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I'm looking at having a total shoulder replacement. I thought I'd do some homework before going to see the surgeon. I see there are cemented and cementless implants. And plastic versus metal-backed parts. What are the differences in these features?

It's always a good idea to gather a little information that could help you when making major decisions such as having a total shoulder replacement (TSR). Knowing a bit about the different models and makes of implants can help you understand suggestions the surgeon might make. Many times, the decision regarding implant type and design is determined during the operation. Once the surgeon can see inside the joint and assess what needs to be done, then it's much clearer what type of prosthesis might work best. Some surgeons have implants that they prefer to use. The more they do the surgery with that implant, the better their technique and more the results improve. Cemented implants are used most often when there is bone loss from osteopenia or brittle bones from osteoporosis. It may take longer for the bone to fill in around the implant. The cement helps hold everything in place until full healing takes place. When cement isn't needed, the implant is press-fitted. It's just like it sounds: the implant is pressed into the bone and fit to tightly match the shape of the area. Tiny holes in the implant fill in with bone material to hold it in place. Some components combine metal-backed with polyethylene (plastic) liners. The thin liner can be exchanged with a new one if and when it wears out. This can be done without removing and replacing the entire joint. All metal components are larger than all-polyethylene. The larger implant is often selected on the basis of patient size. Small patients get the smaller plastic implant. Larger patients receive the metal-backed piece. Other than that, there isn't a lot of evidence yet that one works better than another (or lasts longer). Studies do show that overall, total shoulder replacements provide pain relief and improve motion for patients with osteoarthritis no matter which type is used.

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