Single lag screw cephalomedullary nail angle-anatomy mismatch is associated with immediate postoperative malreduction after intertrochanteric hip fracture fixation.

Abstract

To determine whether cephalomedullary nail (CMN) angle was associated with malreduction after intertrochanteric (IT) fracture fixation. Secondarily, to explore if CMN angle was associated with fixation failure (FF). A retrospective comparative review was conducted of patients ≥ 65 years old with low energy falls and OTA/AO 31-A fractures treated with a CMN from 12/01/2016-06/30/2024 at a single academic institution (four hospitals). The primary outcome was immediate postoperative malreduction (IPM)-the absolute difference between post-fixation neck-shaft angle (NSA) and native contralateral NSA being ≥ 3°. The secondary outcome was FF. Univariate analyses compared IPM between 125° and 130° CMNs. Multivariable regression was performed to determine if CMN angle was associated with IPM, and as an exploratory analysis, FF. A total of 277 patients were included with follow-up of 18.2 ± 15.1 months. The 125° CMN group had significantly greater age, body mass index (BMI), and American Society of Anesthesiologists score (ASA). There was a higher incidence of IPM with 125° CMNs (p = 0.02). Among patients with native NSA ≥ 130°, those treated with a 125° nail had significantly higher IPM incidence (p = 0.01). Mean IPM did not differ by CMN angle. Logistic regression found that BMI (OR 1.06, p = 0.04) and 125° CMN angle (OR 1.82, p = 0.05) were associated with IPM. FF rates were similar between CMN angle groups, but failures had greater varus IPM than non-failures (p = 0.02). In the exploratory FF regression model, CMN angle and varus IPM were not associated with failure, while larger native NSA was associated with FF (OR 1.16, p < 0.001). 125° and 130° nails achieved similar mean fracture alignment, yet 125° nails were more frequently associated with varus malreduction, especially with native valgus neck-shaft angles. After adjusting for confounders, higher BMI and 125° nails were associated with malreduction but not with fixation failure.