and note the strong synchronous activity from the wrist extensor. In gripping an object, the contraction of the long finger flexors, such as the flexor digitorum superficialis and the flexor digitorum profundus, flex the fingers but also cause simultaneous wrist flexion torque. Activation of the wrist extensors, such as the extensor carpi radialis brevis, is necessary to block the wrist flexion tendency caused by activated finger flexors. In this manner, the wrist extensors are able to maintain the optimal length of the finger flexors to effectively flex the fingers. The most active wrist extensor muscle during light closure of the fist is the extensor carpi radialis brevis. As grip force increases, the extensor carpi ulnaris, followed closely by the extensor carpi radialis longus, joins the activated extensor carpi radialis brevis. Of the 3 primary wrist extensors, the extensor carpi radialis brevis is located most centrally at the wrist and has the greatest moment arm for extension Activities that require repetitive forceful grasp, such as hammering, or playing tennis, may overwork the highly active ECRB. A condition known as LATERAL EPICONDYLITIS, or “TENNIS ELBOW”, occurs from stress and resultant inflammation of the proximal attachment of the wrist extensors.
The slide above shows the relationship of the wrist angle and the compressive force generated in executing grip. At neutral or 0 degree, the grip strength is about 200 newtons. Increasing the wrist flexion to 60 degrees resulted in a drop of the grip strength to about 175 newtons. However, dorsiflexing the wrist to about 30 degrees increases the grip strength to 500 newtons. This study shows that as a strong grip is applied to an object, the wrist extensors hold the wrist in about 35 degrees of extension and about 5 degrees of ulnar deviation. Grip strength is significantly reduced when the wrist is fully flexed. This decreased grip strength is caused by a combination of two factors. First, and most likely foremost, the finger flexors cannot generate adequate force because they are functioning at an extremely shortened (slackened) length on their length-tension curve. Second, the overstretched finger extensors, particularly the extensor digitorum communis, create a passive torque at the fingers, which further reduces effective grip force. The combination of physiologic events explains why a person with paralyzed wrist extensors has difficulty producing an effective grip even though the finger flexors remain fully innervated.
The slide above shows a person with paralysis of the right wrist extensor muscles, following the radial nerve injury, is performing a maximum effort grip using a dynamometer. In picture A, despite normally innervated finger flexor muscles, maximal grip strength measures only about 10 lbs. In picture B, the same person is shown stabilizing her wrist in order to prevent it from flexing during the grip effort. Note that the grip force more than double.
The extensor tendons are held in place in the wrist region by the extensor retinaculum, which prevents bowstringing of the tendons when the hand is held in extended at the wrist joint. As the tendon pass over the dorsum of the wrist, they are covered with synovial sheaths, which reduce friction for the extensor tendons as they traverse the osseofibrous tunnels formed by the attachment of the extensor retinaculum to the distal radius and ulna. The four flat tendons of the extensor digitorum pass deep the extensor retinaculum to the medial 4 fingers. The common tendons of the index and little fingers are joined on their medial sides near the knuckles by the respective tendons of the extensor indicis and extensor digiti minimi (extensors of the index and little fingers, respectively). The extensor indicis joins the tendon of the extensor digitorum to pass deep to the extensor retinaculum through the tendinous sheath of extensor digitorum and extensor indicis (common extensor synovial sheath). On the dorsum of the hand, the tendons of extensor digitorum spread out as they run toward the finger. Adjacent tendons are linked proximal to the metacarpal joints by 3 oblique intertendinous connections that restrict independent extension of the fingers. Consequently, normally no finger can remain fully flexed as the other ones are fully extended. On the distal ends of the metacarpals and along the phalanges, the 4 tendons of extensor digitorum flatten to form the EXTENSOR EXPANSIONS. Each extensor expansion (dorsal expansion or hood) is a triangular tendinous aponeurosis that wraps around the dorsum and sides of the head of the metacarpal and base of the proximal phalanx
The tendons of the muscles that cross the dorsal and dorsal-radial side of the wrist are secured in place across the wrist by the EXTENSOR RETINACULUM. The extensor retinaculum wraps around the styloid process of the ulna to attach palmarly to the flexor carpi ulnaris, pisiform, and pisometacarpal ligament. The retinaculum attaches to the radial styloid process and the radial collateral ligament. Between the extensor retinaculum and the dorsal surface of the wrist are 6 fibro-osseous tunnels that house the tendons along with their synovial sheaths. The extensor retinaculum prevents the tendons from “bowstringing” up and away from the radiocarpal joint during active extension. The retinaculum and associated tendons also assist the dorsal capsular ligaments in stabilizing the dorsal side of the wrist.
Each extensor expansion (dorsal expansion or hood) is a triangular tendinous aponeurosis that wraps around the dorsum and sides of the metacarpal head and base of the proximal phalanx. The visor-like “hood” of the extensor expansion over the head of the metacarpal is anchored on each side to the palmar ligament ( a thickened portion of the fibrous layer of the joint capsule of the metacarpophalangeal joints). In forming the expansion, each extensor digitorum divides into a MEDIAN BAND, which passes to the base of the middle phalanx and 2 LATERAL BANDS, which pass to the base of the distal phalanx. The tendons of the interosseous and lumbrical muscles of the hand join the lateral bands of the extensor expansion.
The ANATOMICAL SNUFF BOX is a visible hollow on the lateral aspect of the wrist when the thumb is fully extended; this draws the APL, EPB, and EPL tendons to become prominent and produces a concavity between them. Several structures are found in the anatomical snuff box. 1.The radial artery lies on the floor of the snuff box. 2. The radial styloid process can be palpated proximally and the 3. base of the first metacarpal can be palpated distally in the snuff box. 4. The carpal scaphoid and the trapezium can be felt in the floor of the snuff box between the radial styloid process and the first metacarpal.
In order to pronate or supinate, a muscle must possess two biomechanical features. First the muscle must have one attachment on the humerus and ulna, and the other on the radius and hand. Muscles such as the brachialis or extensor pollicis brevis, therefore, cannot pronate or supinate the forearm. The brachialis has its proximal attachment to the anterior surface of the distal half of the humerus and its distal attachment on the anterior surface the coronoid process and tuberosity of the proximal ulna. The extensor pollicis brevis muscle, on the other hand, has its proximal attachment to the posterior surface of the radius and the interosseous membrane while its distal attachment is to the dorsal aspect of base of proximal phalanx of the thumb. Second, the muscle must have a line-of-force that intersects the axis of rotation for pronation and supination. As a general rule, the closer the line-of-force of a muscle is to the a perpendicular intersection with the axis of rotation, the more likely the muscle is a significant torque generator. On the other hand, a muscle with a line-of-force that runs parallel to the axis of rotation has a 0 degree angle of intersection and, therefore, has no moment arm to pronate or supinate.
The above slide shows the line-of-force of the different muscles that act either as supinators or pronators. In illustration A, a pronated hand, that is about to supinate, is acted by the different supinators like the biceps brachii, supinator, extensor pollicis longus, and extensor indicis. Note that the line of force of these muscles intersect with the line of rotation of the supination. In a supinated hand that is about to pronate, the line of force of the pronators intersect the axis of rotation of pronation.
The supinator muscle has a complex proximal attachment. A superficial set of fibers arise from the lateral epicondyle of the humerus and the lateral collateral and annular ligament. A deeper set of fibers arises from the ulna near and along the supinator crest. Both sets of muscle fibers attach along the proximal third of the radius. From a pronated view as shown at the left slide, the supinator is elongated and in excellent position to rotate the radius into supination. The supinator has only minimal attachments to the humerus and passes too close to the medial-lateral axis of rotation at the elbow to produce significant torque. The Supinator is a relentless forearm supinator similar to the brachialis during elbow flexion. The supinator generates significant muscle activity during forearm supination regardless of the elbow angle, or the speed or power of the action. The nervous system usually recruits the supinator muscle for low-power task that require supination motion only.
The biceps brachii is a powerful supinator muscle of the forearm. The biceps has about 3x the physiologic cross-section as the supinator. It becomes a dominant supinator when the elbow is flexed to 90 degrees and when the activity performed requires a rapid and forceful pronation-supination motions. The biceps brachii spans two joints- the shoulder proximally and the elbow distally. Its long head has its attachment to the supraglenoid tubercle of the scapula while its short head is proximally attached to the coracoid process. Its distal attachment is to the radial tuberosity which is located at the medial side of the proximal radius, and to the fascia of the forearm through the bicipital tuberosity. When the elbow is extended, the biceps brachii is a simple flexor of the forearm; however, when the elbow is flexed and more power is needed against resistance (e.g., when right-handed person drives a screw into a hard wood), the biceps is the primary and most powerful supinator of the forearm. The biceps brachii is also used when inserting a cork screw and pulling the cork from a wine bottle. The biceps barely operates during flexion of a prone forearm.
The line-of-force of the biceps brachii is 90 degrees perpendicular and medial to the axis of the radius.
The primary muscles for pronation are the pronator quadratus and pronator teres. The pronator quadratus is located at the extreme distal end of the anterior forearm, deep to all the wrist flexors and extrinsic finger flexors. This flat quadrilateral muscle attaches between the anterior surfaces of the distal ¼ of the ulna and the radius. Overall, from proximal to distal, the pronator quadratus has a slight obliquity in fiber direction, similar to, but not quite as angled, as the pronator teres. The pronator quadratus is the most active and consistently used pronator muscle, involved during all pronation movements, regardless of the power demands or the amount of associated elbow flexion. The pronator teres has two heads: humeral and ulnar. The median nerve passes between these two heads. The pronator teres functions as a primary pronator of the forearm , in addition to a secondary elbow flexor. This muscle becomes highly active in activities requiring higher power pronation actions such as attempting to unscrew an overtightened screw with the right hand or pitching a baseball. The triceps is an important synergist to the pronator teres, often required to neutralize the tendency of the pronator teres to flex the elbow.
When high-power supination torques are needed to vigorously turn a screw, the biceps is used to assist other muscles, such as the supinator and the extensor pollicis longus. The elbow is usually held flexed to about 90 degrees in order to augment the supination torque potential of the biceps. The maintenance of this elbow posture during the task requires that the triceps co-contract synchronously with the biceps muscle. The triceps supply the essential force during this activity since it prevents the biceps from actually flexing the elbow and shoulder during the supination effort. Unopposed biceps action causes the screwdriver to be pulled away from the screw on every effort- hardly effective. By attaching to the ulna versus the radius, the triceps is able to neutralize the elbow flexion tendency of the biceps without interfering with the supination task. This muscular cooperation is an excellent example of how two muscles can function as synergists for one activity, while at the same time remain as direct antagonists.
