McKay Orthopaedic Research Laboratory, University of Pennsylvania, 3450 Hamilton Walk, 424 Stemmler Hall, Philadelphia, PA 19104-6081, USA.
Clin Orthop Relat Res. 2010 Jun;468(6):1485-92. doi: 10.1007/s11999-009-1206-y.
Chronic rotator cuff tears are often associated with pain or poor function. In a rat with only a detached supraspinatus tendon, the tendon heals spontaneously which is inconsistent with how tears are believed to heal in humans.
QUESTIONS/PURPOSES: We therefore asked whether a combined supraspinatus and infraspinatus detachment in the rat would fail to heal and result in a chronic injury in the supraspinatus tendon.
We acutely detached the supraspinatus and infraspinatus tendons in a rat model. At 4, 8, and 16 weeks post-detachment, biomechanical testing, collagen organization, and histological grading were evaluated for the detached supraspinatus and infraspinatus tendons and compared to controls.
In the detached supraspinatus tendon, area and percent relaxation were increased at all time points while the modulus and stiffness were similar to those of controls at 4 and 8 weeks. Collagen disorganization increased at late time points while cellularity increased and cells were more rounded in shape. In the detached infraspinatus tendon, area and percent relaxation were also increased at late time points. However, the modulus values initially decreased followed by an increase in both modulus and stiffness at 16 weeks compared to control. In the detached infraspinatus, we also observed a decrease in collagen organization at all time points and increased cellularity and a more rounded cell shape.
Due to the ongoing changes in mechanics, collagen organization and histology in the detached supraspinatus tendon compared to control animals at 16 weeks, this model may be useful for understanding the human chronic tendon tear.
This rat rotator cuff chronic model can be used to test hypotheses regarding injury and repair mechanisms that cannot be addressed in human patients or in cadaveric studies.
慢性肩袖撕裂常伴有疼痛或功能不良。在仅存在冈上肌腱分离的大鼠中，肌腱会自发愈合，这与人们认为的撕裂如何愈合不一致。
问题/目的：因此，我们想知道在大鼠中同时分离冈上肌和冈下肌肌腱是否会无法愈合，并导致冈上肌腱慢性损伤。
我们在大鼠模型中急性分离冈上肌和冈下肌肌腱。在分离后 4、8 和 16 周，评估了分离的冈上肌和冈下肌肌腱的生物力学测试、胶原组织和组织学分级，并与对照组进行了比较。
在分离的冈上肌腱中，所有时间点的面积和松弛百分比均增加，而在 4 周和 8 周时，其模量和刚度与对照组相似。胶原组织紊乱在晚期增加，而细胞增多，细胞呈圆形。在分离的冈下肌腱中，晚期面积和松弛百分比也增加。然而，与对照组相比，在 16 周时，模量值最初降低，随后模量和刚度均增加。在分离的冈下肌腱中，我们还观察到所有时间点胶原组织减少，细胞增多，细胞呈圆形。
由于在 16 周时分离的冈上肌腱与对照组动物相比，力学、胶原组织和组织学不断变化，因此该模型可能有助于理解人类慢性肌腱撕裂。
这种大鼠肩袖慢性模型可用于测试与损伤和修复机制相关的假设，这些假设在人类患者或尸体研究中无法解决。
