PURPOSE: Nonanatomic reduction of the sigmoid notch in distal radius fractures may lead to limited motion, instability, or pain with pronation and supination. Standard radiological projections only poorly capture the sigmoid notch contours in the axial plane. The purpose of this study was to find an intraoperatively feasible radiological projection that will facilitate an axial view of the distal radioulnar joint.
METHODS: We modified a previously described radiographic projection termed the skyline view for evaluating the distal radius axially. We created intra-articular steps at the sigmoid notch in solid foam forearm models to identify the best of 12 projections using an image intensifier. Four observers scored each projection based on the clarity of the sigmoid notch contour and indicated the presence and location of an intra-articular stepoff.
RESULTS: The sigmoid notch was best visualized in the modified skyline view with the wrist in extension and 10° to 15° of dorsal forearm angulation relative to the x-ray path. All observers correctly recognized the presence and location of intra-articular steps at the sigmoid notch with this view. The same forearm angulation with the wrist in flexion did not reach equally good visibility of the sigmoid notch. Arm position (wrist flexion, forearm rotation, or forearm angulation) and intra-articular stepoff (none, palmar, or dorsal) were dependent determinates. Elimination of the variable forearm rotation had minimal effect, indicating that forearm rotation is not important for visualization of the sigmoid notch.
CONCLUSIONS: The modified skyline view for visualization of the distal radioulnar joint in an axial plane allows good visibility of the sigmoid notch and reliable identification of stepoffs. Further cadaver and in vivo studies are required to verify the validity of this method.