Intra-Articular Injection of the Carpometacarpal Joint of the Thumb

Indications and Clinical Considerations

The carpometacarpal joint is susceptible to developing arthritis from a variety of conditions that have the ability to damage the joint cartilage. Osteoarthritis of the joint is the most common form of arthritis that results in carpometacarpal joint pain. Osteoarthritis is more common in females. However, rheumatoid arthritis, posttraumatic arthritis, and psoriatic arthritis are also common causes of carpometacarpal pain secondary to arthritis. Less common causes of arthritis-induced carpometacarpal pain include the collagen vascular diseases, infection, and Lyme disease. Acute infectious arthritis usually is accompanied by significant systemic symptoms, including fever and malaise, and should easily be recognized by the astute clinician and treated appropriately with culture and antibiotics rather than injection therapy. The collagen vascular diseases generally manifest as a polyarthropathy rather than a monoarthropathy limited to the carpometacarpal joint, although carpometacarpal pain secondary to collagen vascular disease responds exceedingly well to the intra-articular injection technique described later. The clinician should be aware that the carpometacarpal joint of the thumb is susceptible to trauma, and occult ligamentous injuries, dislocations, and fractures should be included in the differential diagnosis of patients with persistent pain in this joint after trauma ( Figs. 85.1 and 85.2 ).

The majority of patients with carpometacarpal pain secondary to osteoarthritis and posttraumatic arthritis report pain localized to the base of the thumb. Activity, especially with pinching and gripping motions, exacerbates the pain; rest and heat provide some relief. The pain is constant and is characterized as aching and may interfere with sleep. Some patients note a grating or “popping” sensation with use of the joint, and crepitus may be present on physical examination. The Watson stress test is positive in patients with inflammation and arthritis of the carpometacarpal joint of the thumb. This test is performed by having the patient place the dorsum of the hand against a table with the fingers fully extended and then pushing the thumb back toward the table ( Fig. 85.3 ). The test is positive if the patient’s pain is reproduced.

In addition to the previously mentioned pain, patients with arthritis of the carpometacarpal joint often experience a gradual decrease in functional ability, with decreasing pinch and grip strength, making everyday tasks such as using a pencil or opening a jar quite difficult. With continued disuse, muscle wasting may occur and an adhesive capsulitis with subsequent ankylosis may develop.

Plain radiographs are indicated for all patients with carpometacarpal pain. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging and/or ultrasound imaging of the carpometacarpal joint is indicated if joint instability is suspected.

Clinically Relevant Anatomy

The carpometacarpal joint is a synovial, saddle-shaped joint that serves as the articulation between the trapezium and the base of the first metacarpal ( Fig. 85.4 ). The joint’s primary function is to optimize the pinch function of the hand. It allows flexion, extension, abduction, adduction, and a small amount of rotation. The joint is lined with synovium, and the resultant synovial space allows intra-articular injection. The entire joint is covered by a relatively weak capsule that surrounds the entire joint and is susceptible to trauma if the joint is subluxed. The carpometacarpal joint may also become inflamed as a result of direct trauma or overuse of the joint.