Reliability and validity of a kinematic spine model during active trunk movement in healthy subjects and patients with chronic non-specific low back pain.

OBJECTIVE To develop a standardized, reliable, valid spine model of active trunk movements that accurately discriminates kinematic patterns of patients with chronic non-specific low back pain from those of healthy subjects. DESIGN Comparative cohort study. SUBJECTS Healthy subjects (n = 25) and patients with chronic non-specific low back pain (n = 25) aged 30-65 years. METHODS Subjects performed 7 trunk movements from a seated position at non-imposed speed during 2 sessions. Nine markers on bony landmarks measured range of motion and speed of 5 spinal segments, recorded by 8 optoelectronic cameras. RESULTS Both groups showed good-excellent reliability in all movements for range of motion and speed of all spinal segments (intraclass correlation (ICC), 0.70-0.96; standard error of measurement, expressed as a percentage, 19.4-3.3%). The minimal detectable change in the patient group was 16.7-53.7%. Range of motion and speed in all spinal segments for trunk flexion, rotation, and flexion with rotation differed significantly between groups (p < 0.001), with large/very large effect sizes (Cohen's d = 1.2-2). Binary logistic regression yielded sensitivities/specificities of 92%/84% for range of motion and 92%/80% for speed. CONCLUSION Kinematic variables are valid, reliable measures and can be used clinically to diagnose chronic non-specific low back pain, manage treatment, and as quantitative outcome measures for clinical trial interventions.