The carpometacarpal (CMC) joint of the thumb is the second most common site for osteoarthritis of the hand (1,2,3). The thumb CMC joint consists of the articulation between the base of the thumb metacarpal and the trapezium forming a biconcave-convex saddle joint, allowing the movement of the thumb metacarpal in 3 different planes including abduction-adduction, flexion-extension, and axial rotation (4). The CMC joint along with the trapezium-second metacarpal and scaphotrapeziotrapezoid (STT) joint is stabilized by a total of 16 ligamentous structures, creating a tension band that prevents subluxation from cantilever forces experienced during pinch (1,2,4). Of these numerous ligaments, failure of the anterior oblique “beak” ligament plays a significant role in the development of CMC osteoarthritis (1,5). Laxity of the beak ligament results in uneven stress loads in the CMC joint during pinch and grasp leading to the development of synovitis and ultimately to articular wear, cartilage loss, and development of osteoarthritis with osteophyte formation (1,2,3,5). The thumb metacarpal base eventually subluxates dorsally and radially resulting in adduction of the metacarpal diaphysis and compensatory hyperextension of the first metacarpophalangeal (MP) joint (2) (Fig. 26A-1).

Patients typically present with a chief complaint of pain at the thumb base, usually exacerbated by gripping or pinching maneuvers, without history of local trauma (2,4,6). Physical exam will reveal tenderness overlying the CMC joint and, in more advanced stages, a positive grind test and crepitation over the joint. Differential diagnosis includes de Quervain’s tenosynovitis, tendonitis
of the flexor carpi radialis (FCR) or the extensor carpi radialis longus and brevis, STT arthritis, and scaphoid pathology (2,4,6). Radiologic findings confirm the diagnosis and also determine the stage of the disease process based on 2 available classification systems, one described by Dell et al. (7) and the other by Eaton and Glickel (8) (Table 26A-1). The Dell system uses the degree of thumb metacarpal subluxation as a staging tool, while the Eaton system uses the changes in the joint space and the size of osteophytes forming in the joint as staging criteria. Although the Eaton classification system offers only moderate interobserver agreement and does not correlate with patient symptom severity, it remains the most widely used reference to guide treatment options (9).

Treatment options for the management of CMC arthritis vary greatly depending on the stage of the disease, symptoms, level of patient functional impairment, and surgeon preference (1,2,6,10). Furthermore, the increasing popularity of minimally invasive arthroscopic procedures as well as the development of new implant materials for joint reconstruction have created new trends in the management algorithm (1,2,6,11). A recent review of several studies evaluating different surgical and nonsurgical treatment strategies in patients with CMC arthritis
concluded that patients with Eaton grade I CMC arthritis are more likely to benefit from nonoperative interventions while the choice of treatment for patients with grade II to grade IV arthritis will depend on severity of symptoms and functional demands with no one surgical option proven to be superior to another (12).

Management of mild to moderate CMC arthritis starts with activity modification, nonsteroidal anti-inflammatory drugs, and the use of either prefabricated or custom-made opponens splints (6,10,13). These treatment options decrease the friction at the inflamed joint and improve but can be seen by patients as overly restrictive. Injection of the joint with either corticosteroids or hyaluronic acid (off-label) preparations is the next available option (1,2,6,10) and is usually met with at least temporary relief. Failure to adequately control symptoms with nonoperative management and disease progression are indications for surgical intervention (1,2,10). Commonly performed procedures for the management of mild to moderate CMC arthritis include the extension-abduction osteotomy, CMC joint arthroscopy with debridement, synovectomy and possible capsulodesis, and the partial trapeziectomy with or without interposition (1,4,6,11).

Basal abduction osteotomy of the first metacarpal for the treatment of CMC arthritis was initially described several years ago as an alternative to more invasive procedures as total trapeziectomy or CMC joint fusion (14). The osteotomy is designed to address the radial subluxation of the first metacarpal base and the adduction deformity of the first metacarpal diaphysis. It was reported to restore the thumb grasp power as well as the ability of the hand to grasp larger objects (14). The procedure entails a resection of a wedge of bone from the radial aspect of the first metacarpal base and then abducting the distal diaphysis segment for closure of the osseous defect (Fig. 26A-2) (14). The efficacy of the abduction osteotomy is a result of the biomechanical effect it has in the CMC joint, transferring the force during thumb pinch and grasp to the dorsal area of the CMC joint, which is usually less affected (15,16). The thumb is placed in a more abducted and extended position, changing the distribution of stress to a more vertical vector across the joint, decreasing the tendency for thumb subluxation, and thus reducing the shearing forces causing the cartilage
degeneration (1,15). The main advantage of the procedure is the fact that it is extra-articular and therefore preserving all other surgical options if the disease process continues to progress to more advanced stages (1,14,15,16).