Bryan J M, Sumner D R, Hurwitz D E, Tompkins G S, Andriacchi T P, Galante J O
Department of Orthopedic Surgery, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612, USA.
J Orthop Res. 1996 Sep;14(5):762-8. doi: 10.1002/jor.1100140513.
Dual energy x-ray absorptiometry was used to measure periprosthetic, distal femoral, and proximal tibial bone mass in the affected and contralateral limbs of eight patients 10 years after unilateral total hip arthroplasty with a cementless, porous-coated titanium alloy femoral stem. Gait analyses to assess the presence of asymmetries in loading of the lower extremities were also performed 10 years postoperatively. The patients had excellent clinical results and no other significant lower extremity pathology. On the basis of comparison of the affected and unaffected proximal femora, bone loss adjacent to the proximal medial aspect of the femoral stem was determined to be 34% (p < 0.001). However, the patients also had 16% less bone in the ipsilateral proximal tibia (p = 0.003) and 15% less bone in the ipsilateral femur 3 cm distal to the prosthesis (p = 0.007) compared with the contralateral limb. When normalized to the asymmetry in tibial bone mineral content, the estimated proximal medial periprosthetic bone loss was still statistically significant, but the magnitude was reduced from 34 to 17% (p = 0.009). The gait analyses indicated that several measures that influence the loads at the hip and knee joints were reduced in the involved limb compared with the contralateral limb. Furthermore, the bilateral difference in the vertical component of the external force acting on the proximal tibia was correlated with the bilateral difference in tibial bone mineral content (r = 0.80, p = 0.02). These data suggest that two mechanical factors, the local stress-shielding effect of the prosthesis and the global effect of decreased loading of the limb, can both make significant contributions to periprosthetic bone loss. It is apparent that the magnitude of the periprosthetic bone loss related to stress-shielding has been overestimated by as much as 50% in retrospective studies.
在8例患者接受单侧全髋关节置换术并使用无骨水泥、多孔涂层钛合金股骨柄10年后，采用双能X线吸收法测量患侧和对侧肢体的假体周围、股骨远端和胫骨近端骨量。术后10年还进行了步态分析，以评估下肢负重是否存在不对称。患者临床效果良好，且无其他明显的下肢病变。通过比较患侧和未患侧股骨近端，确定股骨柄近端内侧相邻部位的骨丢失为34%（p < 0.001）。然而，与对侧肢体相比，患者同侧胫骨近端骨量减少了16%（p = 0.003），假体远端3 cm处同侧股骨骨量减少了15%（p = 0.007）。当根据胫骨骨矿物质含量的不对称性进行归一化处理后，估计的假体近端内侧骨丢失仍具有统计学意义，但幅度从34%降至17%（p = 0.009）。步态分析表明，与对侧肢体相比，患侧肢体中影响髋关节和膝关节负荷的几项指标有所降低。此外，作用于胫骨近端的外力垂直分量的双侧差异与胫骨骨矿物质含量的双侧差异相关（r = 0.80，p = 0.02）。这些数据表明，两个机械因素，即假体的局部应力遮挡效应和肢体负荷降低的整体效应，均可对假体周围骨丢失产生显著影响。显然，在回顾性研究中，与应力遮挡相关的假体周围骨丢失幅度被高估了多达50%。
