Use of gait parameters to predict the effectiveness of botulinum toxin injection in the spastic rectus femoris muscle of stroke patients with stiff knee gait.

BACKGROUND: Botulinum toxin type A (BTX-A) injection in the rectus femoris (RF) is commonly used to treat decreased peak knee flexion in swing phase of the gait in hemiplegic patients. However, the effect of BTX-A varies between 5° to 10° depending on the studies. Peak knee flexion also increases during fast gait and could constitute a way to predict the effect of BTX-A injection in the RF. AIM: To determine if changes in gait parameters during fast gait before injection could predict the effect of RF BTX-A injection on peak knee flexion in hemiplegic patients. DESIGN: Prospective observational study. SETTING: A neurological rehabilitation department in a university hospital POPULATION: Twenty two hemiplegic patients with stiff knee gait mainly due to spasticity of the RF and treated by RF-BTX-A-injection. METHODS: Patients' gait was analyzed using a 3D motion analysis system and force plates. The gait recordings were performed before (PRE-RF-BTX-A:spontaneous and fast gait speed) and one month after RF-BTX-A-injection (POST-RF-BTX-A:spontaneous gait speed). Correlations between the percentage change in gait parameters during fast gait before RF-BTX-A-injection and the percentage increase in peak knee flexion POST-RF-BTX-A injection at spontaneous speed were analyzed. RESULTS: The percentage improvement in peak knee flexion in the fast gait condition before injection was the only parameter correlated with the percentage increase in peak knee flexion POST-RF-BTX-A injection. This was confirmed by a stepwise linear regression. The percentage increase in peak knee flexion POST-RF-BTX-A injection was also correlated with the percentage increase in knee flexion angular velocity at toe-off in the fast gait condition. CONCLUSION: The percentage increase in peak knee flexion in swing during fast gait before injection is a useful predictor of the increase in peak knee flexion following RF BTX-A injection in chronic stroke patients with RF spasticity. CLINICAL REHABILITATION IMPACT: In stroke patients with SKG which is mainly caused by spasticity of the RF muscle, evaluating changes which occur during fast gait might help the therapist to identify patients who would benefit the most from BTX-A injection in the RF muscle.