Fixation of segmental subtrochanteric fractures. A biomechanical study.

Segmental subtrochanteric fractures have been associated with high rates of malunion, nonunion, and implant failure. Although the use of second generation intramedullary nails with proximal interlocking in the femoral head has been advocated for these fractures, shaft fractures at the tip of short second generation intramedullary rod nails in clinical studies raise concerns about the mechanical suitability of these implants. No biomechanical data are available on the strength of fixation and mode of failure of these newer implants. This study compares the strength and failure mode of segmental subtrochanteric fractures stabilized with 3 current implants. Eighteen anatomic specimen femurs were obtained. The 3 implants tested were the Russell-Taylor reconstruction nail, a short intramedullary hip screw, and a long intramedullary hip screw. Each femur was instrumented and a segmental subtrochanteric fracture was created. The femurs were loaded in a Materials Testing System. The strength of the reconstruction nail group (2869 +/- 210 N) was significantly greater than for the short intramedullary rod hip screw (2330 +/- 490 N), and the long intramedullary rod hip screw (2181 +/- 244 N). The failure modes for the implants were: screw cut out of the femoral head for the reconstruction nail; fracture of the femoral shaft for the short intramedullary hip screw, and implant bending for the long intramedullary hip screw. This study suggests that the reconstruction nail is the superior implant for segmental subtrochanteric fractures of those tested. Implant bending and shaft fractures at lower loads make the 2 intramedullary rod hip screw implants less suitable.