A new logistic regression model for the detection of chronic low back pain, based on a case-control study in the Spanish population.

Study design: Case-control study comparing healthy individuals and patients with chronic non-specific low back pain (NSLBP).

Purpose: To compare detailed spinal motion and muscle activity patterns-recorded simultaneously using non-invasive methods-between chronic NSLBP patients and pain-free individuals, and to identify the most clinically useful variables for discriminating between the two groups.

Overview of literature: Motion analysis and electromyography (EMG) have been widely used to differentiate NSLBP patients from pain-free individuals. However, due to methodological heterogeneity across studies, the results have been inconsistent, limiting the clinical applicability of the findings.

Methods: Forty-three pain-free controls and 43 patients with chronic NSLBP were enrolled. Using non-invasive techniques, synchronized lumbar spine motion and erector spinae (ES) EMG activity were recorded during standardized trunk flexion-extension cycles.

Results: Several variables differed significantly between the two groups. Logistic regression identified two variables with significant odds ratios for the presence of chronic NSLBP: time spent with the spine flexed beyond 90% of its maximum range (odds ratio, 0.92; 95% confidence interval, 0.86-0.99) and the ES relaxation ratio (odds ratio, 1.08; 95% confidence interval, 1.04-1.13).

Conclusions: Individuals with and without chronic NSLBP exhibit distinct spinal motion and ES activity patterns during trunk flexionextension. These differences-specifically the time of maximum lumbar flexion and the relaxation ratio-can be objectively and easily measured. Their assessment may offer valuable clinical utility for the diagnosis and follow-up of NSLBP patients.