Missed sacral fractures.

During 1974 156 patients with pelvic fractures were admitted to our hospital. Of them 63 (40.4%) had double vertical lesions, which broke the pelvic ring in two sites. In 12 patients the diagnosis of a sacral hairline fracture was not made initially. The difficulties in making a radiological diagnosis are mainly due to the curved form of the sacrum in plain radiographs. The use of sophisticated radiological methods does not remove the difficulties. Double lesions were missed most often in elderly female patients with low-energy hairline fractures in osteoporotic sacra. The typical indirect signs observed in combination with sacral fractures were no help in the search for these missed hairline fractures, and the contribution of these fractures to the prediction of dangerous complications can be regarded as minimal.