Development of a Gait Rehabilitation System Using a Locomotion Interface Hiroaki Yano*, Kaori Kasai*, Hideyuki Saitou*, Hiroo Iwata* * University of Tsukuba Tsukuba, 305-8573, JAPAN yano@esys.tsukuba.ac.jp kasai@intron.kz.tsukuba.ac.jp md995493@md.tsukuba.ac.jp iwata@kz.tsukuba.ac.jp
1. Introduction During treatment for gait rehabilitation, physical therapists explain the motion required for walking to patients using words or by physically handling the patient s body. However, the number of therapists that are available for this task is insufficient compared with the number of patients that require treatment, which increases the workload of the therapists. It is difficult for them to teach natural-looking leg movements to patients, even if the patients have the ability to acquire such a motion. In addition, it will be necessary to develop more assisted movement systems with the advent of the aging society. To solve these problems, various systems using robotic mechanisms have been developed. Hesse et.al have developed the Gait Trainer [1]. This consists of two footplates positioned on two bars (couplers), two rockers and two cranks that provided the propulsion. It is based on a doubled crank and rocker gear system, which can generate a 3-D motion for each leg. However, since the trajectory of the footpads is fixed by the crank and gear system, it needs to be set up for each individual patient each time that it is used. Hitachi Ltd. markets commercial rehabilitation systems using two belt-type treadmills [2]. These are already used in many hospitals, but they only generate horizontal motion to the patient. In this study, we developed a locomotion interface that can simulate uneven terrain for the user by utilizing two 2DOF motion-platforms. The system can easily have its trajectory changed by altering the data in a PC attached to the apparatus. We then applied our locomotion interface to gait rehabilitation. We conducted a 3-month long gait rehabilitation course with a hemiplegic patient using our system. The effectiveness of our system was evaluated through electromyography, video analysis and the measurement of physical values such as average velocity and step length. 2. GaitMaster2 We developed a locomotion interface named the GaitMaster2 (GM2). The GM2 is a manipulator-type locomotion interface [3]. It
has two footpads that trace a virtual floor beneath each of the user s feet. When the user moves one of his/her feet forward (swing phase), the footpad under that foot follows it like a shadow over the virtual floor. At the same time, the other footpad (stance phase side) moves back by the same distance as the swing phase foot moves forward. By iterating this motion, the user can walk over an infinite variety of uneven virtual terrain while his/her position remains localized in the real world. Figure 1 shows a pictorial overview of the GaitMaster2. Figure 2 shows the system configuration of the GM2. The GM2 consists of two 2DOF motion-platforms, which are chain drive jacks equipped with an AC servomotor and an optical rotary encoder. Each motion-platform has a 300mm x 270mm footpad on top of them. The footpads have a working volume that is 670mm in the horizontal direction and 130mm in the vertical plane. The maximum velocity of the footpads is 1470mm/sec. The payload of each motion-platform is approximately 80 kg. Wire length sensors measure the positions of each of the user s feet. We measure the position of the footpads by using an optical rotary encoder on the AC servomotors. The GM2 is controlled by a PC (Pentium III 500 MHz, with a Windows 2000 OS). We can change the trajectory of the footpad easily just by changing the data. Figure 1 Overview of GaitMaster2 Figure 2 System configuration of GaitMaster2
3. Gait rehabilitation system using GaitMaster2 Gait rehabilitation is usually applied to patients who have developed trouble in walking due to injured bones, joints, nerves and muscles caused by some trauma or disease. In general, gait rehabilitation begins with training designed to spread his/her weight evenly onto both feet. Next the patients learn how to move their body and how to walk by themselves. Usually a therapist explains the motion of walking to the patient in words or by physically handling the patient s body to assist them in acquiring a voluntary gait. These methods are based not only on the concept of restudy, but also on the idea that alternative nerves can be activated even though the nerves usually used to determine gait are damaged. However, it is difficult for a therapist to repeat the same motion for a long time by handling the patient s body, since they would soon tire and would not have enough time to train each patient adequately. If the same level of treatment could be realized by using some mechanical device, therapists would be able to regulate the motion of the patient s foot with less fatigue. The other advantage of this system is that a therapist who isn t strong enough to manipulate the patient s Figure 3 Gait rehabilitation using GM2 Figure 4 Overview of the gait rehabilitation system using GM2 with the patient
