The DRUJ is the distal pivot of forearm rotation, complementing the proximal radioulnar joint at the elbow. The concave sigmoid notch of the radius rotates around the convex ulnar head, stabilised by the TFCC (the primary stabiliser) and the dorsal and palmar radioulnar ligaments. Ulnar variance (the length of the ulna relative to the radius) strongly influences load through the joint and the TFCC. DRUJ instability from distal radius fracture malunion or TFCC disruption produces a prominent ulnar head and painful, limited forearm rotation.
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DRUJ instability is assessed by the piano key test (dorsal pressure on the ulnar head in pronation and supination), ballottement of the ulnar head and the press test (pain on pushing up from a chair with the wrist loaded). Wrist arthroscopy is both diagnostic and therapeutic for TFCC tears, and peripheral tears can be repaired back to the ulnar fovea. Chronic instability is treated by radioulnar ligament reconstruction (Adams-Berger procedure). Positive ulnar variance can cause ulnocarpal impaction, with central TFCC wear and lunate and triquetral cartilage damage, treated by ulnar shortening osteotomy or an arthroscopic wafer procedure. The Darrach procedure (ulnar head resection) and Sauve-Kapandji procedure (DRUJ fusion with a distal ulnar pseudarthrosis) address chronic DRUJ arthritis.
TFCC disruption or radius malunion producing a prominent ulnar head and painful forearm rotation, managed with TFCC repair or radioulnar ligament reconstruction.
Tear of the TFCC from its foveal attachment after a fall or forced rotation, causing ulnar-sided wrist pain, clicking and DRUJ laxity; arthroscopic repair is preferred for acute instability.
Positive ulnar variance overloads the TFCC and the ulnar carpus, causing ulnar wrist pain; managed by ulnar shortening osteotomy or arthroscopic wafer resection when conservative care fails.
