Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technical University of Munich, Connollystr. 32, 80805, Munich, Germany.
Arch Orthop Trauma Surg. 2011 Mar;131(3):429-35. doi: 10.1007/s00402-010-1246-5. Epub 2010 Dec 29.
The aim of the study was to develop a standardized rat model for chronic rotator cuff tears. Therefore, a time point of degenerative changes that shows comparable histological changes to the chronic tendon tears in humans had to be determined. The rat shoulder has already been described as a standardized model for investigation of the healing behavior in acute supraspinatus lesions. Little data exist about the possibility of generating a chronic rotator cuff lesion.
We performed a complete detachment of the supraspinatus tendon in 45 Sprague-Dawley rats. After an interval of 3, 6 and 9 weeks (15 rats in each group), the macroscopic and histological changes were analyzed. The histological investigation included atrophy and fatty muscle degeneration, tendon degeneration and the grade of inflammatory changes. For evaluation of tendon degeneration, a modified MOVIN-Score was used. The contralateral shoulder provided as control group.
Macroscopically the defect showed an increasing coverage with scar tissue over time with a complete closure in 73% after 9 weeks. The 3 week group showed the highest rate of persisting defects (80%). The atrophy of the supraspinatus muscle decreased from initial slight atrophy to a nearly normal muscle status in the 9 week group. Fatty infiltration was found in three animals per group regardless of the time interval after detachment. Tendon degeneration (modified MOVIN-Score) showed no significant difference between 3 and 6 weeks (p = 0.93) whereas after 9 weeks a significant increased degeneration was found (p < 0.01). In the early phase (3 and 6 weeks), inflammatory cells could be detected more frequently.
The results show that a chronic tear of the human rotator cuff can be imitated in the rat model with some exclusion. The rapid self-healing response in the rat and the fatty infiltration of the human muscle are the main differences. However, tendon degeneration, inflammation and muscle atrophy combined with a persisting defect at 3 weeks after detachment are comparable to the chronic tendon tears in humans. This model can serve as a basis for further research in the field of rotator cuff repair for chronic lesions.
本研究旨在建立一种稳定的慢性肩袖撕裂大鼠模型。因此，需要确定一个退行性变化的时间点，该时间点显示出与人慢性肌腱撕裂相当的组织学变化。大鼠肩部已被描述为研究急性冈上肌腱损伤愈合行为的标准模型。关于产生慢性肩袖损伤的可能性的数据很少。
我们在 45 只 Sprague-Dawley 大鼠中完全切断冈上肌腱。在 3、6 和 9 周后（每组 15 只），分析大体和组织学变化。组织学研究包括萎缩和脂肪肌肉变性、肌腱变性和炎症变化程度。为了评估肌腱变性，使用改良的 MOVIN 评分。对侧肩部作为对照组。
大体上，随着时间的推移，随着瘢痕组织的覆盖，缺损逐渐增大，9 周后有 73%完全闭合。3 周组的持续缺损率最高（80%）。冈上肌的萎缩从最初的轻度萎缩到 9 周组的接近正常肌肉状态逐渐减少。无论分离后时间间隔如何，每组均有 3 只动物出现脂肪浸润。肌腱变性（改良 MOVIN 评分）在 3 周和 6 周之间无显著差异（p=0.93），但 9 周后发现变性显著增加（p<0.01）。在早期（3 周和 6 周），可以更频繁地检测到炎症细胞。
结果表明，大鼠模型可以模拟人类肩袖的慢性撕裂，但存在一些差异。大鼠的快速自我修复反应和人类肌肉的脂肪浸润是主要的差异。然而，肌腱变性、炎症和肌肉萎缩以及分离后 3 周时持续存在的缺损与人类慢性肌腱撕裂相当。该模型可作为慢性肩袖损伤修复领域进一步研究的基础。
