Wrist Joint (Radiocarpal Joint)-Movements-Important Relations-Wrist Joint Injuries-Falls on the Outstretched Hand-

Wrist Joint (Radiocarpal Joint)

■■ Articulation: Between the distal end of the radius and the articular disc above and the scaphoid, lunate, and triquetral bones below. The proximal articular surface forms an ellipsoid concave surface, which is adapted to the distal ellipsoid convex surface.

■■ Type: Synovial ellipsoid joint

■■ Capsule: The capsule encloses the joint and is attached above to the distal ends of the radius and ulna and below to the proximal row of carpal bones.

■■ Ligaments: Anterior and posterior ligaments strengthen the capsule. The medial ligament is attached to the styloid process of the ulna and to the triquetral bone. The lateral ligament is attached to the styloid process of the radius and to the scaphoid bone.

■■ Synovial membrane: This lines the capsule and is attached to the margins of the articular surfaces. The joint cavity does not communicate with that of the distal radioulnar joint or with the joint cavities of the intercarpal joints.

■■ Nerve supply: Anterior interosseous nerve and the deep branch of the radial nerve

Movements

The following movements are possible: flexion, extension, abduction, adduction, and circumduction. Rotation is not possible because the articular surfaces are ellipsoid shaped.

The lack of rotation is compensated for by the movements of pronation and supination of the forearm.

Flexion is performed by the flexor carpi radialis, the flexor carpi ulnaris, and the palmaris longus. These muscles are assisted by the flexor digitorum superficialis, the flexor digitorum profundus, and the flexor pollicis longus.

Extension is performed by the extensor carpi radialis longus, the extensor carpi radialis brevis, and the extensor carpi ulnaris. These muscles are assisted by the extensor digitorum, the extensor indicis, the extensor digiti minimi, and the extensor pollicis longus.

Abduction is performed by the flexor carpi radialis and the extensor carpi radialis longus and brevis. These muscles are assisted by the abductor pollicis longus and extensor pollicis longus and brevis.

Adduction is performed by the flexor and extensor carpi ulnaris.

Important Relations

■■ Anteriorly: The tendons of the flexor digitorum profundus and superficialis, the flexor pollicis longus, the flexor carpi radialis, the flexor carpi ulnaris, and the median and ulnar nerves

■■ Posteriorly: The tendons of the extensor carpi ulnaris, the extensor digiti minimi, the extensor digitorum, the extensor indicis, the extensor carpi radialis longus and brevis, the extensor pollicis longus and brevis, and the abductor pollicis longus

■■ Medially: The posterior cutaneous branch of the ulnar nerve

■■ Laterally: The radial artery

Wrist Joint Injuries

The wrist joint is essentially a synovial joint between the distal end of the radius and the proximal row of carpal bones. The head of the ulna is separated from the carpal bones by the strong triangular fibrocartilaginous ligament, which separates the wrist joint from the distal radioulnar joint. The joint is stabilized by the strong medial and lateral ligaments.

Because the styloid process of the radius is longer than that of the ulna, abduction of the wrist joint is less extensive than adduction. In flexion–extension movements, the hand can be flexed about 80° but extended to only about 45°. The range of flexion is increased by movement at the midcarpal joint.

A fall on the outstretched hand can strain the anterior ligament of the wrist joint, producing synovial effusion, joint pain, and limitation of movement. These symptoms and signs must not be confused with those produced by a fractured scaphoid or dislocation of the lunate bone, which are similar.

Falls on the Outstretched Hand

In falls on the outstretched hand, forces are transmitted from the scaphoid to the distal end of the radius, from the radius across the interosseous membrane to the ulna, and from the ulna to the humerus; thence, through the glenoid fossa of the scapula to the coracoclavicular ligament and the clavicle; and finally, to the sternum. If the forces are excessive, different parts of the upper limb give way under the strain. The area affected seems to be related to age. In a young child, for example, there may be a posterior displacement of the distal radial epiphysis; in the teenager the clavicle might fracture; in the young adult the scaphoid is commonly fractured; and in the elderly the distal end of the radius is fractured about 1 in. (2.5 cm) proximal to the wrist joint (Colles’ fracture).

Elbow Joint-Movements-Important Movements-Stability of Elbow Joint-Dislocations of the Elbow Joint-Arthrocentesis of the Elbow Joint- Damage to the Ulnar Nerve with Elbow Joint Injuries -Radiology of the Elbow Region after Injury-

Elbow Joint

■■ Articulation: This occurs between the trochlea and capitulum of the humerus and the trochlear notch of the ulna and the head of the radius. The articular surfaces are covered with hyaline cartilage.

■■ Type: Synovial hinge joint

■■ Capsule: Anteriorly, it is attached above to the humerus along the upper margins of the coronoid and radial fossae and to the front of the medial and lateral epicondyles and below to the margin of the coronoid process of the ulna and to the anular ligament, which surrounds the head of the radius. Posteriorly, it is attached above to the margins of the olecranon fossa of the humerus and below to the upper margin and sides of the olecranon process of the ulna and to the anular ligament.

