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

目的：冈上肌腱囊侧（B-S）层和关节侧（J-S）层的撕裂机制不同。在这项研究中，我们试图澄清两层的组织学特征和生物力学性能的差异，参考肩袖撕裂的病因。材料和方法：50冈上肌腱从新鲜尸体（28-79岁）的双侧肩部切除。从10冈上肌腱的冠状面和四个交叉平面的肌腱交界处，近端和远端的关键部分和插入点的组织切片。在生物力学研究中，将40条冈上肌腱水平分为等厚的B-S层和J-S层。结果：冈上肌腱B-S层的肌腱纤维较J-S层的粗，而J-S层的肌腱纤维较J-S层的粗。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，而弹性模量小于J-S层。B-S层中腱性部分的伸长率最大，而J-S层的伸长较均匀。B-S层肌腱近端部分和J-S层插入处附近发生“严重断裂”。“隐性断裂”发生在插入点附近，反映了附着点的退行性变化。

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.