Bone Healing Index and Complications of a Magnetic Internal Lengthening Nail: A Retrospective Series of 286 Bone Lengthening Events.

BACKGROUND

The time required to form new bone is a critical aspect of bone lengthening but is not constant depending on the osteotomy location. The objective of this study was to establish the bone healing index (BHI) after femur and tibia bone lengthening procedures. Additional objectives included identifying procedure-related complications and implant reliability.

METHODS

A retrospective analysis was conducted on all consecutive internal lengthening nails (Precice; Nuvasive) implanted in the femur or tibia at a single institution from September 2012 to November 2019. Groups were delineated by surgical approach (antegrade femur [AF], retrograde femur [RF], or antegrade tibia [AT]). The primary outcome was the BHI (days to consolidate regenerate per centimeter bone lengthened). Additional outcomes included iatrogenic bone deformity, implant complications, and nail reliability. Comparative analysis of demographic characteristics and complications was conducted using chi-square tests, and BHI was compared using independent t-tests. Multivariate analysis was used to evaluate independent outcomes among the groups. Statistical significance was set at P < 0.05.

RESULTS

Of 286 bone lengthening events (164 AF, 67 RF, 55 AT), BHI was significantly lower for AF at 24.5 ± 9.5 d/cm than for RF at 33.5 ± 14.5 d/cm and AT at 41.0 ± 17.4 d/cm (P = 0.001) and lower for RF than for AT (P = 0.012). After multivariate analysis, nail approach (AF), younger age (≤16), and lengthening for stature (versus deformity) were significantly associated with a lower BHI. Lengthening > 3 cm was also associated with better BHI. Iatrogenic deformity was induced in 8/164 = 4.9% AF, 2/67 = 3.0% RF, and 5/55 = 9.1% AT. Implant reliability was 92.7% for AF, 93.1% for RF, and 94.8% for AT. Complications requiring another surgery were observed in 39 of 286 (13.6%), and failure to achieve the lengthening goal was observed in 1 of 286 (0.3%).

CONCLUSION

AF lengthening, younger age, stature lengthening, and lengthening > 3 cm lead to better bone healing indices using the Precice internal lengthening nail. Complications and iatrogenic deformity can be partially mitigated with surgeon-controlled decisions (surgical approach, blocking screws, distraction rate, weight-bearing restrictions) and rarely lead to a failure in achieving the lengthening goal if treated promptly.

LEVEL OF EVIDENCE

III.