Available online at ScienceDirect. Procedia Manufacturing 2 (2015 )

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1 Available online at ScienceDirect Procedia Manufacturing 2 (2015 ) nd International Materials, Industrial, and Manufacturing Engineering Conference, MIMEC2015, 4-6 February 2015, Bali Indonesia Functional Electrical Stimulation for Foot Drop Injury Based on the Arm Swing Motion S. Ismail a,b*, M.N. Harun a,c, A.H. Omar a,b a Sport Innovation and Technology Centre, Universiti Teknologi Malaysia,81310 Johor Bahru, Malaysia b Faculty of Biosciences & Medical Engineering, Universiti Teknologi Malaysia,81310 Johor Bahru, Malaysia c Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor Bahru, Malaysia Abstract This paper describes the initial concept of functional electrical stimulation (FES) for foot drop injury based on the arm swing motion. The prototype was an effort to improve the existing FES available in the market that are facing problems due to the error of detecting a step intention, especially in the acute stage of foot drop injury due to stroke. The development of the device was divided into two main phases: hardware design and testing. Hardware phases consisted of the design of the electronic structure and parts such as accelerometer ADXL335 and programming for PIC18F4520. Initial testing was conducted with six normal subjects and one foot drop patient subject in order to identify the functional performance of the prototype. The result shows that the gait sensing placement of the prototype FES was successfully controlled by using the arm swing movement The The Authors. Authors. Published Published by by Elsevier Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license ( Selection and Peer-review under responsibility of the Scientific Committee of MIMEC2015. Selection and Peer-review under responsibility of the Scientific Committee of MIMEC2015 Keywords: Functional Electrical Stimulation; Foot Drop; Gait; Rehabilitation; Accelerometer 1. Introduction Foot drop is defined as a deficit in turning the ankle and toes upward during walking, known as dorsiflexion of the ankle joint [1]. Physiologically, the deep fibular and peroneal nerve in the leg innervates the anterior compartment of the leg play important roles in dorsiflexion of the ankle joint [2]. Some serious injury or lesion that would damage this nerve leads to the inability for the leg to dorsiflex the foot, therefore leading to foot drop [3]. Foot Drop injury occur due to neurologic, muscular or anatomic in origins, and often significantly overlap [4]. * Corresponding I.Saharudin Tel.: ; fax: address: saharudin@biomedical.utm.my The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( Selection and Peer-review under responsibility of the Scientific Committee of MIMEC2015 doi: /j.promfg

2 S. Ismail et al. / Procedia Manufacturing 2 ( 2015 ) The dorsiflexion of the ankle (raising the foot) and the plantar flexion (lowering the foot are important in the gait cycle. The muscles that are involved in dorsiflexion of the ankle during gait cycle are the tibialis anterior and the extensor digitorum longus [5]. Without the motor dorsiflexion action, the patients tend to drag their feet during walking. The patient have a high risks of acquiring injuries due to the behaviour of the toes catching any cluttering objects on the floor. This condition may lead to falling and fall related fractures, especially for the elderly [6]. In the long term, this condition would cause a lot of pain to the lower limb joints. Therefore, a patient with a foot drop injury are recommended to wear or use mobility assistive devices such as an ankle foot orthosis and FES. Today, FES is the main choice to help foot drop patient walk. There are many FES for foot drop available in the market, varying from removable to surgical FES system [7]. Conventional Functional Electric Stimulation (FES) systems available in the market basically consist of electronic stimulators, sensors and stimulation electrodes. FES works on the principle of delivery of the electric impulses and mimick the natural flow of an electric signal in non-impaired structures. Amazingly, our tissues are an ionic conductor with an impedance between 10 to 100 Ώ, which allows an artificial electrical stimulation waveform to excitate a certain group of muscles for movement [8].The WalkAide2 and NessL3000 are two common removable FES brands widely used by foot drop injury patients. For both FES, the gait sensor is placed at the affected foot to sense the foot position and estimate the right moment to deliver the electrical stimulation [9]. This method has a weakness, especially in the early and acute stage of hospitalization, most patients lose control over the affected limb. A small erratic motion produced by the affected limb could produce an error for step intention [10]. Thus, a new sensor placement would be helpful to improve the conventional FES. The first objective of this research is to design the FES system based on normal human arm swing motion sensing using accelerometer. The underpinning theory is based on the act of synchronization of human arm swing and leg motion during normal walking [11]. The second objective of this experiment is to analyse the gait performance of the foot drop injury patients using the prototype with Siliconcoach motion analysis software. 2. Methods 2.1 Hardware and Electronic Design Hardware Design: The control mechanism system comprises of three main units: the brace sensor unit, the calf unit and the standard available Electronic Muscle Stimulator (EMS) unit. The wrist unit is attached to the subject s wrist [Figure 1 (a)] and wirelessly communicates with the relay unit located around the subject s calf [Figure 1 (b)]. The system in this experiment works with commercial EMS LG-7500 widely available in the market by using a docking concept. The parts were cased together in a small scale box and neoprene fabric was used in fabricating the hardware. The weight and easy to wear factor should be considered when designing the prototype casing. Velcro is used to attach the device to the subject s wrist and subject s calf. (a) (b) Fig. 1. (a) The brace sensor unit (b) The calf unit and EMS Electronic Design: The main components of the brace sensor unit consist of the accelerometer, PIC 18F4520 and Xbee. The calf unit consists of XBee receiver, PC 18F4520 and a relay. The relay is connected to the EMS output

