Ulnar variance (also known as Hulten variance) refers to the relative lengths of the distal articular surfaces of the radius and ulna.
Ulnar variance may be:
- neutral (both the ulnar and radial articular surfaces at the same level)
- positive (ulna projects more distally)
- negative (ulna projects more proximally)
Variance is independent of the length of the ulnar styloid process.
- trauma or mechanical
- Madelung deformity/reverse Madelung deformity
- positive ulnar variance is associated with ulnar impaction syndrome.
- negative ulnar variance is associated with Kienbock disease and ulnar impingement syndrome
Ulnar variance changes with wrist position (more positive with maximum forearm pronation and negative with maximum forearm supination) and increases significantly during a firm grip .
To determine ulnar variance on radiographs, the generally accepted standard view is a posteroanterior view obtained with the wrist in neutral forearm rotation, the elbow flexed 90° and the shoulder abducted 90°.
Positive variance occurs when the level of the ulna is >2.5 mm beyond the radius margin at the distal radio-ulnar joint. Negative variance is when the ulna is ≤2.5 mm than the radius at the DRUJ .
MRI can estimate, but cannot reliably quantify, the degree of ulnar variance because the specific wrist position usually cannot be duplicated with MR imaging.