The effect of pain relief on dynamic changes in lumbar curvature

Lumbar curvature is important in the assessment of low back pain (LBP). It is often reported that changes in curvature seen in LBP sufferers are an adaptive response to pain. Studies investigating this hypothesis employing an experimental pain relief model have failed to isolate pain relief in their interventions. Therefore the purpose of this study was to investigate the immediate effects of pain relief on dynamic lumbar curvature. Twenty acute and 20 chronic LBP sufferers had their dynamic curvature measured using a novel fibre-optic device during flexion, extension and lifting before and after administration of oral analgesics. Peak curvature changes were examined using paired t-tests, numbers of responders to pain relief and changes in lumbar curvature sequencing were compared between groups using Chi-squared testing. A significant reduction in movement evoked pain was achieved. A significant reduction in kyphosis at end range flexion and lifting was identified for the acute LBP group following pain relief. No significant differences were observed for the chronic low back pain (CLBP) group. Neither the acute nor chronic LBP group were more likely to respond to pain relief by demonstrating alterations in peak curvature or in lumbar sequencing behaviour. These results demonstrate simple targeted pain relief did not result in gains in peak curvature challenging the assumption of movement alteration being possible through pain relief. Dynamic changes in curvature as displayed by sequencing showed that neither acute nor chronic LBP sufferers were more likely to respond to pain relief.