Unsuspected sacral fractures: detection by radionuclide bone scanning.

Unsuspected sacral fractures may present with confusing clinical, radiographic, and scintigraphic findings. Sacral fractures were diagnosed by radionuclide bone scans in 23 patients, most of whom were osteopenic and had only minor or no trauma. Symptoms usually consisted of low back pain, sometimes with radiculopathy, but some of the patients were asymptomatic and the fractures discovered coincidentally. Abnormalities on bone scanning consisted of increased uptake in the body of the sacrum and one or both sacral alae or only in a single sacral ala. A retrospective review showed abnormalities on radiographs in 11 of the 23 patients and in all four of the CT scans obtained, but the abnormalities were often overlooked or misinterpreted on the original reading. Bone biopsies of the sacrum, done in two patients to rule out metastatic disease, showed reactive bone formation consistent with fracture. Recognition of the characteristic scintigraphic patterns in sacral fractures and the frequency of these fractures in osteopenic patients can avoid mistaken diagnoses and unnecessary tests or treatment.