Assessment of dorsal or ventral intercalated segmental instability configurations of the wrist: reliability of sagittal MR images.

Abstract

To determine whether a dorsal intercalated segmental instability (DISI) or ventral intercalated segmental instability configuration can be mimicked on sagittal magnetic resonance (MR) images in asymptomatic subjects with unremarkable lateral radiographs. In 10 asymptomatic adult volunteers, capitolunate, scapholunate, and radiolunate angles were measured on lateral radiographs and compared with those measured on T1-weighted spin-echo MR images obtained in neutrally positioned wrists with subtle variations in the sagittal imaging plane. MR measurements also were obtained in 15 degrees radially and 15 degrees ulnarly deviated wrists. In neutrally positioned wrists, the mean capitolunate, scapholunate, and radiolunate MR angles 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 radiographs. In 15 degrees radially deviated wrists, the mean MR angles were similar to those on lateral radiographs. In 15 degrees ulnarly deviated 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 neutrally positioned wrists and in eight subjects with ulnarly deviated wrists. The lunate appears more dorsally tilted on sagittal MR images than on lateral radiographs, and a DISI configuration can be mimicked. Subtle errors in the selection of the imaging plane do not substantially influence measurements; however, wrist positioning is crucial.