Engelhardt Christoph, Malfroy Camine Valérie, Ingram David, Müllhaupt Philippe, Farron Alain, Pioletti Dominique, Terrier Alexandre
a Laboratory of Biomechanical Orthopaedics , EPFL , Lausanne , Switzerland.
Comput Methods Biomech Biomed Engin. 2015;18(12):1272-9. doi: 10.1080/10255842.2014.899587. Epub 2014 Apr 4.
The estimation of muscle forces in musculoskeletal shoulder models is still controversial. Two different methods are widely used to solve the indeterminacy of the system: electromyography (EMG)-based methods and stress-based methods. The goal of this work was to evaluate the influence of these two methods on the prediction of muscle forces, glenohumeral load and joint stability after total shoulder arthroplasty. An EMG-based and a stress-based method were implemented into the same musculoskeletal shoulder model. The model replicated the glenohumeral joint after total shoulder arthroplasty. It contained the scapula, the humerus, the joint prosthesis, the rotator cuff muscles supraspinatus, subscapularis and infraspinatus and the middle, anterior and posterior deltoid muscles. A movement of abduction was simulated in the plane of the scapula. The EMG-based method replicated muscular activity of experimentally measured EMG. The stress-based method minimised a cost function based on muscle stresses. We compared muscle forces, joint reaction force, articular contact pressure and translation of the humeral head. The stress-based method predicted a lower force of the rotator cuff muscles. This was partly counter-balanced by a higher force of the middle part of the deltoid muscle. As a consequence, the stress-based method predicted a lower joint load (16% reduced) and a higher superior-inferior translation of the humeral head (increased by 1.2 mm). The EMG-based method has the advantage of replicating the observed cocontraction of stabilising muscles of the rotator cuff. This method is, however, limited to available EMG measurements. The stress-based method has thus an advantage of flexibility, but may overestimate glenohumeral subluxation.
在肌肉骨骼肩部模型中，肌肉力量的估计仍存在争议。有两种不同的方法被广泛用于解决该系统的不确定性：基于肌电图（EMG）的方法和基于应力的方法。这项工作的目的是评估这两种方法对全肩关节置换术后肌肉力量预测、盂肱关节负荷和关节稳定性的影响。将基于EMG的方法和基于应力的方法应用于同一个肌肉骨骼肩部模型。该模型复制了全肩关节置换术后的盂肱关节。它包含肩胛骨、肱骨、关节假体、肩袖肌肉（冈上肌、肩胛下肌和冈下肌）以及三角肌的中部、前部和后部。在肩胛骨平面模拟外展运动。基于EMG的方法复制了实验测量的EMG的肌肉活动。基于应力的方法使基于肌肉应力的成本函数最小化。我们比较了肌肉力量、关节反应力、关节接触压力和肱骨头的平移。基于应力的方法预测肩袖肌肉的力量较低。这在一定程度上被三角肌中部较高的力量所抵消。因此，基于应力的方法预测关节负荷较低（降低了16%），肱骨头的上下平移较高（增加了1.2毫米）。基于EMG的方法具有复制观察到的肩袖稳定肌肉共同收缩的优点。然而，这种方法仅限于可用的EMG测量。基于应力的方法因此具有灵活性的优点，但可能高估盂肱关节半脱位。
