What is the appropriate management for a patient with a knife stab wound to the palm that prevents full extension of the third finger?

Management of Knife Stab Wound to Palm with Inability to Fully Extend Third Finger

This patient requires immediate hand surgery referral for suspected extensor tendon laceration, following initial radiographic evaluation to exclude fracture fragments and assess for bone involvement that would necessitate operative fixation. 1

Initial Diagnostic Approach

Radiographic Evaluation

• Obtain standard 3-view radiographs of the hand immediately (posteroanterior, lateral, and oblique projections) to detect fracture fragments, as large fragments require open reduction and internal fixation. 1
• Radiographs are specifically used to assess for bone involvement and determine the need for operative fixation in extensor tendon injuries. 1
• An internally rotated oblique projection in addition to standard externally rotated oblique increases diagnostic yield for phalangeal fractures. 1

Clinical Assessment Priorities

• Loss of active finger extension following a palmar stab wound indicates extensor tendon injury until proven otherwise, despite the anatomically unusual presentation (extensor tendons run dorsally, but penetrating trauma can track through the hand). 2
• Examine for associated nerve injury, particularly the ulnar deep motor nerve, which can be easily missed in palmar stab wounds as sensation and major flexor tendon function remain intact. 3
• Assess for vascular injury including pulsatile masses (false aneurysm formation can occur 2-3 weeks post-injury). 4

Definitive Management

Surgical Intervention

• Extensor tendon injuries require operative repair, ideally performed immediately if diagnosed acutely. 2
• Complete or partial extensor tendon injuries, particularly near the proximal interphalangeal joint, risk "buttonhole" (boutonniere) deformity if not addressed surgically. 2
• If radiographs demonstrate bony avulsion at the extensor mechanism insertion (osseous mallet injury) with >1/3 articular surface involvement, palmar displacement of distal phalanx, or interfragmentary gap >3mm, operative fixation is indicated. 1

Advanced Imaging Considerations

If radiographs are negative but clinical suspicion remains high for tendon injury:

• MRI of the hand without IV contrast is ideal for evaluating tendon injuries and surgical planning, with sensitivity of 89-92% for extensor hood evaluation (though detection of extensor hood injuries ranges from 28-85%). 1
• Ultrasound of the hand represents an equivalent alternative to MRI for tendon injury assessment and allows dynamic evaluation. 1

Critical Pitfalls to Avoid

• Do not dismiss small, seemingly negligible stab wounds—deep underlying structures (tendons, nerves) can be destroyed even with minimal visible injury. 2
• Extensor tendon injuries are easily overlooked by inexperienced examiners, particularly partial lacerations that may retain some extension capability initially. 2
• Ulnar deep motor nerve paralysis from palmar stab wounds is frequently undiagnosed at initial presentation because sensation and major tendon function appear normal; early diagnosis and nerve repair yield excellent results and prevent permanent paralytic deformity. 3
• Delayed diagnosis leads to functional impairment and permanent sequelae including typical deformities and chronic disability. 1, 2

Infection Risk

• All stab wounds carry general infection risk requiring appropriate wound management, tetanus prophylaxis, and consideration of antibiotic coverage. 2