Nadzadi Mark E, Pedersen Douglas R, Callaghan John J, Brown Thomas D
Department of Orthopaedic Surgery, Orthopaedic Biomechanics Laboratory, University of Iowa, 2181 Westlawn Building, Iowa City, IA 52242, USA.
Clin Biomech (Bristol). 2002 Jan;17(1):32-40. doi: 10.1016/s0268-0033(01)00096-1.
Examine the role of surgical orientation of the acetabular cup on posterior dislocation propensity for small-head-size total hip arthroplasty.
A finite element model of a widely used total hip arthroplasty system was examined for peak resisting moment and range-of-motion prior to impingement, as well as prior to onset of posterior dislocation. Acetabular component surgical orientation was varied.
Dislocation is a leading cause of total hip replacement failure, with an incidence between 2% and 11%. Clinical registries imply acetabular component orientation to be a leading predictor of dislocation. The finite element method permits this complex kinetic behavior to be addressed systematically.
Twenty-five combinations of cup abduction (five angles) and anteversion (five angles) were studied, with the resultant resisting moment about the cup center being tracked in each case. Key events were benchmarked, and a novel dislocation resistance index was developed for multi-factor comparison.
Increasing tilt and/or anteversion resulted in a monotonically increasing range-of-motion prior to impingement, as well as increased peak resisting moment. Range of motion was more sensitive to tilt, while peak resisting moment was more sensitive to anteversion. Peak resisting moment for 22-mm head size was nearly 25% less than that for a 26-mm head.
Increased cup tilt and anteversion discourage posterior dislocations of small-head-size components.
Pre-existing soft tissue compromise and untoward patient motions/postures are largely beyond surgeon control. However, other factors being equal, especially for small-head-size components, many posterior dislocations that would otherwise occur might be prevented by suitable tilt and anteversion of the acetabular component.
研究髋臼杯的手术定位对小头尺寸全髋关节置换术后脱位倾向的作用。
对一种广泛使用的全髋关节置换系统的有限元模型进行研究，以检查撞击前以及后脱位开始前的最大抵抗力矩和活动范围。髋臼组件的手术定位有所不同。
脱位是全髋关节置换失败的主要原因，发生率在2%至11%之间。临床登记表明髋臼组件的定位是脱位的主要预测因素。有限元方法允许系统地处理这种复杂的动力学行为。
研究了髋臼杯外展（五个角度）和前倾角（五个角度）的25种组合，每种情况下均跟踪髋臼杯中心的合成抵抗力矩。对关键事件进行了基准测试，并开发了一种新的抗脱位指数用于多因素比较。
增加倾斜度和/或前倾角会导致撞击前的活动范围单调增加，同时最大抵抗力矩也会增加。活动范围对倾斜度更敏感，而最大抵抗力矩对前倾角更敏感。22毫米股骨头尺寸的最大抵抗力矩比26毫米股骨头尺寸的小近25%。
增加髋臼杯的倾斜度和前倾角可减少小头尺寸组件的后脱位。
先前存在的软组织损伤以及患者不良的运动/姿势在很大程度上超出了外科医生的控制范围。然而，在其他因素相同的情况下，尤其是对于小头尺寸的组件，如果髋臼组件的倾斜度和前倾角合适，许多原本会发生的后脱位可能会被避免。
