发育性髋脱位股骨头表面应力变化的实验研究

目的 通过动物模型,探讨发育性髋脱位股骨头表面应力的变化及对前倾角改变的影响.方法 7只西藏小型猪,通过手术制作出左髋关节髋脱位模型,右侧作为对照组,术后即刻、术后1个月、3个月不同时间分别行骨盆X线检查,测量双侧sharp角及臼头指数,比较术后不同时间各项指标的差异.另分别于术后当天、术后1个月、3个月将实验动物行骨盆及下肢CT检查,收集数据,制作髋脱位三维有限元模型,分析实验侧股骨头表面与对照侧应力分布的变化特点.结果 术后当天实验侧较对照侧sharp角差异无统计学意义,术后1个月、3个月实验侧较对照侧sharp角增大,差异无统计学意义,术后当天、术后1个月、3个月实验侧头臼指数较对照侧减小,差异有统计学意义;同侧对比显示随着脱位时间的延长,实验侧sharp角逐渐增大,差异无统计学意义,头臼指数随着脱位时间的延长逐渐减小,差异有统计学意义.有限元股骨头表面应力分析结果提示:术后当天、术后1个月、3个月实验侧与对照侧股骨头内侧相同检测位点应力分布值比较,实验侧检测位点应力分布值增加,差异有统计学意义(P＜0.05);随着脱位时间的延长,实验侧殷骨头内侧相同观察点应力值不断加大,相同位点应力分布值比较差异有统计学意义(P＜0.05).结论 前倾角加大及股骨头及髋臼的变形是一个渐变的过程,或与股骨头表面应力分布改变有较大关系.提示在临床工作中早期发现早期手术、以及手术中纠正前倾角显得十分重要.

Stress changes of femoral head in developmental dislocation of the hip

Objective To explore the changes of surface stress and angle of inclination of femoral head in developmental dislocation of the hip.Methods Left hip dislocation model was established surgically in 7 Tibetan pigs while right sides served as control group.Pelvic radiological examination was performed.And bilateral values of Sharp angle and acetabular head index were measured at different timepoints of postoperative immediately,postoperative Month 1 and Month 3 respectively.Computed tomography examinations of pelvis and lower extremities were performed.Then,a three-dimensional finite element model was established for analyzing the characteristics of stress distribution of femoral head and control side.Results Postoperative immediately,Sharp angle showed no significant difference between experimental and control sides.At postoperative Month 1 &3,Sharp angle increased at experimental side versus control side and the difference was insignificant.At postoperative immediately,Month 1 and Month 3,head acetabular index at experimental side decreased versus control side and the difference was significant;ipsilateral comparison showed that,with elapsing time of dislocation,Sharp angle increased at experimental side and the difference was insignificant;acetabular head index decreased with elapsing time of dislocation,the difference was significant.Finite element analysis of surface stress of femoral head:stress distribution of the same site was compared with that of control side femoral head at Month 1 and 3.Stress distribution significantly increased at experimental side and the difference was statistically significant (P＜0.05);With elapsing time,stress value of medial femoral head at experimental side and lateral stress of femoral head increased and stress distribution of the same site was statistically significant (P＜0.05).Conclusions Increase of anterior tilt angle and deformation of femoral head and acetabulum occur gradually and it is correlated with surface stress distribution of femoral head.Thus early detection,timely operation and correcting anterior tilt angle are essential.