A 40 yo M presents to the ED with R wrist pain. Onset was just before arrival when he was lifting at work, "felt a pop" and had sudden onset of pain. Exam reveals swelling and tenderness of the R wrist. Neurovascular exam is normal. A R wrist xray is done and shown below.  What's the diagnosis? (scroll down for answer)

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 w/ FOOSH- causes forceful wrist extension, rupturing the scapholunate interosseous ligament
• also associated with spastic paresis, RA, and congential ligament laxity
• Presentation
• wrist swelling and point tenderness over dorsal aspect of wrist
• pain w/ 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 ortho/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