Taheri Nooshin S, Blicblau Aaron S, Singh Manmohan
Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia.
J Orthop Sci. 2011 Nov;16(6):805-13. doi: 10.1007/s00776-011-0145-0. Epub 2011 Aug 30.
Internal fixation with dynamic hip screw is a choice of treatment for hip fractures to stabilize a femoral fracture. Choosing the proper implant and its material has a great effect on the healing process and failure prevention. The purpose of this analysis was to assess biomechanical behavior of dynamic hip screw with two different materials implanted in the femur during fall and gait.
A 3D finite element model of an intact femur and a 3D implant within the same femur were developed. A finite element analysis was carried out to establish the effect of load conditions and implant material properties on biomechanical behavior of the dynamic hip screw after internal fixation. Two load configurations are chosen: one simulating the stance phase of the normal gait cycle, and the other replicating a low-energy fall. The implanted femur was investigated with two different materials for the dynamic hip screw: stainless steel and titanium alloy.
During stance, more stress is placed on the implanted femur compared with the intact femur. During a fall, the implanted femur is in a greater state of stress, which mostly occurs inside the dynamic hip screw. Titanium alloy decreases stress levels by an average of 40% compared with stainless steel. However, deformation is slightly reduced with a stainless steel dynamic hip screw during both load cases.
After internal fixation, dynamic hip screw generates greater stresses within the implanted femur compared with the intact femur under the same loading conditions. A titanium alloy implant appears to undergo less stress from a low-energy fall compared with stainless steel and can be considered the preferred implant material. The critical parts of the dynamic hip screw are the forth distal screw and the plate.
动力髋螺钉内固定是治疗髋部骨折以稳定股骨骨折的一种选择。选择合适的植入物及其材料对愈合过程和预防失败有很大影响。本分析的目的是评估在跌倒和步态过程中，两种不同材料的动力髋螺钉植入股骨后的生物力学行为。
建立了完整股骨的三维有限元模型以及同一股骨内的三维植入物模型。进行有限元分析，以确定载荷条件和植入物材料特性对动力髋螺钉内固定后生物力学行为的影响。选择两种载荷配置：一种模拟正常步态周期的站立期，另一种模拟低能量跌倒。对植入股骨的动力髋螺钉采用两种不同材料进行研究：不锈钢和钛合金。
在站立期间，与完整股骨相比，植入股骨承受的应力更大。在跌倒过程中，植入股骨处于更大的应力状态，这种应力大多出现在动力髋螺钉内部。与不锈钢相比，钛合金可使应力水平平均降低40%。然而，在两种载荷情况下，不锈钢动力髋螺钉的变形略有减小。
内固定后，在相同载荷条件下，与完整股骨相比，动力髋螺钉在植入股骨内产生更大的应力。与不锈钢相比，钛合金植入物在低能量跌倒时承受的应力似乎更小，可被视为首选的植入物材料。动力髋螺钉的关键部位是第四枚远端螺钉和钢板。
