The Sigmoid Notch View for Distal Radius Fractures.

PURPOSE: This study defines the sigmoid notch view of the distal radius. Specifically, we tested the null hypothesis that there is no relationship between the subchondral stripe of bone seen on a sigmoid notch view of the distal radius and the articular surface of the sigmoid notch.

METHODS: We used 44 wrist specimens for anatomic and fluoroscopic analysis. We measured the articular depth of the sigmoid notch from its deepest point and classified the shape of the sigmoid notch. We then placed a radiopaque marker at the nadir of the articular surface and quantified the fluoroscopic depth of the sigmoid notch. A sigmoid notch view, which was a tangential fluoroscopic view of the volar and dorsal lips of the sigmoid notch, was obtained. The relationship of the articular surface to the stripe of subchondral bone seen on this view, called the sigmoid stripe, was determined.

RESULTS: Anatomic analysis revealed sigmoid notch types with proportions similar to those in previous descriptions. The marker for the articular surface was superimposed or just ulnar to the sigmoid stripe in all specimens. In flat face and ski slope notches, this was coincident with the volar and dorsal lips of the sigmoid notch. In C- and S-type notches, there was a measurable distance from the articular surface marker to the edges of the bone of the volar and dorsal lips of the sigmoid.

CONCLUSIONS: The articular surface marker at the nadir of the sigmoid notch is always coincident or ulnar to the sigmoid stripe in the sigmoid notch view.

CLINICAL RELEVANCE: Surgeons can use the sigmoid notch view as a reliable method to (1) evaluate the integrity of the articular surface, (2) ensure hardware is not placed in the distal radioulnar joint, and (3) guide placement of volar locking plates in the coronal plane.