Abstract
BACKGROUND: In growing children, an expandable endoprosthesis is commonly used after distal femoral resection to compensate for loss of the distal femoral physis. Our hypothesis was that such prostheses can affect proximal tibial growth, which would contribute to an overall leg-length discrepancy and cause angular deformity. METHODS: Twenty-three skeletally immature patients underwent the placement of a distal femoral expandable endoprosthesis between 1994 and 2012. Tibial length, femoral length, and mechanical axis were measured radiographically to determine the growth rate. RESULTS: No patient had radiographic evidence of injury to the proximal tibial physis at the time of surgery other than insertion of the tibial stem. Fifteen (65%) of the patients experienced less proximal tibial growth in the operative compared with the contralateral limb. In ten (43%) of the patients, the discrepancy progressively worsened, whereas in five (22%) of the patients, the discrepancy stabilized. Seven patients did not develop tibial length discrepancy, and one patient had overgrowth of the tibia. For the ten patients with progressive shortening, the proximal tibial physis grew an average of 4.0 mm less per year in the operative limb. Five (22%) of the patients had ≥ 20 mm of tibial length discrepancy at last follow-up. Three of these patients underwent contralateral tibial epiphysiodesis. Three patients required corrective surgery for angular deformity. CONCLUSIONS: The tibial growth plate may not resume normal growth after implantation of a distal femoral prosthesis. Physeal bar resection, prosthesis revision, and contralateral tibial epiphysiodesis may be needed to address tibial growth abnormalities.