The Watershed Line of the Distal Radius: Cadaveric and Imaging Study of Anatomical Landmarks

Abstract

Background Placement of volar plates remains a challenge as the watershed line may not be an easy-identifiable distinct line intraoperatively. Objectives The main objective of this article is to define how anatomical landmarks identifiable upon the volar surgical approach to the distal radius relate to the watershed line. Methods We identified anatomical landmarks macroscopically upon standard volar approach to the distal radius in 10 cadaveric forearms and marked these with radiostereometric analysis (RSA) beads in cadaveric wrists. The RSA beads were then referenced against the volar osseous structures using quantification of three-dimensional computed tomography and advanced imaging software. Results The mean measurements were the radial and ulnar prominences 11.1 mm and 2.1 mm proximal to the joint line of the distal radius, respectively. The interfossa sulcus was 0.3 mm proximal and 3 mm dorsal to the ulnar prominence. The watershed line was between 3.5 (minimal) and 7.6 (maximal) mm distal to the distal line of insertion of the pronator quadratus. Conclusion The watershed line is situated distal to the pronator quadratus, but with a wide variability making it an impractical landmark for plate position. The osseous ulnar prominence is a good anatomical reference for safe plate positioning, as it is located on the watershed line and easily palpated at surgery. One should keep in mind the sulcus—the point on the watershed line where the flexor pollicis longus runs—can be situated just proximal to the ulnar prominence. Clinical Relevance To provide anatomical landmarks that are easy to identify upon surgical approach without the direct need for intraoperative imaging.

Volar fixed plating of distal radius fractures: optimizing plate position for enhanced clinical outcomes

“…When the literature is evaluated, there are still ongoing discussions about the watershed line [ 24 , 25 ]. Many anatomical and cadaveric studies attempt to describe the exact watershed area [ 6 , 26 ].…”

A radiographic study of dorsovolar wrist axes and a database of angular measurements on axial computed tomography images

“…The principal axes of the wrist on axial CT sections are used as a reference in studies for following conditions: the distal radius anatomy, [1,4,8,15] rotational malalignment due to distal radius or shaft fractures, [7,9,16] anatomic and kinematic studies of the carpal region, [5,6,10] and DRUJ anatomy. [5,11,12,[17][18][19] Several anatomical locations have been used as principal axis of the distal radius in the past, including, the central axis, [4,[7][8][9]11,12,16] volar cortical axis at metaphyseal level, [5,8,9] and sigmoid notch axis. [5] In the current study, a series of angular measurements based on axial CT images provided improved data for evaluating radiographic anatomy of the wrist.…”

“…The principal axes of the wrist on axial CT sections are used as a reference in the anatomical, kinematic, and clinical studies in patients with different conditions such as distal radius malunion, distal radioulnar joint (DRUJ) instability, and scapholunate ligament injury. [1,[4][5][6][7] However, available data are problematic due to the different landmarks and principal axes preferred for reference. Several different anatomical locations have been used as a principal axis of the distal radius in the past; the central (mediolateral radiocarpal joint) axis, volar cortical axis (at distal metaphyseal level), and sigmoid notch axis.…”

Arthroscopic-assisted Distal Radius Fracture Fixation for Dorsoulnar Corner Fragments Using a Locked, Hooked Kirschner-Wire Technique

“…17 A volar locking plate is sized and applied to the radial volar cortex, proximal to the watershed line if appropriate to reduce tendon irritation. 8,18 Fluoroscopy is used to confirm plate position and early reduction in the coronal and sagittal planes and once satisfactory, the proximal shaft screws are inserted.…”