Real-Time Detection of Seven Phases of Gait in Children with Cerebral Palsy Using Two Gyroscopes

Abstract

A recently designed gait phase detection (GPD) system, with the ability to detect all seven phases of gait in healthy adults, was modified for GPD in children with cerebral palsy (CP). A shank-attached gyroscope sent angular velocity to a rule-based algorithm in LabVIEW to identify the distinct characteristics of the signal. Seven typically developing children (TD) and five children with CP were asked to walk on treadmill at their self-selected speed while using this system. Using only shank angular velocity, all seven phases of gait (Loading Response, Mid-Stance, Terminal Stance, Pre-Swing, Initial Swing, Mid-Swing and Terminal Swing) were reliably detected in real time. System performance was validated against two established GPD methods: (1) force-sensing resistors (GPD-FSR) (for typically developing children) and (2) motion capture (GPD-MoCap) (for both typically developing children and children with CP). The system detected over 99% of the phases identified by GPD-FSR and GPD-MoCap. Absolute values of average gait phase onset detection deviations relative to GPD-MoCap were less than 100 ms for both TD children and children with CP. The newly designed system, with minimized sensor setup and low processing burden, is cosmetic and economical, making it a viable solution for real-time stand-alone and portable applications such as triggering functional electrical stimulation (FES) in rehabilitation systems. This paper verifies the applicability of the GPD system to identify specific gait events for triggering FES to enhance gait in children with CP.

Keywords: cerebral palsy (CP); functional electrical stimulation (FES); gait analysis; gait event; gait pathology; gait phase detection (GPD); motion capture.

Figure 1

The gait phase detection (GPD) and functional electrical stimulation (FES) system. Shank attached gyroscopes sent data to a rule-based algorithm written in LabVIEW (version 2014, National Instruments, Austin, TX, USA) and all seven phases of gait were detected. A motion capture system was used to evaluate the system.

Figure 2

(a) Shank angular velocity about the medio-lateral axis (${\omega }_{ml}$) for typically developing children and healthy adults during treadmill walking. Gait phase onset is based on the indicated peaks and zero-crossings. Four gait phase events are detected using ipsilateral shank angular velocity (loading response (LR), initial swing (ISw), mid-swing (MSw) and terminal swing (TSw). The three remaining gait phase events are detected using contralateral shank angular velocity (mid-stance (MSt), terminal stance (TSt) and pre-swing (PSw)). The onset of LR corresponds to initial contact (IC)/heel strike (HS) and the onset of ISw corresponds to toe-off/end-contact (TO/EC); (b) Representative shank angular velocity about the medio-lateral axis for a typically developing child (top) and a child with cerebral palsy (CP) (bottom). A distinct peak is visible at the onset of ISw (TO/EC) in TD while the peak is less distinct in CP. The sum of all three components of shank angular velocity (${\omega }_{sum}$) shows a more distinct peak at ISw onset, and was initially used for ISw detection in children with CP (bottom).

Figure 3

Mean error (± Std) of heel strike (HS), heel-off (HO) and toe-off (TO) for gait phase detection of typically developing children (GPD-TD) relative to gait phase detection via force sensing resistors (GPD-FSR). HS corresponds to loading response, HO corresponds to terminal stance and TO corresponds to initial swing.

Figure 4

Gait phase detection (GPD) onset deviations (mean ± SE) relative to motion capture (GPD-MoCap). Deviations are shown for both the typically developing version of the GPD algorithm (GPD-TD, yellow) and for the version of the GPD algorithm used for participants with CP (GPD-CP, blue). Negative values indicate delays relative to GPD-MoCap.

Figure 5

Gait phase duration relative to motion capture (MoCap) as a precentage of gait cycle for (a) CP gait phase detection (GPD) and (b) typically developing (TD) GPD. Each color indicates a gait phase, i.e., loading response (LR), mid-stance (MSt), terminal stance (TSt), pre-swing (PSw), initial swing (ISw), mid-swing (MSw) and terminal swing (TSw).

Figure 6

Bland–Altman plot for phase onset detection between CP gait phase detection (GPD) and motion capture (MoCap). Limits of agreement (gray dashed line) are the averaged difference (red line) ± 2 SD. Each color represents a gait phase, i.e., loading response (LR), mid-stance (MSt), terminal stance (TSt), pre-swing (PSw), initial swing (ISw), mid-swing (MSw) and terminal swing (TSw). A total of 700 data points were used from both CP GPD and MoCap.