Disability measurement in persons with back pain: a validity study of spinal range of motion and velocity.

Objective: To evaluate the criterion validity and responsiveness to change of spine kinematic variables to assess disability in patients with low back pain.
Design: Blinded comparison between spine kinematic variables, Oswestry disability questionnaire scores, and work status.
Setting: Multidisciplinary occupational rehabilitation clinic of a university hospital.
Patients: Population-based cohort of 111 patients with subacute work-related back pain who were absent from regular work for more than 4 weeks because of back pain.
Interventions: This study was part of a population-based randomized clinical trial. Patients were randomized to 4 different methods of management: usual care, rehabilitation, ergonomics, or rehabilitation and ergonomics.
Main Outcome Measures: Oswestry disability questionnaire, kinematic analysis of the spine during flexion and extension of the trunk, and work status were collected at weeks 4, 12, 24, and 52 after the back accident.
Results: Kinematic variables were poorly to moderately related to work status and Oswestry questionnaire scores. Kinematic variables were also unresponsive to change in work status and Oswestry questionnaire scores over time.
Conclusion: Spine kinematics during flexion and extension of the trunk do not appear to be a valid measure of disability in patients with subacute and chronic back pain.