Chronic massive rotator cuff tear in rats: in vivo evaluation of muscle force and three-dimensional histologic analysis

• Published in: Journal of shoulder and elbow surgery Vol. 23; no. 12; pp. 1822 - 1830
• Main Authors: Ditsios, Konstantinos, MD, PhD, Boutsiadis, Achilleas, MD, Kapoukranidou, Dorothea, MD, PhD, Chatzisotiriou, Athanasios, MD, PhD, Kalpidis, Ioannis, MD, PhD, Albani, Maria, MD, PhD, Christodoulou, Anastasios, MD, PhD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2014
• Subjects: 3-D atrophy; Animals; Chronic Disease; isometric tension recordings; Male; Muscle Strength; Muscle, Skeletal - pathology; Muscle, Skeletal - physiopathology; Muscular Atrophy - pathology; Muscular Atrophy - physiopathology; Orthopedics; Rat model; Rats; Rats, Sprague-Dawley; Rotator Cuff - pathology; Rotator Cuff - physiopathology; Rotator Cuff Injuries; Rupture; Tendon Injuries - pathology; Tendon Injuries - physiopathology; Tendons - pathology; Tendons - physiopathology; Rat model; Basic Science; Animal Model; Biomechanics and Histology; isometric tension recordings; 3-D atrophy
• ISSN: 1058-2746; 1532-6500
• DOI: 10.1016/j.jse.2014.04.016

Background Massive rotator cuff tear repair is frequently complicated by unsatisfactory clinical results due to possible tendon retraction, muscle atrophy, and fatty degeneration. The objective of this study was the development of a chronic massive tear in a rat model and the evaluation of the muscle force in vivo and of the histologic changes in a 3- dimensional manner. Methods To simulate massive rotator cuff tears, both the supraspinatus (SS) and the infraspinatus (IS) tendons were surgically detached from the right humerus of 15 male adult Sprague-Dawley rats. Twelve weeks postoperatively, all animals underwent isometric tension recordings of both the SS and IS muscles. Histologic analysis and image deconvolution processing were performed to estimate the presence and the distribution of atrophy in 3 dimensions. Results An overall 30% and 35% reduction in muscle force of the SS and IS muscles, respectively, was observed compared with the left uninjured shoulder ( P  < .005). Histologic analysis revealed that the degeneration and the fatty infiltration were more evident near the tendon and at the dorsal side in both muscle groups. Conclusions These results show that functional impairment of SS and IS muscles after chronic massive tendon tears could be attributed to the decrease in muscle force production during their repair on the greater tuberosity and, second, to the comparatively greater degeneration of their dorsal part.