Background

Trial fitting of the acetabular component in uncemented total hip replacement is traditionally done by trial cups. Since trial cups do not resemble the real press-fit obtained by the definitive cup, a dynamic trial inserter, called the X-pander ®, was developed to mimic the real amount of press-fit. However, the concern is raised of losing the initial press-fit by using the X-pander® due to pre-expansion of the acetabulum. The purpose of this study was to assess if there is a difference in primary stability between both methods.

Methods

A biomechanical randomized study was performed with bovine calf acetabula, with randomization between either using the X-pander® or the traditional trial cups to assess primary stability. The primary outcome was the force needed to achieve lever out of the implanted cup (Anexys, Mathys or Trident, Stryker), measured in Newton meter (Nm) with a biomechanical testing set up.

Findings

In total, 54 cups (19 Anexys, 35 Trident) were inserted and tested after randomized trial fitting. Overall mean lever out was 45.1 Nm (SD 14.6) for the X-pander® group and 45.0 Nm (SD 14.5) for the trial cups group. After adjustment for potential confounders (cup size and type) mixed model analysis did not reveal a significant difference in lever out force between both testing devices (mean 1.0 Nm, 95%CI (−5.9; 8.0), p = .77).

Interpration

Initial press-fit of the implanted cup is not lost by pre-expansion as done with dynamic trial fitting with the X-pander®.

中文翻译：

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通过扩大的试验杯进行动态试验装配不会损害髋臼主成分的稳定性。

背景

传统上通过试验杯完成髋臼组件在非骨水泥全髋关节置换术中的试戴。由于试验杯与最终杯所获得的实际压配合并不相似，因此开发了一种动态试验插入器，称为X-pander®，以模拟实际的压配合量。然而，由于髋臼的预膨胀，人们担心使用X-pander®失去初始压配合。这项研究的目的是评估两种方法之间的主要稳定性是否存在差异。

方法

使用牛小腿髋臼进行了生物力学随机研究，并在使用X-pander®或传统的试验杯之间进行随机评估，以评估主要稳定性。主要结果是达到杠杆所需的力，该杠杆是通过生物力学测试在牛顿米（Nm）中测量的，以将杠杆移出植入杯（Anexys，Mathys或Trident，Stryker）。

发现

在随机试验后，总共插入54杯（19头Anexys，35头三叉戟）并进行测试。X-pander®组的整体平均杠杆输出为45.1 Nm（SD 14.6），试验杯组的整体平均杠杆输出为45.0 Nm（SD 14.5）。在对潜在的混杂因素（杯的大小和类型）进行调整后，混合模型分析未显示两个测试装置之间的杠杆力有显着差异（平均值为1.0 Nm，95％CI（-5.9； 8.0），p  = 0.77）。

插补

预膨胀不会像X-pander®的动态试验装配那样通过预膨胀而失去最初的压入配合。