The wrist contains eight small bones, which as a group act as a flexible “spacer” between the forearm and hand. Each carpal bone articulates with one or two others to form the intercarpal joints. In addition to several small intercarpal joints, the wrist or carpus functions as two major articulations. The RADIOCARPAL JOINT is located between the distal end of the radius and the proximal row of carpal bones. Just distal to the radiocarpal joint is the MIDCARPAL JOINT, located between the proximal and distal row of carpal bones. These two joints allow the wrist to flex and extend and to move from side to side in a motion called radial and ulnar deviation. The distal radioulnar joint is considered a part of the forearm complex, rather than the wrist, due to its role in pronation and supination. The position of the wrist significantly affects the function of the hand. Many muscles that control the fingers originate extrinsic to the hand, with their proximal attachments located in the forearm. The position of the wrist, therefore, is critical in setting the length-tension relationship of the extrinsic finger muscles. A fused, weak,or painful wrist often assumes a posture that interferes with the optimal length of the extrinsic musculature of the hand. The motion of the wrist is very much linked to the motion of the hand.
The dorsal surface of the distal radius has several grooves and raised areas that help guide many tendons of extrinsic muscles. The palpable dorsal (or Lister’s) tubercle separates the tendons of the extensor carpi radialis brevis and the extensor pollicis longus. The STYLOID PROCESS of the radius projects from the lateral side of the radius. The STYLOID PROCESS OF ULNA, much sharper than its radial counterpart, extends distally from the posterior-medial surface of the ulna.
The distal articular surface of the radius is concave in both medial-lateral and anterior-posterior directions. Facets are formed in the articular cartilage from indentations made by the scaphoid and lunate bones of the wrist. The distal end of the radius has two configurations of biomechanical importance. First, the distal end of the radius angles about 25 degrees toward the ulnar(medial) direction. This ULNAR TILT allows the wrist and hand to rotate farther into ulnar deviation than into radial deviation. As a result of the tilt, radial deviation of the wrist is limited by impingement of the lateral side of the carpus against the styloid of the radius. Second, the distal articular surface of the radius is angled about 10 degrees in the palmar direction. This accounts, in part, for the greater amounts of flexion that extension of the wrist.
The distal end of the radius, when viewed anteriorly, angles about 25 degrees toward the ulna. This is the ULNAR TILT. This ulnar tilt allows the wrist and hand to rotate farther into ulnar deviation than into radial deviation. In slide B, the distal end of the radius, as seen at the medial side is angled about 10 degrees in the palmar direction. This is the PALMAR TILT. This palmar tilt allows, in part, for greater amounts of wrist flexion than extension.
The above slide shows the range of flexion and extension motion of the wrist. Note that the range of flexion far exceeds wrist extension. The range of motion for radial deviation is less compared that of ulnar deviation. The PALMAR TILT accounts, in part, for the greater amounts of wrist flexion that wrist extension. The ULNAR TILT accounts for the greater range of motion of ulnar deviation than radial deviation
Many daily activities require 45 degrees of sagittal plane motion: from 5 to 10 degrees of flexion to 30 to 35 degrees of wrist extension. In addition, many activities require 25 degrees of frontal plane of motion: from 15 degrees of ulnar deviation to 10 degrees of radial deviation. Medical management of a severely painful or an unstable wrist sometimes requires surgical fusion. To minimize the functional impairment of this procedure, a wrist may be fused in an “average” position of function about 10 to 15 degrees of extension and 10 degrees of ulnar deviation
From a radial(lateral) to ulnar direction, the proximal row of carpal bones includes the SCAPHOID (or, Navicular), LUNATE, TRIQUETRUM, and PISIFORM. The distal row includes the TRAPEZIUM, TRAPEZOID, CAPITATE, and HAMATE. The proximal row of carpal bones in joined in relatively loose fashion. In contrast, the distal row of carpal bones is bound tightly by strong ligaments, providing a rigid and stable base for articulation with the metacarpal bones.
The scaphoid, or navicular, is named based on its vague resemblance to a boat. Most of the “hull” or bottom of the boat rides on the radius; the cargo area of the “boat” is filled with the head of the capitate. The scaphoid is in contact with 4 carpal bones and the radius. The scaphoid has two convex surfaces called poles. The proximal pole articulates with the scaphoid facet of the radius. The distal pole of the scaphoid is a slightly rounded surface, which articulates with trapezium and trapezoid. The scaphoid has a rather large and blunt tubercle, which projects palmarly from the distal pole. The distal-medial surface is deeply concave to accept the lateral half of the prominent head of the capitate. A small facet on the medial side contacts with the lunate. The scaphoid and the distal radius are located in the direct path of most of the force transmission through the wrist. Injury from falling on an extended and radially deviated wrist often results in fracture to the scaphoid. Fracture of the scaphoid occurs more frequently than any other fractures of the carpal bones. Healing is often hindered if the fracture is at the scaphoid’s proximal pole because blood supply is often absent or minimal in this region. Seventeen per cent of all scaphoid fractures are associated with other injuries along the weight-bearing path of the wrist and hand. Associated injuries often involve fracture and/or dislocation of the lunate and fracture of the trapezium and distal radius.
The lunate (from the Latin Luna, moon) bone is the central bone of the proximal row, wedged between the scaphoid and the triquetrum. Like the scaphoid, the lunate’s proximal surface is convex to fit into the concave facet on the radius. The distal surface of the lunate is deeply concave, giving he bone its crescent moon-shaped appearance. This articular surface accepts two convexities- the medial half of the head of the capitate and part of the apex of the hamate. TRIQUETRUM: this triangular-shaped carpal bone occupies the most ulnar position in the wrist, just medial to the lunate. The lateral surface of the triquetrum is long and flat for the articulation with a similarly shaped surface of the hamate.
PISIFORM: The pisiform, meaning “shaped like a pea,” articulates loosely with the palmar surface of the triquetrum. It rests upon the palmar surface of the triquetrum. This easily mobile and palpable bone is the attachment site for several muscles and ligaments. Otherwise, the pisiform has little functional significance in the kinematics of the wrist. TRAPEZIUM: The trapezium, or greater multangular bone, has an asymmetric shape. The proximal surface is slightly concave for articulation with the scaphoid. Of particular importance is the distal saddle-shaped surface, which articulates with the base of the first metacarpal. The carpometacarpal joint is highly specialized articulation allowing a wide range of motion to the human thumb. A slender and sharp tubercle projects from the palmar surface of the trapezium. This tubercle and the palmar tubercle of the scaphoid provide attachment for the lateral side of the TRANSVERSE CARPAL LIGAMENT. Immediately medial to the palmar tubercle is a distinct groove for the tendon of the flexor carpi radialis. TRAPEZOID: the trapezoid, or lesser multangular, is a small bone wedged tightly between the capitate and the trapezium, has a proximal surface that is slightly for the articulation with the scaphoid. The bone makes a relatively firm articulation with base of the 2nd metacarpal bone. HAMATE: The hamate is named after a large hooklike process that projects from its palmar surface. The hamate has a general shape of a pyramid. Its base, or distal surface, articulates with the bases of the 4th and 5th metacarpals. This articulation provide mobility to the ulnar aspect of the hand, most noticeably when cupping the hand. The apex of the hamate, its proximal surface, projects toward the concave surfaces of the lunate. The hook of the hamate and the pisiform bone provides attachment for the medial side of the transverse carpal ligament.
CARPAL TUNNEL: The palmar side of the carpal bones forms a concavity. Arching over this concavity is a thick fibrous band of connective tissue known as the TRANSVERSE CARPAL LIGAMENT which is connected to the four raised points on the palmar carpus, namely, the PISIFORM and the HOOK OF THE HAMATE on the ulnar side and the tubercles of the SCAPHOID and the TRAPEZIUM on the radial side. The transverse carpal ligament serves as a primary attachment site for many muscles located within the hand and the PALMARIS LONGUS, a wrist flexor. The transverse carpal ligament converts the palmar concavity made by the carpal bones into a carpal tunnel. This tunnel serves as a passageway for the MEDIAN NERVE and the tendons of extrinsic digital flexor muscles- FDS and FDP.
The above slide is a cross section at the level of the wrist. It shows the transverse ligament arching over the wrist are. Between the transverse carpal ligament above and the distal row of carpal bones below. At the center between the transverse carpal ligament and the distal row of carpal bones is the carpal tunnel. Also shown are the structures that pass through this carpal tunnel. These are the tendons of the flexor digitorum superficialis and the flexor digitorum profundus; flexor pollicis longus; the median nerve. Dorsal to the distal row of carpal bones are the 6 extensor compartments with corresponding enclosed extensor tendons.
The primary joints of the wrist are the RADIOCARPAL JOINT AND THE MIDCARPAL JOINT. Many less significant intercarpal joints exist between adjacent carpal bones. These joints are called the intercarpal joints. The motion that occur in the intercarpal joints are relatively small compared to the radiocarpal and the midcarpal joints. Nevertheless, the motion occurring in the intercarpal joints is important to the completion of full range of wrist motion. RADIOCARPAL JOINT: This is the articulation between the distal concave joint surfaces of the radius and the adjacent articular disc with the convex proximal surfaces of the SCAPHOID and the LUNATE. The TRIQUETRUM is also considered part of the radiocarpal joint because at full ulnar deviation it medial surface makes contact with the articular disc. The thick articular surface of the distal radius and the articular disc accept and disperse the forces that pass from the carpus to the forearm. Approximately 20% of the total compression force that crosses the wrist passes through the disc. The remaining 80% passes directly through the scaphoid and lunate to the radius. The contact areas at the radiocarpal joint tend to be greatest when the wrist is extended and ulnarly deviated. This is the wrist position where maximal grip strength is obtained. MIDCARPAL JOINT: The midcarpal joint is the articulation between the proximal and distal carpal bones. The capsule that surrounds the midcarpal joint is continuous with each of the intercarpal joints. The midcarpal joint can be divided into medial and lateral joint compartments. The larger medial compartment is formed by the convex head of the capitate and apex of the hamate, fitting into the concave recess formed by the distal surfaces of the scaphoid, lunate and triquetrum. The lateral compartment of the midcarpal joint is formed by the junction of the slightly convex distal pole of the scaphoid with the slightly concave proximal surfaces of the trapezium and trapezoid. The lateral compartment lacks the pronounced ovoid shape of the medial compartment. There is less motion noted in the lateral compartment compared to the medial compartment.
