|Year : 2014 | Volume
| Issue : 1 | Page : 3-7
Magnetic resonance imaging in the diagnosis of lumbar canal stenosis in Indian patients
Inder Pawar1, Supreethi Kohli2, Vipin Dalal2, Vinod Kumar2, Seema Narang2, Anu Singhal2
1 Departments of Orthopedics, ESI Model Hospital and Post Graduate Institute of Medical Sciences and Research, Basaidarapur, New Delhi, India
2 Department of Radiology, ESI Model Hospital and Post Graduate Institute of Medical Sciences and Research, Basaidarapur, New Delhi, India
|Date of Web Publication||10-Jun-2014|
Tower 5, flat no 1403, Sushant Estate, Sector 52, Gurgaon, Haryana 122 002
Source of Support: None, Conflict of Interest: None
Introduction: Magnetic resonance imaging (MRI) has become the choice of imaging modality for lumbar canal stenosis (LCS) due to limitations and radiation risks of computed tomography (CT) and spinal radiography. The radiological criteria for diagnosis of LCS are still ambiguous. Aim of this study is to find out the radiological dimensions on MRI of lumbar spinal canal in Indian patients and the critical dimensions at which the symptoms occur. Materials and Methods: A cross-sectional study was conducted in ESI Hospital, New Delhi from July 2011 to 2013. Two study groups were studied, the symptomatic LCS group, consisted of 30 individuals of either sex in age group of 45-65 years. The control group consisted of 30 asymptomatic age matched individuals. MRI scans were performed on 1.5 Tesla scanner. Dimensions of lumbar canal at all the levels (L1-L5) of lumbar vertebra of 60 patients were measured. Results: In our study, in symptomatic group, narrowest mid-sagittal diameter antero-posterior (mean 10.61) was at L5-S1 level. The interligamentous diameter (ILD) showed no significant difference between the two groups. Lateral recess depths showed a significant difference between the two groups at all levels except L1 on right side and L1 and L2 on left side. Critical canal dimension was found to be 11.13 mm. Conclusion: MRI can effectively evaluate the lumbar canal stenosis. The critical canal dimensions at which symptoms of stenosis appear were 11.13.
Keywords: Lumbar canal, magnetic resonance imaging, stenosis
|How to cite this article:|
Pawar I, Kohli S, Dalal V, Kumar V, Narang S, Singhal A. Magnetic resonance imaging in the diagnosis of lumbar canal stenosis in Indian patients. J Orthop Allied Sci 2014;2:3-7
|How to cite this URL:|
Pawar I, Kohli S, Dalal V, Kumar V, Narang S, Singhal A. Magnetic resonance imaging in the diagnosis of lumbar canal stenosis in Indian patients. J Orthop Allied Sci [serial online] 2014 [cited 2019 Mar 22];2:3-7. Available from: http://www.joas.in/text.asp?2014/2/1/3/134200
| Introduction|| |
Lumbar spinal stenosis (LSS) is a source of neurogenic claudication causing bilateral or unilateral lower limb pain, numbness, paresthesia or weakness. ,,, Accurate diagnosis of the clinical syndrome of spinal stenosis is important because of the substantial differential diagnoses and because the range of treatments includes spinal surgery, which is associated with some morbidity and treatment failure in the elderly population. ,,, There has not been convincing evidence of a relationship between symptoms or surgical results and any anatomical measurement. ,,,,, The LSS has been defined as any type of narrowing of the spinal canal.  It may be developmental (congenital) or acquired.  Developmental stenosis is rare, characterized by short pedicles and narrowing of the spinal canal dimensions, , whereas acquired degenerative stenosis is most common.  Anatomically, LSS could be involved in the central canal, lateral recess, foramina or any combination of these locations. Central spinal stenosis (CSS) is most common at the L2-L3, L3-L4, L4-L5 and patients present with symptoms of radiculopathy or myelopathy often acquired with bilateral extremity claudication on exertion. The most common canal stenotic conditions are acquired along with developmental conditions; such as, narrowed or abnormally shaped spinal canal. The most common shape of canal is round and ovoid; perhaps 15% of humans have a trefoil canal. Lateral recess stenosis is present when the distance between the superior facets antero-medially and the posterior vertebral body margin is less than 4 mm. Hypertrophic inferior facets narrow the lateral recess by reducing the interlaminar angle.  Diagnosis and imaging is based on clinical findings. Neurologic findings on physical examination are unusual. Some patients can have a narrowed canal without symptoms and do not require therapy. Several studies have attempted morphometrically to characterize the lumbar spine in individuals with degenerative lumbar spinal stenosis (DLSS) with diverse results. ,,,,,,,,, Some radiological studies have reported that the changes in the anterior-posterior (AP) diameter, transverse diameter and cross-section area (CSA) of the spinal canal and dural sac are risk factors for developing spinal stenosis. ,,, The poor correlation between radiological manifestations and the clinical picture, ,,, emphasizes the fact that more studies are required to determine the natural course of this syndrome. MRI is extensively used for imaging of lumbar spine, as it is noninvasive and also gives complete overview of osseous canal along with its soft tissue components. The transverse and sagittal dimensions of the central canal are best depicted by the orthogonal planes on T2W sequences, providing the best views of thecal sac dimensions. Peripheral stenosis is best appreciated on T1W images, the parasagittal and axial images allow identification of lateral recess and the neural foramina. Upright MRI, a recent advancement, loads the spine, allows for flexion, extension and makes stenosis more obvious. Studying the morphometric characteristics of the lumbar vertebrae in the DLSS population may assist in developing useful conservative treatments and improvement of surgical procedures. In addition, detecting specific features in an asymptomatic population can be important in preventing or delaying the onset of symptoms in this group.
