lunate dislocation xray

A 46 year-old male presents with wrist pain after sustaining a mechanical fall and catching himself on his outstretched hand. An anteroposterior (left) and lateral (right) plain films of the wrist are obtained (photo credit).

What is the diagnosis (hint – there are 2 findings), injury classification system, associated findings, and the recommended management plan?

Lunate dislocation with associated ulnar styloid fracture1

Mayfield Classification: A mechanism of forced wrist extension with ulnar deviation produces a classic pattern of injuries that progressively worsen in severity:1-4

  • Stage I: Scapholunate dissociation (Figure 2A)
  • Stage II: Perilunate dislocation (Figure 2B)
  • Stage III: Perilunate dislocation with dislocation of triquetrum
  • Stage IV: Lunate dislocation (Figure 2C)

Figure. A. Scapholunate dissociation evidenced by widening between scaphoid and lunate (Terry Thomas sign). B. Perilunate dislocation (note that lunate articulates appropriately with radius). C. Lunate dislocation (tipped teacup with normal alignment of radius and capitate). Images courtesy of Radiopaedia on scapholunate dislocation (Radswiki), lunate dislocation (Dr. Andrew Dixon), and trans-scaphoid perilunate dislocation (Dr. Andrew Dixon). These injuries are important to identify as misdiagnosis and mistreatment may result in chronic instability, arthritis, or scapholunate advanced collapse (SLAC) with significant functional impairment. 1, 3, 4

Pearls to assess for an occult scapholunate dissociation

  • Perform a Watson’s scaphoid shift test. Production of a clunk or pop during radial deviation or after releasing scaphoid pressure indicates possible scapholunate instability.4 The movement is the scaphoid subluxing or relocating, respectively.

  • If you suspect this injury, obtain a clenched fist view or a PA view with the wrist in ulnar deviation to accentuate scapholunate dissociation.3
Due to proximity, a median nerve injury is common in lunate dislocation injuries.3,4

A lunate dislocation will likely require an orthopaedics or hand surgery consultation in the ED unless appropriately reduced and immobilized.

Overview on Lunate Injuries

  1. Scapholunate dissociation
  • Cock-up or volar wrist splint
  • Outpatient follow-up with an orthopedist or hand specialist within 1 week
  1. Perilunate or lunate dislocation
  • Consult an orthopedist or hand surgeon. Closed reductions are often unsuccessful.
  • If a specialist is not available, attempt closed reduction by applying traction, extending and ulnar-deviating the wrist to recreate the injury. Then perform carpal pronation, radial deviation, and wrist flexion.1
  • Indications for emergent surgery include:
    • Open dislocation
    • Median nerve involvement
    • Unsuccessful closed reduction

 

References

  1. Kennedy SA, Allan CH. In brief: Mayfield et al. classification: Carpal dislocations and progressive perilunar instability. Clin Orthop Relat Res. 2012;470(4):1243-1245. PMID 22322787
  2. Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: pathomechanics and progressive perilunar instability. J Hand Surg Am. 1980;5:226–241. PMID 7400560
  3. Williams D, Kim H. Wrist and forearm. In: Marx J, ed. Rosen’s Emergency Medicine Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier, Saunders; 2014: 570-595.e2
  4. Tsyrulnik A. Emergency department evaluation and treatment of wrist injuries. Emerg Med Clin N Am. 2015;33(2): 283-296. PMID 25892722

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Tabitha Ford, MD

Tabitha Ford, MD

Chief Resident
Department of Emergency Medicine
University of Utah
William Denq, MD

William Denq, MD

Sports Medicine Fellow
Department of Emergency Medicine
University of Utah
William Denq, MD

@willdenq

Sports Medicine Fellow Emergency Medicine University of Utah George Washington University '18 University of Pittsburgh '14 and '10