MQ Health Translational Shoulder Research Program, Faculty of Medicine & Health Sciences, Macquarie University, Sydney, NSW, Australia.
MQ Health Translational Shoulder Research Program, Faculty of Medicine & Health Sciences, Macquarie University, Sydney, NSW, Australia.
J Shoulder Elbow Surg. 2022 Dec;31(12):e575-e585. doi: 10.1016/j.jse.2022.06.008. Epub 2022 Jul 22.
A transverse force couple (TFC) functional imbalance has been demonstrated in osteoarthritic shoulders by recent 3-dimensional (3D) muscle volumetric studies. Altered rotator cuff vectors may be an additional factor contributing to a muscle imbalance and the propagation of glenoid deformity.
Computed tomography images of 33 Walch type A and 60 Walch type B shoulders were evaluated. The 3D volumes of the entire subscapularis, supraspinatus, and infraspinatus-teres minor (ISP-Tm) and scapula were manually segmented. The volume masks and scapular landmarks were imported into MATLAB to create a coordinate system, enabling calculation of muscle force vectors. The direction of each muscle force vector was described in the transverse and vertical plane, calculated with respect to the glenoid. Each muscle vector was then resolved into compression and shear force across the glenoid face. The relationship between muscle force vectors, glenoid retroversion or inclination, compression/shear forces on the glenoid, and Walch type was determined using linear regression.
In the transverse plane with all rotator cuff muscles combined, increasing retroversion was significantly associated with increasing posterior drag (P < .001). Type B glenoids had significantly more posterior drag than type A (P < .001). In the vertical plane for each individual muscle group and in combination, superior drag increases as superior inclination increases (P < .001). Analysis of individual muscle groups showed that the anterior thrust of ISP-Tm and supraspinatus switched to a posterior drag at 8° and 10° of retroversion respectively. The compression force on the glenoid face by ISP-Tm and supraspinatus did not change with increasing retroversion for type A shoulders (P = .592 and P = .715, respectively), but they did for type B shoulders (P < .001 for both). The glenoid shear force ratio in the transverse plane for the ISP-Tm and supraspinatus moved from anterior to posterior shear with increasing glenoid retroversion, crossing zero at 8° and 10° of retroversion, whereas the subscapularis exerted a posterior shear force for every retroversion angle.
Increased glenoid retroversion is associated with increased posterior shear and decreased compression forces on the glenoid face, explaining some of the pathognomonic bone morphometrics that characterize the osteoarthritic shoulder. Although the subscapularis always maintains a posterior thrust, the ISP-Tm and supraspinatus together showed an inflection at 8° and 10° of retroversion, changing from an anterior thrust to a posterior drag. This finding highlights the importance that in anatomic TSA the rotator cuff functional balance might be better restored by correcting glenoid retroversion to less than 8°.
最近的三维（3D）肌肉容积研究表明，骨关节炎肩关节存在横向力偶（TFC）功能失衡。肩袖的改变可能是导致肌肉失衡和肩盂变形传播的另一个因素。
评估了 33 例 Walch 型 A 和 60 例 Walch 型 B 肩关节的计算机断层扫描图像。使用手动分割方法对整个肩胛下肌、冈上肌和冈下肌-小圆肌（ISP-Tm）和肩胛的整个 3D 体积进行分割。将体积掩模和肩胛标记导入 MATLAB 以创建坐标系，从而能够计算肌肉力向量。每个肌肉力向量的方向在横平面和矢状面中进行描述，相对于肩盂进行计算。然后，将每个肌肉向量分解为穿过肩盂表面的压缩力和剪切力。使用线性回归确定肌肉力向量、肩盂后倾或倾斜、肩盂上的压缩/剪切力与 Walch 类型之间的关系。
在所有肩袖肌肉合并的横平面中，随着后倾的增加，后向牵拉显著增加（P<.001）。B 型肩盂的后向牵拉明显大于 A 型（P<.001）。在垂直平面中，对于每个单独的肌肉群以及合并的肌肉群，随着上倾的增加，上向牵拉增加（P<.001）。分析各个肌肉群显示，ISP-Tm 和冈上肌的前推力在 8°和 10°的后倾时分别转变为后向牵拉。对于 A 型肩盂，ISP-Tm 和冈上肌的肩盂表面压缩力不随后倾增加而变化（P=.592 和 P=.715），但对于 B 型肩盂则随后倾增加而变化（P<.001）。在横平面中，ISP-Tm 和冈上肌的肩盂剪切力比从前向剪切力变为后向剪切力，在 8°和 10°的后倾时变为零，而肩胛下肌在每个后倾角度都产生后向剪切力。
增加的肩盂后倾与肩盂表面的后向剪切力增加和压缩力减小有关，这解释了一些特征性的骨关节炎肩关节的骨骼形态学特征。尽管肩胛下肌始终保持后推力，但 ISP-Tm 和冈上肌在 8°和 10°的后倾时出现拐点，从前向推力变为后向牵拉。这一发现强调了在解剖学全肩关节置换术中，通过将肩盂后倾纠正至小于 8°，可能更好地恢复肩袖的功能平衡。
