Wolf Orthopaedic Biomechanics Laboratory, Fowler Kennedy Sport Medicine Clinic, London, Ontario, Canada.
J Biomech. 2010 May 28;43(8):1527-31. doi: 10.1016/j.jbiomech.2010.01.043. Epub 2010 Feb 23.
When performing radiostereometric analysis (RSA), computed tomography scans are often taken to obtain the landmarks used to create anatomical coordinate systems (CSs) for quantifying joint kinematics. Different conventions for defining CSs lead to an inability to compare results among studies. The International Society of Biomechanics (ISB) has proposed a set of CSs; however, the landmarks needed to create the recommended scapular CS require the entire scapula to be scanned, thereby also exposing breast and other tissues to radiation. The main purpose of this work was to investigate an alternate definition of the CS that has repeatably attainable landmarks and axes as close as possible to those recommended by the ISB, while limiting the portion of the scapula requiring scanning. Intra- and inter-investigator variabilities of landmark digitization were quantified in one model of a scapula and one cadaveric specimen. Based on the variability of the digitizations, an alternative CS was defined. The differences between the ISB and alternative CSs were evaluated on 11 cadaveric specimens. Beaded biplanar RSA was performed on the glenohumeral joint model in 15 different configurations and the resulting kinematics were calculated for each set of landmark digitizations using both sets of coordinate systems. While the kinematic angles obtained using the alternative CS were statistically different from those obtained using the ISB standard, these differences were small (on the order of 5 degrees) and therefore considered to be of little clinical significance. In all likelihood, the benefits of decreasing radiation exposure outweigh these differences in angles.
在进行放射立体测量分析 (RSA) 时，通常需要进行计算机断层扫描以获取用于创建解剖坐标系 (CS) 的地标，以量化关节运动学。不同的 CS 定义约定导致无法在研究之间进行结果比较。国际生物力学学会 (ISB) 提出了一组 CS；然而，创建推荐的肩胛 CS 所需的地标需要扫描整个肩胛骨，从而也使乳房和其他组织暴露在辐射下。这项工作的主要目的是研究一种替代 CS 的定义，该定义具有可重复获得的地标和轴，尽可能接近 ISB 推荐的 CS，同时限制需要扫描的肩胛骨部分。在一个肩胛骨模型和一个尸体标本中量化了地标数字化的内部和内部调查员变异性。基于数字化的可变性，定义了替代 CS。在 11 个尸体标本上评估了 ISB 和替代 CS 之间的差异。在 15 种不同配置下对肩胛盂肱关节模型进行了珠状双平面 RSA，并使用两组坐标系为每组地标数字化计算了由此产生的运动学。虽然替代 CS 获得的运动学角度与使用 ISB 标准获得的角度在统计学上有所不同，但这些差异很小（约 5 度），因此被认为临床意义不大。很可能，减少辐射暴露的好处超过了这些角度的差异。
