The clavicle is the most frequently fractured bone in the body.

Clavicle fractures occur most frequently at the junction of the middle and lateral thirds of the clavicle (Figure 6-2). The patient characteristically supports the sagging limb with the opposite hand. Subclavian vessels and trunks of the brachial plexus are at risk in fractures of the middle third because they lie behind only the thin subclavius muscle. As the fractured clavicle heals, supraclavicular nerves may be trapped by callous formation, causing chronic neck pain.

The suprascapular nerve may be trapped and compressed as it passes through the suprascapular foramen, which affects functions of the supraspinatus and infraspinatus muscles. The patient has difficulty initiating abduction and weak lateral rotation of the arm.

Suprascapular nerve entrapment at the suprascapular notch weakens the supraspinatus and infraspinatus muscles.

Avulsion fractures of the greater tubercle are relatively common, often in association with anterior dislocation of the shoulder joint. The attachments of the supraspinatus, infraspinatus, and teres minor muscles hold the tubercle posteriorly, while the subscapularis and other muscles rotate the rest of the humerus medially.

Greater or lesser tubercle of humerus may be avulsed by attached rotator cuff muscles.

The lesser tubercle, which receives the insertion of the subscapularis muscle, may be avulsed in violent lateral rotation of the abducted arm (e.g., a football player attempting to tackle a ball carrier running by) or in a rare posterior dislocation of the shoulder joint.

Surgical neck fracture injures the axillary nerve and the posterior humeral circumflex artery.

Surgical neck fractures, which are common, may damage the axillary nerve and the posterior humeral circumflex artery as they pass through the quadrangular space (Figure 6-3).

Humeral shaft fracture injures the radial nerve and the profunda brachii artery.

Fractures of the humeral shaft may damage the radial nerve and profunda brachii artery in the radial groove. Fractures proximal to the deltoid insertion will cause adduction of the proximal fragment by the pectoralis major with the distal fragment pulled proximally by the deltoid. In contrast, fracture distal to the deltoid insertion will cause abduction of the proximal fragment by the deltoid, with the distal fragment pulled proximally by the biceps and triceps.

Supracondylar fractures may injure the brachial artery and median nerve and are common in children and in arm wrestlers. Damage to the brachial artery may compromise the blood supply of the forearm, resulting in compartment syndrome with Volkmann ischemic contracture, usually involving the flexor compartment. Anterior displacement of the jagged proximal fragment damages the attached brachialis, possibly causing heterotopic ossification (posttraumatic myositis ossificans).

Supracondylar humeral fracture may cause forearm compartment syndrome.

Forceful abduction of the extended elbow may produce avulsion of the medial epicondyle in children because the ulnar collateral ligament is stronger than the epiphysis for the medial epicondyle. The common flexor tendon of the superficial forearm muscles will pull the avulsed fragment distally. The ulnar nerve may be damaged.

Medial epicondyle may be avulsed before skeletal maturity by the forceful abduction of the extended elbow.

The ulnar nerve behind the medial epicondyle can be bumped or compressed, causing “funny bone” paresthesia or numbness.

The brachial artery lies just medial to the biceps brachii tendon in the cubital fossa, where the stethoscope is placed when taking blood pressure. The deep branch of the radial nerve may be injured in a fracture of the neck of the radius. See Figure 6-5 for fractures of the radial shaft.

The olecranon may be avulsed by forcible contraction of the triceps brachii during a fall or by a direct blow. The pull of the triceps may displace the olecranon fragment proximally. “Student’s elbow” is olecranon bursitis caused by repeated friction against the olecranon bursa.

The olecranon may be avulsed by forcible triceps brachii contraction or a direct blow.

Transverse fractures of the distal radius are often characterized by shortening of the radius, with the radial styloid process repositioned proximal to the ulnar styloid process. As a result of the fracture, the roughened dorsal tubercle of the radius may rupture the extensor pollicis longus tendon.

Colles fracture, in which the distal radial fragment is displaced posteriorly (“dinner fork deformity”), is common after age 50 and most often occurs when an individual breaks a fall with an outstretched hand. It is the second most common fracture in women with osteoporosis.

The distal fragment of the radius is anteriorly displaced in Smith fracture.

Colles fracture: “dinner fork deformity”

Scaphoid fractures may not show on radiographs for 10 days to 2 weeks, but deep tenderness will be present in the anatomical snuffbox. The proximal fragment may undergo avascular necrosis because the blood supply is interrupted (Figure 6-7), or nonunion of the fracture may occur.

The scaphoid is the most frequently fractured carpal bone, with a risk of avascular necrosis.

Forced hyperextension of the wrist may cause anterior dislocation of the lunate, compressing the median nerve.

Deep tenderness in anatomical snuffbox: scaphoid fracture

The hook of the hamate bone frequently is fractured in racket sports and golf. Dense connective tissue converts the depression between the hook of hamate and the pisiform into Guyon canal (ulnar tunnel), where the ulnar nerve may be compressed (e.g., by a ganglion cyst).

The ulnar nerve may be compressed in Guyon canal between the pisiform and hamate bones.

