Yang J P, Bogoch E R, Woodside T D, Hearn T C
Department of Surgery, University of Toronto, Ontario, Canada.
J Arthroplasty. 1997 Oct;12(7):798-803. doi: 10.1016/s0883-5403(97)90011-5.
Stiffness of subchondral proximal tibial trabecular bone is a factor in the stability of prostheses implanted into that bone. The stiffness of trabecular bone in osteoarthritis (OA) has been documented. Trabecular bone in rheumatoid arthritis (RA) is osteopenic in numerous sites and morphologically abnormal in the proximal tibia. Reliable data on proximal tibial bone in RA are lacking, although 1 study failed to identify abnormalities. The purposes of this study were (1) to document the stiffness of the proximal tibial cancellous bone in patients with RA, (2) to determine the effect of angular deformity on bone stiffness in rheumatoid patients, and (3) to compare RA stiffness values with those in published reports for OA. Fifteen tibial plateau were obtained from patients with RA during surgery. Each plateau was horizontally seated in a mold and covered with cement. The plateau was divided into 6 regions, which were used to facilitate comparison between specimens and the existing literature. Indentation tests were conducted with a 4-mm-diameter cylindrical indentor controlled by an MTS machine. The indentor descended at a rate of 2 mm/min to a maximum depth of 1.0 mm; load and displacement data were digitally recorded. Stiffness was calculated from the slope of the linear region of the curve using best-fit linear regression. Where varus deformity was present, stiffness in the medial plateau was higher overall than for the other compartment; whereas in the case of valgus deformity, stiffness of the lateral side was significantly higher (P < .05 for each observation). In comparison to older normal specimens, both the medial compartment of the varus RA specimens (P < .01) and the posterolateral compartment of the valgus RA specimens (P < .01) had significantly lower stiffness. Comparison with OA specimens showed that in varus RA, the posteromedial region had significantly lower stiffness than in varus OA at the same site (P < .01). In valgus RA, the lateral region had significantly lower stiffness than in valgus OA at the same site (P < .01). The mean stiffness ratio of the valgus RA was significantly (P < .01) altered from normal, and for the varus RA, it was significantly (P < .01) different from normal posteriorly. The stiffness ratios for the varus RA were significantly (P < .01) different from those for varus OA; there was no difference between valgus RA and valgus OA. It is concluded that RA affected bone has significantly lower stiffness than normal and osteoarthritic bone. The loaded plateau is stiffer than the unloaded plateau in angular deformity, but is still less stiff than normal bone and osteoarthritic plateaus with corresponding deformities.
胫骨近端软骨下小梁骨的硬度是植入该骨的假体稳定性的一个因素。骨关节炎（OA）中小梁骨的硬度已有文献记载。类风湿关节炎（RA）中的小梁骨在许多部位存在骨质减少，且胫骨近端在形态上异常。虽然有一项研究未发现异常，但关于RA中胫骨近端骨的可靠数据仍然缺乏。本研究的目的是：（1）记录RA患者胫骨近端松质骨的硬度；（2）确定角度畸形对类风湿患者骨硬度的影响；（3）将RA的硬度值与已发表的OA报告中的值进行比较。在手术过程中从RA患者获取了15个胫骨平台。每个平台水平放置在模具中并用水泥覆盖。将平台分为6个区域，以方便标本之间以及与现有文献进行比较。使用由MTS机器控制的直径4毫米的圆柱形压头进行压痕试验。压头以2毫米/分钟的速度下降至最大深度1.0毫米；载荷和位移数据进行数字记录。使用最佳拟合线性回归从曲线的线性区域的斜率计算硬度。在存在内翻畸形的情况下，内侧平台的硬度总体上高于其他区域；而在外翻畸形的情况下，外侧的硬度明显更高（每次观察P < .05）。与正常的老年标本相比，内翻RA标本的内侧区域（P < .01）和外翻RA标本的后外侧区域（P < .01）的硬度均显著较低。与OA标本比较显示，在内翻RA中，后内侧区域在同一部位的硬度明显低于内翻OA（P < .01）。在外翻RA中，外侧区域在同一部位的硬度明显低于外翻OA（P < .01）。外翻RA的平均硬度比与正常相比有显著改变（P < .01），内翻RA的平均硬度比与正常相比在后方有显著差异（P < .01）。内翻RA的硬度比与内翻OA的硬度比有显著差异（P < .01）；外翻RA与外翻OA之间无差异。结论是，RA累及的骨的硬度明显低于正常骨和骨关节炎的骨。在角度畸形中，加载的平台比未加载的平台更硬，但仍比具有相应畸形的正常骨和骨关节炎平台更软。
