Department of Orthopaedics, University Medicine Rostock, Doberaner Straße 142, D-18057 Rostock, Germany.
Clin Biomech (Bristol). 2020 Dec;80:105202. doi: 10.1016/j.clinbiomech.2020.105202. Epub 2020 Oct 23.
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.
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.
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).
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.
无水泥模块化末端假体采用锥形带槽干骺端，可覆盖髋关节重建术中广泛的股骨缺损谱。然而，对于这些髋关节假体，关于最小骨干锚固距离的建议差异很大。本实验研究调查了锥形带槽翻修干骺端假体在不同类型股骨骨缺损情况下的初始稳定性。
使用 6 个新鲜冷冻的人股骨，在循环加载条件下检查双模块翻修干骺端假体在植入物-骨界面内的相对运动。使用线性变量差动变压器（LVDT）捕获植入物下沉以及骨-植入物界面的微动，用于完整股骨和三种不同的缺陷（从 Paprosky II 型到 IIIB 型）。
与完整股骨相比，施加 Paprosky IIIB 型缺陷（3cm 完整骨干）显著增加了平均干骺端下沉（每 500 次加载循环增加 13-389μm；P=0.116），但界面微动向量总和保持不变（50μm 对 53μm）。在 Paprosky IIIB 型缺陷中，由于旋转（水平面）引起的下沉分量明显高于完整股骨和 Paprosky II 型缺陷（P≤0.041）。
在最佳的骨质量和理想的股骨准备条件下，3cm 的锥形固定足以满足体外骨长入的设定标准。应建议使用 7cm 的锥形固定以限制旋转下沉，尤其是在骨干骨质量受损或预期部分负重困难的情况下。
