The influence of non-specific low back pain on pressure pain thresholds and disability.

The purpose of this study was to investigate the pressure pain thresholds (PPTs) with respect to the Erector spinae and the hip muscles in 87 patients with subacute non-specific low back pain (LBP) and to evaluate the relationship between the PPTs and disability. In order to establish reference values, 64 healthy subjects were examined with respect to PPTs and used as a control group against the group of LBP patients. The mean PPT values of the Erector spinae and the hip at all examined points of the LBP group were significantly lower (p<0.001) in comparison to the PPT values of the healthy group. An exceptionally high difference (2.7 kg/cm2) was found at the L3 Erector spinae level. The correlation between having LBP or not in the whole group (n=151) and PPT, was highest at the L3 level of the Erector spinae (r=-0.710, p<0.001). When the group of patients with LBP was divided into two subgroups in terms of having an Oswestry disability index (ODI) lower than 40 ("moderate LBP disability") or an ODI higher than 40 ("severe LBP disability") it was surprising to notice that there was no significant difference between the PPTs of the Erector spinae and the hip musculature. This study has shown the possibility of the existence of muscular disorder in the lumbar part of the Erector spinae in patients with non-specific low back pain, but also reveals the strong inter-individual differences in muscular fibrosis sensitivity and pain behaviour related to gender.