What is the assessment and treatment approach for a thumb injury?

Assessment and Treatment of Thumb Injuries

Initial Assessment

Obtain a minimum 3-view radiographic series (PA, lateral, and oblique) immediately for any suspected thumb injury to exclude fracture or avulsion before assuming a pure ligamentous injury. 1, 2

Clinical History and Examination

• Ask specifically about mechanism of injury, particularly hyperabduction or hyperextension forces applied to the thumb metacarpophalangeal (MCP) joint, which suggests ulnar collateral ligament (UCL) injury 3
• Document occupational demands and hand dominance, as these influence treatment decisions 4
• Perform valgus stress testing at the MCP joint, ideally 4-5 days post-injury when sensitivity and specificity are maximized 2
• Assess for laxity, pain, decreased pinch strength, and joint instability 3, 4

Imaging Algorithm

Step 1: Plain Radiographs

• Always obtain radiographs first to detect fractures, avulsion injuries at ligament insertion sites, and joint alignment abnormalities 2, 5
• Two views are inadequate and miss important pathology; three views are mandatory 1, 2

Step 2: Advanced Imaging (if radiographs negative but clinical suspicion high)

• If stress testing reveals MCP joint laxity despite negative radiographs, proceed immediately to ultrasound or MRI to detect complete displaced tears (Stener lesion) requiring surgery 2
• MRI is the imaging modality of choice for soft-tissue injuries, with 100% sensitivity and 94-100% specificity for detecting displaced UCL tears 6, 3
• Ultrasound can identify Stener lesions by showing absence of the UCL and presence of a hypoechoic mass proximal to the metacarpal tubercle 6

Step 3: Repeat Imaging (alternative approach)

• If immediate advanced imaging is unavailable and clinical suspicion persists, repeat radiographs in 10-14 days 2

Treatment Approach

Non-Displaced/Partial Tears

• Nonoperative treatment with splinting can be attempted initially, though it often fails and necessitates surgery 4
• The failure rate of conservative management is significant enough that surgical treatment should be strongly considered even for acute injuries 4

Complete or Displaced Tears (Stener Lesion)

Surgical repair or reconstruction is mandatory for complete displaced tears, as nonoperative treatment frequently fails. 2, 4

• Acute UCL injuries (presenting early) should undergo surgical repair 4
• Chronic UCL injuries (delayed presentation) should undergo autograft reconstruction 4
• Both approaches yield excellent clinical outcomes with no significant difference in pain, range of motion, key-pinch strength, or stability between repair and reconstruction 4
• Complications after surgery are rare 4

Post-Operative Management

• Initiate active finger motion exercises immediately following stable fixation to prevent stiffness 1
• Wrist motion does not require early initiation 1
• Consider vitamin C supplementation for prevention of disproportionate pain 1

Critical Pitfalls to Avoid

• Never rely on only 2 radiographic views—this misses fracture details and can lead to delayed diagnosis with functional impairment 1, 2
• Do not assume a "sprain" without radiographs—UCL injuries are notorious for being missed by inexperienced personnel in emergency departments 3
• Do not delay surgical referral for Stener lesions—the adductor pollicis aponeurosis becomes interposed between the ruptured ligament and its insertion site, preventing healing without surgery 6, 2
• Avoid prolonged nonoperative treatment—even after significant delay or failed conservative management, excellent outcomes can still be achieved surgically 4