CT-generated Radiographs in Obese Patients With Acetabular Fractures: Can They Be Used in Lieu of Plain Radiographs?

Background Acetabular fracture diagnosis is traditionally made with AP and oblique pelvic plain radiographs. Obesity may impair diagnostic accuracy of plain radiographs. New CT reconstruction algorithms allow for simulated radiographs that may eliminate the adverse imaging effects of obesity. Questions/purposes In obese patients with acetabular fractures, we compared CT-generated and plain radiographs in terms of (1) ability to classify fracture type, (2) agreement in fracture classification, and (3) surgeon performance at different experience levels. Methods CT-generated and plain radiograph image sets were created for 16 obese (BMI > 35) patients with 17 acetabular fractures presenting from 2009 to 2011. Three orthopaedic trauma attending physicians, three senior residents, and three junior residents independently viewed these sets and recorded their diagnoses. These diagnoses were compared to the postoperative findings, which we defined as the gold standard for diagnosis. To assess intraobserver reliability, the same observers reviewed a rerandomized set 1 month later. We had 80% power to detect a 25% difference in the percentage of correctly classified fractures based on a post hoc sample size calculation and 80% power to detect a 0.10 difference in κ value based on both a priori and post hoc sample size calculations. Results With the numbers available (153 observations in each image set, 51 for each of the three observer groups), we found no differences between CT-generated and plain radiographs, respectively, in terms of percentage of correct diagnoses for the observer groups (all observers: 54% versus 49%, p = 0.48; attendings: 61% versus 59%, p = 0.83; senior residents: 51% versus 53%, p = 0.84; and junior residents: 49% versus 35%, p = 0.16). Furthermore, agreement between CT-generated and plain radiographic fracture classifications was substantial (κ = 0.67). Nonetheless, the attending and senior resident groups performed better in correctly classifying the fracture than the junior residents when using plain radiographs (p = 0.01 and p = 0.049, respectively). Performance was not different when comparing the attendings to the senior resident and junior groups or comparing the senior residents to the junior residents using CT-generated radiographs (p = 0.32, p = 0.22, and p = 0.83, respectively). Conclusions CT-generated radiographs are as good as plain radiographs for experienced surgeons for classifying acetabular fractures in obese patients. CT-