Biomechanical evaluation of an optical system for quantitative human motion analysis.

摘要

An eight-camera Optitrack motion capture system was evaluated by performing static, linear dynamic, and angular dynamic calibrations using marker distances associated with upper and lower extremity gait and wheelchair models. Data were analyzed to determine accuracy and resolution within a defined capture volume using a standard Cartesian reference system. Two additional cameras along with AMASS and Visual3D (C-Motion, Inc., Germantown, MD) biomechanical modeling software were used to determine joint kinematics at the pelvis, hip, knee, and ankle of ten control subjects (mean age 21.5 ± 1.65 years). The same data were processed through Nexus (Vicon Motion Systems, Oxford, England) modeling software. The joint angle data was statistically compared between the two systems using a variance components model which determined the variability between maximum, minimum, and range values.;Static accuracy ranged from 99.31% to 99.90%. Static resolution ranged from 0.04 ± 0.15 mm to 0.63 ± 0.15 mm at the 0.05 level of significance. The dynamic accuracy ranged from 94.82% to 99.77 %, and dynamic resolution ranged from 0.09 ± 0.26 mm to 0.61 ± 0.31 mm at the 0.05 level of significance. These values are comparable to those reported for a standard Vicon 524 (Vicon Motion Systems, Oxford, England) motion analysis system. Gait cycle maximum, minimum, and range values showed no significant difference when comparing Visual3D and Nexus at the pelvis, hip, and knee. Significant differences were seen at the tibia (rotation) and foot due to foot model variations between the two systems. The results support application of the lower cost Optitrack cameras and Visual3D software for 3D kinematic assessment of lower extremity motion during gait. Additional potential applications supported by these findings include other lower extremity models, assisted ambulation, and wheelchair mobility.