髋臼发育不良者全髋置换中置入不同直径髋臼杯的力学分析

背景：成人髋臼发育不良髋臼小而浅，臼内有大量骨痂和瘢痕组织等都为人工髋关节置换臼杯安装带来极大困难。臼杯安装后局部的力学变化关系到置换后假体松动的发生及使用寿命。 目的：利用三维有限元力学分析方法，对髋关节发育不良患者采用不同直径臼杯置入，观察对髋臼假体-骨界面间应力分布情况的影响。 方法：选取髋关节发育不良患者的骨盆为试验对象，用螺旋 CT 做全长连续扫描，然后利用计算机仿真技术对 CT 图像进行三维重建，建立髋关节发育不良骨盆模型。在计算机环境中对重建模型进行不同直径臼杯置入的模拟手术，利用有限元分析软件对重建模型进行有限元网格化及力学分析。 结果与结论：对于髋臼发育不良的病例，选择小直径臼杯可应对髋臼浅平、骨床骨量不足的缺陷而达到较好的臼杯骨床包容，但臼杯直径小致接触面小使单位面积应力升高；另一方面，大直径臼杯置入扩大磨锉髋臼骨床可引起髋内壁破损突破，导致应力（包括压应力及剪切力）增大及集中。由此推断，髋臼发育不良全髋关节置换时应在保证骨床包容的前提下选择较大直径的臼杯，有利于应力的良好分布，但应尽量避免或减少扩大磨锉髋臼骨床所致髋臼内壁的穿破。

Mechanical analysis of total hip replacement with cup of different diameters in patients with developmental dysplasia of hip

BACKGROUND：The anatomical structure of acetabulum is different for the developmental dysplasia of the hip, which is smal and shal ow, with abundant cal us and scar tissue. It is difficult to determine the diameter of cup and instal ation of the cup during arthroplasty. Loosening and survival of postoperative prosthesis were influenced by local mechanical changes. OBJECTIVE：Using the three-dimensional finite element analysis, the stress distribution in acetabular cup-bone interface after implanting cups with different diameters was studied during total hip replacement in treating the dysplasia of hip. METHODS：Pelvis of developmental dysplasia of the hip patients was selected in this study. Acetabulum in the dysplasia was scanned by spiral CT. The computer simulation technology was applied to reconstruct the three-dimensional model of the pelvic for observing the dysplasia of hip from CT scan picture. Implanting cups with different diameters were simulated. Then the pelvis and acetabular cup model were meshed. The mechanics analysis tool was used to analyze three-dimensional model. RESULTS AND CONCLUSION：For the developmental dysplasia, we chose cup with smal diameter that could lead to better bone bed inclusion of cup during total hip replacement. Smal diameter cup induced a smal contact area and increased unit area stress. On the other hand, with implanting the larger cup and increasing degree of acetabular grinding, the acetabular wal bone breaks more obvious, so that the stress （compressive stress and shearing force） concentration at the top of the acetabulum and uneven stress in the rest were apparent increasingly. Thus, in clinical practice, under the premise of the bone bed inclusion, a large diameter cup is helpful to good distribution of stress during total hip replacement, but the perforation of acetabular wal induced by enlarged bone bed should be avoided or minimized.