3 492 S. Ismail et al. / Procedia Manufacturing 2 ( 2015 ) unit. The EMS is set to a certain setting suitable with the subjects to stimulate the ankle dorsiflexion. A setting of microseconds duration, with a frequency of Hz and a maximum peak current of 90mA, was applied through the conductive electrode. Figure 2 shows the complete block diagram for the operational implementation of the prototype. The prototype works on the normal principle of walking. During walking, human arms is swing involuntarily. The system is then switched on based on the swing forward and backward motions of the arm in sequence with the swing phase of the foot gait cycle, where the ankle joint should be in the dorsiflex position after the toe off period. BRACE SENSOR UNIT ADXL335 PIC18F4520 XBEE transmit CALF UNIT XBEE receiver PIC18F4520 Relay Electrode EMS Fig. 2. The Functional Operational Block Diagram 2.2 Prototype Operation EMS is applied to the subject with electrodes fixed along the Paroneal nerve innervations. The initial setting and calibration were done manually by the therapist to relocate the suitable electrode placement. When the user was ready, subjects were asked to swing their arms forward. The system was capable of sensing the forward motion with the accelerometer produced by the arm swing motion. The brace sensor unit then wirelessly communicate with the calf unit which contained a relay. The actual electrical stimulation current flow coming to the relay unit flowed towards the electrode when the user swing the arm forward, signaling presence of motion. The relay is then switched on up to 3 seconds based on the specific setting set by the therapist. 2.3 Volunteer Six healthy participants, 3 men and 3 women, ranging from 24 to 29 years of age, participated. These subjects have had no history of musculoskeletal impairment, neurological disorder, cardiac or other pulmonary pathologies, and they are well conscious of the experimental instructions. The subjects sat in a hanging position to free the ankle joint from touching the floor. First, the participant was given 10 minutes to familiarize with the prototype and hear an explanation of the experiment protocol. The participant was asked to swing his/her arms and the dorsiflexion movements were recorded using a video camera. The recorded video was analyzed using Siliconcoach software. In the second experiment, one subject patient with foot-drop due to stroke in sub-acute phase was willing to enroll in this pilot study. The subject was asked to stay on a line marked on the floor, and after an acoustic signal, to walk forward for 8 m on a single line, with aid if needed. In the first session, the subject walked without FES and after 30

