Ulnar styloid impingement syndrome

Abstract

The tip of an excessively long ulnar styloid can impinge upon the triangular fibrocartilage complex (TFCC) against the triquetrum. The subtleties in biomechanics of the wrist joint and their role in the production of the symptoms are presented as five cases from a retrospective study. The relationship of the symptoms to the patients' job activities is also discussed. The embryological and anatomical studies show that the tip of the ulnar styloid is covered by the TFCC. Therefore, the term "ulnar styloid impingement syndrome" is adopted for the entity in cases in which the TFCC has remained intact.

Fig. 1

Coronal section of the right distal radio-ulnar joint; distal view in full pronation (top) and supination (bottom). The elbow is in 90 degrees of flexion with the arm at the side of the trunk. In full pronation, the ulnar styloid is located at 5 o’clock. In full supination, the radius rotates around the immobile distal ulna but the ulnar styloid remains at 5 o’clock

Fig. 2

Standard posterior-anterior (PA) radiograph of a normal right wrist; short ulnar styloid (top) and an excessively long ulnar styloid (bottom). The reduced distance between the tip of the ulnar styloid and piso-triquetral complex is noticeable in an excessively long ulnar styloid

Fig. 3

Standard posterior-anterior (PA) radiograph of a normal right wrist; the partially excised ulnar styloid (top), full pronation, ulnar deviation (middle) and full supination (bottom). In full pronation and ulnar deviation, the ulnar styloid mildly overlaps the piso-triquetral complex. In full supination and ulnar deviation, the stump of the ulnar styloid rotates away from the piso-triquetral complex. The apparently widened space between scaphoid and lunate was not clinically considered to represent scapho-lunate instability, since there was no history of prior injury to the wrist, symptoms or clinical objective finding referable to such condition