body could operate it via the equipment. In order to realize this function, the equipment should have the ability to move the user s foot on any trajectory, and the capability to repeat this over a long time. Our locomotion interface is suitable for this purpose. We developed a gait training system by using the GM2. The GM2 follows the trajectory taken by a healthy individual s foot when walking, independent of the patient s will. We call this gait training method Enforced-gait. The patient mounts the GM2 and iteratively experiences the correct trajectory for each foot. In this way they can acquire the motion of a healthy individual. In a feasibility study, we can set up any step length, height and walking cycle (Figure 3). An overall view of the gait rehabilitation system using GM2 is shown in Figure 4. We installed a safety frame around the GM2 for the rehabilitation program. The patients pull themselves up by grasping the frame, which is also equipped with wide steps to allow the patient to get on and off the GM2 easily. Safety belts are included so that the patient can remain suspended from the safety frame in an emergency situation. We changed the size of each footpad to 320 mm x 660 mm, and we used the bindings from a snowboard to fix the patient s feet to the footpads. We fixed the patient s feet quite loosely so that he/she could move their feet a little. 4. Gait training with a hemiplegic patient We conducted a 3-month gait-training course using the GaitMaster2 for a hemiplegic patient who was paralyzed down her left side after suffering a stroke. The patient was a 57 year-old woman. She developed cerebral infarction 7 years ago. Her impairment is left hemiplegia, and she wears a short leg brace (SLB) on her left leg. She can realize an independent but languid and shuffling gait by using a T cane. This is a three-point gait using T cane, right leg and left leg. She has a shortened step length, longer duration of stance and shorter duration of swing phase on the affected left side than normal. Her usual
walking speed is 6.5 m/minute with a 1.3 Hz step. She receives a day care service and a home management service. However, she did not actively attend any therapies during the time of our tests. We conducted the following 8-step gait training once a week over a period of 15 weeks by using the GM2. 1. Measure the velocity and step-length of the gait after a 3-min long passage of real walking. 2. Adjust the walking load (speed, step length) of the patient on GM2. We set the velocity to be twice as fast as the 3-min walk, depending on the patient s condition. 3. Take a rest of more than 5 minutes. 4. First 15-min rehabilitation session on GM2, using velocity and step-length derived in Step 2. 5. Take a rest of more than 5 minutes. 6. Second 15-min rehabilitation on GM2 7. Take a rest of more than 5 minutes. 8. Measure walking velocity and step-length after a real 3-min passage of walking. The trajectories of the footpads follow the trajectory of a healthy individual s foot on a treadmill. We conducted this training for a total of 15 times, once each week. We spent the first 10 weeks in determining the training program described above, and then we conducted the program over the latter 5 weeks. A physical therapist attended all of the training sessions. He assisted the patient when she got on and off the equipment. He also gave her advice about her gait. Before the rehabilitation, we gave informed consent about our gait rehabilitation program to the patient and her family. We received their approval in writing.
5. Gait evaluation 5.1 Velocity and step-length Figure 5 and Figure 6 respectively show the transition of the velocity and step-length in a real 3-min passage of walking in the latter 5 weeks of the rehabilitation. The result reveals that the final velocity on GM2 after the training was 20 m/min with a 1.1 Hz step-cycle. All of the data after the rehabilitation eclipse the data before the rehabilitation. These transitions show a moderate improvement. We did not find an appreciable long-term change, but we did see a significant improvement before and after the session on the same day throughout the rehabilitation course. The patient reported that she had the feeling that her paralytic leg was lightened, and this feeling continued into the next day. This means that our system has an advantageous effect in the short term. Figure 5 Transition of walking velocity in gait rehabilitation Figure 6 Transition of step during gait rehabilitation
5.2 Video analysis We shot a video of the patient s gait during all training. We analyzed the videos of the rehabilitation. We analyzed her gait whilst on GM2 and also in a real environment. Initially the patient was quite fearful on the GM2. She couldn t inflect the knee and hip joints of her paralytic leg. She also left her weight on the normal leg during the rehabilitation. However, she gradually acquired the ability to inflect the knee and hip joints on the paralytic leg by herself. The therapist gave her advice, which was mainly to shift her weight onto her paralytic left leg. After the rehabilitation, we observed an improvement in her gait in a real environment. At the beginning of the rehabilitation the patient usually favored leaving her weight on the normal leg (right leg) and her shuffling gait meant that joint movement was rarely observed in her paralytic leg. However, after the 10 th rehabilitation session she gradually lifted up the planta of her paralytic leg. She could also move her paralytic left foot forward further than her right foot and could shift her weight to her paralytic left leg. 5.3 Electromyography We measured muscle function with electromyograms to evaluate the effect of the rehabilitation. We used an electromyograph, the MEG-6108 made by Nihon Kohden, which has 16 EMG channels. We measured the electromyograms of 4 types of muscle. These were the bilateral gluteus medius muscle, the hamstrings, the medial vastus muscle and the gastrocnemius muscle, and we measured both the patient s normal and paralytic sides. The gluteus medius muscle is one of the muscles attached to the hip, which is in charge of rotation and flexion of the hip joint. It maintains the standing posture during walking. The hamstrings are the muscles at the back of the thigh, which are in charge of extension of the thigh and rotation of the lower thigh. They decelerate the lower limb of the swinging side when the gait switches from the swing phase to the
