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ISSN: Print -2349-0977, Online - 2349-4387

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Year : 2018  |  Volume : 4  |  Issue : 4  |  Page : 227-232

Morphometric changes in lumbar vertebral bodies and intervertebral discs in tandem with diminution in bone mineral density

Department of Radiodiagnosis, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India

Date of Web Publication29-Oct-2018

Correspondence Address:
Ranjan Chandra
Department of Radiodiagnosis, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi - 110 029
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/astrocyte.astrocyte_25_18

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Background: Morphometry of vertebral body (VB) and intervertebral disc space (IVD) is a reflection of the osseous strength, which primarily depends on the bone mineral density (BMD) and a host of other factors. As an individual ages, the internal hormonal milieu and the BMD undergoes a change. This is a ubiquitous phenomenon that impacts the quality of life and increases morbidity and mortality. The pathophysiologic process that causes changes in the BMD tends to alter the morphology of VB and the adjacent IVD as well. Aim: To correlate the morphological changes in the lumbar VBs and IVDs using MRI with changes in BMD in the Indian population. Materials and Methods: A total of 100 ambulatory adults in the age group 40–70 years were included in the study. The lumbar BMD was measured using a dual-energy X-ray absorptiometry (DEXA). Morphometry of the VBs and IVDs was performed using 1.5-T MRI, T2-weighted sagittal images and their heights (at various levels) and volumes were measured. Continuous variables were examined by analysis of covariance after correction for height and age. Results: There was no age difference among the subjects of normal BMD, osteopenia, and osteoporosis. Lower BMD was associated with a decrease in anterior, middle, and posterior heights (Ha, Hm, and Hp, respectively) and antero-posterior dimension (AP) of the vertebral body, leading to an increased biconcavity index. With regard to IVD, decrease in BMD was associated with a decline in Ha and Hp and AP dimension and increase in middle height, leading to an increased biconvexity index in both genders. Lower BMD was further associated with an overall decrease in both VB and IVD volume. Conclusion: The change in BMD in subjects with osteopenia and osteoporosis affects the morphology of spinal vertebra and adjacent IVDs and is associated with a decrease in VB and IVD volumes. MRI morphometry correlates well with the BMD measurements.

Keywords: Bone mineral density, intervertebral disc, lumbar spine, osteopenia, osteoporosis, vertebra

How to cite this article:
Bagri N, Madage T, Chandra R, Chopra R, Agarwal Y, Gupta N. Morphometric changes in lumbar vertebral bodies and intervertebral discs in tandem with diminution in bone mineral density. Astrocyte 2018;4:227-32

How to cite this URL:
Bagri N, Madage T, Chandra R, Chopra R, Agarwal Y, Gupta N. Morphometric changes in lumbar vertebral bodies and intervertebral discs in tandem with diminution in bone mineral density. Astrocyte [serial online] 2018 [cited 2019 Dec 8];4:227-32. Available from: http://www.astrocyte.in/text.asp?2018/4/4/227/244293

  Introduction Top

The word “osteoporosis” has been derived from the Greek words “osteon” meaning bone and “poros,” meaning a pore or passage. Osteoporosis is characterized by low bone mass and micro-architectural deterioration of osteoid tissues making the bones fragile and susceptible to fractures.[1] Although the entire skeleton is affected with the decline in bone mineral density (BMD), the spine, being the primary load-bearing region, is severely affected with reduction in the number of horizontal trabecular cross braces within the cancellous bone of the vertebral bodies.[2] This compromise in osseous strength is a strong indicator for considerable morbidity and mortality.

The diminution in BMD is associated with a wide range of morphometric changes in VB and IVD.

The extent of changes may vary with age, gender, and ethnicity and cuts across the geographic and demographic divide.[2],[3] The Caucasians and Asians are at a comparatively higher risk of developing osteoporosis. Few studies indicate that decline in BMD may occur at a relatively younger age in the Indian population.[4],[5]

The vertebrae undergo continuous remodeling throughout life, primarily in response to the changing needs of the body.[6],[7] With increasing stress on the center of the vertebral endplates, vertebral deformities and micro-fractures occur, leading to a progressive reduction in the height of vertebral bodies (VB).[8] This bio-mechanical stress trigeered by decline in bone mass also affects the morphology of IVD leading to decrease in total spinal length which may be a possible key factor for decrease in body height with age.

Although several studies have documented the effects of decline in BMD on the morphometry of VBs, there is still a paucity of literature illustrating the morphological changes in IVDs.[9] The results of previous reports on the relationship between VB and disc heights with aging or osteoporosis are quite diverse and inconsistent.[10],[11] Most of the studies conducted earlier used conventional radiographic techniques that are limited by two-dimensional projection and hence being vulnerable to distortion and magnification errors.[12]

Magnetic resonance imaging (MRI) of the spine is a robust technique for obtaining three-dimensional quantitative data for simultaneously assessing the morphologies of both VB and IVD. To date, only a few studies have juxtaposed the morphological changes in IVD with decrease in BMD.

