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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 4  |  Issue : 4  |  Page : 253-258

Evaluation of canal stenosis of herniated lumbar disc and its correlation to anterior-posterior diameter with magnetic resonance imaging morphometry


1 Department of Anatomy, IMS and SUM Hospital, SOA University, Bhubaneswar, Odisha, India
2 Department of Anatomy, Hi Tech Medical College, Bhubaneswar, Odisha, India
3 Department of Anatomy, SCB Medical College, Cuttack, Odisha, India
4 Department of Anatomy, VSS Medical College, Burla, Odisha, India
5 Department of Anatomy, MKCG Medical College, Berhampur, Odisha, India

Date of Web Publication20-Oct-2015

Correspondence Address:
Sitansu Kumar Panda
Department of Anatomy, IMS and SUM Hospital, SOA University, Bhubaneswar, Odisha
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2278-344X.167652

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  Abstract 

Background: The term disc prolapse is defined as extrusion of nucleus pulposus through a rent in annulus fibrosus. This prolapse disc causes impairment of function by nerve root compression compelling the patient to seek medical advice for low backache. A lumbar herniated disc is a common cause of low back pain radiating to the leg. The problem of prolapsed intervertebral disc is of great importance in this part of the world, because of the fact that people are subjected to various physical stress due to their living habits, low socioeconomic status. Ninety percent of lumbar disc extrusions occur at L4- L5or L5-S1. Central lesion may cause no symptoms with the exiting nerve roots unaffected whereas paracentral lesions cause symptoms due to compression of the exiting nerve root. Radio imaging technique has a pivotal role in the diagnosis of vertebral disc herniation. Various radiological procedures are used for the diagnosis, but MRI which is a relatively newer technique is treated as the gold standard in the field. Aim of the Study: In the present study, an attempt is made to establish the anatomy of herniated lumbar disc by the help of MRI technique in the patients of Eastern India & to correlate the occurance of disc herniation with age, sex & vertebral level. Methods and Material: The present study included 120 patients who have lumbar disc herniation syndrome & their MRI findingd are compared with MRI findings of 80 normal persons who are used as control. Results and Conclusions: The different parameters are compared & observed that the maximum number of disc prolapse occurs between 31- 40 age group. Taking the vertebral level into consideration, it is seen maximum number of herniation occurs at the level of L4- L5.

Keywords: Low backache, lumbar disc, magnetic resonance imaging, nucleus pulposus


How to cite this article:
Panda SK, Arora G, Mohanty BB, Sahoo SK, Mishra DN, Prusty JS. Evaluation of canal stenosis of herniated lumbar disc and its correlation to anterior-posterior diameter with magnetic resonance imaging morphometry. Int J Health Allied Sci 2015;4:253-8

How to cite this URL:
Panda SK, Arora G, Mohanty BB, Sahoo SK, Mishra DN, Prusty JS. Evaluation of canal stenosis of herniated lumbar disc and its correlation to anterior-posterior diameter with magnetic resonance imaging morphometry. Int J Health Allied Sci [serial online] 2015 [cited 2019 Oct 16];4:253-8. Available from: http://www.ijhas.in/text.asp?2015/4/4/253/167652


  Introduction Top


The spinal column is composed of 33 vertebrae arranged as 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral vertebrae and the coccyx. Except for C1, C2 and the sacrum, coccyx, each vertebra has similar osseous elements which include the vertebral body, pedicles, articular pillars, and laminae. Of these, the lumbar, sacral and the coccygeal segments constitute the lumbosacral spine. The intervertebral (I.V.) foramina are situated posteriorly between two adjacent vertebral pedicles. The dorsal and ventral roots mixed together to form nerve trunk which makes its exit through the I.V. foramen. It is at the level of the foramen by which nerve roots leave the vertebral canal that they are most commonly compressed. Commonest causes of such narrowing are fibrosis (hypertrophy) of the ligamentum flavum, bony proliferation from the margins of the foramen and posterolateral protrusion or rupture of an I.V. disc.[1] Ninety percent of lumbar disc extrusions occur at L4-L5 or L5-S1, while, of the remainder, most occur at L3-L4. The central lesion may cause no symptoms as the exiting nerve roots remain unaffected. Paracentral lesions cause symptoms as a result of compression of the exiting nerve root. For example, the S1 nerve root will be compressed by a paracentral L5-S1 disc extrusion. Various radiological procedures which are used for the diagnosis have their own advantage and disadvantage. But, magnetic resonance imaging (MRI) which is a relatively newer technique, is treated as the gold standard in this field. Parasagittal images are used to evaluate foraminal stenosis. In regard to the margins of the foramen, the disc and vertebral body lie anteriorly, the pedicles superiorly and inferiorly, and the facet joints posteriorly. On axial imaging, the margins of the spinal canal consist of the vertebral body anteriorly, the pedicles laterally and the lamina posteriorly. Anatomical study of herniated Lumbar disc in special reference to MRI is both on T1- and T2-weighted scans. In MRI scan, spinal alignment, disc height and hydration, vertebral body configuration, spinal canal size, spinal cord and nerve root compression are studied. Sciatica is a common ailment with a large economic impact both to the individual and to the industry. It has been estimated that sciatica strikes approximately 2–3% of the population and has a prevalence of 4.8% in men and 2.5% in women elder than 35 years of age. The average age of onset of the first sciatic attack is approximately 37 years with an antecedent initial attack of low back pain occurring in 76% of these patients approximately a decade earlier.[2] In this study, we have measured the anterior, posterior diameter of the spinal canal along with width and thickness of the disc and their relation to herniation and disc degeneration. Also, the hydration, disc degeneration and their relation to each other have been observed. All the data obtained in the study are analyzed statistically to establish a relation between them.


