Purpose of the study: The aim was to evaluate the diagnostic value of plain X-ray images in the diagnosis of pelvic ring injury in comparison with CT findings.
Material and methods: The group evaluated consisted of 30 patients, 11 women and 19 men, at an average age of 46 years (range, 20-81 years; women, 20-68 years, men, 20-81 years; average age, 49 and 44 years in women and men, respectively) in whom plain radiography and CT scans were done as part of the initial examination. A retrospective assessment of plain X-ray images was carried out by two independent specialists (radiologist and trauma surgeon). The authors together evaluated CT scans and carried out the final assessment of all medical records. Pelvic radiography was taken with a mobile X-ray unit; CT scans were done according to the standard trauma scanning protocol, using a CT scanner with either one row (CT) or 16 rows (multidetector/MDCT) of detectors.
Results: Based on the evaluation of X-ray and CT findings, a total of 133 fractures or displacements in the sacroiliac joint or pubic symphysis were detected. The radiologist identified 99 (74 %) injured structures and the trauma surgeon 111 (83 %) ones. This difference was not significant on the whole (p = 0.536), nor when individual structures were assessed. False negative findings were made by the radiologist on 10 occasions and by the trauma surgeon on seven occasions; the evaluation of image data sets by both observers was associated with only one false positive finding. The overall sensitivity of plain X-ray images, when compared to CT scans, was 83 %, but it was considerably lower on evaluation by one observer only (radiologist, 67 %; trauma surgeon, 78 %).
Discussion: The biggest difference between the findings of two independent specialists existed in the assessment of injuries to the posterior ring of the pelvis (SI joint, sacrum) on plain X-ray images. However, trauma in this region was identified without any doubt on CT scans. To diagnose the type of pelvic injury from CT scans without a possibility to evaluate standard anteroposterior (AP) radiographs or good-quality 2D or 3D reconstructions was found difficult in over one third of the patients. A validity comparison of standard AP radiography and high-quality 2D or 3D CT reconstructions showed that both had an equal value for the exact detection of pelvic injury type. For correct evaluation of the type of injury, scans from the MDCT were easier to read than those from the CT scanner.
Conclusions: There is no doubt about the role of standard AP X-ray in the identification of pelvic injury type in polytraumatized, hemodynamically unstable patients. The validity of CT examination for identification of injury to the posterior ring of the pelvis in particular is so high that, in the primary diagnostic procedure, inlet and outlet radiography of the pelvis has lost its importance. The information on the stability and type of injury provided by 2D and 3D CT reconstructions is so exact that, at present, CT examination can reliably replace AP radiography, particularly if, for various reasons, good-quality X-ray images cannot be guaranteed.