ACUTE EFFECTS OF PERINEURAL ADMINISTRATION OF SODIUM HYALURONATE ON PALMAR DIGITAL NEURECTOMY SITES IN HORSES

Biaxial palmar digital neurectomy of all limbs was performed on 6 mixe d-breed castrated adult male horses, using a standard guillotine metho d. Using a Teflon catheter, 20 mg (2 ml) of sodium hyaluronate (group 1), 2 ml of phosphate-buffered saline solution (group 2), or catheter placement with no infusion (group 3) was applied to 4 (group 1) or 2 ( groups 2 and 3) of 8 incisions/horse. Treatments were administered aft er closure of the neurectomy incision, and the catheter was removed. H orses were evaluated daily for 1 week, then weekly over a 9-week perio d for evidence of lameness, swelling, and ultrasonographic changes. On week 9, horses were euthanatized and neurectomy sites were removed en bloc for histologic evaluation of axonal regrowth, inflammation, and fibrosis. Neither lameness nor sign of painful neuroma was observed cl inically in any of the horses. Neurectomy eliminated cutaneous heel se nsation in all limbs for the duration of the study. Swelling was evide nt at all neurectomy sites. There were no significant differences betw een treatment sites for measurement of pastern circumference or ultras onographic evaluation of incisional swelling. Foci of ultrasonographic hyperechogenicity increased over time, but there was no significant d ifference in hyperechogenicity between treatment groups. Histologic ev idence of neuroma formation was observed at all sites. Morphometric as sessment of neuroma cross-sectional areas revealed no significant diff erence between the groups, as did subjective histologic assessment of neuroma density and fibrous tissue content. We conclude that there are no clinical, ultrasonographic, or histologic effects on neuroma forma tion and fibrosis at sites of palmar digital neurectomy associated wit h a single perineural administration of sodium hyaluronate or phosphat e-buffered saline solution.