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Unit 9: Joints of the Upper Limb Dissection Instructions: The joints are only to be done on one limb. In this unit, the soft tissues are to be removed to expose the joints. If this is done in a systematic way, an excellent review can be accomplished at the same time. Note the insertion of the pectoralis major muscle on the greater tubercular crest of the humerus and the insertion of the pectoralis minor on the coracoid process of the scapula. Now find the medial and lateral pectoral nerves from the medial and lateral cords of the brachial plexus. Remove the muscles by cutting their insertions. In the axilla, locate the axillary nerve and posterior humeral circumflex vessels. Trace them through the quadrangular space, note the nerve to the teres minor and follow the neurovascular bundle into the deltoid muscle. Remove the deltoid muscle. Trace the thoracodorsal nerve and vessels into the latissimus dorsi muscle, then follow the tendon of the muscle into the intertubercular sulcus. Cut the tendon near its insertion and remove the muscle. The tendon of the long head of the biceps brachii is held in the sulcus by the pectoralis major muscle and the transverse ligament. Find the lower subscapular nerve and trace it to the subscapularis and teres major muscles. Review the origin and insertion of the teres major and then remove the muscle. Locate the upper subscapular nerve and follow it into the subscapularis muscle. The subscapularis, teres major and latissimus dorsi muscles make up the posterior wall of the axilla and they are all innervated by branches off the posterior cord of the brachial plexus. Locate the musculocutaneious nerve from the lateral cord of the brachial plexus and find its branches to the coracobrachialis and biceps brachii muscles. Review the origins and insertion of the biceps brachii muscle. Cut the long head of the biceps brachii where the tendon joins the belly of the muscle. Review the coracobrachialis muscle, then remove it and the short head of the biceps brachii from the coracoid process. Detach the coracobrachialis from the humerus and cut the tendon of insertion of the biceps brachii. Note the course of the radial nerve from the posterior cord of the brachial plexus between the humerus and the long and lateral heads of the triceps brachii muscle to the lateral intermuscular septum of the arm. Detach the long head of the triceps brachii from the infraglenoid tubercle of the scapula and the lateral head from the humerus. Note that the deep brachial vessels travel with the radial nerve in the radial groove of the humerus. Find the two branches of the radial nerve to the medial head of the triceps brachii and note that the proximal branch, the ulnar collateral nerve, is accompanied by the superior ulnar collateral artery and the second branch goes with the middle collateral artery. Follow the latter structures through the medial head of the triceps brachii to the anconeus muscle. Very carefully remove the triceps brachii from the olecranon process of the ulna without damaging the capsule of the elbow joint, which is fused to its deep surface. Note that the plane of the acromioclavicular joint space is nearly in a sagittal plane. Saw through the scapular spine where it becomes the acromion process. Carefully clean the oracoclavicular ligament consisting of conoid and trapezoid parts (Plates 406; 6.43, 6.46). Identify the coracoacromial and coracohumeral ligaments. Unit 9 - 1 Review the subscapularis, supraspinatis, infraspinatis and teres minor muscles forming the rotator cuff of the shoulder joint (Plates 408, 409; 6.45, 6.46, Table 6.5, p. 397). Trace the suprascpular nerve and vessels to the supraspinous muscle. Cut the muscles opposite the neck of the scapula (proximal to the glenoid surface) and follow the suprascapular neurovascular bundle to the infraspinous fossa. Free the muscles from the capsule of the shoulder joint before cutting them from their bony attachments on the humerus. Turn to the back of the shoulder joint and make a vertical incision down the back of the joint capsule so the humerus can be rotated away from the glenoid fossa of the scapula. Note the glenoid labrum. It is a fibrocartilagenous lip which deepens the glenoid fossa. Locate the tendon of the long head of the biceps brachii muscle and follow it to the supraglenoid tubercle. Note that part of the origin is from the glenoid labrum. Now locate the communication between the joint space and the supscapular bursa. Between the biceps tendon and the opening of the bursa is the superior glenohumeral ligament. Bordering the inferior margin of the opening of the subscapular bursa is the middle glenohumeral ligament. Below this and running downward and lateralward is the inferior glenohumeral ligament (Plates 406; 6.41 - 6.45). Locate the radial nerve above the elbow and review the nerves to the extensor muscles of the forearm. The brachioradialis and extensor carpi radialis longus are innervated from the main trunk, the extensor carpi radialis brevis and supinator from the deep branch and the rest of the extensors after the nerve exits the supinator. Remove the extensor muscles that attach to the lateral epicondyle and supracondylar ridge of the humerus after the insertions have been reviewed. Note the relationship between the median nerve and the brachial artery. The nerve has no branches until it reaches the cubital fossa. The artery has many branches, most of which are unnamed muscular branches. Trace the