Hybrid Bone Single Photon Emission Computed Tomography Imaging in Evaluation of Chronic Low Back Pain: Correlation with Modic Changes and Degenerative Disc Disease

BACKGROUND AND OBJECTIVE: Multiple radiologic modalities are used in the evaluation of patients with low back pain (LBP). Only limited evidence currently exists to support the use of bone hydroxydiphosphonate single photon emission computed tomography (SPECT/CT) in patients with Modic changes (MCs) and degenerative disc disease. The aim of this study was to assess the value of the hybrid bone SPECT/CT imaging in patients with chronic LBP. We evaluate the correlation of hybrid bone SPECT/CT imaging patterns with MCs and disc abnormalities on magnetic resonance imaging (MRI). METHODS: This was a prospective study. Ninety-nine consecutive patients with LBP from a single center. The degree of lumbar intervertebral disc and endplate degeneration on MRI and osteoblastic activity was shown on SPECT/CT. These 99 consecutive patients with LBP were prospectively evaluated. Patients with contemporary lumbosacral spine MRI and bone SPECT/CT were included. Patients with known or suspected malignancy, trauma, infectious processes, and previous surgery were excluded. The effect of LBP on the daily quality of life was assessed using Oswestry disability index. We analyzed the correlation between the degenerative changes at the intervertebral disc spaces and endplates on MRI and bone SPECT/CT findings using receiver operating characteristic curve analysis and Kappa statistics. The Pfirrmann grading system was used to score the severity of disc space degeneration on MRI scans. RESULTS: A total of 99 patients were included in the study (58 women, 41 men; mean age, 56.2 years). Mean Oswestry disability index score was 38.5% (range, 8%-72%). The L2-3 through to L5-S1 levels were studied. MCs were found in 54% of patients. Of the 396 levels examined 85 were found to have MCs (21.5%). The most affected levels were L4-5 (31.3%) and L5-S1 (40.9%). Pfirrmann grade 5 disc space (72.9%) was associated with MC (Pp<0.001). MC (70.6%) and Pfirrmann grade 5 disc spaces (73%) resulted in scintigraphically active endplate/disc space on SPECT/CT (P<0.001). Bone SPECT/CT showed high metabolic activity in 96.1% of endplates with MC type I, 56% with MC type II, and 77.8% with MC type III. CONCLUSIONS: In this study we found a high agreement between MCs and increased metabolic activity on bone SPECT/CT imaging. MC type 1 and Pfirrmann grade 5 were the best binary predictors for positivity on bone SPECT/CT and had equivalent correlations. Lower vertebral levels in the lumbar spine were associated with higher degree of disc degeneration, high frequency of MCs, and positivity on bone SPECT/CT.