Thumb CMC arthroplasty

Overview

The carpometacarpal (CMC) joint at the base of the thumb is a saddle-shaped joint that allows the thumb's enormous range of motion — at the cost of being one of the most common sites of arthritis in the hand. Worn cartilage produces pain with pinch, grip, and fine-motor tasks, and over time the base of the thumb drops in toward the palm.

Before — advanced thumb CMC arthritis

After — thumb CMC arthroplasty

How the Procedure Works

We remove the trapezium completely through a small dorsal incision — partial removal reliably leads to recurrent symptoms as the remnant degenerates. Once the space is clear, the key decision is how to stabilize the thumb metacarpal base, which will otherwise migrate proximally and lose the thumb's reach. We use a slip of the flexor carpi radialis or abductor pollicis longus tendon to suspend the metacarpal and fill the dead space, keeping the base positioned so pinch strength is preserved. The suspension is set with the thumb in its functional position — slightly palmar-abducted — and we test active pinch before closing. A small subset of patients develops temporary weakness during healing, but long-term grip and pinch strength consistently return to useful levels, which is the outcome that matters for the activities that drove them to surgery.

When to Consider Thumb CMC Arthroplasty

Thumb CMC arthroplasty is generally offered when symptoms, imaging, and a trial of non-operative care together point to surgery as the next step. The typical picture includes:

1. Symptomatic basal-thumb arthritis

   Pain at the base of the thumb with pinch and grip, with radiographic joint-space narrowing.

2. Failure of conservative care

   Thumb spica splinting, activity modification, therapy, and injections that have not provided lasting relief.

3. Functional limitation

   Difficulty with pinch-dependent tasks — opening jars, buttoning, writing, keys.

Conditions This Treats

• Thumb CMC Arthritis

Physicians Who Perform Thumb CMC Arthroplasty

Michael S. Vrana, M.D.

Risks & Why We Still Recommend It

Every operation carries risk. The reason we offer this procedure is that the condition, left untreated, causes daily pain at the base of the thumb, weak pinch, and progressive loss of the grip that basal-joint arthritis eventually takes away. That is the trade we are managing — not eliminating risk, but choosing the smaller of two unfavorable trajectories.

The risks we discuss with patients before thumb CMC arthroplasty include:

• bleeding and infection
• anesthesia risk
• stiffness
• superficial radial nerve irritation causing dorsal thumb numbness
• loss of thumb height (subsidence), usually well-tolerated
• persistent pain if adjacent joints are also involved
• scar tenderness

The indication to proceed is end-stage thumb CMC (basal-joint) arthritis that has not responded to splinting and injection. Patients who don't need this operation don't get it.

Further Reading

External patient-education references and related OSI pages for additional background:

• Britannica — Hand (anatomy)
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language