Impact of nail-to-medullary canal ratio on proximal femoral shortening in osteoporotic pertrochanteric fractures".

Abstract

Background: Proximal femoral shortening (PFS) is a common but often under-recognized mechanical complication following proximal femoral nailing (PFN) for pertrochanteric fractures and may adversely affect hip biomechanics and functional outcomes. The objective of this study was to determine whether the nail-to-medullary canal ratio (NMR) influences postoperative PFS in patients with osteoporotic pertrochanteric fractures treated with PFN, and to identify risk factors associated with increased shortening.

Hypothesis: We hypothesized that a higher nail-to-medullary canal ratio would be associated with reduced proximal femoral shortening after PFN in osteoporotic pertrochanteric fractures.

Patients and methods: This retrospective cohort study included 128 patients aged >60 years with osteoporotic pertrochanteric fractures (OTA/AO 31A1-31A3) treated using a short Gamma3 nail. PFS was quantified by comparing the operated hip with the contralateral uninjured side and calculating horizontal, vertical, and resultant z-vector components. Independent variables included age, sex, NMR, fracture type, and reduction quality. Multivariable regression analysis was used to identify predictors of PFS, with subgroup analyses performed for stable versus unstable fractures. Factors associated with reoperation were assessed using logistic regression.

Results: The mean proximal femoral shortening was 5.02 ± 4.56 mm. Mild (5-10 mm) and severe (≥10 mm) shortening occurred in 18.8% and 17.2% of patients, respectively. In multivariable analysis, a higher NMR was independently associated with reduced PFS. Unstable fracture patterns (AO/OTA 31A2-31A3) and reduction quality other than good were associated with significantly greater shortening. Subgroup analysis demonstrated that the protective effect of a higher NMR was present in unstable fractures but not in stable fractures. Implant failure occurred in 7 patients and was not associated with NMR.

Discussion: The use of nails that better fill the intramedullary canal may help prevent PFS, particularly in unstable pertrochanteric fractures. Fracture stability and reduction quality remained key determinants of postoperative shortening, whereas nail-to-medullary canal ratio was not related to implant failure.

Level of evidence: III; retrospective cohort study.