  Materials and Methods Top


The present study is a prospective case-control study which was designed to evaluate the MRI findings of lumbar disc prolapse on a series of 120 patients attending Neurosurgery Department of a tertiary level hospital of Eastern India. The patients of the study had lumbar disc herniation syndrome due to various causes and the study was done during the period from January 2011 to April 2013. MRI findings of the lumbar disc of 80 normal persons not who were investigated for other reasons were used as a control. A detailed history had been taken and clinical assessment was carried out for each patient which included name, age, sex, address, and occupation. Symptoms and history were enlisted in a chronological manner.

The clinical symptoms were taken in detail like if they had a low backache during coughing, sneezing, straining, if they had sciatica in relation to left or right or both sides, history of parasthesia, numbness, tingling sensation or grading weakness, bowel and bladder involvement. Along with that occupational history, past history of trauma, family history of prolapsed I.V. disc was also taken. Clinical finding such as spinal tenderness, the spinal deformity was searched for thoroughly.

Straight leg rising test (SLRT) was carried out in all cases. Movements of the spine in all directions were tested for observing restriction or abnormal movement. After examining each patient in the above manner, a provisional clinical diagnosis was made and the possible spinal segmental or vertebral level of compression was entered in the proforma. Then the patients were investigated to determine the anatomical site of compression and the possible pathological lesion causing it. A positive SLRT at 40° or less is suggestive of root compression. Contralateral positive SLRT is a very specific sign of root compression possibly by a disc prolapse. When SLRT is performed on the unaffected side, it may give rise to pain on the affected side. Criteria for lumbar stenosis on MRI were (1) a distortion or paucity of epidural fat either in the neural foramina, lateral recess or posteriorly between the ligamentum flavum (2) a diminution in the overall size of the neural foramina, neural canal and/or thecal sac. An attempt was made to determine the contribution of hypertrophied facet joints and bony over-growth as well as hypertrophy of the ligamentum flavum.[3] Data collected were grouped according to age, sex, spine level, and for sagittal anterior-posterior (SAG) and cross-sectional area of the spinal canal, the height of I.V. disc, type of disc prolapse, disc hydration, and vertebral body width.

*The SAG was measured between the superior border of the lamina and the posterior cortex of the vertebral body on the midline. A SAG value of 11 and 12 is regarded as relative stenosis and a value < 11 mm as absolute stenosis.[4]


  Result Top


The mean value of measurements has been taken into consideration in the following tables and it is compared with the control. The antero-posterior (AP) diameter of spinal canal at L3-L4 level in male control group are between 15.25 and 16.5 mm, whereas in case group, the same is between 12 and 12.6 mm [Table 1]. This data are depicted in [Figure 1]. The age group of 21–30 years shows the highest value. The AP diameter of the spinal canal at L3-L4 level in the female control group are between 14.5 and 16.22 mm in case group the same is between 12 and 14 mm [Table 2]. This data are depicted graphically in [Figure 2]. In 21–30 age group shows the highest value. The difference between the case and control group is statistically significant. The AP diameter of the spinal canal at L4-L5 level in male control group are between 14.66 and 16.5 mm and in case group, the same is between 10.92 and 12.29 mm [Table 3]. This is also shown in [Figure 3]. The age group of 21–30 shows the highest value. The difference between the case and control group is statistically insignificant. The AP diameter of the spinal canal at L4-L5 level in the female control group are between 15 and 15.77 mm in case group the same is between 10 and 13 mm [Table 4]. Graphical representation of same data is shown in [Figure 4]. 0–20 age group shows the highest value. The AP diameter of the spinal canal in males at L5-S1 level in normal cases are between 14.25 and 17 mm in case group the same is between 10.5 and 11.83 mm [Table 5]. This data are shown in [Figure 5]. In 51–70 age group shows the highest value. The difference between the case and control group is statistically significant. The AP diameter of the spinal canal at L5-S1 level in female normal cases are between 14 and 16.5 mm in case group the same is between 6 and 12.75 mm [Table 6]. This is depicted graphically in [Figure 6]. In 41–50 age group shows the highest value. The difference between the case and control group is statistically insignificant.
Table 1: AP diameter of spinal canal at L3-L4 level in males

