Abstract
Introduction
Getting the distal locking screw lengths right in volar locking plate fixation of distal radius is crucial. Long screws can lead to extensor tendon ruptures whereas short screws can lead to failure of fixation, especially if there is dorsal comminution of the fracture. The aim of our study was to determine the distal radius anatomy in relation to sagittal lengths and distance between dorsal bone edge and extensor tendons based on MRI scan.
Method
One hundred consecutive MRI scans of wrist were reviewed by two of the authors on two occasions. All MRI scans were performed for different wrist pathologies except distal radius fractures or tumours. An axial image, two cuts proximal to the last visible articular surface, was selected. Sagittal length at 5 different widths, maximum volar width, radial overhang over distal radio-ulnar joint and the distance between dorsal bone edge and extensor tendons were measured.
Results
A total of 120 MRI scans were included of which 74 were women and 46 were men. Mean volar width was 32mm and longest sagittal length was 22 mm (at Lister's tubercle). Length radial to Lister's tubercle was the shortest (17mm) and ulnar sides were 21mm and 29mm. Male measurements were mean 3mm longer than females. Mean radial overhang over DRUJ was 4mm. Distance from bone to tendons was within 2mm of dorsal radius edge.
Conclusion
The study provides a reference guide to average screw lengths at different widths of distal radius in males and females. EPL tendon is closest to bone although all the extensor tendons are within 2mm of bone edge and carry a risk of injury from drill and screw placement. DRUJ is also at risk of injury if screws are placed within 4mm of ulnar edge of distal radius.
