Motor control in non-specific chronic low back pain: A view to classification

Non-specific chronic low back pain (NSCLBP) is a complex bio-psycho-social pain disorder of frequently unknown aetiology. Impairments in motor control (MC) have been frequently associated with NSCLBP disorder. Although the causal relationship between LBP and motor control impairment (MCI) is a matter of debate, impaired MC has been proposed to increase loading of the spinal tissues, which over time may contribute to an ongoing pain, chronicity and subsequent disability. Therapeutic MC interventions have been shown to modify MC but larger clinical trials were unsuccessful in consistently improving clinical outcomes in patients with CLBP. This lack of success has been linked to the heterogeneity in patients with NSCLBP in whom the impaired MC and hence the most optimal therapeutic MC intervention may considerably vary. Bio-psycho-social classification systems (CS), which categorize NSCLBP patients based on the type of MCI, have been developed but its effectiveness in (i) revealing specific MC alterations in patients with different type of MCI, and (ii) guiding therapeutic MC interventions that are specific to the type of MCI have not been fully explored. Preliminary Study: The aim of this part was to establish the reliability of a novel measuring device, the Spinal Wheel, to measure the sagittal curvatures of the whole spine (thoracic and lumbar) in sitting and standing in MCI subgroups of patients with NSCLBP rather than small sections of the spine as other studies have. Typical measurement error was also studied. Excellent within-day, intra- and inter-tester reliability and substantial between-day, test-retest reliability was demonstrated thus warranting its use in the main study of this thesis. Main Study - Part 1 The aim of this part was to detect differences in sensory and motor parameters of MC, specifically proprioception (spinal position sense) and trunk muscle electromyography (EMG) amplitudes in asymptomatic subjects and two of the most frequently encountered patterns of MCI in NSCLBP, flexion pattern (FP-MCI) and active extension pattern (AEP-MCI) when performing neutral spine posture tasks in sitting and standing. Patients with FP- and AEP-MCI demonstrated unique impairments in some, but not all, of the measured parameters of MC. Main Study - Part 2 The aim of this part was to determine the effect of CS-guided postural motor learning intervention (CS-MLI) compared to generalized postural intervention (GPI) on clinical outcomes (patient-reported pain and disability) and MC outcomes (spinal position sense and trunk muscle EMG amplitudes) in NSCLBP patients with FP- and AEP-MCI using a pragmatic randomized, single-blinded, test-retest investigation. CS-MLI improved perceived disability and pain scores and produced immediate but short-lasting improvements in some elements of sensory function compared to minimal change in GPI. The pragmatic nature of the investigation, however, may not conclusively support that the specificity of CS-MLI to the MCI type was the deciding factor in the improved outcomes. This doctoral thesis on classification of NSCLBP highlighted the importance of classification in clinical research into NSCLBP and advanced its applicability within clinical practice. Classifying NSCLBP patients based on their MC characteristics was shown to be valuable in revealing the existence of unique alterations in some MC parameters in subgroups of patients with specific types of MCI, that appear to be lost when NSCLBP patients are treated as homogeneous. The thesis also advanced the knowledge base on the use of classification-guided therapeutic interventions in this population of patients