Thumb Base (CMC) Arthritis

What is thumb base arthritis?

The thumb base (carpometacarpal or CMC) joint is one of the most commonly affected joints by osteoarthritis, particularly in women over the age of 50. The joint connects the thumb metacarpal to a small wrist bone called the trapezium, and it carries enormous load during pinching and gripping.

As the cartilage wears away, the joint becomes painful, stiff, and progressively unstable, making simple tasks - opening jars, turning keys, twisting taps - painful and weak.

Symptoms

• Pain at the base of the thumb, particularly with pinching and gripping
• Weakness - difficulty opening jars, turning keys, wringing out a cloth
• Swelling and tenderness at the base of the thumb
• A visible bump or prominence at the joint as the disease progresses
• Stiffness, often worse in the morning

Diagnosis

The diagnosis is usually straightforward from the history and examination. A plain X-ray of the thumb confirms the diagnosis and shows the severity of arthritis.

Non-surgical treatment

Most patients are managed non-surgically for years before considering surgery:

• Hand therapy and splinting - a custom thumb splint, particularly worn at night or during aggravating activities, can significantly reduce symptoms
• Activity modification - tools and techniques that reduce load on the thumb
• Simple analgesia and anti-inflammatories
• Corticosteroid injection - can provide relief for months to years, and can be repeated

Surgery is offered when non-surgical measures are no longer controlling pain and the condition is limiting daily function.

Surgical treatment - LRTI (Ligament Reconstruction and Tendon Interposition)

Dr de Hoog uses LRTI (Ligament Reconstruction and Tendon Interposition) using an FCR (flexor carpi radialis) tendon graft - the most widely performed and well-established operation for thumb base arthritis, with decades of good long-term outcomes.

The operation involves:

• Removing the trapezium (the small wrist bone at the base of the thumb) - this eliminates the arthritic joint surfaces
• Using a strip of the patient’s own FCR tendon (taken from the wrist) to both reconstruct the supporting ligament of the thumb and fill the space left by the trapezium
• This restores stability to the thumb and provides a cushion for the thumb metacarpal to rest against

The procedure is performed at Townsville Day Surgery or Mater Hospital Pimlico, under a regional nerve block with light sedation. It typically takes 60-75 minutes. You go home the same day.

Recovery

Recovery from LRTI is longer than most other hand operations because of the reconstruction involved:

• Day of surgery - home with a thumb splint
• Weeks 1-4 - thumb in a splint or cast; early finger movement encouraged; stitches out around 10-14 days
• Weeks 4-6 - transition into a custom removable splint; hand therapy begins in earnest
• Weeks 6-12 - progressive strengthening; driving typically around 6-8 weeks; desk work at 2-3 weeks; manual work from 12 weeks
• Months 3-6 - grip and pinch strength continue to improve
• Up to 12 months - final outcome becomes apparent

Structured hand therapy is essential for a good outcome and is available through NQ Hand Care Clinic at the same North Ward location.

Risks

• Scar tenderness and stiffness - common early, usually settles with therapy
• Ongoing pain - a small proportion of patients have persistent discomfort, usually improved but not fully resolved
• Weakness - some residual weakness of pinch strength is common, though function is markedly improved from pre-op
• Nerve irritation - the superficial radial nerve runs close to the surgical site; irritation or numbness can occur
• Subsidence - the thumb metacarpal can settle slightly into the space left by the trapezium. Usually not symptomatic
• Complex regional pain syndrome - rare but recognised