Osteochondromas (Exostoses)

There is no doubt that the patient had a fracture of the distal right tibia in the past as the AP and lateral views clearly demonstrate.
More proximally, there is deformity of the right tibia and fibula with boney excrescences in the metaphyseal region of both bones.
- These boney structures are continuous with the shafts of the bones to which they are attached.
- Radiographically, they appear to have the density and structure of normal cancellous bone.
- They appear well-marginated by cortical bone which is continuous with the shaft.
- No calcifications or masses are present.
- Findings are well shown on the AP and lateral views.

Findings are compatible with osteochondromas (exostoses). No radiographic search was performed to establish a diagnosis of multiple hereditary exostosis.

You may wish to review some facts concerning osteochondromas:

Lesions are described by Resnick as "cartilage-covered osseous excrescences that arise from the surface of bone."
- Continuous with the parent bone.
- Usually metaphyseal, where it may be associated with widening and deformity.
- Growth usually ceases with puberty.
- Cartilagenous cap thin or non-existent in adults.
When multiple, multiple hereditary exostosis is suspected.
When solitary, developmental physeal defect vs. neoplasm.
Often discovered early as a painless mass.
Femur, humerus, tibia most commonly involved but occurs elsewhere.
- Exostoses commonly point away from the joint.
Complications include fx, impingement on nerves and blood vessels (pseudoaneurysms), and bursa formation.
Malignant degeneration in approx. 1% usually to chondrosarcoma.
- Pain, growth, bone erosion, irreg. Ca+2 helpful if they occur.
- Normal bone scan virtually excludes malignant degeneration.
DDx: osteophyte, enthesophyte, heterotopic ossification, paraosteal osteogenic sarcoma, peripheral chondrosarcoma, others.

Ref: Resnick, D., Bone and Joint Imaging, W.B. Saunders, Philadelphia, PA, 1989, pp. 1132-1138.

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