Trans-tibial amputee gait: time-distance parameters and EMG activity

Gait analysis of trans-tibial (TT) amputees discloses asymmetries in gait p arameters between the amputated and sound legs. The present study aimed at outlining differences between both legs with regard to kinematic parameters and activity of the muscles controlling the knees. The gait of 14 traumati c TT amputees, walking at a mean speed of 74.96 m/min, was analysed by mean s of an electronic walkway, video camera, and portable electromyography sys tem. Results showed differences in kinematic parameters. Step length, step time and swing time were significantly longer, while stance time and single support time were significantly shorter on the amputated side. A significa nt difference was also found between knee angle in both legs at heel strike . The biceps femoris/vastus medialis ratio in the amputated leg, during the first half of stance phase, was significantly higher when compared to the same muscle ratio in the sound leg. This difference was due to the higher a ctivity of the biceps femoris, almost four times higher than the vastus med ialis in the amputated leg. The observed differences in time-distance param eters are due to stiffness of the prosthesis ankle (the SACH foot) that imp edes the normal forward advance of the amputated leg during the first half of stance. The higher knee flexion at heel strike is due to the necessary s ocket alignment. Unlike in the sound leg, the biceps femoris in the amputat ed leg reaches maximal activity during the first half of stance, cocontract ing with the vastus medialis, to support body weight on the amputated leg. The obtained data can serve as a future reference for evaluating the influe nce of new prosthetic components on the quality of TT amputee's gait.