Ulnar impaction syndrome is a common cause of ulnar-sided wrist pain that eventually leads to arthritis of the lunotriquetral joint. Ulnar impaction syndrome results from increased loading of the ulnocarpal articulation and usually is associated with a positive ulnar variance. The increased loading of the ulnocarpal joint leads to degeneration and perforation of the triangular fibrocartilage complex (TFCC). Chondromalacic changes develop on the opposing surfaces of the lunate and triquetrum distally and the ulnar head proximally. A disruption of the lunotriquetral ligament follows, with lunotriquetral arthritis the end result. The condition first was described by Milch [1] as a cause of wrist pain after malunion of a radius fracture; various terms since have been used to describe this symptom complex, including ulnocarpal abutment, ulna abutment, ulnocarpal impingement, and ulnar carpal loading. Ulnar impingement is a different clinical condition that is seen after excision of the distal ulna and results from the impingement of the ulnar stump against the radial shaft [2].
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