Replacement finger joints MCP/PIP - After surgery when can full function be expected. What are my new joints made of?
The MCP (metacarpophalangeal) joints are the knuckle joints where the finger joins the palm. The PIP joints (proximal interphalangeal) are the middle joints of the fingers.
MCP replacement with prostheses is most commonly undertaken for advanced rheumatoid arthritic change with deviation and loss of function at these joints. By far the commonest replacement joint is made from Silicone rubber. Because of its structure it does not accurately replicate the biomechanics of the joint it replaces, and so full function is never restored. In addition it is made of a friable material and for this reason it is subject to attritional wear. Most surgeons therefore use it almost exclusively in the low demand low load hands of rheumatoid patients where it can be very successful indeed.
In addition the joint has no inherent lateral stability, which is not a problem in the MCP because the adjacent joints bolster it, but in the PIP it can pose problems resisting lateral stress.
Many of us believe that the ideal range of motion after an MCP joint replacement is about 30 to 40 degrees, compared with 90 degrees in the unaffected hand.