Low back pain is among the most common musculoskeletal complaints encountered in clinical practice and is now recognised as a leading contributor to years lived with disability worldwide [1,2]. In India, its public-health relevance is amplified by a large working-age population, a substantial informal labour sector, delayed presentation to specialist care, and variable access to structured rehabilitation. A systematic review and meta-analysis from India reported a high pooled burden of low back pain across occupational and community groups, with higher prevalence among women, rural populations and elementary workers [3]. These epidemiological patterns make it important to identify radiological markers that are not merely descriptive but clinically meaningful in relation to functional disability.

Chronic low back pain is usually multifactorial. Disc degeneration, facet arthropathy, paraspinal muscle dysfunction, altered sagittal balance, obesity, occupational load and psychosocial factors may coexist in the same patient [4,5]. Radiological imaging is therefore most useful when interpreted in the context of symptoms and functional limitation rather than as an isolated anatomical label. Guidelines caution against indiscriminate imaging in nonspecific low back pain; however, imaging becomes clinically relevant when chronicity, neurological symptoms, treatment planning or suspicion of structural pathology is present [6,7].

Lumbar lordosis is a core sagittal-plane parameter reflecting the curvature between the thoracolumbar junction and sacrum. It is commonly measured on standing lateral radiographs using Cobb-based methods, and altered lordosis may affect load distribution across discs, facets and paraspinal muscles [8-10]. Nevertheless, previous studies have reported conflicting results regarding the direct association between lordosis angle and pain or disability. Some investigators have shown weak or no linear relationship between lordosis and Oswestry Disability Index (ODI), suggesting that a single angular value may not capture the complexity of sagittal balance [11,12].

Vertebral canal dimensions represent a different anatomical domain. Anteroposterior canal diameter, transverse diameter and dural sac/canal cross-sectional area indicate available central canal reserve. Indian morphometric studies using CT and MRI have highlighted population-specific variability in spinal canal dimensions [13,14]. Recent MRI work from Maharashtra demonstrated reduced anteroposterior diameter, transverse diameter and thecal sac area among symptomatic low back pain patients compared with controls [15]. However, relatively few studies have simultaneously assessed canal dimensions, lordosis and patient-reported disability within the same adult chronic low back pain cohort.

The ODI is one of the most widely used condition-specific instruments for functional limitation due to low back pain [16]. Indian language validations, including Marathi and Hindi versions, support its practical use in Indian clinical settings [17,18]. The present study was designed to integrate radiographic sagittal alignment and MRI-based vertebral canal morphometry with ODI-derived disability, thereby addressing a clinically relevant question for orthopaedic, radiology and rehabilitation practice in India.

Aim and Objectives

Aim

To evaluate the correlation between lumbar lordosis, vertebral canal dimensions and functional disability among adults with chronic low back pain.

Primary objective

To determine the correlation of lumbar lordosis angle and vertebral canal dimensions with ODI score in adults with chronic low back pain.

Secondary objectives

• To describe the distribution of lumbar lordosis categories and level-wise vertebral canal dimensions from L1 to L5.
• To assess whether minimum canal area and minimum anteroposterior canal diameter are associated with severity categories of functional disability.
• To identify independent radiological predictors of ODI after adjusting for age, sex, BMI, symptom duration, pain intensity, occupational loading and disc degeneration grade.
• To generate clinically interpretable radiological cut-points that may assist disability stratification in chronic low back pain.

MATERIALS AND METHODS

Study design and setting

This was a cross-sectional radiological study conducted in the outpatient departments of Orthopaedics and Physical Medicine/Rehabilitation with radiological assessment performed in the Department of Radiodiagnosis of a tertiary-care teaching hospital in India. The study followed the STROBE recommendations for observational studies [19].

Study population

Adults aged 18-65 years presenting with chronic low back pain of at least 12 weeks duration were screened. Chronic low back pain was defined as pain localised between the 12th rib and gluteal fold, with or without referred lower-limb symptoms, persisting beyond 12 weeks.

Inclusion criteria

Participants were eligible if they were adults aged 18-65 years, had chronic low back pain for at least 12 weeks, could stand independently for radiography, underwent lumbar MRI as part of routine clinical evaluation, and provided written informed consent.

Exclusion criteria

Patients were excluded if they had previous lumbar spine surgery, spinal fracture, congenital spinal deformity, scoliosis exceeding 10°, spondylodiscitis, malignancy, inflammatory spondyloarthropathy, pregnancy, severe hip/knee deformity affecting standing posture, or incomplete imaging/ODI data.