  Materials and Methods Top

This study was carried out on 100 adult subjects (age: 40–70 years; 43 men and 57 women) including all patients who presented with low backache and were referred for dual-energy X-ray absorptiometry (DEXA) to our department. Those who were unable to walk had clinical or radiological evidence of metastases, spondylolisthesis, spondylolysis, severe kyphotic deformity, prior major spinal or hip surgery, past history of spine fracture, hormonal therapy, and suffering from medical conditions unsuitable for MRI, for example, an incompatible metallic implant, cardiac pacemaker, or claustrophobia.

The BMD of VBs was measured as T score of the L1-L5 vertebrae and consequently, the subjects were categorized into three groups (normal, osteopenia, and osteoporosis) using the World Health Organization criteria (normal T score >-1.0; osteopenia T score between -1.0 and -2.5; and osteoporosis Tscore ≤2.5 irrespective of gender) [Figure 1]. The normality curve for Indian Population is integrated in the software of the machine.
Figure 1: DEXA Scan of a Male Subject Showing BMD Measurements- 0.703g/cm2 and T-score -2.8, Indicative of Osteoporosis.

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MRI was performed using a 1.5-Tesla (PhilipsAchieva) MR scanner. A series of sagittal T2-weighted images (TR = 3500 ms, TE = 120 ms) were obtained at matrix = 512 × 281, field of view = 320 × 320 mm, slice thickness = 5 mm, inter-slice gap = 0.5 mm, and number of signal acquisition = 2. The MR images of all the subjects were measured at the level of central slice of each VB and IVD. The key measurements obtained were anterior height (Ha), middle height (Hm), posterior height (Hp), antero-posterior (AP) dimension, and the volumes of five VBs (L1–L5) and six IVDs (T12–L1 to L5–S1) [Figure 2]. The volumes of VB and IVD were obtained using all the MR slices through slice-by-slice summation of the products of the area of VB or IVD times the slice thickness n (V = thickness × i = 1areai), where the inter-slice gap was incorporated into the thickness. The wedge index (Ha/Hp), biconcavity index {[(Ha + Hp)/2]/Hm} of VB, and biconvexity index {Hm/[(Ha + Hp)/2]}of IVD were calculated as well.
Figure 2: T2W Sagittal MR Image Showing Measurements of Lumbar VB and IVD - Disc AH, Disc MH, Disc PH, and Disc AP (blue lines); Vertebra AH, MH, PH, and AP (Yellow Lines); Vertebral Area (Pink Line) and Disc Area (Green Line). AH Denotes Anterior Height; MH, Middle Height; PH, Posterior Height; AP, Anterior Posterior Dimension.

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Analysis of the summated results of the five VBs (L1–L5) and six related discs (T12–L1 to L5–S1) for each subject, as well as each VB and IVD, was performed. Continuous variables were examined by analysis of variance and analysis of covariance, with adjustment for height and age. The P value for trend, which tests the increasing or decreasing linear trend of group, is tested for the trend across the ordinal groups in this study.[13] Probability level of 5% was used as the level of significance.

  Results Top

The age of the subjects ranged between 40 and 70 years, with most in their fifth decade (28%) followed by sixth decade (23%), together constituting 51.66% of the study group. The most common symptom was backache (100%) with or without other symptoms such as radiating pain from the lower back to legs (53%) and pain in other joints (12%).

Based on the T-scores, as measured on DEXA, the subjects were divided into three groups i.e. normal, osteopenia and osteoporosis. The number of male and female subjects were 39.5.%, 41.9%, 18.6% and 22.8%, 45.7%, 31.5% in normal, osteopenia and osteoporosis groups, respectively [Table 1].
Table 1: Age and Gender Distribution with Changes in BMD in Three Groups (Normal, Osteopenia and Osteoporosis)

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The VB morphometric changes among the three groups in both genders showed a significant decreasing trend in Ha, Hm, and Hp with the reduction in BMD. The decrease in BMD also led to an increased biconcavity index in the lumbar VBs [Table 2]. The IVD morphometric changes among various groups showed a significant decreasing trend in Ha and Hp; however Hm showed a significant increasing trend in both genders [Figure 3] along with the increase in biconvexity index [Table 3]. The wedge index of vertebra and disc was also affected by a reduction of BMD. The lumbar VB and disc volume also showed a decreasing trend as the BMD decreased which was significant (P < 0.0005) for both men and women [Table 4].
Table 2: Measurement for Lumbar Vertebral Bodies (n=5) Among Normal Bone Mineral Density, Osteopenia, and Osteoporosis Groups

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Figure 3: T2W Sagittal MR Image of an Osteoporotic Patient Showing Morphological Changes in the IVD in the form of Increased Middle Height and Decrease in Anterior and Posterior Heights. The T12 to L5 Vertebral Bodies also Show Decrease in Vertical Height Leading to Increased Biconcavity Index and Overall Decrease in Volume of Both Discs and Vertebral Bodies.

