Mitterer Marian, Matis Nicholas, Steiner Gernot, Vasvary Imre, Ortmaier Reinhold
Department of Orthopaedics and Traumatology, Paracelsus Medical University Salzburg, 5020 Salzburg, Austria.
Department for Radiology, Private Hospital Wehrle-Diakonissen, 5020 Salzburg, Austria.
BMC Musculoskelet Disord. 2021 Mar 15;22(1):279. doi: 10.1186/s12891-021-04146-3.
The transverse force couple (TFC) of the rotator cuff (subscapularis vs. infraspinatus and teres minor muscle) is an important dynamic stabilizer of the shoulder joint in the anterior-posterior direction. In patients with posterior static subluxation of the humeral head (PSSH), decentration of the humeral head posteriorly occurs, which is associated with premature arthritis. We hypothesize that not only pathologic glenoid retroversion but also chronic muscle volume imbalance in the transverse force couple leads to PSSH.
A retrospective analysis of the TFC muscle volumes of 9 patients with symptomatic, atraumatic PSSH, within 8 were treated with glenoid correction osteotomy, was conducted. The imaging data (CT) of 9 patients/10 shoulders of the full scapula and shoulder were analyzed, and the muscle volumes of the subscapularis (SSC), infraspinatus (ISP) and teres minor muscles (TMM) were measured by manually marking the muscle contours on transverse slices and calculating the volume from software. Furthermore, the glenoid retroversion and glenohumeral distance were measured.
The mean glenoid retroversion was - 16° (- 7° to - 31°). The observed mean glenohumeral distance was 4.0 mm (0 to 6.8 mm). Our study population showed a significant muscle volume imbalance between the subscapularis muscle and the infraspinatus and teres minor muscles (192 vs. 170 ml; p = 0.005). There was no significant correlation between the subscapularis muscle volume and the glenohumeral distance (r = 0.068), (p = 0.872).
The muscle volume of the SSC in patients with PSSH was significantly higher than the muscle volume of the posterior force couple (ISP and TMM). This novel finding, albeit in a small series of patients, may support the theory that transverse force couple imbalance is associated with PSSH.
Level 4 - Case series with no comparison group.
肩袖的横向力偶（肩胛下肌与冈下肌和小圆肌）是肩关节在前后方向上重要的动态稳定器。在肱骨头后静态半脱位（PSSH）患者中，肱骨头会向后移位，这与过早出现关节炎有关。我们推测，不仅病理性的肩胛盂后倾，而且横向力偶中的慢性肌肉体积失衡都会导致PSSH。
对9例有症状的非创伤性PSSH患者的横向力偶肌肉体积进行回顾性分析，其中8例接受了肩胛盂矫正截骨术。分析了9例患者/10个肩部全肩胛骨和肩部的影像数据（CT），通过在横断面上手动标记肌肉轮廓并利用软件计算体积来测量肩胛下肌（SSC）、冈下肌（ISP）和小圆肌（TMM）的肌肉体积。此外，还测量了肩胛盂后倾和肱盂距离。
平均肩胛盂后倾为-16°（-7°至-31°）。观察到的平均肱盂距离为4.0毫米（0至6.8毫米）。我们的研究人群显示肩胛下肌与冈下肌和小圆肌之间存在明显的肌肉体积失衡（192对170毫升；p = 0.005）。肩胛下肌体积与肱盂距离之间无显著相关性（r = 0.068），（p = 0.872）。
PSSH患者的SSC肌肉体积明显高于后向力偶（ISP和TMM）的肌肉体积。这一新颖的发现，尽管是在一小部分患者中得出的，但可能支持横向力偶失衡与PSSH相关的理论。
4级——无比较组的病例系列。
