Kraemer W J, Hearn T C, Powell J N, Mahomed N
Department of Orthopaedic Surgery, Sunnybrook Health Science Centre, University of Toronto, Canada.
Clin Orthop Relat Res. 1996 Nov(332):71-9. doi: 10.1097/00003086-199611000-00010.
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.
转子下节段性骨折与骨不连、骨畸形愈合及植入物失败的高发生率相关。尽管对于这些骨折，有人主张使用第二代带股骨头近端交锁的髓内钉，但临床研究中短的第二代髓内钉末端的股骨干骨折引发了对这些植入物力学适用性的担忧。目前尚无关于这些新型植入物固定强度及失效模式的生物力学数据。本研究比较了用3种现有植入物固定的转子下节段性骨折的强度及失效模式。获取了18具解剖学标本股骨。所测试的3种植入物为Russell-Taylor重建钉、短髓内髋螺钉和长髓内髋螺钉。对每根股骨进行器械植入并制造转子下节段性骨折。在材料测试系统中对股骨施加负荷。重建钉组的强度（2869±210 N）显著高于短髓内棒髋螺钉组（2330±490 N）和长髓内棒髋螺钉组（2181±244 N）。植入物的失效模式为：重建钉的螺钉穿出股骨头；短髓内髋螺钉的股骨干骨折；长髓内髋螺钉的植入物弯曲。本研究表明，在所测试的植入物中，重建钉是转子下节段性骨折的最佳植入物。较低负荷下的植入物弯曲和股骨干骨折使得2种髓内棒髋螺钉植入物不太适用。