stance phase. The medial vastus muscle is a knee muscle, which is in charge of absorbing the shock when the foot lands on the ground. The gastrocnemius muscle is a sural muscle that is in charge of flexion of the lower thigh and the flinging-up motion used to obtain acceleration [4][5]. As a result, the medial vastus muscle and the hamstrings have distinct qualities. Figure 7 shows electromyograms of the patient s normal and paralytic side medial vastus muscles in a real walking passage. The data were measured before the 3 rd -week of rehabilitation and after the 15 th -week of rehabilitation. Before rehabilitation we could not observe any significant activation of the electromyogram for the paralytic side. However, after the rehabilitation we could see significant activation of the electromyogram for the paralytic side. The medial vastus muscle is a shock absorbing muscle. Since the patient could now lift up her paralytic leg, the landing shock was increased. Therefore the muscle was more activated than before the rehabilitation. To evaluate any short-term change we compared the electromyograms taken before and after the rehabilitation sessions on the same day. Figure 8 shows the electromyograms of the patient s hamstrings before and after the 15 th rehabilitation. As you can see, the electromyogram of the paralytic side is more activated than before. Figure 7 Long-term effects at medial vastus muscle Figure 8 Short-term effect at hamstrings
Since the hamstrings are used for controlling the lower thigh during the swing phase, it was assumed that the patient had acquired the ability to fling up her leg due to the training. 6. Discussion We cannot find any durable improvement in the velocity and step-length of the patient through the last 5 weeks of rehabilitation sessions. However, we can find significant improvement before and after rehabilitation on the same day for all of the rehabilitation sessions (short-term effect, as shown in Figure 5 and Figure 6). It has been postulated that this is caused by an overlong interval between rehabilitations. The patient reported that she felt that her paralytic leg had been lightened. The feeling disappeared after the next day. However, during video analysis and electromyography we can find a significant long-term improvement, even though the rehabilitation sessions only took place once a week. In particular, we observed that she gradually lifted up the planta of her paralytic leg during the video analysis. She reported that she attempted to follow the feeling that was memorized during the rehabilitation on the GM2 when she walked during the measurement stage after the rehabilitation (step 8 described in Chapter 4). The results of the electromyogram support this assertion. In addition, the patient acquired the ability to shift her weight to her paralytic left leg in her gait. Since she can now keep her balance, the patient s QOL (Quality of Life) is improved. She reported that she can now take out her clothes from her tansu chest. She can also use the bathroom normally when she goes out. Her experience of gait rehabilitation with the GM2 has encouraged her to voluntarily undertake more challenging tasks. As a general impression, she said, I was scared of the training at the beginning, but when I got into the swing of it, I could move my legs voluntarily. I have had a pleasant experience. Also, I remember the feeling of walking when I had good health. Incidentally, we have been unable to find any medical opinion
regarding the progress of diseases during and after the rehabilitation. From the therapist s viewpoint, the use of our system would enable them to teach a natural walking motion since they now don t need to handle the patient s leg themselves. In addition, the patient s motion can be digitized. The therapist can check the progress of the training quantitatively and plan the next training schedule objectively. If we collect these training data over a long period we could build a database for more objective rehabilitation programs. For remote medical services, a networked locomotion interface would be particularly suitable. By connecting locomotion interfaces, one for the therapist and the other for the patient, the therapist could teach motion to the patient [6]. This system could send motion information from the therapist/trainer to the remote patient directly. In this study, we can find some improvement in the patient s condition. However, the reason for the improvement remains to be clarified. We assume that the patient recreates a nerve function for improvement or else represses nervousness. We need to investigate the reason for the improvement. Fortunately, the user s position on the GM2 remains localized in the real world, so we can easily use a range of measuring equipment on the GM2. 7. Conclusion In this study, we applied our locomotion interface, the GaitMaster2, to gait rehabilitation. During rehabilitation with the GM2, the patient mounts the equipment and the footpads of the GM2 iteratively trace the pre-recorded walking motion of a healthy individual. The patient can therefore experience a correct sensation of motion and learn how to walk. From a therapist s point of view, they can now afford to conduct elaborate training regimes. A 15-week walking rehabilitation course using the GM2 was conducted with a hemiplegic patient. As a result, the effectiveness of our method has been demonstrated. In future work we plan to develop more voluntary rehabilitation algorithms for patients by using the GM2 with force sensors. We also plan to develop methods of evaluating the user s rehabilitation level.
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