Humerus

one of the long tubular bones of the upper arm, which extends from the shoulder to the elbow. It articulates with the scapula proximally and with the radius and ulna distally. Also, see humerus.

2. Pathology

The bone may contain notches or shallow grooves in the medial cortex at its proximal end as a normal variant in young adolescents. In addition, the greater tuberosity of the humerus may contain a large amount of cancellous bone and appear on radiographs as a pseudocyst; this should not be mistaken for a destructive lesion. Similarly, the supracondylar process humerus is a bone outgrowth on the anteromedial surface of the distal end of the humerus. The ligament of Struthers may extend from its tip and lead to compression of the median nerve.

The humerus may be involved in numerous diseases that affect the musculoskeletal system. In Pagets disease, the epiphysis is the main site of involvement. Radiographic features include cortical thickening with encroachment on the medullary canal, bowing, fracture and periosteal new bone leading to widening of the bone surface.

Fractures of the humerus are common and can be classified into various types (Table 1).

Humerus, Table 1. Fractures of the humerus.

Osteonecrosis of the humeral head may occur if the blood supply to both the muscular insertions and the arcuate branch of the anterior circumflex humeral artery is disrupted. Common causes are displaced fracture of the anatomic neck or a severe fracture dislocation of the humerus.

Anterior dislocations of the humeral head accompanied by fracture produce the Bankart lesion and Hill Sachs lesion. A special type of inferior dislocation of the humeral head (luxatio erecta is rare.

Disruption of the growth plate in the proximal portion of the humerus may result in an epiphysiolysis termed Little League shoulder syndrome. Chronic stress injuries from participation in other types of athletic activities also involve this region. Salter Harris classification type IV injuries frequently occur in children and also involve the growth plate of the humerus.

An entrapment neuropathy caused by trapping of the radial nerve in the spiral groove of the humerus may also occur. In shoulder impingement syndrome, one of the causes may be humeral abnormalities (congenital anomalies, fractures with malunions or altered position of a humeral

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