M20.02 Boutonniere deformity

Name of the Condition

• Boutonniere deformity
• ICD-10-CM Code: M20.02

Summary

Boutonniere deformity is a structural abnormality of the finger characterized by a flexion deformity at the proximal interphalangeal (PIP) joint and hyperextension at the distal interphalangeal (DIP) joint. This results in a "buttonhole" appearance of the affected finger and can impair function, particularly in gripping or manipulating objects.

Causes

The deformity typically arises from disruption of the central slip of the extensor tendon at the PIP joint, often due to trauma or inflammatory conditions. Common causes include a direct blow to the finger, laceration of the tendon, or chronic inflammatory diseases such as rheumatoid arthritis that weaken tendon integrity.

Risk Factors

• History of finger trauma or injury
• Chronic inflammatory conditions (e.g., rheumatoid arthritis)
• Occupational or recreational activities involving repetitive hand use
• Age-related tendon degeneration
• Previous tendon or joint damage in the affected finger

Symptoms

• Flexion at the PIP joint with hyperextension at the DIP joint
• Visible "buttonhole" appearance of the finger
• Pain, swelling, or tenderness over the PIP joint
• Reduced range of motion or stiffness in the affected finger
• Difficulty gripping objects or performing fine motor tasks

Diagnosis

Diagnosis involves a physical examination to assess finger alignment, joint mobility, and tendon function. Imaging studies, such as X-rays, may be used to evaluate bone structure and joint integrity. Patient history, including injury or disease onset, helps guide evaluation.

Treatment Options

Treatment depends on the severity and underlying cause. Conservative management may include splinting to maintain PIP joint extension, physical therapy to restore function, and anti-inflammatory medications. Severe cases may require surgical repair of the extensor tendon or joint reconstruction.

Prognosis and Follow-Up

Prognosis varies based on the cause and timeliness of treatment. Early intervention often improves outcomes, while chronic or untreated cases may lead to permanent deformity. Follow-up care typically involves monitoring joint function and adjusting treatment as needed.

Complications

• Permanent joint stiffness or deformity
• Chronic pain or reduced grip strength
• Recurrent tendon instability
• Secondary arthritis due to altered joint mechanics

Lifestyle & Prevention

• Avoid activities that strain the finger joints
• Use protective gear during high-risk activities (e.g., sports)
• Maintain joint flexibility through regular exercise
• Manage underlying inflammatory conditions to reduce tendon stress

When to Seek Professional Help

Seek medical attention if you experience sudden finger deformity, persistent pain, or difficulty moving the finger. Early evaluation is important to prevent progression and optimize treatment outcomes.

Tips for Medical Coders

Document the specific finger affected and any underlying causes (e.g., trauma, arthritis) to support code assignment. Ensure clinical notes specify the presence of PIP flexion and DIP hyperextension, as these are key diagnostic features of boutonniere deformity.