The anatomy of the thumb metacarpal (TM) joint is extremely complex and has been well studied.³,¹⁹ The deep anterior oblique ligament (dAOL) (“beak ligament”) is the primary stabilizer of the TM joint.¹⁰,¹¹ More recently, 16 ligaments have been described that stabilize the TM joint. Seven of these ligaments, including the superficial anterior oblique ligament (sAOL), dAOL, dorsoradial, posterior oblique, ulnar collateral, intermetacarpal, and dorsal intermetacarpal, directly stabilize the TM joint. The other 9 ligaments indirectly stabilize the TM joint by directly stabilizing the trapezium.³,¹⁸

The TM joint is the most complex joint in the hand.⁸ It is a biconcave-convex saddle joint with minimal bony constraints. This joint allows flexion-extension, abduction-adduction, and pronation-supination of the thumb ray.¹⁴ For optimal treatment outcomes with joint replacement, normal kinematics—six degrees of freedom—should be restored as closely as possible.

Degeneration of the AOL of the TM joint has been linked to the development of osteoarthritis.

Pathologic laxity, abnormal translation of the metacarpal on the trapezium, and generation of abnormally high shear forces within the TM joint, especially on the palmar aspect of the joint during pinch and grip motions, occur when the AOL becomes incompetent.

The base of the metacarpal tends to sublux dorsally with AOL detachment, emphasizing the importance of the AOL. In advanced osteoarthritis, adduction and flexion contractures tend to develop, producing further functional impairment and joint overload.

The vast number of described operations to treat osteoarthritis of the TM joint demonstrates the lack of consensus among treating surgeons as to the best way to approach this disorder. This chapter details the role of resurfacing and implant arthroplasty for the treatment of osteoarthritis of the TM joint.

Various materials, techniques, and prostheses have been used in the past. Hemiarthroplasty and total joint arthroplasty of the TM joint have largely failed, with mediocre long-term results compared with soft tissue arthroplasty.¹,²,⁷,⁹,¹⁷,²³ However, the appeal of a replacement may lie with quicker recovery, more normal kinematics, immediate stability, and the avoidance of metacarpal subsidence.

Obviously, the perils of prosthetic alternatives revolve around durability, survivability, and complication rate. Joint resurfacing with the Artelon implant (Small Bone Innovations, Inc., Morrisville, PA) was touted to have the most potential, in terms of a biologic resurfacing. This procedure avoids the use of a semiconstrained device—which has been associated with trapezial component loosening and failure, but long-term follow-up has been characterized by a significant complication rate and poor satisfaction.

Arthritis of the TM joint often presents with pain at the base of the thumb during pinch and grip (stressful activities for the TM joint). Women are 10 to 15 times more likely than men to develop this disorder. Asian and Caucasian populations have an increased prevalence as well.

Common offending activities include brushing teeth, opening a jar, picking up a book, or turning a key. All of these activities involve increasing the breadth of grasp or forceful lateral pinch. Usually, the pain is localized at the base of the thumb on the dorsal or volar radial aspect of the thenar cone. Patients often feel the joint slipping or subluxing radially.

Other causes of pain in the hand should be evaluated (see Differential Diagnosis list) as well. This is important because any concomitant disease, such as a trigger thumb, may hamper the postoperative therapy regimen and negatively affect the patient’s final outcome.

The treating physician should also keep the diagnosis of carpal tunnel syndrome in mind, as it coexists in about 44% of patients with TM joint arthritis. Furthermore, the postoperative swelling from a basal joint arthroplasty may exacerbate even mild cases of carpal tunnel syndrome.

The Allen test should be performed on every patient who is undergoing surgery for basal joint arthroplasty, as the radial artery will be near or in the operative field and may
need to be mobilized depending on the exact procedure performed. Any injury to the radial artery should be repaired immediately.

The stability of the metacarpophalangeal (MCP) joint of the thumb is also critical, as this is a source of postoperative stress on the reconstructed beak ligament from either ligament reconstruction or suspensionplasty procedures.

Methods for examining the carpometacarpal (CMC) joint of the thumb include the following:

Imaging of the TM joint includes a true anteroposterior (AP) view of the TM joint (called a Robert view or pronated AP), lateral, and posteroanterior 30-degree oblique stress view (with thumb tips pressing against each other).

The most common staging system was originally described by Eaton and Littler¹¹,¹²: stage 1 shows slight widening of the joint, possibly from synovitis; stage 2 demonstrates some joint space narrowing and osteophytes smaller than 2 mm; stage 3, osteophytes larger than 2 mm; and stage 4 disease, scaphotrapezial joint space involvement along with TM joint narrowing.

The senior author of this chapter has described a “fifth stage” in which the disease process is pantrapezial and there is TM, scaphotrapezial, and scaphotrapezoidal joint degeneration. Scaphotrapezoidal arthritis can be a source of continued pain and this joint should be evaluated intraoperatively in every patient because, unfortunately, preoperative radiographs are only 44% sensitive and 86% specific for diagnosing arthritis at this joint.²⁶

Initial management of TM joint arthritis is nonoperative and includes anti-inflammatory medication, thenar cone muscle isometric strengthening exercises, hand- or forearm-based thumb spica splint immobilization, steroid injections, and activity modification.

These measures may not alleviate any or all of the patient’s symptoms, but they may help enough to provide temporary relief, allowing the patient ample time to educate himself or herself and to contemplate the treatment alternatives.

The time afforded by the nonoperative measures may also allow the patient to schedule the operation at a more convenient time.