Short cephalomedullary nail toggle: a closer examination

OBJECTIVES: In patients with wide femoral canals, an undersized short nail may not provide adequate stability, leading to toggling of the nail around the distal interlocking screw and subsequent loss of reduction. The purpose of this study was to identify risk factors associated with nail toggle and to examine whether increased nail toggle is associated with increased varus collapse. DESIGN: Retrospective cohort study. SETTING: Level 1 and level 3 trauma center. PATIENTS/PARTICIPANTS: Seventy-one patients with intertrochanteric femur fractures treated with short cephalomedullary nails (CMN) from October 2013 to December 2017. INTERVENTION: Short CMN. MAIN OUTCOME MEASUREMENTS: Nail toggle and varus collapse were measured on intraoperative and final follow-up radiographs. Risk factors for nail toggle including demographics, fracture classification, quality of reduction, Dorr type, nail/canal diameter ratio, lag screw engaging the lateral cortex, and tip-apex distance (TAD) were recorded. RESULTS: On multivariate regression analysis, shorter TAD (P = .005) and smaller nail/canal ratio (P < .001) were associated with increased nail toggle. Seven patients (10%) sustained nail toggle >4 degrees. They had a smaller nail/canal ratio (0.54 vs 0.74, P < .001), more commonly Dorr C (57% vs 14%, P = .025), lower incidence of lag screw engaging the lateral cortex (29% vs 73%, P = .026), shorter TAD (13.4 mm vs 18.5 mm, P = .042), and greater varus collapse (6.2 degrees vs 1.3 degrees, P < .001) compared to patients with nail toggle < 4 degrees. CONCLUSIONS: Lower percentage nail fill of the canal and shorter TAD are risk factors for increased nail toggle in short CMNs. Increased nail toggle is associated with increased varus collapse. Level of evidence: Therapeutic Level III