Osteochondromas of the distal aspect of the tibia or fibula. Natural history and treatment.

BACKGROUND: There is little information on the natural history or treatment of osteochondromas arising from the distal aspect of either the tibia or the fibula. It is believed that there is a risk of deformation of the ankle if these exostoses are left untreated or if the physis or neurovascular structures are injured during operative intervention.

METHODS: We reviewed the records of twenty-three patients who had been treated for osteochondroma of the distal aspect of the tibia or fibula between 1980 and 1996. Four of the patients had hereditary multiple cartilaginous exostoses. There were seventeen male and six female patients, and the average age at the time of presentation was sixteen years (range, eight to forty-eight years).

RESULTS: Preoperative radiographs showed evidence of plastic deformation of the fibula in eleven patients who had a large osteochondroma. Four patients elected not to have an operation. The tumor was excised in nineteen patients. Postoperatively, all nineteen patients had a Musculoskeletal Tumor Society score of 100 percent for function of the lower extremity with pain-free symmetrical and unrestricted motion of the ankle at the latest follow-up examination. Partial remodeling of the tibia and fibula gradually diminished the asymmetry of the ankles in all nineteen operatively managed patients; however, the remodeling was most complete in the younger patients. Pronation deformities of the ankle did not change after excision of the tumor. Complications of operative treatment included four recurrences (only three of which were symptomatic), one sural neuroma, one superficial wound infection, and one instance of growth arrest of the distal aspects of the tibia and fibula.

CONCLUSIONS: Osteochondromas of the distal and lateral aspects of the tibia were more often symptomatic than those of the distal aspect of the fibula; they most commonly occurred in the second decade of life with ankle pain, a palpable mass, and unrestricted ankle motion. Untreated or partially excised lesions in skeletally immature patients may become larger and cause plastic deformation of the tibia and fibula and a pronation deformity of the ankle. Ideally, operative intervention should be delayed until skeletal maturity, but, in symptomatic patients, partial excision preserving the physis may be necessary for the relief of symptoms and the prevention of progressive ankle deformity. However, partial excision is associated with a high rate of recurrence, so a close follow-up is required. Skeletally mature patients who are symptomatic may require excision of the tumor.