Taking Another Look at the Reverse Total Shoulder ReplacementThe reverse shoulder total arthroplasty (rTSA) is used for older adults who have disabling shoulder pain and loss of function due to severe rotator cuff damage. In fact, for these patients, the rotator cuff (needed for a traditional total shoulder replacement) is beyond repair.
The rotator cuff is a group of four muscles, tendons, and connective tissue that envelopes the shoulder. The rotator cuff both moves and stabilizes the shoulder. Stabilizes means it holds the shoulder in the socket and prevents dislocations.
The reverse shoulder replacement has a round sphere called a glenosphere that inserts into the area where the socket used to be. The patient's own round head of the humerus (upper arm) is cut off and replaced with a polyethylene (plastic) cup.
With this new configuration, the center of rotation changes. The angle of pull for some of the shoulder muscles also changes. Although the outcome is pain free motion, there are some limitations. For example, the patient no longer has full adduction (moving the arm across the body).
In this review article, surgeons from Switzerland share their knowledge and expertise in using the reverse total shoulder implant. They discuss the changes in shoulder biomechanics, possible complications, and their own experiences and results with this device. Photographs of patients' motion before and after surgery are provided to demonstrate the improvements with the rTSA.
The rTSA had a rocky start when it was first introduced back in the 1970s. The results were so disastrous that by the late 1980s, surgeons had given up even trying to use this implant. But eventually, a group of surgeons found a way to improve the design and reintroduced the concept of a reverse total shoulder replacement.
Since then, controversy around this surgery has continued. Some studies report excellent results while others say the complication rate is too high to continue. Efforts are being made to improve current designs. And surgeons are advised to choose their patients carefully. The rTSA isn't for everyone.
Patients most likely to benefit (and succeed) with the rTSA have a severely deficient rotator cuff that cannot be repaired. Without a properly functioning rotator cuff, when the deltoid muscle contracts, the necessary counterpull from the rotator cuff is missing. The patient ends up with pseudoparesis -- an inability to lift the arm up overhead despite the fact that the patient has the necessary range-of-motion to do so.
A good candidate for the rTSA must have good nerve function in order to ensure stability of the joint. Other muscles important to shoulder motion such as the deltoid, teres minor, and latissimus dorsi must be in good working order. At the same time, the quality of bone must be good enough to hold the screws used to secure the implant to the bone. Because the complication rate is so high and the fact that the implant doesn't last 10 years, patients must be over age 70 and inactive or at least, with minimal functional needs.
Patient selection is important but so is surgical technique. There are different ways to do this surgery. Some are more successful than others. The authors provide surgeons with a detailed description of their preferred surgical technique. They suggest that preoperative planning is very important. RTSA has also been shown effective in the treatment of patients with failed surgery for shoulder fracture.
Once the right patient has been chosen, three-dimensional CT scans help ensure that the planned operation is possible. Getting the right implant position goes a long way to provide improved motion and prevent loosening of the implant. Choosing the right implant size is also important. The larger glenospheres seem to work best.
While still in the operating room, the surgeon tests the arm for stability. Under the effects of anesthesia, the arm is moved through full abduction (away from the body) and internal rotation. There must be no sign of anterior (forward) dislocation. These movements are used most often by patients to get out of bed or up out of a chair.
Even though most studies have shown that deterioration appears on X-rays after five or six years, there are cases of continued success past the 10-year mark. Again, the authors stress the importance of choosing the right patient for the procedure. The benefits of the surgery far outweigh the disadvantages for patients who meet the criteria outlined.
Should there be problems with the rTSA, a second revision surgery may be needed. Usually it's just a matter of removing and replacing one of the component pieces of the implant. Infection or hematoma (pocket of blood) may be treated without removing the implant. The joint is flushed to remove unwanted debris and (in the case of infection), the patient is put on antibiotics. Results are more likely to be poor if the implant has to be taken out for any reason.
The authors conclude that enough improvements have been made now in the rTSA that it's worth keeping as a surgical procedure. Without it, some patients simply don't have any other options. They would be stuck living with poor motion and limited function. Further improvements of the implant design and surgical technique are called for in future research. Hopefully, it will be possible to expand the number and types of patients who will benefit from this procedure.
Christian Gerber, MD, FRCS(Ed), et al. Reverse Shoulder Arthroplasty. In Journal of the American Academy of Orthopaedic Surgeons. May 2009. Vol. 17. No. 5. Pp. 284-295.
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