Reliability and measurement error of frontal and horizontal 3D spinal motion parameters in 219 patients with chronic low back pain

Background: In order for measurements to be clinically useful, data on psychometric conditions such as reliability should be available in the population for which the measurements are intended to be used. This study comprises a test-retest design separated by 7 to 14 days, and evaluates the intra and interrater reliability of regional frontal and horizontal spinal motion in 219 chronic LBP patients using the CA6000 Spine Motion Analyzer. In addition, it compares these results on the frontal and horizontal plane with previously published results on the sagittal plane. 219 individuals with chronic mechanical LBP, classified as either Quebec Task Force group 1, 2, 3 or 4 were included, and kinematics of the lumbar spine were sampled during standardized spinal lateral flexion and rotation motion using a 6-df instrumented spatial linkage system. Test-retest reliability and measurement error were evaluated using intraclass correlation coefficients ICC_(1,1) and Bland-Altman limits of agreement (LOAs). Results: The reliability analysis based on the whole study sample showed ICC_(1,1) coefficients varying between 0.68 and 0.73 for the frontal plane and 0.33 and 0.49 for the horizontal plane. Relatively wide LOAs were observed for all parameters. Reliability measures in patient subgroups ICC_(1,1) ranged between 0.55 and 0.81 for the frontal plane and 0.28 and 0.69 for the horizontal plane. Greater ICC_(1,1) coefficients and smaller LOA were observed when patients were examined by the same examiner, had a stable pain level between tests, and were male. ROM measurements were more reliable in patients with a BMI higher than 30, and measurements on patients with LBP and leg pain showed higher reliability and smaller measurement error in all parameters except for the jerk index. Conclusion: Frontal plane measurements obtained using the CA6000 Spine Motion Analyzer are sufficiently reliable to be used for group comparisons but not individual comparisons. Measurements in the horizontal plane can be used for neither group nor individual comparisons.