A fibrous capsule surrounds the external surface of the wrist and the distal radioulnar joint.
Dorsally, the capsule thickens slightly to form ligamentous bands known as the dorsal radiocarpal ligaments. These ligaments are thin and very difficult to distinguish from the capsule itself. In general, the dorsal radiocarpal ligaments travel distally in ulnarly direction, from the distal radius to the dorsal surfaces of the scaphoid and the lunate. A larger discrete set of fibers extends to the triquetrum. The dorsal radiocarpal ligaments reinforce the posterior side of the radiocarpal joint, becoming taut in full flexion. The lateral part of the wrist capsule is strengthened by the fibers called the radial collateral ligament. These fibers attached proximally to the styloid process, and distally to the scaphoid tubercle, trapezium, and adjacent transverse carpal ligament. This ligament provides only part of the lateral stability to the wrist. A major portion is furnished by the extrinsic muscles, such as the abductor pollicis longus and the extensor pollicis brevis. The radial collateral ligament is more developed in the palmar side than in the dorsal side. These fibers become maximally taut when ulnar deviation of the wrist is combined with extension.
At the palmar aspect of the wrist, the ligaments that stabilize the carpal bones are separate from the palmar capsule of the wrist. These ligaments are located deep to the wrist capsule. These ligaments are several and, are known collectively as the PALMAR RADIOCARPAL LIGAMENTS. These include the RADIOCAPITATE LIGAMENT, RADIOLUNATE LIGAMENT, and, in the deeper plane , the RADIOSCAPHOLUNATE LIGAMENT. Each ligament arises from a roughened area on the distal radius, travels distally in ulnar direction, and attaches to the palmar surface of several carpal bones. The palmar radiocarpal ligaments are much stronger and thicker than the dorsal radiocarpal ligaments. Significant tension exists in these ligaments even in the relaxed neutral wrist position. In general, the palmar radiocarpal ligaments become maximally taut at full wrist extension.
A complex set of connective tissue exists near the ulnar border of the wrist known as the ULNOCARPAL COMPLEX. This group of connective tissue is often referred to as the triangular fibrocartilage complex (TFCC). The ULNOCARPAL COMPLEX includes the ff: 1. the ARTICULAR DISC; 2. the ULNAR COLLATERAL LIGAMENT; 3. the PALMAR ULNOCARPAL LIGAMENT. This complex set of connective tissue fills most of the ULNOCARPAL SPACE between the ulna and the carpal bones. The ulnocarpal space allows the carpal bones to pronate and pronate with the radius, without interference from the distal end of the ulna.
The intrinsic ligaments of the wrist are classified as short, intermediate, or long. Short ligaments within the wrist connect the bones of the distal row of carpal bones by their palmar, dorsal, or interosseous surfaces. The short ligaments firmly stabilize and unite the row of bones, permitting them to function as a single mechanical unit. Three INTERMEDIATE LIGAMENTS exist within the wrist. The SCAPHOLUNATE LIGAMENT is a broad collection of fibers that links the SCAPHOID with the LUNATE. The LUNOTRIQUETRAL LIGAMENT is a fibrous continuation of the PALMAR RADIOLUNATE LIGAMENT. Several SCAPHOTRAPEZIAL LIGAMENTS reinforce the articulation between the scaphoid and the trapezium. Two relatively long ligaments are present within the wrist. The PALMAR INTERCARPAL LIGAMENT is firmly attached to the palmar surface of the capitate bone. The ligament bifurcates proximally into 2 fiber groups that form an inverted V shape. The lateral leg of the inverted V is formed by fibers from the capitate to the scaphoid; the medial leg is formed by the fibers between the capitate and triquetrum. A thin ligament, the DORSAL INTERCARPAL LIGAMENT, provides transverse stability to the wrist by binding the scaphoid to the triquetrum.
The MUSCULOCUTANEOUS, RADIAL , MEDIAN and ULNAR nerves provide motor and sensory innervation to the muscles and connective tissues of the elbow, forearm, wrist and hand. Knowledge of the innervation to the muscle, skin and joints is useful clinical information in the treatment of injury to the peripheral nerves or nerve root. The informed clinician can anticipate the extent of the sensory and motor involvement following an acute injury. Therapeutic activities such as splinting, selective strengthening, range of motion exercise, and patient education, can be initiated almost immediately following injury. This proactive approach minimizes the potential for deformity and damage to insensitive skin and joints, thereby limiting amount of permanent disability.
The MUSCULOCUTANEOUS NERVE, formed from C5-C7 nerve roots, innervates the following muscles: BICEPS BRACHII, CORACOBRACHIALIS, and BRACHIALIS. As its name implies, the musculocutaneous nerve innervates muscle, then continues distally as a sensory nerve to the skin, supplying the lateral forearm. The elbow flexors have 3 different sources of peripheral nerve supply: the musculocutaneous nerve to the biceps brachii and brachialis, the radial nerve to the brachioradialis and lateral part of the brachialis, and the median nerve to the pronator teres, which is secondary flexor. Since the elbow flexors have 3 different sources of peripheral nerve supply, injury to the musculocutaneous nerve will not result in complete paralysis of the elbow flexors, although it could result in weakness of the elbow flexion. The bicep brachii which is innervated solely by the musculocutaneous nerve is a primary elbow flexor and at the same time, a strong supinator. In fact, its performance as an elbow flexor is maximal when it is coupled with supination as noted in bringing spoon to the mouth. The brachialis muscle, which is the main elbow flexor, has a dual innervation. The lateral half of the muscles is innervated by the radial nerve while the medial half is innervated by the musculocutaneous nerve. Injury to the musculocutaneous nerve may weaken the brachialis muscle but not totally paralyzed it. The brachioradialis muscle is also one of the primary elbow flexors and it innervated by the radial nerve. It is not affected if the musculocutaneous nerve is injured.
Injury to the musculocutaneous nerve in the axilla (very uncommon in this protected position) is typically inflicted by a penetrating injury (either by a bladed weapon or a missile like the bullet) results in paralysis of the coracobrachialis, biceps brachii and brachialis. Consequently, flexion of the elbow joint and supination of the forearm are greatly weakened but not totally paralyzed. Loss of sensation may occur on the lateral surface of the forearm supplied by the lateral antebrachial cutaneous nerve.
The RADIAL NERVE, formed from C5-T1 nerve roots, is a direct continuation of the posterior cord of the brachial plexus. This large nerve courses within the radial groove of the humerus to innervate the triceps. Just before entering the radial groove it sends nerve branches to the lateral head, medial head, and the long head of triceps. It also sends the Brachial cutaneous nerve which innervates the posterior surface of the arm. The radial nerve emerges laterally at the distal humerus to innervate the muscles that attach on or near the lateral epicondyle. Proximal to the elbow, the radial nerve innervates the brachioradialis, a small lateral part of the brachialis, extensor carpi radialis longus, the anconeus. Distal to the elbow, the radial nerve branches into two- the superficial and deep branches. The superficial branch is purely sensory, supplying the posterior-lateral aspects of the extreme distal forearm and hand, especially concentrated at the dorsal aspect of the first webspace between the thumb and index finger. Such concentration of sensation is known as “AUTONOMOUS ZONE”. The deep branch of the radial nerve contains the remaining motor fibers of the radial nerve. This motor branch supplies the extensor carpi radialis brevis and the supinator muscle. After piercing through the intermuscular tunnel of the supinator muscle, the final section of the radial nerve courses toward the posterior side of the forearm. This terminal branch, often referred to as the POSTERIOR INTEROSSEOUS NERVE, supplies the extensor carpi ulnaris and several muscles of the forearm, which function in extension of the digits. These muscles are: EXTENSOR DIGITORUM COMMUNIS, EXTENSOR DIGITI MINIMI, ABDUCTOR POLLICIS LONGUS, EXTENSOR POLLICIS BREVIS, EXTENSOR POLLICIS LONGUS, and EXTENSOR INDICIS. The extensive muscle innervation of the radial nerve makes the nerve an important neural structure of the upper extremity. Injury of the radial nerve at its proximal part just before it courses through the radial groove results in paralysis of the triceps brachii and the extensor-supinator muscles of the forearm, extensor of the wrist, digits and thumb, and thumb abductors. This is associated with loss of sensation at the posterior aspect of the arm, forearm and the dorsal aspect of the 3 and one half of the lateral digits of the hand. The most common location of the radial nerve injury is at the part where it courses through the radial groove where it becomes vulnerable to middle third humeral shaft fracture. It is also vulnerable during surgical fixation of the humeral fracture in which the nerve becomes accidentally compressed by bone clamps. It is also in danger of being surgically cut if the surgeon opts to approach the humeral fracture at the posterior aspect of the arm. In this scenario, all the muscles distal to injury lose their motor function. The triceps function, however, and the sensation at the posterior aspect of the arm are intact. The patient will exhibit the “WRIST DROP” deformity of the hand. Active supination of the forearm and hand is lost. Active wrist, fingers and thumb extension are lost. Thumb abduction is also lost.
In this slide the radial nerve passes through the triangular space between the long head of triceps and the humerus beneath the teres major muscle. Then the nerve courses diagonally through the radial groove from medial proximally to lateral distally. In the spiral (or radial groove), the nerve lies between the medial and the long heads of triceps. The radial nerve is accompanied by the profunda brachii artery. After crossing the back of the humerus and giving off branches to the lateral head and the lateral part of the medial head of the triceps, the radial nerve pierces the lateral intermuscular septum, entering the anterior compartment and lying the brachioradialis and the brachialis as it crosses the elbow joint. There it supplies the brachioradialis, extensor carpi radialis and the extensor carpi radialis brevis, and the anconeus.
The motor branch of the radial nerve is seen exiting through the supinator muscle. From this point on, the motor branch is name as the POSTERIOR INTEROSSEOUS NERVE.
