One of the most common areas for the development of osteoarthritis (OA) is the base of the thumb.
This joint is called the carpo-metacarpophalangeal joint. It consists of a bone in the wrist called the trapezium that forms a shallow groove or saddle in which the base of the metacarpal bone (thumb bone) rests. Each of these bones is covered with a layer of hyaline cartilage.
This joint is particularly prone to developing OA because of its extreme mobility (one of the most mobile joints in the body) as well as the forces it must withstand during the course of a day's activity.
It has been estimated that the force multiplier effect is about 12 times the actual force applied by the thumb. Over a long period of time this causes the cartilage to undergo wear and tear. This wear and tear is complicated by the presence of local inflammation which accelerates the destruction of cartilage.
Prior injuries to the joint or to the ligaments supporting the joint also can make it more prone to developing OA.
OA at this site is more common in women than men. (Callinan N. Arthritis Self-Management.2011; 12: 8-15)
The diagnosis is made clinically and supported by x-rays. There is poor correlation between symptoms and extent of disease.
While early management consisting of medication, hand therapy, joint protection and exercises can be of assistance, the course of the disease in this location is inexorably downhill.
Thermal modalities such as ice or heat may help. One method of delivering heat is a paraffin (hot wax) bath.
Hand stretching and strengthening exercises under the supervision of a hand therapist may offer temporary respite.
Splints can also offer a modicum of relief.
Non-steroidal anti-inflammatory drugs (NSAIDS) or oral analgesics can help in milder cases. However, their effectiveness is limited by their potential toxicities. Topical NSAIDS may be helpful and cause less overall toxicity.
Patients may require injections with either corticosteroids or viscosupplements. These injections should be done using ultrasound guidance and be followed by at least three days of splinting to rest the joint. No more than three corticosteroid injections should be administered per calendar year.
Arthroscopic debridement followed by viscosupplementation has been demonstrated to be of some benefit. (Wei N, et al. J Clin Rheum. 2002; 8: 125-129).
End stage disease will require surgery.
A hand surgeon will use a tendon from the forearm to act as a spacer inside the joint. Less commonly, the joint may require fusion.
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