The Effects of Overuse Combined With Intrinsic or Extrinsic Alterations in an Animal Model of Rotator Cuff Tendinosis

Abstract

An in vivo animal model was used to evaluate overuse and overuse plus intrinsic tendon injury or extrinsic tendon compression in the development of rotator cuff injury. Forty-four male Sprague-Dawley rats were divided into groups of 22. Each left shoulder received an intrinsic or extrinsic injury plus overuse (treadmill running), and each right shoulder received only overuse. Eleven rats from each group were sacrificed at 4 and 8 weeks. Supraspinatus tendons were evaluated histologically or geometrically and biomechanically. Ten rats constituted a cage-activity control group. Both supraspinatus tendons of the experimental groups had increases in cellularity and collagen disorganization and changes in cell shape compared with control tendons. Tendons with injury plus overuse exhibited a worse histologic grade than those with overuse alone. The cross-sectional area of both supraspinatus tendons of the experimental rats was significantly more than in control tendons. The area of the injury plus overuse tendons was increased on average compared with overuse-alone tendons. Biomechanically, the tissue moduli of overuse/intrinsic injury tendons at 4 weeks and those of the overuse/extrinsic injury tendons at 8 weeks were significantly lower than in control tendons. Tissue moduli of the overuse/injury tendons were significantly lower than in the overuse-alone tendons at 8 weeks. This study demonstrated that damage to the supraspinatus tendon can be caused by overuse and intrinsic injury, overuse and extrinsic compression, and overuse alone.

Towards development of a nonhuman primate model of carpal tunnel syndrome: Performance of a voluntary, repetitive pinching task induces median mononeuropathy in Macaca fascicularis

“…22,24,25,39,48 though other patterns are used as well. 49,50 In a rat model of rotator cuff tendinitis, the exposure (1 h/day, 5 day/week) was based on equating the number of strides per day for the subjects to ''the number of strokes an elite swimmer may take during a typical training protocol.'' 49 In the present model, exposure was modeled on the typical 40-h work week.…”

“…49,50 In a rat model of rotator cuff tendinitis, the exposure (1 h/day, 5 day/week) was based on equating the number of strides per day for the subjects to ''the number of strokes an elite swimmer may take during a typical training protocol.'' 49 In the present model, exposure was modeled on the typical 40-h work week. The subjects were free to execute as many trials as possible in that time (up to 6 rep/min within the 8 h day).…”

Work-Related Musculoskeletal Disorders of the Hand and Wrist: Epidemiology, Pathophysiology, and Sensorimotor Changes

“…Tendon necrosis and matrix disorganization are found only in studies utilizing intensive repetitive kicking or intensive running combined with tendon compression. 10,31,101,102 Inflamma- • See Table 5 tory changes are more prevalent than degenerative changes in animal models of tendinopathies and suggest that inflammatory/proliferative changes appear early, before overt signs of tissue injury. 7,10,12,77,102 Discrete signs of injury may precede inflammation in tendons or their sheaths.…”

Nicotine Delays Tendon-to-Bone Healing in a Rat Shoulder Model

“…who were blinded with regard to specimen group. Grading was performed with use of printed standards representing high (4), intermediate (3 and 2), low (1), and undetectable (0) levels 19,25,27 .…”