Osteochondroma of the Distal Tibia and Fibula

Osteochondroma occur in the distal fibula and the distal tibia, where they can cause recurrent sprains, ankle stiffness, or a palpable mass. Distal fibular lesions often impinge on the tibia and require removal. Large or multiple lesions in the distal leg result in differential longitudinal growth of the tibia and fibula leading to valgus deformity of the ankle. The valgus deformity will remodel if these lesions are removed early. Patients with osteochondromatosis present in early adulthood with valgus overload of the ankle. Severe ankle deformity will not remodel, and supramalleolar osteotomy may be required to correct symptomatic valgus.

Osteochondroma of the Foot

Osteochondroma may be the most common bone tumor in the foot, although that is not the case in my practice. This tumor affects teenages and young adults in their twenties, but occasionally may be see in older adults who have had delayed seeking medical advice. The male female ratio is 1.6 to 1. The tumor is almost always located on the metatarsals. The tumor presents as a painless lump that increases in size with growth of the patient.

In the distal tibia and fibula, osteochondromas may present as acute or recurrent ankle sprains, ankle pain, ankle stiffness, or a palpable mass. The lesion may cause plastic deformation of the ankle and varus deformity. The deformity will remodel after tumor removal, and younger patients remodel more completely. Substantial ankle varus did not remodel. (Chin el al JBJS 82A Sept 2000 1269 - 1278)

Radiologically, the tumor arises from the surface of the bone and the cortex and medullary cavity of the lesion is continuous with the cortex and medullary cavity of the bone. A CT scan can be very helpful in confirming this and may thus confirm the diagnosis. MRI is usually not necessary for diagnosis but may help define the nearby neurovascular structures in preparation for surgery. MRI will also allow precise measurement of the thickness of the cartilage cap on the lesion, which is an indicator of the potential for amlignant degeneration.

Treatment consists of simple excision by osteotomy through the base of the stalk. Surgeons do not need to remove every vestige of the stalk or base of the tumor to achieve complete resolution of the symptoms. The neurovascular bundle may be very near the intended osteotomy site. Damage to the neurovascular structures of the foot is not an acceptable complication from what should be a simple removal of a benign bone tumor.

Surgical treatment should be deferred until the patient is at or near skeletal maturity, if possible. The lesions are less likely to recur and are better defined so that complete removal can be easily accomplished and damage to the growth plate as well as recurrence can be avoided.

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