Lower limb coordination in hemiparetic subjects: impact of botulinum toxin injections into rectus femoris.

Botulinum toxin (BTX) injection into rectus femoris (RF) is a therapeutic modality used to improve knee flexion during the swing phase of gait in hemiparesis. The impact of this treatment on lower limb coordination is unknown. The authors evaluated whether BTX injection into RF is associated with modifications of intersegmental coordination in hemiparesis. The authors evaluated gait in 10 control and 14 hemiparetic subjects with low peak knee flexion associated with inappropriate RF activity in mid-swing, using 3-dimensional analysis before and 1 month after BTX injection into RF (Botox, 200 units). Thigh-shank coordination was measured in the sagittal plane by averaging the continuous relative phase (CRP(Thigh-Shank)) during each phase of the gait cycle in both lower limbs. The CRP is a validated metric that integrates angle positions and velocities of 2 limb segments to quantify their temporal-spatial coordination. Before treatment, the low peak knee flexion in hemiparetic subjects (paretic limb 29 +/- 9 degrees) was associated with a decreased CRP(Thigh-Shank) in the paretic limb in swing (paretic limb 26.0 +/- 16.6 degrees vs controls 73.5 +/- 7.4 degrees, P < .001) and with a trend of an increased CRP(Thigh-Shank) in the nonparetic limb over the full gait cycle (nonparetic limb 77.9 +/- 14.1 degrees vs controls 66.2 +/- 19.8 degrees, P = .083). After treatment, the CRP(Thigh-Shank) increased by 11.9 degrees in the swing phase of the paretic limb (P = .002) and decreased by 8.0 degrees over the full gait cycle ( P = .002) in the nonparetic limb. BTX injection into RF was associated with improved thigh-shank coordination in parts of the gait cycle, in both injected paretic and noninjected nonparetic limbs.