The MEDIAN NERVE, formed from C6-T1 nerve roots, is a nerve-in-transit at the medial side of the arm and doesn’t give any branch at the this level. It courses toward the elbow to innervate most of the muscles attaching on or near the medial epicondyle. These muscles include wrist flexors and forearm pronators (pronator teres, flexor carpi radialis, and palmaris longus) and the deeper flexor digitorum superficialis. A deep branch of the median nerve, often referred to as the ANTERIOR INTEROSSEOUS NERVE innervates the deep muscles of the forearm: the lateral half of the flexor digitorum profundus, the flexor pollicis longus, and the pronator quadratus. The main part of the median nerve continues distally to cross the wrist through the carpal tunnel, under the cover of the transverse carpal ligament. The nerve then innervates several intrinsic muscles of the thumb and the lateral fingers. These muscles are: ABDUCTOR POLLICIS BREVIS, OPPONENS POLLICIS. FLEXOR POLLICIS BREVIS, and the lateral half of THE LUMBRICALS. The median nerve provides a source of sensory fibers to the lateral thumb, and lateral two and a half fingers. This sensory supply is especially rich and concentrated about the distal ends of the index and middle fingers.
When the median nerve is severed in the elbow region, flexion of the proximal interphalangeal joints (PIP) of digits 1 to 3 is lost; flexion of the PIP joints of the 4th and 5th digits is weakened. Flexion of the distal interphalangeal joints (DIP) of the 4th and 5th digits is not affected because the medial part of the flexor digitorum profundus(FDP), which produces these movements, is supplied by the ULNAR NERVE. There will be lost of flexion of the DIP joints of the 2nd and 3rd digits. The ability of the metacarpophalangeal joints of the 2nd and 3rd digits to flex will not be affected because the digital branches of the median nerve supply the first and 2nd lumbricals. Thus, when the patient attempts to make a fist, digits 2 and 3 remain partially extended (“HAND OF BENEDICTION).
PRONATOR SYNDROME: This nerve entrapment syndrome is caused by compression of the median nerve between the heads of the pronator teres near the elbow. This may be caused by trauma, hypertrophy of muscles, or, the presence of fibrous bands. Patients are first seen clinically with pain and tenderness in the proximal aspect of the anterior forearm. Symptoms often follow activities that involve repeated elbow movements. These are common among weight lifters.
In long standing carpal tunnel syndrome, muscle atrophy involving the thenar muscles and flattening of the thenar eminence are seen.
CLINICAL CORRELATION: CARPAL TUNNEL SYNDROME. This condition is actually a compression neuropathy of the median nerve in the carpal tunnel. The causation of this condition involves several conditions that cause increase in size of the tunnel structures caused by edema (trauma), inflammation (rheumatoid disease); ganglion cyst, amyloid deposits, or diabetic neuropathy. All these conditions may compress the median nerve. The condition may present as gradual numbness of fingers while driving, or, the patient may be awaken by tingling and/or pain in thumb, index and middle fingers.
The ULNAR NERVE, formed from C8-T1 nerve roots, is formed by a direct branch of the medial cord of the brachial plexus. After passing posteriorly to the medial epicondyle, the ulnar nerve innervates the flexor carpi ulnaris and the medial half of the flexor digitorum profundus. The nerve then crosses the wrist external to carpal tunnel and supplies motor innervation to many intrinsic muscles of the hand. These muscles are the ff: PALMARIS BREVIS, ABDUCTOR DIGITI MINIMI, OPPONENS DIGITI MINIMI. It also innervates the 4 dorsal interossei and 4 palmar interossei muscles, and the medial half of the lumbricals The ulnar nerve supplies sensory fibers to the skin on the ulnar side of the hand, including the medial side of the ring finger and entire little finger. This sensory supply is especially concentrated about the little finger and ulnar border of the hand.
More than 27% of nerve lesions of the upper limb affect the ulnar nerve. The ulnar nerve is frequently injured by gunshot wounds, stab wounds, and fractures of the distal end of the humerus, olecranon, or the head of the radius. Ulnar nerve injury commonly occurs where the nerve passes posterior to the medial epicondyle of the humerus. Often the injury occurs when the elbow hits a hard surface, fracturing the epicondyle. The ulnar nerve may be compressed at the elbow during sleep or as an occupational neuritis in workers who rest their elbows on hard surface for long periods.
The ulnar nerve injury may result in extensive motor and sensory loss to the hand with accompanying impaired power of adduction. On flexing the wrist joint, the hand is drawn to the radial side by the FLEXOR CARPI RADIALIS in the absence of the “balance” Provided by the flexor carpi ulnaris. After ulnar nerve injury, patients are likely to have difficulty making a fist due to paralysis of most intrinsic hand muscles. In addition, their metacarpophalangeal joints become hyperextended, and they cannot flex their 4th and 5th digits at the distal interphalangeal joint when they try to make a fist; nor can they extend their interphalangeal joints when they try to straighten their fingers. This results in a characteristic CLAWHAND appearance of the hand.
GUYON’S CANAL SYNDROME: Compression of the ulnar nerve at the wrist where it passes between the pisiform and the hook of the hamate. The depression between these bones is converted by the pisohamate ligament into an osseofibrous tunnel(GUYON’S canal). Compression of the ulnar nerve in this canal may result in hyposthesia in the medial one and a half digits and weakness of the intrinsic muscles of the hand. CYCLIST’S PALSY (or, HANDLEBAR NEUROPATHY): This condition is common among bicycle riders who ride long distances with their hands in an extended position against the hand grips. This put pressure on the hook of the hamate and compromises the ulnar nerve. Because of this, this type of ulnar nerve compression is called handlebar neuropathy. This injury results in sensory loss on the medial side of the hand and weakness of the intrinsic hand muscles.
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION A. STUDY THE FOLLOWING BONES 1. SCAPULA -Distinguish the anterior vs. posterior surface -know the acromial process, scapular spine, coracoid process -know the muscles originating from the scapula; muscles inserting to the scapula 2. HUMERUS -know the different tubercles of the proximal part of the humerus and the muscles inserting to these 3. CLAVICLE -Distinguish anterior border vs. posterior border -Distinguish the medial end vs. the lateral end
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION B. DISSECT AND OBSERVE THE FF. MUSCLES 1. Deltoid muscle 2. “SIT” muscles: Supraspinatus, Infraspinatus, Teres Minor 3. Subscapularis muscle 4. Teres major C. Locate the following spaces including their boundaries and, the important structures that pass through these spaces. 1. Quadrangular space 2. 2 triangular spaces
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION REGIONAL ANATOMY OF THE POSTERIOR ASPECT OF THE SHOULDER Two muscular sleeves 1. Posterior part of the deltoid- outer sleeve 2. Two muscles of rotator cuff- inner sleeve -Infraspinatus -Teres minor
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION Posterior aspect showing the posterior deltoid muscle on the left shoulder. With the trapezius and the posterior deltoid muscle taken, the supraspinatus, infraspinatus and teres minor muscles are exposed.
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION THE AXILLARY NERVE -branch of posterior cord of the brachial plexus The QUADRANGULAR SPACE: POSTERIOR VIEW: -boundaries: superiorly: lower border of the teres minor laterally: surgical neck of the humerus medially: long head of triceps inferiorly: upper border of the teres major ANTERIOR VIEW: superiorly: subscapularis laterally: surgical neck of the humerus medially: long head of biceps inferiorly: upper border of the teres major
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION HILTON’S LAW: -Axillary nerve is an example of a nerve following the Hilton’s law -The law states: that the motor nerve to a muscle tends to send a branch to the joint that the muscle moves and another branch to the skin over the joint.
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION DELTOID MUSCLE -responsible for the roundness of the shoulder -outer shoulder muscle sleeve -origin: Anterior border and upper surface of clavicle -Lateral margin, upper surface of the acromiom -lower border of the spine of the scapula -Insertion: deltoid tubercle of the humerus -Innervation: Axillary nerve -Action: Abducts arm Anterior fibers: flex and rotate arm medially Posterior fibers: extends and rotate arm laterally
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION ANTERIOR PART OF THE DELTOID DISSECTED OFF THE CLAVICLE POSTERIOR PART OF THE DELTOID MUSCLE DISSECTED FROM ITS ORIGIN AT THE SPINOUS PROCESS OF THE SCAPULA.
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION TRIANGULAR SPACES 1. Triangular space containing the radial nerve -boundaries: superiorly: lower border of teres major laterally: shaft of the humerus medially: long head of triceps 2. Triangular space containing the circumflex scapular vessels -boundaries: superiorly: lower border of teres minor laterally: long head of triceps medially: upper border of teres major
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION POSTERIOR VIEW OF THE QUADRANGULAR SPACE SHOWING THE AXILLARY NERVE
CLINICAL ANATOMY: THE SHOULDER ANTERIOR VIEW OF THE QUADRANGULAR SPACE
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION SUPRASPINATUS MUSCLE SUPRASPINATUS MUSCLE AS A COMPONENT OF THE ROTATOR CUFF OF THE SHOULDER SUPRASPINATUS MUSCLE Origin: medial ¾ of supraspinous fossa Insertion: Upper facet of greater tuberosity of humerus Action: Initiates abduction of shoulder Nerve supply: Suprascapular nerve
CLINICAL ANATOMY: THE SHOULDER
CLINICAL ANATOMY: THE SHOULDER
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION Continue the dissection of the Deltoid muscle anteriorly. Take note of the ff: 1.Acromioclavicular joint -What are the structures that go into articulation of this joint? -What are the structures that pass underneath the A-C joint? 2. ligaments that stabilize the A-C joint. a. coracoclavicular ligament a1. Trapezoid ligament a2. Conoid ligament b. Acromioclavicular ligaments b1. superior acromioclavicular ligament b2. inferior acromioclavicular ligament. c. Coracoacromial ligament
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION Dissect the skin over the anterior shoulder and take the skin incision medially along the anterior base of the neck towards the sternoclavicular joint from which the incision is directed caudally passing the center of the sternum. Take note of the ff: 1. STERNOCLAVICULAR JOINT A. Give the structures that go into formation of the sternoclavicular joint 1. What type of joint is the sternoclavicular joint B. Take note of the following structures: B1. sternoclavicular joint fibrous capsule B2. Anterior and posterior sternoclavicular ligaments B3. Costoclavicular ligament B4. Interclavicular ligament
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION Dissect the skin out starting from the sternoclavicular joint to expose the following structures: -Pectoralis major muscles -Anterior part of the deltoid muscles 1. Take note of the origin of the anterior part of the deltoid muscle at the anterior border of the lateral third of the clavicle. 2. Locate the deltopectoral fascial interval and follow the insertion of the deltoid muscle to the deltoid tubercle of the humerus.
