一体化假肢与传统假肢生物力学模型的比较

Comparative biomechanical researches of monolimb and traditional prosthesis

目的:应用有限元方法分析一体化假肢与传统假肢的应力分布特点,探讨一体化假肢的应力缓冲作用。方法:基于针对同一膝下截肢者设计的一体化假肢和传统假肢的真实几何构形,分别建立三维有限元模型,同时考虑残肢和接受腔之间的接触作用,选用摩擦系数为0.5。施加HeelOff步态时相的载荷,比较分析一体化假肢和传统假肢模型的应力分布。结果:①一体化假肢和传统假肢模型中,接受腔的应力分布基本一致,各区域的应力值也较为接近。接受腔和假腿的过渡区域都为高应力区;两个模型在此区域的应力值则差异较大,一体化假肢的最大应力分别为16.1MPa和17.8MPa,而传统假肢则达到23.7MPa和28.6MPa,传统假肢的应力分别高于一体化假肢47.2%和60.7%。高应力区的面积也呈现出传统假肢明显大于一体化假肢的现象,传统假肢的高应力区从前端和后端一直延伸到外侧面。②两个模型软组织表面的应力分布规律基本一致,最大正应力和最大剪应力都出现在正面末端。传统假肢模型中残肢表面的最大正应力和最大剪应力分别为581.2kPa和178.7kPa,一体化假肢模型中残肢表面的最大正应力和最大剪应力分别为416.8kPa和118.3kPa。结论:一体化假肢的外形美观,且价格低廉,轻便,易于截肢者接受。一体化假肢在接受腔和假腿的过渡区域产生较为明显的应力缓冲作用,也降低了残肢表面的应力,生物力学性能明显优于传统假肢,将成为未来假肢发展的一个重要方向。

AIM： To analyze the stress distributions of monolimb and traditional prosthesis using finite element method, and discuss the stress damping of the monolimb. METHODS： Based on the real geometrical shapes of the monolimb and the traditional prosthesis designed for the same below-knee amputee, two three-dimensional finite element models were established. Contact between the limb stump and the socket was taken into the consideration of setting the coefficient of friction as 0.5. The loads corresponding to the stance subphase of Heel Off were applied to compare the stress distributions of the monolimb and the traditional prosthesis. RESULTS： ①The monolimb and the traditional prosthesis demonstrated the similar stress distributions of sockets and the high stress of the border sections between the sockets and the prosthetic shanks. However the stresses of the posterior and anterior area of border sections in the traditional prosthesis were 47.2% and 60.7% higher than those in the monolimb （16.1 MPa, 17.8 MPa; 23,7 MPa, 28.6 MPa）. And the high stress area in the monolimb was obviously smaller than in the traditional prosthesis, in which the area extended from the anterior and posterior ends to the lateral surface, ②The stress distributions of the soft tissues were also similar in the two models, And both the maximum normal stresses and the maximum shear stresses located at the distal anterior of soft tissues in two models. The maximum normal and shear stresses of the stumps in the traditional prosthesis were 581.2 kPa and 178,7 kPa, respectively; while the values in the monolimb were 416,8 kPa and 118.3 kPa, respectively. CONCLUSION： Compared with traditional prosthesis, monolimb is more economical, good-looking and portable, so that amputees prefer to monolimb. The monolimb appears very evident stress damping in the border section between the socket and the prosthetic shank; And the stresses of the stump in the monolimb are lower than those in the traditional prosthesis. Owing to the obvious biomeehanieal capability, monolimb will be the guide of prosthesis development.