For the past 30 years, the “conventional” T2-weighted magnetic resonance imaging (MRI) has been broadly used to diagnose low back pain. However, this is not a highly-sensitive or reliable tool and, as such, may not be useful to identify the cause and treatment of low back pain. A study led by the Department of Orthopaedics and Traumatology, Li Ka Shing Faculty of Medicine, The University of Hong Kong (HKU), Hong Kong, is first to report that the ultra-short time-to-echo disc sign (UDS) was found to be significantly related to degenerative spine changes, low back pain and disability in comparison to conventional magnetic resonance (MRI) imaging. The research was published in Spine.
Although low back pain is a multifactorial complex disorder, several studies have noted lumbar disc degeneration as a risk factor. For the past 30 years, “conventional” T2-weighted MRI has been used to assess the spinal discs and spine degeneration. The modality’s shortcomings may provide a rationale as to why it is common to find symptomatic individuals with seemingly non-degenerated discs and asymptomatic individuals with degenerative disc changes on conventional MRI. This may offer some explanation as to the problems of identification, diagnosis and outcomes of low back pain.
Over the past decade, various novel MRI technologies have been developed in an effort to address more sensitive measures to assess spine degeneration. One such imaging technology is the ultra-short time-to-echo (UTE) MRI. UTE MRI assesses MRI signal from short T2 components that are not detected on conventional T2-weighted MRI. It can be performed on any MRI machine and takes approximately 15-20 minutes to scan the lumbar spine of one individual. Utilising UTE MRI, the research team has identified a new disc biomarker, called the UTE disc sign (UDS), and evaluated its clinical importance.
This study is the first to report the finding and clinical relevance in humans of the UDS on MRI. According to authors, the UDS is a novel, reliable and simple MRI biomarker to assess the intervertebral lumbar discs, its relationship with other findings of spine degeneration, and its implications upon low back pain and disability.
The UDS was found to be significantly related to degenerative spine changes, low back pain and disability in comparison to conventional MRI imaging. The authors believe that the UDS may serve as a new imaging marker that may have potential implications in diagnostic, therapeutic and prognostic platforms in patients presenting with LBP or possibly be able to predict the development and severity of pain. The UDS may also shed light upon the pathomechanism of spinal disc changes that may become painful.
One hundred and eight (108) Southern Chinese participants were recruited (mean age: 52 years, equal number of male and female subjects). T2-weighted MRI was used to assess disc degeneration and other phenotypes, and T1-rho MRI values represented quantitative proteoglycan content (ie. water) of the disc. UDS was detected on UTE as a hyper- or hypo-intense band across a disc. The cumulative number of UDS levels represented a UDS score, whereas summated degenerated scores of lumbar levels via T2-weighted MRI represented a cumulative disc degeneration score. Subject demographics, low back pain every day (chronic) in the past year and disability profiles (Oswestry Disability Index, ODI) were obtained.
“Our study provides the ‘missing link’ between imaging findings of the spine and the development of low back pain”
The UDS was noted in 39.8% subjects, of which 61.4% occurred at the lower lumbar levels. Subjects with UDS had significantly more disc degeneration and levels with pathologic changes of the vertebral bodies (i.e. Modic changes). Based on disc levels, a higher prevalence of disc degeneration and disc bulges/protrusions, Modic changes and spondylolisthesis (i.e. slippage of the vertebral body) were noted in UDS discs than non-UDS discs (p<0.05). T1-rho values were lower in UDS discs than non-UDS discs (p=0.022). The majority of UDS could not be detected on conventional T2-weighted MRI. The UDS score was significantly correlated with worse ODI scores (r=0.311; p=0.001) and pain (p=0.009), whereas T2-weighted cumulative disc degeneration score was not (ODI: r=0.13; p=0.19, low back pain: p=0.127). Thirty-nine point five per cent of UDS subjects who had multi-level involvement also had a higher prevalence of low back pian (p<0.015), however this correlation was not found on T2-weighted MRI (p=0.53).
According to the lead investigator, Dino Samartzis, associate professor of the department, “For the past 30 years, it has been argued time and time again that findings on conventional MRI or imaging that are commonly used worldwide are not strongly related to low back pain or disability. Many clinicians and scientists have often questioned the practical use of having patients undergo such costly conventional imaging to determine the source of pain and that degenerative disc findings are commonplace among individuals who are also not in pain. Our study provides the ‘missing link’ between imaging findings of the spine and the development of LBP and disability.”
“UTE MRI is the only sequence so far in our study that showed definite correlation between back pain, disability and degenerative disc changes”
Samartzis further notes that “using UTE MRI has allowed us an opportunity to identify ‘hidden’ degenerative disc findings in an easy, quick and reliable fashion that helps us understand what is going on within the spinal discs much better than ever before. This has also led us to understand why someone may develop low back pain and if the pain may indeed have its ‘origins’ within the disc.”
Henry Pang, Master of Research in Medicine student in the department and first author of the study, further notes that “Among various MRI sequences, UTE MRI is the only sequence so far in our study that showed definite correlation between back pain, disability and degenerative disc changes. At the same time, as our study group unveils the previously hidden pathologies in traditional MRI, these findings may promote further understanding in the pathologies and therapies for low back pain and lumbar degeneration.”
Future study plans are underway to identify what these UDS findings truly represent and how they contribute to the mechanism of low back pain, as well as predicting future episodes of pain. Further initiatives are also being planned to address large-scale, prospective and multicentre international studies to further validate our findings, and assess the utility of the UDS on different clinical and research platforms.
Samartzis concludes, “This new imaging technology and the assessment of the UDS may supplement conventional MRI, therefore providing a larger snapshot into a patient’s spine degeneration and pain profiles…allowing clinicians to develop more personalised and precise management options to improve patient outcomes. This certainly represents a new leap forward in the visualisation of the spinal discs and perhaps pain.”