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C MC ARTHRITIS IS a common condition, often referred to as basal joint arthritis or arthritis at the base of the thumb. It affects people as they grow older and can affect either the dominant or the nondominant hand. It is much more common in women. Statistically, women proceed to surgical treatment approximately 40 times more frequently than men. The etiology of CMC arthritis is due to pinching between the thumb, index and long fingers. When someone pinches and applies 5 pounds of grip strength between their thumb and index finger — to write with a pen, for example — the joint at the base of the thumb, or CMC joint, sees 60 pounds of pressure, or approximately 12 times as much as is applied at the point of contact. One reason it is believed that women get this much more frequently than men is because most women do not have a stout anterior oblique ligament at the base of their thumb. The thumb subluxes or pops in and out of the joint at its base, and over time this subluxation takes its toll on the articular surface and causes arthritis. The initial treatment of CMC arthritis involves splinting and activity modification. Several different splints can be utilized both day and night to provide some relief. A daytime splint is usually softer and more pliable but supports the base of the thumb while allowing some mobility. At night, a longer, firmer splint that holds the thumb and wrist in a neutral position is commonly utilized. Activity modification consists of learning how to hold or utilize objects using a power-grip maneuver instead of a pinching maneuver. Think of how one would hold an old-time metal potato peeler — it involves pinch, which stresses the base of the thumb. Both newer kitchen tools as well as gardening tools have larger, fatter, well-padded handles that force one to hold them more in the hand and use a grip position that does not stress the thumb. Cortisone injections are often very helpful as well. However, when the joint becomes arthritic, it is more difficult to suc- cessfully inject medicine into the joint. The last option for treatment is surgery, and numerous surgical procedures — each varies on which tendon is utilized for the reconstruction — have been designed and implemented to treat this condition. The arthritic trapezium bone is usually totally removed, and the tendon is either used as spacer or is drilled through bone to suspend the thumb in its normal anatomical place. Numerous implants, made of different material such as silicone or titanium, have also been utilized to perform joint replacement surgery in this area. They have been less successful and plagued by more complications than the use of a tendon, which is known as CMC arthroplasty. The results of CMC arthroplasty are very predictable in terms of pain relief. People generally return to a very high level of function and have 85–90 percent of their grip and pinch strength return within a year. Other associated problems with CMC arthritis involve the next joint, known as the metacarpophalangeal joint, which can hyperextend and cause the thumb to go into Z-deformity. This condition is often treated concurrently with CMC arthroplasty by either pinning the joint, advancing the ligament, or in extreme cases, fusing the joint. Overall, most patients return to a very high level of activity following surgical intervention and are happy with the outcomes. Dr. Dietrich is a board-certified orthopedic surgeon, specializing in surgery of the hand and upper extremities. His areas of interest include wrist disorders, fracture care, peripheral nerve surgery and trauma. He practices at the Crystal Clinic's Akron, Ohio, office at 3925 Embassy Parkway. ■ Pain at the Base of the Thumb, By John W. Dietrich, MD a Common Condition ++++++++++++++++++++ + +++ + +++ ++++++++++++++++++++ ORTHOPEDICS ❯ 1 8 | Cleveland/Akron/Canton MD NEWS ■ M D N E W S . CO M ■ J U LY/AU G U S T 2 0 1 5