Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.
Faculty of Medicine and Health Technology, Tampere University, Tampere; Coxa Hospital for Joint Replacement, Tampere, Finland.
Acta Orthop. 2024 Oct 11;95:586-591. doi: 10.2340/17453674.2024.41946.
In contemporary total hip replacement (THR), dislocation is one of the most common complications. At our institution, the cause of an increase in the dislocation rate was recently reported to be reduced head coverage of a newly introduced neutral liner. We therefore aimed to ascertain whether differences exist in articulating head coverage between the various neutral liners used in contemporary THR. A secondary aim was to utilize coverage measurements to develop a new liner coverage classification.
The articulating head coverage of 25 modular neutral polyethylene liners used in 6 uncemented cup designs from 4 major manufacturers was evaluated. The measurements were performed in a metrology laboratory and a mathematical model was developed to calculate coverage of the articulating surfaces. Further, 1 "elevated rim" liner and 1 "face changing liner" were included to develop a new liner coverage classification.
The articulating head coverage among the studied liners ranged from 167.7° to 194.8°, corresponding to a variation of 27.1°. The variations with different cup and head sizes within each design were smaller (from 1.0° to 5.6°) than those between different designs. Each of the liner designs offered distinct coverage, even though they were all classified as neutral. Based on measurements, a set of descriptive parameters to discriminate different liners in terms of coverage was created.
We showed that all neutral liners are not equal - instead, they clearly varied in terms of their actual coverage design. We suggest our set of descriptive parameters called "hemispheric coverage index values" be used in discriminating the differences in liner coverage.
在当代全髋关节置换术（THR）中，脱位是最常见的并发症之一。最近，我们机构报告称，一种新的中性衬垫的头覆盖面积减少是导致脱位率增加的原因。因此，我们旨在确定在当代 THR 中使用的各种中性衬垫之间是否存在关节头覆盖的差异。次要目标是利用覆盖测量值开发新的衬垫覆盖分类。
评估了来自 4 家主要制造商的 6 种非骨水泥杯设计的 25 个模块化中性聚乙烯衬垫的关节头覆盖情况。测量是在计量实验室进行的，并开发了一个数学模型来计算关节表面的覆盖范围。此外，还包括 1 个“高边衬垫”和 1 个“表面变化衬垫”，以开发新的衬垫覆盖分类。
研究中的衬垫的关节头覆盖范围从 167.7°到 194.8°，变化范围为 27.1°。在每个设计中，不同杯和头尺寸之间的变化（从 1.0°到 5.6°）比不同设计之间的变化小。尽管所有设计都被归类为中性，但它们的覆盖范围明显不同。基于测量结果，创建了一组描述性参数，用于根据覆盖范围区分不同的衬垫。
我们表明，并非所有的中性衬垫都是平等的，它们在实际覆盖设计方面存在明显差异。我们建议使用我们的一组描述性参数，称为“半球覆盖指数值”，用于区分衬垫覆盖的差异。
