The fingers can be affected by osteoarthritis (‘wear and tear’ arthritis), rheumatoid (inflammatory) arthritis, or arthritis that occurs because of joint injury (post-traumatic arthritis). Any of the three finger joints can be affected. The distal interphalangeal (DIP) joint is the smallest joint closest to the finger tip. The proximal interphalangeal (PIP) joint is the joint in the middle of the finger. The metacarpophalangeal (MP) joint is the main big knuckle, where the finger attaches to the hand.
Regardless of the cause, the first treatment for finger arthritis is non-operative. A steroid injection can be very helpful. Splinting or “buddy taping” the finger to its neighbor can help decrease stresses on the painful joint.
If these non-operative measures fail and the joint is sufficiently painful, then surgical treatment may be considered. The DIP joint requires stability, to aid in pinching and grasping. Therefore, this joint is fused so that it’s stiff, strong and painless. This is a straightforward, outpatient, relatively predictable surgery. The DIJ is splinted for 2-6 weeks, but the rest of the hand can be used fairly normally.
For PIP joint arthritis, the surgical options are fusion or replacement. Fusion renders the PIP joint stiff, stable and pain-free. As above, this is a straight-forward, predictable surgery with a low complication rate. PIP joint replacement allows motion to be retained. This is more complicated surgery, but is often preferred, as motion is desirable. The decision depends on numerous factors, including which finger is affected, what caused the arthritis, what the patient’s demands are, and how much time and effort the patient can commit to therapy. In general, the index finger’s PIP joint is fused and the middle, ring or small finger’s PIP joints are replaced.
Proximal Interphalangeal (PIP) Joint Fusion
The index finger’s PIP joint is best fused because the index finger is used primarily for pinch. When the index finger opposes the thumb to create power during pinch, this creates a significant sideways stress on the PIP joint. Current PIP joint replacements simply cannot handle this sideways stress, and will become unstable. On the other hand, fusion leads to a stiff but pain-free and stable platform for pinching. The loss of PIP joint motion is not a significant problem for the index finger.
Because the middle, ring and small fingers are used for grasp, motion of the PIP joint of these digits is important. For that reason, PIP joint replacement may be considered. As for most joint replacements, there are fewer problems with older patients. The reason for this is because joint replacements have a limited ‘life expectancy’, and do not last as long in younger, higher demand individuals. Having said that, the newer joint replacements may be better suited for younger, higher demand individuals, within reason.
Proximal Interphalangeal (PIP) Joint Replacement
PIP joint replacement is performed as an outpatient surgery. The newer metal and polyethylene (a very tough plastic-like material) replacements usually work better than the pyrocarbon implants that were popular a few years back. These are newer devices that are similar to a total knee replacement, and made from the same material, but are obviously much smaller. (Figures 41 & 42). We think that these may last longer than the one-piece linked replacements, but won’t know for sure for another decade or so. An example of the newer (SR-PIP) joint implant can be seen at www.totalsmallbone.com/us/products/hand/sr_pip.php4
After PIP joint replacement, motion is started within a few days after surgery with hand therapy. Ultimate motion is about 50% of normal, roughly a 60° arc of motion. It is unclear how long the newer PIP joint replacements will last.
Unfortunately, these newer unlinked PIP joint replacements are not appropriate for patients with advanced rheumatoid arthritis. Rheumatoid arthritis is a much rarer inflammatory condition than the typical osteoarthritis (i.e. arthritis from ‘wear and tear’). People with rheumatoid arthritis have poor ligaments. Because of this ligament laxity, unlinked replacements, such as the SR-PIP, will be unstable. For rheumatoid arthritis, the old-fashioned one-piece linked silastic (a type of rubbery plastic) replacements provide intrinsic stability and are better options. The post-operative therapy is the same. The post-operative motion for patients with rheumatoid arthritis is less, because motion is limited by the condition of the finger’s tendons. Sometimes people wonder which type of arthritis they have: In most cases, unless someone has been formally diagnosed and placed on medication for rheumatoid arthritis, the most probably diagnosis is simple osteoarthritis or post-traumatic arthritis (due to a previous injury).
The good news: for people with PIP joint arthritis, there are now better treatment options than were previously available. Most patients are very happy with the pain relief and function afforded by these newer PIP joint replacements.
Metacarpophalangeal (MP) Joint Replacement
The metacarpophalangeal (MP) joint is the large joint where the finger attaches to the hand. Arthritis of the MP joint can lead to pain, swelling and stiffness. Non-operative management includes a steroid injection or two, activity limitation and buddy taping the finger to its neighbor. Once non-operative management fails, the MP joint is best replaced, not fused, as it’s the major joint of the finger. There are two major types of replacement, depending on what caused the arthritis.
If the joint’s ligaments are intact, as is usually the case with osteoarthritis (from ‘wear and tear’ and post-traumatic arthritis (from an injury), it is possible to use one of the new metal and polyethylene (a very tough plastic-like material) total joint replacements. These replacements are made from the same materials that hip, knee and shoulder replacements are made out of. They are believed to last longer and provide better function than the older single-piece hinged silastic (a rubbery plastic) joint replacements. As for the larger joints, each side of the joint is resurfaced by a separate implant, for a total of two pieces. (Figure 43) These MP replacements are an effective surgical option placed during an outpatient procedure. We believe that these newer joints may last longer than the one-piece linked replacements, but won’t know for sure for another decade or so. An example of the newer (SR-MCP) joint implant can be seen at http://www.totalsmallbone.com/us/products/hand/sr_mcp.php4
In patients with rheumatoid arthritis, all of the MP joints can be involved, and the fingers can angle away from the thumb, making it difficult to use the hand to pick up and pinch objects. (Figure 44) Rheumatoid arthritis causes the fingers to deform, sublux and eventually dislocate because rheumatoid arthritis destroys not only the joint, but also the ligaments that hold the joint in position and the tendons that move the joint. Because rheumatoid arthritis destroys the ligaments that support the joint, the newer type of total joint replacement cannot be used, because there are no ligaments to stabilize the two separate pieces. Therefore, the older hinged silastic replacement must be used, as these single-piece joint replacements provide their own stability to the joint. These silastic implants work well, but will eventually break after a number of years. Having said that, good function often remains even after they break; broken silastic joints don’t necessarily have to be replaced.
As far as timing goes for patients with rheumatoid arthritis, MP joint replacement should be strongly considered once the MP joint dislocates. The reason is because following joint dislocation, the bones of the finger start to progressively drift up into the palm of the hand. This causes the soft tissues to shorten. Then, when MP joint replacement is finally performed, the finger cannot be brought out to length. At this point, in order place the new joint, a significant amount of bone needs to be removed from the bones of the hand. So now the MP joint replacement can no longer be placed in the wide area at the end of the bone, but must instead be placed in the narrow shaft of the bone (think of how a dog bone in wider on either end than in the middle). Placing an MP joint replacement in the narrow shaft doesn’t provide as much stability as the wider bone ends do, predisposing to complications and possibly shortening the life-span of the replacement. While early motion is started in patients with the more modern MP joint replacements, patients with rheumatoid arthritis require 5 weeks of casting post-operatively, in order to let the ligaments and other soft tissues stabilize.
Both types of replacement provide excellent pain relief, improved cosmetics, and an average of about 50% of normal motion. However, that amount of MP joint motion is still very functional. Even though it’s not full motion, having 50% of pain-free motion is almost always better than having motion that causes pain, as when a joint is painful its function is usually significantly compromised.