ulnar nerve through the arm, behind the medial epicondyle of the humerus and between the heads of the flexor carpi ulnaris muscle. Locate its branch to this muscle and to the flexor digitorum profundis. Review the origins and insertions of the flexor muscles of the forearm, then remove those that arise from the medial epicondyle of the humerus. Identify the end of the brachial artery, the radial and ulnar arteries and the common interosseous artery. Now find the radial recurrent, interosseious recurrent and anterior and posterior ulnar recurrent arteries. Carefully remove the brachialis from the anterior surface of the elbow joint (the capsule is very thin and fused to the muscle) after reviewing its origin and insertion. The elbow joint is formed by the humerus radius and ulna (Plates 421; 6.52, 6.54 - 6.57). Within the elbow joint is the proximal radioulnar joint. The proximal end of the had of the radius articulates with the capitulum of the humerus while the circumference of the head of the radius articulates with the radial notch of the ulna. The trochlear fossa of the ulna articulates with the trochlea of the humerus. The main stability of the joint is maintained by this trochlea-trochlear fossa relationship. On the medial side of the elbow joint, clean the ulnar collateral ligament and identify the anterior, posterior and oblique parts. Clean the radial collateral ligament on the lateral side of the elbow joint. Notice that it attaches inferiorly to the annular ligament. This ligament attaches to the ulna and circles the neck and lower part of the head of the radius. The anterior and posterior part of the elbow joint capsule is weak. Open the elbow joint by making a horizontal incision through the front of the joint capsule at the level of the radial head-capitulum atriculation. Alternately pronate and supinate the hand and watch for movement of the annular ligament. It should be noted that the annular ligament does not move, but the capsule distal to the annular ligament is loose and allows for the movement. Note that the tissue between Unit 9 - 2 the radius and ulna below the annular ligament also is loose. That portion of the capsule is known as the quadrate ligament. Find the insertion of the flexor carpi ulnaris on the pisiform bone, then cut the tendon proximal to the bone. Review the insertions of the flexor pollicis longus, flexor digitorum superficialis and profundis and detach them. Locate the flexor carpiradialis insertion and then cut its tendon. Review the anatomy of the median and ulnar nerves in the hand and the superficial and deep palmar arterial arches. Review the muscles of the hand. Review the extensor retinaculum, identify the tendons passing under it and trace them to their insertions. Review the blood supply to the dorsal aspect of the forearm and hand. Now, remove the muscles that cross the wrist and hand joints, but not the metacarpophalangeal and interphalangeal joints. Clean the interosseous ligament between the radius and ulna (Plate 422; 6.58). This makes up the middle radioulnar articulation. It is a syndesmosis, a fibrous joint. The distal radioulnar joint is a separate synovial joint between the head of the ulna and the ulnar notch of the radius (Plates 422, 438; 6.85 -6.89). Alternately supinate and pronate the hand and note the movement at the distal radioulnar joint. At the distal end of the ulna is a fibrocartilagenous disk which separates the ulna from the carpal bones. Remove the areolar tissue covering the wrist joint and identify the dorsal and palmar radiocarpal ligaments (Plates 437, 438; 6.85, 6.86) Note that they come from the distal end of the radius and pass distally and medialward as they cross the wrist joint. On the sides of the joint are the radial and ulnar collateral ligaments of the wrist. The pisiform bone articulates with the triquetral by a plane synovial joint. The other seven carpal bones articulate with each other through the mid-carpal joint (Plates 438; 6.85, 6.89). This is a single complex synovial joint. Distally the carpal bones articulate with the metacarpal bones through three joint cavities. The first metacarpal bone forms a saddle joint with the trapezium bone. The second and third metacarpals and the third and fourth metacarpals have synovial joints with the adjacent carpal bones. The metacarpophalangeal joints (Plates 441; 6.89) are condylar joints except for the first one, which is a hinge joint. They all have radial and ulnar collateral ligaments. The palmar part of the capsules is very tough and is connected by the deep transverse metacarpal ligament. The dorsal aspect of the joints is formed primarily by the extensor tendon expansion (hood). The interphalangeal joints are hinge joints and their capsules are similar to those of the metacarpophalangeal joints (Plates 44; 6.90). Unit 9 - 3 Be sure to identify all of the following: acromioclavicular joint coracoclavicular ligament (conoid & trapezoid) coracoacromial ligament coracohumeral ligament rotator cuff of shoulder joint subscapularis muscle supraspinatus muscle infraspinatus muscle teres minor muscle glenoid fossa glenoid labrum tendon of long head of biceps brachii muscle superior glenohumeral ligament middle glenohumeral ligament inferior glenohumeral ligament ulnar collateral ligament (elbow) radial collateral ligament (elbow) annular ligament quadrate ligament interosseous ligament dorsal radiocarpal ligament palmar radiocarpal ligament radial collateral ligament (wrist) ulnar collateral ligament (wrist) Unit 9 - 4