Editorial Comment: Symposium: Thumb Carpometacarpal Arthritis
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- Ladd, A.L. Clin Orthop Relat Res (2014) 472: 1093. doi:10.1007/s11999-013-3348-1
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The basilar joint — that very base of power, precision, and human superiority — is prone to osteoarthritis, and is the most common site of reconstructive hand surgery. Surgeons currently favor some form of trapeziectomy over hemitrapeziectomy or implant arthroplasty for a variety of reasons. The surgeon often chooses the method of trapeziectomy that the “master” taught or works well in his or her hands. Indeed, the current evidence suggests that trapeziectomy (with or without reconstruction) works if pain relief is the primary endpoint for those with advanced thumb carpometacarpal (CMC) arthritis.
If the current literature is any indication, controversy surrounds basilar thumb arthritis. No one comfortably agrees on what to call this troublesome little joint: “trapeziometacarpal joint” is most accurate, but “basal joint” has such a nice ring to it. However, “CMC joint” likely has the most followers given its simple shorthand name. Then again, others favor “TMC” for similar reasons. Controversy accompanies unanswered questions, and this symposium begins to address several of these unknowns. We will investigate basic questions: Who really gets CMC arthritis? How good are we at diagnosing it? We also delve into the more complex: How does the CMC joint actually move with functional activity? Do ligaments, hormones, or abnormal motion cause the joint to wear out? Why do so many different reconstructive procedures with trapeziectomy and no implant “work” — even if we do not reconstruct the anatomic ligaments? Why have, to date, implant failure rates been comparatively high? Finally, some questions border on the philosophical: Where does this joint — a defining characteristic of what it means to be human — fit on the evolutionary scale?
This symposium on CMC arthritis supplies insight into commonly held beliefs with a blend of history, basic science, and clinical perspectives. We have printed the first English translation of Paul Robert’s original 1936 article on the importance of the pronated thumb x-ray view . It is truly a gem — although absent of actual x-rays.
From an evolutionary standpoint, the thumb forms last, recesses in length, and diverges from the adjacent digits. It may disappear in a few thousand millennia, but for now, most of us will embrace its elegance and beleaguered existence. More complex than the “saddle” biconcave-convex joint we have been taught; the thumb may be evolving into a simplified ball-and-socket joint — a common pattern of severe arthritis. Although ball-and-socket implants have not fared well to date, this favored shape of progressive arthritis and evolution warrants further study. In the meantime, kinematic studies [1, 2] indicated that the micro-motion of the metacarpal upon the trapezium can be quantified in motion arcs of flexion-extension, adduction-abduction, and rotation. The movement patterns and loads are eccentric and specific, especially with volar and ulnar preference. A pilot kinematic study  indicated the effect of an adducted, arthritic thumb on compensatory movements of the upper limb, providing measurable parameters with implications for rehabilitation and functional capacity.
This symposium both supports and challenges prevailing thoughts on how CMC arthritis occurs. Volar, ulnar preferential wear of the trapezium is a commonly documented site of arthritis, and the anterior oblique ligament holds court at this very site. The anterior oblique ligament is often reported to be an important contributor to disease development, and has hormone receptors including relaxin, suggesting a link to laxity. Recent reports suggest the sturdier dorsal ligaments may be more important as stabilizers and determinants of proprioception. Arthroscopic treatment of the CMC joint follows the trend of larger joint arthroscopy in offering minimally invasive therapeutic options. Whether partial arthroscopic trapeziectomy or complete trapeziectomy with specific ligament reconstruction (or any at all) have advantages over each other remains to be determined with future studies. Historically prescribed by tradition and training, both nonoperative and postoperative therapy remains an area for future systematic approach in developing accepted and rigorous protocols.