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Knuckle replacement: Relieve pain, improve function
Special to CNN.com
If arthritis has left your knuckles in pain and unable to move like they used to, you might consider joint replacement surgery (arthroplasty). The knuckle — also called the metacarpophalangeal (MCP) joint — allows you to pinch and grip things with your fingers. Joint replacement surgery can restore strength to your fingers and improve motion and function. It can also relieve pain and improve the look of your hands.
But joint replacement can't restore all of the function in your fingers, and surgery isn't without risks. Understand what's involved in joint replacement and what you can expect after surgery. Talk with your doctor about whether knuckle replacement is right for you.Who is knuckle replacement for?
Knuckle replacement surgery is most common in people with rheumatoid arthritis. Rheumatoid arthritis almost always affects the wrist and hands. In the hand, the MCP joint — where the metacarpal bones of your hand meet the phalangeal bones of your fingers to create your knuckle — is most commonly affected by rheumatoid arthritis, although the other joints in the finger also might be damaged by rheumatoid arthritis.
Your knuckles rely on a complex system of tendons and ligaments to stabilize the bones of your hand and fingers and allow free movement of your fingers. Rheumatoid arthritis begins in the knuckles as pain and swelling around the joints. As it worsens, the swelling stretches and loosens the joint and the surrounding ligaments, causing severe deformity in the hands. Not only does this stop your fingers from functioning, but it can also be embarrassing as your fingers may appear angled and deformed.
If you have rheumatoid arthritis in your knuckles, your doctor will likely advise you to try more conservative ways to relieve your pain before you have surgery. Medications, hand splints and physical therapy can help in earlier stages of rheumatoid arthritis. Once the damage to your joints is more severe, your doctor may recommend total joint replacement.
Surgeons also perform knuckle replacement in people with other types of arthritis, including:
- Osteoarthritis. Osteoarthritis rarely affects the first knuckle, but instead it most commonly affects the joints at the base of your thumb and those at the middle and tip of your fingers.
- Post-traumatic arthritis. Injury can cause damage to the bones that make up your knuckle joints and affect the first and middle knuckle joints.
Knuckle replacement in these types of arthritis is less common than in people with rheumatoid arthritis.How is knuckle replacement surgery performed?
Joint replacement surgery takes about three to four hours, or about one hour per knuckle, and is performed while you're under local, regional or general anesthesia. As many as four knuckles on one hand can be replaced during a single operation.
If you're having all four of your knuckles replaced, your surgeon makes an incision across the top of your knuckles, perpendicular to your fingers. If you're having only one knuckle replaced, the incision runs up and down your knuckle.
Your surgeon must first carefully separate and set aside the delicate ligaments that surround your knuckle in order to gain access to your joint. Next he or she removes the inflamed lining (synovium) around your joint. Then your surgeon separates the two bones that make up your knuckle and removes any fragments of damaged or diseased bone. A hole is made in each bone and the artificial joint is inserted. Your surgeon then tightens and repairs the ligaments around your finger. Finally, the incision is stitched closed.What types of artificial joints are used?
What type of artificial joint you have is usually decided by your surgeon. He or she will factor in your age, your health and what your goals are for surgery. Types of artificial joints include:
The most common type of artificial joint is a one-piece silicone design that sits between the bones of your knuckle joint and keeps them from rubbing together. This artificial joint isn't a hinge or similar style of joint that you might expect in other joint replacement surgeries. Instead, the silicone knuckle joint simply replaces the diseased bone fragments as a spacer. In the weeks and months after surgery, the soft tissues and ligaments that surround your knuckle will heal and strengthen, allowing you to regain movement and function in your fingers.
These implants are constructed of two pieces, one of cobalt chrome metal and the other of polyethylene plastic. A ball on the end of the metal part fits into a socket on the end of the plastic piece, creating a joint that is more similar to your natural knuckle. The materials allow for greater motion and durability than do silicone joints. Metal-plastic combination joints are usually reserved for people who have minimal damage to the soft tissues around their knuckles — usually people with osteoarthritis or post-traumatic arthritis. People with rheumatoid arthritis who have less severe deformity and soft tissue damage also may be candidates for this type of artificial joint. Metal-plastic joints can last 12 to 15 years.
Pyrolytic carbon jointsWhat happens after knuckle replacement surgery?
This type of joint is constructed out of durable pyrolytic carbon and graphite, making it strong and wear resistant. These metal joints work much like the metal-plastic joints. But unlike other joints, these don't require bone cement to hold them in place. This makes the pyrolytic carbon joints less likely to come loose. This durability may make pyrolytic carbon joints an option for young people in need of joint replacement. As with metal-plastic joints, pyrolytic carbon joints require fairly healthy soft tissues around your knuckle, so they're best for people with less tissue damage and deformity in their knuckles.
After surgery a compression bandage and splint are placed over your hand to hold your knuckle joints still. In order to allow the soft tissues around your knuckles to heal, your entire hand will be immobilized for one to two weeks. For one to two weeks after that, you'll be able to move the top two joints on your fingers, but your knuckles must remain still.
You'll need to exercise your hand and relearn to use your new knuckles. A hand therapist will help you do this slowly beginning about a week after surgery and lasting four to six weeks. He or she will guide you through exercises to strengthen your knuckles.
After about six weeks, you'll be able to remove the splints and move your fingers freely. But you'll need to continue wearing a splint on your hand when you aren't using it — for instance, while you're sleeping.Results
Knuckle replacement surgery can't restore the function you had before arthritis damaged your joints. But you can expect it to relieve the pain in your knuckles, improve the look of your hands and restore some function. For this reason, the majority of people who have knuckle replacement surgery are pleased with the outcome.
A healthy knuckle allows about 90 degrees of movement in your finger. On average, knuckle replacement allows for about 45 degrees of movement.
You might find that it's more difficult to grasp small items with your new knuckles. For this reason, some people choose to have surgery on only one hand. Since rheumatoid arthritis can make it difficult to grasp large objects and surgery makes it difficult to grasp small objects, having one hand for each type of grip might be more convenient for you. Other people choose to have surgery on both hands and rely on assistive devices to help them grasp smaller objects.Risks
As with any surgery, knuckle replacement carries risks. In rare cases infection may occur. Infections that can't be treated with antibiotics may require new artificial knuckle joints.
Silicone knuckle implants last about 10 years, while other joints may last longer. You may need to have another joint replacement later in life if the pain and lack of motion in your fingers returns. Your doctor can give you the general life span of the joint you'll receive.
It's also possible for the artificial knuckles to break, though it's unclear if this is truly a complication. Many people with artificial knuckles don't notice that their new joints have broken. That's because the implants don't control finger movement — the ligaments and other soft tissues around the joint do that.
It's important to know that knuckle replacement can't always stop the damage of rheumatoid arthritis. In severe cases, swelling and pain may eventually return.Looking to the future
Silicone knuckles were developed in the 1960s. Since then doctors have worked to create new types of joints that may one day better replicate the motion of your knuckle. Many different types of artificial knuckles exist today, though modified versions of that first silicone joint remain the most popular. Newer types of knuckle replacement joints may prove beneficial for younger people and those with earlier stages of rheumatoid arthritis.
Video: Artificial knuckles