Radioactive Tin117m, or Synovetin, has been sparking conversations among veterinary professionals globally as a promising treatment for canine arthritis with exciting prospects. Earlier this year, we spoke to Dr Matt Brunke from VSC, who has been using this product on canine elbow arthritis with positive results.
While there are many hoops and regulations to jump through and adhere to to make this product a part of your practice, the available evidence on safety and efficacy, together with clinical results make it worthwhile as a treatment option for elbow OA.
Here are some of the highlights from our conversation with Dr Brunke.
What is Synovetin, and what is its role in the management of OA?
It’s a whole new field for Vet Med, because it falls into the category of RSO or radio synovial arthesis. This has been used in Europe on quite number of people.
A radioactive isotope is injected into a joint, which brings down the layer of the synovial membrane. The true heart of OA is where it gets its nutrition, which is the synovial membrane. When the synovial membrane becomes inflamed, there are increases in metalloproteinase and upregulation of destructive enzymes, and this leads to cartilage damage. Our approach to OA is to reduce the inflammation in the joint, in one of several ways.
The use of corticosteroids will damage cartilage in the long run, which is not exactly helpful. HA alone lacks potency.
With RSO, we calm down the number of synoviophytes that are inflammatory as well as the number of macrophages within the joint, essentially calming down the synovial membrane.
In radioactive tin material conversion electron therapy, a colloid is injected by itself into the joint under light sedation, and the patient can be discharged. It is super straightforward. It remains in the joint with a half-life of 14 days, remaining in the joint for three to five months. As a large molecule, it cannot leave the joint.
In the synovium, the body recognises it as a foreign body, engulfing the particle. The radioisotope then kills off the white blood cells and synoviocytes, effectively ‘putting out the coals of a campfire’.
What happens with the tin molecule in the joint over time, and how long are effects seen from this treatment?
The half-life is 14 days, but we inject an amount that will be active for up to six months. Efficacy papers that have been done show that there is still efficacy for up to 12 months. The radioisotope is very small, and does not cause a mechanical obstruction in the joint when left there.
Why is Synovetin only used in elbows right now?
Safety and efficacy studies have only been completed for dogs. In the USA, there are multiple regulations governing the use of this product. I can only use it in elbows in dogs. Some of my colleagues in other states are able to use it in other joints and in other species, with special permission.
Do the injections need to be repeated after a certain time period?
The efficacy papers only followed dogs for one year, but there are dogs that have been injected two or three years ago that are still comfortable and have not needed repeat injections. From a radioactive perspective, we are injecting an annual dosage, so we cannot repeat an injection within 12 months, except in special circumstances.
If we compare this with the other products on the market that we might use for IA injections, cortisone and synthetic joint fluid might need to be repeated in three to six months, PRP might need to be repeated in six to nine months. Stem cells get us about nine or 12 months. To have a study evaluating efficacy for a 12-month period is quite unique in this area.
Can you tell us a little more about the licensing and regulation surrounding this product?
If you already have radiation in your hospital, it will be a lot easier, as you will just need to amend your license. If that is not the case, you need to jump through some hoops at both the federal and the state level.
The company is very helpful, as they have created an online learning platform and guide to help you get set up. As a practice, you need to apply for all the appropriate permits, known as RAM licenses. You need to put together a proposal outlining where the product will be kept, where it will be used, your training in handling the product, how the product will be received, etc. There is a licensing fee and you need to pay for a radiation safety officer consultant on an annual basis. You also need special materials, such as Geiger counters, lead-lined trash cans and sharps containers, etc. There are quarterly reports that evaluate your paperwork.
There are some hoops, and it will take time, but it is completely worth it! I have dogs coming off of their lifelong NSAIDs, dogs walking up and down stairs unassisted for the first time in years. If it lasts six months or 12 months, it is a no-brainer.
Are there studies comparing the efficacy of Synovetin to other IA treatment options?
We are not there yet, but the research that is published includes:
Safety studies in healthy dogs shows that the Synovetin does no damage to healthy joints.
The second phase of the studies focusing on efficacy show that dogs with mild to moderate elbow OA had improved outcomes for up to 12 months.
There are no comparative studies yet, but in my clinical experience, I have patients that were being injected every four to six months with other products that were not getting as good results as we’re now seeing with Synovetin.
I am working on following my patients for a 24-month period, monitoring a host of outcome measures, and we will publish those results.
What motivated you to add Synovetin to your practice?
Elbows stink; they are frustrating, they hurt, and we don’t have good options! When I spoke to my team of surgeons about this, they were on board, just wanting a solution to elbow OA.
From a surgical perspective, there are very few good options. At this point, elbow replacements have a 30% complication rate, and if the complications are severe enough, they can’t be salvaged and the limb needs to be amputated.
I want to get dogs off of NSAIDs, I want them to have better, longer lives with fewer complications.
What is the cost implication for the owner, and how does it compare to other available treatment options?
For an average-sized dog, the treatment itself will be around USD 2200 for one elbow and USD 3000 for bilateral treatment in one day. Compare that to the cost of taking an NSAID every day: Grapaprant will cost an owner USD 15 000 to USD 2000 per year when it is taken daily.
Other IA therapies will vary in cost, but you might look at USD 500 per treatment for bilateral elbows with DepoHA, and you might repeat that three to four times per year. If you do PRP, you are looking at USD 1000 per injection. If we are doing stem cells, you could be looking at USD 3000-6000 per treatment.
So the Synovetin is very comparable in price.
What are the restrictions, cautions or contraindications for us as Vetrehabbers, if a patient with this treatment is referred for rehab?
The safe answer is we don’t know, so don’t do it. Avoid laser, ESWT, PEMF, etc. It is a targeted treatment, so we can treat other areas of the body with these modalities and avoid the elbows.
The dogs will be home and isolated for the first two weeks after treatment, so we won’t treat them in that time. If we treat them after that point, we need to avoid laser for about six months, since we don’t know how the Synovetin will interact – but we can laser other areas of the body. The Synovetin is doing its job 24 hrs a day, and doesn’t need any help.
I have patients coming in for check-ups that have gained anything from five to 25 degrees range of motion, that have no effusion, and are off their NSAIDs.
It would be great to pull in the experts on all the different devices and have a discussion about possible effects.
The other reality is that with the efficacy of this treatment, the patients just don’t need the additional modalities.
What are some of the home care considerations after this treatment?
The owner needs to go through a whole host of paperwork that is well defined and easy to follow. The big considerations include no boarding or grooming facilities for two to four weeks post treatment, and reporting any complications or issues.
The most awkward one I need to cover is that if the pet passes in the first six months after injection, they can be euthanised, but before anything happens to the remains, the owner needs to speak the vet who treated their dog as there are some considerations from state to state that need to be observed.
The other regulations are pretty simple. The biggest is that they can’t sleep in bed with their owners for two to four weeks, they are limited to three hours a day of close contact (one to three feet away) per day, and 15 minutes of super close contact (less than 12 inches). Close contact is measured from your sternum to the dog’s elbow, not from your foot to their elbow.
It is a very safe product.
When it comes to treating elbow OA, there really are no good, long-term treatment options. Even with the restrictions and legislation around Synovetin, it would appear to be a viable, relatively affordable and effective treatment option for this joint – something we are severely lacking at this point in time.
To listen to the full interview with Dr Matt Brunke, including some additional valuable nuggets of information and comments, questions and experiences from Vetrehabbers, watch the interview here: