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

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OBJECTIVES: To evaluate factors influencing slide in statically locked single lag screw cephalomedullary nail constructs for reverse obliquity (RO) fractures. DESIGN: Retrospective comparative study. SETTING: A multicenter academic urban hospital system (4 hospitals). PATIENT SELECTION CRITERIA: Patients with an RO fracture (OTA/AO 31A3) treated with a cephalomedullary nail (Gamma or TFNA) and statically locked single lag screw from 2014 to 2024, with at least 1 follow-up radiograph (minimum 3 months or documentation of healing). OUTCOME MEASURES AND COMPARISONS: 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 <5 mm, 5-10 mm, or >10 mm slide. Comparisons included fracture subtype, nail brand, angle, and length. Bivariate analyses tested associations with slide. RESULTS: 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%) women. Mean radiographic follow-up was 19.9 months, with a follow-up range of 74-2576 days. The mean slide was 7.8 mm (±5.2 mm). In total, 74 patients (87.1%) had slide >2 mm. ΔTHD was negligible (-0.1 ± 7.0 mm) and ΔPR 0.2 (±0.1) significantly exceeded 0 ( P < 0.001). Neither nail length (Short: 9.4 ± 5.3 mm vs. Long: 7.1 ± 5.0 mm, P = 0.083), nail angle (125 degrees: 8.0 ± 5.4 mm vs. 130 degrees: 6.5 ± 4.0 mm; P = 0.286), nor nail brand had a significant effect (Gamma: 7.6 ± 5.1 mm vs. TFNA: 9.1 ± 6.2 mm; P = 0.921). Fracture subtype (31A3.1: 9.1 ± 6.1 mm vs. 31A3.2: 10.4 ± 5.1 mm vs. 31A3.3: 6.9 mm ± 4.6 mm; P = 0.114) and demographic factors ( P > 0.05) were not significantly associated with slide severity. CONCLUSIONS: 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 OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

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