Dynamic and Static Analysis of Rotator CUFF (Supraspinatus Tendon) with Tensile Test

目的：冈上肌腱的法氏侧(B-S)和关节侧(J-S)层可能以不同的机制发生撕裂。本研究从肩袖撕裂的病因出发，试图阐明肩袖撕裂的组织学特征和生物力学特性的差异。材料和方法：从28-79岁的新鲜身体的双侧肩部切取50条冈上肌腱。对10例冈上肌腱进行了冠状面和肌腱交界处、关键部近端、远端及附着点的4个交叉面的组织学切片。在生物力学研究中，将40根冈上肌腱水平分为等厚的B-S层和J-S层。对各层进行准静态拉伸实验，测量肌腱、肌腱及附着部的伸长率。结果：B-S层冈上肌腱纤维较J-S层厚。J-S层中的纤维向插入处逐渐变细。在拉伸试验中，B-S层的破坏应力大于J-S层，而前者的弹性模量较低。B-S层的肌腱部分延伸率最大，J-S层的延伸率最小。“粗大断裂”发生在B-S肌腱近端和J-S肌腱附着点附近。“锥状破裂”发生在附着部附近，反映了附着部的退行性改变。

Objective : The bursal-side (B-S) and the joint-side (J-S) layers of the supraspinatus tendon may be torn in the different mechanism. In this study, we attempted to clarify the difference of the histological characteristic and the biomechanical property between both layers with reference to the etiology of the rotator cuff tear.Materials and Methods : 50 supraspinatus tendons were resected from bilateral shoulders of fresh cadavers (28-79 yrs.). Histological sections from 10 supraspinatus tendons were made in the coronal and four cross planes at the musculotendinous junction, proximal and distal points of the critical portion and the insertion. In the biomechanical study, 40 supraspinatus tendons were divided horizontally into the B-S and J-S layers of equal thickness. Quasistatic tensile test was performed foe each layer and the elongation rates in the musculotendinous, tendinous and insertional portions were measured.Results : The tendon fibers of the supraspinatus were thicker in the B-S layer than in the J-S layer. The fibers in the J-S layer tapered toward the insertion. In the tensile test, the destroying stress to the B-S layer was greater than that to the J-S layer while the elastic modulus was lower in the former. The tendinous portion had the largest elongation rate in the B-S layer, while the J-S layer elongated evenly. 'Gross rupture' occurred in the proximal portion of the tendon in the B-S layer and near the insertion in the J-S layer. 'Concealed rupture' occurred near the insertion and reflected the degenerative changes of the enthesis.