Long-Term Results of Pyrolytic Carbon Implants for Finger Joint Replacement
Take a moment to look at the knuckles of your hand. The main bumps across the back of your hand are the metacarpophalangeal or MCP joints. Now try moving your fingers or hand without using those MCPs (knuckles) and you'll see why they are important to everyday life and function. For people with osteoarthritis (OA) of the MCPs, pain, stiffness, and deformity can lead to disability and loss of function. Quality of life is affected as the individual is unable to participate in work, play, or daily activities.

Fortunately, this condition (osteoarthritis of the MCPs) is uncommon. Treatment begins conservatively with hand therapy, medications to control pain and inflammation, and sometimes steroid injections. Surgery is a last resort type of option but consists of joint replacement. In this report, one surgeon reports the results of 11 patients who had an implant made of pyrolytic carbon placed in the index or middle finger MCP joint.

The implant is made by burning and separating hydrocarbon gas to make it chemically stable. The process makes the material biologically compatible (acceptable to the body). Pyrolytic carbon implants have been around and in use for finger joint replacements for 20 years or more. But the use of these devices for osteoarthritis (OA) of the metacarpophalangeal (MCP) joints has been limited. In fact, there is very little data reported on the results (especially long-term outcomes) for this condition. That's what makes this study so important.

All patients received the implant from one single surgeon. They were followed for at least two full years. Results were measured using pain, motion, function, and patient satisfaction. Assessment tools included the Michigan Hand Questionnaire and the Quick Disabilities of the Arm, Shoulder, and Hand survey. X-rays were used to look for implant loosening, fracture, movement, subsidence (sinking down into the bone), or failure of any kind.

The surgeon reports that motion was significantly improved from before surgery to after. Grip strength was better than before surgery but less than the other hand. Pain was mild (rated as a one on a scale from zero to 10) if there was any pain at all. And 10 of the 11 patients were fully satisfied with the results.

There were a few problems reported along the way. Two of the patients noticed clicking and squeaking when they moved the finger. There were no other symptoms accompanying the noises (e.g., no pain, no swelling, no tenderness). The one patient who was unhappy with the results had joint stiffness, constant pain, and squeaking for no apparent reason. She ended up having a joint fusion (arthrodesis) seven months later. In general, there was no sign of implant failure for any of the patients. Everyone had a little subsidence (implant sinking down) but this did not continue to get worse and presented no problems.

In summary, long-term results of surgical placement of pyrolytic carbon implants in the metacarpophalangeal (MCP) joints of the hand are positive. Symptoms improve, satisfaction is high, and the implants hold up well. Patients are able to get back to work and/or daily activities requiring the full use of the fingers and hands.

Pyrolytic carbon implants are a good solution to problems caused by osteoarthritis that are not corrected or improved with conservative care. Good alignment of the fingers is possible with these implants when the patient has healthy, undamaged soft tissues and ligaments. Without good soft tissue structures (e.g., with patients who have rheumatoid arthritis), this type of unconstrained implant (produces less stress where the implant meets the bone) cannot be used.
Lindley B. Wall, MD, and Peter J. Stern, MD. Clinical and Radiographic Outcomes of Metacarpophalangeal Joint Pyrolytic Carbon Arthroplasty for Osteoarthritis. In The Journal of Hand Surgery. March 2013. Vol. 38A. No. 3. Pp. 537-544.