What is the treatment for a mild subluxation of the thumb Metacarpophalangeal (MCP) joint?

Treatment of Mild Thumb MCP Subluxation

Immediate immobilization with a custom-made thumb spica splint or orthosis for at least 3 months, combined with hand therapy, is the recommended first-line treatment for mild subluxation of the thumb MCP joint. 1

Initial Management

Immobilization is the cornerstone of treatment:

• Apply a custom-made thumb spica splint immediately upon diagnosis 1
• Custom fabrication by a specialized hand therapist or occupational therapist is strongly preferred over prefabricated options, as it improves compliance and ensures proper fit 1
• The orthosis should be worn during all activities of daily living to protect healing ligamentous structures 1
• Minimum immobilization duration is 3 months, though some cases may require 3-6 weeks depending on severity 1, 2

The evidence strongly supports custom orthoses over generic splints. While older studies used standard thumb spica splints with success rates of 85% 3, current guidelines emphasize custom fabrication for optimal outcomes 1.

Clinical Reassessment Protocol

Follow a structured reassessment timeline:

• Perform clinical reassessment at 1 week after initial immobilization 1
• If the joint remains unstable or subluxation recurs at 1-week follow-up, obtain MRI imaging promptly (within days) 1
• MRI demonstrates 100% sensitivity and specificity for assessment of thumb ulnar collateral ligament tears and guides treatment decisions 1

This early reassessment is critical—it identifies the 15% of patients who will ultimately require surgical intervention 3, allowing for timely referral rather than prolonged unsuccessful conservative treatment.

Hand Therapy Integration

Initiate structured hand therapy regardless of treatment pathway:

• Begin education on joint protection strategies and assistive devices immediately to prevent re-injury 1
• Start exercises to improve joint mobility, muscle strength, and thumb base stability after 3-6 weeks of immobilization once initial healing has occurred 1
• Continue therapy throughout the immobilization period and beyond 1

Surgical Considerations

Refer for surgical evaluation if:

• Joint instability persists beyond 1 week of proper immobilization 1
• Subluxation recurs despite appropriate splinting 1
• MRI reveals complete ligamentous disruption or complex injury 1

Approximately 15% of patients will demonstrate persistent laxity at 12 weeks and require surgical reconstruction, which yields excellent results when performed 3.

Common Pitfalls to Avoid

• Do not use prefabricated splints as primary treatment—they have lower compliance and suboptimal fit compared to custom orthoses 1
• Do not delay MRI if instability persists at 1 week—early identification of surgical candidates prevents prolonged unsuccessful conservative treatment 1
• Do not immobilize for less than 3 months in stable cases—premature discontinuation leads to recurrent instability 1
• Do not skip hand therapy—it is essential for both conservative and surgical management 1