■■ Ligaments: The lateral ligament is triangular and is attached by its apex to the lateral epicondyle of the humerus and by its base to the upper margin of the anular ligament. The medial ligament is also triangular and consists principally of three strong bands: the anterior band, which passes from the medial epicondyle of the humerus to the medial margin of the coronoid process; the posterior band, which passes from the medial epicondyle of the humerus to the medial side of the olecranon; and the transverse band, which passes between the ulnar attachments of the two preceding bands.

■■ Synovial membrane: This lines the capsule and covers fatty pads in the floors of the coronoid, radial, and olecranon fossae; it is continuous below with the synovial membrane of the proximal radioulnar joint.

■■ Nerve supply: Branches from the median, ulnar, musculocutaneous, and radial nerves

Movements

The elbow joint is capable of flexion and extension. Flexion is limited by the anterior surfaces of the forearm and arm coming into contact. Extension is checked by the tension of the anterior ligament and the brachialis muscle. Flexion is performed by the brachialis, biceps brachii, brachioradialis, and pronator teres muscles. Extension is performed by the triceps and anconeus muscles. It should be noted that the long axis of the extended forearm lies at an angle to the long axis of the arm. This angle, which opens laterally, is called the carrying angle and is about 170° in the male and 167° in the female. The angle disappears when the elbow joint is fully flexed.

Important Movements

■■ Anteriorly: The brachialis, the tendon of the biceps, the median nerve, and the brachial artery

■■ Posteriorly: The triceps muscle, a small bursa intervening

■■ Medially: The ulnar nerve passes behind the medial epicondyle and crosses the medial ligament of the joint.

■■ Laterally: The common extensor tendon and the supinator.

Stability of Elbow Joint

The elbow joint is stable because of the wrench-shaped articular surface of the olecranon and the pulley-shaped trochlea of the humerus; it also has strong medial and lateral ligaments.

When examining the elbow joint, the physician must remember the normal relations of the bony points. In extension, the medial and lateral epicondyles and the top of the olecranon process are in a straight line; in flexion, the bony points form the boundaries of an equilateral triangle.

Dislocations of the Elbow Joint

Elbow dislocations are common, and most are posterior. Posterior dislocation usually follows falling on the outstretched hand. Posterior dislocations of the joint are common in children because the parts of the bones that stabilize the joint are incompletely developed. Avulsion of the epiphysis of the medial epicondyle is also common in childhood because then the medial ligament is much stronger than the bond of union between the epiphysis and the diaphysis.

Arthrocentesis of the Elbow Joint

The anterior and posterior walls of the capsule are weak, and when the joint is distended with fluid, the posterior aspect of the joint becomes swollen. Aspiration of joint fluid can easily be performed through the back of the joint on either side of the olecranon process.


Damage to the Ulnar Nerve with Elbow Joint Injuries

The close relationship of the ulnar nerve to the medial side of the joint often results in its becoming damaged in dislocations of the joint or in fracture dislocations in this region. The nerve lesion can occur at the time of injury or weeks, months, or years later. The nerve can be involved in scar tissue formation or can become stretched owing to lateral deviation of the forearm in a badly reduced supracondylar fracture of the humerus. During movements of the elbow joint, the continued friction between the medial epicondyle and the stretched ulnar nerve eventually results in ulnar palsy

Radiology of the Elbow Region after Injury

In examining lateral radiographs of the elbow region, it is important to remember that the lower end of the humerus is normally angulated forward 45° on the shaft; when examining a patient, the physician should see that the medial epicondyle, in the anatomic position, is directed medially and posteriorly and faces in the same direction as the head of the humerus.

Shoulder Joint-Movements-Stability of the Shoulder Joint-Dislocations of the Shoulder Joint-Anterior Inferior Dislocation--Posterior Dislocations-Shoulder Pain

Shoulder Joint

■■ Articulation: This occurs between the rounded head of the humerus and the shallow, pear-shaped glenoid cavity of the scapula. The articular surfaces are covered by hyaline articular cartilage, and the glenoid cavity is deepened by the presence of a fibrocartilaginous rim called the glenoid labrum.

■■ Type: Synovial ball-and-socket joint

■■ Capsule: This surrounds the joint and is attached medially to the margin of the glenoid cavity outside the labrum; laterally, it is attached to the anatomic neck of the humerus. The capsule is thin and lax, allowing a wide range of movement. It is strengthened by fibrous slips from the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles (the rotator cuff muscles).

■■ Ligaments: The glenohumeral ligaments are three weak bands of fibrous tissue that strengthen the front of the capsule. The transverse humeral ligament strengthens the capsule and bridges the gap between the two tuberosities . The coracohumeral ligament strengthens the capsule above and stretches from the root of the coracoid process to the greater tuberosity of the humerus.

■■ Accessory ligaments: The coracoacromial ligament extends between the coracoid process and the acromion. Its function is to protect the superior aspect of the joint

■■ Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces. It forms a tubular sheath around the tendon of the long head of the biceps brachii. It extends through the anterior wall of the capsule to form the subscapularis bursa beneath the subscapularis muscle .

