Does the Axis of Screw Placement Determine Outcomes in Percutaneous Fixation of Acute Scaphoid Fractures?

The ideal axis for screw placement in scaphoid waist fracture fixation is still controversial. Central screw placement can be technically challenging because of the scaphoid anatomy, surgical approach used for fixation and the patient’s body habitus. Perpendicular placement of screw to oblique fractures is considered to have equivalent strength to that of the centrally placed screw with additional advantage of using shorter screw for fixation .However this fixation cannot be achieved by standard approaches to scaphoid. Hence this study was undertaken to determine if variable screw fixation trajectories to the scaphoid waist fracture geometry achieved during surgery, influences the fracture union in percutaneous fixation of scaphoid waist fractures. 

Plain radiographs of scaphoid waist fractures fixed by percutaneous headless compression screw  by volar or dorsal approach were analysed for fracture pattern, direction of screw placement from distal half (radial /ulnar /central in PA view & volar/dorsal/central in lateral view) to proximal half of scaphoid (radial /ulnar /central in PA view & volar/dorsal/central in lateral view) or vice versa, angle of the screw to the fracture line and to longitudinal axis of scaphoid, length of screw and time taken for fracture union. 

27 plain radiographs which fulfilled the inclusion criteria were analysed. 5 scaphoid fractures were fixed along its central axis, 5 perpendicular to the fracture line and 20 with variable screw trajectories to the fracture line. The average screw length was found to be 22mm. Union was observed in all cases and the average time to union was 8 weeks. Union status of scaphoid fracture was independent of screw length and direction of fixation and was statistically proven. 

In this study, it was found that various trajectories of screw placement did not determine the rate of union or the time taken for union in percutaneous fixation of scaphoid waist fractures.