A comprehensive evaluation of somatosensory function in acute low back pain and pain-free individuals using quantitative sensory testing

Low back pain is a common complaint and has the highest global disability burden when measured as years lived with a disability. After an episode of low back pain, up to two-thirds of people will experience variable levels of chronic pain after one year and around 10% will be significantly disabled in association with low back pain. Recent research has revealed that people with chronic low back pain are characterised by widespread pain hypersensitivity, suggesting that neuroplastic changes at the central nervous system underlie this condition. While this knowledge has enhanced our understanding of pathophysiological processes in chronic low back pain, it is currently unclear how early these somatosensory changes develop. Therefore, the broad aims of this thesis are: to investigate the time course of somatosensory changes from the acute stage of low back pain without serious pathology; to examine the prognostic utility of this information in low back pain; and to address methodological aspects of such assessment using quantitative sensory testing (QST). In order to meet these aims, several research approaches have been undertaken. Two systematic reviews of the literature were carried out to establish whether somatosensory changes are a feature of acute low back pain compared to healthy controls (Chapter 2) and to investigate the prognostic ability of QST in low back pain (Chapter 5). An inception cohort study, using a comprehensive QST assessment, was carried out to inform whether early somatosensory changes can be detected soon after low back pain onset compared to pain-free individuals (Chapter 3). The assessment included evaluation of endogenous pain modulation (Chapter 4) and tracked changes in somatosensory function over time, until 4 months after onset (Chapter 7). This comprehensive data set has also enabled the evaluation of important methodological issues related to the stability of QST over time in healthy individuals (Chapter 6). Overall, the work presented in this thesis has contributed to the body of evidence regarding the evaluation of somatosensory function in the early stages of low back pain, as well as providing novel methodological insights into QST testing. This scholarly work has specific implications for clinicians and researchers addressing low back pain, the condition of highest disability burden worldwide.