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION Dissect the origin of the anterior part of the deltoid off the anterior border of the lateral one third of the clavicle. Observe the following structures: a. tendon inserting into the lesser tubercle of the proximal humerus b. The glenohumeral joint enclosed by its joint capsule c. Palpate the coracoid process of the scapula and the tendons of the muscles inserting to it. d. Insertion of the pectoralis major muscle e. The tendon of the long head of the biceps as it enters the bicepital groove.
CLINICAL ANATOMY: THE SHOULDER ANTERIOR PART OF THE DELTOID POSTERIOR PART OF THE DELTOID
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER
CLINICAL ANATOMY: THE SHOULDER ANATOMY DISSECTION
CLINICAL ANATOMY: THE SHOULDER
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY BY DANILO V. OLEGARIO MD, FPOA SILLIMAN UNIVERSITY MEDICAL SCHOOL
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY I. INTRODUCTION A. Basic Principles 1. Primitive Position a. Primitive surfaces: -primitive ventral surface: corresponds to the anterior or flexor side -primitive dorsal surface corresponds to the posterior or extensor side b. Axial borders: -cephalad preaxial border -caudal postaxial border
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY INTRODUCTION TO THE UPPER EXTREMITY 2. Early terrestrial adaptation -from fin-like position to approximation of amphibian/reptilian position -elbow flexed to 90 degrees -wrist extension to 90 degrees 3. Late terrestrial adaptation: -in mammals and humans: -amphibian/reptilian brachium rotated caudally -upper extremity brought down alongside the lateral body wall - flexor surface facing anteriorly
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY Late terrestrial adaptations in human a. Manipulation: the Hand 1. upper extremity freed from its original role of support/weight bearing and propulsion 2. development of intrinsic mobility -function of the human extremity: -manipulation of the environment b. Grasp: characteristic PREHENSION, two-point grasp between the thumb and index finger c. Sophisticated sensory organ d. strength
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY B. Basic Organization -free portion: arm, forearm, wrist and hand -embedded portion: pectoral girdle 1. Bony support 2. Muscular support a. Dynamic stability b. Mobility
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE PECTORAL GIRDLE (shoulder) ANTERIOR VIEW THE PECTORAL GIRDLE (shoulder) POSTERIOR VIEW
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY Muscular attachment of the pectoral girdle Muscular attachment of the scapula to the thorax
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY The muscles that support the upper extremity anteriorly The muscles that support the upper extremity posteriorly
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY C. Regions of the Upper Extremity 1. The pectoral girdle or shoulder consists of two bones, the clavicle and the scapula 2. The arm or brachium contains one bone, the humerus. 3. The forearm or antebrachium contains two bones, the radius and the ulna 4. The wrist or carpus contains 7 carpal bones in two rows and a sesamoid bone 5. The hand contains five metacarpals and 14 phalanges
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY BONES OF THE PECTORAL GIRDLE A. The clavicle -shape: S-shaped strut between the sternum anteriorly and the scapula posteriorly -articulations: with the sternum at the sternoclavicular joint -with the scapula through the acromioclavicular joint -first bone to begin to ossify starting at the 5th week of fetal life; the last bone to complete ossification at the 21 year. -the only long bone formed by intermembranous ossification
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY The clavicle The muscle and ligamentous attachments to the clavicle
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY The sternoclavicular articulation The acromioclavicular articulation
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY The clavicle as a strut or rigid support The clavicle as a rigid shield protecting the neurovascular structures
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY CLINICAL CORRELATION 1. Fracture of the clavicle - one of the most commonly fractured bones in individuals younger than middle age - the most common obstetrical fracture a. Mechanism of injury: fall on an outstretched arm. b. Fracture fragment displacement: -proximal half of fracture fragment: upward -distal half: downward c. Complication: injury to the neurovascular structures
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY B. THE SCAPULA (SHOULDER BLADE) 1.Description: Inverted triangular flat bone -surfaces -borders -inferior apex. - other structures 2. Location: lies on the posterolateral aspect of the thorax, overlying the 2nd to the 7th ribs. 3. Articulations: with the clavicle at the acromioclavicular joint -with the humerus at the glenohumeral joint
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE SCAPULA LATERAL VIEW OF THE SCAPULA STRUCTURES CHARACTERISTICS OF THE SCAPULA Spine of the scapula Acromium process Coracoid process Glenoid fossa -glenoid labrum -supraglenoid and infraglenoid tubercles
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY CORONAL SECTION OF THE GLENOHUMERAL JOINT LATERAL VIEW OF THE GLENOHUMERAL JOINT
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ARTICULATIONS OF THE SHOULDER GIRDLE C. GLENOHUMERAL(SCAPULOHUMERAL) JOINT 1. Structure: -articulation between the glenoid fossa of the scapula and the head of the humerus - shallow ball and socket joint -glenoid labrum 2. Movement -3 degrees of freedom -flexion/extension -abduction/adduction -internal and external rotation -circumduction
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE GLENOHUMERAL JOINT LATERAL VIEW OF THE GLENOID WITH THE LIGAMENTOUS STRUCTURES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY The ligamentous support of the glenohumeral joint The capsular and ligamentous support of the glenohumeral joint THE GLENOHUMERAL JOINT 3. Ligamentous support: ligamentous structures provide STATIC STABILITY a. Superior, middle and inferior glenohumeral ligaments-run from the glenoid lip to the anatomic neck of the humerus b. Coracohumeral ligament-between the coracoid process and the humerus supports the dead weight of the free portion of the upper extremity
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY The ligamentous support of the glenohumeral joint The capsular and ligamentous structures of the glenohumeral joint THE GLENOHUMERAL JOINT -Ligamentous supports c. Coracoacromial ligament -together with the acromiom process, this ligament forms the CORACOACROMIAL ARCH -this arch buttresses the superior aspect of the glenohumeral joint. -coracoacromial ligament: transmit tensile force
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ROTATOR (MUSCULOTENDINOUS) CUFF
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE LONG HEAD OF BICEPS BRACHII MUSCLES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY D. DYNAMIC STABILITY -Provided by the action of the muscles -Rotator (musculotendinous) cuff -Subscapularis -Supraspinatus -Infraspinatus -Teres Minor -The tendon of the long head of the biceps brachii muscles
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY CLINICAL CORRELATION 2. Shoulder Dislocation -humeral head out of the glenoid fossa -factors predisposing the shoulder joint to dislocation a. Extreme mobility of the glenohumeral joint b. Shallowness of the glenoid fossa Types: 1. Anterior Dislocation -MOST COMMON form of shoulder dislocation -humeral head comes to lie inferior to the coracoid process -Anterior capsule might be stretched and avulse the glenoid labrum - may be associated with AXILLARY NERVE INJURY 2. Posterior Dislocation
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY NORMAL AXILLARY VIEW OF THE SHOULDER STRUCTURES SEEN IN NORMAL AXILLARY VIEW OF THE SHOULDER NORMAL AXILLARY VIEW OF THE SHOULDER -shows clearly the relationship of the humeral head to the glenoid fossa -the humeral head is seated on the glenoid fossa like a golf ball seated on a tee. -the coracoid process which located anteriorly is shown clearly in this view. - the scapular spine which is located posteriorly is also shown clearly in this view.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY NORMAL ANTERO-POSTERIOR XRAY VIEW OF THE LEFT SHOULDER A-P XRAY VIEW OF A DISLOCATED LEFT SHOULDER
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY CLINICAL CORRELATION 1. Acromio-clavicular subluxation: Very common among football players. -etiology(the cause): usually by traumatic downward displacement of the clavicle resulting in rupture of the capsule of the A-C joint. -other stabilizing ligaments: intact. 1. Acromio-clavicular(A-C) joint separation - upward displacement of the clavicle - the joint capsule is torn; other stabilizing ligaments are also rupture
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY SUPERIOR VIEW OF THE PECTORAL GIRDLE ANTERIOR VIEW OF THE PECTORAL GIRDLE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY BURSAE OF THE SHOULDER JOINTS THE SUBDELTOID AND SUBACROMIAL BURSAE F. BURSAE 1. The subacromial bursa -separates the acromiom process from the underlying supraspinatus muscle 2. Subdeltoid bursa separates the deltoid muscle from the humeral head and the insertion of the rotator cuff
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY F. CLINICAL CORRELATION 1. Inflammatory conditions a. Subacromial bursitis: -inflammation of the subacromial bursa - could be a part of diabetic syndrome b. tendonitis: could involve the supraspinatus tendon, long head of bicep brachii tendon, subscapularis tendon
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY MUSCLE FUNCTION AT THE SHOULDER JOINT A. Movement of the Pectoral Girdle 1. Organization of muscles acting on the pectoral girdle -shoulder movement occurs at: a. sternoclavicular joint b. acromioclavicular joint c. scapulothoracic joint a. Major posterior muscles: arranged in 2 layers 1. Superficial muscles: upper and lower portions of the trapezius muscles 2. Deep muscles: levator scapulae and the rhomboids(major and minor)
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY POSTERIOR AXIOAPPENDICULAR AND SCAPULOHUMERAL MUSCLES -Superficial and intermediate groups of extrinsic back muscles -attach the superior appendicular skeleton ( upper limb) to the axial skeleton (trunk) THREE GROUPS OF POSTERIOR SHOULDER MUSCLES: 1. Superficial axioappendicular (extrinsic shoulder) muscles: trapezius and latissimus dorsi 2. Deep posterior axioappendicular (extrinsic shoulder ) muscles: levator scapulae and rhomboids 3. Scapulohumeral(Intrinsic shoulder) muscles: deltoid, teres major and the 4 rotator cuff muscles
