Biomechanical correlates for recovering walking speed following a stroke. The potential of tibia to vertical angle as a therapy target

Background: Recovering independent walking is a priority for stroke survivors. Community walking requires speeds exceeding the average values typically achieved at discharge (0.7 m/s). To improve outcomes there is a need to clarify the factors associated with recovery of functional walking speeds. Research question: Which biomechanical variables correlate significantly with improved walking speed following rehabilitation in acute stroke patients. Methods: The study was embedded in a larger clinical trial testing efficacy of a gait training splint. Participants, within 6 weeks of their stroke and exhibiting abnormal gait, were recruited. Using a valid and reliable videobased system, specific kinematic measures were recorded before randomisation (baseline), after a 6-week rehabilitation phase (outcome) and six months after stroke (follow-up). Measures of temporospatial symmetry, knee angular velocity and tibia to vertical angle were added to clinical measures and correlated with change in speed. Results: 23 participants were recruited, (mean age 67.7 +/- 16.7 years, 19.2 +/- 9.0 days after stroke and 73.9% male), with 20/23 assessed at outcome and 17/23 at follow-up. Drop out was due to withdrawal (3) and technical failure (3). Walking speed increased by 0.15 +/- 0.21 m/s (outcome), and 0.21 +/- 0.14 m/s (follow-up) from baseline (0.50 +/- 0.20 m/s). This increase correlated with an increase in step length (r = 0.88) and change in angle of tibia at initial contact (r = -0.59), foot flat (r = -0.61) and terminal contact (r = 0.54). Significance: This study of gait recovery among acute stroke patients demonstrated modest improvements in walking speed. Walking speed by follow-up (0.71 m/s) classified the group as community walkers (> 0.66 m/s) but still too slow to safely use a pedestrian road crossing. Change in step length and tibia to vertical angle significantly correlated with increased walking speed. This finding provides distinctive targets for therapy aimed at improving community walking among stroke survivors. This hypothesis should be tested prospectively in future studies.