Department of Orthopaedic Surgery, Gunma University Graduate School of Medicine, Maebashi, Japan.
Department of Orthopaedic Surgery, Saint Pierre Hospital, Takasaki, Japan.
Am J Sports Med. 2018 May;46(6):1416-1423. doi: 10.1177/0363546518758313. Epub 2018 Mar 20.
Supraspinatus muscle atrophy is typically assessed by the occupation ratio of the cross-sectional area of the muscle belly to the supraspinatus fossa at the medial border of the coracoid process in a slice along the oblique-sagittal plane on MRI. Previous studies have shown that the occupation ratio of the supraspinatus changed soon after rotator cuff repair compared with before surgery. However, no studies have examined the perioperative change in the muscle volume assessed with 3-dimensional measurement.
To compare the volume of the supraspinatus muscle before and soon after surgery by using 3-dimensional imaging and to elucidate whether the changes in the occupation ratio represent corresponding changes in the muscle volume.
Cohort study; Level of evidence, 3.
Thirty shoulders of patients who underwent arthroscopic rotator cuff repair were evaluated. T2-weighted images were obtained before surgery and 2 weeks after surgery. After the muscle and its tendon borders were plotted, the supraspinatus and its tendon were segmented with interactive thresholding in all slices. The 3-dimensional images were then reconstructed and the volumes calculated. Changes in the muscle volume and the occupation ratio were evaluated via 3-dimensional and 2-dimensional image assessments. The 3-dimensional and 2-dimensional findings before and after surgery were compared by use of paired t tests.
The mean muscle volume did not change significantly at a time point soon after surgery in any group. In patients with little medial retraction (n = 7) or isolated detachment at the superior facet (n = 17), no significant differences were noted in the occupation ratio after surgery compared with before surgery. In contrast, in patients with moderate medial retraction (n = 23) or extended tearing in the transverse direction (n = 13), the occupation ratio increased significantly.
Although the muscle volume did not change soon after surgery compared with the preoperative values, in patients with moderate medial retraction or extended tearing in the transverse direction, the occupation ratio increased, probably due to lateral traction of the supraspinatus muscle. We recommend that MRI findings obtained soon after surgery be used as the time-zero reference for evaluating the postoperative changes in the supraspinatus.
冈上肌萎缩通常通过 MRI 斜矢状位层面上喙突内侧缘的肩胛冈窝内冈上肌肌腹的横截面积与冈上肌窝的截面积之比来评估。既往研究显示，与术前相比，肩袖修补术后冈上肌的截面积比值很快发生变化。然而，尚无研究检测用三维测量评估的冈上肌体积的围手术期变化。
使用三维成像比较手术前后冈上肌的体积，并阐明截面积的变化是否代表肌肉体积的相应变化。
队列研究；证据等级，3 级。
评估了 30 例接受关节镜下肩袖修补术的患者的 30 个肩关节。在术前和术后 2 周时获取 T2 加权图像。绘制肌肉及其肌腱边界后，在所有层面上通过交互式阈值分割冈上肌及其肌腱。然后重建三维图像并计算体积。通过三维和二维图像评估评估肌肉体积和截面积的变化。使用配对 t 检验比较手术前后的三维和二维结果。
在任何一组中，术后即刻肌肉体积均无明显变化。在轻度内侧回缩（n = 7）或单纯上关节面分离（n = 17）的患者中，术后与术前相比，截面积比无明显差异。相比之下，在中度内侧回缩（n = 23）或横向广泛撕裂（n = 13）的患者中，截面积比显著增加。
尽管与术前值相比，术后即刻肌肉体积没有变化，但在中度内侧回缩或横向广泛撕裂的患者中，截面积比增加，可能是由于冈上肌的外侧牵拉所致。我们建议将术后即刻获得的 MRI 结果用作评估冈上肌术后变化的时间零参考。
