The Parallelogram Effect: The Association Between Central Band and Positive Ulnar Variance.

Purpose: Ulnar impaction syndrome is a poorly understood degenerative wrist condition characterized by symptoms of pain thought to be caused by increased loads between the ulnar head and the carpals. Radiographic evaluation often reveals an ulnar-positive wrist. We hypothesize that progressive elongation of the central band of the forearm interosseous ligaments changes the longitudinal radial-ulnar relationships, resulting in an ulnar-positive wrist.