Dickinson A S, Taylor A C, Jeffers J R T, Browne M
Bioengineering Science Research Group, University of Southampton, Southampton, UK.
Proc Inst Mech Eng H. 2010;224(7):841-51. doi: 10.1243/09544119JEIM680.
Hip resurfacing is a popular treatment for osteoarthritis in young, active patients. Previous studies have shown that occasional failures--femoral neck fracture and implant loosening, possibly associated with bone adaptation--are affected by prosthesis sizing and positioning, in addition to patient and surgical factors. With the aim of improving tolerance to surgical variation, finite element modelling was used to indicate the effects of prosthesis metaphyseal stem design on bone remodelling and femoral neck fracture, with a range of implant orientations. The analysis suggested that the intact femoral neck strength in trauma could be maintained across a wider range of varus-valgus orientations for short-stemmed and stemless prostheses. Furthermore, the extent of periprosthetic bone remodelling was lower for the short-stemmed implant, with slightly reduced stress shielding and considerably reduced densification around the stem, potentially preventing further progressive proximal stress shielding. The study suggests that a short-stemmed resurfacing head offers improved tolerance to misalignment and remodelling stimulus over traditional designs. While femoral neck fracture and implant loosening are multifactorial, biomechanical factors are of clear importance to the clinical outcome, so this may reduce the risk for patients at the edge of the indications for hip resurfacing, or shorten the surgical learning curve.
髋关节表面置换术是治疗年轻、活跃患者骨关节炎的一种常用方法。以往的研究表明，偶尔出现的失败情况——股骨颈骨折和植入物松动，可能与骨适应性有关——除了患者和手术因素外，还受到假体尺寸和位置的影响。为了提高对手术变异的耐受性，采用有限元建模来研究假体干骺端柄设计对骨重塑和股骨颈骨折的影响，考虑了一系列植入物方向。分析表明，对于短柄和无柄假体，在更广泛的内翻-外翻方向范围内，创伤时完整的股骨颈强度能够得以维持。此外，短柄植入物周围假体周围骨重塑的程度较低，应力遮挡略有减少，柄周围的致密化程度显著降低，这可能会防止进一步的近端应力遮挡进展。该研究表明，与传统设计相比，短柄表面置换头对排列不齐和重塑刺激具有更好的耐受性。虽然股骨颈骨折和植入物松动是多因素导致的，但生物力学因素对临床结果显然很重要，因此这可能会降低处于髋关节表面置换术适应症边缘的患者的风险，或者缩短手术学习曲线。
