髋臼假体放置角度对髋臼周围应力分布的影响

Influence from acetabular component orientation on stress distributions of periacetabulum

目的研究全髋关节置换（totalhiparthroplasty，THA）髋臼侧重建中不同髋臼假体安放角度对髋臼周围内外应力分布的影响，探索提高THA术后髋臼假体稳定性的方法。方法基于材料属性的非均匀赋值模型和由不同髋臼假体前倾角（15°，20°，25°）与外展角（40°，45°，50°）的9种组合方式构建包括正常髋模型在内的10种有限元模型，并以正常步行模式单支撑相中的髋关节最大接触力为载荷条件进行求解。以正常髋模型分析结果为对照，按照从定性到定量原则对比分析各模型的内外应力。结果当髋臼假体的放置角度与正常髋臼的解剖角度（前倾19°、外展46°）最接近时，髋臼周围的应力遮挡现象最明显。此外，当髋臼假体的外展角放置于45°，前倾角在15°～25°变化不会对模型整体应力分布造成较大的影响；而且在15°前倾角条件下，模型不仅在应力分布方面具有良好稳定性，同时在皮质骨和松质骨上应力遮挡现象相比于处于正常髋臼解剖角度时明显改善。结论对于髋臼的正常解剖形态未发生明显改变且需要接受THA手术的患者，应把髋臼假体放置在正常外展角45°，而前倾角应小于正常解剖前倾角5°左右并居于15°～20°之间。

Objective To study the influence from different placement angles of acetabular component on inner and outer stress distributions of periacetabulum in acetabular reconstruction of total hip arthroplasty （ THA）, so as to explore proper orientation for improving stability of acetabular component after THA. Methods Based on mod- el with inhomogeneous material property assignment, nine THA models with acetabular component at different anteversion angles（ 15°, 20°, 2.5°） and abduction angles（40°, 45°, 50°） as well as one normal hip model were constructed. The maximal hip contact force in phase of single leg stance during normal gait cycle was chosen as the loading condition. In addition, according to the qualitative and quantitative principle, inner and outer stress distributions on 9 THA models were analyzed and compared with the normal hip model as control. Results When abduction angle of acetabular component was the nearest to anatomic angle （19° anteversion, 46° abduction） of acetabulum, the phenomenon of stress shielding on periacetabulum was the most obvious. When abduction an- gle of acetabular component was placed at 45° and anteversion angle changed from 15° to 25°, no significant in- fluence was exerted on the whole stress distributions of THA models. Meanwhile, when anteversion angle of ace- tabular component was 15°, the THA model had good stability in stress distributions, and the phenomenon of stress shielding on cortical and cancellous bone was obviously improved. Conclusions For patients who have normal anatomic acetabulum and need to be treated with THA, the abduction angle of acetabular component should be placed at 45°, as that of normal acetabulum; the anteversion angle should be 5° smaller than that of normal acetabulum and between 15° and 20°.