Abstract
Introduction
Scaphoid fractures are commonly treated with a single headless screw. There are different recommendations regarding the optimal location of this screw. The purpose of this study was to compare the location of screws placed for the treatment of acute scaphoid fractures with theoretical and virtual screw locations.
Materials and Methods
10 patients with acute scaphoid fractures treated surgically and with available pre- and postoperative CT scans were included. The scans were analysed using a 3D software model (Amira Dev 5.3, Mercury Computer Systems, Chelmsford, MA). On the preoperative CTs the displaced fractures were virtually reduced. Possible screw locations for fracture fixation were examined including one along the central third of the proximal fragment (central base screw), the scaphoid longitudinal axis calculated mathematically (PCA screw) and a screw placed perpendicular to the fracture plane (90 degree screw). The angle between the axes and fracture plains were measured. The angle and distance between the actual screw on the postoperative CT and the different virtual screw locations were measured as well.
Results
The angles between the actual and virtual screws to the fracture plane were between a mean of 67 to 69 degrees. The angle between the axes was greatest between the 90 degree screws to the PCA and actual screws (mean 23 degrees both; p=0.034) and smallest between the central base screws and PCA to the actual screws (mean of 12.1 and 12.5 degrees, respectively; p=0.034). The difference between the entrance and exit points between the axes was between 3.1 to 4.8 mm other than the 90 degree screws which were 5.3 to 7.1 mm to the other axes (p=0.002). The PCA (mean 28.3 mm) were found to be longer than the actual screws (mean 25.4) or the 90 degree screws (mean 23.5) (p=0.034 and p=0.008 respectively). The 90 degree screws were shorter than the PCA or central base screws (p=0.008, p=0.034 respectively), but not the actual screws.
Discussion
There were no significant differences in the angles between actual and virtual optimal screws other than the 90 degree screws. The PCA was found to be the longest screw and at a similar angle to the fractures as the other virtual screw options, other than the shorter 90 degree screw. Virtual reduction and preplanning of the screw location, using standard software, may enable the surgeon to place the longest screw along the PCA longitudinal axis. If placing a 90 degree screw is considered, this may be technically difficult or may necessitate a trans-trapezial approach.
