Chondromalacia at the ulnar head, ulnar side of the lunate and the radial side of the triquetral bone. Small focus of increased signal is seen in the triangular fibrocartilage suspicious for a small central tear. Findings are suggestive of ulnolunate impaction. Fluid is seen in the sheath of the extensor carpi ulnaris suggestive of tenosynovitis. 

Ulnolunate impaction syndrome.

Ulnar impaction syndrome, also known as ulnar abutment or ulnocarpal loading, is a degenerative condition characterized by ulnar wrist pain, swelling, and limitation of motion related to excessive load bearing across the ulnar aspect of the wrist. Chronic impaction between the ulnar head and the TFC complex and ulnar carpus results in a continuum of pathologic changes- degenerative tear of the TFC; chondromalacia of the lunate bone, triquetral bone, and distal ulnar head; instability or tear of the lunotriquetral ligament and finally, osteoarthritis of the ulnocarpal and distal radioulnar joints. 

Treatment of symptomatic ulnar impaction is complex in that it varies with the amount of ulnar variance, the Palmer lesion class (of TFCC), the shape of the sigmoid fossa and ulnar seat and the presence of concomitant lunotriquetral instability. Briefly, patients with no TFC perforation are managed with an open wafer procedure which consists of surgical resection of the distal most 2–3 mm of the dome of the ulnar head or formal ulnar shortening (ie, excision of a slice [generally 2–3 mm wide] of the ulnar shaft followed by rigid fixation). When the TFC is already perforated the head of the ulna can be burred down with the help of arthroscopic instrumentation (arthroscopic wafer procedure). This procedure is minimally invasive, highly effective, and allows rapid return to normal activities. More advanced cases are managed with salvage procedures such as complete or partial ulnar head resection (Darrach procedure and similar procedures) or arthrodesis of the distal radioulnar joint with distal ulnar pseudoarthrosis (Sauve-Kapandji procedure).

CLINICAL HISTORY: Intermittent right wrist pain with tenderness over ulna since accident one month ago.
No evidence of fracture on a plain radiograph.  REFERENCES RadioGraphics 2002; 22:105–121