Does Modern Nail Geometry Affect Positioning in the Distal Femur of Elderly Patients With Hip Fractures? A Comparison of Otherwise Identical Intramedullary Nails With a 200 Versus 150 cm Radius of Curvature

Objective: To compare implant positioning in the distal femur between 2 cohorts of elderly patients treated for a hip fracture with a long 200- or 150-cm radius of curvature (ROC) cephalomedullary nail. We theorized that the 150-cm ROC nails would more closely approximate the femoral bow and result in fewer implant-related complications. Design: Retrospective Comparative Study. Setting: Single Level II Trauma Center. Participants: Fifty-eight geriatric patients with a hip fracture (26 in 200-cm nail cohort and 32 in 150-cm nail cohort). Intervention: Long cephalomedullary nailing using single hip fracture nail and instrumentation system (InterTAN) before and after transition from a 200- to 150-cm ROC long hip nail. Main Outcome Measures: Anteroposterior position of distal nail tip on intraoperative lateral radiograph (where 0.50 indicates midaxial, perfectly central placement) and implant-related complications (anterior cortical abutment, perforation, or fracture). Results: The average position of nails with a 150-cm ROC was closer to the midaxial line of the distal femur compared with 200-cm nails (0.63 vs. 0.55, P = 0.02). Only 1 of 26 (3.8%) 200-cm ROC nails was placed at the midaxial line and none were posterior, whereas 9 of 32 (28%) 150-cm ROC nails were positioned at or posterior to this line (P = 0.006). Only 1 nail with a 150-cm ROC abutted the distal femur's anterior cortex compared with 3 in the 200-cm cohort-including one that caused a fracture. Conclusions: Femoral nails with a 150-cm ROC more closely approximate the femoral bow of geriatric hip fracture patients than 200-cm ROC nails, appearing less likely to cause complications such as anterior cortical abutment, perforation, or fracture.