Veterinary Science & Technology

Carbomer Viscosupplementation in the Equine Middle Carpal Joint

Abstract

JM Rosser

Joint visco supplementation is widely used in the sport horse industry, commonly utilizing hyaluronan. Similar to hyaluronan, the carbomer molecule has bioadhesive and viscoelastic properties, and has been 15 studied for use in human medicine. Carbomers are generally inert biologically, non-irritating, and have been used in humans as injectable depots for time-release medications. Our objective was to describe the outcome of intra-articular viscosupplementation with carbomer in four horses. Four healthy adult mares participated in this study. Baseline lameness examinations, aseptic arthrocenteses and synovial fluid analyses were performed. Three mL of 3% carbomer was then 20 injected into each left middle carpal joint. Lameness evaluations were repeated daily for each horse for ten days post-injection or until the time of euthanasia. At euthanasia, synovial fluid analyses were repeated on the left middle carpal joint. Samples of synovium from the left middle carpal joints were submitted for histopathology. Articular cartilage of the third carpal bone including subchondral bone was submitted for histology and confocal microscopy. 25 Carbomer viscosupplementation of the middle carpal joint caused severe lameness in 3 /4 mares. The fourth mare developed moderate lameness after injection. Confocal microscopy was negative for cartilaginous defects. Histology of all treated samples revealed varying degrees of small cell inflammatory infiltrate into the subsynovia. With no abnormal findings in samples of cartilage or subchondral bone, lameness is attributable to 30 severe synovitis, which is consistent with histologic findings of synovium in all cases. The current formulation of carbomer is therefore not suitable for intra-articular viscosupplementation in horses.