Introduction: Botulinum toxin type A (BoNT-A) injections are known to improve walking impairments and activity in spastic hemiparetic stroke patients presenting with a stiff-knee gait [Caty GD, Detrembleur C, Bleyenheuft C, Deltombe T, Lejeune TM. Effect of simultaneous botulinum toxin injections into several muscles on impairment, activity, participation, and quality of life among stroke patients presenting with a stiff knee gait. Stroke 2008;39(October (10)):2803-8]. The aim of the present study was to understand how the improvement of mechanical variables during gait is controlled by the central nervous system after BoNT-A injections. Therefore, we used Kinematic Segmental Coordination (KSC), i.e. the kinematic covariation law of elevation angles between lower limb segments, to assess their effect on gait control. As far as we know, this has never been studied before.
Methods: Twenty chronic hemiparetic stroke patients presenting with a stiff-knee gait performed an instrumented gait analysis at the same walking speed before and 2 months after BoNT-A injection in several spastic muscles. We used the kinematic recordings previously obtained by Caty et al. [Caty GD, Detrembleur C, Bleyenheuft C, Deltombe T, Lejeune TM. Effect of simultaneous botulinum toxin injections into several muscles on impairment, activity, participation, and quality of life among stroke patients presenting with a stiff knee gait. Stroke 2008;39(October (10)):2803-8] and computed KSC following Borghese's methodology. The treatment effect was tested using a repeated measures ANOVA.
Results: BoNT-A injections allowed a statistically significant improvement in KSC of both lower limbs (p=0.004). Moreover, the unaffected side KSC reached normal values after BoNT-A injections.
Conclusion and discussion: BoNT-A allowed an improvement in KSC of the affected lower limb and a normalization of KSC of the unaffected limb. This improvement could either be due to a mechanical effect or a central effect of BoNT-A via the spinal central pattern generators (CPGs).