Fitts's Law using lower extremity movement: Performance driven outcomes for degenerative lumbar spinal stenosis

A paucity of objective outcome measures exists for assessing movement disorders, including degenerative lumbar spinal stenosis (LSS). Fitts's Law provides a novel approach to clinical outcome measurement since performance is resistant to learning, and task difficulty can be altered. The objective of the present study was to compare, using a Fitts's task, movement performance of individuals with and without LSS to determine if motor difficulties that arise with LSS impede the planning, initiation, or execution of deliberate lower limb movements. Twelve pre-surgical LSS patients and twelve control participants from the community performed a Fitts's Law (foot reaching) task, while LSS participants also completed pain and disability questionnaires. Fitts's Law was evident for both groups, however the LSS group's movements were more adversely impacted as task difficulty increased. Specifically, the LSS group's movement time and time to peak velocity (ttPV) increased as task index of difficulty increased, while peak velocity decreased. Correlations between ttPV and leg pain, and with stenosis impairment severity respectively, provided evidence that less support leg pain and less stenosis impairment severity yield faster ttPV in the moving leg at the highest index of difficulty. Therefore a lower extremity Fitts's Law task captured differences in the planning and execution of leg movements between healthy and LSS populations.