Diffuse central sensitization in low back patients: A secondary analysis of cross-sectional data including tender point examination and magnetic resonance imaging of the lumbar spine

Abstract

Consistency between back pain intensity and degenerative changes on magnetic resonance imaging (MRI) of the lumbar spine is poor. This study aimed to show whether tender point (TP) examination, used as a test for diffuse central sensitization, may add valuable information to clinical assessment of patients with low back pain (LBP).This was a cross-sectional study including 141 patients with LBP on sick leave. Baseline measures comprised back pain, leg pain intensity, and LBP examination including TP examination. Degenerative MRI findings were assessed in a standardized manner and blinded for clinical data. The number of TPs was analyzed in relation to sex, widespread pain, radiculopathy, pain duration, and degenerative changes on MRI.The number of TPs was positively associated with the female sex, widespread pain, and pain duration. It was negatively associated with degenerative manifestations and radiculopathy, the latter displaying a low level similar to that of the general population. A positive association between back pain intensity and TPs was present in patients with and without radiculopathy and in patients with substantial degenerative changes. Men with >7-8 TPs and women with >10-11 TPs had more back pain and similar or fewer degenerative changes than patients with few TPs (<3 and <6 TPs, respectively), thereby identifying 34% to 44% of patients with nonspecific LBP and 5% to 8% of patients with radiculopathy, respectively, with disproportionate back pain in relation to degenerative changes.Supplemental TP examination improved clinical and MRI evaluation of patients with LBP. By using gender-specific cut points, patients with disproportionate back pain were identified, presumably indicating diffuse central sensitization.

Figure 1

Box plots showing tender point distribution in different subgroups of the present study group of 141 patients. The boxes include 25% to 75% of the distributions, and the whiskers define 1% and 99% limits. Outliers presented by dots. Only 4 women and 1 man both had radiculopathy and widespread pain. 1. +widespread pain^∗, −radiculopathy. 2. +widespread pain^∗, +radiculopathy. 1. −widespread pain^∗, −radiculopathy. 1. −widespread pain^∗, +radiculopathy. ^∗the preceding two weeks.

Figure 2

Associations between tender points and back pain intensity in patients with and without radiculopathy (left), and in patients with and without substantial degenerative changes (right). Fitted values and 95% confidence intervals of standard error of the means. The confidence intervals were wide in the upper spectrum of TPs in patients with radiculopathy and substantial degenerative changes due to few of these patients with many TPs.