Chevalier Yan, Santos Inês, Müller Peter E, Pietschmann Matthias F
Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistrasse 15, D-81377 Munich, Germany.
Department of Orthopedic Surgery, Physical Medicine and Rehabilitation, University Hospital of Munich (LMU), Campus Grosshadern, Marchioninistrasse 15, D-81377 Munich, Germany.
J Biomech. 2016 Jun 14;49(9):1724-1733. doi: 10.1016/j.jbiomech.2016.04.003. Epub 2016 Apr 8.
Glenoid loosening is still a main complication for shoulder arthroplasty. We hypothesize that cement and bone stresses potentially leading to fixation failure are related not only to glenohumeral conformity, fixation design or eccentric loading, but also to bone volume fraction, cortical thickness and degree of anisotropy in the glenoid. In this study, periprosthetic bone and cement stresses were computed with micro finite element models of the replaced glenoid depicting realistic bone microstructure. These models were used to quantify potential effects of bone microstructural parameters under loading conditions simulating different levels of glenohumeral conformity and eccentric loading simulating glenohumeral instability. Results show that peak cement stresses were achieved near the cement-bone interface in all loading schemes. Higher stresses within trabecular bone tissue and cement mantle were obtained within specimens of lower bone volume fraction and in regions of low anisotropy, increasing with decreasing glenohumeral conformity and reaching their maxima below the keeled design when the load is shifted superiorly. Our analyses confirm the combined influences of eccentric load shifts with reduced bone volume fraction and anisotropy on increasing periprosthetic stresses. They finally suggest that improving fixation of glenoid replacements must reduce internal cement and bone tissue stresses, in particular in glenoids of low bone density and heterogeneity.
盂肱关节松动仍然是肩关节置换术的主要并发症。我们推测，可能导致固定失败的骨水泥和骨应力不仅与盂肱关节匹配度、固定设计或偏心负荷有关，还与盂肱关节的骨体积分数、皮质厚度和各向异性程度有关。在本研究中，利用描绘真实骨微结构的置换盂肱关节微有限元模型计算假体周围的骨和骨水泥应力。这些模型用于量化在模拟不同水平盂肱关节匹配度的负荷条件下以及模拟盂肱关节不稳的偏心负荷条件下骨微结构参数的潜在影响。结果表明，在所有负荷方案中，骨水泥-骨界面附近的骨水泥应力峰值均出现。在骨体积分数较低的标本以及各向异性较低的区域，小梁骨组织和骨水泥壳内的应力较高，随着盂肱关节匹配度的降低而增加，当负荷向上移位时，在龙骨设计下方达到最大值。我们的分析证实了偏心负荷移位与骨体积分数和各向异性降低对假体周围应力增加的综合影响。最终表明，改善盂肱关节置换的固定必须降低骨水泥和骨组织内部应力，尤其是在骨密度低和异质性高的盂肱关节中。
