INVESTIGATION OF LATERAL FORCES WHILE PERFORMING VOLUN-TARY FORWARD STEPPING WITH and WITHOUT USING A CANE IN HEALTHY ADULTS and HEMIPLEGIC PATIENTS WITH STROKE.

Abstract

Hypothesis: This study investigated differences in the lateral forces while performing voluntary forward stepping with and without a cane in healthy adults and hemiplegic patients with stroke. Number of Subjects: Five hemiplegic patients with stroke (mean age=55.9 ± 11.5yrs) and five age-matched healthy adults (mean age=56.0 ± 7.0yrs) participated in this study. Materials/Methods: Four conditions, stepping forward with the left and right leg, and with and without using a cane, were tested. Ground reaction forces underneath the lower extremities and the cane were collected by two force plates and an instrumented cane, respectively. The loading duration (from onset of the increase in lateral force toward the stepping leg to the first zero crossing of the lateral force), unloading duration (onset of the increase in lateral force toward the stance leg to the second zero crossing of the lateral force), force impulses during the loading and unloading durations, and the rate of lateral force transfer prior to foot liftoff were analyzed. Results: Compared with healthy adults, patients with stroke showed longer loading duration (P = 0.003), smaller force impulse in the loading phase (P = 0.024), and slower rate of lateral force transfer (P = 0.001) when stepping with the unaffected leg without a cane; and showed longer loading (P = 0.003) and unloading durations (P = 0.01), and smaller force impulses in the unloading phase (P = 0.001) while stepping with the affected leg without a cane. Without using a cane, patients with stroke also showed longer unloading duration (P = 0.017), faster rate of lateral force transfer (P = 0.009), greater force impulse in the loading phase (P = 0.021), and smaller force impulse in the unloading phase (P = 0.017) while stepping forward with the affected leg than with the unaffected leg. While using a cane to perform the stepping, most of these patients decreased the generation of force impulses in the loading and unloading phase although the amount of the decreases did not reach a significant level (loading phase P = 0.059;unloading phase P = 0.071). No significant change was observed for the rate of lateral force transfer between the no cane and cane use conditions for the patient group either. Conclusions: To achieve a safe lateral weight transfer required prior to and during a forward stepping movement, patients with stroke appeared to lengthen the loading and unloading durations in order to compensate for their decreased ability to generate lateral impulses in the loading and unloading phases, respectively. Using a cane might partially contribute to the lateral impulse generation required for performing the stepping movement such that the impulses generated by the lower extremities decreased slightly. Clinical Relevance: For patients with stroke to step forward, the use of a cane might potentially decrease the difficulty of the lower extremities to perform the lateral weight shifting required prior to and during this movement.