INTRODUCTION The Robert Mathys (RM) monoblock uncemented cup is a design less commonly used in primary total hip replacement. It's purported advantages over modular cemented cups are: (1) its modulus of elasticity approximating bone, thus mimicking load transmission and the biomechanical behaviour of the cup to better match stresses on the acetabulum, leading to bone-preservation; and (2) as a 1-piece cup there is absence of a mobile interface between a liner and shell, preventing backside wear. Since its inception in 1983 there have been 3 major design changes: the RM Classic, the RM Pressfit, and the RM Vitamys with the most modern polyethylene (vitamin E). METHODS In a retrospective cohort study of the New Zealand Joint Registry, all designs of RM acetabular cup were reviewed. Data were included from1998 to 2018. All-cause revision rates, reasons for revision and the Oxford Hip Score (OHS) were assessed. RESULTS In total 13,272 acetabular cups were included. The all-cause revision rates did not differ between the designs. Revision rates for aseptic loosening in the RM Vitamys were lower, but the follow-up was shorter and more larger heads were used. There was no difference in the OHS. CONCLUSION All implant designs were safe. The use of larger heads led to a decrease in revisions due to dislocation. It has to be waited out whether the RM Vitamys performs superior in the long-term due to the highly cross-linked polyethylene.

中文翻译：

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Mathys RM 整体杯 45 年的演变：范式转变是否值得？

简介 Robert Mathys (RM) 一体式非骨水泥臼杯是一种不太常用于初级全髋关节置换术的设计。据称，与模块化骨水泥臼杯相比，它的优势在于：(1) 其弹性模量接近骨骼，从而模拟载荷传递和臼杯的生物力学行为，以更好地匹配髋臼上的应力，从而保护骨骼；(2) 作为一件式杯子，衬里和外壳之间没有移动界面，防止背面磨损。自 1983 年问世以来，已经进行了 3 次重大设计更改：RM Classic、RM Pressfit 和采用最现代聚乙烯（维生素 E）的 RM Vitamys。方法 在新西兰联合登记处的一项回顾性队列研究中，对 RM 髋臼的所有设计进行了审查。数据包括 1998 年至 2018 年。全因修正率，对翻修的原因和牛津髋关节评分 (OHS) 进行了评估。结果 总共包括 13,272 个髋臼杯。全因修正率在设计之间没有差异。RM Vitamys 中无菌松动的修正率较低，但随访时间较短且使用了更大的头部。OHS 没有差异。结论 所有种植体设计都是安全的。使用较大的头部导致因错位而导致的修正减少。由于高度交联的聚乙烯，RM Vitamys 是否在长期内表现出色还需等待。但是后续时间更短，使用了更大的头。OHS 没有差异。结论 所有种植体设计都是安全的。使用较大的头部导致因错位而导致的修正减少。由于高度交联的聚乙烯，RM Vitamys 是否在长期内表现出色还需等待。但是后续时间更短，使用了更大的头。OHS 没有差异。结论 所有种植体设计都是安全的。使用较大的头部导致因错位而导致的修正减少。由于高度交联的聚乙烯，RM Vitamys 是否在长期内表现出色还需等待。