Blunt pelvic traumata are common injuries especially among elderly patients. It is well known, that standard x-ray diagnostics fail to detect all fractures. We set up a retrospective study to gain a profound knowledge of the actual informative value of a single, plain a.p. pelvic radiograph in these injuries for detecting acetabular and proximal femoral fractures as a standardized starting point in the radiologic work-up. We analysed the radiological reports, all validated by a board certified radiologist, for patients aged 75 years and older who had a blunt pelvic trauma and had both a standard a.p. pelvic x-ray and pelvic CT scan in the emergency department over a 3-year period. In 233 patients aged 75 years and older, we found 35 acetabular fractures. The calculated specificity of the plain x-ray was high (97.3%), but sensitivity was rather low (66.6%). The positive and negative predictive value were 85.7% and 92.4%, respectively. The number of proximal femur fractures found in CT was comparable (n = 46; prevalence 19.8%). The calculated sensitivity was 82.6%, specificity 93.0%, positive predictive and negative predictive values were 74.5% and 95.6%. We thus recommend the a.p. radiograph as the first step in the diagnostic pathway. But according to the crucial clinical assessment, a CT scan should be obtained whenever in doubt of the reliability of the plain x-ray, especially in elderly patients.
anterior pelvic ring; imaging; proximal femur fracture; acetabular fracture; sensitivity