■■ Nerve supply: The axillary and suprascapular nerves

Movements

The shoulder joint has a wide range of movement, and the stability of the joint has been sacrificed to permit this.

(Compare with the hip joint, which is stable but limited in its movements.) The strength of the joint depends on the tone of the short rotator cuff muscles that cross in front, above, and behind the joint—namely, the subscapularis, supraspinatus, infraspinatus, and teres minor. When the joint is abducted, the lower surface of the head of the humerus is supported by the long head of the triceps, which bows downward because of its length and gives little actual support to the humerus. In addition, the inferior part of the capsule is the weakest area.

Stability of the Shoulder Joint

The shallowness of the glenoid fossa of the scapula and the lack of support provided by weak ligaments make this joint an unstable structure. Its strength almost entirely depends on the tone of the short muscles that bind the upper end of the humerus to the scapula—namely, the subscapularis in front, the supraspinatus above, and the infraspinatus and teres minor behind. The tendons of these muscles are fused to the underlying capsule of the shoulder joint. Together, these tendons form the rotator cuff.

The least supported part of the joint lies in the inferior location, where it is unprotected by muscles.

Dislocations of the Shoulder Joint

The shoulder joint is the most commonly dislocated large joint.

Anterior Inferior Dislocation

Sudden violence applied to the humerus with the joint fully abducted tilts the humeral head downward onto the inferior weak part of the capsule, which tears, and the humeral head comes to lie inferior to the glenoid fossa. During this movement, the acromion has acted as a fulcrum. The strong flexors and adductors of the shoulder joint now usually pull the humeral head forward and upward into the subcoracoid position.

Posterior Dislocations

Posterior dislocations are rare and are usually caused by direct violence to the front of the joint. On inspection of the patient with shoulder dislocation, the rounded appearance of the shoulder is seen to be lost because the greater tuberosity of the humerus is no longer bulging laterally beneath the deltoid muscle. A subglenoid displacement of the head of the humerus into the quadrangular space can cause damage to the axillary nerve, as indicated by paralysis of the deltoid muscle and loss of skin sensation over the lower half of the deltoid. Downward displacement of the humerus can also stretch and damage the radial nerve.

 

Shoulder Pain

The synovial membrane, capsule, and ligaments of the shoulder joint are innervated by the axillary nerve and the suprascapular nerve. The joint is sensitive to pain, pressure, excessive traction, and distention. The muscles surrounding the joint undergo reflex spasm in response to pain originating in the joint, which in turn serves to immobilize the joint and thus reduce the pain.

Injury to the shoulder joint is followed by pain, limitation of movement, and muscle atrophy owing to disuse. It is important to appreciate that pain in the shoulder region can be caused by disease elsewhere and that the shoulder joint may be normal; for example, diseases of the spinal cord and vertebral column and the pressure of a cervical rib (see page XXX) can cause shoulder pain. Irritation of the diaphragmatic pleura or peritoneum can produce referred pain via the phrenic and supraclavicular nerves.

Acromioclavicular Joint-Movements-Important Relations-Acromioclavicular Joint Injuries-Acromioclavicular Dislocation-

Acromioclavicular Joint

■■ Articulation: This occurs between the acromion of the scapula and the lateral end of the clavicle.

■■ Type: Synovial plane joint

■■ Capsule: This surrounds the joint and is attached to the margins of the articular surfaces.

■■ Ligaments: Superior and inferior acromioclavicular ligaments reinforce the capsule; from the capsule, a wedge-shaped fibrocartilaginous disc projects into the joint cavity from above.

■■ Accessory ligament: The very strong coracoclavicular ligament extends from the coracoid process to the undersurface of the clavicle. It is largely responsible for suspending the weight of the scapula and the upper limb from the clavicle.

■■ Synovial membrane: This lines the capsule and is attached to the margins of the cartilage covering the articular surfaces.

■■ Nerve supply: The suprascapular nerve

Movements

A gliding movement takes place when the scapula rotates or when the clavicle is elevated or depressed.

Important Relations

■■ Anteriorly: The deltoid muscle

■■ Posteriorly: The trapezius muscle

■■ Superiorly: The skin

Acromioclavicular Joint Injuries

The plane of the articular surfaces of the acromioclavicular joint passes downward and medially so that there is a tendency for the lateral end of the clavicle to ride up over the upper surface of the acromion. The strength of the joint depends on the strong coracoclavicular ligament, which binds the coracoid process to the undersurface of the lateral part of the clavicle. The greater part of the weight of the upper limb is transmitted to the clavicle through this ligament, and rotary movements of the scapula occur at this important ligament.

Acromioclavicular Dislocation

A severe blow on the point of the shoulder, as is incurred during blocking or tackling in football or any severe fall, can result in the acromion being thrust beneath the lateral end of the clavicle, tearing the coracoclavicular ligament. This condition is known as shoulder separation. The displaced outer end of the clavicle is easily palpable. As in the case of the sternoclavicular joint, the dislocation is easily reduced, but withdrawal of support results in immediate redislocation.