The thumb carpometacarpal joint: anatomy, hormones, and biomechanics.

Although there are many surgical options to treat thumb carpometacarpal (CMC) arthritis, a precise etiology for this common disorder remains obscure. To better understand the physiology of the thumb CMC joint and treat pathology, it is helpful to examine the biomechanics, hormonal influences, and available surgical treatment options, along with the evolutionary roots of the thumb; its form and function, its functional demands; and the role of supporting ligaments based on their location, stability, and ultrastructure. It is important to appreciate the micromotion of a saddle joint and the role that sex, age, and reproductive hormones play in influencing laxity and joint disease. Minimally invasive surgery is now challenging prevailing treatment principles of ligament reconstruction and plays a role in thumb CMC joint procedures.