Musculoskeletal Imaging

Hereditary multiple exostoses

an autosomal dominant disorder characterized by presence of palpable bone masses, deformities due to shortening and bowing of bones, and joint restriction. The masses, which may number more than 100, are typically bilateral and symmetrical osteochondromas. The distal and proximal ends of the femur, tibia and fibula and the proximal end of the humerus are involved most typically (Fig.1) (Fig.2). The diagnosis of this disorder is virtually impossible to make if exostoses are not present in the bones about the knee. In some patients the distal ends of the radius and ulna may be involved, and the scapula, innominate bone and ribs are affected more commonly in patients with multiple exostoses than in those with solitary osteochondromas.

Defects in normal bone modelling and bone deformities such as bilateral coxa valga, widening of the proximal femoral metaphysis and bilateral and progressive changes about the wrist, are characteristic.

Radiographically, an effective survey would include frontal radiographs of the knees, pelvis and wrists; surveys could be supplemented with bone scans to identify metabolically active lesions.

The complications associated with hereditary exostoses are similar to those accompanying solitary osteochondromas and include fracture, vascular injury, neurologic compromise, bursa formation and malignant transformation.

DR/RB

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Fig.1

AP radiograph of the leg demonstrates multiple osteochondromas involving the proximal and distal aspects of the tibiae and fibulae.
Hereditary multiple exostoses, Fig.1
Hereditary multiple exostoses, Fig.2