The carpometacarpal (CMC) joint is the small, specialized joint located at the base of the thumb, connecting the thumb’s metacarpal bone to a small wrist bone called the trapezium. This unique saddle-shaped joint allows the wide range of motion that makes the human thumb so useful for grasping and pinching. CMC arthroplasty is a surgical procedure designed to treat severe arthritis in this joint. The term arthroplasty generally involves removing the damaged joint surfaces and reconstructing the area. This surgery is a common and effective solution for patients whose thumb pain and loss of function can no longer be managed with non-surgical treatments.
Understanding Basal Joint Arthritis
The condition that necessitates this procedure is basal joint arthritis, a form of osteoarthritis where the protective cartilage covering the ends of the bones wears away. This erosion causes the bones of the thumb metacarpal and the trapezium to rub directly against each other, leading to inflammation and pain. Patients typically experience deep, aching pain localized at the base of the thumb, which is often aggravated by pinch motions or activities requiring a strong grip, such as opening jars or turning a key. As the condition progresses, a grinding sensation may be felt, and the joint can become stiff, leading to weakness and a visible “squaring” or bony prominence at the thumb’s base. Non-surgical options, including specialized splints, anti-inflammatory medications, and corticosteroid injections, are the first line of defense, but surgery is indicated when these conservative measures fail to provide lasting relief and the arthritis has advanced to severe joint degeneration.
How the CMC Arthroplasty Procedure Works
The most common surgical approach for CMC arthroplasty is a trapeziectomy, the complete removal of the diseased trapezium bone, which immediately eliminates the source of the arthritic pain. Once the trapezium is removed, a gap or void remains between the thumb metacarpal and the remaining wrist bones. If this gap is left untreated, the metacarpal bone of the thumb can migrate downward, potentially leading to new pain from impingement on adjacent wrist bones.
Joint Reconstruction
To prevent this collapse and maintain the thumb’s height, the surgeon performs a reconstruction, often called a suspensionplasty or tendon interposition. A common method involves using a portion of the patient’s own tendon, such as the flexor carpi radialis (FCR) tendon. One part of the tendon is rolled up and placed into the space where the trapezium was, creating a cushion or spacer for the thumb metacarpal to rest on. The remaining part of the tendon is often woven through the base of the thumb and secured to an adjacent bone to act as a stabilizing ligament. Newer techniques may use a strong, non-biologic material, such as a suture-button device, instead of a tendon graft to tether the thumb’s base and maintain the joint space.
The Post-Surgery Recovery Timeline
Recovery from CMC arthroplasty is a gradual process. Immediately following the procedure, the hand is immobilized in a bulky dressing or cast for approximately two to six weeks to protect the surgical site and allow initial soft tissue healing. During this phase, managing swelling and pain is the primary focus, and movement of the fingers not involved in the surgery is encouraged to prevent stiffness.
Rehabilitation and Strengthening (2 Weeks – 6 Months)
Around the two-week mark, the sutures are typically removed, and the cast may be replaced with a custom-molded splint worn full-time for several more weeks. Physical or occupational therapy usually begins in this intermediate phase, starting with gentle, passive range-of-motion exercises to prevent stiffness while protecting the reconstruction. Between six and ten weeks post-surgery, the therapist progresses the patient to active range-of-motion exercises, and the splint is gradually weaned off for daily activities. Strengthening exercises, including light gripping and pinching, are typically introduced around the 10-to-12-week mark.
Return to Activity
Most patients can return to light-duty work within four to six weeks, but activities requiring heavy lifting or intense manual labor are restricted until at least three to six months after the surgery. Full recovery, marked by the return of strength and function, can take up to six months to one year.
Expected Long-Term Results
The ultimate goal of CMC arthroplasty is to provide pain relief, which is successfully achieved for most patients. Many studies report high rates of patient satisfaction, allowing individuals to resume daily activities that were previously hindered by the arthritic joint. The procedure consistently leads to improved functional capacity, particularly in tasks involving pinching and grasping. Patients see an improvement in grip and pinch strength compared to their pre-operative state, though it may take a full year for strength gains to stabilize. The reconstructed joint is durable, providing a stable, pain-free base for the thumb’s function for decades.