Three-dimensional imaging of the distal radius with reference to volar locking plate surgery

The watershed line is widely accepted as the distal limit of the volar locking plate (VLP); however, the VLP placement could vary depending on the plate contour and morphology of the distal radius. The aim of this study was to investigate the morphology of the distal radius and VLP fitting using 3D images.

We hypothesized that attachment of the VLP would affect the contour of the volar prominence of the distal radius.

Variable-angle LCP two-column volar distal radius Plate 2.4 and 16 formalin-fixed cadavers were studied. The plate and forearm were scanned using a computed tomography scanner. The plate was fixed to the radial shaft in the most distal position without flexor pollicis longus tendon contact. Postero-antero and lateral radiographs were obtained using fluoroscopy. Postero-antero radiographs were superimposed on a 3D image of the distal radius. The virtual plate was attached to the distal radius in the computer simulations and the plate was adjusted in the sagittal plane. In the postero-antero radiographs, the distance between the plate and distal end of the radius (DPR) was measured. In the sagittal plane, the height of the volar lunate facet (VLF) and the plate-to-bone distance of each locking screw hole was measured. The volar cortical angle (VCA) was measured as the angle formed by a line drawn along the volar surface and a line drawn on the radial shaft on the sagittal plane at each locking screw plane.

A significant correlation was observed between the height of the VLF and the DPR and between the height of the VLF and the VCA. The plate-to-bone distance at the ulnar screw hole was significantly smaller than that of the other screw holes.

Our study revealed that the higher the VLF, the more proximal is the VLP. The plate fits on the bone surface at the ulnar side, whereas the radial side has more space between the plate and bone.

III, diagnostic Level.