Intrasubject reliability of spinal range of motion and velocity determined by video motion analysis.

BACKGROUND AND PURPOSE The purpose of this study was to investigate the repeatability of spinal range of motion (ROM) and movement velocity measurements of patients with chronic low back pain, using a two-dimensional motion analysis system. This apparatus uses reflective markers placed on anatomical landmarks and video digitization to derive ROM measurements from three segments of the spine and associated velocities through the respective ROMs. SUBJECTS Forty-two patients with chronic LBP underwent ROM and movement velocity testing. METHODS Each subject was tested twice without removal of the markers to minimize error contribution from differences in marker placement. RESULTS Results indicated that both the ROM measures and the velocity measures were highly repeatable. Intraclass correlations for the ROM measures ranged from .77 to .96. Velocity measures were also reliable, with intraclass correlation coefficients ranging from .75 to .97. CONCLUSION AND DISCUSSION Overall, the results seem to indicate that the video motion analysis system used in this study yields repeatable ROM and velocity measures on a clinical population. In practice, however, the measures may reflect greater errors due to the need of examiners to relocate markers at different testing sessions. These systems also offer distinct advantages over other means of obtaining ROM and velocity measures. The results of this study indicate that these measures may be obtained without undue concern for measurement artifact due to the instrumentation reliability.