Stratégies d’optimisation d’utilisation d’un exosquelette pour la réadaptation locomotrice des patients avec des troubles neuromoteurs : stratégies d’optimisation d’utilisation d’un exosquelette pour la réadaptation locomotrice des patients avec des troubles neuromoteurs

Cerebral palsy is the leading cause of childhood gait limitations, affecting 2 to 3 children per 1000 births. It is defined as a movement and posture disorder that causes functional limitations due to the damage of the immature brain. Spasticity, excessive co-contraction, muscle weakness and bone deformities limit the autonomy of these children. Their walking is slower and more unstable compared to that of typically developing children. Recently, exoskeletons for gait rehabilitation (e.g., Lokomat®) have been shown to be effective in adults with neuromotor disorders. However, evidence supporting the effectiveness of such a training modality in children with cerebral palsy remains insufficient. In addition to its apparent relevance for gait rehabilitation, the Lokomat® offers the possibility of evaluating certain motor functions (i.e., muscle strength, spasticity). However, these tools are not used due to the lack of information on the reliability of its measurements.  The objective of this thesis was to assess the relevance of the use of robotic orthoses « Lokomat® » for the assessment of motor functions and for gait rehabilitation in patients with neuromotor disorders, such as cerebral palsy. To respond to our general objective, three specific objectives have been defined in order to: (1) provide information on the applicability and effectiveness of robotic locomotor rehabilitation for improving gait parameters in children with cerebral palsy; (2) evaluate the psychometric qualities of the Lokomat® integrated tools measuring spasticity and isometric force in order to determine their suitability for regular clinical use; and (3) propose a systematic approach based on electromyography to personalize Lokomat's settings to promote optimal training for hip extensor strength.  Carried out in a « Living Lab » context involving the patient, parents, clinicians and researchers, our 1st study established a realistic Lokomat® training protocol (2 sessions / weeks for 12 weeks) that can be easily transferred to the clinic. This intervention on 24-patients led to significant improvement in the lower limb isometric strength (25-74%) and walking capacities such as walking speed (+20%), step length (+14%) and endurance (+24%). Improvements in muscle strength and endurance had sustained when measured at a 6-month follow-up. In the same study, our results showed that robotic training had a positive effect on muscle strength and gait capacity whatever the level of severity (GMFCS levels II-IV). In the second and third studies, the reliability of the two integrated tools of the Lokomat® (L-FORCE and L-STIFF) assessing muscle strength and spasticity respectively was measured using intraclass correlation coefficient (ICC) and standard error of measurement (SEM). The intra- and inter-tester reliability of the L-FORCE tool was good to excellent (ICC = 0,70 - 0,87 et SEM = 11,9 - 22,5%) for measuring isometric strength of hip and knee flexors and extensors in children with cerebral palsy. For the L-STIFF tool, the intra-tester reliability was moderate to excellent (ICC = 0.49 – 0.89, SEM = 7 – 16%) while the inter-tester reliability was acceptable to good (ICC = 0.32 – 0.70, SEM = 6 - 39%). These two tools have thus greater intra- and inter-tester reliability than conventional clinical tests for measuring isometric strength and spasticity in children with cerebral palsy. Finally, our fourth study is a proof of concept of a systematic approach based on electromyography to personalize and optimize the Lokomat® settings that aim to maximize muscle activity of hip extensors in two post-stroke patients. We were able to set personalized parameters for a targeted Lokomat® training using an easily implementable protocol. It only took two test sessions to determine these settings. The two cases presented in the study showed a significant increase in muscle strength of the hip extensors (+43 and 114 %) as well as improvement in endurance (+37% and +150%) and mobility (from 4 to 7 on the Modified Functional Ambulation Classification).  In conclusion, the results of our studies support the use of the Lokomat® robotic orthosis for gait rehabilitation in children with cerebral palsy. This approach provides a standardized training environment and allows an objective and mostly reliable assessment of changes in strength and spasticity of the lower limb. Finally, optimization of Lokomat® training appears to be feasible and easy to implement (i.e., based on electromyography and with only two additional Lokomat® training sessions).

Keyphrases: cerebral palsy, robotic rehabilitation, gait analysis, kinematics, electromyography, intervention optimization, measurement reliability, isometric muscle strength, spasticity