Perilunate instability - Mayfield classification of carpal instability

Mayfield et al. described in 1980 the following four stages of progressive carpal instability.

Stage Description
Stage I scapholunate dissociation: dorsal dislocation of the proximal scaphoid pole in the radiocarpal joint (rotatory subluxation of the scaphoid) with disruption of the dorsal scapholunate ligament leads to widened scapholunate distance (Terry Tomas sign) on radiograph
Stage II perilunate dislocation: midcarpal instability between the lunate and the capitate - the scaphoid and distal row complex dislocates dorsally relative to the lunate
Stage III midcarpal dislocation: fracture of the triquetrum or rupture of the lunotriquetral ligament
Stage IV lunate dislocation: palmar rotatory dislocation of the lunate into the carpal canal - "tipped teacup" appearance


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