Background

Cementless modular endoprostheses with tapered fluted stems cover a wide spectrum of femoral defects in reconstructive surgery of the hip. Nevertheless, for these hip stems the recommendations concerning the minimum diaphyseal anchorage distance differ widely. The present experimental study investigated the primary stability of a conical fluted revision stem depending on different types of femoral bone defects.

Methods

Using six fresh frozen human femora, the relative movement of a bi-modular revision stem within the implant-bone interface was examined under cyclic loading conditions. Implant subsidence as well as micromotions at the bone-implant interface were captured with linear variable differential transformers for the intact femora and three different defects ranging from Paprosky type II to type IIIB.

Findings

Compared to the intact femur, the infliction of a Paprosky type IIIB defect (3 cm of intact diaphysis) notably increased mean stem subsidence (13–389 μm per 500 load cycles; P = 0.116) but the mean interface micromotion vector sum remained unchanged (50 μm vs. 53 μm). In Paprosky IIIB defects the subsidence component resulting from rotation (horizontal plane) was significantly higher than with the intact femur and a Paprosky II defect (P ≤ 0.041).

Interpretation

With optimal bone quality and ideal femur preparation a 3 cm conical fixation was sufficient to meet the set criteria of bony ingrowth in vitro. A conical fixation of 7 cm should be recommended to limit rotational subsidence, especially in case of impaired diaphyseal bone quality or expected difficulties with partial weight-bearing.

中文翻译：

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取决于股骨缺损大小的非骨水泥状圆锥形凹槽茎的微动和下沉–人类尸体研究

背景

带有锥形槽状茎的非骨水泥模块化假体在髋关节的重建手术中覆盖了广泛的股骨缺损。但是，对于这些髋关节，有关最小骨干锚固距离的建议差异很大。目前的实验研究根据不同类型的股骨缺损研究了圆锥形凹槽翻修柄的主要稳定性。

方法

使用六个新鲜的冷冻人股骨，在循环载荷条件下检查了双模块翻新柄在植入物-骨界面内的相对运动。植入物的沉陷以及在骨-植入物界面处的微动都用线性可变差动变压器记录了完整的股骨和从Paprosky II型到IIIB型的三种不同的缺陷。

发现

与完整股骨相比，Paprosky IIIB型缺损（3根完整的干physi端）受累显着增加了平均茎沉陷（每500个负荷循环13-389μm；P  = 0.116），但平均界面微运动矢量和保持不变（ 50μm和53μm）。在Paprosky IIIB缺陷从旋转（水平面）所产生的沉降成分比与完整的股骨和一个Paprosky II缺陷（显著更高P  ≤0.041）。

解释

具有最佳的骨质量和理想的股骨准备，3 cm的圆锥形固定足以满足体外骨向内生长的既定标准。建议使用7 cm的锥形固定装置以限制旋转下陷，尤其是在干端骨质量受损或预期部分负重困难的情况下。