Variables Associated With Lag Screw Sliding After Single-Screw Cephalomedullary Nail Fixation of Intertrochanteric Fractures

Objectives: To evaluate variables associated with lag screw sliding after single-screw cephalomedullary nail (CMN) fixation of intertrochanteric femur fractures. Design: Retrospective cohort study. Setting: Level-one trauma center. Patients/Participants: One hundred fifty-eight intertrochanteric fractures in patients older than 65 years with an average follow-up of 22 months. Intervention: Single-screw CMN fixation. Main Outcome Measurements: Lag screw sliding and revision surgeries. Results: The average amount of lag screw sliding was 5 +/- 5 mm (range, 0-21 mm). Lag screw sliding was greater with unstable fracture patterns (mean difference 2 mm, 95% confidence interval 0.4-3.5 mm,P= 0.01) and calcar gapping >4 mm (mean difference 3.7 mm, 95% confidence interval 2-5 mm,P< 0.01). No association was found between lag screw sliding and age, female gender, implants, long versus short nails, distal interlock screw use, postoperative neck-shaft angle, or tip-apex distance (P> 0.05). Revision surgeries were performed in 6 (4%) patients. Indications included symptomatic lag screw removal (n = 2), avascular necrosis (n = 1), cutout (n = 1), loss of reduction (n = 1), and perimplant fracture (n = 1). Conclusions: Unstable fracture patterns are unavoidable; however, careful attention to calcar reduction and selection of dual-screw CMN implants may minimize lag screw sliding and its detrimental effects on outcomes.