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY Posterior muscles acting on the shoulder girdle Organization of posterior muscles acting on the shoulder girdle A. Superficial layer of Posterior muscle groups: 1. Trapezius -Upper Portion -Lower Portion B. Deep Layer of Posterior muscle groups: 1. Levator Scapulae 2. Rhomboid minor 3. Rhomboid major
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE TRAPEZIUS MUSCLE POSTERIOR MUSCLES OF THE BACK SUPERFICIAL POSTERIOR AXIOAPPENDICULAR MUSCLES a. TRAPEZIUS -provides direct attachment of the pectoral girdle to the trunk. -covers the posterior aspect of the trunk and the superior half of the trunk. -attaches the pectoral girdle to the cranium and vertebral column.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE TRAPEZIUS MUSCLE PARTS OF THE TRAPEZIUS PARTS OF THE TRAPEZIUS MUSCLE A. superior or descending part: elevates scapula B. middle part: retracts the scapula C. ascending part: depresses the scapula and lowers the shoulder
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY LATISSIMUS DORSI Latissimus dorsi -wide area of back covered - inserted on the proximal humerus -acts directly on the humerus and indirectly on the scapulothoracic (shoulder girdle) -with limb fixed, the latissimus dorsi raises the trunk -with trunk fixed, the latissimus dorsi moves the limb as in paddling the canoe or chopping the wood. POSTERIOR AXIOAPPENDICULAR MUSCLES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY Muscles Acting on the Pectoral Girdle b. Major anterior muscles -arranged in 2 layers 1. Superficial layer: Pectoralis minor and the sternocleidomastoid muscles 2. Deep layer: Serratus anterior and the subclavius muscles 2. Group Actions a. Elevation/depression: occurs through an anteroposterior axis through the sternoclavicular joint with a resultant vertical gliding at the SCAPULOTHORACIC joint 1. Elevation: Prime elevators- cervical portion of the trapezius, the levator scapulae, rhomboid major and rhomboid minor
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ANTERIOR GROUP OF MUSCLES ACTING ON THE SHOULDER GIRDLE STERNOCLEIDOMASTOID MUSCLE STERNOCLEIDOMASTOID MUSCLE -Origin: a.Sternal head: from the anterior surface of manubrium sterni b. clavicular head: upper surface of the medial third of the clavicle -Insertion: Mastoid process of the temporal bone and the lateral half of the superior nuchal line of occipital bone -Innervation: Accessory ( CN XI) and ventral(anterior) ramus of second cervical nerve directly.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY MAJOR ANTERIOR MUSCLES ACTING ON THE PECTORAL GIRDLE. SERRATUS ANTERIOR MUSCLE SERRATUS ANTERIOR MUSCLE Origin: Outer surface of ribs 1-9 Insertion: Vertebral border of the scapula Action: Protracts (abducts) and rotates scapula upward Innervation: Long Thoracic Nerve
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ANTERIOR MUSCLE GROUP ACTING ON THE SHOULDER GIRDLE PECTORALIS MINOR MUSCLE PECTORALIS MINOR MUSCLE Origin: Outer surface of 3rd to 5th ribs. Insertion: Coracoid process of the scapula Innervation: Medial Pectoral Nerve Action: Depression and Protraction of the scapula -also elevates ribs if shoulder is fixed.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ANTERIOR MUSCLE GROUPS ACTING ON THE SHOULDER GIRDLE THE SUBCLAVIUS MUSCLE THE SUBCLAVIUS MUSCLE Origin: Junction of the first rib and its costal cartilage Insertion: Inferior surface of the clavicle. Innervation: Nerve to Subclavius Action: depresses the lateral end of clavicle, draws it toward the sternum and steadies clavicle during shoulder movement. Paralysis of the muscle produces no demonstrable effect.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE SCAPULOTHORACIC JOINT THE SCAPULOTHORACIC JOINT BETWEEN THE SUBSCAPULARIS MUSCLE AND THE SERRATUS ANTERIOR MUSCLE E. SCAPULOTHORACIC JOINT -A conceptualized pseudojoint -lies between the Subscapularis muscle and the Serratus Anterior muscle. -its movement pairs actually occur at the sternoclavicular and acromioclavicular joints -Degrees of Freedom 1. Protraction/Retraction 2. Elevation/Depression 3. Rotation -Support: 1. Clavicle 2. Muscles: Rhomboids, Serratus anterior, Levator Scapulae, Trapezius
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY DYNAMIC SUPPORT OF THE SCAPULOTHORACIC JOINT MUSCLES SUPPORTING THE SCAPULOTHORACIC JOINT DYNAMIC SUPPORT OF THE SCAPULOTHORACIC JOINT Muscles located at the back -Rhomboids -Levator Scapula -Trapezius
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY PARTS OF THE HUMERUS ANTERIOR VIEW OF THE HUMERUS THE HUMERUS Parts of the humerus: A. Proximal Humerus -Humeral Head -Anatomic Neck -surgical Neck -The Lesser Tuberosity -The Greater Tuberosity -Intertubercular Groove - B. SHAFT OF THE HUMERUS - Deltoid tuberosity -Radial Groove -Medial and Lateral Epicondyle
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY PARTS OF THE HUMERUS Anterior and Posterior Views of the Distal Part of the Humerus PARTS OF THE HUMERUS C. Distal Humerus -Condyle of the humerus a. Trochlea b. capitulum c. Olecranon d. Coronoid Fossa e. Radial Fossa
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE HUMERUS CLINICAL CORRELATION - Fractures of the humerus -fractures of the surgical neck: common in the elderly people with OSTEOPOROSIS -Fractures of the humeral shaft: - middle third: associated radial nerve injury resulting in WRIST DROP deformity or position of the hand. -distal third: common in children -associated with neurovascular injury due to the displacement of the end of the proximal fragment anteriorly -associated with COMPARTMENT SYNDROME
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ANTEROPOSTERIOR VIEW OF THE ELBOW JOINT LATERAL VIEW OF THE ELBOW SHOWING THE SUPRACONDYLAR FRACTURE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ARTICULATIONS OF THE SHOULDER GIRDLE B. THE ACROMIOCLAVICULAR JOINT 1. STRUCTURE -articulation: distal end of clavicle with the acromial process of the scapula 2. MOVEMENT -sliding - 2 degrees of freedom 3. SUPPORT -Coracoclavicular ligament -Conoid ligament -Trapezoid ligament -Acromioclavicular ligament
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY DISPLACED SUPRACONDYLAR FRACTURE OF THE DISTAL HUMERUS LATERAL VIEW OF THE ELBOW SHOWING POSTERIOR DISPLACEMENT OF THE DISTAL SUPRACONDYLAR FRAGMENT
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW AND FOREARM COMPLEX
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE HUMEROULNAR AND HUMERORADIAL JOINTS OF THE ELBOW THE PROXIMAL AND DISTAL RADIOULNAR JOINTS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW ANTERIOR AND POSTERIOR VIEW OF THE ELBOW TWO MAJOR ARTICULATIONS: 1. Humeroulnar joint 2. Humeroradial joint MOTIONS: -mainly flexion-extension -efficient way to adjust the overall functional length of the upper limb. -important activities of daily living: feeding, reaching, throwing, and personal hygiene.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY NORMAL “Valgus Angle” THE ELBOW THE NORMAL VALGUS ANGLE (or CARRYING ANGLE) OF THE ELBOW Asymmetry of the trochlea- lateral deviation of the ulna relative to the humerus Cubitus valgus- the natural frontal plane angle made by the extended elbow -also known as the “Carrying Angle” which is normally about 15-18 degrees.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY OSTEOLOGY OF THE ELBOW AND FOREARM COMPLEX THE MUSCLE ATTACHMENTS AND OSTEOLOGIC FEATURES OF THE MID-TO-DISTAL HUMERUS Mid-to-Distal Humerus -Muscle attachment - Osteologic features -Trochlea including the groove and medial and lateral lips -Coronoid fossa -Capitulum -Radial fossa -Medial and lateral supracondylar ridges -Olecranon fossa
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ANTERIOR VIEW OF THE DISTAL END OF THE HUMERUS INFERIOR VIEW OF THE ARTICULAR SURFACE OF THE DISTAL HUMERUS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW AND FOREARM COMPLEX: THE ULNA THE PROXIMAL PART OF THE ULNA (lateral view) OSTEOLOGIC FEATURES OF THE ULNA -Olecranon process -Coronoid process -Trochlear notch and Longitudinal crest - Radial Notch -Supinator crest -Tuberosity of the ulna -Ulnar head -Styloid process
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW AND FOREARM COMPLEX: THE RADIUS THE RADIUS-ULNA IN ARTICULATION OSTEOLOGIC FEATURES OF THE RADIUS -Radial head -Fovea -Bicipital tuberosity -Ulnar notch -Styloid process
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW JOINT ANTERIOR VIEW OF THE RIGHT ELBOW SHOWING THE CAPSULE AND THE COLLATERAL LIGAMENTS PERIARTICULAR CONNECTIVE TISSUE 1. Articular capsule 2. Synovial membrane 3. Collateral ligaments a. Medial collateral ligaments 1a. Bundles: -anterior fibers -posterior fibers -transverse fibers b. Lateral collateral ligaments -radial collateral ligament -ulnar collateral ligament
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY SUMMARY ON THE ELBOW LIGAMENTS AND MOTIONS THAT INCREASE TENSION Medial collateral ligament Valgus (anterior fibers) Extension and to a lesser extent flexion - Medial Collateral ligament Valgus (Posterior fibers) Flexion - Lateral Collateral ligament (radial collateral Component) Varus - Lateral Collateral ligament (lateral (ulnar) collateral Varus, Flexion component) - Annular ligament Distraction of the radius
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY Valgus-directed force applied to the elbow during fall on outstretched upper extremity
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY FUNCTIONAL CONSIDERATIONS OF FLEXION AND EXTENSION OF THE ELBOW Important physiologic functions of elbow flexion -activities: pulling, lifting, feeding and grooming -Normal activities of daily living: 30 degrees to 130 degrees of flexion -loss of extremes of motion of elbow: minimal functional impairment -Important physiologic functions of elbow extension: needed in activities like throwing, pushing and reaching.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE HUMEROULNAR JOINT SAGITTAL VIEW OF THE HUMEROULNAR JOINT Arthrokinematics at the humeroulnar joint -limit of motion: predominantly sagittal plane (i.e., flexion-extension) -articular coverage: -trochlea: 300 degrees -trochlear notch: 180 degrees -Elbow Extension -Elbow flexion
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE HUMERORADIAL JOINT ELBOW FLEXION MECHANISM ARTHROKINEMATICS -Articulating structures fovea of radial head vs. capitulum of the distal humerus. -Extension of the elbow: No physical contact exists -Active flexion: rolling and sliding motion of the fovea on the capitulum
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY JOINTS OF THE FOREARM THE FOREARM JOINTS STRUCTURES THAT BIND THE RADIUS AND ULNA 1. Interosseous membrane 2. Proximal radioulnar joint 3. Distal radioulnar joint
