Early Experience of Femoral Lengthening with the FITBONE Nail in Adolescents

Intramedullary limb lengthening nails are increasingly used in patients nearing skeletal maturity. Following the temporary withdrawal of magnetically driven systems, the electrically powered FITBONE nail has been used at our institution since March 2021. This study aims to present the early experience of this nail with particular attention to complications, regenerative healing, and the learning curve.

A single-center retrospective study was performed, including adolescent patients who underwent femoral lengthening with antegrade or retrograde FITBONE nails and progressed to full weight-bearing (FWB). Outcome measures included length gained, distraction index (DI), weight-bearing index (WBI), mechanical axis parameters, complications, and patient-reported outcomes using the Paediatric Quality of Life (PedsQL) Questionnaire.

A total of 15 (eight males, seven females) patients with a mean age of 16.9 years, with varied diagnoses of leg length discrepancy (LLD), were analysed. Mean length gained was 39 mm with a mean DI of 0.75 mm/day. Weight-bearing index in these patients, on average, was 57.4 days/cm lengthened. Four complications were observed, including two nonunions (both successfully treated) and two knee subluxations. Mechanical axis deviation improved from 12.1 to 7 mm on average. A significant reduction in WBI was observed with increasing surgical experience (Spearman's ρ = -0.58, p = 0.02). No significant changes were detected in PedsQL scores pre- and post-operatively (p > 0.05 for all domains).

Femoral lengthening using the FITBONE nail in adolescents approaching skeletal maturity is an effective and relatively safe procedure, with complication rates and outcomes comparable to other intramedullary lengthening systems. A learning curve was evident, reflected by earlier progression to FWB without an increase in complications.

Surgeons experienced with intramedullary limb lengthening can expect outcomes and complication profiles comparable to other motorised nail systems when using FITBONE. However, the relatively large barrel diameter (12 mm) may limit its use in patients with narrow femoral canals and should be considered during patient selection.