Fusion of the distal intertarsal and tarsometatarsal joints in the horse using intraarticular sodium monoiodoacetate.

This research study explores the use of sodium monoiodoacetate (MIA) injections for inducing joint fusion in horses, presenting a potential treatment for lower leg osteoarthritis. The results reveal that this non-invasive and affordable treatment method leads to joint fusion within six months, with minimal clinical side effects during exercise periods.

Research Methodology

• Six healthy horses participated in the study, receiving three MIA injections in the distal intertarsal (DIT) and tarsometatarsal (TMT) joints of one hind leg.
• These injections took place at three-week intervals. Any resulting pain was managed through the application of phenylbutazone for five days after each treatment.
• Starting one week following the first injection, the horses engaged in a gradually escalating exercise program. This comprised walking and trotting exercises and lasted for 24 weeks.

Findings

• Over time, the treated joints displayed increasing levels of radiographic proof of degenerative joint disease. However, symptoms were mild or non-existent during exercise periods.
• All of the joints that were treated demonstrated radiographic and histological evidence of fusion 24 weeks after the first injection.
• Radiographic fusion encompassed between 54.49% to 88.64% of the joint space, with most of the space appearing radiographically fused being stuffed predominantly with woven and lamellar bone.
• Transition areas between fused and non-fused sections often contained fibrocartilage and fibrous tissue.
• The articular cartilage in the non-fused areas was found to be thin, fibrillated, and contained fewer cells. Its proteoglycan content—which is crucial to cartilage firmness and resistance—was also found to be reduced.
• The existing joint space was filled with fibrin and necrotic, acellular chondroid matrix, indicating a substantial tissue change.

Conclusion

Based on their findings, the researchers concluded that MIA could cause complete fusion of the DIT and TMT joints in normal horses within 24 weeks. This suggests that this relatively straightforward, inexpensive, and non-invasive method could be a promising treatment option for distal tarsal osteoarthritis in horses.