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY SUPINATION AND PRONATION OF THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE DISTAL RADIOULNAR JOINT THE DISTAL RADIOULNAR JOINT WITH THE ULNAR HEAD PULLED OUT.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE PROXIMAL RADIOULNAR JOINT THE ANNULAR LIGAMENT WITH THE RADIAL HEAD TAKEN OUT
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY MUSCLES ACTING ON THE ELBOW Principles: 1. Muscles that attach distal to the ulna -flex or extend the elbow -No ability to pronate or supinate the forearm 2. Muscles that attach distally on the radius -may, in theory, flex or extend the elbow -have a potential to pronate or supinate forearm 3. Muscles that act primarily on the wrist also cross the elbow joint -many wrist muscles have a potential to flex or extend the elbow. This potential is relatively minimal
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ELBOW FLEXORS Primary elbow flexors -Biceps brachii -Brachialis -Brachioradialis -Pronator teres -each of these muscles produces a force that passes anterior to the medial-lateral axis of rotation at the elbow
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW FLEXOR THE BICEPS BRACHII BICEPS BRACHII 1. Two heads a. Long head: b. short head 2. Proximal attachments - long head: supraglenoid tubercle of the scapula -short head: tip of coracoid
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW FLEXORS THE BRACHIALIS MUSCLE BRACHIALIS MUSCLE -deep(posterior) to the biceps brachii -the only pure elbow flexor; produces the greatest flexor force -flexes the elbow and the forearm in all position -origin: distal half of the anterior surface of the humerus -insertion: Coronoid process and tuberosity of ulna. -the “work-horse” of the elbow flexors
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ELBOW FLEXORS THE BRACHIORADIALIS MUSCLE THE BRACHIORADIALIS - the longest of all elbow muscles -located at the extensor compartment; innervated by the radial nerve. -a primary elbow flexor especially during rapid movements against resistance.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ELBOW EXTENSORS Primary elbow extensors -Triceps brachii - Anconeus -all these muscles converge to a common tendon attaching to the olecranon process of the elbow -Triceps brachii: produces majority of the total extension torque at the elbow
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ELBOW EXTENSORS: THE TRICEPS AND THE ANCONEUS THE MEDIAL HEAD OF TRICEPS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY MECHANISM OF ELBOW EXTENSION a. During submaximal efforts of elbow extension: -anconeus: usually the first muscle to initiate and maintain low levels of elbow extension force b. With gradual increase in extension force: - Anconeus + medial head of triceps c. with moderate-to-high levels of extension force demand -Anconeus+ medial head+ lateral head d. with high-to-extreme demand of extension force -anconeus + medial head + lateral head + long head
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY SURFACE ANATOMY OF THE POSTERIOR ARM SURFACE ANATOMY OF THE MEDIAL ARM AND THE CUBITAL FOSSA
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE CUBITAL FOSSA SUPERFICIAL ANATOMY OF THE CUBITAL FOSSA AREA DEFINED: -a shallow triangular depression on the anterior surface of the elbow. -boundaries: superiorly: an imaginary line connecting the medial and lateral epicondyle Medially: pronator teres Laterally: brachioradialis Floor of the cubital fossa: formed by the brachialis and supinator muscles Roof: formed by the continuity of the brachial and the (deep) antebrachial fascia Roof reinforcements: bicipital aponeurosis, subcutaneous tissue and skin
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE CUBITAL FOSSA DEEP DISSECTION OF THE CUBITAL FOSSA WITH ITS CONTENTS. CONTENTS OF CUBITAL FOSSA 1. Terminal part of the brachial artery and commencement of its terminal branches, the radial and ulnar arteries 2.(Deep) accompanying veins of the arteries 3. Biceps brachii tendon 4. Median nerve 5. Radial nerve, dividing into its superficial and the posterior interosseous nerve.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE FOREARM THE RADIUS AND ULNA JOINED BY THE INTEROSSEOUS MEMBRANE THE FOREARM -Lies between the elbow and the wrist -two bones: 1. radius 2. ulna -INTEROSSEOUS MEMBRANE: -binds the radius and ulna FUNCTION OF FOREARM MOVEMENT OCCURRING AT THE ELBOW AND RADIOULNAR JOINTS: 1. Assist the shoulder in application of force 2. control the placement of the hand in space
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY FORCE TRANSMISSION WHILE HOLDING A LOAD
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE INTEROSSEOUS MEMBRANE THE ROLE OF INTEROSSEOUS MEMBRANE IN FORCE TRANSMISSION OF COMPRESSION FORCE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY MUSCLES OF THE FOREARM A. FLEXOR-PRONATOR MUSCLES - occupy the anterior compartment of the forearm - tendons of these muscles pass across the anterior surface of the wrist B. ARRANGEMENT 1. GROUPS: -arranged in 3 layers a. superficial layer: Pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris b. intermediate layer: flexor digitorum superficialis c. deep layer: flexor digitorum profundus, flexor pollicis longus, pronator quadratus 2. 5 superficial and intermediate muscles cross the elbow joint; the 3 deep muscles do not
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ANTERIOR AND POSTERIOR COMPARTMENTS OF THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY SUPERFICIAL GROUP OF FLEXOR –PRONATOR GROUP OF MUSCLES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM Surface projection of the superficial layer of the flexor pronator group of muscles of the forearm
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM Surface projection of the tendons of the forearm muscles at the wrist region
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM SECOND LAYER OF FLEXOR MUSCLE: flexor digitorum superficialis
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM 3rd LAYER OF FLEXOR MUSCLES: flexor digitorum profundus and flexor pollicis longus
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE WRIST FLEXORS THE PRIMARY WRIST FLEXORS PRIMARY WRIST FLEXORS -Flexor carpi radialis -Flexor carpi ulnaris -Palmaris longus: missing in 10% of the population SECONDARY WRIST FLEXORS -Flexor digitorum superficialis -Flexor digitorum profundus -Flexor pollicis longus
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM RADIAL AND ULNAR DEVIATORS RADIAL DEVIATORS OF THE WRIST -Extensor carpi radialis longus -Extensor carpi radialis brevis -Extensor pollicis longus -Extensor pollicis brevis -Flexor carpi radialis -Abductor pollicis longus -Flexor pollicis longus ULNAR DEVIATORS OF THE WRIST -Extensor carpi ulnaris -Flexor carpi ulnaris
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY EXTENSOR MUSCLES OF THE FOREARM -Located at the posterior (extensor-supinator) compartment of the forearm -all are innervated by the branches of the radial nerve. -ORGANIZATION A. 3 functional groups 1. muscles that extend and abduct or adduct the hand at the wrist joints: -extensor carpi radialis longus -extensor carpi radialis brevis -extensor carpi ulnaris
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY EXTENSOR MUSCLES OF THE FOREARM ORGANIZATION: A. 3 functional groups 2. Muscles that extend the medial four digits -extensor digitorum -extensor indicis -extensor digiti minimi 3. Muscles that extend or abducts the thumb -abductor pollicis longus (APL) -extensor pollicis brevis (EPB) -extensor pollicis longus (EPL)
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE FOUR SUPERFICIAL LAYER OF EXTENSOR MUSCLES THE DEEP LAYER OF EXTENSOR MUSCLES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE WRIST EXTENSOR MUSCLES THE PRIMARY WRIST EXTENSORS THE WRIST EXTENSOR MUSCLES 1. Primary wrist extensors -Extensor carpi radialis longus -Extensor carpi radialis brevis -Extensor carpi ulnaris 2. Secondary wrist extensors -Extensor digitorum communis -Extensor indicis -Extensor digiti minimi -Extensor pollicis longus
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE ROLE OF WRIST EXTENSORS IN GRIP MAIN FUNCTION OF THE WRIST EXTENSORS Main function of wrist extensors 1. To position and stabilize the wrist for activities involving fingers 2. Important role in making fist
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE EXTENSOR TENDON COMPARTMENTS CROSS SECTION AT THE LEVEL OF THE DISTAL RADIUS SHOWING THE EXTENSOR TENDON COMPARTMENTS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM ILLUSTRATION OF THE SIX EXTENSOR OSSEOFIBROUS TUNNELS IN RELATION TO THE DORSAL DISTAL RADIUS AND ULNA THE SIX DORSAL OR EXTENSOR COMPARTMENTS 1ST DORSAL OR EXTENSOR TUNNEL: -Abductor pollicis longus -Extensor pollicis brevis 2nd EXTENSOR TUNNEL -Extensor carpi radialis longus (lateral) -Extensor carpi radialis brevis 3rd EXTENSOR TUNNEL -Extensor pollicis longus 4th EXTENSOR TUNNEL -Extensor digitorum communis -Extensor indicis 5th EXTENSOR TUNNEL -Extensor digiti minimi 6th EXTENSOR TUNNEL -Extensor carpi ulnaris
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE EXTENSOR TENDON SHOWING ITS EXPANSION AND ITS CONNECTION THE EXTENSION MECHANISM AT THE LEVEL OF THE FINGERS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE STRUCTURES IN THE ANATOMICAL SNUFF BOX. THE ANATOMICAL SNUFF BOX Radial artery- lies on the floor of the snuff box Radial styloid process- can be palpated proximally Base of the 1st metacarpal can be palpated distally Scaphoid and trapezium- floor of the snuff box. -can be palpated between the radial styloid and the 1st metacarpal
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY SUPINATOR AND PRONATOR MUSCLES Two biomechanical properties for a muscle to become a supinator/pronator muscle: 1. The muscle must have one attachment on the humerus and ulna, and the other on the radius and hand. -brachialis and extensor pollicis brevis, therefore, cannot pronate or supinate the forearm 2. The muscle must have a line of force that intersects of rotation for pronation and supination.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM SUPINATOR MUSCLES THE PRONATOR MUSCLES PRIMARY SUPINATOR MUSCLES -Supinator -Biceps brachii SECONDARY SUPINATOR MUSCLES: -Radial wrist extensors(extensor carpi radialis longus and brevis) -Extensor pollicis longus -Extensor indicis -Brachioradialis PRIMARY PRONATOR MUSCLES -Pronator teres -Pronator quadratus -SECONDARY PRONATOR MUSCLES -Flexor carpi radialis -Palmaris longus
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE MUSCLE ORIENTATION OF THE SUPINATOR MUSCLE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE BICEPS BRACHII AS THE MOST POWERFUL SUPINATOR OF THE FOREARM -Biomechanical Features: 1. Muscle attachment: Proximal attachment: a. Long head- supraglenoid tubercle of the scapula b. short head: coracoid process -distal attachment: radial tuberosity at the medial surface of the proximal radius and fascia of the forearm via the bicipital aponeurosis. .
