van Loon C J, de Waal Malefijt M C, Buma P, Verdonschot N, Veth R P
Department of Orthopedics, University Hospital Nijmegen, The Netherlands.
Acta Orthop Belg. 1999 Jun;65(2):154-63.
Femoral bone loss in total knee arthroplasty (TKA) is a common feature and is mainly attributed to three etiological factors. Stress shielding causes an "osteopenia" type of bone loss behind the anterior flange and adjacent to the distal aspects of the femoral component. Using dual-energy x-ray absorptiometry, decrease in bone mineral density up to 44% has been measured in these areas. Secondly, polyethylene, cement and metal particles are released by implant wear and may cause the less common "osteolysis" type of bone loss located directly at the anterior and posterior implant-cement-bone interfaces. This type of bone loss occurs mainly in young, male, overweight patients with osteoarthritis. Finally, implant loosening leads to bone loss at the bone cement-implant interface and results in "hollowing out" of the distal femur in a stemmed TKA. Femoral bone loss may be reduced by diminishing the stress-shielding effect, by improving the quality of the polyethylene insert, and by decreasing the rate of implant loosening still further. In revision TKA, femoral bone loss is often underestimated in the preoperative radiographs. Classification of bone loss should be made during surgery, and should be based upon the size of the defect generated and the grade of containment. The choice among cement filling, metal augmentation, custom-made TKA, solid bone grafts, and morsellized bone grafts in reconstruction of bone defects will depend upon the type of bone loss, the bone quality, the surgeon's preference and philosophy, and the availability of grafts and implants.
全膝关节置换术（TKA）中股骨骨丢失是一个常见特征，主要归因于三个病因。应力遮挡导致前凸缘后方以及股骨假体远端相邻区域出现“骨质减少”型骨丢失。使用双能X线吸收法测量，这些区域的骨矿物质密度下降高达44%。其次，聚乙烯、骨水泥和金属颗粒因植入物磨损而释放，可能导致较不常见的“骨溶解”型骨丢失，这种骨丢失直接位于植入物 - 骨水泥 - 骨界面的前后方。这种类型的骨丢失主要发生在患有骨关节炎的年轻、男性、超重患者中。最后，植入物松动导致骨水泥 - 植入物界面处的骨丢失，并在有柄TKA中导致股骨远端“空洞化”。通过减少应力遮挡效应、提高聚乙烯衬垫质量以及进一步降低植入物松动率，可以减少股骨骨丢失。在翻修TKA中，术前X线片往往低估股骨骨丢失情况。骨丢失的分类应在手术期间进行，且应基于所产生缺损的大小和包容程度分级。在骨缺损重建中，骨水泥填充、金属增强、定制TKA、整块骨移植和碎骨移植之间的选择将取决于骨丢失的类型、骨质、外科医生的偏好和理念以及移植材料和植入物的可用性。
