The use of muscle morphology and local dynamic stability in clinical assessment of treatment for non-specific chronic low back pain

This thesis investigated the use of a series of tests to examine local dynamic stability (LDS) of the trunk, morphology of lumbar multifidus muscle (LMM) and levels of pain and disability in non-specific chronic low back pain (NSCLBP) patients within a clinical setting. Study one determined the reliability of a test for LDS of the trunk using maximum Lyapunov exponents (max), calculated from 3-dimensional acceleration time series collected during a 3-minute kneeling cyclical tap-test. The test was found to be reliable (ICC=0.760) in healthy adults, thus providing evidence that the use of this testing protocol was valid for use in future studies with repeated measures design. Study two established the reliability of using ultrasound imaging (USI) to measure LMM thickness on separate occasions. USI was shown to have excellent reliability (ICC=0.988) in measuring LMM thickness, thereby providing validity for use in future studies. Study three examined the outcomes of a series of tests used in a cohort of NSCLBP patients and age matched healthy controls; aimed at assessing LDS of the trunk using a three minute cyclical tap test during single and dual task (motor + cognitive) conditions, LMM thickness, and levels of pain and disability. Differences between groups and relationships between measures were observed at baseline and at 3 months follow-up. Significant differences were found between healthy and NSCLBP groups when comparing LDS during single and dual task conditions. NSCLBP participants prioritised the motor task at greater expense of the cognitive task, whereas healthy participants showed no deficit in either task. No significant associations were found between LDS measures and pain or LMM thickness, although after 3 months and a significant reduction in pain, the NSCLBP group showed behaviour that was analogous to that of the healthy group during dual task conditions. The results of this study show that the series of tests were able to identify differences between healthy and NSCLBP populations and may provide a useful clinical tool in studies evaluating treatment efficacy and effectiveness. Study four, a case study, explored the feasibility of using the series of tests in a patient receiving spinal cord and medial nerve stimulation – an intervention directly aimed at reducing pain, rehabilitating LMM and restoring dynamic stability. The study demonstrated the practicability of using the protocol with patients and informed recommendations for a future, larger scale study. The use of an innovative tap-test to measure LDS of the trunk during single and dual task conditions, in conjunction with LMM morphology, for clinical application in the assessment of NSCLBP patients are the novel aspects of this thesis and contribute new data and interpretations to this area of research.