The necks of metacarpal bones are frequently fractured during fistfights. Typically, fractured fifth metacarpals are seen in unskilled fighters (boxer’s fracture). Professional boxers punch mainly with the second and third metacarpals and rarely suffer these fractures.

A fractured neck of the fifth metacarpal is “boxer’s fracture.”

Sternoclavicular joint only bony union between axial and upper extremity skeletons

The sternoclavicular joint is so stable that the clavicle usually will fracture before the joint dislocates. If the joint dislocates, it is usually anteriorly. In a rare posterior dislocation, however, the medial end of the clavicle may compress the trachea or major blood vessels.

A posterior dislocation of the sternoclavicular joint may compress the trachea or great vessels.

The latissimus dorsi muscle, and to a lesser extent the pectoralis major muscle, acts through attachments on the humerus to depress the shoulder girdle. Without functioning of these muscles, an individual cannot walk with axillary crutches or negotiate wheelchair transfers.

Falling on an outstretched hand or a point of the shoulder often dislocates the acromioclavicular joint (shoulder separation). The coracoclavicular ligament tears when the lateral end of the clavicle rides up over the acromion. The weight of the shoulder causes it to drop away, or separate, from the clavicle (see Figure 6-8).

Shoulder separation: acromioclavicular joint dislocates with tearing of the coracoclavicular ligament

The shoulder joint accounts for 120° of shoulder abduction, and scapular rotation for 60°.

The supraspinatus initiates arm abduction, and the deltoid continues it after the first 15°.

The glenohumeral joint is the most frequently dislocated large joint (shoulder dislocation). In the usual anterior-inferior dislocation, muscle traction pulls the dislocated humeral head into a subcoracoid position (Figure 6-9). The axillary nerve may be injured. Posterior dislocations comprise only 5% but are seen following convulsions or electric shock. A posterior dislocation may not be apparent on standard AP radiographs.

The shoulder joint is the most frequently dislocated large joint.

Abduction of the arm is initiated (first 15°) by the supraspinatus muscle (suprascapular nerve). Further abduction to the horizontal position is a function of the deltoid muscle (axillary nerve). Raising the extremity above the horizontal position requires upward scapular rotation by action of the trapezius (accessory nerve) and serratus anterior (long thoracic nerve). Injury to these muscles or nerves compromises abduction.

Subacromial bursitis is often due to deposition of calcium within the supraspinatus tendon (calcific supraspinatus tendinitis) in middle-aged males. The patient typically experiences a painful arc of movement from 50 to 130° of abduction.

Osteoarthritic changes in the glenohumeral joint or chronic tendinitis may cause a rupture of the long head of the biceps tendon. Alternatively, the tendon may be avulsed from the supraglenoid tubercle of the scapula. The detached muscle belly contracts into a ball in the anterior arm on attempted elbow flexion (Popeye deformity).

Ruptured long head of biceps tendon: Popeye deformity

Disorders such as bicipital tendinitis and cervical disc herniation that produce shoulder pain or prolonged immobilization in a cast or sling may cause adhesive capsulitis (“frozen shoulder”), significantly restricting movement.

Pain may be referred to the shoulder in various disorders, such as cervical disc herniation, angina pectoris, pleuritis, cholecystitis, or ruptured spleen.

The trapezius is the only muscle that can elevate the shoulder. Its paralysis from a lesion of the spinal accessory nerve or a stroke causes a drooping shoulder and an inability to shrug. Inferior subluxation of the head of the humerus is common following paralysis of the trapezius due to the drooping shoulder.

The shoulder joint usually dislocates in an anteroinferior direction.

The brachialis muscle is the main flexor of the elbow; the biceps brachii muscle flexes and assists in supination. Both are innervated by the musculocutaneous nerve. When these primary elbow flexors are paralyzed, the brachioradialis muscle (radial nerve) provides some ability to flex the elbow.

Brachioradialis provides weak elbow flexion if the brachialis and biceps are paralyzed.

In a supracondylar fracture of the humerus, the medial and lateral epicondyles and olecranon process maintain their triangular relationship. In elbow dislocation, the olecranon aligns with the epicondyles. Posterior dislocations of the elbow are frequent in children.

A lesion of the median nerve at or above the elbow paralyzes the pronator quadratus and pronator teres muscles, with loss of ability to pronate the forearm. When the supinator muscle is paralyzed from a radial nerve lesion, the biceps brachii muscle can still supinate the forearm.

Median nerve lesion at elbow: loss of forearm pronation

In adults, the head of the radius is not dislocated without tearing the anular ligament. Young children are prone to dislocation of the immature head of the radius from the encircling anular ligament, a “pulled elbow” or “nursemaid’s elbow,” caused by sudden traction on an extended forearm.

Infections of the elbow joint always involve the proximal radioulnar joint because of their shared joint cavity.

Lifting a preschool child by the forearm or hand may dislocate the head of the radius from the anular ligament.

Force transmission: hand → radius → interosseous membrane → ulna → humerus

Wrist extension is necessary for effective finger flexion.

MP joints allow abduction-adduction only in extension due to collateral ligaments.