Introduction:

The majority of acetabular revisions can be performed with an uncemented, porous acetabular component with or without bone grafting. These are contained acetabular defects, with an intact acetabular rim (Paprosky type I and II). As defects of the medial wall of the acetabulum are a challenge situation revision surgery, we performed this biomechanical study on a pig pelvis model with contained acetabular defects to determine the size of medial wall defect at which the acetabular cup will have sufficient primary stability.

Materials and methods:

In 24 pig pelvis models, different diameter of medial wall defects were created, followed by acetabular component placement. The acetabulum externally loaded, and the force at a level in which the acetabular component remains stable for each diameter of defect, or at which point the acetabular cup moves into the pelvis for >2 mm.

Results:

In the models with acetabular medial wall defects of 10 and 20 mm, 2 mm acetabular displacement occurred under a force between 1000 and 1500 N. In those with a medial wall defect of 25 mm, the force that caused acetabular instability was between 700 and 1000 N. In the models with 30 mm of medial wall defect all acetabular components were unstable under a force of 700 N.

Conclusions:

According to our results, acetabular component should be stable if the defect of the medial wall of the acetabulum is less than 68% of the diameter of the acetabular component or if the uncovered surface area of the acetabular component is not greater than 27%, and the force <700 N. For a load of 1000 N, the medial wall defect should not exceed 45% of acetabular component diameter or 18% of uncovered acetabular component surface.

中文翻译：

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多孔杯翻修髋关节置换术中安全髋臼内侧壁缺损尺寸的测量

介绍：

大多数髋臼翻修可以使用非骨水泥的多孔髋臼部件进行，无论是否进行骨移植。这些包含髋臼缺陷，具有完整的髋臼边缘（Paprosky I 型和 II 型）。由于髋臼内壁缺损是一项具有挑战性的修复手术，我们对包含髋臼缺损的猪骨盆模型进行了这项生物力学研究，以确定髋臼杯具有足够初级稳定性的内壁缺损的大小。

材料和方法：

在 24 个猪骨盆模型中，创建了不同直径的内侧壁缺损，然后放置髋臼假体。髋臼外部负载，以及在髋臼组件对于每个缺损直径保持稳定的水平上的力，或在该点髋臼杯移入骨盆> 2 mm。

结果：

在髋臼内壁缺损为 10 和 20 mm 的模型中，在 1000 到 1500 N 的力下会发生 2 mm 的髋臼位移。在内壁缺损 25 mm 的模型中，导致髋臼不稳定的力在 700 到 1000 N 之间N. 在具有 30 mm 内侧壁缺损的模型中，所有髋臼组件在 700 N 的力下都不稳定。

结论：

根据我们的研究结果，如果髋臼内壁的缺损小于髋臼假体直径的 68%，或者如果髋臼假体的裸露表面积不大于 27%，则髋臼假体应该是稳定的，并且力 <700 N。对于 1000 N 的负载，内壁缺损不应超过髋臼组件直径的 45% 或未覆盖髋臼组件表面的 18%。