Why do wrist replacements not seem to work as well as hip or knee replacements?
Hip and knee replacements are considered to be common surgeries now. Doctors have been performing them for quite a while and manufacturers are coming up with better and improved models as quickly as they can. The knee and the hip are rather straight forward joints, although they do bear a heavy load in supporting your body as you stand, walk, and move about in general. The joints have to be able to bend and rotate as needed, and be strong enough for all the demands placed on them.
The wrist, on the other hand, is more complicated. There are two bones that go from the forearm to the wrist and then the wrist is not only responsible for moving the hand around and back and forth, but the nerves and tendons that run through the wrist control the motion of your fingers. This requires a more complicated type of joint that what is used for the knee and hip.
As more wrist replacements are done, doctors and manufacturers are learning what seems to be working and what doesn't, which is resulting in new and improved implants.