Q: Can you please give me some basic info on reverse shoulder replacements?

A: Along with hip and knee joint replacements, shoulder replacement has become increasingly popular for people with pain and loss of motion from arthritis. But the shoulder is a bit different from the hip and knee. A tear in the muscles around the shoulder (called the rotator cuff) can complicate things.

Replacing the joint without an intact, functioning rotator cuff may not improve the situation. Without the muscles to hold the joint in place and move the arm, the surgery may not be successful. Surgeons who recognized this problem designed a special replacement joint (implant) just for large rotator cuff tears that cannot be repaired.

The procedure is called a reverse shoulder arthroplasty. The round ball-shaped bone that normally fits into the shoulder socket is removed and replaced with an artificial cup. The anatomic socket is replaced with a titanium round head. The two parts of the shoulder (round head and socket) are reversed in location.

The indications for this surgery are pain, loss of shoulder motion, and failed conservative (nonoperative) care. A rotator cuff tear that is too large to repair is another criterion for the use of the reverse shoulder arthroplasty.

In a recent study, the surgeon who designed the reverse shoulder implant investigated the results of treatment with this implant. The focus was on patients who had a massive rotator cuff tear but no sign of shoulder joint arthritis. The study was done at the Foundation for Orthopaedic Research and Education in Tampa, Florida. It was funded by the company that manufactures the implants (Don Joy Orthopaedic Surgical company).

Results were measured using patient report about pain, X-rays to look at the joint, and several tests of shoulder strength, motion, and function. There were two groups: those who had a previous shoulder surgery (usually a failed rotator cuff repair) and those who had never had shoulder surgery before. Results were compared between the two groups.

They found significant improvements in all areas measured for both groups. There were a few failed implants and 18 of the 60 patients said they wouldn't have the surgery if they had it to do over again (unknown reasons why they felt that way). Two-thirds of the group had an excellent result and were very pleased.

The patients most likely to be disappointed with the results were those who had severe shoulder pain but fairly good motion (greater than 90-degrees). Sometimes after the reverse shoulder implant, their motion was less than before surgery.

When problems occurred with the reverse shoulder arthroplasty, it was usually because the implant came loose or broke. Other complications included fracture of a bone in the shoulder complex affecting the humerus (upper arm bone), clavicle (collar bone), or scapula (shoulder blade). Shoulder dislocation, deep infection, and hematoma (pocket of blood) were also reported in individual patients.

Reference: Philip Mulieri, MD, et al. Reverse Shoulder Arthroplasty for the Treatment of Irreparable Rotator Cuff Tear Without Glenohumeral Arthritis. In The Journal of Bone and Joint Surgery. November 3, 2010. Vol. 92A. No. 15. Pp. 2544-2556.