Effects of Tendon Splitting on Experimentally-Induced Acute Equine Tendinitis

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Abstract
The objective of this study was to compare the early phases of healing between surgically split and unsplit (control) tendons in a superficial digital flexor tendinitis model. Tendinitis was induced in both forelimbs of six horses by injection with collagenase. One tendon from each horse was randomly chosen to undergo tendon splitting. In six horses, the tendons were evaluated by ultrasonography before (week 0) and after (week 1) the onset of tendinitis and at weeks two, three, and four following tendon splitting. Three horses were euthanatized at the end of week four. Three horses were maintained for an additional month and evaluated at week eight before euthanasia. Following euthanasia, microangiographic and histologic evaluations were performed. Ultrasonographic evaluation revealed a significant (p 0.05) between groups at all periods after surgery. There was a more mature vascular pattern and greater peritendinous vascular response in the split tendons compared to control tendons. Histological examination under plain and polarized light revealed more normal collagen orientation and wave formation in the repair tissue in the split tendons at weeks four and eight. The fibroblast nuclei density was significantly (p <0.05) lower in the split tendons at week eight. These findings suggest that during the time period of this study, tendon splitting results in a more rapid decrease in lesion size and superior repair tissue organization when compared to controls. In a collagenase-induced tendinitis model, tendon splitting was shown to result in a greater reduction in tendon lesion size and superior repair tissue organization when compared to control tendons.