THUMB ARTHRITIS
(CMC ARTHRITIS)
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related topics: wrist arthritis; broken thumb, finger arthritis, broken finger, broken wrist, nailbed injury
What is Thumb Arthritis?
The thumb, known as the opposable thumb, distinguishes humans from monkeys... among other things. The thumb is the stable foundation that other fingers lean on to perform daily functions. The thumb is also a highly mobile digit that enables so many fine motor activities. Its controlled by 9 different muscles!
However, our heavy reliance on this joint makes it subject to increased wear and tear over a lifetime, and its at increased risk for arthritis as we grow older.
Almost everyone will develop thumb arthritis if given enough time. About 1 in 3 women will prematurely develop thumb arthritis and about 1 in 8 men. This arthritis occurs at the CMC joint (aka carpo-metacarpal joint).
How is Thumb Arthitis diagnosed?
When people walk into the office with thumb arthritis, their thumbs can come in all shapes, sizes, and levels of severity. But its almost always pain that brings them in.
The pain is typically dull and aching, but will be sharp during vigorous activity (like with gripping or pinching).
When examining the thumb doctors see pain at the base of the thumb (the CMC joint), there is increased laxity (especially in the radioulnar plane), and often there is visable dorsal subluxation (the whole joint is shifted out of position). There is crunching within the joint (called a "grind test") which is due to synovitis (inflammation of the joint lining).
As the arthritis progresses, the joint actually becomes stiff, the laxity no longer exists because there are osteophytes (bone spikes) and other forms breakdown that blocks motion. Dorsal subluxation becomes more prominent while the thumb moves into a more adducted position, while MP hyperextension develops to compensate for loss of abduction. Inspect the STT joint as well because this is highly correlated with thumb arthritis.
X-rays are taken and can be used in conjunction with the physical exam to measure the severity of the arthritis. Stage 1 correlates with the laxity on exam (this is due to synovitis enlarging the joint space), then stage 2 shows mild cartilage narrowing and small osteophytes (<2mm), stage 3 shows worsening narrowing with osteophytes, and stage 4 includes adjacent joint arthritis (STT). The main thumb stabilizer is the anterior oblique ligament which prevents dorsal subluxation and it must become incompetent for the arthritis to progress.
How is Thumb Arthritis treated?
Treatment is often first with activity modification, splinting, anti-inflammatories, and steroid injections.
Full time splinting showed improvments in pain in 75% of people with early arthritis and 50% with late arthritis, and over 7 years one study found that about 70% of patients were able to avoid surgery with conservative treatment alone. This is important to remember because so many people have some level of thumb arthritis.
Surgery is a last resort for this condition which is so common. But continued pain and dysfuction can then be treated effectively with surgery. The most typical approach, which has shown significant success is the excision of the carpal bone (the trapezium) which is contributing significantly to the arthritic pain. Once this is bone gone, the pain should be better, however the thumb is now unstable. To stabilize the thumb a portion of the FCR (flexor carpi radialis) is taken and attached to the thumb metacarpal bone as well as interposed in the new space previously occupied by the trapezium.
Patients typically do well with this procedure.
What is the long term outcome?
The patients do well if treatment is approached in a stepwise manner, where nonsurgical treatment is first used, and then surgery is performed later if all else fails.
References
1. Van Heest AE, Kallemeier P. Thumb carpal metacarpal arthritis. JAAOS 2008; 16: 140-151. see article. review.
2. Doerschuk SH et al: Histopathology of the palmar beak ligament in trapeziometacarpal osteoarthritis. J Hand Surg 1999;24:496-504. see article. the amount of beak ligament degeneration corresponds to CMC arthritis. the dorsal-radial ligament is the restraint to posterior dislocation. its the strongest/thickest ligament.
3. Jónsson H et al. Hypermobility associated with osteoarthritis of the thumb base: A clinical and radiological subset of hand osteoarthritis. Ann Rheum Dis 1996;55:540-543. see article. major cause is hypermobility. cmc arthritis occurs by 15 yo in people with Ehlers-danlos.
4. Eaton RG, Littler JW: Ligament reconstruction for the painful thumb carpometacarpal joint. JBJS 1973;55:1655-1666. see article. classic x-ray classification system.
4. Brown GD III et al. Radiography and visual pathology of the osteoarthritic scaphotrapezio-trapezoidal joint, and its relationship to trapeziometacarpal osteoarthritis. J Hand Surg 2003;28:739-743. see article. x-rays underestimate OA severity seen intraop.
5. Swigart CR et al.. Splinting in the treatment of arthritis of the first carpometacarpal joint. J Hand Surg 1999;24:86-91. see article. 140 pts, splinting is effective with early stage cmc arthritis, 70% reduction pain.
6. Meenagh GK et al. A randomised controlled trial of intra-articular corticosteroid injection of the carpometacarpal joint of the thumb in osteoarthritis. Ann Rheum Dis 2004;63:1260-1263. see article. no effect of steroid injections.
7. Gerwin M et al. Ligament reconstruction basal joint arthroplasty without tendon interposition. CORR 1997;342:42-45. see article. surgical treatment 20 pts. randomized control trial trapezectomy +/- tendon interposition (APL, FCR or palmaris) had no effect on pain, function, prevention of metacarpal subsidence.
8. Kriegs-Au G et al. Ligament reconstruction with or without tendon interposition to treat primary thumb carpometacarpalosteoarthritis: A prospective randomized study. JBJS 2004;86:209-218. see article. another rct with 30 pts looking at need for tendon interposition. no difference in pain etc.