Age and disc degeneration in low back pain: automated analysis enables a magnetic resonance imaging comparison of large cross-sectional cohorts of symptomatic and asymptomatic subjects

Abstract

AbstractObjectivesWe aimed to improve understanding of the role of imaging in diagnosis of low back pain by determining the prevalence of age-related disc degeneration in asymptomatic and symptomatic subjects. Spinal MRIs of symptomatic and asymptomatic subjects were re-annotated onto the same objective grading system and prevalence of degenerative changes compared.MethodsIn an exploratory cross-sectional study, we compared the prevalence of disc degeneration between two large groups of anonymised females, 30-80yrs, viz a symptomatic group with chronic back pain (724) and an asymptomatic (701) group. We used a verified automated MRI annotation system to re-annotate their spinal MRIs and report degeneration on the Pfirrmann (1-5) scale, and other degenerative changes (herniation, endplate defects, marrow signs, spinal stenosis) as binary present/absent.ResultsSevere degenerative changes were significantly more prevalent in discs of symptomatics than asymptomatics in the lower (L4-S1) but not the upper (L1-L3) lumbar discs in subjects <60years. We found high co-existence of several degenerative features in both populations. Degeneration was minimal in around 30% of symptomatics < 50years.ConclusionsAutomated MRI provides a valuable means of rapidly comparing large MRI datasets. Here, through directly comparing MRI annotations on the same objective scales it enabled us to detect significant age and spinal-level related differences in the prevalence of degenerative features between asymptomatic and symptomatic populations. By distinguishing between symptomatics whose discs have structural defects, and symptomatics with minimal degenerative changes, MRI could provide a means of clinical stratification, and provide a useful pathway to investigate possible pain sources.Key messagesWhat is already known about this subject?Even though intervertebral disc degeneration, and degenerative changes such as disc herniations, are strongly associated with low back pain, the importance of disc degeneration in development of low back pain is questioned because these degenerative changes are seen in both those with and those without low back pain; spinal MRIs are thus thought to be of little clinical value.What does this study add?The study provides the first data on age-related degeneration in those without pain and shows the significant differences in prevalence between age-related and symptom-related disc degeneration.The study provides definitive data showing that severe disc degeneration is directly implicated in a significant proportion of those with chronic low back pain, with the association with pain strongly dependent on age and spinal levelHow might this impact on clinical practice or future developments?The study shows that even though severe disc degeneration is strongly associated with low back pain, 30% of younger (<50yrs) chronic low back pain patients have no evident disc degeneration detected by MRI, which is important information (currently not used) for clinicians in directing treatments (and perhaps a clearer reason for the proper use of scans).The study provides important information for those working on mechanisms, as it enables stratification between pathways of pain arising from structural defects in the disc, and those pain pathways in discs with no such structural change.