An artifical feedback model of the leg drop pendulum test: implications for studying and evaluating spastic cerebral palsy

Reports on ongoing work in the modeling of the leg drop pendulum test as a means of assessment in spastic cerebral palsy. In previous papers it was demonstrated that a passive model is not adequate for modeling the limb of a subject with spastic cerebral palsy. Succeeding papers showed that the addition of a set of velocity feedback loops, around a passive plant, could accurately represent both normal and spastic limbs. This paper uses that model to document changes in spasticity after a simple clinical intervention. The intervention consists of 15 minutes of reciprocal vertical motion. By optimizing feedback parameters so that model data fits actual limb position data changes in the gains of the model´s feedback loops are demonstrated. These gain changes are suggestive of an additional mechanism for spasticity beyond the hypersensitive stretch reflex. It will be argued that the model represents a possible means of evaluating clinical change as well as fertile ground for further study