The first carpometacarpal or trapeziometacarpal joint is a synovium-lined saddle-type joint formed by the articular surface of the trapezium proximally and the base of the first metacarpal (thumb) distally (Fig. 75.1). The primary function of the first carpometacarpal joint is to aid in orientation of the thumb to allow pinching movements as well as flexion and extension in the plane of the palm of the hand, abduction and adduction in a plane at right angles to the palm, circumduction, and opposition (Fig. 75.2). The joint’s articular cartilage is susceptible to damage, which, if left untreated, will result in arthritis with its associated pain and functional disability. Osteoarthritis of the joint is the most common form of arthritis that results in first carpometacarpal joint pain and functional disability, with rheumatoid arthritis, posttraumatic arthritis, and crystal arthropathy also causing arthritis of the first carpometacarpal joint. Less common causes of arthritisinduced first carpometacarpal joint pain include the collagen vascular diseases, infection, villonodular synovitis, and Lyme disease. Acute infectious arthritis of the first carpometacarpal joint is best treated with early diagnosis, with culture and sensitivity of the synovial fluid, and with prompt initiation of antibiotic therapy. The collagen vascular diseases generally manifest as a polyarthropathy rather than a monoarthropathy limited to the first carpometacarpal joint, although first carpometacarpal pain secondary to the collagen vascular diseases responds exceedingly well to ultrasound-guided intra-articular injection of the first carpometacarpal joint. Interestingly, osteoarthritis of the thumb occurs over twenty times more frequently in elderly females when compared with elderly males. This is thought to be due to sexual dimorphism in the shape of the joint with the female joint having a significantly smaller trapezial articular surface when compared with males of the same age.

Patients with first carpometacarpal joint pain secondary to arthritis, gout, synovitis, and collagen vascular disease-related joint pain complain of pain that is localized to the base of the thumb. Activity, including pinching and gripping motions, makes the pain worse, with rest and heat providing some relief. The pain is constant and characterized as aching in nature. Sleep disturbance is common with awakening when patients roll over onto the affected upper extremity. Some patients complain of a grating, catching, or popping sensation with range of motion of the joint, and crepitus may be appreciated on physical examination. Watson stress test is positive in patients who suffer from inflammation and arthritis of the carpometacarpal joint of the thumb. Watson 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. 75.3). The test is positive if the patient’s pain is reproduced.

Functional disability often accompanies the pain of many pathologic conditions of the first carpometacarpal joint. Patients will often notice increasing difficulty in performing their activities of daily living and tasks that require gripping or pinching objects such as writing with a pen or pencil or opening a jar. If the pathologic process responsible for the first carpometacarpal pain is not adequately treated, the patient’s functional disability may worsen, and muscle wasting and ultimately a frozen first carpometacarpal joint may occur.

Plain radiographs are indicated in all patients who present with first carpometacarpal joint pain (Fig. 75.4). Based on the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging or ultrasound of the first carpometacarpal joint is indicated if fracture, effusion, tendinopathy, crystal arthropathy, joint mice, synovitis, bursitis, or ligamentous injury is suspected.

The first carpometacarpal or trapeziometacarpal joint is a synovial-lined saddle-type joint formed by the articular surface of the trapezium proximally and the base of the first metacarpal (thumb) distally (see Fig. 75.1). The primary function of the first carpometacarpal joint is to aid in orientation of the thumb to allow pinching movements as well as flexion and extension in the plane of the palm of the hand, abduction and


adduction in a plane at right angles to the palm, circumduction, and opposition. The joint is lined with synovium, and the ample synovial space allows for intra-articular placement of needles for injection and aspiration. Due to the extensive and diverse range of motion of the first carpometacarpal joint combined with a relatively weak and slack joint capsule, the joint is especially susceptible to trauma including subluxation and fractures of the base of the metacarpal through the articular surface, which can result in the development of arthritis (Fig. 75.5). The joint is also susceptible to overuse and misuse with resultant inflammation and arthritis. Much of the joints strength is derived from the three intracapsular and two extracapsular ligaments and the surrounding tendons.