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Figure 1: Graph showing antero-posterior diameter of spinal canal at L3-L4 level (males)

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Table 2: AP diameter of spinal canal at L3-L4 level in females

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Figure 2: Graph showing antero-posterior diameter of spinal canal at L3-L4 level (females)

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Table 3: AP diameter of spinal canal at L4-L5 level in males

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Figure 3: Graph showing antero-posterior diameter of spinal canal at L4-L5 level (males)

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Table 4: AP diameter of spinal canal at L4-L5 level in females

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Figure 4: Graph showing antero-posterior diameter of spinal canal at L4-L5 level (females)

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Table 5: AP diameter of spinal canal at L5-S1 level in males

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Figure 5: Graph showing antero-posterior diameter of spinal canal at L5-S1 level (males)

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Table 6: AP diameter of spinal canal at L5-S1 level in females

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Figure 6: Graph showing antero-posterior diameter of spinal canal at L5-S1 level (females)

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  Discussion Top


The vertebral canal begins at the lower part of the foramen magnum and ends at hiatus sacralis. It follows the vertebral curvature and forms a wavy canal. The diameter of the canal is not uniform. It's ovoid and smaller at the upper lumbar region, triangular at the lower lumbar region. The diminution of the dimension of spinal canal causes symptom complex.[1] There are 23 I.V. discs in the spinal column making up roughly a quarter of the height of the column. Shrinkage of the disc accounts for some of the loss in height in old age and also contributes to the variable degree of curves of the vertebral column. The thickness of I.V. disc is variable, being thicker in front than behind. Disc behaves like a cushion and shock absorber. They have a high water content which is maximum at birth and decreases with ageing.

This work is a prospective case-control study on the anatomy of herniated lumbar disc using MRI technique. Different aspects of the lumbar disc thickness, degeneration and its grade, hydration, and type of herniation were the prime target of their study.

Miller et al. studied the disc degeneration with the loss of height. Varol gave an elaborate study on lower lumbar vertebrae and the disc in between them in the patients with and without low back pain.[5] Prasad et al. worked on the anatomy and sociodemographic character of lumbar disc prolapse and analyzed properties such as AP diameter and cross-sectional area of spinal canal to established their relation with each other and to compare the values with that of previous workers.[6] Statistical analysis of the data obtained was done by deriving standard deviation and t-value. We preferred the students' t-test (unpaired) because:

  • This is a random sample having quantitative data
  • The sample number is <30 in each table.


By using unpaired t-test we derived the level of significance of a particular degree of freedom when the probability value is 5%.

Prasad et al. mentioned that disc prolapse occur at 34.4% in L4-L5 level and 26.7% in L5-S1 level. The AP diameter of a spinal canal of L1-L2 and L2-L3 has not been taken into account as the incidence of cases with disc prolapse in those levels are very less.[6] The AP diameter of the spinal canal at L3-L4 level in both male and female has been studied.

It is observed statistically that there is a significant difference between the values of case and control group in case of a male, but not in the female. As per Varol et al. the absolute stenosis of the spinal canal will be <11 mm and the relative stenosis values will be 11 and 12 mm.[4] Andersson et al. (1981) suggested that when the axial AP diameter of the spinal canal is <9.2 mm, it is called congenital lumbar stenosis.[7] Degenerative lumbar spinal stenosis manifests primarily after the sixth decade of life with L4-L5 and L5-S1 level predominance while congenital stenosis presents earlier age with similar findings but multilevel involvement and fewer degenerative changes.

Spinal stenosis

Spinal stenosis can be classified as:

  1. Central, when it affects the spinal canal
  2. Foraminal, when it affects the I.V. foramen and
  3. Lateral, when it affects the lateral recesses.


