Dr. Matthew Willis reviews an imaging study.
Switched Ball and Socket Adds Stability
Just when patients believe all hope is gone when it comes to shoulder pain and immobility, a procedure called reverse total shoulder replacement comes on the scene. The results for some patients can be life-changing — substituting pain-free, fluid movement for what patients have described as drill-like, shooting pain from their fingertips to their neck, simply because they reached for a can in the kitchen pantry.
The reverse total prosthesis had been used in Europe for 15 years before the FDA gave it the nod in the United States in 2005. By last year, the procedure had really picked up steam. Today, a handful of Nashville orthopaedic surgeons are offering the paradigm-breaking prosthesis, including Matthew P. Willis, MD, who completed a one-year fellowship in shoulder replacement in July at the Florida Orthopaedic Institute in Tampa. “I did about 260 shoulder replacements during my year in Florida, and half of them were reverse total replacements,” Willis said. A native of Harrogate, Tenn., near Knoxville, Willis is a graduate of the University of Tennessee Medical School and joined Tennessee Orthopaedic Alliance in August. Willis does most of his shoulder replacements at Baptist Hospital.
What’s a reverse replacement?
When the shoulder is healthy, the upper arm bone, the humerus, ends in a ball shape. That ball fits into a socket formed by the shoulder blade, the scapula. The rotator cuff is the muscle that surrounds the joint and helps lift and rotate the arm. With the reverse shoulder prosthesis, the natural structure of the shoulder is backward. The implant is designed so that the ball portion is attached to the scapula and the socket is placed at the upper end of the humerus. According to DJO Surgical, the Texas-based manufacturer of the ENCORE® brand of reverse prosthesis that Willis uses, “the forces in the joint are directed through the center of the glenosphere, converting the centrifugal (outward) forces into centripetal (inward) forces. This in turn creates inherent stability in the reversed design because of the congruency of the humeral socket and glenosphere.”
When to use the reverse
Willis said the primary reason to use a reverse prosthesis is because of shoulder instability, usually caused by arthritis or an irreparable rotator-cuff tear. To have soft-tissue stability, an intact rotator cuff “really is the key,” he said. Should a patient have arthritis but an intact rotator cuff and soft tissues that are otherwise intact, a conventional shoulder replacement is the way to go. However, if there’s a large rotator-cuff tear, for example, then the ball won’t ride properly in the socket. “If you put a conventional replacement in, it will fail early,” Willis explained. “The solution is to switch the ball and socket, so you will have a deep socket on the arm side that rotates around a ball and stabilizes the arm. Without having all of your soft tissues, you can still have an arm that’s stable without worrying about dislocation or poor function.”
So why not put a reverse prosthesis in all patients? Because the range of motion achieved is generally not quite as good as a conventional total shoulder. “You almost always want to replace your anatomy as closely as you possibly can, and that’s true for any part of the body,” Willis said. “But in this case, if you’re lacking a rotator cuff or if you have some other issue that causes instability of the shoulder, that’s when you pick a reverse.”
Willis stressed that just because a patient has had a rotator-cuff repair in the past, that doesn’t mean the patient isn’t a candidate for conventional replacement. It all depends on the structure and stability of all the soft tissue around the joint.
Younger patients rarely are candidates for the reverse procedure, but there are exceptions – a 30-year-old patient who suffered juvenile rheumatoid arthritis, for example. Another occasional use in younger patients is for someone whose shoulder frequently dislocates despite multiple surgical attempts at repair of soft tissues.
Willis has published papers on the use of a reverse prosthesis after a conventional total shoulder replacement fails, and he performed such a procedure in late October at Baptist. “When a regular shoulder replacement fails, you’re frequently left with large holes in the bone where the old prostheses were, so you have to figure out a way to put in a new prosthesis that’s stable. Fortunately, with the system I use, I’m able to do that,” he said. Willis recently authored the chapter on reverse shoulder replacement for a book to be published next year on shoulder replacements by the American Academy of Orthopaedic Surgeons.
“There’s definitely a lot of misinformation about shoulder replacements in general, particularly the reverse,” he said. “The longevity is not yet well-known, but our latest published article showed that at 8.5 years 92 percent of patients still had their reverse. In 10 to 15 years, what will the numbers be? We’re not entirely sure.”
Willis added, “One of the things that I’ll say about the reverse is that it is very useful for a lot of people who have been told that there’s not much else that can be done for them when, in fact, there are good options.”