Department of Biomedical Engineering and Orthopedic and Rheumatologic Research Center, Cleveland Clinic, Cleveland, OH 44195, USA.
J Biomech. 2012 Feb 2;45(3):614-8. doi: 10.1016/j.jbiomech.2011.11.046. Epub 2011 Dec 12.
Previous studies have used radiostereometric analysis (RSA) to assess the integrity and mechanical properties of repaired tendons and ligament grafts. A conceptually similar approach is to use CT imaging to measure the 3D position and distance between implanted markers. The purpose of this study was to quantify the accuracy and repeatability of measuring the position and distance between metallic markers placed in the rotator cuff using low-dose CT imaging. We also investigated the effect of repeated or variable positions of the arm on position and distance measures. Six human patients had undergone rotator cuff repair and placement of tantalum beads in the rotator cuff at least one year prior to participating in this study. On a single day each patient underwent nine low-dose CT scans in seven unique arm positions. CT scans were analyzed to assess bias, precision and RMS error of the measurement technique. The effect of repeated or variable positions of the arm on the 3D position of the beads and the distance between these beads and suture anchors in the humeral head were also assessed. Results showed the CT imaging method is accurate and repeatable to within 0.7 mm. Further, measures of bead position and anchor-to-bead distance are influenced by arm position and location of the bead within the rotator cuff. Beads located in the posterior rotator cuff moved medially as much as 20 mm in abduction or external rotation. When clinically relevant CT arm positions such as the hand on umbilicus or at side were repeated, bead position varied less than 4 mm in any anatomic direction and anchor-to-bead distance varied +2.8 to -1.6 mm (RMS 1.3 mm). We conclude that a range of ± 3 mm is a conservative estimate of the uncertainty in anchor-to-bead distance for patients repeatedly scanned in clinically-relevant arm positions.
先前的研究已经使用放射立体测量分析（RSA）来评估修复后的肌腱和韧带移植物的完整性和机械性能。一种类似的概念是使用 CT 成像来测量植入标记物的三维位置和距离。本研究的目的是量化使用低剂量 CT 成像测量肩袖内植入金属标记物的位置和距离的准确性和可重复性。我们还研究了手臂重复或可变位置对位置和距离测量的影响。六名患者在参与本研究之前至少一年接受了肩袖修复和肩袖内钽珠的放置。每位患者在一天内进行了九次低剂量 CT 扫描，扫描了七个独特的手臂位置。对 CT 扫描进行了分析，以评估测量技术的偏差、精度和 RMS 误差。还评估了手臂重复或可变位置对珠的三维位置以及这些珠与肱骨头上缝合锚之间的距离的影响。结果表明，CT 成像方法的准确性和可重复性在 0.7 毫米以内。此外，珠的位置和珠与锚之间的距离测量值受手臂位置和珠在肩袖内的位置的影响。外展或外旋时，位于肩袖后部的珠向内侧移动多达 20 毫米。当重复临床相关的 CT 手臂位置（例如手放在脐部或侧面）时，珠的位置在任何解剖方向上的变化都小于 4 毫米，而珠与锚之间的距离变化为+2.8 至-1.6 毫米（RMS 为 1.3 毫米）。我们得出结论，对于在临床相关手臂位置重复扫描的患者，珠与锚之间距离的不确定性的保守估计值为±3 毫米。
