ASSESSMENT OF DORSAL OR VENTRAL INTERCALATED SEGMENTAL INSTABILITY CONFIGURATIONS OF THE WRIST - RELIABILITY OF SAGITTAL MR-IMAGES

PURPOSE: To determine whether a dorsal intercalated segmental instabil ity (DISI) or ventral intercalated segmental instability configuration can be mimicked on sagittal magnetic resonance (MR) images in asympto matic subjects with unremarkable lateral radiographs. MATERIALS AND ME THODS: In 10 asymptomatic adult volunteers, capitolunate, scapholunate , and radiolunate angles were measured on lateral radiographs and comp ared with those measured on T1-weighted spin-echo MR images obtained i n neutrally positioned wrists with subtle variations in the sagittal i maging plane. MR measurements also were obtained in 15 degrees radiall y and 15 degrees ulnarly deviated wrists. RESULTS: In neutrally positi oned wrists, the mean capitolunate, scapholunate, and radiolunate MR a ngles were 13.6 degrees-14.5 degrees, 4.0 degrees-9.9 degrees, and 18. 0 degrees-20.3 degrees larger, respectively, than those on lateral rad iographs. In 15 degrees radially deviated wrists, the mean MR angles w ere similar to those on lateral radiographs. In 15 degrees ulnarly dev iated wrists, the mean MR angles were 32.3 degrees, 16.6 degrees, and 37.1 degrees larger than those on lateral radiographs. At MR imaging, a DISI configuration would have been diagnosed in four subjects with n eutrally positioned wrists and in eight subjects with ulnarly deviated wrists. CONCLUSION: The lunate appears more dorsally tilted on sagitt al MR images than on lateral radiographs, and a DISI configuration can be mimicked. Subtle errors in the selection of the imaging plane do n ot substantially influence measurements; however, wrist positioning is crucial.