When you stop to think about how much you use your thumbs, it’s easy to see why the joint where the thumb attaches to the hand can suffer from wear and tear. This joint is designed to give the thumb its rather large range of motion, but the tradeoff is that the joint suffers a lot of stress over the years. This can lead to painful osteoarthritis of this joint that may require surgical treatment as the arthritis progresses.
This guide will help you understand
- How arthritis of the thumb develops
- How it is diagnosed
- What can be done for the condition
Where is the CMC joint, and what does it do?
Several strong, thick ligaments hold the CMC joint together. The ligaments allow for motion but keep the joint from sliding too far and prevent thumb dislocation. This function is called ligamentous restraint. These ligaments can be injured, such as when you sprain your thumb. There are also nine muscles that provide dynamic stabilization of the CMC joint. These muscles coordinate together to create a balance of stability. They put the thumb in positions that allow optimal function for thumb-pinch activities.
What causes arthritis of the thumb?
Injury to a joint, such as a bad sprain or fracture, can cause damage to the articular cartilage. An injury to the CMC joint of the thumb, even if it does not injure the articular cartilage directly, can alter how the joint works. After a fracture of the thumb metacarpal, the bone fragments may heal in slightly different positions. The joints may then line up differently. This is also true when the ligaments around the CMC joint are damaged by a sprain. When an injury results in a change in the way the joint moves, the injury may increase the forces on the articular cartilage surfaces. This is similar to any mechanical device or machinery. If the mechanism is out of balance, it tends to wear out faster.
Over many years this imbalance in the joint mechanics can lead to damage on the articular surface. Since articular cartilage cannot heal itself very well, the damage adds up. Eventually, the joint is no longer able to compensate for the increasing damage, and it begins to hurt. Damage has occurred well before the pain begins.
Women are three time more likely than men to develop arthritis of the CMC joint. There are several reasons for this. Women have higher amounts of certain hormones that are linked with joint laxity (looseness). There are also some anatomic differences in the joint surfaces between men and women. Increased joint motion from laxity combined with differences in the shape and surface of the bones add to the risk of CMC arthritis in women.
Adults with increased body mass index (BMI) are also at risk for CMC arthritis. There are two possible reasons for this relationship. First, increased mechanical loading seems to occur at the CMC joint in obese adults. This is true even though the thumb is not a weight-bearing joint. Over time, increased load translates into wear and tear on the joint.
Second, patients with a higher body mass index also have elevated levels of lipids (fats), hormones, and insulin-like growth factor around the joint. Local biochemical changes from these hormones may speed up joint degeneration.
What does arthritis of the thumb feel like?
When the articular cartilage starts to wear off the joint surface, the joint may make a squeaking sound when moved. Doctors refer to this sound as crepitus. The joint often becomes stiff and begins to lose motion. Moving the thumb away from the palm may become difficult. This is referred to as a contracture.
Osteoarthritis may cause the CMC joint of the thumb to loosen and to bend back too far (hyperextension). If the middle thumb joint (MCP joint) becomes flexed and the furthest thumb joint also becomes hyperextended, the deformity is named a thumb swan neck deformity. A similar finger deformity sometimes occurs in people with finger arthritis.
How do doctors identify this problem?
Following the history, the doctor will examine your hand and possibly other joints in your body. The doctor will need to see how the motion of the CMC joint has been affected.
X-rays will be taken to see how much the joint is damaged. This test usually determines how bad the degenerative arthritis has become. How much articular cartilage remains in the joint can be estimated with the X-rays.
Using X-ray findings, the condition is classified as stage I, II, III, or IV, depending on the condition of the joint cartilage and the joint space. In Stage I, there are no obvious changes on X-ray. By stage IV, bone spurs, narrowed joint space, and even joint dislocation may be seen. Although X-rays are important, radiographic staging of the disease does not predict the severity of symptoms or guide treatment.
What can be done for CMC joint arthritis?
Treatment usually begins when the CMC joint first becomes painful. This may only occur with heavy use and may simply require mild anti-inflammatory medications, such as aspirin or ibuprofen. Reducing the activity, or changing from occupations that require heavy repetitive gripping with the hand, may be necessary to help control the symptoms.
Rehabilitation services, such as physical and occupational therapy, have a critical role in the nonoperative treatment plan for CMC joint arthritis. A primary goal is to help you learn how to control symptoms and maximize the health of your thumb. You’ll learn ways to calm pain and symptoms, which might include the use of rest, heat, or topical rubs. Adaptive devices to assist with household chores, self-care, or even on-the-job tasks may be recommended.
A brace or splint may also be prescribed to support the thumb. These devices are designed to help reduce pain, prevent deformity, or keep a thumb deformity from getting worse. A thumb stabilizer is a type of thumb splint that is often custom-made of heat-moldable plastic. It is designed to fit the forearm, wrist, and thumb. Patients with CMC joint arthritis usually only wear the splint at night and when the joint is flared up. It should also be worn to protect the thumb during heavy or repeated hand and thumb activities.
Range-of-motion and stretching exercises are prescribed to improve your thumb motion. Strengthening exercises for the arm and hand help steady the hand and protect the thumb joint from shock and stress. Strengthening improves joint stability and prevents deformity and/or dislocation. Your therapist will go over tips on how you can get your tasks done with less strain on the joint.
An injection of cortisone into the joint can give temporary relief. Cortisone is a very powerful anti-inflammatory medication. When injected into the joint itself, it can help relieve the pain. Pain relief is temporary and usually only lasts several weeks to months. There is a small risk of infection with any injection into the joint, and cortisone injections are no exception.
