Evaluation of Computed Tomography for Determining the Diagnosis of Acetabular Fractures

Objective: We assessed whether, in contrast to reports in the literature, computed tomographic (CT) scans improve the ability to classify acetabular fractures in comparison with plain radiographs. Design: Prospective. Setting: Level I trauma center. Patients: Seventy-five patients with 75 acetabular fractures treated between June 2005 and May 2006. Intervention: Four different image sets for each patient were evaluated: image set A, Judet view plain radiographs plus axial view CT scans; image set B, Judet view plain radiographs alone; image set C, three-dimensional CT reconstructions; and image set D, CT-simulated anteroposterior and Judet views of the pelvis. The 300 image sets were viewed in random order by four orthopaedic trauma fellowship-trained surgeons who independently recorded a diagnosis. A gold standard diagnosis was determined by group consensus. Main Outcome Measurements: Agreement among four imaging methods was evaluated by using kappa statistics for multiple raters and nominal data. Results: Comparing the gold standard diagnosis with the four image sets, Judet view plain radiographs had a worse kappa value than CT scans (P < 0.05). The adjusted kappa values for all three image sets that included CT scans averaged greater than 0.62, showing substantial agreement, whereas the image set with plain radiographs alone (image set B) had a lower kappa value of only 0.48 (P < 0.05). Conclusions: In contrast to previous reports in the literature, the accuracy of plain radiographs alone was less than the accuracy of CT scans in terms of diagnosis. The interobserver reliability was also worse for plain radiographs alone.