Purpose of the study: Percutaneous screw fixation is widely used for the treatment of non-displaced fresh fractures of the carpal scaphoid. This screw fixation can be achieved either via a volar approach (retrograde insertion) or via a dorsal approach (antegrade insertion). The purpose of our study was to define the best approach as a function of the orientation of the fracture line (types B1 or B2 in the Herbert classification).

Material and methods: We used 12 upper limbs. For each wrist we obtained three scanner images: in maximal flexion, in the neutral position, and in maximal extension. For each scanner image, the parasagittal slice corresponding to the ideal plane for screw position was identified by digital reconstruction. On each slice, the type B1 and B2 fractures were modellised, as was the displacement of the corresponding screws introduced via the volar incision (S1) or the dorsal incision (S2). Each virtual screw was positioned as perpendicular as possible to the fracture line. For each slice corresponding to a given wrist position, we measured the angles between the fracture line (B1, B2) and the screws (S1, S2), giving four angles V1 (S1-B1), V2 (S1-B1), D1 (S2-B1), D2 (S2-B2). Thus the angle closest to 90° was considered the most satisfactory.

Results: For B2 fractures, the position of the virtual screw perpendicular to the fracture line was possible via both the volar and the dorsal incision. For B1 fractures, it was impossible to position the screw perpendicular to the fracture line, but the dorsal approach with the wrist in maximal flexion gave the best position.

Conclusion: For B2 fractures, the dorsal and volar approach allow optimal screw insertion so the choice of the incision depends on the surgeon’s experience. For B1 fractures, we recommend the dorsal approach.