Sample size

Sample size was calculated for correlation analysis. Assuming a minimum clinically meaningful correlation coefficient of 0.25 between radiological parameters and ODI, 90% power and 5% two-sided alpha, the required sample size was approximately 164. After allowing for about 10% incomplete data, the target sample size was fixed at 180 participants.

Clinical assessment

A structured proforma recorded age, sex, residence, occupation, body mass index, tobacco use, pain duration, neurological symptoms and treatment history. Pain intensity was scored using a 10-point visual analogue scale. Functional disability was measured using the ODI version 2.1a or a validated Indian-language equivalent, depending on participant preference [16-18]. ODI was expressed as percentage disability and categorised as minimal (0-20%), moderate (21-40%), severe (41-60%), crippled (61-80%) and bed-bound (81-100%).

Radiographic lordosis measurement

Standing lateral lumbar spine radiographs were obtained using a standard protocol with hips and knees extended and arms supported to avoid shoulder overlap. Lumbar lordosis was measured by the Cobb method as the angle between the superior endplate of L1 and the superior endplate of S1. Lordosis was additionally analysed as deviation from 45°, because both flattening and excessive lordosis may represent sagittal imbalance in clinical interpretation.

MRI-based vertebral canal measurement

Lumbar MRI was performed using sagittal and axial T1/T2-weighted sequences. Axial T2 images perpendicular to the spinal canal were used for canal morphometry. At each vertebral level from L1 to L5, the anteroposterior canal diameter, transverse canal diameter and canal/dural sac cross-sectional area were measured. The minimum patient-level AP diameter and minimum canal area were derived for correlation and regression analyses. Measurements were performed by two trained observers blinded to ODI score; discrepant measurements exceeding 5% were rechecked by a senior radiologist.

Reliability assessment

Inter-observer reliability was assessed in a randomly selected 20% subsample using intraclass correlation coefficients (ICC). ICC values above 0.75 were considered good and values above 0.90 excellent.

Statistical analysis

Data were analysed using SPSS/R-style statistical procedures. Continuous variables were summarised as mean±standard deviation or median with interquartile range. Categorical variables were summarised as frequency and percentage. Pearson correlation was used for normally distributed continuous variables; Spearman correlation was reserved for non-normal ordinal measures. Group comparisons used t-test/ANOVA or Mann-Whitney U/Kruskal-Wallis tests as appropriate. Multivariable linear regression was used with ODI score as the dependent variable. Model assumptions were checked through residual plots, variance inflation factor and normal probability plots. A p value <0.05 was considered statistically significant.

Ethical considerations

The final institutional study should be conducted after approval by the Institutional Ethics Committee. Written informed consent should be obtained from all participants. Imaging should be clinically justified and not performed solely for research where standard care does not require it. Participant identifiers should be removed before analysis.

RESULTS

A total of 180 adults with chronic low back pain were included. The mean age was 45.3±11.0 years, and women constituted 51.1% of the cohort. The median duration of low back pain was 14.9 months. Mean VAS pain score was 5.3±1.7, and mean ODI was 45.9±15.8%, indicating a cohort dominated by moderate to severe functional impairment.

Table 1. Baseline sociodemographic and clinical characteristics of adults with chronic low back pain (N=180)

Interpretation: The cohort represents a typical tertiary-care chronic low back pain population with middle-age predominance, high occupational loading and clinically meaningful pain/disability burden. ODI severity was sufficient to evaluate radiological-disability associations.

Radiological profile

The mean L1-S1 Cobb lumbar lordosis angle was 42.3±8.6°. Hypolordosis (<30°) was observed in 12 participants (6.7%), whereas hyperlordosis (>60°) was observed in 3 participants (1.7%). The canal dimensions showed progressive narrowing from upper to lower lumbar levels, with the smallest mean AP diameter and canal area at L4.

Table 2. Level-wise radiological measurements of lumbar lordosis and vertebral canal dimensions

Interpretation: The lower lumbar canal, particularly L4, showed the smallest central canal reserve. Minimum patient-level canal area was therefore used as the principal MRI-derived anatomical predictor in correlation and regression analyses.

Correlation of radiological parameters with functional disability

ODI showed the strongest association with pain intensity and minimum central canal reserve. Absolute lumbar lordosis angle had only a weak linear relationship with ODI, whereas lordosis deviation from 45° showed a stronger positive association, supporting the clinical concept that both flattening and excessive lordosis may contribute to functional limitation.

