Extramedullary Lengthening After a Distal Femoral Replacement to Improve Bone Stock and Restore Leg Length: A Case Report.

CASE: A 10-year-old boy with a left femur osteosarcoma treated with a growing distal femoral prosthesis developed a 6.5 cm limb-length discrepancy with erosion of the remaining femur. He underwent revision of the replacement with femoral transport and lengthening using an extramedullary lengthening nail. After treatment, his bone stock increased by 14 cm and his discrepancy decreased to 3.6 cm. He ambulates without assistive device using a shoe insert.

CONCLUSIONS: Extramedullary lengthening can increase bone stock and improve leg lengths. Multiple procedures may be required, and deformities can occur if lengthening is attempted beyond the tip of the intramedullary stem.