Laboratory of Biomechanical Orthopedics, Ecole Polytechnique Fédérale de Lausanne, Station 9, 1015 Lausanne, Switzerland.
Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
Med Eng Phys. 2020 Nov;85:48-54. doi: 10.1016/j.medengphy.2020.09.009. Epub 2020 Sep 28.
Glenoid implant loosening remains a major source of failure and concern after anatomical total shoulder arthroplasty (aTSA). It is assumed to be associated with eccentric loading and excessive bone strain, but direct measurement of bone strain after aTSA is not available yet. Therefore, our objective was to develop an in vitro technique for measuring bone strain around a loaded glenoid implant. A custom loading device (1500 N) was designed to fit within a micro-CT scanner, to use digital volume correlation for measuring displacement and calculating strain. Errors were evaluated with three pairs of unloaded scans. The average displacement random error of three pairs of unloaded scans was 6.1 µm. Corresponding systematic and random errors of strain components were less than 806.0 µε and 2039.9 µε, respectively. The average strain accuracy (MAER) and precision (SDER) were 694.3 µε and 440.3 µε, respectively. The loaded minimum principal strain (8738.9 µε) was 12.6 times higher than the MAER (694.3 µε) on average, and was above the MAER for most of the glenoid bone volume (98.1%). Therefore, this technique proves to be accurate and precise enough to eventually compare glenoid implant designs, fixation techniques, or to validate numerical models of specimens under similar loading.
肩盂假体松动仍然是解剖型全肩关节置换术后（aTSA）失败和关注的主要原因。人们认为它与偏心载荷和过度的骨应变有关，但目前还没有直接测量 aTSA 后骨应变的方法。因此，我们的目标是开发一种测量负载肩盂假体周围骨应变的体外技术。设计了一种定制的加载装置（1500N），可安装在 micro-CT 扫描仪内，使用数字体素相关技术测量位移并计算应变。使用三对空载扫描评估误差。三对空载扫描的平均位移随机误差为 6.1µm。应变分量的相应系统和随机误差分别小于 806.0µε和 2039.9µε。平均应变准确度（MAER）和精度（SDER）分别为 694.3µε和 440.3µε。加载后的最小主应变（8738.9µε）平均比 MAER（694.3µε）高 12.6 倍，并且在大多数肩盂骨体积（98.1%）中高于 MAER。因此，该技术证明足够准确和精确，最终可以比较肩盂假体设计、固定技术，或验证类似载荷下标本的数值模型。
