What is the likely diagnosis and recommended management for a volleyball player who hyperextended his thumb and now has ulnar‑side pain at the thumb metacarpophalangeal joint?

Thumb Ulnar Collateral Ligament (UCL) Injury ("Skier's Thumb")

This volleyball player most likely has an ulnar collateral ligament (UCL) tear of the thumb MCP joint, and management depends critically on whether the tear is complete or partial—complete tears (especially with a Stener lesion) require surgical repair, while partial tears can be managed conservatively with thumb spica immobilization.

Diagnosis

The mechanism—hyperextension with ulnar-side MCP pain—is classic for UCL injury 1, 2, 3. This occurs when a valgus/radial deviation force is applied to an abducted or extended thumb, common in volleyball when the ball strikes the thumb 3.

Clinical Assessment

• Stress testing: Apply valgus stress to the thumb MCP joint in both full extension and 30° flexion

  • 30-35° of laxity compared to contralateral side suggests complete tear

  • Lack of firm endpoint indicates complete rupture 4, 3
• Pain location: Ulnar aspect of MCP joint
• Palpable mass: May indicate Stener lesion (retracted UCL stump superficial to adductor aponeurosis)

Imaging Strategy

Start with plain radiographs to rule out avulsion fractures 5.

For definitive soft tissue diagnosis, MRI is the gold standard 5:

• 100% sensitivity and specificity for UCL tears 5
• Identifies Stener lesions (critical for surgical planning) 5
• Distinguishes partial from complete tears

Ultrasound is an acceptable alternative if MRI unavailable 5:

• Can identify Stener lesions by showing hypoechoic mass proximal to metacarpal tubercle with absent UCL at insertion 5
• Dynamic examination demonstrates relationship of adductor aponeurosis to retracted ligament 5

Management Algorithm

Complete Tears (>30° instability, no endpoint, or Stener lesion present)

Surgical repair is indicated 1, 2, 6, 4, 3:

• Acute repairs (within 3-6 weeks) have superior outcomes to delayed reconstruction
• Stener lesions will NOT heal without surgery—the adductor aponeurosis blocks ligament-to-bone healing 1, 3
• Primary repair with or without suture tape augmentation provides excellent outcomes 1
• Recent evidence supports suture tape augmentation for earlier return to function 1

Partial Tears (<30° instability with firm endpoint)

Conservative management 2, 6, 4, 3:

• Thumb spica cast or splint immobilization for 4-6 weeks
• Gradual return to activity with protective taping
• Re-examine at 4-6 weeks; if persistent instability develops, proceed to surgery

Critical Pitfall: The Stener Lesion

A Stener lesion occurs in approximately 60-80% of complete UCL ruptures 3. The adductor aponeurosis becomes interposed between the torn UCL and its insertion site, preventing healing. This is an absolute indication for surgery and cannot be managed conservatively 5, 1, 3. Missing this diagnosis leads to chronic instability, pain, and loss of pinch strength.

Sport-Specific Considerations

For this volleyball player 2, 6:

• Timing: Acute surgical repair allows return to sport in 8-12 weeks with excellent outcomes
• Position matters: Setters and blockers have higher demands on thumb stability
• Protective splinting: May allow earlier return in partial tears, though re-injury risk exists
• Delayed treatment: Chronic injuries require ligament reconstruction rather than repair, with longer recovery 6, 4

Key Clinical Pearls

• The absence of a palpable "mass" does NOT rule out a Stener lesion—imaging is essential for complete tears
• Stress radiographs showing >30° angulation indicate complete rupture requiring surgery
• Untreated complete tears result in chronic instability, arthritis, and permanent loss of pinch strength 1, 4, 3
• Do not delay imaging or specialist referral—outcomes deteriorate significantly after 3-6 weeks when primary repair becomes technically difficult