Terrier A, Larrea X, Malfroy Camine V, Pioletti D P, Farron A
Laboratory of Biomechanical Orthopedics, Ecole Polytechnique Fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland.
Clin Biomech (Bristol). 2013 Feb;28(2):146-50. doi: 10.1016/j.clinbiomech.2012.11.010. Epub 2013 Jan 18.
The rotator cuff muscles are the main stabilizer of the glenohumeral joint. After total shoulder arthroplasty using anterior approaches, a dysfunction of the subscapularis muscle has been reported. In the present paper we tested the hypothesis that a deficient subscapularis following total shoulder arthroplasty can induce joint instability.
To test this hypothesis we have developed an EMG-driven musculoskeletal model of the glenohumeral joint. The model was based on an algorithm that minimizes the difference between measured and predicted muscular activities, while satisfying the mechanical equilibrium of the glenohumeral joint. A movement of abduction in the scapular plane was simulated. We compared a normal and deficient subscapularis. Muscle forces, joint force, contact pattern and humeral head translation were evaluated.
To satisfy the mechanical equilibrium, a deficient subscapularis induced a decrease of the force of the infraspinatus muscle. This force decrease was balanced by an increase of the supraspinatus and middle deltoid. As a consequence, the deficient subscapularis induced an upward migration of the humeral head, an eccentric contact pattern and higher stress within the cement.
These results confirm the importance of the suscapularis for the long-term stability of total shoulder arthroplasty.
肩袖肌群是盂肱关节的主要稳定器。在采用前入路进行全肩关节置换术后，已有肩胛下肌功能障碍的报道。在本文中，我们验证了全肩关节置换术后肩胛下肌功能不足会导致关节不稳定这一假设。
为验证这一假设，我们构建了一个由肌电图驱动的盂肱关节肌肉骨骼模型。该模型基于一种算法，在满足盂肱关节力学平衡的同时，使测量到的和预测的肌肉活动之间的差异最小化。模拟了肩胛平面内的外展运动。我们比较了正常和功能不足的肩胛下肌。评估了肌肉力量、关节力、接触模式和肱骨头移位情况。
为满足力学平衡，功能不足的肩胛下肌导致冈下肌力量下降。这种力量下降通过冈上肌和三角肌中部力量的增加得以平衡。结果，功能不足的肩胛下肌导致肱骨头向上移位、偏心接触模式以及骨水泥内更高的应力。
这些结果证实了肩胛下肌对全肩关节置换术长期稳定性的重要性。
