Validating stroke-induced bilateral ankle coordination deficits using bilateral ankle measure relationship with motor functions in lower limbs

BACKGROUND: Coordinated control between the bilateral ankle joints plays an important role in performing daily life functions, such as walking and running. However, few studies have explored the impact of stroke on movement disorders that decrease the coordination control of the bilateral extremities and may decrease daily activities that require coordination control of the bilateral ankles. This study aimed to investigate the coordination control of the bilateral ankles using a novel bilateral ankle measurement system and evaluate the relationship of bilateral movement coordination control deficits with motor and functional performances of the lower extremities in patients with stroke. METHODS: Twenty-one healthy adults (36.5 ± 13.2 y/o) and 19 patients with chronic stroke (58.7 ± 10.5 y/o) were enrolled. A novel measurement device with embedded rotary potentiometers was used to evaluate bilateral ankle coordination control. Participants were asked to move their dominant (non-paretic) foot from dorsiflexion to plantarflexion position and non-dominant (paretic) foot from dorsiflexion to plantarflexion position (condition 1) simultaneously, and vice versa (condition 2). Alternating time and angle for coordination control with movements of both ankles were calculated for each condition. Motor and functional performance measurements of the lower extremities included the lower-extremity portion of the Fugl-Meyer assessment (FMA-LE), Berg Balance Test (BBS), Timed Up and Go Test (TUG), and Barthel Index (BI). RESULTS: Compared with the healthy group, alternating time was shorter in the stroke group by 8.3% (p = 0.015), and the alternating angles of conditions 1 and 2 were significantly higher than those of the healthy group by 1.4° (p = 0.001) and 2.5° (p = 0.013), respectively. The alternating angle in condition 2 showed moderate correlations with TUG (r = 0.512; p = 0.025), 10-m walk (r = 0.747; p < 0.001), gait speed (r = − 0.497 to − 0.491; p < 0.05), length (r = − 0.518 to − 0.551; p < 0.05), and BI (r = − 0.457; p = 0.049). CONCLUSION: Stroke decreases alternating time, increases alternating angle, and shows bilateral ankle coordination control deficits temporally and spatially. A higher alternating angle is moderately to highly associated with motor function and lower limb function in patients with stroke.