Tin-117m radiosynoviorthesis safely and effectively manages canine osteoarthritis with minimal radiation exposure: a narrative review

Canine osteoarthritis (OA) is a major contributor to chronic pain, mobility loss, and premature euthanasia. Although multimodal care is standard, many dogs experience incomplete relief, adverse events, or limited access to care. Radiosynoviorthesis (RSO) is a targeted IA therapy that delivers localized radiation to inflamed synovial tissue, reducing synovial effusion and alleviating joint pain. While various RSO agents have been used for over 70 years in human medicine to manage inflammatory joint disease, tin-117m (Sn-117m) is the first RSO agent adapted for veterinary use and approved for the treatment of canine OA. Sn-117m is a radionuclide emitting low-energy conversion electrons with minimal tissue penetration and, unlike systemic radiotherapeutics, Sn-117m remains confined within the joint capsule and does not form radioactive metabolites. This containment minimizes environmental contamination and limits caregiver exposure. This narrative review synthesized current evidence on the clinical use of Sn-117m RSO in dogs, addressing therapeutic efficacy and effectiveness, safety, and caregiver radiation exposure. Sn-117m offers a minimally invasive alternative to fill this treatment gap. Following a single injection for OA, prospective clinical trials report sustained improvements in objective gait analysis and caregiver-reported pain scores with benefits lasting up to 12 months. Modeled and measured radiation exposures for caregivers remain below US Nuclear Regulatory Commission limits, allowing outpatient use without isolation. This review evaluated existing data, highlighted regulatory and implementation considerations, and identified areas of potential further research. Long-term outcome tracking and expanded joint-specific data could help refine the use of RSO in human and veterinary medicine.