Department of Orthopaedic Surgery, SUNY Upstate Medical University, 3216 IHP, 750 East Adams Street, Syracuse, NY, 13210, USA.
Clin Orthop Relat Res. 2014 Jan;472(1):304-13. doi: 10.1007/s11999-013-3248-4. Epub 2013 Aug 24.
Aseptic loosening continues to be a short- and long-term complication for patients with cemented TKAs. Most studies to this point have evaluated tibial component fixation via radiographic changes at the implant-bone interface and quantification of component migration; direct assessment of morphologic features of the interface from functioning TKAs may provide new information regarding how TKAs function and are fixed to bone.
QUESTIONS/PURPOSES: In a postmortem retrieval study, we asked: (1) What are the morphologic features at the cement-trabecular bone interface in retrieved tibial components? (2) Do constructs with greater time in service have less cement-trabecular bone interlock? (3) Do constructs with more estimated initial interlock sustain more interlock with in vivo service?
Fourteen postmortem retrieved tibial components with time in service from 0 to 20 years were sectioned and imaged at high resolution, and the current contact fraction, estimated initial interdigitation depth, current interdigitation depth, and loss of interdigitation depth were quantified at the cement-bone interface. Estimated initial interdigitation depth was calculated from the initial mold shape of the cement mantle that forms around the individual trabeculae at the time of surgery. Loss of interdigitation depth was the difference between the initial and current interdigitation depth.
There was resorption of trabeculae that initially interlocked with the cement in the postmortem retrievals as evidenced by the differences between current interdigitation and the estimated original interdigitation. The current contact fraction (r(2) = 0.54; p = 0.0027) and current interdigitation depth (r(2) = 0.33; p = 0.033) were less for constructs with longer time in service. The current contact fraction for implants with 10 or more years in service (6.2%; 95% CI, 4.7%-7.7%) was much less than implants with less than 10 years in service (22.9%; 95% CI, 8.9%-37%). Similarly, the current interdigitation depth for implants with 10 or more years in service (0.4 mm; 95% CI, 0.27-0.53 mm) was much less than implants with less than 10 years in service (1.13 mm; 95% CI, 0.48-1.78 mm). The loss of interdigitation depth had a strong positive relationship with time in service (r(2) = 0.74; p < 0.001). Using a two-parameter regression model, constructs with more initial interdigitation depth had greater current interdigitation depth (p = 0.011), but constructs with more time in service also had less current interdigitation depth (p = 0.008).
The cement-trabecular bone interlock obtained initially appears to diminish with time with in vivo service by resorption of the trabeculae in the cement interlock region.
Our study supports the surgical concept of obtaining sufficient initial cement interlock (approximately 3 mm), with the acknowledgment that there will be loss of interlock with time with in vivo service.
对于接受过水泥固定 TKA 的患者来说，无菌性松动仍然是一个短期和长期的并发症。到目前为止，大多数研究都通过在植入物-骨界面上的影像学变化和对组件迁移的量化来评估胫骨组件的固定情况；从功能 TKA 直接评估界面的形态特征可能会提供有关 TKA 如何工作以及与骨骼固定的新信息。
问题/目的：在一项尸体检索研究中，我们提出了以下问题：（1）从检索到的胫骨组件中，水泥-小梁骨界面的形态特征是什么？（2）使用时间较长的结构是否具有较少的水泥-小梁骨互锁？（3）具有更多初始互锁的结构在体内使用时是否能保持更多的互锁？
对 14 个时间从 0 年到 20 年不等的尸体检索胫骨组件进行分段和高分辨率成像，并在水泥-骨界面上对当前接触分数、估计初始互锁深度、当前互锁深度和互锁深度损失进行量化。估计初始互锁深度是从手术时围绕单个小梁形成的水泥覆盖层的初始模具形状计算得出的。互锁深度损失是初始互锁深度和当前互锁深度之间的差异。
正如当前互锁与估计原始互锁之间的差异所证明的那样，尸体检索中的小梁发生了吸收，从而与水泥发生了互锁。使用时间较长的结构的当前接触分数（r²=0.54；p=0.0027）和当前互锁深度（r²=0.33；p=0.033）较低。使用时间在 10 年或以上的植入物的当前接触分数（6.2%；95%CI，4.7%-7.7%）远低于使用时间在 10 年以下的植入物（22.9%；95%CI，8.9%-37%）。同样，使用时间在 10 年或以上的植入物的当前互锁深度（0.4mm；95%CI，0.27-0.53mm）远低于使用时间在 10 年以下的植入物（1.13mm；95%CI，0.48-1.78mm）。互锁深度损失与使用时间呈很强的正相关（r²=0.74；p<0.001）。使用双参数回归模型，具有更多初始互锁深度的结构具有更大的当前互锁深度（p=0.011），但使用时间较长的结构的当前互锁深度也较低（p=0.008）。
水泥-小梁骨互锁在体内使用过程中似乎随着时间的推移而减少，这是由于水泥互锁区域内小梁的吸收所致。
我们的研究支持获得足够初始水泥互锁（约 3mm）的手术概念，同时承认随着体内使用时间的推移，互锁会丢失。
