Thumb CMC Arthroplasty

Overview

The joint at the base of the thumb is called the carpometacarpal (CMC) joint. It is shaped like a saddle, which gives the thumb its huge range of motion. That same shape makes it one of the most common places in the hand to get arthritis. Worn cartilage causes pain with pinch, grip, and fine hand work. Over time the base of the thumb drops in toward the palm.

How the Procedure Works

We remove the trapezium (a trapeziectomy), the small wrist bone the thumb sits on, through a small incision on the back of the thumb. We take all of it; a remnant left behind can wear down and allow symptoms to return. Once the space is clear, we hold the thumb bone in place with a small implant instead of one of your own tendons. A strong surgical stitch is passed through the thumb bone and anchored to the neighboring index bone with small buttons. This supports the thumb's position while the tissue around it heals.

Some weakness during healing is common, and recovery varies from person to person. The aim is to relieve pain at the base of the thumb and keep usable pinch and grip for everyday tasks.

When to Consider Thumb CMC Arthroplasty

We generally offer thumb CMC arthroplasty when symptoms, imaging, and a full course of non-surgical care all 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, plus joint-space narrowing on X-ray.

2. Failure of conservative care

   A thumb (spica) splint, activity changes, therapy, and injections that have not given lasting relief.

3. Functional limitation

   Trouble with tasks that need pinch: opening jars, buttoning, writing, keys.

Physicians Who Perform Thumb CMC Arthroplasty

Michael S. Vrana, M.D.

Risks

Every operation carries risk. Whether thumb CMC arthroplasty is appropriate is decided for each patient in consultation with the surgeon, weighing these risks against the limitations that untreated arthritis at the base of the thumb places on daily use of the hand.

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

• bleeding and infection
• anesthesia risk
• stiffness
• irritation of a small skin nerve (the superficial radial nerve), causing numbness on the back of the thumb
• some loss of thumb height (subsidence), usually well tolerated
• ongoing pain if nearby joints are also affected
• scar tenderness

We proceed when there is advanced arthritis at the base of the thumb that has not improved with splinting and injections. If this operation is not right for you, we will not recommend it.

Further Reading

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

• Thumb Carpometacarpal (CMC) Arthroplasty — AAOS OrthoInfo