Returning to overuse activity following a supraspinatus and infraspinatus tear leads to joint damage in a rat model

• Published in: Journal of biomechanics Vol. 46; no. 11; pp. 1818 - 1824
• Main Authors: Reuther, Katherine E, Thomas, Stephen J, Evans, Elisabeth F, Tucker, Jennica J, Sarver, Joseph J, Ilkhani-Pour, Sarah, Gray, Chancellor F, Voleti, Pramod B, Glaser, David L, Soslowsky, Louis J
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 26-07-2013; Elsevier Limited
• Subjects: Animal model; Animals; Biological; Biomechanical Phenomena; Cartilage; Cartilage, Articular - physiopathology; Chondrogenesis - genetics; Chondrogenic phenotype; Cuffs; Cumulative Trauma Disorders - etiology; Cumulative Trauma Disorders - pathology; Cumulative Trauma Disorders - physiopathology; Damage; Disease Models, Animal; Elastic Modulus; Gene Expression; Histology; Humans; Male; Mechanical properties; Overuse injury; Patients; Physical Medicine and Rehabilitation; Rats; Rats, Sprague-Dawley; Rotator cuff; Rotator Cuff - pathology; Rotator Cuff - physiopathology; Rotator Cuff Injuries; Shoulder; Shoulder Joint - injuries; Shoulder Joint - pathology; Shoulder Joint - physiopathology; Shoulders; Sports injuries; Tearing; Tendons; Tendons - physiopathology; Animal model; Overuse injury; Chondrogenic phenotype; Rotator cuff
• DOI: 10.1016/j.jbiomech.2013.05.007
• EISSN: 1873-2380
• ISSN: 0021-9290

Abstract Large rotator cuff tears (supraspinatus and infraspinatus) are common in patients who perform overhead activities (laborers, athletes). In addition, following large cuff tears, these patients commonly attempt to return to pre-injury activity levels. However, there is a limited understanding of the damaging effects on the uninjured joint tissues when doing so. Therefore, the objective of this study was to investigate the effect of returning to overuse activity following a supraspinatus and infraspinatus tear on shoulder function and the structural and biological properties of the intact tendons and glenoid cartilage. Forty rats underwent 4 weeks of overuse followed by detachment of the supraspinatus and infraspinatus tendons and were then randomized into two groups: return to overuse or cage activity. Ambulatory measurements were performed over time and structural and biological properties of the adjacent tendons and cartilage were evaluated. Results demonstrated that animals returning to overuse activity did not have altered shoulder function but despite this, did have altered cartilage and tendon properties. These mechanical changes corresponded to altered transcriptional regulation of chondrogenic genes within cartilage and tendon. This study helps define the mechanical and biological mechanisms leading to joint damage and provides a framework for treating active cuff tear patients.