Greaves L L, Gilbart M K, Yung A, Kozlowski P, Wilson D R
Division of Orthopaedic Engineering Research, University of British Columbia, Vancouver, BC, Canada.
J Biomech. 2009 Feb 9;42(3):349-54. doi: 10.1016/j.jbiomech.2008.11.025. Epub 2009 Jan 14.
Accurate measurement of cartilage deformation in loaded cadaver hip joints could be a valuable tool to answer clinically relevant research questions. MRI is a promising tool, but its use requires an understanding of cartilage deformation and recovery properties in the intact hip. Our objective was to answer the following questions: (1) How long does it take for hip cartilage to reach a deformed steady-state thickness distribution under simulated physiological load, and how much does the cartilage deform? (2) How long does it take for hip cartilage to return to the original cartilage thickness distribution once the load is removed?
Five human hip specimens were axially loaded to 1980N in a 7T MR scanner and scanned every 15min throughout loading. One specimen was scanned every hour throughout recovery from load. One repeatability specimen was loaded and scanned every day for 4 days. Hip cartilage was segmented as a single unit and thickness was measured radially.
The hip cartilage reached a steady-state thickness distribution after 225min of load, and 16.5h of recovery. Mean strain after 225min of load was 30.9%. The repeatability specimen showed an average day-to-day change in mean cartilage thickness of 0.10mm over 4 days of data collection. The amount of deformation (0.96mm) was far greater than the image resolution (0.11mm) and error due to repeatability (0.10mm).
Using an ex vivo model, this method has potential for assessing changes in hip cartilage strain due to injury or surgical intervention.
准确测量加载的尸体髋关节软骨变形情况，可能是回答临床相关研究问题的一个有价值的工具。磁共振成像（MRI）是一种很有前景的工具，但其使用需要了解完整髋关节中软骨的变形和恢复特性。我们的目的是回答以下问题：（1）在模拟生理负荷下，髋关节软骨达到变形稳态厚度分布需要多长时间，软骨会变形多少？（2）负荷去除后，髋关节软骨恢复到原始软骨厚度分布需要多长时间？
在7T磁共振扫描仪中，对五个人类髋关节标本轴向加载至1980N，并在整个加载过程中每隔15分钟扫描一次。在负荷恢复过程中，每隔一小时对一个标本进行扫描。对一个重复性标本每天加载并扫描，持续4天。将髋关节软骨作为一个整体进行分割，并径向测量厚度。
负荷225分钟后，髋关节软骨达到稳态厚度分布，恢复时间为16.5小时。负荷225分钟后的平均应变率为30.9%。重复性标本在4天的数据收集过程中，平均软骨厚度的每日平均变化为0.10mm。变形量（0.96mm）远大于图像分辨率（0.11mm）和重复性误差（0.10mm）。
使用离体模型，该方法有潜力评估因损伤或手术干预导致的髋关节软骨应变变化。