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Table 3: Measurement for Intervertebral Disc (n=6) Among Normal Bone Mineral Density, Osteopenia, and Osteoporosis Groups

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Table 4: Vertebrae and Disc Volumes Among Normal Bone Mineral Density, Osteopenia, and Osteoporosis Groups

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  Discussion Top

The present study evaluated the applications of MRI in morphometric assessment of VB and IVD in tandem with diminution of BMD to establish standard measurement protocol yielding excellent intra-and inter-observer measurement reliability. Previous studies have largely focused on the effect of osteoporosis on the morphology of VBs; however, this study evidently shows that non-osseous tissues such as IVDs are affected with decrease in BMD.

The age of the subjects in the present study ranged between 40-70 yrs, maximum belonging to the 5th decade (28%) followed by 6th decade (23%). Although it is said that bone loss in a universal phenomenon that starts from the time peak bone mass is achieved, most studies have assessed bone health status in postmenopausal women and men above 50 years of age. However, few recent studies have shown that bone loss starts from the age of 30-40 years in both men and women.[14] Considering the sociodemographic and lifestyle factors such as nutrition, educational status and occupation of our study population, the onset of bone loss was seen at a relatively younger age. Studies indicate that oseoporosis and osteopenia.[15] or low bone mass may occur at a relatively younger age in Indian population.[15],[16] The number of subjects in the present study in three groups (normal, osteopenia, osteoporosis) were 39.5%, 41.9%, 18.6% in males and 22.8%, 45.7%, 31.5% in females, respectively. On the contrary the number of subjects were 59.5%, 24.1%, 16.5% in males and 23.9%, 34.0%, 42.1% in females in the study conducted by Anthony WL Kwok et al.[17]. In this study, the VBs showed a decrease in Ha, Hm and HP values along with an increase in biconcavity index (P < 0.001), with reduction in BMD. This is consistent with the study by Twomey and Taylor[18], which established that a reduction in BMD leads to weakening of horizontal trabeculae and consequently, the vertebra become concave as the discs remain firmer than the unsupported osteoporotic vertebral endplates. However, these results markedly vary from those reported by Yang et al.[11] — the anterior vertebral height in the lumbar region is larger in patients possibly because of their small sample size and the use of radiographic equipment. The MRI data used in this study enable sectional and VB and IVD volume assessment.

Consistent with the study of Roberts et al.[19] this study showed a statistically significant increase in the biconvexity index of IVD owing to increased Hm and decreased Ha and Hp along with a decrease in BMD [Figure 3]. This in turn suggests that the morphometric changes in the IVDs are dependent on the osseous strength of the VBs or vice versa. However, a few reports state quite contrastingly that osteoporosis does not affect the anterior and posterior disc heights among the elderly subjects.[11] The effect of osteoporosis on the IVDs still remains debatable.[20],[21],[22] However, these earlier studies did not include volumes. In the present study, with decrease in BMD, there was an overall decreasing trend in disc volume, despite the increase in Hm.

The mechanical interaction between the disc and adjacent vertebrae have been examined in a number of studies.[23] A positive correlation between the thickness of the subchondral endplates of the vertebrae and the proteoglycan content of the disc has been shown.[19] However, this association could be altered in osteoporotic spines, as the increase in endplate porosity leads to changes in the nutritional pathway of the disc.[24] The nutritional supply of the disc from the adjoining vertebrae might be compromised with reduction in BMD.[25],[26],[27] Thus, the disc expansion observed in this study could be attributed to the changes in the nutritional pathway, although further studies are required to test this hypothesis.

This study is one among the few investigating on the effect of osteoporosis on the morphology of the lumbar IVDs using quantitative MRI data. Statistical power could be amplified with higher sample sizes in future studies. As osteoporosis depends on ethnic backgrounds[28] and the subjects in this study belong to a homogeneous adult Indian population, the limitation whether these results can be extrapolated to other ethnic groups remains to be further validated. Future studies should be large and multi-centric including subjects of diverse ages, gender, socioeconomic strata and ethnicity using standard techniques to ascertain these results.

  Conclusions Top

MRI can enable quantitative evaluation of BMD in vivo and morphometric analysis of VB and IVD holds a significant place in the diagnostic algorithm of osteoporosis. Furthermore, the statistical significance of morphometric analysis is comparable to that of the BMD assessed using the hitherto gold standard DEXA without entailing any radiation. Morphological changes in lumbar VB and IVD observed on MRI had linear relationship with the change in BMD. This cross-sectional study shows that the decline in BMD is associated with a decrease in VB height leading to an increase in biconcavity index and with respect to IVD, a decrease in Ha and Hp along with an increase in Hm leads to an increased biconvexity index. There is an overall decreasing trend in both VB and IVD volumes with the decline in BMD. These results will be valuable for further understanding of the pathophysiological changes as well as the biomechanical changes in the spine that accompany osteoporosis.


We wish to thank the participants of the study and the staff in the Department of Radiodiagnosis, VMMC and Safdarjung Hospital for their support and cooperation throughout the study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3]

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


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