Peleg Eran, Mosheiff Rami, Liebergall Meir, Mattan Yoav
Biomedical Engineering, The Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Clin Biomech (Bristol). 2006 Nov;21(9):963-8. doi: 10.1016/j.clinbiomech.2006.06.001. Epub 2006 Aug 8.
Decreasing the length of the side plate of the dynamic hip screw would theoretically allow a smaller surgical incision, a shorter surgical time, decreased operative blood loss and minimal periosteal stripping. A new design of a very short plate dynamic hip screw based on two diagonal screws has been developed. Our study compares the new design and the four-hole side plate in respect to mechanical properties and bio-mechanical outcomes utilizing the Finite Element Analysis method.
Four pairs of fresh frozen cadaveric femora were extracted from male corpses aged 25-43 years (mean 34.8). One femur of each pair was fixated by means of the new system and the other by means of the conventional design. Mechanical loading was applied to all four pairs. The decline which occurred during the periodical loadings and the breakage loads of fixated bones were measured. Mechanical performance and probability of failure was assessed by conducting a mathematical analysis using the finite element method.
The average deflection under excessive cyclic loading was 33% higher in the bones fixated with the very short plate-dynamic hip screw device than in those fixated with the conventional dynamic hip screw. The average load failure during the collapse-loading test was 3120N for the very short plate-dynamic hip screw as compared to 4160N for the regular device. Mechanical testing did not provide decisive results regarding failure. The mathematical analysis performed indicated that the maximal stress in the very short plate-dynamic hip screw reached values 3-4-fold higher than in the regular dynamic hip screw.
Although the new design offers a minimally invasive approach to subtrochanteric femur fracture fixation, it was found to have insufficient biomechanical performance resulting in high probability of mechanical failure. The authors believe that the finite element method may have the potential to serve as an additional clinical tool for performing surgical preplanning and assist in decision making.
理论上，缩短动力髋螺钉侧板的长度可减小手术切口、缩短手术时间、减少术中失血并使骨膜剥离降至最低。基于两根对角螺钉设计出了一种新型极短钢板动力髋螺钉。我们的研究采用有限元分析方法，比较了这种新设计与四孔侧板在力学性能和生物力学结果方面的差异。
从25 - 43岁（平均34.8岁）男性尸体中提取四对新鲜冷冻股骨。每对中的一根股骨用新系统固定，另一根用传统设计固定。对所有四对股骨施加机械载荷。测量固定骨骼在周期性加载期间的位移下降情况以及断裂载荷。使用有限元方法进行数学分析，评估力学性能和失效概率。
用极短钢板动力髋螺钉装置固定的骨骼在过度循环加载下的平均位移比用传统动力髋螺钉固定的骨骼高33%。在塌陷加载试验中，极短钢板动力髋螺钉的平均载荷失效为3120N，而常规装置为4160N。力学测试未提供关于失效的决定性结果。所进行的数学分析表明，极短钢板动力髋螺钉中的最大应力比常规动力髋螺钉中的应力高3 - 4倍。
尽管新设计为股骨转子下骨折固定提供了一种微创方法，但发现其生物力学性能不足，导致机械失效的可能性很高。作者认为有限元方法可能有潜力作为一种额外的临床工具，用于进行手术预规划并协助决策。
