Abstract
Few studies discuss kinetic changes in tendinopathy models. We propose a customized corridor to evaluate dynamic weight bearing (DWB) and shearing forces. Sixty rats were randomly given ultrasound-assisted collagenase injections (Collagenase rats) or needle punctures (Control rats) in their left Achilles tendons, and then evaluated 1, 4, and 8 weeks later. The Collagenase rats always had significantly (p < 0.001) higher histopathological and ultrasound feature scores than did the Controls, significantly lower DWB values in the injured than in the right hindlimbs, and compensatorily higher (p < 0.05) DWB values in the contralateral than in the left forelimbs. The injured hindlimbs had lower outward shearing force 1 and 4 weeks later, and higher (p < 0.05) push-off shearing force 8 weeks later, than did the contralateral hindlimbs. Injured Control rat hindlimbs had lower DWB values than did the contralateral only at week 1. The Collagenase rats had only lower static weight bearing ratios (SWBRs) values than did the Controls at week 1 (p < 0.05). Our customized corridor showed changes in DWB compatible with histopathological and ultrasound feature changes in the rat tendinopathy model. The hindlimb SWBRs did not correspond with any tendinopathic changes.
Highlights
Tendinopathy is a chronic painful tendon disorder that is common in athletes and the sedentary[1]
We propose a customized corridor composed of a chain of load cells and one digital camera to evaluate the kinetic parameters (dynamic weight bearing (DWB) force and shearing force) during a gait analysis
We found that the ultrasound-assisted collagenase injection into rat Achilles tendons is valid, and that the Collagenase-group rats had correspondingly higher histopathological and ultrasound feature scores, and significantly lower DWB scores than did the Control-group rats
Summary
Tendinopathy is a chronic painful tendon disorder that is common in athletes and the sedentary[1]. Intratendinous collagenase injection is a common induction method that yields consistent tendon damage compared with mechanical-overload models. It is less labor-intensive and less expensive to develop[1, 2]. Ultrasound is a real-time noninvasive examination with a growing number of applications for monitoring and diagnosing tendinopathy. Few studies report the dynamic changes in ultrasound features after a collagenase injection in a rat tendinopathy model. Fu et al.[13] in 2009 reported that motion analysis can be used to measure the painful responses associated with collagenase-induced tendinopathy rat models. Our first hypothesis was that collagenase injected into a rat’s Achilles tendon would induce histopathological changes, ultrasound features, and DWB changes that approximate human tendinopathy. Because of the pain, the collagenase-treated hindlimb would present less DWB than would the contralateral hindlimb, and the contralateral forelimb would present compensatorily more DWB than would the right forelimb
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