Efficacy of Botulinum Toxin Injections in the Rectus Femoris to Treat Stiff Knee Gait Following Acquired Brain Injury

Pathophysiologic factors that may contribute to stiff knee gait in persons with brain injury
are muscle hypertonicity of the quadriceps muscles, hip flexor weakness, and over activity
of the gastrocsoleus muscles in terminal stance(1). Kerrigan et al (2) reported that
hyperactivity of the Rectus Femoris (RF) during swing phase was a key contributor to this
dynamic swing phase deficit in adults with spastic paresis. Overactivity of the RF muscle
during early swing phase has also been identified as a major contributor to stiff knee gait
dysfunction in children with cerebral palsy (3). Recognition of the role of RF over-activity
in stiff knee gait in the cerebral palsy population has led to surgical and medical
interventions aimed to minimize this constraint on swing phase mechanics, such as RF
transfers, RF release, and Botulinum toxin injections (BTX-A)(4,5). Research in the cerebral
palsy population supports the application of these interventions to improve knee flexion
during swing phase and improve overall gait function and efficiency (6).

The applicability of these directed interventions for stiff knee gait, particularly the less
invasive BTX-A injections to RF, has not been well examined in adults with spastic paresis.
Two research groups (7,8) examined the immediate effects of a motor branch block of RF in
persons post-stroke with stiff knee gait and reported improved maximum knee flexion and mean
knee flexion velocity during preswing and swing phase following the block. Very few
studies9,10 to date examined the short-term effects of BTX-A injection to RF on gait
function and energy cost during walking in persons post-stroke who ambulated with stiff knee
gait. Stoquart and colleagues9 found that at two months following BTX-A injections,
subjects had improved maximum knee flexion during swing phase and improved knee flexion
velocity during toe off. Energy cost improved only in that subset of subjects who had
greater than 10 degrees of knee flexion during swing phase prior to BTX-A injections. The
results of this prospective observational study provided initial support for the efficacy of
BTX-A intervention for stiff knee gait in adults post-stroke, however, the authors only
examined the short-term effects of this intervention(9). Also, this study had limitations in
its methodology, as gait function pre- and post-BOTOX® intervention was assessed using an
automated treadmill as opposed to gait analysis during overground walking at self selected
gait speed. Further research is needed to determine if there is longer-term benefit of
BTX-A injections to RF on gait function in the brain injury population.

Research Design:

- Double-blind randomized controlled trial

- Subjects will be randomly assigned to experimental or control group

- The experimental group will receive BTX-A injection to rectus femoris (RF) followed by
usual care

- The control group will receive saline injection to RF followed by usual care

- Subjects and researchers will be blinded to group assignment

- Three-dimensional computerized gait assessments will be conducted pre-treatment (within
2 weeks prior to BOTOX®/placebo injection), 1 month post and 4 months post-injection