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM LINE-OF –FORCE OF BICEPS: Medial and perpendicular to the axis of rotation of the radius
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM THE PRIMARY PRONATOR MUSCLES: THE PRONATOR QUADRATUS AND PRONATOR TERES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE FOREARM Vigorous contraction is shown of the right biceps, supinator, and extensor pollicis longus muscles to tighten a screw using a clockwise rotation with a screwdriver. The triceps muscle is activated isometrically to neutralize the strong elbow flexion tendency of the biceps
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE WRIST THE OSTEOLOGIC COMPONENTS OF THE WRIST INTRODUCTION - “spacer” between the forearm and hand -contains 8 small carpal bones -two major articulations: 1. Radiocarpal joint 2. Midcarpal joint Take note: the distal radioulnar joint is functionally not part of the wrist; it belongs to the forearm complex.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST OSTEOLOGIC FEATURES OF THE DISTAL DORSAL FOREARM SKELETAL COMPONENTS OF THE DISTAL FOREARM THE DORSAL ASPECT Dorsal or Lister’s tubercle of the radius -separates the tendons of extensor carpi radialis brevis from the extensor pollicis longus Styloid process of the radius Styloid process of ulna Dorsal articular process of the radius
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST ANTERIOR VIEW OF THE DISTAL RADIUS SHOWING THE ULNAR TILT OF THE DISTAL END OF THE RADIUS MEDIAL VIEW SHOWING THE PALMAR TILT OF THE DISTAL END OF THE RADIUS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST “POSITION OF FUNCTION” OF THE WRIST Range of motion of wrist required for daily activities -45 degrees of sagittal plane motion 5 to 10 degrees of wrist flexion 30 to 35 degrees of wrist extension -25 degrees of frontal plane motion 15 degrees of ulnar deviation 10 degrees of radial deviation
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE CARPAL BONES THE CARPAL BONES PROXIMAL ROW OF CARPAL BONES Scaphoid Lunate Triquetrum Pisiform DISTAL ROW OF CARPAL BONES -Trapezium -Trapezoid -Capitate -Hamate
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE CARPAL BONES CROSS SECTION OF THE WRIST SHOWING THE MORPHOLOGY OF THE SCAPHOID AND LUNATE BONES
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY FRACTURE OF THE SCAPHOID CARPAL BONE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE CARPAL BONES CROSS SECTION AT THE WRIST LEVEL SHOWING THE CONVEX SURFACE OF THE LUNATE AND SCAPHOID
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE CARPAL BONES THE CARPAL BONES: PISIFORM, TRAPEZIUM, TRAPEZOID, HAMATE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY CROSS SECTION OF THE WRIST SHOWING THE CARPAL TUNNEL PALMAR VIEW OF THE WRIST SHOWING THE TRANSVERSE CARPAL LIGAMENT AND THE STRUCTURES DEEP TO IT.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST PRIMARY WRIST JOINTS: THE RADIOCARPAL JOINT THE MIDCARPAL JOINT OF THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST LIGAMENTS OF THE WRIST LIGAMENTS OF THE WRIST EXTRINSIC LIGAMENTS: -Dorsal carpal ligament -Radial collateral ligament -Radial radiocarpal ligaments -radiocapitate -radiolunate -radioscapholunate ULNOCARPAL COMPLEX -Articular disc -Ulnar collateral ligament -Palmar ulnocarpal ligament INTRINSIC LIGAMENTS Short ligaments of the distal row Intermediate Ligaments - Lunotriquetral -scapholunate -scaphotrapezial Long ligaments -palmar intercarpal -lateral leg -medial leg Dorsal intercarpal fibers between the scaphoid and triquetrum
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE DORSAL LIGAMENTS OF THE WRIST DORSAL LIGAMENTS OF THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE PALMAR LIGAMENTS OF THE WRIST THE PALMAR LIGAMENTS OF THE WRIST
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST EXTRINSIC LIGAMENTS OF THE WRIST ULNOCARPAL COMPLEX
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST INTRINSIC LIGAMENTS OF THE WRIST AT THE DORSAL ASPECT INTRINSIC LIGAMENTS OF THE WRIST AT THE PALMAR ASPECT
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY NEUROANATOMY OF THE UPPER EXTREMITY: AN OVERVIEW THE THREE NERVES -Musculocutaneous -Radial -Median -Ulnar
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST THE PATHWAY OF THE MUSCULOCUTANEOUS NERVE SENSORY DISTRIBUTION OF THE MUSCULOCUTANEOUS NERVE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE MUSCULOCUTANEOUS NERVE INNERVATING THE BICEPS BRACHII AND THE BRACHIALIS MUSCLES NEURODEFICITS IN INJURY TO THE MUSCULOCUTANEOUS NERVE MOTOR DEFICITS -Weakness of elbow flexors -complete paralysis of biceps brachii -partial paralysis of the brachialis muscle due to its dual innervation. -pronator teres not affected since it is innervated by the median nerve. SENSORY DEFICITS: NUMBNESS at the lateral aspect of the forearm which is innervated by the lateral antebrachial cutaneous nerve which is a sensory branch of the musculocutaneous nerve.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE GENERAL PATH OF THE RADIAL NERVE SENSORY DISTRIBUTION OF RADIAL NERVE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE RADIAL NERVE IN RADIAL GROOVE
REGIONAL AND CLINICAL ANATOMY THE RADIAL NERVE DIVIDING INTO SENSORY AND MOTOR BRANCH THE MOTOR BRANCH OF THE RADIAL NERVE ENTERING THE SUPINATOR MUSCLE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE RADIAL NERVE EXITING THE SUPINATOR MUSCLE
REGIONAL AND CLINICAL ANATOMY INJURY TO THE RADIAL NERVE SUPERIOR TO THE ORIGIN OF IT BRANCHES TO THE TRICEPS BRACHII -paralysis of triceps, brachialis, supinator, and extensor muscles of the wrist and digits INJURY IN THE RADIAL GROOVE: -triceps not completely paralyzed but only weakened since only the medial head is affected. -muscles of the extensor compartment are all paralyzed. RADIAL NERVE INJURY AT DIFFERENT LEVELS
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY RADIAL NERVE INJURY: THE WRIST DROP THE WRIST DROP DEFORMITY Characteristic clinical sign or radial nerve injury Inability to extend the wrist and digits at the metacarpophalangeal joints. Wrist is flexed due to unopposed or dominance of the flexor muscles and gravity The interphalangeal joints can be extended weakly through the action of the lumbricals and the interossei which are innervated by the median and ulnar nerves.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY PATHWAY OF THE MEDIAN NERVE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY MEDIAN NERVE INJURY AT THE ELBOW REGION FUNCTIONS NOT AFFECTED BY MEDIAN NERVE INJURY AT THE ELBOW LEVEL Motor deficits: 1.Lost of flexion of the proximal interphalangeal joints(PIP) of digits 1to 3; weakened flexion of PIP of 4th and 5th. 2. Lost of flexion of the distal interphalangeal joints of 2nd and 3rd digits Flexion of the DIP joints of the 4th and 5th digits is not affected The ability to flex the metacarpophalangeal joints of the 2nd and 3rd digits will not be affected.
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY INJURY TO THE MEDIAN NERVE IN THE ELBOW REGION PRONATOR SYNDROME -nerve entrapment syndrome caused by compression of the median nerve between the heads of the pronator teres near the elbow -causation: trauma, muscular hypertrophy, or, fibrous bands.
REGIONAL AND CLINICAL ANATOMY THE CUBITAL FOSSA SHOWING THE ANATOMIC RELATIONSHIP BETWEEN THE MEDIAN NERVE AND THE PRONATOR TERES MUSCLE THE PRONATOR TERES IS RETRACTED. THE MEDIAN NERVE AND ITS BRANCHES ARE SHOWN
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST Muscle atrophy involving the thenar muscles in long standing carpal tunnel syndrome. CARPAL TUNNEL SYNDROME: Anatomical basis
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY: THE WRIST Signs and symptoms of Carpal Tunnel Syndrome Signs and symptoms of Carpal Tunnel Syndrome
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY PATHWAY OF THE ULNAR NERVE
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ULNAR NERVE INJURY COMMON PLACES OF INJURY 1. Posterior to the medial epicondyle of the humerus 2. In the cubital tunnel formed by the tendinous arch connecting the humeral and heads of the flexor carpi ulnaris 3. at the wrist 4. in the hand
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY THE ULNAR NERVE AT THE VOLAR ASPECT OF THE WRIST THE ULNAR NERVE IS SHOWN IN THE CANAL OF GUYON
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ULNAR NERVE INJURY MOTOR AND SENSORY LOSS -HAND: 1. Impaired power of finger adduction a. adductor pollicis b. palmar interossei 1-3 2. Difficulty of making a fist due to paralysis of the most intrinsic hand muscles a. adductor pollicis b. flexor digiti minimi brevis c. lumbricals 3-4 d. dorsal and palmar interossei -CLAWHAND APPEARANCE OF THE HAND 3. With wrist flexion, there is radial deviation
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY ULNAR NERVE COMPRESSION SYNDROMES 1. GUYON’S CANAL SYNDROME -Compression of the ulnar at the wrist. 2. CYCLIST’S PALSY (or, HANDLEBAR NEUROPATHY)
REGIONAL AND CLINICAL ANATOMY THE UPPER EXTREMITY
REGIONAL AND CLINICAL ANATOMY