Swing-through gait with free-knees produced by surface functional electrical stimulation

The swing-through gait is often the gait of choice for those crutch walkers who can perform it. However, a practical (sufficiently low energy and sufficiently fast) gait is usually not achievable by paraplegic individuals with thoracic lesions. Functional electrical stimulation (FES) was used to assist three spinal cord injured (SCI) subjects with complete thoracic lesions at T11, T11 and T6 to ambulate with a swing-through gait patten. Eight channels of surface stimulation were used to bilaterally stimulate knee extensors, knee flexors, hip extensors and hip flexors. The stimulation sequence was controlled by a computer that implemented a finite-state, rule-based control strategy according to sensor inputs. Over a long, level walkway, the T11 subjects averaged 0.40 m/s and 0.38 m/s for distances of 56 m and 51 m; the T6 subject averaged 0.30 m/s for 43 m. Using a motion analysis system, the gait patterns of two of the subjects were compared to those of a trained, non-impaired subject. The SCI subjects spent more time in both double support phases (when both crutches and both feet contact the floor) than did the non-impaired subjects, leading to a loss of momentum and hence a slower and less efficient gait. In conclusion, an FES assisted swing-through gait is shown to be a potentially useful mode of FES gait.