Validation of a portable marker-based motion analysis system

Abstract

Background The Opti_Knee system, a marker-based motion capture system, tracks and analyzes the 6 degrees of freedom (6DOF) motion of the knee joint. However, the validation of the accuracy of this gait system had not been previously reported. The objective of this study was to validate and the system. Two healthy subjects were recruited for the study. Methods The 6DOF kinematics of the knee during flexion–extension and level walking cycles of the knee were recorded by Opti_Knee and compared to those from a biplanar fluoroscopy system. The root mean square error (RMSE) of knee kinematics in flexion–extension cycles were compared between the two systems to validate the accuracy at which they detect basic knee motions. The RMSE of kinematics at key events of gait cycles (level walking) were compared to validate the accuracy at which the systems detect functional knee motion. Pearson correlation tests were conducted to assess similarities in knee kinematic trends between the two systems. Results In flexion–extension cycles, the average translational accuracy (RMSE) was between 2.7 and 3.7 mm and the average rotational accuracy was between 1.7 and 3.8°. The Pearson correlation of coefficients for flexion–extension cycles was between 0.858 and 0.994 for translation and 0.995-0.999 for angles. In gait cycles, the RMSEs of angular knee kinematics were 2.3° for adduction/abduction, 3.2° for internal/external rotation, and 1.4° for flexion/extension. The RMSEs of translational kinematics were 4.2 mm for anterior/posterior translation, 3.3 mm for distal/proximal translation, and 3.2 mm for medial/lateral translation. The Pearson correlation of coefficients values was between 0.964 and 0.999 for angular kinematics and 0.883 and 0.938 for translational kinematics. Conclusion The Opti_Knee gait system exhibited acceptable accuracy and strong correlation strength compared to biplanar fluoroscopy. The Opti _Knee may serve as a promising portable clinical system for dynamic functional assessments of the knee.

Kinematic study of the overall unloading brace for the knee

“…All braces were placed on the right knee by the same professional orthopedist. We collected 3D kinematic data using a standard validated test procedure [ 14 ] under four conditions: walking without the OUB; walking with the OUB; jogging without the OUB; and jogging with the OUB. Data were collected while the subjects were walking at a speed of 3 km/h and jogging at a speed of 5 km/h on a treadmill [ 18 , 19 ].…”

“…All kinematic data were acquired with an Opti_Knee system (Innomotion, Shanghai, China, Fig. 2 ), which is a 3D portable optical motion capture system and has repeatability in translation and rotation of 1.3 mm and 0.9°, respectively [ 13 , 14 , 16 ]. Two high-speed infra-red cameras (Polaris Spectra, Northern Digital Inc., Waterloo, ON, Canada) were integrated into a housing compartment to fix their relative 3D spatial positions.…”

“…The dynamic motions of limb joints are complex. The human knee has functional movement and proprioception across six DOFs (6DOF) in three-dimensional (3D) space [ 14 – 16 ]. Quantified joint-kinematic data have enabled motion characteristics to be compared across conditions, such as before and after treatment [ 17 ].…”

The Chinese knotting technique assist anatomical anterior cruciate ligament reconstruction for aggressive rehabilitation

“…[1][2][3] The knee kinematics in 2 groups were compared at 3, 6, 12, and 24 months after surgery using Opti_Knee, a knee joint 3-dimensional motion analysis system (on Haiyidong Medical Technology Co., Ltd), recording the maximum step length, minimum step length, period of the limb walking, knee joint 6 degrees of freedom (flexion and extension angle, varus angle, internal and external rotation angle, front and back displacement, up and down displacement and internal and external displacement), and range of motion (maximum the difference from the minimum value). [20][21][22][23][24][25] The second look examination under arthroscopy was performed 12 months after surgery.…”

“…In this study, CKT technique was used during ACL reconstruction, and active rehabilitation plan was adopted after surgery. International Knee Documentation Committee (IKDC) and Lysholm function scores of patients were followed up 2 years after surgery, and Opti_Knee [20][21][22][23][24][25] (Innomotion, Shanghai, China) was used for kinematic analysis. This study assumed that the CKT group could obtain better functional scores and kinematic analysis results.…”