Ulnar styloid triquetral impaction.

Background: Ulnar styloid triquetral impaction (USTI), one of many causes of ulnar sided wrist pain, is a pathological entity with clear clinical and radiographic features, distinct and different from the impaction of the ulnar head against the lunate or ulno-carpal impaction (UCI). Pain is ulnar and point-tenderness is present precisely over the ulnar styloid as opposed to the proximal lunate in UCI. The provocative maneouvre of dorsiflexion in pronation followed by supination is markedly different from the ulnar deviation grind test maneouvres used to diagnose UCI. Multiple anatomical and pathological features interplay to produce a situation in which the distance between the tip of the ulnar styloid and the triquetrum is reduced resulting in USTI. The concept of ulnar styloid variance is introduced and anatomical variations of ulnar styloid length are demonstrated.

Methods: The clinical and radiographic features of 56 patients diagnosed with USTI were analysed. One thousand standardised film-file wrist radiographs were measured to determine the average length of the ulnar styloid in the population as well as the average projection of the styloid above the radius (ulnar styloid variance).

Results: An aetiological classification system for USTI was developed based on the clinical and radiographic features of the aforementioned patients and radiographs.

Conclusions: The causes of this syndrome are often complex and classification of the aetiological features is clinically useful. It is important for physicians and surgeons to recognise the clinical and radiographic features of this syndrome in order to properly manage the symptoms and prevent an iatrogenic production of USTI.