PD Hinduja National Hospital & Medical Research Centre, Veer Savarkar Marg, Mahim, Mumbai, 400016, India.
Clin Orthop Relat Res. 2010 Nov;468(11):2904-13. doi: 10.1007/s11999-010-1409-2.
Low-cost indigenous megaprostheses used in the developing world are prone to mechanical failure but the frequency and causes are not well established.
QUESTIONS/PURPOSES: We retrospectively analyzed the causes of failure, particularly design, and suggest changes to reduce the breakage. We also report our experience with revision surgery.
We identified 28 breakages in 266 megaprosthetic knee arthroplasties performed between January 2000 and December 2006. Twenty-six breakages were revised to another prosthesis. The complications were studied and the function was evaluated. Prostheses were studied for failure by the computer-aided design program SolidWorks(®) and Hyperworks(®) for finite element analysis (FEA). Design improvements were performed based on these results.
In 21 cases, the failure occurred at the stem-collar junction, the point of maximum stress predicted by FEA. Stainless steel implants were prone to failure. There was one early and one late infection. Three patients died of metastatic disease. The most difficult surgical step involved the removal of the well-cemented broken stem from the intramedullary canal. Musculoskeletal Tumor Society scores varied from 27 to 29 after revision. FEA revealed stress could be reduced by filleting the stem-collar junction and by two-piece stems.
Revisions of broken total knee megaprostheses, though technically difficult, have allowed patients reasonable function. We recommend design analysis for custom prostheses to point to areas of weakness. Breakages can be reduced by using titanium stems and filleting the junction or by having two-piece inserted stems. Incorporating these changes has reduced the failures in our experience.
在发展中国家使用的低成本国产大型假体容易发生机械故障，但故障的频率和原因尚不清楚。
问题/目的：我们回顾性分析了故障的原因，特别是设计方面，并提出了一些改进建议，以减少断裂的发生。我们还报告了我们在翻修手术方面的经验。
我们在 2000 年 1 月至 2006 年 12 月期间共对 266 例大型人工膝关节假体进行了研究，其中 28 例出现了断裂。26 例进行了翻修。研究了并发症，并对功能进行了评估。通过计算机辅助设计程序 SolidWorks(®)和 Hyperworks(®)对假体进行了有限元分析(FEA)，以研究断裂原因。根据这些结果对设计进行了改进。
在 21 例病例中，断裂发生在柄颈交界处，这是 FEA 预测的最大应力点。不锈钢植入物更容易出现故障。有一例早期感染和一例晚期感染。有 3 例患者死于转移性疾病。最困难的手术步骤是从髓腔内取出已牢固固定的断裂柄。翻修后肌肉骨骼肿瘤学会评分从 27 到 29 不等。FEA 显示，通过对柄颈交界处进行圆角处理和采用分体式柄，可以降低应力。
尽管翻修大型全膝关节假体技术难度较大，但可以让患者获得合理的功能。我们建议对定制假体进行设计分析，以发现薄弱环节。通过使用钛制柄和对交界处进行圆角处理，或采用分体式插入柄，可以减少断裂的发生。在我们的经验中，采用这些改进措施已经减少了故障的发生。
