“The thumb is the king of all digits, and must be treated in a princely manner.” – Barry Gainor, MD; Professor Emeritus, University of Missouri
Why is the thumb so important?
Depending on the sources that you read, the thumb accounts for 30-50% of hand function. Even though arthritis is most common in the other fingers, arthritis of the thumb accounts for more clinic visits, more time off work and a higher impact on daily activities. The basal thumb joint, also known as the thumb carpometacarpal (CMC) joint, is what sets the thumb apart from the other fingers (Figure 1). The shape of the CMC joint resembles two saddles that fit and interlock together; this allows the thumb to move in several directions, including front and back, side-to-side, but also rotation (Figure 2). These movements come together to bring the thumb out from the palm and allow it to participate in opposition. Opposition is what allows us to grab and hold various objects, pinch and twist keys.
How do we get arthritis at the base of the thumb (CMC)?
The more a joint can move in different directions, the more it relies on ligaments to keep it stable throughout these motions. The thumb CMC joint is no exception. Through a combination of genetics and environmental conditions, some people become more prone to wearing out the thumb CMC joint. We think that the stretching and wearing out of the supporting ligaments is one of the key processes that leads to joint wear and tear. When the ligaments stretch out with repetitive use, the two opposing articulating surfaces of the CMC joint don’t come together as well and the joint wears out faster. Over time, the lubricating layer of cartilage wears away and people can develop pain from bone-on-bone grinding. This process can easily be seen on X-rays (Figure 3). However, not everyone with arthritis on X-rays feels pain the same way. We think that the increased inflammation at the joint that often comes with arthritis is the reason why some people with thumb CMC arthritis have more pain than others. That is why treatment that is geared towards decreasing inflammation often work well.
How do I know if my pain is from thumb CMC arthritis?
Patients who have symptoms from thumb CMC arthritis usually report pain on the thumb side of the wrist that gets worse the more they use their hand. There is sometimes a painful bump at the location of the pain. Most people will report having difficulty opening jars, pinching objects or carrying heaving things. Typically, the symptoms may increase or decrease in intensity from one day to the other, but generally the flare-ups get worse and more frequent over time without treatment. Other symptoms include stiffness and some also report weakness with their grip.
What treatments are available?
For the majority of early cases of arthritis, treatment starts with non-surgical options to control pain and restore strength/motion. Most of these methods are geared towards decreasing the amount of inflammation at the arthritic joint. A special brace called a “thumb spica” brace can be used to support the thumb during movements and prevent certain movements that cause the pain to flare. In my experience, patient prefer a softer sleeve-like brace over the conventional firm brace because it allows them to stay active while they wear it. Anti-inflammatory medications can also be helpful, and they come in three varieties.
- Oral pills: Non-steroidal anti-inflammatorydrugs (NSAIDS) like ibuprofen (Advil™), naproxen (Aleve™), can help decrease inflammation and pain, but we often avoid using them for long term treatment because they can among other things irritate the stomach lining and cause heartburn.
- Topical: Topical anti-inflammatory gels/creams like Voltaren™ gel can be used instead of pills to avoid side effects to the body. However, pain relief is usually not as effective as the pill form
- Steroid injection: a corticosteroid injection (cortisone shot) can be used to provide targeted anti-inflammatory relief to the inflamed andpainful joint.
Occasionally, a consult with a hand therapist can be useful. Their specialized protocol usually focuses on teaching how to modify activities to avoid positions that cause pain. They can also help to give you exercises to build up strength and maintain motion.
When is surgery the right choice for me?
For thumb CMC arthritis, we try and get as much mileage as possible out of the joint before going to surgery. As long as the non-surgical methods above provide enough relief of pain to keep you active, there is no role for surgery. However, when bracing and anti-inflammatories are no longer working, surgery may be the right choice at this point.
There are many described surgeries for the treatment of thumb CMC arthritis, but the vast majority of those performed in North America involve removing the joint by taking out the carpal bone at the base of the thumb called the trapezium. This gets rid of the bone-on-bone grinding and leads to pain relief while maintaining motion. The surgery is very successful at relieving pain, but for some it can make their thumb a bit weaker with pinch and grip. Many hand surgeons will use various methods to stabilize the thumb metacarpal after removing the trapezium to prevent the thumb from shortening. Some methods currently involve taking a tendon from the wrist to create a new stabilizing ligament. This method works well but requires patients to be in a cast for 6 weeks after surgery, which often leads to stiffness. In the last 4 years, I have switched to using an implant called the “internal brace” to stabilize the thumb (Figure 4). The implant is made of two small anchors that are linked together with a strong suture sling, which forms like a hammock supporting the thumb metacarpal and preventing the thumb from shortening. The implant is hidden deep so it can’t be felt through the skin. One advantages of this technique is the single-incision approach which is often less than an inch. The other more important advantage is that the internal brace is stronger than the conventional method, which allows for early motion at 2 weeks post-surgery (instead of 6 weeks). This was a game-changer for me. Seeing my patients start moving their thumbs at 2 weeks with minimal discomfort is why I changed over to this technique. Although the long-term results are the same regardless of the fixation method, the improved function in the short term is why I prefer this surgery for my patients.