A magnetically controlled lengthening nail: A prospective study of 31 individuals (The PRECICE™ intramedullary nail study)

Abstract

Purpose: We studied 31 individuals whose femur or tibia was elongated with the PRECICE™ intramedullary lengthening nail in a protocol-controlled, multicentric, prospective series. Only skeletally mature individuals were included in the study. Materials and Methods: The protocol entailed 2-year follow-up after consolidation of the regenerate new bone in the distraction gap. Since the external remote controller (that powers the nail's internal rotating magnet) must be within a predetermined distance from the implant, body weight limitations applied to the individuals. Similarly, a history of active or prior bone infection in the involved limb segment, an offset medullary canal that could not be successfully reamed for the implant, an angular deformity that precluded insertion of a straight device, and any potential limitation on regenerate new bone formation (such as metabolic bone disease or vascular compromise) were causes for exclusion. The mean age ± standard deviation was 24.3 ± 15.0, and the median age was 18 years. There were 20 males and 11 females in the series, with 21 Caucasians, 5 Hispanics, and 5 African-American individuals. The mean body mass index was 24.2 ± 4.7. Twentythree (74.2%) cases involved the femur and 8 (25.8%) involved the tibia. Results: One participant died of medical causes during the study period, and one participant was lost to follow-up, but 29 of 29 participants followed at least to consolidation achieved union (100%) although one of these participants was treated with a supplementary cancellous bone graft and another participant was converted to trauma nail before consolidation, to permit full weight-bearing as a stimulus to regenerate consolidation. On an average, participants achieved 96.3% ± 23.2% of the preoperative target lengthening (3.5 cm; range 1.8–6.0 cm) over an average of 48.5 ± 15.6 days. The average time to full weightbearing (permitted when the regenerate was consolidated on three sides) was 141.1 ± 80.7 days. The knee joint, at consolidation, lost an average of 6.5° of flexion and 0.3° of extension. The ankle lost an average of 1.4° of dorsiflexion and 5.4° of plantar flexion. The hip joint lost, on average, 2° of flexion, and gained 1.6° of extension. There was one deep infection involving the implant, successfully treated with intravenous antibiotics and superficial debridement. Nearly 25.8% of the participants had pain issues during lengthening, often over prominent hardware. In one participant, the nail failed to elongate during lengthening at home and had to be exchanged. One interlock screw broke. The internal components separated during implant extraction in the one subject had his nail exchanged by a trauma nail. Only 17 participants exited the protocol by presenting to clinic for evaluation 2 years after consolidation. None experienced significant deterioration of outcome. Conclusion: The PRECICE™ IM nail is a well-tolerated, reliable, fully implantable limb lengthening device that will accurately elongate the femur or tibia in a variety of causes of limb length inequality, with a low implant failure rate, and few complications.

Keywords

• Leg lengthening
• lengthening intramedullary nail
• limb lengthening
• magnetical