Kinematics and Dynamic Stability of the Locomotion of Polio Patients ∗ †

The study reported in this article was conducted to propose a set graphical and analytical tools and assess their clinical utility by analyzing gait kinematics and dynamics of polio survivors. Phase plane portraits and first return maps were used as graphical tools to detect abnormal patterns in the sagittal kinematics of polio gait. Two new scalar measures were introduced to assess the bilateral kinematic symmetry and dynamic stability of human locomotion. Nine healthy subjects and seventeen polio patients were involved in the project. Significant increases in the knee extension and ankle plantar flexion of polio patients were observed during the weight acceptance phases of their gait. Polio patients also exhibited highly noticeable excessive hip flexion during the swing phase of their ambulation. Using the proposed symmetry measure, we concluded that polio patients walked less symmetrically than normals. Our conclusion, however, was based on the bilateral symmetry in the sagittal plane only. Finally, we observed that polio patients walked significantly less stably than normals. In addition, weaknesses in lower extremity muscles of polio patients were found to be an important factor that affected stable ambulation. ∗Supported by a grant from the Whitaker Foundation †This article has appeared in the August 1996 issue of ASME Journal of Biomechanical Engineering, Vol. 118, pp. 405-411 ‡Mechanical Engineering Department, Southern Methodist University, Dallas, TX 75275