全髋关节置换术中的髋臼外展角和磨损的关系

目的研究人工全髋关节置换术中的髋臼外展角与磨损的关系,及其对人工全髋关节稳定性的影响。方法对30例32髋进行平均4.2年的随访。测量髋臼杯的外展角,并通过测量在随访期间股骨头中心相对于髋臼中心的矢量位移,来确定关节面磨损的大小和方向,并进行统计学分析。结果最近随访时,30例患者的32个髋关节假体均未发现临床松动和失败征象,假体柄轴线与股骨纵轴成角均在3°以内。聚乙烯平均线性磨损量为0.81mm,磨损速度为0.18mm/年,髋臼外展角平均54.5°。磨损方向平均为?6.93°,指向上方稍偏外侧。线性回归分析显示磨损方向与髋臼假体外展角度存在负相关关系。随着外展角度的增加,磨损方向由内上方转为外上方,外展角55°以上的假体磨损方向基本指向外上方。未发现线性磨损速度与外展角及磨损方向之间的相关关系。结论过大的外展角使股骨头中心向外上方迁移,可能会造成应力分布不均和假体磨损增加,因此临床上应该避免髋臼假体植入的外展角超过55°,以维持髋关节的活动度和稳定性。

The relationship of wearing with the abduction angle of the acetabulum in total hip arthroplasty

Objective A group of total hip arthroplasties were followed up radiologically to in ves-tigate the relationship of the cup ab duction angle with the extent of wearing and its direction and the effects of the cup abduction angle on the stability of hip joint.Methods A series of 32hip joints(30patients)were followed up routinely.The average f ollow-up period was 4.2years.The cu p abduction angle was measured,and the sagittal displacement of fem oral head to acetabulum was also exam ined to determine the direction and degree of linear polyethylene wear.The direction and magnitude of wear were decided by measuring femoral head penetration into the polyethylene liner.A new method of computer assisted two dimensional wear mea-surement was employed in this study.The results were statistically analyzed,with a P value less than 0.05indicating significant difference.Results There were no evidences of component loosening and clinical failure among the 32hips at a latest f ollow-up.The angle between the axis femoral component and femoral shaft in all of the patients was less than 3d egrees.The average amount of linear wear was 0.81mm,and the wear rate was 0.18mm per year.The average cup abduction angle was 54.5degrees,the wear direction was?6.93degrees superior-laterally.Wear d irection had a negative correlation with cup abduction angle by linear re-gression analysis;it meaned that th e direction of wear turning from superior-medial to superior-lateral gradually along with the increasing of cup abduction angle.In the cup abduction angle of more than 55degrees,the wear direction mostly orientated superior-laterally.However,no correlation of linear wear amount with wear di rec-tion or cup abduction angle was found in linear regression analysis.Conclusion Wear direction and cup abduction angle is negatively corre lated.The wear direction points mostly superior-laterally with cup abd uction angle over 55degrees,which could re sult in uneven stress distribution a nd greater stress concentration sup e-rior-laterally,consequently increase of wear;meanwhile,if the cup is too vertical,the risk of impingemen t and dislocation increases.The study shows that acetabular components with cup abduction angle over 55de-grees should be avoided in order to ma intain hip stability and desirable r ange of motion.