MRI Evaluation of Degenerative Lumbar Spine Disease in Young Adults: A Quantitative Evaluation of Risk Factors

Background Data: Evidently, there is an alarmingly increasing incidence of degenerative lumbar spine disease in adolescents and young adults. Hence, it is imperative to ascertain and identify the risk factors so that early lifestyle modifications can be done, and early lumbar spine degeneration can be prevented. Purpose: To study the array of MRI findings of degenerative lumbar spine disease in young adults and quantitatively evaluate the risk factors. Study Design: A prospective imaging case study. Patients and Methods: A total of 200 young adult patients between 21 and 30 years old presenting with low back pain were included in this study. MRI findings of 200 young adults were graded and quantitatively evaluated in relation to three risk factors, that is, physical activity, smoking, and BMI. Grading of intervertebral disc degeneration, lumbar facet joint degeneration, and foraminal stenosis was done. Results: Modic type II endplate changes and reduced T2 bright disc signal were the most common manifestations of spondylosis and intervertebral disc (IVD) degeneration, respectively. A correlation between obesity and increasing grades of disc degeneration was found to be most significant at a 95% confidence interval. A significant correlation was found between each of the risk factors (obesity, sedentary lifestyle, and smoking) and increasing grades of IVD degeneration and facet arthropathy with a p value of <0.05. Foraminal stenosis manifested a positive association with BMI at a 95 % confidence interval. Conclusion: This study could recognize a statistically significant correlation between lumbar DDD and physical activity, smoking, and BMI. Identification of causative lifestyle factors could help prevent the occurrence and progression of lumbar DDD. (2020ESJ214)


INTRODUCTION
Among the various causes of morbidity in young adult individuals aged ≤ 30, low back pain (LBP) is one of the most common causes ensuing reduced productivity and consumption of healthcare resources. 25 Degenerative changes of the lumbar spine are the foremost of underlying factors of LBP. 17,7 Various genes have been implicated in degenerative disc disease (DDD) including the ones encoding collagens, interleukin 1, aggrecan, vitamin D receptor, and matrix metalloproteinase3-(MMP-3). 14 Environmental risk factors responsible for DDD and its progression include age, occupational, back injuries, smoking, obesity, sedentary lifestyle, and lack of physical activity. 21, 10,16 Degeneration of the intervertebral disc, endplates, and vertebral bodies is part of physiological aging. The incessant technological advancement and materialism have ushered in an era of workaholics, competitiveness, and stress. This, of course, led to an increased pace of human body wear and tear and a myriad of mental and physical ailments. Various studies have brought to light a high prevalence of DDD in adolescents and young adults. 16 A positive association between obesity and backache has also been reported in the literature. 8,26 There is evidence to suggest that there is an increased incidence of LBP in adolescents and young adults with a history of long hours of sitting and reduced physical activity. 6,12 Hence, it is imperative to ascertain the causal factors for DDD so that early lifestyle modifications can be done and premature spine degeneration can be prevented. We could find only a few studies in the literature evaluating DDD in the young Indian population. 21, 3 We aim to study the array of MRI findings of lumbar degenerative disc disease in young adults and quantitatively evaluate the risk factors for this condition.

PATIENTS AND METHODS
Two hundred patients between 21 and 30 years of age presenting with LBP were prospectively included in this study. All the patients complained of moderate-to-severe back pain for at least four weeks. Detailed history of sciatica and LBP was taken, including onset, nature, course, severity, and aggravating and relieving factors of pain. The severity of pain was graded by the Visual Analogue Scale 9 (VAS). Screening tests such as straight leg raising, crossed straight leg raising, and testing strength and reflexes in the lower extremities were conducted. Patients with a spinal deformity, infection, trauma, congenital malformations, and primary canal stenosis were excluded from the study. The study was done in Maharishi Markandeshwar Institute of Medical Sciences and Research, Mullana, for a period of 6 months between January 2020 to June 2020. Baseline data on demographic and clinical characteristics were collected throughout the course of study on a predesigned performa. Detailed history regarding smoking (number of cigarettes per day) and number of hours of physical activity per day was taken. Anthropometric assessments recorded were weight (kg), height (meter), and body-mass index (BMI, Kg/m2). WHO criterion for BMI was referred to, which divides patients into four groups: underweight, normal, overweight, and obese. An individual is underweight if his BMI is below 18.5, normal if BMI is 18.5-24.9, overweight if BMI is 25-29.9, and obese if BMI ≥30. 18 For this study, we divided the patients into two groups: obese with BMI ≥30 and not obese with BMI 18.5-29.9. The physical activity was graded as active or sedentary. Active lifestyle was defined as adults doing at least 150 minutes of moderate-intensity aerobic physical activity in a week or 75 minutes of vigorousintensity aerobic physical activity in a week according to the WHO Global Recommendations on Physical Activity for Health, 2010. 19 Subjects were classified as smokers or nonsmokers for The EGYPTIAN SPINE Journal the third risk factor. Daily smokers, whatever the number of cigarettes they smoke, were included in this study as smokers.
MRI was independently reported by two radiologists, and the findings were tabulated.
Intervertebral disc degeneration and lumbar facet joint degeneration were graded as described by Pfirrman et al. 20 and Weishaupt et al. 27 , respectively. Grading of lumbar neural foraminal stenosis was done. 15 Any difference in opinion was solved by consensus.
The study was approved by the local ethics committee of the institute. Informed written consent was obtained from all patients, and the study was conducted in accordance with the Declaration of Helsinki. 2 The confidentiality of any individual or the institution was not breached.
The study in no way involved experimentation on human or animal subjects. The procedure (MRI) that was carried out is routinely done on LBP subjects, and no new intervention was done for this study. The ethical issues in the study have been paid due attention to, and the study did not delay any residents from performing their duties.

