Zhang Qing-Hang, Cossey Andrew, Tong Jie
Mechanical Behaviour of Materials Laboratory, School of Engineering, University of Portsmouth, Anglesea Road, Portsmouth PO1 3DJ, UK.
Mechanical Behaviour of Materials Laboratory, School of Engineering, University of Portsmouth, Anglesea Road, Portsmouth PO1 3DJ, UK ; Spires Portsmouth Hospital, Bartons Road, Havant PO9 5NP, UK.
Med Eng Phys. 2016 Dec;38(12):1481-1488. doi: 10.1016/j.medengphy.2016.09.018. Epub 2016 Oct 10.
Periprosthetic bone strain distributions in some of the typical cases of total knee replacement (TKR) were studied with regard to the selection of material, design and the alignments of tibial components to examine which conditions are more forgiving than the others to stress shielding post a TKR. Four tibial components with two implant designs (cruciate sacrificing and cruciate retaining) and material properties (metal-backed (MB) and all-polyethylene (AP)) were considered in a specimen-specific finite element tibia bone model loaded in a neutral position. The influence of tibial material and design on the periprosthetic bone strain response was investigated under the peak loads of walking and stair descending/ascending. Two of the models were also modified to examine the effect of selected implant malalignment conditions (7° posterior, 5° valgus and 5° varus) on stress shielding in the bone, where the medio-lateral load share ratios were adjusted accordingly. The predicted increases of bone density due to implantation for the selected cases studied were also presented. For the cases examined, the effect of stress shielding on the periprosthetic bone seems to be more significantly influenced by the implant material than by the implant geometry. Significant stress shielding is found in MB cases, as opposed to increase in bone density found in AP cases, particularly in the bones immediately beneath the baseplate. The effect of stress shielding is reduced somewhat for the MB components in the malaligned positions compared with the neutral case. In AP cases, the effect of stress shielding is mostly low except in the varus position, possibly due to off-loading of lateral condyle. Increases in bone density are found in both MB and AP cases for the malaligned conditions.
针对全膝关节置换术（TKR）的一些典型案例，研究了假体周围骨应变分布情况，涉及材料选择、设计以及胫骨组件的对线情况，以考察哪些条件对TKR术后应力遮挡的耐受性更强。在一个特定标本的有限元胫骨骨模型中，考虑了四种具有两种植入物设计（后交叉韧带牺牲型和后交叉韧带保留型）以及材料特性（金属背衬（MB）和全聚乙烯（AP））的胫骨组件，并使其处于中立位置加载。研究了在行走和上下楼梯的峰值负荷下，胫骨材料和设计对假体周围骨应变响应的影响。还对其中两个模型进行了修改，以考察选定的植入物排列不齐情况（后倾7°、外翻5°和内翻5°）对骨应力遮挡的影响，并相应调整了内外侧负荷分担比例。还给出了所选研究案例中植入后骨密度的预测增加情况。对于所检查的案例，应力遮挡对假体周围骨的影响似乎受植入物材料的影响比受植入物几何形状的影响更大。在MB案例中发现了显著的应力遮挡，而在AP案例中发现骨密度增加，尤其是在基板下方紧邻的骨骼中。与中立情况相比，排列不齐位置的MB组件的应力遮挡效应有所降低。在AP案例中，除了内翻位置外，应力遮挡效应大多较低，这可能是由于外侧髁卸载所致。在排列不齐的情况下，MB和AP案例中均发现骨密度增加。
