The base of the thumb (where it joins the wrist) is a common spot for arthritis that can be very disabling. This joint is called the thumb basilar or carpometacarpal joint. Arthritis of the thumb makes it difficult to pick up objects, open doors, turn a key in a lock, get dressed, and many other daily activities we often take for granted.
More than half of all women in their 70s and older will experience this type of problem. Collapse of the basilar thumb joint will cause a zigzag shift throughout the rest of the thumb. As part of the zigzag shift, the metacarpophalangeal (MCP) joint becomes hyperextended. The MCP joint is the large knuckle at the base of your thumb.
The pain, loss of motion, and weakness that occur as a result of this deformity can make the simplest task impossible. What can be done to treat thumb basilar joint arthritis and in particular, the resulting MCP hyperextension deformity? That is the question many hand surgeons face as they try to help patients with this difficult problem.
A review of the literature shows many different surgical approaches. But no one single procedure has risen above the others as being superior. There are ligament and tendon transfers, fusions, pinning procedures, bone removal, and capsulodesis. This last technique involves shifting the metacarpal attachment of the volar plate. The volar plate is a very thick ligament that prevents hyperextension from occurring.
The goal of surgery is to stabilize the MCP joint and possibly bring the thumb into a more functional position. Both function and appearance can be improved. But which surgery to choose remains an unknown. Without evidence to show what works best, the choice of surgery is left up to the surgeon.
Results seem to vary depending on severity of deformity, presence of joint instability, and surgical approach taken. Some patients regain full use of the thumb. Others have an improved cosmetic result but no change in their ability to use the thumb.
Some studies show that unless the MCP deformity is at least 30 degrees or more, no change can be expected with surgery to correct the problem. For patients with degenerative joint disease and an unstable joint that won't realign, joint fusion may be the only reasonable choice.
Experts agree there is a need for future studies to compare results of different treatment options. Research is needed to show if there is even a need for surgery at all. The question needs to be answered whether surgery improves function enough to make it worth it. And of course, which procedure is the most effective must be determined.
Reference: David M. Brogan, MD, and Sanjeev Kakar, MD. Metacarpophalangeal Joint Hyperextension and the Treatment of Thumb Basilar Joint Arthritis. In The Journal of Hand Surgery. April 2012. Vol. 37A. No. 4. Pp. 837-838.