Validation of foot pitch angle estimation using inertial measurement unit against marker-based optical 3D motion capture system

Gait analysis is relevant to a broad range of clinical applications in areas of orthopedics, neurosurgery, rehabilitation and the sports medicine. There are various methods available for capturing and analyzing the gait cycle. Most of gait analysis methods are computationally expensive and difficult to implement outside the laboratory environment. Inertial measurement units, IMUs are considered a promising alternative for the future of gait analysis. This study reports the results of a systematic validation procedure to validate the foot pitch angle measurement captured by an IMU against Vicon Optical Motion Capture System, considered the standard method of gait analysis. It represents the first phase of a research project which aims to objectively evaluate the ankle function and gait patterns of patients with dorsiflexion weakness (commonly called a “drop foot”) due to a L5 lumbar radiculopathy pre- and post-lumbar decompression surgery. The foot pitch angle of 381 gait cycles from 19 subjects walking trails on a flat surface have been recorded throughout the course of this study. Comparison of results indicates a mean correlation of 99.542% with a standard deviation of 0.834%. The maximum root mean square error of the foot pitch angle measured by the IMU compared with the Vicon Optical Motion Capture System was 3.738° and the maximum error in the same walking trail between two measurements was 9.927°. These results indicate the level of correlation between the two systems.

The Talus-1st Metatarsal Angle, the Talo-Horizontal Angle and Calcaneal Pitch Angle of Young Men in Korea / 대한족부족관절학회지

PURPOSE: The purpose of this study is to find out the normal angles of the talus-1st metatarsal angle, the talo-horizontal angle and calcaneal pitch angle for diagnosis of foot deformity in Korea. This would be helpful as it would provide a basic angular measurement of flat and cavus foot that indicates the need for operation. MATERIALS AND METHODS: Within a period of four months from January 2007 to April 2007, We have established 600 feet of 300 males without trauma history of foot. The source to image distance is 40 inches and erect weight bearing radiographs are obtained in anteroposterior and lateral projections. The significant angular measurements that define flat or cavus foot are the talus-1st metatarsal angle, the talo-horizontal angle and calcaneal pitch angle. RESULTS: The mean age was 21 years (19-22 years) old. The mean talus-1st metatarsal angle was 0+/-6.9degrees, the mean talo-horizontal angle was 25.8+/-4.5degrees and the mean calcaneal pitch angle was 23.9+/-5.1degrees. CONCLUSION: We can consider that mean talus-1st metatarsal angle, talo-horizontal angle and calcaneal pitch angle are 0+/-6.9degrees, 25.8+/-4.5degrees and 23.9+/-5.1degrees as an normal angle limit of young age in Korea.