基于激光快速成型技术正常步态下骨盆应力分布的三维光弹分析

背景：三维有限元技术是对应力真实情况的数字模拟，光弹技术可以真实显示测试模型的整体应力分布。 目的：使用激光快速成型技术制备骨盆光弹模型，以三维光弹法研究正常步态下髋臼区域的应力分布特征并与使用有限元法获得的数据进行比较。 方法：使用激光快速成型技术制备骨盆光弹模型，包括第5腰椎及双侧股骨近端。在股骨上施加体质量负荷，通过固定在髂骨翼前部髂前上棘髂后上棘及耻骨下支的钢丝施加负荷模拟4组肌群，假定股骨内收15°，支撑相4个子步态股骨从屈曲22°到后伸12°。应力冻结后，沿弓状线切片。在偏振光场中观察等差线及等倾线。 结果与结论：①应力集中点位于髂骨中部、髋臼后上、髂耻联合及骶髂关节部位，其中最大应力产生在髋臼后上部。②主应力从从臼顶后上部位向骶髂关节传递，同时部分向耻骨上支传递。随着股骨后伸的加大，臼顶至髂结节区域的应力逐步加大。③髋臼区域的应力主要来源于体质量负荷产生的头臼作用力，肌肉收缩力的作用有限。结果提示，采用三维光弹法可直观全场反映髋臼区域应力分布特征，与既往有限元实验产生的结果基本相符。

Three-dimensional photoelastic analysis on the stress distribution of the pelvis under normal gait based on laser rapid prototyping technology

BACKGROUND:Finite element technology is a digital simulation of the real stress situation; however, photoelastic technology can truly display the overall stress distribution of the test model. OBJECTIVE:To make the pelvis photoelastic model by laser rapid prototyping technology, and then to investigate the stress distributions of the pelvis under normal gait loading conditions by three-dimensional photoelastic analysis and to compare the result with that gained by the finite element method. METHODS:The pelvic potoelastic model was made by laser rapid prototyping technology, including the fifth lumbar vertebrae and bilateral proximal femur. Mass loading was imposed on the femur. Four groups of muscles forces were imposed through steel wire fixed on iliac wing, anterior superior iliac spine, posterior superior iliac spine and inferior ramus of pubis. The femur was assumed to adduct for 15° and moved from flexed 22° to extend 12° during four gait phases. After stress froze, slices were cut along the arcuate line. Isochromatic lines and isoclinic lines were observed in the field of polarized light. RESULTS AND CONCLUSION:①Stress was concentrated on the center of ilium posterior superior roof of acetabulum, iliopubic eminence and cacroiliac joint, and the maximum stress was on the posterior superior roof of acetabulum. ② The main stress was transferred from posterior superior roof of acetabular to the cacroiliac joint and superior ramus of pubis partly. The area from roof to tubercle of the iliac crest loaded more stress with the femur extending. ③The stress on the acetabular area was mainly from the acetabular contact forces produced by mass loading, and the role of the muscle contraction force was limited. The three-dimensional photoelastic analysis could reflect distribution of stress on acetabulum. The result was in accordance with the data of finite element method.