The head and surgical neck of the humerus may now be felt from the axilla, if the axillary fascia is relaxed by bringing the arm to the side. The great tuberosity can be indistinctly felt on the lateral aspect of the shoulder through the fibres of the deltoid. It lies vertically above the lateral epicondyle, and may be felt to rotate with the shaft. The inter-tubercular (bicipital) groove looks forward, and lies in a line drawn vertically through the biceps muscle.
The subclavian artery, with its vein to the median side and the cords of the brachial plexus to the lateral side, passes under the middle of the clavicle, and may be compressed against the first rib immediately above this bone.
Fracture of the Clavicle
Fracture of the clavicle is one of the commonest injuries met with in practice. As about one-third of the cases occur in children, the fracture is often of the greenstick variety. The fractures are seldom compound or complicated, unless as a result of gun-shot injuries; but occasionally one of the fragments pierces the skin, or comes to press upon the subclavian vessels or the cords of the brachial plexus, arresting the pulsation in the vessels of the limb, and causing severe pain in the arm.
Fig. 13.—Oblique Fracture of Right Clavicle in Middle Third, united.
The most common site of fracture is in the middle third ([Fig. 13]), and this usually results from indirect violence, such as a fall on the outstretched hand, the elbow, or the outer aspect of the shoulder, the force being transmitted through the glenoid cavity to the scapula, and thence by the coraco-clavicular ligaments to the clavicle. The violence is therefore of a twisting character, and the bone gives way near the junction of the lateral and middle thirds, just where the two natural curves of the bone meet, and where the supporting muscular and ligamentous attachments are weakest.
The fracture so produced is usually oblique from above, downwards and inwards. The sternal fragment may be slightly drawn upwards by the clavicular fibres of the sterno-mastoid, while the acromial fragment falls by the weight of the arm, and the fragments usually overlap to the extent of about half an inch. The shoulder, having lost the buttressing support of the clavicle, falls in towards the chest wall, narrowing the axillary space, while the weight of the arm pulls it downward, and the muscles inserted in the region of the bicipital groove pull it forward.
Fracture of the middle third may result also from a direct stroke, such as the recoil of a gun, or from violent muscular contraction, the fracture as a rule being transverse, and the displacement less marked than in fracture by indirect violence.