CMC arthroplasty is surgery to treat arthritis at the base of the thumb, where the thumb’s first bone meets a small wrist bone called the trapezium. This joint, known as the carpometacarpal (CMC) joint, is one of the most common sites for hand arthritis, and arthroplasty aims to eliminate the bone-on-bone grinding that causes pain during everyday tasks like opening jars, turning keys, or pinching. Several surgical techniques fall under the CMC arthroplasty umbrella, but they all share the same goal: restoring a pain-free, functional thumb.
Why the Thumb CMC Joint Is Vulnerable
The thumb CMC joint has a unique saddle shape that allows it to move in three planes using just two axes of rotation. This is what gives humans the ability to oppose the thumb against the other fingers for gripping and pinching. No other finger joint has this range of motion, and no other finger joint takes on quite the same mechanical load.
That combination of flexibility and heavy use makes the CMC joint prone to wearing out over time. The cartilage lining the joint gradually breaks down, leading to osteoarthritis. Doctors classify the severity using a four-stage system. Stage I shows subtle widening of the joint space before true arthritis sets in. Stage II involves mild joint narrowing with small bone spurs under 2 mm. Stage III shows significant narrowing with larger spurs. Stage IV means the arthritis has spread to neighboring wrist joints. Surgery typically enters the conversation when splinting, anti-inflammatory medications, and steroid injections are no longer controlling pain, usually at stage II or beyond.
Types of CMC Arthroplasty
Trapeziectomy With Tendon Reconstruction (LRTI)
The most widely performed version is called ligament reconstruction and tendon interposition, or LRTI. The surgeon removes part or all of the trapezium, the arthritic wrist bone, so there is no longer any damaged surface to grind against. Then a wrist tendon called the flexor carpi radialis is harvested through an incision in the forearm. One end of that tendon is threaded through a hole drilled in the base of the thumb’s metacarpal bone and sewn back onto itself, reconstructing the ligament that holds the thumb in position.
The remaining portion of tendon is rolled into a tight coil, sometimes called an “anchovy,” and tucked into the space where the trapezium used to sit. This acts as a cushion, mimicking the shock-absorbing role that healthy cartilage once played. Synthetic spacers can also fill this role, avoiding the need to sacrifice a tendon. Temporary wires are placed to hold the thumb in correct alignment and are removed about four weeks later. LRTI can be used across all four stages of thumb arthritis, making it one of the most versatile options.
Total Joint Replacement
A newer approach replaces the CMC joint with a prosthetic implant, similar in concept to a hip or knee replacement. Modern designs use a cementless, ball-in-socket configuration with a metal component articulating against a polyethylene liner. These implants simplify the joint’s natural double center of rotation into a single center within the trapezium. Current generation implants with dual-mobility designs have significantly reduced the risk of early dislocation, which was a common problem with older models. Studies of these newer implants report 10-year survival rates above 90%.
That said, prosthetic replacement at the thumb CMC joint remains somewhat controversial. Some orthopedic guidelines still favor tendon-based procedures over implants, particularly because implants can loosen or wear out over a patient’s lifetime. Joint replacement tends to be considered more carefully in younger, physically active patients who would put high demands on the prosthesis for decades.
Other Surgical Options
Several less common procedures also fall under the CMC arthroplasty umbrella. Joint fusion (arthrodesis) permanently locks the bones together, eliminating pain but also eliminating motion. This is sometimes preferred for younger workers in heavy manual trades with stage II or III disease. Arthroscopic debridement, a minimally invasive cleaning of the joint, can help in early-stage disease. Joint denervation, which cuts the tiny nerves carrying pain signals from the joint, can be used across all stages when the goal is pain relief without altering the joint structure.
What Recovery Looks Like
Recovery from CMC arthroplasty is measured in months, not weeks. Immediately after surgery, your hand is wrapped in a bulky dressing with a plaster splint covering the thumb, wrist, and forearm. At your first follow-up, typically 10 to 14 days later, the stitches come out and you’re fitted with a custom removable thumb brace made by an occupational therapist.
You wear that brace full-time for four more weeks, removing it several times a day only to do gentle prescribed exercises: slow, controlled movements of the thumb with about 10 repetitions each. After roughly six weeks, the brace comes off for light daily activities, though you continue wearing it at night until 8 to 12 weeks after surgery. At the six-week mark, hand therapy ramps up to about twice a week, focusing on reducing swelling and rebuilding range of motion.
Pinching and gripping are off-limits until around 8 to 10 weeks post-op. By three months, most people can stop using the brace entirely. Full recovery, meaning a return to demanding hand activities without restriction, often takes four to six months. The timeline can stretch longer depending on the specific procedure, your hand dominance, and the physical demands of your daily life or job.
Risks and Complications
The most common complication is irritation of the superficial sensory radial nerve, a nerve that runs right through the surgical field and provides sensation to the back of the thumb. If the nerve is nicked or stretched during surgery, it can form a painful lump called a neuroma. Surgeons take care to identify and protect the nerve, but its location makes it inherently vulnerable.
With trapeziectomy-based procedures, the thumb’s metacarpal bone can gradually sink into the space left by the removed trapezium. This settling, called subsidence, doesn’t always cause problems, but it can lead to the metacarpal impinging against neighboring bones and producing a new source of mechanical pain. The tendon graft used for suspension can also extrude or fail over time, which may require revision surgery.
Less common but more serious risks include complex regional pain syndrome, a condition involving chronic pain and abnormal nerve signaling that can develop after any hand surgery. Infection and stiffness are possible with any surgical procedure. Untreated looseness at the joint where the thumb meets the index finger (the MCP joint) can also undermine results if it isn’t addressed at the time of surgery.
How Well It Works
Patient satisfaction after CMC arthroplasty is generally high. In studies comparing trapeziectomy to prosthetic replacement, 76% of trapeziectomy patients said they would have the same surgery again, compared to 89% of those who received a prosthetic implant. Pain scores dropped substantially with both approaches. One comparative study found pain decreased by 86% in the implant group and nearly 70% in the trapeziectomy group, with similar improvements in overall hand function scores.
These numbers reflect what most hand surgeons observe in practice: the large majority of patients get meaningful, lasting pain relief regardless of which technique is used. Grip and pinch strength improve over the first year, though they rarely return to what they were before arthritis set in. The tradeoff most patients make is exchanging peak strength for a thumb that works comfortably throughout the day without pain.