Optoelectronic movement analysis to measure motor performance in patients with chronic low back pain: test of reliability.

OBJECTIVE To assess test-retest reliability of the Posturo-Locomotion-Manual(PLM) test in patients with chronic low back pain. DESIGN A controlled study in which the PLM test was used repeatedly on patients with chronic low back pain and persons without back pain. SUBJECTS Twelve patients with treatment-resistant chronic low back pain, selected by 2 orthopaedic spine surgeons and 12 age- and sex-matched individuals with no back pain history. METHODS An optoelectronic camera and a computer were used to quantify the performance during a simple test in which subjects picked up an object from the floor and transported it up to a shelf, thereby forcing the body through postural, locomotor and manual movements. The outcome measures were: movement time, simultaneity index and phase times for postural, locomotion and arm movement phases. Statistical analyses regarding intra-individual agreement between the measurements (reliability analysis) and changes over time were carried out. RESULTS The effect of test movement habituation was minimized when the lowest mean value of any of 3 consecutive measures (tri-average) was used. In the control group, variation between test occasions was small. In the group of patients with chronic low back pain there was a random measurement error before intervention (sensory motor learning). After intervention the PLM test had the same precision in both groups. CONCLUSION When the tri-average measure is used, the influence of test movement habituation is minimized and the optoelectronic PLM test is found to be reliable and responsive. It proved to be a useful tool to quantify dynamic performance in freely moving patients with chronic low back pain.