PRECICE® magnetically-driven, telescopic, intramedullary lengthening nail: pre-clinical testing and first 30 patients

Abstract

Introduction: Femoral/tibial lengthening with a telescopic, magnetically-powered, intramedullary nail is an alternative to lengthening with external fixation.

Methods: Pre-clinical testing was conducted of the PRECICE in a human cadaver. A retrospective review of the first 30 consecutive patients who underwent unilateral lengthening was also conducted. Nail accuracy was obtained by comparing the amount of nail distraction to the final bone length achieved at the end of the distraction process. Relative standard deviation of accuracy was used to calculate nail precision.

Results: Devices performed successfully in a human cadaver. Thirty consecutive patients (10 females, 20 males; mean age, 23 years) with limb length discrepancy (LLD) were followed an average of 19 months (range, 12-24 months). Etiology included congenital shortening (14), posttraumatic deformities (7), Ollier disease (3), osteosarcoma resection (1), prior clubfoot (2), hip dysplasia (1), post-septic growth arrest of knee (1), and LLD after hip arthroplasty (1). Twenty-four femoral and eight tibial nails were implanted. Mean preoperative lengthening goal was 4.4 cm (range, 2-6.5 cm); mean postoperative length achieved was 4.3 cm (range, 1.5-6.5 cm). Average consolidation index was 36.4 days/cm (range, 12.8-113 days/cm). Mean nail accuracy was 97.3% with a precision of 92.4%. Average preoperative and 12-month postoperative Enneking scores were 21.5 and 25.3 (p < 0.001), respectively. The preoperative and 12-month postoperative SF-12 physical and mental component scores were not statistically different. Nine complications (nine limb segments) resolved: two partial femoral unions, two suspected deep vein thrombosis (DVT), one delayed tibial union, one fibular nonunion, one peroneal nerve irritation, one knee joint subluxation, and one confirmed DVT. Twenty-nine (91%) of 32 limb segments achieved successful bone healing without revision surgery.

Discussion: Limb lengthening with PRECICE is reliable, but larger trials with longer follow-up will reveal limitations. Implantable nails prevent problems associated with external fixation, such as muscle tethering and pin-site infections.

Figure 1.

Clinical case shows normal healing. (A) Preoperative anteroposterior (AP) view full length standing radiograph of a patient with a limb length discrepancy. (B) AP view radiograph of the right femur after insertion of PRECICE. (C) AP view radiograph of the right femur after distraction. (D) Final AP view full length standing radiograph shows that the right femur healed after the lengthening goal was achieved. Figure used with permission (© 2016, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore).

Figure 2.

Clinical case with partial union. AP (A) and lateral (B) view radiographs of the right femur show partial union. After injection of bone marrow aspirate concentrate (platelet-rich plasma) into the partial union site and nail dynamization by removing the proximal locking screws, AP (C) and lateral (D) view radiographs showed complete healing. Figure used with permission (© 2016, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore).