From the EMDaily Archives: What’s the Diagnosis? By Dr. Jacob Martin

A 40 year old male presents for right wrist pain. Onset was just before arrival when he was lifting at work, “felt a pop”, and had a sudden onset of pain. Exam reveals swelling and tenderness of the right wrist. Neurovascular exam is normal. A right wrist x-ray is performed and shown below. What’s the diagnosis?

Answer: Scapholunate Dissociation

• Background
  • Scapholunate ligament is most commonly injured ligament in the wrist
  • SLD is part of a spectrum of traumatic carpal bone instabilities
• Etiology
  • Most commonly occurs with FOOSH injury causing forceful wrist extension, rupturing the scapholunate interosseous ligament
  • Also associated with spastic paresis, rheumatoid arthritis, and congenital ligament laxity
• Presentation
  • Wrist swelling and point tenderness over dorsal aspect of wrist
  • Pain with wrist extension, radial deviation, and “clicking” sensation with movement
• Diagnosis
  • Obtain AP and lateral views (+/- grip compression view/wrist in ulnar deviation)
  • Radiographic signs:
    • Widening of the scapholunate joint space > 3mm (“Terry Thomas sign”)
    • Cortical ring sign – loss of ligamentous support results in rotary subluxation and palmar tilt of the scaphoid on AP radiograph 
  • MRI provides definitive diagnosis, rarely done in ED 
• ED Management
  • Pain management
  • Radial gutter splint
  • Urgent referral to orthopedics/hand specialist 
• Pearls and Pitfalls
  • Prompt recognition crucial
  • Delayed diagnosis is associated with chronic pain, joint instability, inflammatory arthritis, long-term degenerative changes

References:

Casey PD, Youngberg R.Scapholunate dissociation: a practical approach for the emergency physician.J EmergMed. 1993;11(6):701-707. doi:10.1016/0736-4679(93)90629-l

Long B, Koyfman A. Wrist Injuries. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, StapczynskiJ, Cline DM, ThomasSH. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw-Hill; Accessed September 29,2020.https://accessmedicine.mhmedical.com/content.aspx?bookid=2353&sectionid=222324635

Ramponi D, McSwigan T. ScapholunateDissociation.Adv Emerg Nurs J. 2016;38(1):10-14.doi:10.1097/TME.0000000000000094

Stevenson M, Levis JT. Image Diagnosis: Scapholunate Dissociation.Perm J. 2019;23:18-237. doi:10.7812/TPP/18-237