Hand and Wrist Joint Replacements
Richard Baker Blog
Joint Replacements in the Hand and Wrist
There are many joints in the hand and wrist, and they are prone to developing arthritis just as other joints in the body. Arthritis means pain, swelling and reduced motion due to wear and tear within the joint, or more specifically loss of the soft cartilage surface of the joints. This occurs in all of us as we age, but in a minority of people it leads to pain. An effective way of relieving pain in joints is to remove the joint entirely and fuse the bones together. However, this means the joint does not move at all.
An alternative that preserves motion is to replace the joint with a mechanical device or prosthesis. There are some advantages to replacing joints in the hand and wrist. Firstly, the hand and wrist are not weight-bearing joints in contrast to the hip and knee, so they do not have to be as strong. Secondly, the hand is more resistant to infection than other parts of the body because of its excellent blood supply. The disadvantage of the hand as a site for joint replacement is that there are no muscles crossing the individual joints in the hand; for example, there is no muscle in the fingers. This means that the joints are inherently less stable than, for example, the hip and knee.
Many joint replacements have been devised for the hand and wrist and only a minority have proved to be durable and safe. Silicone joint replacements first devised by an American surgeon called Swanson have been around for decades. They are particularly used in people with rheumatoid arthritis, which is an inflammatory arthritis. These joints are not particularly strong or stable but they have a very long track record of safety and are relatively straightforward to implant. These implants are particularly useful in the knuckles of the fingers.
More modern implants have used steel, titanium and, most recently, PyroCarbon, that mimic the shape of normal joints and provide a smooth, frictionless surface to minimise stiffness. Arthritis at the base of the thumb is very common and many joint replacements have been devised for this joint that have come and gone over the years. However, in the past decade or so a new device called the Maia prosthesis has been devised for the thumb base and it has an excellent track record over 10 years. The advantage of this device over the standard procedure, which is removal of the trapezium, is that thumb length and mobility is preserved and the postoperative pain considerably less with a quicker rehabilitation. I find this device particularly useful in the relatively young patient between 50 and 65.
There are joint replacements in the wrist as well, despite the wrist being the most complicated joint in the human body. There are two main joints in the wrist: the radiocarpal joint and the radioulnar joint. The radiocarpal joint can be replaced with a hinge-like device and the radioulnar joint can be replaced by inserting a device onto the end of the ulna bone or by replacing both radial and ulnar components with a prosthesis such as the Schecker (named after the brilliant American surgeon that devised it) prosthesis. These joint replacements are complex, although they do not fully mimic the movement of a normal wrist, and very few patients require these operations.
What is the future of joint replacements in the hand? Currently, the stem of implants that is inserted into the bone is covered in a layer of hydroxyapatite which allows the bone to grow onto the implant and become firmly adherent. I think in the future there will be improvements in this technology to prevent any movement at the implant-bone interface which can cause loosening. Infection is also a challenge, and I expect that implants will be developed that have some intrinsic antibacterial properties to prevent infection. 3D printing may allow the development of custom-made implants. Of course, many years down the line I expect joint replacements will become redundant as we learn how to grow new joints in the laboratory. I do hope that my career lasts long enough for me to see that development.