Definition of terms


Autoradiograph: An image produced by decay emissions from a radionuclide. The emulsion or detector used to produce the image is usually placed in contact with or close to the tissue being examined.

Canine Brief Pain Inventory (CBPI): An owner‐completed questionnaire that quantifies the owner’s assessment of the severity and impact of chronic pain in dogs with osteoarthritis. The CBPI contains 4 questions pertaining to the severity of pain (used to calculate a mean value for the pain severity [PS] score) and 6 questions pertaining to how the pain interferes with the dog’s typical activities (used to calculate a mean value that can provide a pain interference [PI] score). The CBPI was developed and validated by use of standard methods for the stepwise development of a health‐assessment questionnaire.

Clinician’s lameness assessment: Using a scoring system ranging from imperceptible to severe, the clinician’s lameness assessment is a tool used to determine limb lameness at various evaluation points that can be tracked over time to determine improvement or deterioration.

Colloid: A mixture of insoluble microparticles (particles 1–1,000 μm) that remain distributed in solution without precipitating or settling to the bottom; nontoxic colloids are used for binding radionuclides to prevent them from escaping the intra-articular space into systemic distribution.

Conversion electron: A low-energy electron released from an atomic shell as a result of radioactive decay, resulting when gamma radiation energy emitted by the nucleus is transferred to the electron; conversion electrons are monoenergetic in contrast to beta particles.

Degenerative joint disease (DJD): The inclusive term for joint disease with end-stage arthritides such as osteoarthritis (OA), characterized by a pathogenesis that often begins with joint injury due to trauma or conformational abnormalities, followed by inflammation, deterioration of articular cartilage and underlying bone, loss of joint space, and arthritic remodeling accompanied by pain and functional loss.

Force plate gait analysis: An assessment made using an instrument that measures the ground reaction generated by a dog as it moves across the plate. This analysis is used to quantify balance, gait, and other parameters of canine biomechanics.

Homogenous Tin-117m colloid (HTC): A novel preparation of the radionuclide Tin-117m suspended in a colloid (Synovetin OA™); HTC is well suited for intra-articular administration to treat synovial inflammation caused by traumatic injury, OA, and other arthritides.

Inflammatory cycle: The cycle of chronic inflammation in osteoarthritis (OA) that contributes to symptoms and progressive joint damage. Synovitis results in the overproduction of macrophages and synoviocytes with synovial hyperplasia and proinflammatory cytokines. These inflammatory mediators move into and out of the cartilage and synovial lining, initiating and driving cartilage destruction, which results in the chronic pain, inflammation, and disability that mark the disease.

Macrophages: The most common immune cell type present in inflamed synovial tissue. They contribute both directly and indirectly to osteoarthritis progression through the induction of inflammatory mediators, growth factors and proteinases, resulting in cartilage degeneration and osteophyte formation.

Non-systemic: A treatment effect that is localized, meaning that it is not taken by mouth and does not circulate in the bloodstream throughout the body. As a non-systemic treatment, Synovetin OA™ is localized within the joint space and does not impact the entire body.

Osteoarthritis (OA): Also known as degenerative joint disease (DJD), OA is the progressive and permanent long-term deterioration of the cartilage surrounding the joints. Arthritis term for inflammation of the joints, while osteoarthritis refers to a form of chronic joint inflammation caused by deterioration of joint cartilage.

Proinflammatory cytokines: A general term for immunoregulatory cytokines that favor inflammation; produced predominantly by activated macrophages and involved in the up-regulation of inflammatory reactions.

Radionuclide: An unstable isotope of an atom that emits radiation released from the atomic nucleus. Some radionuclides exist naturally, but those with research and therapeutic applications are usually produced artificially; a radioisotope.

Radiosynoviorthesis (RSO): Injection into the synovial space of a radioisotope to treat joint inflammation and mitigate chondromalacia when systemic or other traditional therapies have failed to produce a satisfactory response. The goal of RSO is reduction of both pain and synovial hypertrophy.

Radioactive materials (RAM) license: Obtaining radioactive materials in hospitals, colleges, and industries for medical, research, and industrial purposes requires a license from the state of operation. The objective of the licensing program is to ensure radioactive material is used safely and disposed of properly, while facilities are free from contamination.

Synoviocytes: The cells of the synovium, the connective tissue that lines the inside of the joint capsules. A joint capsule, also called an articular capsule, is a bubble-like structure that surrounds joints such as the elbow, knee, and hip.

Synovitis: Inflammation of the synovial membrane that lines the joints. The joint usually swells due to synovial fluid collection, a condition that has been shown to precede radiographic evidence of canine osteoarthritis. Long-term occurrence of synovitis can result in degeneration of the joint.

Tin-117m (Sn-117m or 117mSn): An artificially produced radionuclide of tin with medical applications for localized treatment and imaging. Tin-117m has a half-life of 14 days. Two principal forms of the energy that it emits are (1) conversion electrons that have a short penetration range in tissue (~300 µm), and (2) imageable gamma radiation, which enables monitoring of local distribution in tissue. Tin-117m is metastable, indicated by the “m” suffix, meaning that it is a radioisotope with an energetic nucleus and a relatively long half-life and therefore distinct from highly unstable radionuclides with shorter half-lives.

Synovetin OA™ delivers sustained OA pain relief.1

Synovetin OA™ provides targeted, non-systemic therapy.2


  1. Data on file, Exubrion Therapeutics.
  2. Donecker JM, Fox SM. Safety and effectiveness of Synovetin OA™: Results of three randomized trials evaluating treatment of naturally occurring canine elbow osteoarthritis. Exubrion Therapeutics, July 2019.