Statistical Analysis
The data were analyzed with SPSS software version 20. Descriptive statistics (percentage, mean, median, and mode) were calculated. Chisquare test was used to determine the statistical difference between variables. Crude odds ratio (OR) and adjusted OR were calculated. The level of significance was fixed at <0.05 at a 95% confidence interval (CI).

RESULTS
Of the 200 patients suffering from LBP of moderate-to-severe degree for a minimum of 4 weeks who were referred for spine MRI, 140 were male and 60 females. The mean VAS of LBP was 6.7 ± 2. The mean age was 26 ± 8 (range, 21-30).  (Table 1).        left paracentral disc protrusion at L5-S1 level indenting the thecal sac with compression of left S1 traversing nerve root in the lateral recess, with reduced disc height at this level (solid arrow). A disc bulge is also seen at L4-L5 level (arrow) with disc desiccation changes at L4-L5 and L5-S1 levels.

DISCUSSION
MRI is the first-line investigation performed for DDD of the lumbar spine. The role of imaging is to accurately assess the cause of the patient's pain based on which clinicians can choose a treatment option. The imaging features of the DDD of the spine include intervertebral disc degeneration assessed as reduced signal intensity, disc bulge, protrusion, or extrusion. The non-disc changes include nerve root indentation or compression, endplate changes, Modic changes, foraminal stenosis, facet arthropathy, and annular tears. In this study, we assessed the degree of degeneration of the spine in young adults in relation to three risk factors, that is, obesity, sedentary lifestyle, and smoking. MRI changes of DDD were seen in 56% of the patients presenting with LBP in our study. Samartzis et al. 22 found disc degeneration in 35% of subjects between 13 and 29 years old without spinal deformity. Another study conducted by Al-Saeed et al. 1 on a young Arab population concluded that 65% of symptomatic subjects had MRI changes of lumbar spine degeneration. In a Finnish study by Takatalo et al. 26 , 47% of subjects between 20 and 22 years old were found to have DDD. Another study done by Savage et al. 23 found 34% of subjects between 20 and 30 years of age and 59% between 31 and59 years to be having DDD on MRI.
In this study, 57.9 % of patients had multilevel disease. The lower two lumbar levels (L4-L5 and L5-S1) were seen to be the most commonly involved (30.3% of patients). This observation was comparable with those made by Al-Saeed et al. 1 and Takatalo et al. 26 in their studies. Features on MRI such as reduced IVD signal intensity, reduced disc height, changes in disc contour, and nerve root compromise were also in agreement with the study done by Al-Saeed et al. 1 Regarding the effects of obesity on the spine, our study depicted that 60% of patients with BMI >30 have changes on MRI. Several mechanisms are responsible for the effect of obesity on DDD. Obesity could result in serious postural changes that affect loading on joints and thus result in long-term adverse effects on bones and joints. All these changes result in greater degeneration and overloading of the spine and produce higher compressive forces contributing to LBP. Many other studies also found a significant correlation between obesity and LBP. In a study done by Samartzis et al. 22 , the presence of juvenile disc degeneration was strongly associated with overweight and obesity. It also inhibits the activity of alpha-1-antiprotease, the most potent protease inhibitor. Through these two mechanisms, it increases proteolytic activity. This high serum proteolytic activity speeds up the degenerative process and weakens the spinal ligaments. 11 A study done on young adults (18-35 years) in India identified various risk factors associated with LBP but could not determine the association between smoking and alcoholism and LBP. However, many other risk factors such as marital status, family history or previous history of spine problems, strenuous exercise, stress, and increased hours of studying hours were found to be statistically significant causes of LBP. 15 Another Indian study by Barani et al. 3 found out that 22.2% of their patients between the ages of 20-40 years who presented with a history of LBP were smokers, and all of them had degenerative disc changes on MRI. A study on the effects of smoking on twins demonstrated a small increase in disc degeneration associated with smoking. 4 This study has some limitations such as the small sample size and the lack of a control group that is why we recommend a large sample size study with further dynamic X-ray to exclude instability.

CONCLUSION
The data of this study showed a statistically significant correlation between DDD and obesity, sedentary lifestyle, and smoking. Identification of causative lifestyle risk factors that affect DDD could help prevent the occurrence and/or progression of this condition.