This week’s Orthopaedic Crossfire® debate was part of the 18th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “Dr. Krishnan v. Lederman: OA in a 50-year-old: Stemless TSA Trumps Resurfacing Arthroplasty.” For is Sumant G. Krishnan, M.D., Baylor University Medical Center, Dallas, Texas. Opposing is Evan S. Lederman, M.D., University of Arizona, College of Medicine, Phoenix, Arizona. Moderating is Thomas S. Thornhill, M.D., Brigham and Women’s Hospital, Boston, Massachusetts.
Dr. Krishnan: I’ll say it right off the bat that my debate opponent, Evan Lederman, can probably put any shoulder arthroplasty in better than any human being in this room. Because of that he’s going to make anything look anatomic.
For the rest of us, we have to find a way to do this operation reliably. This quote was attributed to da Vinci, “Simplicity is the ultimate sophistication.” I’ll have you keep that in mind.
Dr. Neer, who taught all of us about shoulder arthroplasty, wrote; “My philosophy is as near normal anatomy as possible. And the radius of curvature of the humeral head, matching it anatomically, allows the cuff to be repaired and rehabilitated around it.”
Again, we are talking about the rotator cuff and replacing the proximal humerus with something metallic to give you this same function that we would have with normal anatomy. Well, we know the last 20 years have taught us many things about the proximal humerus—it’s not so forgiving. Increasing the thickness of the humeral head by just 5 millimeters decreases the range of motion of the glenohumeral joint. This is because of the concavity compression effect of the rotator cuff. So, the humeral head doesn’t just sit in the middle of the glenoid it actually glides on the glenoid.
Dr. Warner and his group have demonstrated beautifully the motion patterns that occur in a normal anatomy of the glenohumeral joint and how that’s necessary to be replicated with prosthetic anatomy. But we also know that you can’t make it too small because by decreasing the thickness of the humeral head, you affect glenohumeral joint excursion—which, again, is purely related to rotator cuff function.
The consequences of shifting the humeral articular surface is rotator cuff tendinopathies and, potentially, glenoid loosening.
When we talk a stemless replacement we are referring to resecting the articular surface of the proximal humerus and replacing it versus a resurfacing arthroplasty, which is putting a cap on a humeral head. So, I’ll just ask you a couple key questions; would you like something that’s too big? Would you like a cap that’s too small? A cap that’s too high? A cap that’s too low? Or perhaps something that looks anatomic?
The advantage of stemless total shoulder arthroplasty is that it is canal sparing. As shoulder surgeons we have tried to invade the proximal humerus less and less over the years. We’ve tried to become bone sparing. We try to preserve the proximal humerus for the next operation, if necessary, especially in a 50-year-old patient.
Easier glenoid exposure; there is no debate about that. If you have the humeral head sitting in your face and you’re trying to replace the glenoid it’s more technically challenging than simply resecting the proximal humerus and replacing the glenoid.
If you are doing a resurfacing arthroplasty, you have to exactly match the thickness of your implant to the thickness or thinness of the cartilage that you’ve removed and also replace the bone in such a way that the cuff functions anatomically. Which, I submit, is pretty easy to do if you actually cut the humeral head and replace the head with what you took off.
There are disadvantages. The FDA approval is pending for many of the designs and at this point I believe that there is still only one implant that is FDA approved for use in the United States. There is no mid- to long-term outcome data and no real durable studies on implant longevity beyond a two-year time frame as this is an evolving concept.
Worldwide, as of 2014, there were more than ten thousand cases reported.
Prospective two year follow up studies have now been performed in Austria, France, Belgium, Canada, and here in the U.S., demonstrating that at least in the short-term—and for anything regarding arthroplasty, whether it’s hip, knee, shoulder, elbow or ankle, two years is by and large just short-term data-this can be a very viable option.
Is this really a debate? In your own mind, in your hands, you decide.
