Evidence of tendon microtears due to cyclical loading in an in vivo tendinopathy model.
Nakama-LH; King-KB; Abrahamsson-S; Rempel-DM
J Orthop Res 2005 Sep; 23(5):1199-1205
Tendon injuries at the epicondyle can occur in athletes and workers whose job functions involve repetitive, high force hand activities, but the early pathophysiologic changes of tendon are not well known. The purpose of this study was to evaluate early tendon structural changes, specifically the formation of microtears, caused by cyclical loading. The Flexor Digitorum Profundus (FDP) muscle of nine New Zealand White rabbits was stimulated to contract repetitively for 80 h of cumulative loading over 14 weeks. The contralateral limb served as a control. The tendon at the medial epicondyle insertion site was harvested, sectioned, and stained. Microtears were quantified, using image analysis software, in four regions of the tendon, two regions along the enthesis and two distal to the enthesis. The tear density (loaded: 1329+/-546 tears/mm(2); unloaded: 932+/-474 tears/mm(2)) and mean tear size (loaded: 18.3+/-6.1 microm(2); unloaded: 14.0+/-4.8 microm(2)) were significantly greater in the loaded limb (p<0.0001) across all regions compared to the unloaded contralateral limb. These early microstructural changes in a repetitively loaded tendon may initiate a degenerative process that leads to tendinosis.
In-vivo-studies; Models; Injuries; Hand-injuries; Workers; Laboratory-animals; Animals; Animal-studies; Muscles; Repetitive-work; Cumulative-trauma-disorders; Cumulative-trauma
University of California, 1301 South 46th Street. Building 163, Richmond, CA 94804
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Journal of Orthopaedic Research
University of California - San Francisco