The aim of this study to assess the radiological dimensions of lumbar spine canal in symptomatic patients of lumbar canal stenosis with reference to age matched asymptomatic population and to find out critical canal dimension in AP dimension at which the symptoms appear.
| Materials and Methods|| |
A cross-sectional study conducted by the Department of Orthopedics and Radiology, ESI Hospital, New Delhi from July 2011 to 2013. All patients were assessed by a structured performa for epidemiological and clinical details. Investigations to be performed were explained to each patient and written consent was taken. The study was approved by Ethical Committee of the Institute.
A total of two study groups were studied. The symptomatic LCS group consisted of 30 individuals of either sex in age group of 45-65 years with signs and symptoms related to LCS. All individuals in this group were interviewed and examined using a defined protocol. They exhibited intermittent neurogenic claudication and were often accompanied by other symptoms, such as radiculopathy or low backache. The control group consisted of 30 asymptomatic age-matched individuals. They were interviewed to exclude possible LCS-related symptoms.
(1) Lumbar vertebrae fracture (2) vertebral abnormalities (3) previous spinal surgery (4) Spinal tumors (5) Pott's spine (6) Paget's disease (7) gross spinal pathology (e.g., spondylolisthesis, retrolisthesis and disc-space collapse).
All study subjects underwent magnetic resonance imaging (MRI) of the lumbar spine. MRI radiologist was blind to the subject status. The MRI scan was performed on Philips Acheiva (Philips Health Care, Netherlands, BV) 1.5 Tesla scanner, coil used was sense spine, 4 mm slice thickness, sequence included (1) T2W FSE SAG, (2) T1W FSE SAG, (3) STIR COR, 4T1W FSE AXIAL (5) T2W FSE AXIAL (6) T2 FSE DRIVE AXIAL (high resolution) sequence using DRIVE with a small FOV to reduce cerebrospinal fluid (CSF) flow artefacts. Dimensions of lumbar canal at all the levels (L1-L5) of lumbar vertebra of 60 patients were measured. MRI measurements were taken at all levels from L1 to L5: (1) Antero-posterior diameter was measured on T2W at mid-sagittal level as the distance between the posterior border of the vertebra and the lamina posteriorly at the midline [Figure 1]. (2) Interpedicular distance was measured on T2W axial at the mid pedicular level as the distance between the inner borders of both the pedicles of vertebral bodies [Figure 2]. (3) Inter-ligamentous diameter (ILD) was measured on T2 W axial as the distance between the inner borders of ligamentum flavum at the point joining the facets in MRI. (4) Lateral recess depth (LRD) was measured from the dorsal surface of vertebral body to the most ventral segment of the superior articular facet.
|Figure 1: Sagittal T2w image with spinal canal diameter at various levels|
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It was performed using mean, standard deviation (SD), standard error and Student's t-test. A P value less than 0.05 were considered statistically significant.
| Results|| |
Out of 2 study groups, the symptomatic LCS group consisted of 16 males and 14 females with mean age 52.65 years (range 45-65) [Table 1] and Figure 3]and the other normal (asymptomatic) group consisted of 17 males and 13 females with mean age 54.50 years (range 46-64) [Table 1] and [Figure 3]. Overall, there were 33 males (55%) and 27 females (45%) in our study [Table 2].
|Figure 3: Bar diagram shows age distribution of normal and symptomatic lumbar canal stenosis group|
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|Table 1: Chart shows age distribution of Normal and symptomatic groups (in years)|
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|Table 2: Charts shows sex distribution of the symptomatic and normal group Sex distribution|
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Mid-sagittal diameter on MRI
In normal group, the mean of mid-sagittal (antero-posterior) diameter in millimeter from L1 to L5 showed a steady increase in diameter [Table 3]. Whereas in symptomatic LCS group, there was a steady increase from L1 to L3 and then diameter decreased from L3 to L5 as shown in figure below. There was a significant difference (P < 0.05) in midsagittal diameter between the 2 groups at L4 and L5 levels.
|Table 3: Chart shows mean spinal canal diameter values on sagittal images in normal and symptomatic group|
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The mean mid-sagittal (antero-posterior) diameter of lumbar central canal in the normal group showed gradual increase in diameter from L1 to L5 [Table 3], whereas in symptomatic LCS group there was decrease in values [Table 3]. More number of patients in symptomatic group had AP diameter less than 11.13 mm as compared to asymptomatic patients [Table 4].
