Ulnar Variance

Normal ulnar variance

• 80% of load goes to the radius

 

This X ray shows :

Positive ulnar variance

• In +2.5mm of ulnar variance 60% of load goes to radius while 40% goes though ulna.
• It leads to ulnar sided wrist pain from increased impact stress on the lunate and triquetrum.
• associated conditions include  
  • Ulnar impaction syndrome
  • SLD
  • TFCC tears
  • Lunotriquetral ligament tears

This X ray shows :

 

In -2.5mm of ulnar variance, 95% of load goes through radius and 5% of load goes through ulna

• It is commonly associated with Kienbock’s disease

 

 

Imaging

Method to determine ulnar variance   requires PA radiograph w/ wrist in neutral supination/pronation and zero rotation from the PA view draw two lines one tangential to the articular surface of the ulna and perpendicular to its shaft the other tangential to the lunate fossa of the radius and perpendicular to its shaft. measure the distance between these two lines. If the ulnar tangent is distal to the radial tangent there is positive ulnar variance, if it’s proximal there is negative ulnar variance.  Normal is 0mm.