Is there a relationship between pain intensity and postural sway in patients with non-specific low back pain?

Abstract

Background: Increased center of pressure excursions are well documented in patients suffering from non-specific low back pain, whereby the altered postural sway includes both higher mean sway velocities and larger sway area. No investigation has been conducted to evaluate a relationship between pain intensity and postural sway in adults (aged 50 or less) with non-specific low back pain.

Methods: Seventy-seven patients with non-specific low back pain and a matching number of healthy controls were enrolled. Center of pressure parameters were measured by three static bipedal standing tasks of 90 sec duration with eyes closed in narrow stance on a firm surface. The perceived pain intensity was assessed by a numeric rating scale (NRS-11), an equal number of patients (n = 11) was enrolled per pain score.

Results: Generally, our results confirmed increased postural instability in pain sufferers compared to healthy controls. In addition, regression analysis revealed a significant and linear increase in postural sway with higher pain ratings for all included COP parameters. Statistically significant changes in mean sway velocity in antero-posterior and medio-lateral direction and sway area were reached with an incremental change in NRS scores of two to three points.

Conclusions: COP mean velocity and sway area are closely related to self-reported pain scores. This relationship may be of clinical use as an objective monitoring tool for patients under treatment or rehabilitation.

Figure 1

Relationship between pain intensity and mean sway velocity in AP and ML. The horizontal line and the grey area indicate the mean score of healthy controls and the standard deviations respectively. The vertical lines indicate standard deviations; the boxes show mean and 95% CIs respectively. Levels of significance compared to controls: * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001.

Figure 2

Relationship between pain intensity and 90% circle diameter. The horizontal line and the grey area indicate the mean score of healthy controls and the standard deviations respectively. The vertical lines indicate standard deviations; the boxes show mean and 95% CIs respectively. Levels of significance compared to controls: * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001.