Department of Orthopaedic Surgery, McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA 19104-6081, USA.
J Shoulder Elbow Surg. 2012 Jul;21(7):873-81. doi: 10.1016/j.jse.2011.04.036. Epub 2011 Aug 4.
Biceps tendon pathology is common with rotator cuff tears. The mechanisms for biceps changes, and therefore its optimal treatment, are unknown. Our objective was to determine the effect of rotator cuff tears on regional biceps tendon pathology. We hypothesized that histologic and compositional changes would appear before organizational changes, both would appear before mechanical changes, and changes would begin at the tendon's insertion site.
Detachment of supraspinatus and infraspinatus tendons or sham surgery was done in 65 Sprague-Dawley rats. Rats were euthanized at 1, 4, or 8 weeks for regional measurements of histologic, compositional, organizational (1, 4 and 8 weeks), or mechanical properties (4 and 8 weeks only).
One week after tendon detachments, decreased organization and more rounded cell shape were found in the intra-articular space of the biceps tendon. Aggrecan expression was increased along the entire length of the tendon, whereas all other compositional changes were only at the tendon's proximal insertion into bone. With time, this disorganization and more rounded cell shape extended the length of the tendon. Organizational and cell shape changes also preceded detrimental mechanical changes: decreased modulus in the intra-articular space was found after 8 weeks.
Results support a degenerative component to pathology in the biceps tendon. In addition, changes resembling a tendon exposed to compressive loading occurring first in the intra-articular space indicate that the biceps tendon plays an increased role as a load-bearing structure against the humeral head in the presence of rotator cuff tears.
二头肌肌腱病变在肩袖撕裂中很常见。二头肌变化的机制及其最佳治疗方法尚不清楚。我们的目的是确定肩袖撕裂对区域性二头肌肌腱病变的影响。我们假设组织学和成分变化将先于组织结构变化出现，两者都将先于机械变化出现，并且变化将从肌腱的插入部位开始。
在 65 只斯普拉格-道利大鼠中进行了冈上肌和冈下肌肌腱的分离或假手术。在 1、4 或 8 周时处死大鼠，进行区域性组织学、成分、组织学（1、4 和 8 周）或力学特性（仅 4 和 8 周）测量。
在肌腱分离后 1 周，发现二头肌肌腱关节内空间的组织排列减少，细胞形状变圆。聚集蛋白的表达沿整个肌腱长度增加，而所有其他成分变化仅在肌腱近端插入骨处。随着时间的推移，这种无序和更圆的细胞形状使肌腱的长度延长。组织结构和细胞形状的变化也先于有害的机械变化：在 8 周后发现关节内空间的模量降低。
结果支持二头肌肌腱病变具有退行性成分。此外，类似于暴露于压缩载荷下的肌腱的变化首先发生在关节内空间，表明在肩袖撕裂存在的情况下，二头肌肌腱作为抵抗肱骨头的承重结构发挥更大的作用。