|Table 4: Chart shows number of patients in normal and symptomatic group with reference to spinal canal diameter value 11.13 mm on sagittal images|
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The diagnostic accuracy as given by the area under ROC curve is 0.815 (95% CI 0.681-0.949). Taking 11.13 mm spinal canal diameter as cut-off for symptoms on sagittal images has high specificity (93.33%), however it has less sensitivity (60%) [Table 5].
|Table 5: Chart shows various statistical values of AP spinal canal diameter value 11.13 as cut-offf or symptoms|
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The mean diameter in both groups showed no significant difference. The range at all the levels was 17 to 36 mm in the normal group and 15.30 to 36 mm in symptomatic LCS group [Table 6]. The measurement of the lumbar vertebrae showed a steady increase in the interpedicular distance from L1 to L5 in both the groups.
|Table 6: Chart shows inter-pedicular diameter (in mm) in normal and symptomatic groups|
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Inter-ligamentous diameter on MRI
There was no significant difference between the mean diameters between the two groups [Table 7]. In normal group, there was an increasing pattern in the mean diameters from L1 to L5.
|Table 7: Chart shows inter-ligamentous diameter (in mm) in normal and symptomatic groups|
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Lateral recess depth of right side on MRI
There was a significant difference between the mean measurements of left side lateral recess depth between the 2 groups at all levels except L1 [Table 8].
|Table 8: Chart shows lateral recess depth (in mm) on right side in normal and symptomatic group|
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Lateral recess depth of left side on MRI
There was a significant difference between the mean measurements of left side lateral recess depth between the 2 groups at all levels except L1 [Table 9].
|Table 9: Chart shows lateral recess depth (in mm) on left side in normal and symptomatic group|
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| Discussion|| |
North American Spine Society states in their guideline that imaging is the key non-invasive test for LSS but they provide no radiological criteria for stenosis in these guidelines. MRI has become investigation of choice as it is non-invasive, with no radiation risks and gives overview of spine along with its soft-tissue components. Our cross-sectional study, which included 30 study subjects in symptomatic LCS group and 30 normal groups shows that MRI can effectively be used for analysis of LSS.
In our study, the narrowest and widest mid-sagittal diameters on MRI were at L5-S1 (mean 10.61) in symptomatic LCS group and L1-L2 in normal group. Our results were consistent with the study done by Deep S. Chatha and Mark E. Schweitzer (2011) also the narrowest level was at L5-S1 (mean 11.6 mm) and widest at L1-L2 (mean15.6 mm).  The mean Inter-pedicular diameter (IPD) between the two groups showed no significant difference. The range at all the levels was 17 to 36 mm in the normal group and 15.30 to 36 mm in symptomatic group. The measurement of lumbar vertebrae showed a steady increase in the IPD from L1 to L5 in both the groups, which is consistent with other studies like Eisenstien  , Karantanas et al.,  Rapala et al., ILD showed a steady increase L1 to L5 and there was no significant difference between the two groups. The minimum value (mm) from L3 to L5 in our study were 10-17, 13.6-19.6 and 14.2-25.1, whereas in a study of Karantanas (1998), ranges were 7.3-23.6, 8.4-26.58 and 11.4-28.8 mm.  In our study, there was significant difference between the mean measurements of the right lateral recess depth between the two groups except L1. There was a significant difference between the mean measurements of the left lateral recess depth between the two groups from L2 to L5. The findings of this study were compatible with other studies of Bolender et al.,  1985, Beers et al.,  1985, Schonstrom et al.,  1985, where lateral recess was studied though not in central spinal canal stenosis entity.
For measurement of critical canal dimensions ROC curve analysis of MRI-AP was used. It found a cutoff value that minimizes the number of false positives and false negatives. Minimizing the false positives and false negatives is the same as maximizing the sensitivity and specificity. Thus a good first choice for a test cutoff value is that value, which corresponds to a point on the ROC curve nearest to the upper left corner of the ROC graph, which is 11.13 mm Fukusaki et al.,  (1998) reported it to be <15 mm, whereas Koc et al.,  (2009) reported it to be <12 mm but these two studies did not report the measurement points.
| Conclusion|| |
According to our cross-sectional study, MRI was able to differentiate between symptomatic and asymptomatic groups with good reliability of the measurements. There were significant differences in AP dimensions of lumber spinal canal in symptomatic patients, which is a measure of central canal stenosis. The critical AP canal dimension for symptoms to appear in our study on basis of ROC curve analysis is 11.13. It was also found that there were significant differences in the lateral recess depth on both right and left side indicating that MRI is also beneficial to assess LCS. Limitations and radiation risk of CT scan and spinal radiography suggest that MRI represents the best imaging modality for assessment of lumbar canal stenosis. A limitation to this study is small sample size.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]