Thursday, November 19, 2015
Thumb Carpometacarpal Joint Osteoarthritis
By: Julian Carlo, MD, surgeon at The Brookwood Orthopedic Sports Medicine Institute
The thumb is an essential part of our anatomy and one of humans’ most important anatomic features. The thumb plays a vital role in most hand functions through a combination of flexibility and strength. The carpometacarpal (CMC) joint of the thumb is integral in providing the thumb the flexibility to position itself in space. The joint’s complex saddle-like morphology allows it to abduct, oppose, and rotate the thumb into numerous positions necessary for the hand to deftly interact with the world and its objects. The large thenar muscles can apply forces delicate enough for a precision pinch or strong enough for a power grip. Given its importance, it should be no surprise that without the thumb, the hand loses about 50% of its function.
Although the CMC joint seems elegantly designed, the freedom of mobility and tremendous demands placed on the thumb can predispose it to developing osteoarthritis. The biomechanical design of the thumb concentrates forces on the CMC joint by a factor of 12 times the original applied force. In addition, the laxity essential for allowing wide range of motion often translates into instability, which can increase joint contact forces and accelerate cartilage wear. As a result, the thumb CMC joint is one of the joints most susceptible to osteoarthritis. Up to one in four post-menopausal women may be affected.
Most patients present with complaints of activity-related pain, aching, or burning at the base of the thumb that results in functional disability. Activities that are particularly painful include a forceful pinch (such as when holding dishes, turning a key, or pulling up a pair of pants), the positioning of the joint at extremes of motion (such as reaching across to the small finger), and a forceful grip (such as opening a jar). On exam, reproduction of symptoms by palpation at the CMC joint or an axial “grind” test are suggestive of the diagnosis. Radiographs show findings typical of arthritis, including joint space narrowing, sclerosis, erosion, loose bodies, and osteophytes.
When I see patients with this condition, I feel it is important to lay out the goals of care: reduction of pain and improvement of function. Patients should embark on a trial of nonoperative treatment because many people can improve without surgery. Activity modification, use of assistive devices, and splinting the thumb CMC joint are a good place to start. Nonsteroidal anti-inflammatories or acetaminophen can also help improve symptoms. Injecting the CMC joint with corticosteroid or a hyaluronidase can also provide relief that may help delay or eliminate the need for surgical treatments.
When should a patient be referred to a hand surgeon? It is appropriate for primary care physicians or other healthcare providers to diagnose and initiate care for this common condition as described above. Patients can be referred if they are failing nonoperative management and surgery is anticipated. Referral can also be initiated at any time in treatment, if the diagnosis is uncertain, or if more specialized treatment such as a CMC joint injection is desired.
When nonoperative management has failed to adequately improve the overall condition, it is reasonable to consider surgery. Many patients are unaware that a surgery can help their condition. There are a number of outpatient surgical procedures that reliably improve pain and function. The most common surgeries include excision of the trapezium with or without a reconstruction of ligaments that stabilize the thumb. In young patients a fusion of the joint may be indicated. Other procedures that preserve the trapezium or replace the joint have been devised. The surgeon will decide which operation is best for a patient’s particular presentation. Postoperatively patients require a short period of immobilization and most benefit from hand therapy to regain motion and strength. Improvement in pain, strength, and function can reliably be achieved, and there is generally a high satisfaction rate after surgery.
Julian Carlo, MD is an orthopedic hand and upper extremity surgeon at The Brookwood Orthopedic Sports Medicine Institute. For questions, appointments, or referrals call (205) 877-BONE (2663).