Internal Lengthening Device for Congenital Femoral Deficiency and Fibular Hemimelia

Patients with congenital limb shortening can present with joint instability, soft tissue contractures, and significant leg length discrepancy. Classically, lengthening is done with external fixation, which can result in scarring, pin site infection, loss of motion, and pain. We therefore developed an alternative to this approach, a new, controllable, internal lengthening device for patients with congenital limb shortening.

We evaluated this device in terms of (1) healing index, (2) complications, (3) accuracy of the device’s external controller, and (4) adjacent-joint ROM.

Between January 2012 and May 2013, we treated 66 patients for congenital limb shortening, of whom 21 were treated using this device. During this period, general indications for using the device were patients with leg length discrepancies of 2 cm or more, with intramedullary canals able to withstand rods of at least 12.5-mm diameter and 230-mm length, without active infection in the affected bone, able to comply with the need for frequent lengthening, and without metal allergies or an implanted pacemaker. We included only those patients who had completed their course of treatment and were currently fully weightbearing, leaving 18 patients (21 bone segments) available for followup at a minimum of 6 months after limb lengthening (mean, 14 months; range, 6–22 months). Mean age was 19 years (range, 9–49 years). Sixteen femurs and five tibias were lengthened a mean of 4.4 cm (range, 2.1–6.5 cm). Mean distraction index was 1.0 mm/day (range, 0.5–1.8 mm/day). Healing index, complications, device accuracy, and ROM were recorded. To date, 10 of the 21 devices have been removed. This was typically done 12–24 months after insertion when the bone was solidly healed on all four cortices.

Mean healing index was 0.91 months/cm (range, 0.2–2.0 months/cm). There were seven complications requiring an additional unplanned surgery, including one hip flexion contracture, three femurs with delayed healing, one tibia with delayed healing, one hip subluxation/dislocation, and one knee subluxation. The external controller was accurate as programmed and actual lengthening amounts were consistent. ROMs of the hip, knee, and ankle were essentially maintained.

This device is completely internal, allowing for satisfactory joint motion during treatment in most patients. Lengthening was achieved in an accurate, controlled manner, and all patients reached their goal length. Complications remain a concern, as is the case with all approaches to this complex patient population. Both future comparative studies and longer-term followup are needed.

Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.