Characterization of Gait and Fatigue in Children and Adults with Spinal Muscular Atrophy Using Instrumented Footwear (P5.057)

Objective: To determine the feasibility and validity of using instrumented footwear to characterize gait and fatigue in children and adults with spinal muscular atrophy (SMA). Background: Gait impairments are common in SMA and have been described using clinical assessments and instrumented walkways. Fatigue is quantified by a decrease in gait velocity from the first minute to the last minute of the six-minute walk test (6MWT). Continuous evaluation of over-ground walking has not been studied. Design/ Methods: Nine ambulatory SMA participants age 27.9 years (range 11.0 - 51.8) completed the 6MWT and 10-meter walk/run (10MWR) wearing instrumented footwear (SoleSound). Data were simultaneously collected using the Gaitrite instrumented walkway. The average root mean square error (RMSE) was calculated for stride time, stride length, and velocity to determine criterion validity. The time derivative for cadence was calculated from SoleSound during the 6MWT to evaluate patterns of fatigue. Gait patterns were evaluated using pressure sensors during the 10MWR. Results: All participants completed the 6MWT and 10MWR. The average deviations (mean RMSE +/- SD) were 0.011±0.008s, 2.55±0.68cm, and 2.21±0.48cm/s for stride time, stride length and velocity, respectively. These deviations ranged from 0.84-2.18[percnt] for all 3 variables. Participants walked slower in the last minute compared to the first (21.4±10.3[percnt]). This pattern of fatigue was also reflected in a negative time derivative for cadence (-1.154±0.637 steps/min²). Participants spent, on average, 52.13±8.05[percnt] of the gait cycle on their forefoot. The average initial forefoot contact occurred early in the gait cycle (18.00±13.98[percnt]). Conclusions: Gait and fatigue can be well characterized under different conditions using instrumented footwear. Agreement was excellent between both methods. SoleSound characterized patients with SMA as walking predominantly on their forefoot. Instrumented footwear also permit assessment under variable conditions. Better understanding of the gait disturbances should inform on-going treatment efforts and provide a more sensitive outcome measure. Disclosure: Dr. Montes has received personal compensation for activities with Isis Pharmeceuticals as a consultant. Dr. Zanotto has nothing to disclose. Dr. Dunaway has received personal compensation for activities with ISIS Pharmaceuticals, Inc. as a consultant. Dr. Salazar has nothing to disclose. Dr. De Vivo has received personal compensation for activities with Isis Pharmaceuticals as a consultant. Dr. Agrawal has nothing to disclose.