Imaging correlation of the degree of degenerative L4-5 spondylolisthesis with the corresponding amount of facet fluid. J Neurosurg Spine

National Health Insurance Medical Center, Goyang, South Korea.
Journal of neurosurgery. Spine (Impact Factor: 2.38). 11/2009; 11(5):614-9. DOI: 10.3171/2009.6.SPINE08413
Source: PubMed


The aim of this study was to correlate the degree of L4-5 spondylolisthesis on plain flexion-extension radiographs with the corresponding amount of L4-5 facet fluid visible on MR images.
Patients underwent evaluation at the Neurosurgical Spine Clinics of Stanford University Medical Center and National Health Insurance Medical Center (Goyang, South Korea) between January 2006 and December 2007. Only patients who were diagnosed with L4-5 degenerative spondylolisthesis (DS) and who had both lumbosacral flexion-extension radiographs and MR images available for review were eligible for this study. Each patient's dynamic motion index (DMI) was measured using the lateral lumbosacral plain radiograph and was the percentage of the degree of anterior slippage seen on flexion versus that seen on extension. Axial T2-weighted MR images of the L4-5 facet joints obtained in each patient was analyzed for the amount of facet fluid, using the image showing the widest portion of the facets. The facet fluid index was calculated from the ratio of the sum of the amounts of facet fluid found in the right plus left facets over the sum of the average widths of the right plus left facet joints.
Fifty-four patients with L4-5 DS were included in this study. Of these 54 patients, facet fluid was noted on MR images in 29 patients (53.7%), and their mean DMI was 6.349 +/- 2.726. Patients who did not have facet fluid on MR imaging had a mean DMI of 1.542 +/- 0.820; this difference was statistically significant (p < 0.001). There was a positive linear association between the facet fluid index and the DMI in the group of patients who exhibited facet fluid on MR images (Pearson correlation coefficient 0.560, p < 0.01). In the subgroup of 29 patients with L4-5 DS who showed facet fluid on MR images, flexion-extension plain radiographs in 10 (34.5%) showed marked anterolisthesis, while the corresponding MR images did not.
There is a linear correlation between the degree of segmental motion seen on flexion-extension plain radiography in patients with DS at L4-5 and the amount of L4-5 facet fluid on MR images. If L4-5 facet fluid in patients with DS is seen on MR images, a corresponding anterolisthesis on weight-bearing flexion-extension lateral radiographs should be anticipated. Obtaining plain radiographs will aid in the diagnosis of anterolisthesis caused by an L4-5 hypermobile segment, which may not always be evident on MR images obtained in supine patients.

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    • "Increased fluid in the lumbar facet joints is the result of degeneration of the synovial joints, and this fluid is detectable using MRI [10, 11]. Some authors have recently reported the existence of a correlation between facet joint effusion detected on the supine MRI and radiographic signs of lumbar instability [12–15]. "
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    ABSTRACT: Magnetic resonance imaging (MRI) is often used to evaluate low back pain; however, MRI in the supine position does not always reveal degenerative spondylolisthesis. The existence of a linear correlation between increased fluid in the facet joints seen on the supine axial T2 MRI of the lumbosacral spine and lumbar instability seen on standing lateral flexion-extension lumbosacral radiographs has recently been reported. The objective of this prospective study was to determine the incidence of increased fluid in the lumbar facet joints seen on the supine axial T2 MRI, and to evaluate the correlation of this finding with radiographic evidence of lumbar instability. We prospectively analyzed weight-bearing flexion-extension lumbosacral radiographs and lumbosacral MRI in the supine position for 52 patients (mean age 64.7 years) seen at our institution for low back pain and/or radiculopathy. The statistical analysis was performed with Fisher's exact test. A difference was considered statistically significant if P < 0.05. In all but 5 of the 52 patients, degenerative disc disease and facet joint disease were observed on the supine MRI of the lumbosacral spine. Fifteen patients had exaggerated fluid in the lumbar facets on the axial T2 MRI (28.8%). Radiographic signs of degenerative lumbar spondylolisthesis were observed in 12 patients (23.1%), and the degenerative spondylolisthesis was not evident on the supine sagittal MRI in 10 of these 12 patients (83.3%). Among these 12 patients, the axial T2 MRI showed exaggerated fluid in the facet joints at the corresponding level in 8 patients (66%). Increased fluid in the lumbar facet joints was present on the supine axial T2 MRI in 7 patients (13.4%), even though there were no radiographic signs of corresponding lumbar instability. We observed a statistical correlation between increased fluid in the lumbar facet joints on the supine axial T2 MRI and degenerative spondylolisthesis seen on standing lateral flexion-extension lumbosacral radiographs.
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    ABSTRACT: Background and purpose: Lumbar disc herniation (LDH) at the level of non-displaced spondylolysis (isthmic spondylolisthesis) is an uncommon association rarely evaluated in the literature. In this study, authors examine whether the continuous posterior epidural fat between the dura mater and spinous process (continuous double-hump sign) at the level of LDH is a valuable tool to identify patients with non-displaced spondylolysis on MRI. Methods: Eighteen patients (group 1) presented at our department (2000-2010) with a LDH associated with an undiagnosed non-displaced spondylolysis on MRI. Spondylolysis was confirmed by direct visualization of the defect on CT-scan, dynamic radiography, MRI or at surgery. To validate this method, we made the same evaluation in 20 surgically treated patients (group 2) with a one-level LDH without spondylolysis. Results: In all patients of group 1 spondylolysis was unsuspected on the MRI report. However, a positive "continuous double-hump sign" was seen in 16 patients. The spondylolysis was recognized on MRI in six cases, on CT-scan in nine cases and on dynamic radiography in one case. Two cases were diagnosed surgically. In group 2, only one patient had a positive "continuous double-hump sign". This new sign had a specificity of 95%, sensitivity of 88.88%, and accuracy of 92.10% for diagnosis of non-displaced spondylolysis. Conclusions: Non-displaced spondylolysis may be associated with adjacent LDH. Although uncommon, it is important for neurosurgeons to be aware of this association because of its implication on the therapeutical management. MRI is not always sufficient to recognize a non-displaced spondylolysis with certainty; however "continuous double-hump sign" may be used as a simple valuable diagnosis tool.
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