The arthritic rotator cuff-deficient shoulder has long been a significant clinical problem due to lack of successful treatment options for this painful and disabling condition.
But this situation is rapidly changing with the evolution of implant technology and surgical technique. Since the reverse shoulder arthroplasty (RSA) implant was originally developed nearly 25 years ago in Europe to treat rotator cuff tear arthropathy, it has dramatically improved the treatment of rotator cuff conditions.
Approved in 2004 by the Food and Drug Administration, the RSA implant has also engendered controversy related to possible overuse, because indications are expanding beyond rotator cuff tear arthropathy to include a suite of shoulder pathologies. These pathologies range from reconstruction after tumor removal to proximal humeral fractures and nonunion.
After seven years' experience with RSA, Mayo Clinic orthopedic surgeons remain committed to studying it from both a clinical and basic science perspective. They proceed with expanded indications on an individualized basis, grounded in a comprehensive understanding of the biomechanics of shoulder pathophysiology.
"The reverse shoulder arthroplasty has provided an innovative and effective way to relieve pain and restore function in many patients with rotator cuff deficiencies," explains Mayo Clinic orthopedic surgeon John W. Sperling, M.D. In one large outcome study — n=80 patients, mean follow-up of 3.6 years — 96 percent of patients ranked the pain relief as good.
Adds Dr. Sperling's colleague Joaquin Sanchez-Sotelo, M.D., Ph.D.: "Reverse shoulder arthroplasty has revolutionized the field of shoulder replacement. At Mayo, our outcomes with RSA have been consistently very encouraging in terms of pain relief, motion and functional outcomes. We have been extremely careful in attempting to perfect our surgical technique, ensure component fixation and determine the optimal soft-tissue tension for each individual."
RSA reverses the natural anatomy of the ball-and-socket joint by implanting a concave socket plate into the humeral head and a convex spherical glenoid component into the glenoid fossa. RSA also treats arthritis by resurfacing the glenohumeral joint.
The goal is to reduce pain and restore function by overcoming vulnerabilities of traditional shoulder replacements in which the absence of a stabilizing rotator cuff can lead to poor function and mechanical failure of the implant.
By reversing the anatomy, the surgery improves deltoid tension and provides a stable fulcrum that compensates for loss of rotator cuff performance. In the absence of a rotator cuff, attempted arm elevation results in superior migration of the humeral head, with no real fulcrum and poor motion.
With RSA, the constrained nature of the implant provides a fulcrum that is particularly advantageous for a better tensioned deltoid. Disadvantages range from highly variable complication rate to overuse.
RSA advantages include:
RSA disadvantages include:
In experienced hands, the RSA has the potential to successfully compensate for rotator cuff insufficiency across a broad spectrum of shoulder pathologies. At Mayo Clinic indications for use of RSA range from the relatively simple to the highly complex, from rotator cuff tear arthropathy to chronic pseudoparalysis.
Patients for whom RSA may not be indicated include those who have:
With rapid expansion of RSA, highly variable complication rates have been reported in the literature — in some instances, up to 50 percent of cases. This variation can be explained in part by the fact that RSA is commonly used as a salvage technique for a failed prosthesis, and often in older patients with poor bone quality. Complications include:
At Mayo Clinic and other advanced orthopedic centers, complication rates are below 10 percent. And while these centers have promising short-term functional outcome data, the procedure is still new enough in the U.S. that large-sample, long-term results are lacking and a subject for further investigation.