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Background: The development in size and type of lumbar disc herniation (LDH) over time is not fully understood. Furthermore, the relationship between MRI defined LDH and clinical symptoms may not always confer with each other. This may be due to the lack of knowledge about the natural history of morphological changes in the related structures. In order to better understand the relationships, we investigated the following objectives. 1) the changes of LDH size through quantitative measures from MRI images taken at three time points over an eight-year period, 2) the cross-sectional associations between sizes of LDH and area of dural sac as well as disc height, and 3) LDH as a predictor of changes in dural sac areas and disc height after four and eight years.Methods: The study sample was assembled using a population-based cohort study of 41 year olds called “Backs on Funen Cohort”. All individuals who had MRI confirmed LDH during the first four years period were included in the study. The individuals were followed for 8 years with MRIs taken at baseline, four years and eight years. Cross-sectional areas (mm2) of LDH, disc heights and dural sacs were calculated from measurements using sagittal T2 weighted images. Changes over time in LDH sizes were reported as “the same”, “increased “, “decreased”, or “fluctuating”. Beta-coefficients with 95% confidence intervals for cross-sectional and longitudinal analyses were obtained from linear regression adjusted for relevant covariates. Results: In total, 65% of disc levels remained the same size, 17.5% decreased, 12.5% increased, and 5% had a fluctuating pattern. There was a negative association between LDH size and dural sac size (β-0.25[ -0.52;0.01]), and a positive association for disc height(β 0.35[0.14;0.56]). LDH size predicted statistical significant reductions in dural sac area (β -0.35 [-0.58;-0.13] and disc height (β -0.50[-0.81;-0.20]. Conclusions: This study provides detailed knowledge about changes in LDH size over time and its association with dural sac and disc height. Most LDHs did not change in size over time. However, the size of LDH predicted future reduction of cross-sectional area of dural sac as well, as loss of disc height.

Background: Detailed information about the development of disc morphology over time could provide valuable knowledge about disc health when compared with clinical measures such as pain and activity limitation. However, a review of the available literature did not reveal any detailed and directly applicable description of quantitative methods for measuring lumbar disc herniations and related structures on sagittal MRIs. The objectives of this study were: 1) to develop methods for quantitative measures of intervertebral discs, lumbar disc herniations and dural sac/spinal canal using MRIs, 2) to evaluate the agreement of these methods, and 3) to identify factors in the measurement procedures that may compromise agreement.Methods: In this intra- and inter-rater agreement study, lumbar quantitative measurements were performed on magnetic resonance images from 32 participants from a study cohort representative of the Danish general population. A new method for quantitative measures of intervertebral discs and related structures was developed and systematically described. MRI-images were measured twice by one rater for intra-rater agreement and once by a second rater for inter-rater agreement. Length and volume measurements were conducted, and cross-sectional areas calculated from length measurements. Statistical analysis included Bland and Altman’s limits of agreement and weighted kappa analysis.Results: Acceptable to good agreement was found for intra-rater measurements and calculations, with limits of agreement ranging from 1.8% to 33.6% of mean values. Questionable to good agreement was found for inter-rater measurements and calculations, with limits of agreement ranging from 2.3% to 51.9% of mean values. An exception was found for volume measurements, which showed poor agreement. It was possible to identify two main causes compromising agreement, both of which related to uncertainty in point markings during measurements. Conclusions: Quantitative length measurements and CSA calculations showed good to excellent agreement, and are applicable for further use in a broader context. Quantitative volume measurements showed poor agreement and are not applicable for further use.