In-vivo three-dimensional measurement of distal radioulnar joint translation in normal and clinically unstable populations.

UNLABELLED: Assessment of distal radioulnar joint instability is clinically difficult and subjective. The distal radioulnar joint is postulated to 'tighten' in ulnar/radial deviation and pronation/supination. Using a rig, we measured mean distal radioulnar joint translation in neutral forearm rotation and neutral wrist radial and ulnar deviation, as well as extremes of wrist radial and ulnar deviation and forearm rotation. We tested the rig on ten cadaver forearms to validate the measurements we made. We tested 50 normal adults and 50 patients with clinical distal radioulnar joint instability. Distal radioulnar joint stability in men and women and on contralateral sides were comparable. Distal radioulnar joint translation decreased significantly with wrist radial and ulnar deviation and forearm pronation and supination, matching clinical practice and further validating the rig. The data in normal patients is comparable with previous computed tomography-based studies. Translation in all positions was statistically increased within the clinical instability group and did not cross-over with the normal ranges. Distal radioulnar joint translation is a physically measurable phenomenon. Our device appears to be a valid test of distal radioulnar joint translation, establishing normal data in vivo. LEVEL OF EVIDENCE: III.