Computer tomography aided 3D analysis of the distal dorsal radius surface and the effects on volar plate osteosynthesis.

The aims of this study were to measure the size of Lister's Tubercle, the extent of the extensor pollicis longus (EPL) groove and the dihedral angle of the distal dorsal radius. Computer tomography scans of 30 forearms were performed by using a 64-slice Siemens SOMATOM Sensation CT system (Resolution 0.6 mm). DICOM raw data were calculated to 3D by MIMICS software (Materialise, Leuven, Belgium). The size of Lister's Tubercle varied from 1.4 to 6.6 mm (average 3.3 mm) in height radial to the tubercle, and from 5.6 to 18.6 mm (average 13.2 mm) in length. The depth of the EPL groove varied from 0.6 to 3.2 mm (average 1.6 mm). The height on the ulnar side, between the depth of the groove and the tip of the tubercle, varied from 2.2 to 5.8 mm (average 3.4 mm). The dihedral angle of the distal dorsal radius varied from 110 degrees to 135 degrees (average 123 degrees). The variations in height of Lister's Tubercle and in depth of the EPL groove are considerable. This needs to be taken into account when performing volar plating of distal radius fractures otherwise screws may inadvertently penetrate the dorsal cortex of the radius potentially leading to EPL rupture.