Validity of computed tomography in predicting scaphoid screw prominence: a cadaveric study.

BACKGROUND

Studies of hardware protrusion into joint spaces following fracture fixation have been performed to address whether or not there is discrepancy between the actual and radiographic appearance of screw prominence. The purpose of our study was to prove that, with respect to the scaphoid, prominence as visualized on CT scan is real and not a result of metal artifact.

METHODS

Forty-two cadaveric wrists were separated into four allotted groups with 21 control specimens and 21 study specimens. All specimens were radiographically screened to exclude those with inherent carpal abnormalities. Acutrak® headless compression screws were placed into all specimens using an open dorsal approach. Cartilage was removed from screw insertion site at the convex surface of the scaphoid proximal pole. Control specimens had 0 mm screw head prominence. The studied specimens had 1, 2, and 3 mm head prominence measured with a digital caliper. Computed tomography, with direct sagittal acquisition and metal suppression technique, was then performed on all specimens following screw placement. Two staff radiologists blinded to the study groups interpreted the images.

RESULTS

Results revealed that only one of 21 control specimens was interpreted as prominent. Comparatively, in the studied groups, 90% were accurately interpreted as prominent.

CONCLUSIONS

CT provides an accurate assessment of scaphoid screw head prominence. When a screw appears prominent on CT scan, it is likely to be truly prominent without contribution from metallic artifact.