Combined lengthening for acquired leg length discrepancy: Are there advantages of hydroxyapatite-coated intramedullary nails?

Introduction The aim of this multicenter prospective study was to analyze the outcomes of bone lengthening by external fixator associated with flexible intramedullary nailing (FIN) in acquired limb length discrepancy (LLD). Hypothesis Hydroxyapatite (HA)-coated FIN enables reduced External Fixation Index in limb lengthening for acquired leg length discrepancies in comparison to non-HA-coated FIN. Material and methods This study included 54 patients (mean age, 17.9 years) operated on for femoral or tibial lengthening by combined technique (External fixator with FIN) for acquired length discrepancy. Titanium non-HA-coated FIN (29 cases) or HA-coated FIN (25 cases) were used. The factors that might influence external fixation index, complication occurrence and outcome were analyzed: age, amount of lengthening, nail diameter, HA-coating vs. non-HA-coated nails. Results The mean External Fixation Indexes (EFI) of groups compared for non-HA-coated nails vs. HA-coated nails were not significantly different: 26.5 d/cm and 27.2 d/cm in femoral lengthening and 34.9 d/cm and 31.7 d/cm in tibial lengthening. Positive correlation between the “nail diameter/inner distance between cortices at osteotomy site” ratio and EFI in tibial lengthening was revealed (p = 0.034). The nail types and the “nail diameter/medullary canal diameter” ratio interact and have significant simultaneous effect on EFI in femoral lengthening (p = 0.021). Discussion The results of this study revealed no differences with regards to EFI using HA-coated or non-HA-coated titanium FIN in lengthening for acquired leg-length discrepancies. Combined technique allowed reduced EFI and avoided major complications. Both non-HA-nail and HA-coated nail lengthening provided good and excellent outcomes. Level of evidence III; (controlled trial without randomization) prospective comparative study.