Measurement of muscle stiffness using robotic assisted gait orthosis in children with cerebral palsy: a proof of concept

Abstract

Purpose. To evaluate the feasibility and reliability of a novel stiffness assessment tool implemented in the driven gait orthosis Paediatric Lokomat; to investigate the influence of single robotic-assisted gait training (RAGT) on muscle stiffness in children with cerebral palsy (CP).

Methods. Ten children with spastic CP conducted a single standard RAGT session and stiffness was assessed before and after the RAGT. Nine of the ten subjects were tested twice on the same day to investigate test–retest reliability, intraclass correlation coefficients (ICCs), standard error of measurement (SEM), coefficient of variation of the method error (CV_ME) and resistive torques during passive leg movements (stiffness in Nm/°) were calculated.

Results. ICCs showed high reliability (0.83–0.97) for hip and knee movements. SEM and CV_ME indicated 0.028–0.085 Nm/°, 9.5–23.0% of test–retest variability in hip and 0.018–0.064 Nm/°, 13.3–43.5% in knee measures. Using the assessment tool, a significant decrease in muscle stiffness in participants, especially in children with high levels of muscle tone, could be shown after a single session of RAGT.

Conclusions. The assessment tool L-STIFF is a feasible tool for automated measurement of stiffness in children with CP, but it is not sensitive enough to record small changes in muscle tone.

Keywords:

• Assistive device
• cerebral palsy
• child
• muscle stiffness
• spasticity
• robotic assisted gait training

Acknowledgements

We wish to express appreciation to the physical therapist Claudia von Allmen and Petra Marsico-Niederberger for their generous help during the measurements. A further thank you goes to Beth Padden, MD, for carefully reviewing the manuscript. Alexander Duschau-Wicke and Lars Lünenburger, PhD, deserve special recognition for their help in the adaptation and development of the L-STIFF Software and the new L-STIFF Evaluation Tool. We are very grateful to all the children and their parents, who were willing to participate in this study.

Conflict of interest: During the accomplishment of the study AS has been employed by the Rehabilitation Centre Affoltern am Albis, University Children's Hospital Zurich. During the submission of the paper to Disabil Rehabil Assist Technol AS has been employed by Hocoma AG. The authors alone are responsible for the content and writing of the paper.