Scapholunate dissociation: MRI

Case Report :  23 yr old lady  with clinical  scapholunate  dissociation  on MRI shows ill definition of scapholunate ligament (volar  component more than others) with oedema/ ill definition of radio lunate ligament   substantiating the  clinical  diagnosis.

Teaching points by Dr MGK Murthy, MRI technician:Mr Rammurti

1.Scapholunate dissociation results from the scapholunate ligament disruption/ injury  with  more important  dorsal component  , 3 mm  thick(short, transversely oriented collagen fibers)/

volar component ( 1mm  thick) ,intermediate component  (fibrocartilage)  meniscus shape 

2.  Injury to  scapholunate ligament (complete tear of the dorsal component) and radiolunate ligament will result in scapholunate dissociation.  Mayfield et al. have proposed a 4 stage process to describe perilunar wrist instability where scapholunate dissociation represents stage 1 .

3 Most responsible  for SLAC (Scapho Lunate Advanced Collapse) (capitate stationed between scaphoid and lunate ). Present late and Xray may show Terry Thomas sign on AP with widened Scapho lunate distance ( more than 4mm)  / Rotation of scaphoid to make it look end on = signet ring.  Surgery is  effective to prevent SLAC