Differential diagnosis between metastatic and osteoporotic vertebral fractures using sagittal T1-weighted magnetic resonance imaging.

BACKGROUND: Magnetic resonance imaging (MRI) is the most helpful for determining the differential diagnosis between metastatic and osteoporotic vertebral fractures; especially whole spine MRI is effective if patients have multiple spinal metastases. However, it is time-consuming to obtain all planes for all metastatic vertebrae. If we can differentiate these metastatic and osteoporotic vertebral fractures based on only one section and signal intensity, it would save time and be effective for patients with pain. This study investigated the usefulness of sagittal T1-weighted MRI findings in differentiating metastatic and osteoporotic vertebral fractures. METHODS: We retrospectively reviewed patients diagnosed with metastatic or osteoporotic vertebral fractures. Findings characteristic of metastatic fractures were considered: (a) pedicle or posterior element involvement; (b) convex posterior border of the vertebral body; (c) epidural infiltration; and (d) diffuse homogeneous low signal intensity; findings characteristic of osteoporotic compression fractures were also considered: (e) low-signal-intensity band and (f) posterior retropulsion. Chi-square test or Fisher's exact probability test was used to investigate the usefulness of each MRI finding. Intra- and inter-observer reliability analysis was performed. RESULTS: This study comprised 43 patients with metastases (45 vertebrae) and 118 patients with osteoporotic fractures (156 vertebrae). All findings showed significant difference with each fracture (p-value: <0.01 to 0.03). Although each MRI finding exhibited high intra- and inter-observer reliability (κ: 0.66 to 1.00), finding (c) exhibited low reliability. Finding (a) showed high sensitivity (88.9%) and usefulness for screening, and findings (b), (d), (e), and (f) showed high specificity (90.4%-100%) and usefulness for definitive diagnosis. CONCLUSIONS: Characteristic findings with sagittal T1-weighted MRI were useful in the differential diagnosis of metastatic and osteoporotic vertebral fractures. To prevent overlooking metastatic fractures with sagittal T1-weighted MRI, findings of the pedicle or posterior element involvement should be focused on because of its reliability and sensitivity.