Have you ever heard of someone having 'buyer's remorse' after getting a joint replacement? That's how I feel with my 'new' shoulder replacement. At this point, I'd rather have my old shoulder back. This new one has been nothing but trouble. First it sank down into the bone. I had a bone graft to help shore it up. Then the bone graft didn't 'take.' What next?
If you had a perfectly shaped shoulder with good bone stock, you probably wouldn't need a shoulder replacement. But the long-term effects of osteoarthritis (the number one reason for joint replacement) alter joint shape and biomechanics. And if those changes are not corrected during joint replacement, the chance of implant failure increases dramatically.
Surgeons performing shoulder replacements are often faced with challenging joint deformities. There can be areas of uneven or increased points of joint contact, defects in the bone, and twists or torsions of the bone structures. Poor bone quality can make it difficult for the implant to have the support it needs to function properly and last for a long time.
The technical difficulty of correcting shoulder joint deformities can contribute to the problems you are describing. Modifications must be done during shoulder replacement surgery but before inserting the new joint (called a prosthesis or implant).
It may be necessary for the surgeon to use a technique called eccentric reaming. Reaming helps restore normal, even contact between the round head of the humerus (upper arm bone) and the glenoid fossa (shoulder socket).
The surgeon uses a shaver to reshape the curvature of the shallow socket and make it the same depth from front to back. Proper reaming is required for the implant to sit inside the socket and move with even contact and force between the two parts of the prosthesis. If there is more than 15 degrees of retroversion (backward twist), then eccentric reaming cannot be used effectively. Anything more than that requires the second treatment option: bone grafting.
When there isn't enough bone to work with, then the surgeon turns to bone grafting to smooth out uneven wear. There are many advantages to this approach and a few disadvantages. On the positive side, the bone graft usually lasts a long time and is considered a permanent solution. The surgeon can use the patient's own bone by using the removed humeral head.
Using bone graft material also gives the surgeon a chance to restore a more normal joint line. This effect prevents altered joint motion, which could lead to implant failure. On the downside, bone grafts can break down and dissolve or fail to bond with the natural bone. This may have happened to you.
The third solution (augmented glenoid component) refers to the use of plastic liners to help restore a normal joint line and build up areas of thin or deficient bone. Long-term studies to show results with this solution are not yet available. But it may be something your surgeon considers as a way to salveage (save) the implant and the joint.
When choosing the best surgical procedure, the surgeon must evaluate each patient individually to determine all possibilities. Every effort is made to avoid implant loosening or failure for any reason. The surgeon takes into consideration the amount and severity of bone loss and the type of deformities present. Eccentric reaming works well for mild bone loss or minor joint changes. More severe problems may require more extensive surgery (e.g., augmentation, bone graft, or joint resurfacing).
Implants that sink down (an event called subsidence) or that loosen may do so because of deficiency (weakness) in the bone. There may be other factors as well. Your surgeon is the best one to help you understand why (if there is a known 'why') these problems have developed and what is the next step in treatment.
There may be some surgical options as well as some choices in rehab that could help you. A strengthening program or some time focusing on reducing painful symptoms may be helpful during this transition phase. The next step is certainly to make a follow-up appointment with your surgeon (if you haven't already done so). You may also want to consider a second opinion from another surgeon who has expertise with shoulder replacement surgery.
Benjamin W. Sears, MD, et al. Glenoid Bone Loss in Primary Total Shoulder Arthroplasty. In Journal of the American Academy of Orthopaedic Surgeons. September 2012. Vol. 20. No. 9. Pp. 604-613.
*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.