Extramedullary Limb Lengthening with a Motorized Lengthening Nail in an Adult with Conradi–Hünermann Syndrome

Abstract

Extramedullary limb lengthening using a motorized lengthening nail offers an alternative in situations where narrow canals or atypical femoral morphology preclude intramedullary fixation. Although this technique has been described in pediatric settings, its use in skeletally mature patients remains limited. A 22-year-old female patient with Conradi–Hünermann syndrome presented with an approximately 7 cm leg length discrepancy. Due to atypical femoral anatomy, intramedullary nail placement was not feasible. A corrective trapezoidal wedge osteotomy was performed, and a Precice™ magnetic lengthening nail was implanted in a retrograde, extramedullary, and submuscular plane. Distraction commenced on the postoperative day nine and was adjusted according to the quality of the regenerate bone on serial radiographs. A total of 40 mm of lengthening was achieved over 10 weeks without loss of alignment, implant failure, or other complications. The patient advanced to full weight-bearing by 4.5 months, underwent elective nail removal at 1 year, and demonstrated maintained alignment and functional improvement at a 26-month follow-up. Although an off-label application, extramedullary limb lengthening using a motorized lengthening nail in an “off-label” manner can be safely and effectively performed in carefully selected adult patients with complex femoral anatomy. This case highlights the feasibility and successful outcomes that can be achieved with preoperative planning and surgical execution.