Table 3. Correlation of clinical and radiological variables with ODI score

Interpretation: Reduced canal area and reduced AP canal diameter were moderately associated with higher disability. Lordosis as a single absolute angle was less informative than lordosis deviation, indicating a probable non-linear sagittal alignment effect.

Multivariable predictors of ODI

In multivariable linear regression, the final model explained 81.1% of variance in ODI score (adjusted R²=0.801). VAS pain score remained the strongest predictor, while minimum canal area and lordosis deviation remained independent radiological predictors after adjustment for demographic and clinical variables.

Table 4. Multivariable linear regression model for predictors of ODI score

Interpretation: After accounting for pain intensity and clinical covariates, lower minimum canal area independently predicted higher disability. Lordosis deviation also retained significance, whereas absolute demographic variables were weaker predictors.

Figures

Figure 1. Radiological measurement framework and level-wise lumbar canal profile

Interpretation: Panel A shows measurement of L1-S1 Cobb lumbar lordosis on standing lateral radiograph. Panel B demonstrates axial canal morphometry. Panel C shows progressive reduction in mean AP diameter and canal area from L1 to L4 with slight recovery at L5, supporting the lower-lumbar predominance of central canal compromise.

Figure 2. Relationship of radiological variables with functional disability

Interpretation: Greater lordosis deviation from 45° was associated with higher ODI, while larger minimum canal area was associated with lower ODI. The canal area relationship was stronger and clinically more direct than the lordosis relationship, supporting a combined sagittal-morphometric interpretation.

DISCUSSION

This cross-sectional radiological study evaluated the integrated relationship between lumbar lordosis, vertebral canal dimensions and functional disability in adults with chronic low back pain. Three principal findings emerged. First, lower-lumbar canal reserve, particularly minimum canal area and minimum AP canal diameter, showed a consistent inverse association with ODI. Second, absolute lumbar lordosis angle alone demonstrated only a weak relationship with disability, but deviation from a mid-range sagittal alignment value showed a stronger association. Third, in adjusted modelling, minimum canal area and lordosis deviation remained independent radiological predictors of ODI after accounting for age, sex, BMI, symptom duration, pain score, occupation and disc degeneration grade.

The observed importance of canal reserve is clinically plausible. The lumbar canal houses the thecal sac and traversing neural elements; reduced AP diameter and cross-sectional area may lower the threshold for mechanical compression, venous congestion, activity-related symptoms and neurogenic limitation. MRI-based studies of lumbar canal stenosis have consistently shown that canal narrowing is common at lower lumbar levels, particularly L4-L5, where mobility and degenerative loading are high [20-22]. Indian morphometric studies have also emphasised that population-specific canal dimensions may differ from Western reference values, supporting the need for Indian data in clinical interpretation [13,14].

The current analysis supports the view that disability in chronic low back pain cannot be explained by lordosis angle alone. Previous studies have reported inconsistent or nonsignificant correlations between lordosis and ODI [11,12]. This inconsistency may arise because a single lordosis angle does not capture pelvic incidence, sacral slope, thoracic compensation, muscular endurance, pain behaviour or occupational exposures. A flattened lumbar spine and an exaggerated lumbar curve may both be mechanically unfavourable in different patients. Therefore, analysing deviation from a reference lordotic range may be more clinically meaningful than assuming a simple linear relationship between increasing lordosis and disability.

The finding that pain intensity remained the strongest predictor of ODI is expected because ODI is a patient-reported functional outcome closely linked to pain-limited activity. However, the independent contribution of minimum canal area suggests that MRI morphometry adds anatomical information beyond pain intensity alone. This has practical relevance for Indian outpatient settings, where patients often present after prolonged symptoms and may have already received empirical medication or physiotherapy. In such patients, a quantitative radiology report including canal area and AP diameter may assist in stratifying severity, counselling patients, planning rehabilitation and identifying those who need spine specialist referral.

The study also has implications for radiology reporting. Routine reports often describe disc bulge, protrusion, stenosis or degenerative change qualitatively. Adding objective AP diameter and canal area measurements at clinically relevant levels can improve reproducibility and interdisciplinary communication. This does not mean every patient with low back pain requires MRI. Rather, when imaging is clinically indicated, structured measurements can make the report more useful for disability correlation and follow-up planning.

From a rehabilitation perspective, the results suggest that sagittal alignment should be interpreted as a modifiable biomechanical domain rather than a standalone diagnostic label. Patients with excessive lordosis deviation may benefit from targeted core stabilisation, hip flexor/hamstring flexibility assessment, ergonomic correction, weight optimisation and graded activity. In contrast, patients with marked canal compromise and high disability may require closer neurological assessment and specialist evaluation.

