The volar extension of the lunate facet of the distal radius: A quantitative anatomic study

Purpose: To describe quantitatively the protrusion of the volar part of the lunate facet of the distal radius articular surface anterior to the volar metaphyseal cortex, which is susceptible to fracture and can be difficult to control with plates and screws alone. Methods: Quantitative anatomic measurements of 48 3-dimensional computed tomography scans of the distal radius were analyzed to quantify the anatomy of the volar part of the lunate facet of the distal radius. The measurements were scaled to account for overall bone size. Male and female anatomies were compared. Results: The height and width of the volar extension of the lunate facet were 3 +/- 1 mm and 19 +/- 4 mm, respectively. The mean height of the lunate facet was 19 +/- 3 mm. An average of 16% of the lunate facet projects anterior to the flat volar surface of the distal radius. The thickness of the volar extension of the lunate facet averaged 5 +/- 1 mm. There were no statistically significant differences between men and women for any of the scaled measurements. Conclusions: The observation that the volar lunate facet projects approximately 3 mm (or 16% of the dorsal-volar height of the lunate facet) anterior to the flat volar surface of the distal radius and is approximately 5 mm thick helps explain its relative vulnerability to injury and the difficulty encountered when trying to secure it with a plate and screws.