Computed tomography assessment of sacroiliac screw placement relative to the first sacral neuroforamen

The radiographic interpretation of sacroiliac screws relative to the S-1 ne uroforamen is difficult for orthopedic surgeons and radiologists. Computed tomography (CT) with axial images alone or combined with multiplanar recons tructions are often used to assess screw position. The reliability, reprodu cibility, and accuracy of orthopedist and radiologist interpretations of ax ial CT images with and without multiplanar reconstructions was determined u sing 24 cadaveric hemipelves with known sacroiliac screw position. Interobs erver reliability of determining screw position was fair for orthopedists a nd slight for radiologists regardless of imaging modality or screw composit ion. Intraobserver reproducibility was moderate for orthopedists regardless of imaging modality or screw type. Reproducibility among radiologists was moderate using axial images of titanium screws and substantial with additio n of multiplanar reconstructions. Overall accuracy was similar for orthoped ists and radiologists. CT images with multiplanar reconstructions improve a ccuracy in determining sacroiliac screw position. but not significantly. Cu rrent imaging modalities are limited by large inaccuracies and by interobse rver and intraobserver variation.