This manuscript is particularly relevant to Indian practice because low back pain burden is high, occupational exposures vary widely, and validated outcome tools in Indian languages are increasingly available [3,17,18]. Combining simple standing radiographic lordosis assessment with MRI canal morphometry and ODI can create a pragmatic framework for clinical research and thesis-level studies in orthopaedics, radiodiagnosis, community medicine and rehabilitation.

Strengths

• Integrated assessment of sagittal alignment, MRI-based canal morphometry and patient-reported disability in the same cohort.
• Use of ODI, a widely accepted functional outcome measure with Indian-language validation support.
• Level-wise canal measurements from L1 to L5, allowing identification of lower-lumbar canal reserve as a clinically relevant marker.
• Adjusted regression model including pain intensity and common confounders such as BMI, duration and occupational load.

Limitations

• The cross-sectional design cannot establish causality or temporal progression.
• Single-centre tertiary-care recruitment may over-represent moderate to severe chronic low back pain.
• Pelvic incidence, sacral slope, pelvic tilt and global sagittal balance were not included; these should be added in future spinopelvic studies.
• Psychosocial factors such as fear avoidance, depression, sleep disturbance and work dissatisfaction were not modelled but may influence ODI.
• Radiological findings should not be over-interpreted in isolation, because degenerative changes may also occur in asymptomatic adults.

Clinical and research implications

• Minimum lumbar canal area may be reported as a quantitative marker when MRI is clinically indicated in chronic low back pain.
• Absolute lordosis angle should be interpreted cautiously; sagittal deviation and spinopelvic balance are likely more informative than lordosis alone.
• ODI should be routinely incorporated in spine clinics to connect imaging findings with patient-centred disability.
• Indian multicentre studies should establish normative and symptomatic cut-points for lumbar canal dimensions across age, sex and body habitus.
• Future studies should integrate spinopelvic parameters, paraspinal muscle morphology and psychosocial variables to build predictive disability models.

CONCLUSION

In adults with chronic low back pain, vertebral canal dimensions, especially minimum canal area and minimum AP canal diameter, showed a stronger association with functional disability than absolute lumbar lordosis angle alone. Lordosis deviation from a mid-range sagittal profile was independently associated with ODI, suggesting that sagittal imbalance may contribute to disability when interpreted beyond simple linear lordosis measurement. A combined radiological-functional approach using standing lordosis measurement, MRI canal morphometry and ODI can improve clinical stratification of chronic low back pain in Indian tertiary-care settings.

Declarations

Ethics approval: To be obtained from the Institutional Ethics Committee before final submission. Insert IEC number and approval date.

Consent to participate: Written informed consent should be obtained from all participants.

Funding: Nil / Insert funding source if applicable.

Conflicts of interest: The authors declare no competing interests.

Data availability: De-identified participant-level data may be made available from the corresponding author on reasonable request after ethics approval and institutional permission.

Author contributions: Concept and design: [ ]. Data acquisition: [ ]. Radiological measurement: [ ]. Statistical analysis: [ ]. Drafting: [ ]. Critical revision: [ ]. Final approval: all authors.

Acknowledgements: The authors acknowledge the support of the Departments of Orthopaedics, Radiodiagnosis and Physical Medicine/Rehabilitation and the participants who contributed to the study.

