Imaging differentiation of pathologic fractures caused by primary and secondary bone tumors

ObjectiveTo describe pre-treatment imaging features of pathologic fractures caused by primary bone tumors (PBTs) and metastatic bone tumors (MBTs) and determine if radiographic or cross-sectional features can differentiate the underlying pathologies associated with the fractures.MethodsSixty-nine patients with a diagnosis of a pathologic fracture were enrolled. Biopsy established PBT as the cause of the pathologic fracture in 16 (23%) cases and MBT in 53 (77%) cases. The radiographs, computed tomography (CT) scans, and magnetic resonance imaging (MRI) scans of the subjects were retrospectively reviewed for the presence of multiple imaging features.ResultsCompared to pathologic fractures caused by MBTs, the fractures caused by PBTs demonstrated a higher incidence of lytic bone cortex, mineralization and a soft-tissue mass on radiographs, mineralization and a soft-tissue mass on CT scans, and periosteal abnormality on MRI scans (P < 0.01). These features also exhibited a high negative predictive value in supporting the diagnosis of an underlying PBT over MBT.ConclusionPathologic fractures caused by PBT and MBT may be differentiated by a few specific radiographic and CT imaging features, though MRI was poor for characterization of the underlying lesion. Such knowledge may assist radiologists in raising the possibility of a PBT as the cause of a pathologic fracture.