Introduction
The joint at the base of the thumb called the carpometacarpal (CMC) or trapeziometacarpal joint, is like a versatile joint. It can move in many different ways, but because of this flexibility, it can also wear down over time. Basal thumb arthritis is a common issue for which people often see hand doctors. To determine if someone has this problem, doctors usually just need to talk to them and do a checkup. Most people can get better with simple treatments, whether the condition is mild or severe.
What Is Basilar Thumb Arthritis?
Basal thumb arthritis is a form of osteoarthritis that impacts explicitly the joint at the base of the thumb. It is also known as carpometacarpal (CMC) joint arthritis or trapeziometacarpal (TMC) joint arthritis. Basal thumb arthritis becomes more common as people age, especially in postmenopausal women. It is about six times more likely to affect women than men. It is also associated with conditions like carpal tunnel syndrome, Ehler-Danlos syndrome, scaphotrapezial arthritis, and increased BMI.
What Causes Basal Thumb Arthritis?
Basilar thumb arthritis typically develops due to wear and tear on the joint over time.
Several factors contribute to the development of basal thumb arthritis;
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Aging - The natural aging process is a primary risk factor for basilar thumb arthritis. As people age, the cartilage in their joints can deteriorate, leading to arthritis.
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Ligamentous Laxity - Loose ligaments in the thumb joint, especially common in young women, are strongly linked to early joint wear and tear. This stress on an unstable joint can lead to damage visible on X-rays after age 50.
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Previous Thumb Injury - Prior thumb injuries increase the risk of developing arthritis in the base joint. Certain fractures, like Rolando or Bennett fractures, can result in issues if they do not heal correctly.
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Inflammatory Arthritis - Conditions like rheumatoid arthritis, which cause joint inflammation, can predispose individuals to basal thumb arthritis. This joint is frequently affected in rheumatoid arthritis patients.
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Idiopathic Cases - In many instances, the exact cause of basal thumb arthritis remains unclear, and it seems to develop spontaneously without a specific trigger.
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Overuse - Activities that involve repetitive thumb movements or excessive use of the thumb joint, such as gripping, pinching, or heavy lifting, can contribute to the development of arthritis.
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Hormonal Changes - Some research suggests that hormonal changes, such as those that occur during menopause, may influence the development of thumb arthritis in women.
What Are the Symptoms of Basal Thumb Arthritis?
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Pain - Patients typically feel pain in the base of the thumb, which can also spread to the fleshy part of the palm (thenar eminence) and the joint where the thumb connects to the hand (metacarpophalangeal joint). This pain is often linked to activities, especially when using the thumb forcefully, like gripping objects, opening jars, turning doorknobs, or writing. As the arthritis gets worse, the pain might become constant.
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Weakness and Limited Motion - People with basal thumb arthritis often experience weakness in the thumb and may find it difficult to move it properly. These symptoms are the body's way of protecting the damaged joint and preventing further harm.
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Thumb Problems - In advanced stages, when the joint becomes unstable, patients might notice that they cannot move their thumb away from their index finger, making it hard to grasp large objects. This can lead to a thumb deformity known as a swan-neck deformity, where the thumb bends unusually.
How Is Basilar Thumb Arthritis Diagnosed?
Typically, a thorough history and clinical examination are sufficient to confirm the diagnosis of basal thumb arthritis. In addition, the following may be done to diagnose this condition.
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X-rays can help assess the disease's stage and educate the patient about their condition.
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If there are any sensory problems related to nerves, nerve conduction studies may be recommended.
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In advanced cases, the base of the thumb looks more prominent on the back and towards the side of the hand. This can be due to joint problems, inflammation, and the formation of bone spurs.
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A doctor can find specific tenderness by pressing on the affected joint with the thumb and fingers. If there is a grinding or crackling sensation when moving the thumb, it suggests damage to the joint cartilage.
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Provocative Tests - These are special tests that a hand specialist may perform. One test involves rotating the thumb base while pressing down gently (the "grind" test). If it causes pain, it suggests degenerative disease. Another test consists of rotating the thumb base while pulling gently (the "distraction" or "torque" test). A positive result suggests inflammation in the joint capsule.
Based on the radiographic changes, basal thumb arthritis can be classified into the following stages:
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Stage I (Pre-arthritis) - There is a bit more space in the joint than usual, but it is not arthritis yet.
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Stage II - The joint starts narrowing, and there are small bone spurs (less than 2mm).
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Stage III - The joint narrows significantly, with larger bone spurs (over 2mm).
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Stage IV (Pantrapezial Arthritis) - This is the most advanced stage, where the thumb base joint is affected and the joint that connects the wrist bone to a thumb bone (known as the STT joint).
How Is Basilar Thumb Arthritis Treated?
Conservative Treatment
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Adjusting how the thumb is used, like avoiding forceful pinching or using the other hand more, can help.
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Immobilizing the thumb base with a special splint, especially a custom-made one, can provide relief. Initially, it is worn continuously for 3 to 4 weeks, along with anti-inflammatory drugs. Then, it can be used during the day and gradually stopped over a month or used when the thumb is bothersome.
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Non-steroidal anti-inflammatory drugs can help with the symptoms.
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Doing specific hand exercises can strengthen thumb muscles.
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Corticosteroid Injections can be considered if conservative treatments do not work. They can relieve pain for varying periods but have diminishing effects over time.
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Some studies explore chondroprotective supplements like glucosamine and chondroitin sulfate to protect cartilage, but their effectiveness is debated.
Surgical Treatment
Surgery may be recommended if other treatments fail and the patient continues to experience pain and loss of function. Different surgical procedures are available, ranging from soft tissue treatments in early disease stages to removing the trapezium bone in advanced cases.
The choice of surgery depends on the patient's symptoms and needs.
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Arthroplasty - The removal of damaged joint surfaces and replacement with an artificial joint or spacer.
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Fusion (Arthrodesis) - The fusion of the thumb joint to eliminate pain and provide stability.
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Tendon Transfer - The repositioning of tendons to improve thumb function.
Conclusion
Basilar thumb arthritis is a common problem in the joint at the bottom of the thumb. Although it can make the hands hurt and stiff, limiting their movement, there are different treatment methods, from conservative measures to surgical interventions.
