When Stephen Gunther, M.D., of Charlottesville, VA, began to dream up a design for a revolutionary new glenoid, even he didn’t foresee how successful his unique design could be in solving total shoulder arthroplasty’s number one problem, glenoid loosening.
It’s now been nearly a decade since his first InSet™ Glenoid designs were implanted and Dr. Gunther was able to follow-up with 21 of the 24 patients. He recently wrote a paper detailing the long-term results of his InSet™ Glenoid implant which were recently published in the Journal of Shoulder and Elbow Surgery (JSES), a peer-reviewed publication for eight leading specialty medical organizations.
We recently sat down with Dr. Gunther to discuss his paper and the implications of his results for total shoulder arthroplasty.
David Blue: Congratulations on publishing your paper.
Dr. Gunther: Yes, thank you. It required an incredible amount of work but was absolutely worth it. In fact, this InSet™ Glenoid project has been my life’s work for the last 15 years and it’s been so rewarding to see my efforts coming to fruition in the published results.
David Blue: Tell us about your motivation. Was there a defining moment for you in your journey creating the InSet™ Glenoid?
Dr. Gunther: Actually, there was. A long time ago, I was at UCSF performing a revision surgery that involved a broken screw from a bone graft. This ended up being a six-hour case and four of those hours were spent removing another surgeon’s broken screw from the axillary sheath, which houses the main artery and all the nerves in your arm.
It was a scary procedure that I’ll never forget. But that experience motivated me to pour all my efforts into positively affecting change in the total shoulder arthroplasty space.
David Blue: What else along the way has inspired your work?
Dr. Gunther: I spent a good deal of time performing surgeries in the California wine country where I came into contact with millwrights, truck drivers, and other hardworking people who were ignoring the pain but living with severely deficient bones with deformities. That’s when I realized that the current design of the onlay glenoid implants was not sufficient for long-term success for such difficult cases. I wanted to find a way to help these people. And I knew it had to be something completely different.
David Blue: Could you explain to us briefly how you first began to visualize this new design and how it differs from the standard glenoid implant?
Dr. Gunther: Sure. One picture that came into my mind was that of an object hanging on a wall. For instance, people hang decorative plates on walls, but imagine if you carved an indent into the wall the exact shape of the plate and then you pressed the plate into the indentation instead of hanging it on the surface of the wall. You can see how once it was securely anchored there it would be very difficult to knock loose.
Or another analogy is that of a house on a muddy hill. Do you simply set the house on the surface, or do you dig a foundation? I began to realize that for the difficult cases I was coming into contact with, a glenoid that was inlaid into the bone would provide significant benefits. And it turns out, all types of patients benefit from this design.
David Blue: Had you published any results before this paper?
Dr. Gunther: Actually, I did. My first paper showing this technique was published in the Journal of Shoulder and Elbow in 2012. But because these were my short-term results and I was reporting on a very small group of custom implants, nobody really paid much attention to it.
Together with the team at Shoulder Innovations (SI), I followed that with another paper showing the results from two independent mechanical tests in finite elements analysis. The mechanical ASTM testing, performed according to ASTM standards, took place at Knight Labs in Indiana. We set up a model which they ran independently, and it showed 87% less distraction of the far surface of the glenoid.
And then we did FDA finite element computer modeling through another independent group in Michigan. This is the same group that does blast research for the United States government, so they are very experienced. They found less stress at the edge of the implant and less stress in the bone cement interface, which could translate to both less loosening and less implant wear, in theory.
So those were two great papers in 2012. And then in 2016 and 2017, there were two more papers which validated both our scientific testing and then our clinical theory.
Quite a few surgeons began looking into it, but everybody wanted long-term data.
David Blue: And that’s what this paper finally provides.
Dr. Gunther: Exactly. This new paper gives nine-year results on the expanded cohort of the original group of patients. In the shoulder literature, this is considered long-term data on this novel technique. That’s why I devoted my time to organizing this data together into a paper.
David Blue: What all was involved in getting this data?
Dr. Gunther: I had to fly out to California multiple times to find and meet with the patients. Some of them drove five hours to meet with me. But it was encouraging how dedicated they were. And they were all so thankful for the results of their surgery and happy to see me.
And then I spent about every weekend for the last year putting the data files together to summarize. Thankfully I had a student at UVA help me with some of the work.
David Blue: How many patients were you able to follow up with?
Dr. Gunther: I was very pleased that out of the cohort of 24 patients, I was able to make contact with 21. Two had passed away and one was not traceable. But considering that these patients were ten years older and hadn’t been young to begin with and that this was the other side of the country, 21 was a very high turnout.
I was able to get 14 of them to come all the way in the clinic for a full follow-up with x-rays, and the other seven I was able to get on the phone to do Shoulder and Elbow Society outcome scores. So I have outcome scores on a mean nine-year follow-up of 21 patients, and I have final x-rays at the timeframe of 14 of them.
David Blue: That’s a great turnout. So I think the most exciting part of this interview and what everyone is waiting to hear is the outcome. Could you summarize what your paper reports from these 21 patients?
Dr. Gunther: The results were absolutely astounding. Perhaps better than anyone hoped.
The bottom line is: there have been no revision surgeries. None. There were no surgical complications, no infections. And of the 14 we followed up with, there was no evidence glenoid loosening.
What makes this data even more remarkable is these were all patients with C type glenoids, meaning severe deformity, where all the standard implants would commonly fail because there wasn’t enough bone. This was the population of patients that were at the highest risk of glenoid loosening. The normal series has up to a 40% loosening rate in five years, and this group is the worst set of patients at nine years, and we saw zero loosening and no revision surgery. These results are unbelievably positive. And we can expect even better results in patients without deficient bones.
David Blue: That’s fantastic. You must be so pleased with your work.
Dr. Gunther: Well, honestly, it’s very exciting for me to think that I invented something that can lead to fewer complications in surgery, a decrease in revision surgeries which are very expensive, a decrease in pain and suffering in patients, a decrease in healthcare expenditures, and most importantly a radical improvement in the quality of life of the patients long term after the surgery.
David Blue: One more question. What do you anticipate will be the surgeon response to your paper?
Dr. Gunther: The appetite for shoulder surgeons has been progressively increasing toward this InSet™ Glenoid as they’ve learned more and more over time, first with the critical paper, then scientific data. The only thing that was missing was the long-term data.
With that finally available, I anticipate many surgeons will see the advantages and be ready to make the switch.
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