Morphometric Variations of Scaphoid and Safety of Screw Fixation for Its Waist Zone Fractures in Indian Population: A Preliminary Report

Purpose: Surgeons fixing scaphoid fractures need to be familiar with their morphological variations and their implications for safe screw placement during fixation. The purpose of this computed tomography (CT)-based study was to analyze the anatomical limits of safe screw placement for scaphoid waist fractures in the Indian population. Methods: We measured the coronal and sagittal dimensions of the scaphoid in 3 zones: proximal, waist, and distal, in CT scans of wrists with intact scaphoids obtained from 50 live subjects. In addition, we studied the curvature of the scaphoid, its longitudinal extent, and the safe placement of trajectories for different screw diameters. Results: The proximal segment had the narrowest mean coronal width of 6.39 mm, whereas the waist region had the narrowest mean sagittal width of 9.02 mm. Mean scaphoid curvature was 132.23°. Maximal bony extent of the scaphoid was significantly higher than the mean length of screw placed centrally in the mid-waist region. Conclusions: This study showed that there is a considerable amount of variation in scaphoid morphometry in Indian patients. All scaphoids capable of safely containing a single 4-mm screw or 2 parallel 1.7-mm screws coplanar in the sagittal plane. Surgeons treating these fractures should consider a CT-based analysis to plan the screw direction and length and need to be familiar with the morphometric variations of the scaphoid. Clinical relevance: The measurements and techniques in this study may be helpful in understanding morphometric variations of the scaphoid and in planning surgery for fixation of fractures around its waist region. Key words: scaphoid curvature, scaphoid morphometry, scaphoid screw, screw trajectory, waist fractures