De rol van proprioceptieve posturale controle in het ontwikkelen en in stand houden van lage rugpijn: een cross-sectioneel en prospectief onderzoek

Low back pain (LBP) and the reoccurrence of LBP is a major health problem in Western society with high social and economic consequences. Clinicians in daily practice are convinced that the group of patients with LBP is becoming still younger and the incidence of LBP in the late adolescence approximates the incidence of the adult population. Moreover, LBP at adolescent age is mostly idiopathic and may higher the risk for future episodes of LBP. Idiopathic LBP or non-specific low back pain (LBP) is defined as pain in the lumbar and/or gluteal region without structural anatomical abnormalities as there are disc abnormalities, inflammation, fracture, tumor, etc. Pain may be caused or persist despite the absence of a nociceptive stimulus due to damage or injury. Altered proprioceptive postural control (postural changes, decreased postural robustness and changed proprioceptive afferent inputs) is frequently demonstrated as a contributing factor in LBP and may confirm that a real anatomical nociceptive stimulus is not always present in people with LBP. A better understanding of the biological component of LBP in relation, and in addition to psychosocial factors, is important for a more rational approach to the management of LBP. Research into biological underlying causes and mechanisms may be of priority interest for the research in LBP for the next years. In addition to cross-sectional research, prospective studies are necessary to have more insight in the underlying causing mechanisms of LBP.The general objective of this doctoral project is to generate a better insight in the proprioceptive postural control in young people with LBP versus healthy controls. Besides cross-sectional analysis also a prospective investigation was carried out to clarify a cause-effect relation. Four studies were performed to clarify this research question. The variability in proprioceptive postural control strategies was investigated in Chapter 2 (Study 1). Results showed a decreased variability in proprioceptive postural control strategies in young persons with LBP. Subjects with LBP showed a decreased capacity to switch to a more multisegmental strategy when this was more appropriate according to the postural condition (i.e., standing on an unstable support, sitting). Also a decreased postural robustness was shown in the more complex postural conditions. A reduced use of lumbar proprioceptive afference was associated with the decreased variability. In Chapter 3 (Study 2), it was investigated if proprioceptive impairments demonstrated during static postural tasks in people with LBP are associated with an altered performance of a more dynamic task. As a dynamic task, the STSTS task was chosen. People with LBP and a concomitant decreased use of lumbar proprioceptive afference for standing postural control needed more time to perform five repetitions of the STSTS. The time differences were observed during the sit and stance phases (transition phases) and not during the focal movement phases. A decreased pelvic preparatory movement (slower onset of pelvic anterior rotation) was observed during the sit phases. In Chapter 4 (Study 3), postural inter-correlations during usual standing and sitting in young healthy people were analyzed. In usual sitting, the pelvis was demonstrated to have most correlations with other spinal angles. In contrast, in usual standing the trunk angle showed most correlations with other spinal postural angles. However, correlations were mostly small to moderate, suggesting a between-subject variability in sagittal spinal posture without the existence of an optimal spinal posture. Chapter five (Study 4) describes a prospective study that examined altered proprioceptive postural control, altered postural spinal angles and psychological variables as possible risk factors for future mild LBP within two years. Only an ankle-steered postural control strategy during stable standing was observed to be a risk factor for developing LBP in the near future. Other proprioceptive, postural, psychological or physical activity variables could not be identified as risk factors. It may be concluded that evaluating the proprioceptive postural control may help clinicians to identify people who are at risk for developing LBP. This doctoral thesis brought more insight into the role of the proprioceptive system as underlying mechanism in LBP. A decreased capacity to upweight proprioceptive signals from the back muscles compared to the ankle muscles was demonstrated to be associated with LBP and to develop future LBP. Moreover, this impaired proprioceptive control also delayed the preparatory pelvic movement during the STSTS resulting in a slower performance of this movement. These findings illustrate the importance of evaluating proprioception during postural control tasks rather than only focusing on the motor output when evaluating persons with LBP. Future research must clarify if the altered proprioceptive input is based on a decreased sensitivity of the muscle spindles and/or based on central changes.status: publishe