SplintER Series: A Case of Traumatic Wrist Pain After Fall on Outstretched Hand

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