The size of the spinal canal is determined by different factors. The phenotypic expression of genetic factors can be altered by direct local injury (trauma, infection, etc.,) and the effects of systemic disturbances (malnutrition, cardiovascular illness, etc.,) during its development. From degenerative alterations, it is possible to differentiate whether they are congenital or developmental in origin. The most significant and frequent causes of lumbar spinal stenosis are the degenerative diseases of the discs and articular processes (facets), and hypertrophy of the ligamentum flavum. Degenerative lumbar spinal stenosis manifests primarily after the sixth decade of life as a result of facet hypertrophy and degenerative disc disease. Congenital stenosis, on the other hand, presents earlier in age with similar clinical findings, but with multilevel involvement and fewer degenerative changes. To establish the diagnosis of spinal stenosis, the best method is computed tomography (CT) with myelography, but plain CT or MRI can also be used with good results. Criteria described in the literature for the diagnosis of central lumbar spinal stenosis are:

  1. Symptoms and signs
  2. Reduction in the AP diameter (sagittal diameter of the vertebral foramen; SAG) of the spinal canal at the level of stenosis and the corresponding reduction in the spinal canal area as estimated by CT, without taking into account the patient's height and weight.


The SAG is measured between the superior border of the lamina and the posterior cortex of the vertebral body on the midline. A SAG value between 11 and 12 mm is regarded as relative stenosis and a value < 11 mm as absolute stenosis.[4] Stenosis is noted mainly in vertebrae L4, L5 and S1. Absolute and relative stenosis in SAG was less in females, suggesting that sex might be an important factor. Significant sex differences are especially marked in vertebrae L4 and L5. Therefore, it is suggested that developmental, physical and sex differences all play roles in the development of the vertebral canal.

Lumbar intervertebral discs

The lumbar I.V. discs can be classified morphologically as immature (new born), transitional (adolescent), adult (30 onwards), early degenerated (60 onwards), or severely degenerated (80 or older). The normal adult lumbar I.V. disc measure 8–15 mm in height and 30–50 mm in diameter. The ratio of the vertical diameter of each disc space to the vertical diameter of the adjacent vertebra is normally in the range of 0.3–0.6 in adults. In axial anatomic sections the L1-L4 discs have a slightly concave or flat posterior border; the L5 disc has a flat or slightly convex posterior border.[8]

Disc herniation

The definition of disc herniation is the protrusion of degenerated or fragmented disc material into the foramen thus compressing a nerve root or into the spinal canal compressing the spinal cord or cauda equina. Disc herniation is classified into four categories-disc bulges, protrusion of the disc, extrusion, and free fragment.[5]


  Conclusion Top


In this prospective study which covered 200 patients of Eastern India out of which 120 suffered from lumbar herniation syndrome and 80 are normal persons (taken as controls), it is observed that the maximum number of disc prolapse occurs between 31 and 40 age group. Taking the vertebral level into consideration, it is seen maximum number of herniation occurs at the level of L4-L5. In the occurrence of disc disease, it is seen that males are more sufferer than the females. So far the area and anterior-posterior the diameter of the spinal canal is concerned our findings on average is little more (0.5 mm) than that of the earlier workers. This may be due to a small number of samples or racial variation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Henry Gray. Gray's Textbook of Anatomy. 39th ed. Elsevier: Churchil livingstone; 2004. p. 736.  Back to cited text no. 1
    
2.
Bell GR, Rothman RH, Booth RE, Cuckler JM, Garfin S, Herkowitz H, et al. A study of computer-assisted tomography. II. Comparison of metrizamide myelography and computed tomography in the diagnosis of herniated lumbar disc and spinal stenosis. Spine (Phila Pa 1976) 1984;9:552-6.  Back to cited text no. 2
    
3.
Modic MT, Steinberg PM, Ross JS, Masaryk TJ, Carter JR. Degenerative disk disease: Assessment of changes in vertebral body marrow with MR imaging. Radiology 1988;166:193-9.  Back to cited text no. 3
    
4.
Varol T, Iyem C, Cezayirli E, Erturk M, Kayalioglu G, Hayretdag C. Comparative morphometry of the lower lumbar vertebrae: Osteometry in dry bones and computed tomography images of patients with and without low back pain. J Int Med Res 2006;34:316-30.  Back to cited text no. 4
    
5.
Miller JA, Schmatz C, Schultz AB. Lumbar disc degeneration: Correlation with age, sex, and spine level in 600 autopsy specimens. Spine (Phila Pa 1976) 1988;13:173-8.  Back to cited text no. 5
    
6.
Prasad R, Hoda M, Dhakal M, Singh K, Srivastava A, Sharma V. Epidemiological characteristics of lumbar disc prolapse in a tertiary care hospital. Internet J Neurosurg 2005;3:1.  Back to cited text no. 6
    
7.
Andersson GB, Schultz A, Nathan A, Irstam L. Roentgenographic measurement of lumbar intervertebral disc height. Spine (Phila Pa 1976) 1981;6:154-8.  Back to cited text no. 7
    
8.
Haughton VM, Eldevik OP, Magnaes B, Amundsen P. A prospective comparison of computed tomography and myelography in the diagnosis of herniated lumbar disks. Radiology 1982;142:103-10.  Back to cited text no. 8
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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