Scapholunate Dislocation-Plain Film

10 yr old child with history of fall and dorsal scapholunate tenderness  shows  loss of prescaphoid fat planes , increased scapholunate distance  with possible lunate extension and scaphoid flexion, suggesting scapholunate instability. Stress view with traction applied to thumb (5Kg) and other side comparison would help.

Teaching points  by Dr MGK Murthy.

·         Scapholunate instability is  most common and most significant carpal instability.  Predisposition occurs in negative ulnar variance, radial articular surface sloping, and lunotriquetral coalition.  Dorsal scapholunate tenderness is the clinical sign  for suspicion

·         Labeled chronic(>6wks), subacute(1-6weeks), and acute(<1week), with delayed diagnosis leading to Scapho Lunate Advanced Collapse (SLAC)

·         Resting PA wrist  is suggestive  -scapholunate gap is> 3mm =suspicious and if >5mm= diagnostic (Terry Thomas sign) , scaphoid ring sign(distance between proximal edge of the ring to the ulnar corner of scaphoid is <7mm),Traingular shaped lunate(extended),reduction in carpal height ratio( <0.54)

·         Lateral X –ray ----scapholunate angle >60 degrees is probable, >80 degrees is definite, lunate extended, lunocapitate angle >15 degrees

·         If  routine x -rays  negative, stress views –ulnar deviation PA  or AP clenched fist views would help

·         Some advocate dynamic  thumb traction(5Kg) and fluoroscopic spot film, to see increased SL distance or difference of more than 1mm  with resting view

·          Conventional /MR Arthrogram would help with Arthroscopy as gold standard