Powered lower limb orthoses for gait rehabilitation

Abstract

Bodyweight supported treadmill training has become a prominent gait rehabilitation method in leading rehabilitation centers. This type of locomotor training has many functional benefits but the labor costs are considerable. To reduce therapist effort, several groups have developed large robotic devices for assisting treadmill stepping. A complementary approach that has not been adequately explored is to use powered lower limb orthoses for locomotor training. Recent advances in robotic technology have made lightweight powered orthoses feasible and practical. An advantage to using powered orthoses as rehabilitation aids is they allow practice starting, turning, stopping, and avoiding obstacles during overground walking.

Figures

Figure 1

Bodyweight supported treadmill training. Physical therapists can administer body weight supported treadmill training in the clinic. The patient's body weight is partially supported by way of a modified parachute harness worn on the trunk. Two therapists manually assist the motion of the patient's legs through a natural gait pattern. A third therapist stands behind the patient and provides trunk support. Source: The New York Times, Science News, 9/21/99. Permission to reprint photo from Michael Tweed.

Figure 2

Electromyography amplitude (root mean square, RMS) with and without manual assistance in subjects with incomplete spinal cord injury. Four subjects with incomplete spinal cord injury walked on a treadmill at 0.36 m/s with bodyweight support, with and without manual assistance. While walking under the two experimental conditions, electromyography data were recorded from 8 muscles (tibialis anterior, TA; soleus, SO; medial gastrocnemius, MG; lateral gastrocnemius, LG; vastus lateralis, VL; vastus medialis, VM; rectus femoris, RF; and medial hamstring, MH). Electromyography RMS values were averaged and standardized to the highest RMS value. Error bars indicate standard error. Electromyography amplitudes were greater in all muscles with manual assistance, but the difference was not statistically significant (p > 0.3). Source: Original figure from the Human Neuromechanics Laboratory at the University of Michigan.

Figure 3

Ankle, knee, and hip joint powers over the stride cycle for normal human walking. Heel strike is at 0% and again at 100%. Toe off occurs at ∼ 60%. The majority of the joint power comes from the ankle joint just before toe off. Source: Meinders et al. Scand J Rehab Med 30: 39-46, 1998. Permission to reprint fromTaylor and Francis Publishing.

Figure 4

Powered orthoses as assistive technology. A. The exoskeleton developed by Vukobratovic in Yugosalvia in the1970s. B. Blaya and Herr's powered ankle-foot-orthosis for drop foot correction. C. The hybrid assistive limb (HAL) is currently under development by engineers in the Cybernetics Laboratory at the University of Tsukuba in Japan. Source: A. Vukobratovic et al., Med Biol Eng, January, 1974. Permission to reprint from Peter Peregrinus Ltd. B. Blaya et al., IEEE Trans Neur Sys Eng, 12(1), 24-31, 2004. Permission to reprint from IEEE. C. Original photograph from Prof. Sankai, University of Tsukuba / Cyberdyne Inc. Permission to reprint from Yoshiyuki Sankai, University of Tsukuba. / Cyberdyne Inc.

Figure 5

Powered orthoses for power augmentation. A. The Sarcos protoype is being developed under the direction of Stephen Jacobsen with funding from the Defense Advanced Research Projects Agency (DARPA). B. BLEEX, the Berkeley Lower Extremity Exoskeleton, is under development in Homayoon Kazerooni's Laboratory at the University of California Berkeley, also with funding from DARPA. Source: A. Technology Review, p.73, July/August, 2004. Permission to reprint from MIT Technology Review. B. website: bleex.me.berkeley.edu/bleex.htm. Permission to reprint from Professor H. Kazerooni, Robotics and Human Engineering Laboratory, University of California at Berkeley.

Figure 6

Pneumatically powered orthoses at the University of Michigan. A. The patient controls the timing of assistance with push buttons in each hand through an algorithm programmed on a remote computer. The computer commands airflow into and out of the pneumatic actuators attached to the orthoses, producing assistive torque at the ankle joint. B. A patient uses the push button controllers to assist walking on a treadmill. Source: Original figure from the Human Neuromechanics Laboratory at the University of Michigan.

Figure 7

Muscle activation and kinematic patterns for gait training with powered orthoses. Data are averaged for six incomplete spinal cord subjects (ASIA C-D) walking on a treadmill with partial body weight support (0.54 m/s). Subjects walked under four conditions: without the orthoses (WO), wearing passive orthoses (PA), wearing active orthoses under therapist control (TC) and wearing active orthoses under patient control (PC). TOP: Normalized root mean square EMG of tibialis anterior (TA), soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG). BOTTOM: Mean ankle angle during the gait cycle. Plantar flexion is positive. Source: Original figure from the Human Neuromechanics Laboratory at the University of Michigan.