The Effects of a Crosslinked, Modified Hyaluronic Acid (xCMHA-S) Gel on Equine Tendon Healing.

Objective: To assess the effects of a crosslinked, modified hyaluronic acid (xCMHA-S) gel on equine tendon healing using an in vivo surgical model.

Study Design: In vivo experimental study.

Animals: Adult horses (n = 5).

Methods: Full thickness bilateral forelimb window tenectomies were surgically created in both forelimb superficial digital flexor tendons and xCMHA-S gel was implanted intraoperatively into the right forelimb lesion of each horse whereas the left forelimb served as the untreated control. Healing was monitored by serial ultrasound examinations every 14 days over the course of the 84 day study. In addition, gross pathology, scanning electron microscopy for fiber diameter, and histological scoring were completed on tendon samples harvested after euthanasia at 84 days.

Results: Ultrasound assessment demonstrated a significant decrease in mean lesion size of treated (0%) compared to control (30%) tendons at 84 days. Mean (±SD) cumulative histologic tendon scores for control tendons (17.7 ± 2.7) were significantly higher than treated tendons (13.6 ± 1.9), indicating less advanced healing in the control group. Tendon cell density was increased and neovascularization, intensity of inflammation, and uniformity of fiber diameter were increased in control compared to treated tendons. There were no differences in fibroblast shape, levels of intralesional hemorrhage, linearity of collagen fibers, or collagen fiber diameter or distribution between treated and control tendons.

Conclusion: Tendons treated with xCMHA-S gel at the time of model induction had superior histologic healing scores and sonographically smaller lesions compared to controls, suggesting that xCMHA-S gel may aid the natural healing process.