Validation of a Markerless Non-Contact Gait Analysis System for Three-Dimensional Gait Kinematics in Patients with Ankle Injuries: A Concurrent Comparison Study with the Vicon Three-Dimensional Motion Capture System.

(1)

Background

This study validated the accuracy of a markerless gait analysis system, Foot4D, against the Vicon 3D motion capture system in 60 patients with ankle injuries. (2)

Methods

Synchronized gait data were collected using both systems while participants walked on a treadmill at self-selected speeds. The Foot4D system employs a Vision Transformer (ViT-H/16) encoder and the SKEL parametric model for markerless 3D pose reconstruction from multi-view depth cameras. Spatiotemporal gait parameters and lower limb 3D kinematics (hip, knee, and ankle) were compared using ICC, Bland-Altman analysis, and MAE. (3)

Results

All 12 spatiotemporal parameters showed good-to-excellent agreement (ICC = 0.738-0.999, MAE = 0.009-0.108 m/s). Agreement for joint kinematics decreased from proximal to distal: hip (mean ICC ≈ 0.947, MAE 1.16-1.52°), knee (mean ICC ≈ 0.921, MAE 1.17-1.75°), and ankle (mean ICC ≈ 0.839). Ankle sagittal plane ROM demonstrated good agreement (ICC = 0.857-0.911), while the frontal (ICC ≈ 0.807) and transverse (ICC ≈ 0.816-0.835) planes were at the lower bound of good agreement, with a -3.19° systematic bias in the injured ankle sagittal plane. (4)

Conclusions

Foot4D is clinically reliable for spatiotemporal and proximal joint kinematic assessment, though ankle multiplanar motion measurement warrants further algorithmic optimization.