What is the management plan for a 46-year-old male with hyperextension of the wrist and thumb, no swelling, normal X-rays, and numbness at the Metacarpophalangeal (MCP) lateral area?

Management of Hyperextension Wrist and Thumb Injury with Lateral MCP Numbness

Clinical Assessment and Differential Diagnosis

This presentation suggests a radial digital nerve injury to the thumb, likely from hyperextension trauma affecting the lateral (radial) aspect of the MCP joint. The numbness localized to the lateral MCP area with preserved medial sensation indicates injury to the radial digital nerve branch rather than the median nerve proper 1.

Key Diagnostic Considerations

• Radial digital nerve contusion or stretch injury is the most likely diagnosis given the hyperextension mechanism and lateral-only sensory deficit 1
• The normal X-rays appropriately rule out fracture, avulsion injuries, or bony mallet deformities that would require operative fixation 1
• Volar plate injury should be considered with hyperextension mechanisms, though typically presents with joint instability rather than isolated numbness 2, 3
• Collateral ligament injury (radial or ulnar) can accompany hyperextension trauma and may contribute to symptoms 1, 2

Physical Examination Priorities

Perform these specific assessments beyond standard examination 1:

• Two-point discrimination testing on both lateral (radial) and medial (ulnar) aspects of the thumb to quantify sensory deficit
• MCP joint stability testing in both radial-ulnar and dorsal-volar planes to assess for ligamentous injury 2
• Active and passive MCP range of motion to identify any mechanical locking or extension lag 4
• Volar plate integrity by assessing resistance to passive hyperextension compared to contralateral side 3, 5
• Thumb opposition and pinch strength to evaluate thenar function and rule out median nerve involvement 5

Initial Management Strategy

Conservative Treatment Protocol

Initiate conservative management with immobilization, as most soft tissue injuries and nerve contusions resolve within 3-6 months 1:

• Thumb spica splint immobilizing the MCP joint in slight flexion (15-20°) for 2-3 weeks to protect healing structures 1
• Relative rest avoiding hyperextension stress and forceful pinch activities 1
• Ice application for acute pain control in the first 48-72 hours 1

Pain Management

Follow this analgesic ladder 1:

• Paracetamol (acetaminophen) up to 4g daily is first-line for pain control due to efficacy and safety profile 1
• Topical NSAIDs are preferred over oral NSAIDs for localized hand injuries with mild-moderate pain 1
• Oral NSAIDs at lowest effective dose only if paracetamol inadequate, with gastroprotection if indicated 1

Advanced Imaging Indications

When to Order MRI

MRI without IV contrast should be obtained if symptoms persist beyond 2-3 weeks or if clinical examination suggests significant soft tissue injury 1:

• MRI has 67% sensitivity and 91% specificity for collateral ligament injuries at MCP joints 1
• MRI with dedicated neurography sequences can visualize traumatic nerve injury when nerve dysfunction persists 1
• MRI effectively evaluates volar plate tears, capsular injuries, and occult fractures not visible on radiographs 1

Ultrasound Considerations

• Ultrasound can assess collateral ligaments and volar plate as a dynamic, cost-effective alternative to MRI 1
• Useful for excluding foreign bodies if penetrating trauma suspected 1

Follow-Up and Referral Criteria

Expected Recovery Timeline

• Most nerve contusions recover within 6-12 weeks with conservative management 1
• Sensory recovery typically precedes motor recovery in peripheral nerve injuries
• Re-evaluate at 2-3 weeks to assess for improvement in numbness and pain 1

Indications for Hand Surgery Referral

Refer to hand surgery if 1, 2, 5:

• Persistent numbness beyond 3 months suggesting nerve laceration rather than contusion
• MCP joint instability with >20-30° hyperextension compared to contralateral side
• Mechanical symptoms such as locking or catching suggesting intra-articular pathology 4
• Progressive weakness of thumb pinch or opposition
• Failed conservative management after 3-6 months with persistent pain and functional limitation 1, 2

Common Pitfalls to Avoid

• Do not obtain X-rays to diagnose soft tissue nerve injuries—they are normal in these conditions and provide no diagnostic value 6
• Avoid prolonged immobilization beyond 3 weeks as this can lead to MCP joint stiffness and contracture 1
• Do not dismiss hyperextension laxity—if MCP hyperextension exceeds 60°, this may require surgical volar plate advancement even after conservative treatment 3
• Recognize that isolated lateral numbness does NOT indicate carpal tunnel syndrome—median nerve compression causes palmar and volar digital symptoms, not isolated lateral MCP numbness 1