Lag Screw Slide Persists Despite Static Locking in Reverse Obliquity Intertrochanteric Hip Fractures Treated with a Single Lag Screw Cephalomedullary Nail.

Abstract

To evaluate factors influencing slide in statically-locked single lag screw cephalomedullary nail (CMN) constructs for reverse obliquity (RO) fractures. Design: Retrospective comparative study. A multi-center academic urban hospital system (4 hospitals). Patients with an RO fracture (OTA/AO 31A3) treated with a CMN (Gamma or TFNA) and statically-locked single lag screw from 2014 to 2024, with at least one follow-up radiograph (minimum three months or documentation of healing). Lag screw sliding was measured as the difference in screw position between immediate postoperative imaging and final follow-up radiographs. Tip-to-head distance (ΔTHD) and screw protrusion ratio (ΔPR) were recorded. Patients were grouped as <5mm, 5-10mm, or >10mm slide. Comparisons included fracture subtype, nail brand, angle, and length. Bivariate analyses tested associations with slide. Of the 219 patients identified with a 31A3 type fracture, 85 (38.8%) met inclusion criteria. The average age was 81.0 (±9.3) years with 65 (76.5%) females. Mean radiographic follow-up was 19.9 months, with a follow-up range of 74-2,576 days. The mean slide was 7.8mm (±5.2mm). 74 patients (87.1%) had slide >2mm. ΔTHD was negligible (-0.1 ± 7.0mm), and ΔPR 0.2 (±0.1) significantly exceeded zero (p < 0.001). Neither nail length (Short: 9.4 ± 5.3mm vs. Long: 7.1 ± 5.0mm, p = 0.083), nail angle, (125°: 8.0 ± 5.4mm vs 130°: 6.5 ± 4.0mm; p = 0.286), nor nail brand had a significant effect (Gamma: 7.6 ± 5.1mm vs TFNA: 9.1 ± 6.2mm; p = 0.921). Fracture subtype (31A3.1: 9.1 ± 6.1mm vs 31A3.2: 10.4 ± 5.1mm vs 31A3.3: 6.9mm ± 4.6mm; p = 0.114) and demographic factors (p > 0.05) were not significantly associated with slide severity. Surgeons should expect some degree of lag screw slide and subsequent proximal fragment displacement when a Gamma nail or TFNA nail cephalomedullary nail is used for a reverse obliquity fracture, even when statically locked. Level III.