Mayfield classification of carpal instability, also known as perilunate instability classification (carpal dislocations), describes carpal ligament injuries.
Instability has been divided into four stages 1-2:
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stage I: scapholunate dissociation (rotatory subluxation of the scaphoid)
- disruption of the scapholunate ligament with resultant Terry Thomas sign
- exacerbated in clenched fist views
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stage II: perilunate dislocation
- the lunate remains normally aligned with the distal radius, and the remaining carpal bones are dislocated (almost always dorsally)
- the capitolunate joint is disrupted, and the lunate projects through the space of Poirier
- 60% are associated with scaphoid fractures
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stage III: midcarpal dislocation
- lunotriquetral interosseous ligament disruption or triquetral fracture
- neither the capitate or the lunate is aligned with the distal radius
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stage IV: lunate dislocation
- dorsal radiolunate ligament injury
- dislocation of the lunate in a palmar direction
- tipped teacup appearance
History and etymology
This classification was described by Mayfield et al. in 1980 1.