CLAVICLE
Peculiarities of the Clavicle
1 It is the only long bone that lies horizontally.
2 It is subcutaneous throughout.
3 It is the first bone to start ossifying.
4 It is the only long bone which ossifies in membrane.
5 It is the only long bone which has two primary centres of ossification.
6 There is no medullary cavity.
7 It is occasionally pierced by the middle supraclavicular nerve.
It receives weight of upper limb via lateral one-third through coracoclavicular ligament and transmits weight of upper limb to the axial skeleton via medial two-thirds part.
CLINICAL ANATOMY OF CLAVICLE
The clavicle is commonly fractured by falling on the outstretched hand (indirect violence). The most common site of fracture is the junction between the two curvatures of the bone, which is the weakest point. The lateral fragment is displaced downwards by the weight of the limb as trapezius muscle alone is unable to support the weight of upper limb
The clavicles may be congenitally absent, or imperfectly developed in a disease called cleidocranial dysostosis.
In this condition, the shoulders droop, and can be approximated anteriorly in front of the chest .
SCAPULA
CLINICAL ANATOMY OF SACPULA
Paralysis of the serratus anterior causes ‘winging’ of the scapula. The medial border of the bone becomes unduly prominent, and the arm cannot be abducted beyond 90° .
The scaphoid scapula is a developmental anomaly, in which the medial border is concave.
HUMERUS
CLINICAL ANATOMY OF HUMERUS
The common sites of fracture of humerus are the surgical neck, shaft and supracondylar region.
Supracondylar fracture is common in young age. It is produced by a fall on the outstretched hand. The lower fragment is mostly displaced backwards, so that the elbow is unduly prominent, as in dislocation of the elbow joint. This fracture may cause injury to the median nerve. It may also lead to Volkmann’s ischaemic contracture caused by occlusion of the brachial artery.
The humerus has a poor blood supply at the junction of its upper one-third and lower twothirds. Fractures at this site show delayed union or non-union.
The head of the humerus commonly dislocates inferiorly (subglenoid)
RADIUS
CLINICAL ANATOMY OF RADIUS
The radius commonly gets fractured about 2 cm above its lower end (Colles’ fracture). This fracture is caused by a fall on the outstretched hand . The distal fragment is displaced upwards and backwards, and the radial styloid process comes to lie proximal to the ulnar styloid process. (It normally lies distal to the ulnar styloid process.) If the distal fragment gets displaced anteriorly, it is called Smith’s fracture
A sudden powerful jerk on the hand of a child may dislodge the head of the radius from the grip of the annular ligament. This is known as subluxation of the head of the radius (pulled elbow) . The head can normally be felt in a hollow behind the lateral epicondyle of the humerus.
ULNA
CLINICAL ANATOMY OF ULNA
The ulna is the stabilising bone of the forearm, with its trochlear notch gripping the lower end of the humerus. On this foundation, the radius can pronate and supinate for efficient working of the upper limb.
The shaft of the ulna may fracture either alone or along with that of the radius. Cross-union between the radius and ulna must be prevented to preserve pronation and supination of the hand.
Dislocation of the elbow is produced by a fall on the outstretched hand with the elbow slightly flexed. The olecranon process shifts posteriorly and the elbow is fixed in slight flexion. Normally, in an extended elbow, the tip of the olecranon process lies in a horizontal line with the two epicondyles of the humerus; and in the flexed elbow, the three bony points form an equilateral triangle. These relations are disturbed in dislocation of the elbow.
Fracture of the olecranon process is common and is caused by a fall on the point of the elbow. Fracture of the coronoid process is uncommon, and usually accompanies dislocation of the elbow.
Madelung’s deformity is dorsal subluxation (displacement) of the lower end of the ulna, due to retarded growth of the lower end of the radius.
