Spasticity compensation using Hermes, a novel negative stiffness Ankle-Foot-Orthosis
Academia (TU Delft, LUMC), industry (InteSpring, OIM Orthopedie) and health care partners (Basalt, Kennisnetwerk CVA Nederland) are codeveloping a revolutionary negative stiffness Ankle-Foot-Orthosis: Hermes. The project will follow up on the NWO-TTW NeuroCIMT-project ‘Stiffness as Needed’ which developed this technology to TRL 4, compensating spastic ankle joint stiffness, enabling the available dorsiflexor muscles to regain control.
Plantarflexor spasticity in combination with dorsiflexor paresis cause equinus or equinovarus foot affecting safe mobility. Conventional ankle-foot orthoses (AFOs) are stiff, and support mobility by attaining foot clearance during swing, but at the cost of ankle motion, push off during gait, and activities requiring a mobile ankle, like dressing and car-driving. In the Netherlands alone there are about 70,000 registered AFO users.
“Show and Transfer I" will bring the design from a generic, though tuneable, research prototype TRL4 to a personalised demonstrator prototype for home use TRL6. At the expense of complexity and weight, the TRL4- prototype allows tuning to a range of patient’s needs. For home use, the hinge should be redesigned for safety and durability and should accommodate individual patients’ needs using personalised torque-angle characteristics. With cross-sectional patient studies in lab setting currently underway, a “Validate and Transfer II” would enable longitudinal studies with home use.
Improved ankle mobility reduces complications of spastic paresis (e.g., contractures, high energy expenditure), allows renewed muscular control, and secondarily lowers the limitations in activities, enhancing quality of life.