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BACKGROUND: A lumbar disc herniation (LDH) is a localised displacement of disc material, which may initiate changes in the disc and adjacent structures such as the nerve root and the spinal canal. Knowledge about how morphological changes in the disc relate to changes in other spinal structures might give the clinician a better understanding of the natural history and consequences of lumbar disc herniations. However, few longitudinal studies have investigated this process using reliable measures from magnetic resonance imaging (MRI). The objectives of this study were to examine changes in and associations between the size of lumbar disc herniations, dural sac area and disc height over an eight-year period using MRI at three time-points.METHODS: Individuals from a population-based cohort, the 'Backs on Funen Cohort', had MRIs taken at age 41 years and again at 45 and 49 years. Only disc levels with MRI-confirmed disc herniations at 41 or 45 years were included. Cross-sectional areas (mm(2)) of the LDH, dural sac and disc height were calculated from measurements performed on sagittal T2-weighted images using a previously validated method. Changes over time for the three MRI findings were defined as "unchanged", "increased ", "decreased", or "fluctuating". Only changes beyond 95 % limits of agreement of the same measurements were regarded as valid. Associations between the three types of measures were examined cross-sectionally and longitudinally.RESULTS: One hundred and forty disc levels, from 106 people (48 women and 58 men), were included. Over eight years, 65 % of the herniations remained unchanged, 17.5 % decreased, 12.5 % increased, and 5 % had a fluctuating pattern. Increased herniation size was associated with decreased dural sac area (β-0.25[-0.52;0.01]) and increased disc height (β 0.35[0.14;0.56]). Moreover, larger herniation size predicted a statistically significant reduction in both dural sac area (β-0.35[-0.58;-0.13]) and disc height (β-0.50[-0.81;-0.20]).CONCLUSIONS: On average, most LDHs do not change over a four- to eight-year period. However, larger herniation size predicts a reduction in both dural sac area and disc height. Further research should be done to determine the correlations between the progression of LDH and resolution of patient symptoms.

Introduction and Aim. This study was based on the assumption that clinical and MRI finding which are strongly associated with the spondyloarthritis (SpA) disease entity, also are associated with each other. Therefore the objectives were to explore the prevalence of clinical SpA features and MRI findings and the association between these two domains. Methods. The study sample included patients aged 18-40 years with persistent low back pain, referred to a public Spine Centre. The prevalence of and associations between clinical SpA features (incl. HLA-B27and CRP) and MRI of the entire spine and sacroiliac joints (SIJ) were estimated and analysed. Results. Of the 1020 patients included in the study, 52% had ≥1 clinical SpA feature. The three most common SpA features were; inflammatory back pain, good response to NSAID and family disposition (15-17% each). SIJ bone marrow oedema (BMO) occurred in 21%. Although several SpA features, incl. HLAB27, were positively associated with MRI findings at the SIJ (OR ranging from 1.1-9.0), the three most common clinical SpA features were not. Several SIJ and spinal MRI findings, incl. severe SIJ BMO (sum-scores ≥3) and SIJ erosions, were associated with positive HLA-B27 (OR ranging from 3.1-24.5). Slight BMO (sum-score of 1) was, however, not associated with any SpA features. Conclusions. The high prevalence of both clinical SpA features and MRI findings and the lack of consistent associations between the two domains, indicate a need for further investigation of the diagnostic utility of SpA features and the minimum requirements of BMO for defining sacroiliitis.

Summary In patients with low back pain (LBP) it is only possible to diagnose a small proportion, (approximately 20%), on a patho-anatomical basis. Therefore, the identification of relevant LBP subgroups, preferably on a patho-anatomical basis, is strongly needed. Signal changes on MRI in the vertebral body marrow adjacent to the end plates also known as Modic changes (MC) are common in patients with LBP (18–58%) and is strongly associated with LBP. In asymptomatic persons the prevalence is 12–13%. MC are divided into three different types. Type 1 consists of fibro vascular tissue, type 2 is yellow fat, and type 3 is sclerotic bone. The temporal evolution of MC is uncertain, but the time span is years. Subchondral bone marrow signal changes associated with pain can be observed in different specific infectious, degenerative and immunological diseases such as osseous infections, osteoarthritis, ankylosing spondylitis and spondylarthritis. In the vertebrae, MC is seen in relation to vertebral fractures, spondylodiscitis, disc herniation, severe disc degeneration, injections with chymopapain, and acute Schmorl's impressions. The aim of this paper is to propose two possible pathogenetic mechanisms causing Modic changes. These are: A mechanical cause : Degeneration of the disc causes loss of soft nuclear material, reduced disc height and hydrostatic pressure, which increases the shear forces on the endplates and micro fractures may occur. The observed MC could represent oedema secondary to the fracture and subsequent inflammation, or a result of an inflammatory process from a toxic stimulus from the nucleus pulposus that seeps through the fractures. A bacterial cause : Following a tear in the outer fibres of the annulus e.g. disc herniation, new capilarisation and inflammation develop around the extruded nuclear material. Through this tissue it is possible for anaerobic bacteria to enter the anaerobic disc and in this environment cause a slowly developing low virulent infection. The MC could be the visible signs of the inflammation and oedema surrounding this infection, because the anaerobic bacteria cannot thrive in the highly aerobic environment of the MC type 1. Perspectives : One or both of the described mechanisms can – if proven – be of significant importance for this specific subgroup of patients with LBP. Hence, it would be possible to give a more precise and relevant diagnosis to 20–50% of patients with LBP and enable in the development of efficient treatments which might be antibiotics, special rehabilitation programmes, rest, stabilizing exercise, or surgical fixation, depending on the underlying cause for the MC.

Background Magnetic Resonance Imaging (MRI) is the gold standard for detailed visualisation of spinal pathological and degenerative processes, but the prevailing view is that such imaging findings have little or no clinical relevance for low back pain. This is because these findings appear to have little association with treatment effects in clinical populations, and mostly a weak association with the presence of pain in the general population. However, almost all research into these associations is based on the examination of individual MRI findings, despite its being very common for multiple MRI findings to coexist. Therefore, this proof-of-concept study investigated the capacity of a multivariable statistical method to identify clusters of MRI findings and for those clusters to be grouped into pathways of vertebral degeneration. Methods This study is a secondary analysis of data from 631 patients, from an outpatient spine clinic, who had been screened for inclusion in a randomised controlled trial. The available data created a total sample pool of 3,155 vertebral motion segments. The mean age of the cohort was 42 years (SD 10.8, range 18–73) and 54% were women. MRI images were quantitatively coded by an experienced musculoskeletal research radiologist using a detailed and standardised research MRI evaluation protocol that has demonstrated high reproducibility. Comprehensive MRI findings descriptive of the disco-vertebral component of lumbar vertebrae were clustered using Latent Class Analysis. Two pairs of researchers, each containing an experienced MRI researcher, then independently categorised the clusters into hypothetical pathoanatomic pathways based on the known histological changes of discovertebral degeneration. Results Twelve clusters of MRI findings were identified, described and grouped into five different hypothetical pathways of degeneration that appear to have face validity. Conclusions This study has shown that Latent Class Analysis can be used to identify clusters of MRI findings from people with LBP and that those clusters can be grouped into degenerative pathways that are biologically plausible. If these clusters of MRI findings are reproducible in other datasets of similar patients, they may form a stable platform to investigate the relationship between degenerative pathways and clinically important characteristics such as pain and activity limitation.