M18.12 Unilateral primary osteoarthritis of first carpometacarpal joint, left hand

Name of the Condition

• Unilateral primary osteoarthritis of first carpometacarpal joint, left hand

Summary

Unilateral primary osteoarthritis of the first carpometacarpal joint, left hand, is a degenerative joint disease affecting the base of the left thumb. It involves cartilage breakdown, leading to pain, stiffness, and functional limitations, particularly with gripping or pinching tasks.

Causes

Osteoarthritis develops from cartilage degradation in the joint. In this condition, wear and tear over time leads to cartilage breakdown, bone changes, and joint space narrowing at the first carpometacarpal joint of the left hand.

Risk Factors

• Age: more common in older adults.
• Gender: higher prevalence in women.
• Occupational: repetitive thumb use.
• Previous thumb injuries.
• Genetic predisposition to osteoarthritis.

Symptoms

• Pain at the left thumb base, worsened by movement.
• Swelling and stiffness.
• Reduced thumb strength.
• Difficulty pinching or gripping objects.
• Possible bony prominence at the joint.

Diagnosis

Physical examination assesses pain, swelling, and range of motion. Imaging, such as X-rays, evaluates joint space narrowing, bone spurs, or subchondral changes to confirm osteoarthritis.

Treatment Options

• Medications: NSAIDs for pain relief.
• Splints or braces: Limit thumb movement and provide support.
• Occupational therapy: Exercises to improve strength and function.
• Corticosteroid injections: Reduce inflammation.
• Surgery: For severe cases, options include joint fusion or replacement.

Prognosis and Follow-Up

Prognosis depends on severity and treatment adherence. Regular follow-up monitors symptoms and joint function. Early intervention may slow progression and improve quality of life.

Complications

• Chronic pain.
• Reduced hand function.
• Joint deformity.
• Difficulty with daily tasks.

Lifestyle & Prevention

• Avoid repetitive thumb strain.
• Use ergonomic tools.
• Maintain a healthy weight.
• Perform thumb-strengthening exercises.
• Protect the joint during activities.

When to Seek Professional Help

Seek care if pain persists, worsens, or limits daily activities. Consult a provider for sudden swelling, redness, or loss of motion.

Tips for Medical Coders

Document laterality (left hand) and specify "primary" osteoarthritis. Ensure clinical notes support unilateral involvement and exclude secondary causes. Code M18.12 is specific to the left hand; verify documentation aligns with the code's criteria.