Studies do not support the use of cortisone injections alone. Although temporary pain relief is possible, there is no long-term improvement in hand function, joint stiffness, or tenderness. Steroid injection(s) combined with splinting has been shown more successful in patients during the early stages of CMC arthritis.
The surgical treatment for arthritis of the CMC joint includes several options. At one time, joint replacement with an artificial joint made with silicone was very popular. Problems with silicone implants in other parts of the body have led many surgeons to return to more traditional operations such as fusion and excision arthroplasty instead.
Newer artificial joints are being developed, and in the future we may see more surgeons using them. The best method to reduce pain and provide optimal function still remains uncertain. Research is underway to provide surgeons with evidence-based practice guidelines.
CMC Joint Fusion
A fusion, or arthrodesis, of any joint is designed to eliminate pain by allowing the bones that make up the joint to grow together, or fuse, into one solid bone. Fusions are used in many joints and were very common before the invention of artificial joints for the replacement of arthritic joints. Even today, joint fusions are still commonly used in many different joints for treating the pain of arthritis.
A fusion of the CMC joint of the thumb is done quite often in younger people who need a strong grip or pinch more than they need the fine motion of the thumb. People who use their hands for heavy work will probably prefer a fusion to an arthroplasty (described below).
Artifical Joint Replacement
Artificial joints are available for the CMC joint. These plastic or metal prostheses are used by some hand surgeons to replace the joint. The prosthesis acts as a spacer to fill the gap created when the arthritic surfaces of the two bones that make up the CMC joint are removed.
Long-term results using silicone and Zirconia implants have not been widely successful. Early wear (after two years) has been reported as a result of the shear and compressive forces across the implant. In some cases, the implant sinks down into the bone causing increased pain and weakness. Titanium implants have reportedly excellent results but not all studies have had equally good outcomes. More research is needed to reduce complications and extend the life of the implant.
Resectin (also called Excision) Arthroplast
The traditional operation for treating CMC joint arthritis is resection (excision) arthroplasty. This method has been used for many years and has withstood the test of time. Patients with severe symptoms in stage III or IV CMC arthritis who have failed nonsurgical treatment are good candidates for resection arthroplasty.
The purpose of resection arthroplasty is to remove the arthritic joint surfaces of the CMC joint and replace them with a cushion of material that will keep the bones separated. The trapezium bone is removed in a procedure called a trapeziectomy.
A rolled up piece of tendon is placed into the space created by removing the bone. This procedure is called a resection arthroplasty with ligament reconstruction and tendon interposition (LRTI). During the healing phase after surgery, this tendon turns into tough scar tissue that forms a flexible connection between the bones, similar to a joint. Sometimes the surgeon uses a silicone-based or metal implant or disc made of costochondral tissue instead of a rolled up tendon for the interpositional material. Costochondral allografts are plugs of tissue taken from the material between the breastbone and the ribs.
Resection arthroplasty with or without LRTI can be combined with a ligament reconstruction of the joint. Tendons in the area are used to create a ligament sling between the metacarpal bone of the thumb and the carpal bone of the index finger. This helps hold the thumb in place and keeps the space between the bones from collapsing.
Your surgeon decides whether to perform resection arthroplasty with or without tendon interposition and/or ligament reconstruction. Studies so far have not shown a biomechanical or clinical advantage to interposition. If there’s no evidence that this procedure improves pain, reduces stiffness, or increases pinch or grip strength, then it may fall out of favor. Surgeons will look for something more effective to achieve the intended treatment goals.
There can be complications with any surgical procedure. Infection, nerve injury, or continued pain can occur after surgery for CMC arthritis. When tendons are used as graft material for ligament reconstruction, problems can occur such as tendon rupture or tethering. Tethering means the tendon develops scarring or adhesions that bind it and keep it from gliding smoothly inside its sheath or outer covering.
With joint implants, there can be an inflammatory reaction, subsidence (the implant sinks down into the bone), dislocation, or other cystic changes.
What should I expect following treatment?
If you don’t need surgery, range-of-motion exercises for the thumb should be started as pain eases. Your therapist will work with you to obtain or create a special thumb splint (mentioned earlier) when needed. The program advances to include strength exercises for the thumb and fingers. Dexterity and fine motor exercises are used to get your hand and thumb moving smoothly. You’ll be given tips on keeping your symptoms controlled. You will probably progress to a home program within four to six weeks.
Your postoperative recovery and rehab program may depend on the type of surgery you had. For example, arthroscopy is much less invasive than open surgery and requires less time to recover. Your hand will be bandaged with a well-padded dressing and a thumb splint for support after arthroscopic, joint replacement, or ligament reconstructive surgery.
With fusion, there’s a high risk of nonunion so a cast is used to immobilize the joint for as much as three months. Often the thumb is fused in a functional position. The preferred position is a thumb key pinch. This means you can use the thumb to pinch and hold objects, but you won’t be able to open your hand flat. Getting your hand into a pocket will be more difficult, especially a pocket in tight pants.
Physical or occupational therapy sessions may be needed after surgery for up to eight weeks. The first few treatments are used to help control the pain and swelling after surgery. Some of the exercises you’ll begin to do are to help strengthen and stabilize the muscles around the thumb joint.
Other exercises are used to improve fine motor control and dexterity of your hand. You’ll be given tips on ways to do your activities while avoiding extra strain on the thumb joint.