Department of Orthopaedic Surgery, Virginia Commonwealth University, PO Box 980153, Richmond, VA 23298-0153, USA.
Clin Orthop Relat Res. 2010 Feb;468(2):497-503. doi: 10.1007/s11999-009-1034-0. Epub 2009 Aug 11.
The incidence of femur fracture around total hip arthroplasties continues to increase at substantial cost to society. These fractures are frequently associated with a loose femoral component. Consequently, we sought to test whether femoral component loosening predisposes to periprosthetic femoral fracture. Because many periprosthetic femoral fractures are spiral in nature, we evaluated the torsional characteristics of the implanted femur in which the only design variable was instability of the femoral component. We used synthetic (polyurethane) (n = 15) and paired cadaveric femora (n = 10) with specimens divided into two groups: well-fixed and loose cemented stems. Each specimen was tested mechanically in internal rotation until failure. For the synthetic specimens, torque to failure was reduced by 38%, whereas stiffness was decreased 54% for the loose group compared with the well-fixed group. For the cadaveric specimens, torque to failure was reduced by 58%, whereas stiffness decreased 70% for the loose group compared with the well-fixed group. Fracture patterns were similar between synthetic and cadaveric femora with a proximal spiral pattern in loose specimens and more distal fracture patterns with well-fixed stems. Based on our data, patients with loosened femoral components are at risk for fracture at a substantially lower torque than those with well-fixed components.
全髋关节置换术后股骨骨折的发病率持续上升，给社会带来了巨大的经济负担。这些骨折通常与股骨部件松动有关。因此，我们试图测试股骨部件松动是否会导致假体周围股骨骨折。由于许多假体周围股骨骨折呈螺旋形，我们评估了植入股骨的扭转特性，其中唯一的设计变量是股骨部件的不稳定性。我们使用合成（聚氨酯）（n = 15）和配对的尸体股骨（n = 10），将标本分为两组：固定良好和松动的水泥固定干。每个标本在内旋转下进行机械测试，直到失效。对于合成标本，失效扭矩降低了 38%，而对于松动组，与固定良好组相比，刚度降低了 54%。对于尸体标本，失效扭矩降低了 58%，而对于松动组，与固定良好组相比，刚度降低了 70%。松动标本的骨折模式与合成和尸体股骨相似，呈近端螺旋形，而固定良好的干则呈更远端的骨折模式。根据我们的数据，松动股骨部件的患者在明显较低的扭矩下就有骨折的风险，而固定良好的患者则没有。
