Growth prediction in extendable tumor prostheses in children

Limb salvage procedures for malignant bone tumors of the lower limb in children usualy involve resection of at least one growing physis. To achieve equal leg length, reconstruction relies on accurate prediction of the remaining growth potential of the child. The current authors present the results of predicted growth versus actual prosthetic elongation observed in a group of 15 children fitted with extendable tumor endoprostheses of the lower limb who subsequently have reached skeletal maturity. All patients had at least one of the distal femoral or proximal tibial physes resected for a primary malignant bone tumor. Eight patients underwent distal femoral resection, four patients underwent proximal tibial resection, and three patients had total resection of the femur. All patients received custom-made Howmedica extendable prostheses. In two patients, a newly developed automatic elongation module was used. At followup, between 70 and 158 months, the patients achieved a mean elongation of the surgically treated limb of 10.4 cm (range, 1.1-19.5 cm), which exceeded the predicted growth by 24.3%. Final leg length discrepancies did not exceed 1 cm. Using incremental extendable tumor endoprostheses, individual adaptation of the elongation procedures could be achieved for equalization of leg length discrepancies in children after resection of primary malignant bone tumors of the lower limb.