Quantitative Analysis of the Volar Ulnar Corner of the Distal Radius: A Reference for Intraoperative Distal Radius Fracture Reduction.

PURPOSE: The reduction of distal radius fractures using volar locking plate fixation can be performed by securing the plate to the distal fragments and then levering the plate to the radial shaft. Oblique placement of the plate on the radial shaft may lead to malreduction. The aim of this study was to evaluate parameters that can be used for the assessment of intraoperative distal radius fracture reduction using "distal-first" volar plate fixation, especially the geometry of the ulnar corner. The prevalence of Tolat distal radioulnar joint (DRUJ) types was determined, and the angles of the volar corner were quantitatively described. METHODS: Three hundred seventy-five adult patients with a conventional wrist radiograph in their medical chart were identified. From this cohort, 50 radiographs of each Tolat DRUJ type were quantitatively analyzed using 4 angles. The probability density of each angle was described using Kernel density estimation graphs. A multivariable analysis was used to study the association between the 4 angles and Tolat DRUJ types and other patient factors. RESULTS: One hundred fifty-one patients (40%) had a wrist with type 1 DRUJ, 147 (39%) had a wrist with type 2 DRUJ, and 77 (21%) had a wrist with type 3 DRUJ. The measurements of the distal ulnar corner, volar ulnar corner, and DRUJ angulation were significantly different among each Tolat DRUJ type. The median lunate facet inclination, relative to the axis of the radial shaft, measured 14° (interquartile range, 12°-16°) across all the Tolat DRUJ types. CONCLUSIONS: The prevalence of Tolat type 1, 2, and 3 DRUJ was 40%, 39%, and 21%, respectively. The angles of the volar ulnar corner varied with each DRUJ type. CLINICAL RELEVANCE: Because the lunate facet inclination was relatively consistent among all the Tolat DRUJ types, this angle may be useful as a reference for "distal-first" distal radius volar plating.