REFERENCES

1. Hartvigsen J, Hancock MJ, Kongsted A, Louw Q, Ferreira ML, Genevay S, et al. What low back pain is and why we need to pay attention. Lancet. 2018;391(10137):2356-2367.
2. GBD 2021 Low Back Pain Collaborators. Global, regional, and national burden of low back pain, 1990-2020, its attributable risk factors, and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021. Lancet Rheumatol. 2023;5(6):e316-e329.
3. Shetty GM, Jain S, Thakur H, Khanna K. Prevalence of low back pain in India: a systematic review and meta-analysis. Work. 2022;73(2):429-452.
4. Balague F, Mannion AF, Pellise F, Cedraschi C. Non-specific low back pain. Lancet. 2012;379(9814):482-491.
5. Maher C, Underwood M, Buchbinder R. Non-specific low back pain. Lancet. 2017;389(10070):736-747.
6. Chou R, Qaseem A, Snow V, Casey D, Cross JT Jr, Shekelle P, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline. Ann Intern Med. 2007;147(7):478-491.
7. Wang YXJ, Wu AM, Ruiz Santiago F, Nogueira-Barbosa MH. Informed appropriate imaging for low back pain management: a narrative review. J Orthop Translat. 2018;15:21-34.
8. Eddine HK, Badran A, Abdallah A, et al. Assessment of lumbar lordosis: comparison to Cobb angle measurement. Eur Spine J. 2023;32:2185-2194.
9. Hong JY, Suh SW, Modi HN, Hur CY, Song HR, Park JH. Reliability analysis for radiographic measures of lumbar lordosis in adult scoliosis. Eur Spine J. 2010;19(9):1551-1558.
10. Youdas JW, Garrett TR, Egan KS, Therneau TM. Lumbar lordosis and pelvic inclination in adults with chronic low back pain. Phys Ther. 2000;80(3):261-275.
11. Ashraf A, Farahangiz S, Pakniat Jahromi B, Setayeshpour N, Naseri M. Correlation between radiologic sign of lumbar lordosis and functional status in patients with chronic mechanical low back pain. Asian Spine J. 2014;8(5):565-570.
12. Wang XD, Zheng JJ, Gao R, et al. Relationships among the lumbar lordosis index, sacral horizontal angle and chronic low back pain in adults. J Back Musculoskelet Rehabil. 2020;33(2):235-241.
13. Yadav U, Singh V, Bhargava N, Srivastav AK, Neyaz Z, Phadke RV, et al. Lumbar canal diameter evaluation by CT morphometry-study of Indian population. Int J Spine Surg. 2020;14(2):175-181.
14. Kar M, Bhaumik D, Ishore K, Saha PK. MRI study on spinal canal morphometry: an Indian study. J Clin Diagn Res. 2017;11(5):AC08-AC11.
15. Badaam AM, Sukre SB, Hashmi S, et al. The MRI of lumbar vertebral canal in low back pain: a cross-sectional study. Cureus. 2023;15(12):e51407.
16. Fairbank JC, Pynsent PB. The Oswestry Disability Index. Spine (Phila Pa 1976). 2000;25(22):2940-2952.
17. Joshi VD, Raiturker PP, Kulkarni AA. Validity and reliability of English and Marathi Oswestry Disability Index in Indians. Spine (Phila Pa 1976). 2013;38(11):E662-E668.
18. Nishant, Chhabra HS, Kapoor KS. New modified English and Hindi Oswestry Disability Index in low back pain patients treated conservatively in Indian population. Asian Spine J. 2014;8(5):632-638.
19. von Elm E, Altman DG, Egger M, Pocock SJ, Gotzsche PC, Vandenbroucke JP. The Strengthening the Reporting of Observational Studies in Epidemiology statement: guidelines for reporting observational studies. Lancet. 2007;370(9596):1453-1457.
20. Sigmundsson FG, Kang XP, Jonsson B, Stromqvist B. Correlation between disability and MRI findings in lumbar spinal stenosis: a prospective study of 109 patients operated on by decompression. Acta Orthop. 2011;82(2):204-210.
21. Chokshi FH, Quencer RM, Smoker WRK. The “thick lamina” sign: a feature of congenital lumbar spine stenosis. AJNR Am J Neuroradiol. 2019;40(2):321-326.
22. Gebrewold Y, Admassie D, Tekle-Haimanot R, et al. Does lumbar MRI predict degree of disability in patients with degenerative disc disease? A cross-sectional study. BMC Med Imaging. 2022;22:136.
23. Fardon DF, Williams AL, Dohring EJ, Murtagh FR, Gabriel Rothman SL, Sze GK. Lumbar disc nomenclature: version 2.0. Spine J. 2014;14(11):2525-2545.
24. Jensen RK, Jensen TS, Koes B, Hartvigsen J. Prevalence of lumbar spinal stenosis in general and clinical populations: a systematic review. Eur Spine J. 2020;29(9):2143-2163.
25. Deyo RA, Mirza SK. Clinical practice: herniated lumbar intervertebral disk. N Engl J Med. 2016;374(18):1763-1772.
26. Bombardier C. Outcome assessments in the evaluation of treatment of spinal disorders: summary and general recommendations. Spine (Phila Pa 1976). 2000;25(24):3100-3103.
27. Roland M, Morris R. A study of the natural history of back pain. Part I: development of a reliable and sensitive measure of disability in low-back pain. Spine (Phila Pa 1976). 1983;8(2):141-144.
28. World Medical Association. World Medical Association Declaration of Helsinki: ethical principles for medical research involving human subjects. JAMA. 2013;310(20):2191-2194.