A carpometacarpal (CMC) arthroplasty is a surgical procedure designed to treat severe arthritis at the base of the thumb. The CMC joint, also known as the basal joint, connects the thumb metacarpal bone to a small wrist bone called the trapezium. Arthroplasty refers to the surgical reconstruction of a damaged joint to restore function and eliminate pain. This procedure is common for advanced thumb base arthritis that has not responded to non-surgical treatments.
Understanding CMC Joint Arthritis
The CMC joint is a unique saddle-shaped joint that provides the thumb with its wide range of motion, allowing it to swivel, pivot, and pinch against the fingers. Covering the ends of the bones is smooth articular cartilage, which acts as a cushion and allows the bones to glide frictionlessly. Osteoarthritis, a degenerative “wear-and-tear” condition, causes this cartilage to progressively break down and thin over time.
This loss of cushioning leads to bone-on-bone friction, resulting in inflammation, stiffness, and pain at the base of the thumb. Patients typically experience a sharp or aching pain that worsens with activities like gripping, grasping, or pinching objects. Reduced grip strength and a grinding sensation when moving the thumb are common symptoms as the joint deteriorates. As the condition progresses, the joint may develop a bony, enlarged appearance, and the thumb’s position can become deformed.
Before considering surgery, treatment focuses on conservative methods such as splinting, anti-inflammatory medications, and corticosteroid injections. Surgery is reserved for those with moderate to severe arthritis who continue to experience significant pain and functional limitations despite these non-operative approaches.
Details of the Surgical Procedure
The most prevalent surgical approach for CMC arthroplasty is Ligament Reconstruction Tendon Interposition (LRTI). This technique addresses both joint pain and the stability of the thumb base. The fundamental step involves a trapeziectomy, which is the complete removal of the damaged trapezium bone.
This removal eliminates the painful bone-on-bone rubbing. This leaves a space between the thumb metacarpal and the remaining wrist bones. To stabilize the joint and prevent the thumb’s metacarpal bone from collapsing into the empty space, a local tendon is used for reconstruction.
A common tendon harvested for this purpose is the Flexor Carpi Radialis (FCR) or the Palmaris Longus. A strip of this tendon is secured to the base of the thumb metacarpal bone, reconstructing the damaged ligament to provide stability. The remaining portion of the harvested tendon is then rolled up into a bundle, often referred to as an “anchovy,” and placed into the space where the trapezium once was. This tendon acts as a soft-tissue cushion or spacer, preventing the thumb bone from rubbing directly against the wrist bones.
Post-Operative Recovery and Expectations
Recovery from CMC arthroplasty requires adherence to a structured rehabilitation protocol. Immediately following the surgery, the hand is immobilized in a bulky dressing and a splint or cast for approximately two to four weeks to protect the surgical site. During this initial phase, managing pain and keeping the hand elevated above the heart are important to control swelling.
After the initial immobilization period, the surgeon or hand therapist will remove the cast and replace it with a custom removable splint. This marks the beginning of physical or occupational hand therapy. Therapy initially focuses on gentle active and passive range-of-motion exercises to prevent stiffness in the thumb and wrist. The next phase of therapy, typically starting around six weeks post-operation, involves progressive strengthening exercises to rebuild grip and pinch strength.
The total recovery time before a patient can resume heavy activities, forceful gripping, or lifting usually ranges from three to six months. Although patients often experience significant pain reduction soon after surgery, the full return of strength and final improvement can continue for up to a year. While stiffness and swelling are common concerns in the months following the procedure, the expected long-term outcome is a substantial reduction or complete elimination of pain. Patients should anticipate wearing the protective splint for certain activities for up to three months before being cleared for unrestricted use.