Original ArticleHybrid Bone Single Photon Emission Computed Tomography Imaging in Evaluation of Chronic Low Back Pain: Correlation with Modic Changes and Degenerative Disc Disease
Introduction
Low back pain (LBP) is an extremely common disorder, with a prevalence ranging from 60%–90% and a peak prevalence in the fifth decade.1, 2 Among older adults, LBP is the most frequently reported musculoskeletal problem and the third most frequently reported symptom of any kind.1, 2
Although several anatomic structures have been found to be potential sources of LBP, it is difficult to identify a specific pathoanatomic cause in most cases, particularly in patients with chronic LBP, in whom psychologic factors are thought to play a critical role in pain pathogenesis.1 Also, several degenerative changes and structural abnormalities have been shown to exist even in asymptomatic individuals.3
Degenerative spinal disease includes degenerative disc disease (DDD) and degenerative facet disease or facet osteoarthritis.4, 5 Both these conditions are common in the general population, particularly among older adults.6 Either DDD or facet arthropathy have been suggested as sources of LBP, but there is still conflicting evidence regarding their role as primary cause of pain.7, 8, 9, 10, 11
Multiple radiologic modalities are used in evaluation of patients with LBP. Plain radiography is universally available and inexpensive, but its value in the evaluation of LBP is questionable. Computed tomography (CT) is extremely useful to study the bone and joint anatomy. Its use currently is mostly restricted to trauma and postoperative settings. Magnetic resonance imaging (MRI) provides excellent soft tissue resolution and has become a routine investigation in evaluation of patients with LBP due to its ability to clearly define DDD. However, these diagnostic modalities evaluate morphologic parameters, they are limited in the ability to differentiate between incidental and clinically relevant changes. Recent introduction of bone hydroxydiphosphonate (HDP) single photon emission computed tomography (SPECT/CT) allows assessment of morphology and bone physiology in a single study. Bone single photon emission (SPECT) is an extension of the conventional 1-dimensional bone scan, applying a tomographic method to acquire data map tracer distribution in 3-dimensional mode. The SPECT data are fused to a conventional CT acquired in the same sitting, on the same camera, using a hybrid imaging system. Data from the 2 modalities are complementary and allow the foci of abnormal bone metabolism to be localized with anatomic precision, hitherto lacking in conventional bone scans, whereas the CT scan further embellishes the diagnostic information. Bone HDP SPECT/CT could potentially be used in a complimentary fashion to MRI to refine the significance of incidental from clinically relevant findings.
The purpose of this study was to define and correlate the patterns of scintigraphic abnormalities on bone SPECT/CT imaging with MRI findings in patients with LBP. We correlated bone SPECT/CT imaging patterns with DDD features on MRI.
Section snippets
Methods
Ninety-nine consecutive patients with LBP were prospectively evaluated. Patients with contemporary lumbosacral spine MRI and SPECT/CT were included. Patients with known or suspected malignancy, trauma, infectious processes, and previous surgery were excluded. Patients with signs of dynamic instability on flexion-extension roentgenogram were also excluded. The effect of LBP on the daily quality of life was assessed using Oswestry disability index (ODI). The L2-3 to L5-S1 levels were included in
Results
Ninety-nine patients were included in the study (58 women and 41 men; mean age, 56.2 years). The L2-3 to L5-S1 levels were studied. Mean ODI score was 38.5% (range, 8%–72%). There was no statistically significant difference in ODI in patients with and without positive bone SPECT/CT. A total of 396 levels were analyzed. Description of the study sample by test results are shown in Table 1.
Discussion
LBP is an extremely common disorder, with a prevalence ranging from 60%–90% and a peak prevalence in the fifth decade.1, 2 Radiologic investigations, like skeletal radiography, CT, and MRI, are used in the evaluation of patients with LBP. Radiography is universally available and an inexpensive investigation for an initial evaluation. However, its value in LBP has been questioned. Lumbar spine radiographs with flexion-extension views are useful to evaluate the presence of vertebral instability,
Conclusions
In the present study we analyzed the correlation between degenerative changes at endplates/disc level on MRI and bone SPECT/CT findings in patient with LBP. We found an agreement between MCs and high osteoblastic activity/bone metabolic turnover on bone SPECT/CT imaging. MC type I 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 more disc degeneration, high
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.