Computed Tomographic Analysis of Screw Positions in Volar Percutaneous Screw Fixation of Scaphoid Fractures

ABSTRACT

PURPOSE: We analysed the position of screws whithin the scaphoid on computed tomographic images of patients treated by volar percutaneous screw fixation for scaphoid fractures. MATERIALS AND METHODS: We reviewed 16 patients treated by volar percutaneous screw fixations for scaphoid fractures. In three (proximal, middle, distal) portions of the scaphoid, the distance from the center of the screw to the edge of the cortex and the diameter of the scaphoid were measured on the sagittal and coronal reconstructive computed tomographic images. We divided into two groups the risk group with cortical breakage or penetration by the screw and the safe group with no cortical breakage. The position of screws was analysed and compared between two groups. RESULTS: The position of screws in the proximal scaphoid was more central than the distal scaphoid (p<0.05). The central screw placement in the distal scaphoid correlated with that in the proximal scaphoid. The average distance from the volar surface of the scaphoid tuberoisity to the entry point was 7.0 mm(5.0~8.8 mm) in risk group and 4.7 mm(1.5~7.6 mm) in safe group. It was differed significantly between risk group and safe group(p<0.05). CONCLUSION: This study suggests that volar percutaneous screw fixation for scaphoid fractures can achieve central screw placement in the proximal scaphoid. For the safe placement of the screw, a surgeon should be careful not to locate the entry point too far posteriorly on the scaphotrapezial joint.