JOINT MOMENTS EXHIBITED BY CHRONIC STROKE SUBJECTS WHILE WALKING WITH A PRESCRIBED PHYSIOLOGICAL GAIT PATTERN

Abstract

Purpose/Hypothesis: The goal of this study was to calculate lower extremity joint moments exhibited by hemiparetic stroke subjects while walking with a physiological normal gait pattern prescribed by a robotic gait-orthosis. Number of Subjects: 5 individuals with chronic unilateral stroke (3L, 2R) and 7 age-matched controls participated in this study. Materials/Methods: A Codamotion (Charnwood Dynamics, UK) motion analysis system was used to track the kinematic patterns of the subject's pelvis and legs at 100 Hz as they walked in the Lokomat. The legs were attached to the Lokomat by instrumented cuffs at the thigh and calf capable of measuring the interaction forces between the subject and Lokomat. With minimal body-weight support, subjects walked at four speeds on an instrumented treadmill capable of measuring ground reaction forces. For all trials, subject marker positions, Lokomat kinematics and leg cuff forces, and ground reaction forces were recorded for 30 seconds. Through a custom inverse dynamics model the ankle, knee, and hip joint moments were calculated in both the frontal and sagittal planes. A 2-way AN OVA was used to investigate differences in joint moments between control, involved, and uninvolved legs (alpha = 0.05). Results: Despite being trained under normal gait kinematic patterns, stroke subjects exhibited significant differences in numerous joint moments. Specifically the involved lower limb experienced greater ankle inversion during both swing and stance phases and less knee extension moments throughout stance phase than either the controls or the uninvolved limb (p < 0.05). Interestingly, during stance, the uninvolved limb of stroke subjects demonstrated greater hip adductor moments and greater knee varus moments compared to either the controls or the stroke subjects involved limb (p < 0.05). Conclusions: Despite being guided through a symmetric gait pattern stroke subjects were unable to exhibit symmetric joint moments. Clinical Relevance: Clinically there is a prevalence towards muscle inverters exhibiting greater activation than everters, which is expressed as an inversion moment present throughout the gait cycle. The decreased ability of stroke subjects to transfer and maintain weight onto their involved limb may arise from the involved limbs lack of sufficient knee extension torque during early to mid stance.