Genter Jeremy, Croci Eleonora, Oberreiter Birgit, Eckers Franziska, Bühler Dominik, Gascho Dominic, Müller Andreas M, Mündermann Annegret, Baumgartner Daniel
IMES Institute of Mechanical Systems, Zurich University of Applied Sciences ZHAW, Winterthur, Switzerland; Department of Biomedical Engineering, University of Basel, Basel, Switzerland; Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland.
Department of Biomedical Engineering, University of Basel, Basel, Switzerland; Department of Orthopaedics and Traumatology, University Hospital Basel, Basel, Switzerland.
J Biomech. 2024 Mar;166:112055. doi: 10.1016/j.jbiomech.2024.112055. Epub 2024 Mar 20.
Glenohumeral biomechanics after rotator cuff (RC) tears have not been fully elucidated. This study aimed to investigate the muscle compensatory mechanism in weight-bearing shoulders with RC tears and asses the induced pathomechanics (i.e., glenohumeral translation, joint instability, center of force (CoF), joint reaction force). An experimental, glenohumeral simulator with muscle-mimicking cable system was used to simulate 30° scaption motion. Eight fresh-frozen shoulders were prepared and mounted in the simulator. Specimen-specific scapular anthropometry was used to test six RC tear types, with intact RC serving as the control, and three weight-bearing loads, with the non-weight-bearing condition serving as the control. Glenohumeral translation was calculated using instantaneous helical axis. CoF, muscle forces, and joint reaction forces were measured using force sensors integrated into the simulator. Linear mixed effects models (RC tear type and weight-bearing) with random effects (specimen and sex) were used to assess differences in glenohumeral biomechanics. RC tears did not change the glenohumeral translation (p > 0.05) but shifted the CoF superiorly (p ≤ 0.005). Glenohumeral translation and joint reaction forces increased with increasing weight bearing (p < 0.001). RC and deltoid muscle forces increased with the presence of RC tears (p ≤ 0.046) and increased weight bearing (p ≤ 0.042). The synergistic muscles compensated for the torn RC tendons, and the glenohumeral translation remained comparable to that for the intact RC tendons. However, in RC tears, the more superior CoF was close to where glenoid erosion occurs in RC tear patients with secondary osteoarthritis. These findings underscore the importance of early detection and precise management of RC tears.
肩袖（RC）撕裂后的盂肱关节生物力学尚未完全阐明。本研究旨在调查负重状态下肩袖撕裂肩部的肌肉代偿机制，并评估由此引发的病理力学变化（即盂肱关节平移、关节不稳定、力中心（CoF）、关节反应力）。使用带有肌肉模拟缆线系统的实验性盂肱关节模拟器来模拟30° 肩外展运动。制备了八个新鲜冷冻肩关节并安装在模拟器中。采用特定标本的肩胛骨人体测量法来测试六种肩袖撕裂类型，以完整肩袖作为对照，以及三种负重负荷，以非负重状态作为对照。使用瞬时螺旋轴计算盂肱关节平移。使用集成在模拟器中的力传感器测量力中心、肌肉力量和关节反应力。采用具有随机效应（标本和性别）的线性混合效应模型（肩袖撕裂类型和负重）来评估盂肱关节生物力学的差异。肩袖撕裂并未改变盂肱关节平移（p > 0.05），但使力中心向上移位（p ≤ 0.005）。盂肱关节平移和关节反应力随负重增加而增加（p < 0.001）。肩袖和三角肌力量随肩袖撕裂的出现而增加（p ≤ 0.046），并随负重增加而增加（p ≤ 0.042）。协同肌肉代偿了撕裂的肩袖肌腱，盂肱关节平移与完整肩袖肌腱时相当。然而，在肩袖撕裂时，更高的力中心接近继发骨关节炎的肩袖撕裂患者出现盂肱关节侵蚀的部位。这些发现强调了早期发现和精确处理肩袖撕裂的重要性。
