Hôpital Ambroise Paré, Boulogne-Billancourt, France.
Imascap, Plouzané, France.
J Shoulder Elbow Surg. 2024 Jul;33(7):1493-1502. doi: 10.1016/j.jse.2023.11.027. Epub 2024 Jan 17.
The etiology of humeral posterior subluxation remains unknown, and it has been hypothesized that horizontal muscle imbalance could cause this condition. The objective of this study was to compare the ratio of anterior-to-posterior rotator cuff and deltoid muscle volume as a function of humeral subluxation and glenoid morphology when analyzed as a continuous variable in arthritic shoulders.
In total, 333 computed tomography scans of shoulders (273 arthritic shoulders and 60 healthy controls) were included in this study and were segmented automatically. For each muscle, the volume of muscle fibers without intramuscular fat was measured. The ratio between the volume of the subscapularis and the volume of the infraspinatus plus teres minor (AP ratio) and the ratio between the anterior and posterior deltoids (AP) were calculated. Statistical analyses were performed to determine whether a correlation could be found between these ratios and glenoid version, humeral subluxation, and/or glenoid type per the Walch classification.
Within the arthritic cohort, no statistically significant difference in the AP ratio was found between type A glenoids (1.09 ± 0.22) and type B glenoids (1.03 ± 0.16, P = .09), type D glenoids (1.12 ± 0.27, P = .77), or type C glenoids (1.10 ± 0.19, P > .999). No correlation was found between the AP ratio and glenoid version (ρ = -0.0360, P = .55) or humeral subluxation (ρ = 0.076, P = .21). The AP ratio of type A glenoids (0.48 ± 0.15) was significantly greater than that of type B glenoids (0.35 ± 0.16, P < .01) and type C glenoids (0.21 ± 0.10, P < .01) but was not significantly different from that of type D glenoids (0.64 ± 0.34, P > .999). When evaluating both healthy control and arthritic shoulders, moderate correlations were found between the AP ratio and both glenoid version (ρ = 0.55, P < .01) and humeral subluxation (ρ = -0.61, P < .01).
This in vitro study supports the use of software for fully automated 3-dimensional reconstruction of the 4 rotator cuff muscles and the deltoid. Compared with previous 2-dimensional computed tomography scan studies, our study did not find any correlation between the anteroposterior muscle volume ratio and glenoid parameters in arthritic shoulders. However, once deformity occurred, the observed AP ratio was lower with type B and C glenoids. These findings suggest that rotator cuff muscle imbalance may not be the precipitating etiology for the posterior humeral subluxation and secondary posterior glenoid erosion characteristic of Walch type B glenoids.
肱骨后脱位的病因仍不清楚，有人假设水平肌肉失衡可能导致这种情况。本研究的目的是比较在关节炎性肩关节中，作为连续变量分析时，肩袖和三角肌前、后肌体积比与盂肱关节半脱位和肩胛盂形态之间的关系。
共纳入 333 例肩关节 CT 扫描（273 例关节炎性肩关节和 60 例健康对照组），并进行自动分段。对于每个肌肉，测量无肌内脂肪的肌纤维体积。计算肩胛下肌与冈下肌和小圆肌（AP 比）的体积比以及前三角肌和后三角肌（AP）的体积比。进行统计学分析，以确定这些比值与肩胛盂分型、肱骨头半脱位和/或肩胛盂类型之间是否存在相关性。
在关节炎组中，A型肩胛盂（1.09±0.22）与 B 型肩胛盂（1.03±0.16，P=0.09）、D 型肩胛盂（1.12±0.27，P=0.77）或 C 型肩胛盂（1.10±0.19，P＞0.999）的 AP 比值无统计学差异。AP 比值与肩胛盂分型（ρ=-0.0360，P=0.55）或肱骨头半脱位（ρ=0.076，P=0.21）无相关性。A型肩胛盂（0.48±0.15）的 AP 比值显著大于 B 型肩胛盂（0.35±0.16，P＜0.01）和 C 型肩胛盂（0.21±0.10，P＜0.01），但与 D 型肩胛盂（0.64±0.34，P＞0.999）无显著差异。当评估健康对照组和关节炎性肩关节时，AP 比值与肩胛盂分型（ρ=0.55，P＜0.01）和肱骨头半脱位（ρ=-0.61，P＜0.01）之间存在中度相关性。
这项体外研究支持使用软件对 4 个肩袖肌肉和三角肌进行完全自动的 3 维重建。与之前的二维 CT 扫描研究相比，我们的研究未发现关节炎性肩关节中前、后肌体积比与肩胛盂参数之间存在任何相关性。然而，一旦发生畸形，B 型和 C 型肩胛盂的观察到的 AP 比值较低。这些发现表明，肩袖肌肉失衡可能不是导致 B 型肩胛盂特征性的肱骨后脱位和继发性后肩胛盂侵蚀的诱发因素。
