Ulnolunate Distance and Lunate Height: Reliability Testing

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Many methods for measuring ulnar variance have been described. The purpose of thisstudy was to introduce the use of both lunate height and ulnolunate distance on the zero-rotation view as well as to assess the intra- and interobserver reliabilities of these measurements. The hypothesis was that the use of concave surfaces in the measurement of both lunate height and ulnolunate distance will yield a higher intra- and interobserver reliability than ulnar variance, which uses the convex surface of the distal radius. Seven hand fellows reviewed 32 radiographs. Measurements of lunate height, ulnolunate distance, and ulnar variance, using the method of perpendiculars, were recorded to the nearest 0.5 mm. Intraclass correlation coefficient (ICC) was then calculated for each radiograph for intra- and interobserver reliability. The ICC measurements were similar for lunate height, ulnolunate distance, and ulnar variance. The inter- and intraobserver reliability was similar for all 3 measurements. Measurements of ulnar variance utilize the concave surface of the distal radius. The use of the convex surface of the lunate and pole of the ulna does not seem to improve the reliability of these measurements. Further studies are necessary to confirm the clinical utility of these measurements. The use of ulnolunate distance and lunate height as an adjunct to ulnar variance may assist in evaluation of distal radius fractures and ulnocarpal abutment, improve surgeon communication, and contribute to our overall knowledge of the wrist.