Poggie Robert A, Turgeon Thomas R, Coutts Richard D
Zimmer Trabecular Metal Technology, 48 Horsehill Road, Cedar Knolls, NJ 07927, USA.
J Bone Joint Surg Am. 2007 Feb;89(2):367-75. doi: 10.2106/JBJS.F.00148.
Alternative bearings have been explored in an attempt to improve the longevity of total hip prostheses. A Food and Drug Administration (FDA)-approved clinical study of a nonmodular acetabular component consisting of a porous metal shell, compression-molded polyethylene, and a ceramic liner inlay was discontinued following reports of early failures.
Between October 1999 and January 2003, 429 patients were enrolled in a prospective study to evaluate a cementless ceramic-on-ceramic total hip arthroplasty design (Hedrocel ceramic bearing cup; Implex, Allendale, New Jersey). Two hundred and eighty-two patients (315 hips) were treated with the experimental acetabular implant and 147 patients (157 hips) were treated with an acetabular implant that consisted of the same porous shell but an allpolyethylene liner. Clinical data including a Harris hip score and responses to the Short Form-12 (SF-12) health survey were collected preoperatively and at twelve and twenty-four months postoperatively. Serial radiographs were made preoperatively; at six weeks, three months, six months, and twelve months postoperatively; and annually thereafter. Retrieval analysis was performed on all failed explanted components. Failure was defined as fracture or displacement of the ceramic liner out of the acetabular component. In addition, biomechanical testing was performed on unimplanted acetabular components and mechanically altered cups in an effort to recreate the mechanisms of failure. Finite element analysis was used to estimate stress and strain within the ceramic liner under extreme physiologic loading conditions.
The ceramic liner failed in fourteen of the 315 experimental acetabular components; all of the failures were at the ceramic-polyethylene interface. Patients with a body weight of >91 kg had a 4.76 times greater odds of the ceramic liner failing than those who weighed < or =91 kg. Retrieval analysis demonstrated stripe and rim wear with evidence of adhesive wear, indicating a potentially high-friction interaction at the articulation. Finite element analysis demonstrated that the forces on the ceramic liner in cups subjected to extreme loading conditions were insufficient to cause fracture. Biomechanical testing was unable to reproduce an initial ceramic liner displacement in vitro; however, when the ceramic liner was forcibly displaced prior to biomechanical testing, complete displacement and eventual fracture of the ceramic liner resulted.
We hypothesized that the combination of a high patient body weight, an extensive range of motion, and subluxation of the femoral head led to high friction at the articulation between the femoral head and the rim of the liner, which initiated displacement of the ceramic liner. Subsequent normal gait led to further displacement of the liner in all of the fourteen failed components and eventually to ceramic fracture in twelve of the fourteen components.
人们一直在探索采用替代轴承，以期提高全髋关节假体的使用寿命。一项由美国食品药品监督管理局（FDA）批准的关于一种非模块化髋臼组件的临床研究被中止，该组件由多孔金属外壳、模压聚乙烯和陶瓷内衬嵌体组成，原因是有早期失败的报告。
在1999年10月至2003年1月期间，429例患者被纳入一项前瞻性研究，以评估一种非骨水泥型陶瓷对陶瓷全髋关节置换设计（Hedrocel陶瓷轴承杯；Implex，新泽西州阿伦代尔）。282例患者（315髋）接受了实验性髋臼植入物治疗，147例患者（157髋）接受了由相同多孔外壳但全聚乙烯内衬组成的髋臼植入物治疗。收集了术前以及术后12个月和24个月的临床数据，包括Harris髋关节评分和对简短健康调查问卷（SF - 12）的回答。术前、术后6周、3个月、6个月和12个月以及此后每年都进行了系列X线片检查。对所有取出的失败组件进行了翻修分析。失败定义为陶瓷内衬从髋臼组件中骨折或移位。此外，对未植入的髋臼组件和机械改变的髋臼杯进行了生物力学测试，以重现失败机制。采用有限元分析来估计在极端生理负荷条件下陶瓷内衬内的应力和应变。
在315个实验性髋臼组件中，有14个陶瓷内衬出现失败；所有失败均发生在陶瓷 - 聚乙烯界面。体重>91 kg的患者陶瓷内衬失败的几率是体重≤91 kg患者的4.76倍。翻修分析显示有条状和边缘磨损以及粘着磨损的迹象，表明关节处存在潜在的高摩擦相互作用。有限元分析表明，在承受极端负荷条件的髋臼杯中，作用于陶瓷内衬的力不足以导致骨折。生物力学测试无法在体外重现陶瓷内衬的初始移位；然而，当在生物力学测试前强行移位陶瓷内衬时，会导致陶瓷内衬完全移位并最终骨折。
我们推测，患者体重过高、活动范围过大以及股骨头半脱位的共同作用导致股骨头与内衬边缘之间的关节处产生高摩擦，从而引发陶瓷内衬的移位。随后的正常步态导致了所有14个失败组件中内衬的进一步移位，并最终导致其中12个组件的陶瓷骨折。
