The rotator cuff (RC) muscles are crucial in moving and stabilizing the glenohumeral joint, and tears can be functionally devastating. Chronic fatty and fibrotic muscle changes, which are non-responsive to surgical tendon repair, are a focus of contemporary research. The rabbit model recapitulates key biological features of human RC tears, but function and physiology are poorly characterized-limited force and stress data are inconsistent with literature norms in other mammalian species. Here, we present an improved method to assess the physiology of the rabbit SSP, and report values for healthy SSP architecture and physiology. Using female New Zealand White Rabbits (n=6) under 2% isofluorane anesthesia, the SSP was surgically isolated and maximum isometric force measured at 4-6 muscle lengths. Architectural analysis was performed, and maximum isometric stress was computed. Whole muscle length-tension curves were generated using architectural measurements to compare experimental physiology to theoretical predictions. Maximum isometric force (80.87± 5.58N) was dramatically greater than previous reports (11.06 and 16.1N, p<0.05). Architectural measurement of fiber length (34.25 ± 7.18mm), muscle mass (9.9 ± 0.93g), pennation angle (23.67 ± 8.32°), and PCSA (2.57 ± 0.20cm²) were consistent with prior literature. Isometric stress (30.5 ± 3.07N/cm²) was greater than previous reports of rabbit SSP (3.10 and 4.51 N/cm²), but similar to mammalian skeletal muscles (15.7-30.13 N/cm²). Previous studies underestimated peak force by ~90%, having profound implications for interpreting physiological changes as a function of disease state. Data presented here enable understanding the physiological implications of disease and repair in the RC of the rabbit.

中文翻译：

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兔体内Supraspinatus肌肉收缩力和结构

肩袖（RC）肌肉在移动和稳定盂肱关节方面至关重要，而眼泪可能会造成功能严重破坏。对外科肌腱修复无反应的慢性脂肪和纤维化肌肉变化是当代研究的重点。兔模型概述了人类RC眼泪的关键生物学特征，但功能和生理学的表征欠佳，受力有限，压力数据与其他哺乳动物物种的文献标准不一致。在这里，我们提出了一种改进的方法来评估兔SSP的生理学，并报告健康的SSP体系结构和生理学的价值。使用雌性新西兰白兔（n = 6）在2％异氟烷麻醉下，通过外科手术分离SSP，并在4-6个肌肉长度处测量最大等距力。进行了架构分析，并计算出最大等距应力。使用建筑测量产生全肌肉长度-张力曲线，以将实验生理与理论预测进行比较。最大等轴测力（80.87±5.58N）显着大于以前的报道（11.06和16.1N，p <0.05）。纤维长度（34.25±7.18mm），肌肉质量（9.9±0.93g），下垂角（23.67±8.32°）和PCSA（2.57±0.20cm）的建筑测量²）与现有文献一致。等轴测应力（30.5±3.07N / cm ²）大于兔子SSP的先前报道（3.10和4.51 N / cm ²），但与哺乳动物骨骼肌相似（15.7-30.13 N / cm ²）。先前的研究低估了峰值力约90％，对将生理变化解释为疾病状态具有深远的意义。此处提供的数据有助于了解兔子RC中疾病和修复的生理意义。