Clinical features

The clavicle has three functions:

1 to transmit forces from the upper limb to the axial skeleton;

2 to act as a strut holding the arm free from the trunk, to hang supported principally by trapezius;

3 to provide attachment for muscles.

The weakest point along the clavicle is the junction of the middle and outer third. Transmission of forces to the axial skeleton in falls on the shoulder or hand may prove greater than the strength of the bone at this site and this indirect force is the usual cause of fracture.

When fracture occurs, the trapezius is unable to support the weight of the arm so that the characteristic picture of the patient with a fractured clavicle is that of a man supporting his sagging upper limb with his opposite hand. The lateral fragment is not only depressed but also drawn medially by the shoulder adductors, principally the teres major, latissimus dorsi and pectoralis major (Fig. 121).

The humerus (Fig. 122)

The upper end of the humerus consists of a head (one-third of a sphere) facing medially, upwards and backwards, separated from the greater and lesser tubercles by the anatomical neck. The tubercles, in turn, are separated by

Fracture Displacement Muscle Pull
Fig. 121 The deformity of a fractured clavicle-downward displacement and adduction of the outer fragment by gravity and muscle spasm respectively; slight elevation of the inner fragment by the sternocleidomastoid.

the bicipital groove along which emerges the long head of biceps from the shoulder joint.

Where the upper end and the shaft of the humerus meet there is the narrow surgical neck against which lie the axillary nerve and circumflex humeral vessels. The shaft itself is circular in section above and flattened in its lower part. The posterior aspect of the shaft bears the faint spiral groove, demarcating the origins of the medial and lateral heads of the triceps between which wind the radial nerve and the profunda vessels.

The lower end of the humerus bears the rounded capitulum laterally, for articulation with the radial head, and the spool-shaped trochlea medially, articulating with the trochlear notch of the ulna.

The medial and lateral epicondyles, on either side, are extra-capsular; the medial is the larger of the two, extends more distally and bears a groove on its posterior aspect for the ulnar nerve.

Three important nerves thus come into close contact with the humerus —the axillary, the radial and the ulnar; they may be damaged, respectively, in fractures of the humeral neck, midshaft and lower end (Fig. 122).

It is an important practical point to note that the lower end of the humerus is angulated forward 45° on the shaft. This is easily confirmed by examining a lateral radiograph of the elbow, when it will be seen that a vertical line continued downwards along the front of the shaft bisects the

Radial Nerve Humerus Spiral Groove
Fig. 122 The (a) anterior and (b) posterior view of the humerus. (c) The humerus with its three major related nerves—axillary, radial and ulnar—all of which are in danger of injury in humeral fractures.

capitulum. Any decrease of this angulation indicates backward displacement of the distal end of the humerus and is good radiographic evidence of a supracondylar fracture.

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Responses

  • ruby brockhouse
    Are there any grooves in the shaft of the humerus?
    7 years ago
  • sam mcintosh
    How does the radial nerve?
    7 years ago
  • Leevi Paananen
    What separates the head of the humerus from the shaft?
    7 years ago
  • tove
    Where is radial groove in the body?
    7 years ago
  • atte
    What are the muscles of the hand posterior view?
    6 years ago
  • abaalom
    Where does the spiral groove of the humerus demarcate?
    6 years ago

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