Eberle Sebastian, Gerber Claus, von Oldenburg Geert, Hungerer Sven, Augat Peter
Institute of Biomechanics, Trauma Center Murnau, Prof. Küntscher Str. 8, 82418, Murnau, Germany.
Clin Orthop Relat Res. 2009 Aug;467(8):1972-80. doi: 10.1007/s11999-009-0800-3. Epub 2009 Mar 31.
The choice of the appropriate implant continues to be critical for fixation of unstable hip fractures. Therefore, the goal of this study was to develop a numerical model to investigate the mechanical performance of hip fracture osteosynthesis. We hypothesized that decreasing fracture stability results in increasing load share of the implant and therefore higher stress within the implant. We also investigated the relationship of interfragmentary movement to the fracture stability. A finite element model was developed for a cephalomedullary nail within a synthetic femur and simulated a pertrochanteric fracture, a lateral neck fracture, and a subtrochanteric fracture. The femur was loaded with a hip force and was constrained physiologically. The FE model was validated by mechanical experiments. All three fractures resulted in similar values for stiffness (462-528 N/mm). The subtrochanteric fracture resulted in the highest local stress (665 MPa), and the pertrochanteric fracture resulted in a lower stress (621 MPa) with even lower values for the lateral neck fracture (480 MPa). Thus, intramedullary implants can stabilize unstable hip fractures with almost the same amount of stiffness as seen in stable fractures, but they have to bear a higher load share, resulting in higher stresses in the implant.
对于不稳定型髋部骨折的固定而言，选择合适的植入物仍然至关重要。因此，本研究的目的是建立一个数值模型，以研究髋部骨折骨接合术的力学性能。我们假设骨折稳定性降低会导致植入物分担的负荷增加，从而使植入物内部应力升高。我们还研究了骨折块间移动与骨折稳定性之间的关系。针对一根合成股骨内的髓内钉建立了有限元模型，并模拟了转子间骨折、外侧颈骨折和转子下骨折。对股骨施加髋部作用力，并进行生理约束。通过力学实验对有限元模型进行了验证。所有三种骨折的刚度值相似（462 - 528 N/mm）。转子下骨折导致的局部应力最高（665 MPa），转子间骨折的应力较低（621 MPa），外侧颈骨折的应力更低（480 MPa）。因此，髓内植入物能够以与稳定骨折几乎相同的刚度稳定不稳定型髋部骨折，但它们必须承担更高的负荷分担，从而导致植入物内部应力更高。