4 S. Ismail et al. / Procedia Manufacturing 2 ( 2015 ) minutes familiarized with FES. The subject then walked with FES. The session was recorded using a video camera in the sagittal and frontal plane. The post analysis assessment was done using Siliconcoach software. 3. Results Figure 3 and Table1 shows the results of the experiment which indicated the presence of ankle joint dorsiflexion when subjects swung their arms forward for all six subjects during stimulation. The plantar flexion is the initial position without the EMS stimulation. The dorsiflexion movement is the missing action in foot drop injury patients. Table 1: Ankle joint plantar flexion and dorsiflexion result of six subjects Range of Motion ( o ) Subject A Subject B Subject C Subject D Subject E Subject F Plantar Flexion Dorsiflexion (a) (b) Fig. 3. (a) Plantar flexion of the ankle joint (b) Dorsiflexion of the ankle joint One males patient subject, of age 69, with a history of left side stroke and a history of onset for 195 days had been recruited for this experiment. In this experiment, the subject did not wear any walking aid at home. The recorded video was analysed using Siliconcoach software. Table 2 shows the result for the comparison between walking with and without the prototype. Table 2: Comparison between Walking With FES and Without FES for Patient Subject Velocity (m/min) Cadence (step/min) Step length (cm) Ankle Angle at toe off(degree) Peak Ankle Angle during swing (Degree) Without FES (plantarflexion) 3 (plantarflexion) With FES (plantarflexion) 4 (dorsiflexion) 4. Discussion and Future Work Conventional FES tends to use the affected legs as a reference for gait sensing. This work suggests using a referral sensor around the wrist, matching the motion of the arm swing and the footsteps. This work is an initial

5 494 S. Ismail et al. / Procedia Manufacturing 2 ( 2015 ) concept of changes that could be done with the conventional FES. The first experiment showed that swinging the arms forward in a marching-like manner when walking normally can be used as a control switch. There are lots of improvements and studies to do in improving this prototype such as the fundamental correlation study of human arm swing and gait cycle. The speed of the arm swing and the electrical stimulation circuit is suitable for this system. The result from the pilot test showed that the patient walked better using the prototype compared to walking without FES. Walking with the prototype provided advantages as it had improved the subject walking speed (0.13 m/s), increased the number of cadence (7.96 step/min) and increased7 cm of the step length. Thus, we hypothesized that an increase in walking speed, cadence, and step length is an early indication that arm swing was able to be used as a gait referral axis. During the toe off period, the foot provided a significant 10 o difference between ranges of motion, which was enough to provide a foot clearance during walking. A foot clearance is important not only to prevent the patient from falling but also to prepare the foot for heel strike in the early stance phase [12]. The peak ankle angle difference with a 7 o range of motion during the swing phase, changing from plantar flexi position to dorsiflexion position indicated a positive improvement over the foot position during the swing phase. As a result, the changes had helped to reduce the user s energy consumption during walking [13]. 5. Conclusion The built FES for foot drop injury based on the arm swing motion functioned successfully and provided an alternative for gait sensing or referral position to predict the gait step intention. However, further studies and improvements should be done so that the device could be used clinically in the rehabilitation field. Acknowledgements Authors would like to convey a deepest acknowledgement to the Ministry of Education Malaysia for providing the research grant 4L629 References [1] Stewart, J. D. (2008). Foot drop: where, why and what to do?. Practical neurology, 8(3), [2] Sheffler, L. R., Hennessey, M. T., Naples, G. G., & Chae, J. (2006). Peroneal nerve stimulation versus an ankle foot orthosis for correction of footdrop in stroke: impact on functional ambulation. Neurorehabilitation and neural repair, 20(3), [3] Eskandary, H., Hamzei, A., & Yasamy, M. T. (1995). Foot drop following brain lesion. Surgical neurology, 43(1), [4] Stein, R. B., Everaert, D. G., Thompson, A. K., Chong, S. L., Whittaker, M., Robertson, J., & Kuether, G. (2010). Long-term therapeutic and orthotic effects of a foot drop stimulator on walking performance in progressive and nonprogressive neurological disorders. Neurorehabilitation and neural repair, 24(2), [5] Marsh, E., Sale, D., McComas, A. J., & Quinlan, J. (1981). Influence of joint position on ankle dorsiflexion in humans. Journal of Applied Physiology, 51(1), [6] Rubenstein, L. Z. (2006). Falls in older people: epidemiology, risk factors and strategies for prevention. Age and ageing, 35(suppl 2), ii37-ii41. [7] Kottink, A. I., Oostendorp, L. J., Buurke, J. H., Nene, A. V., Hermens, H. J., & IJzerman, M. J. (2004). The orthotic effect of functional electrical stimulation on the improvement of walking in stroke patients with a dropped foot: a systematic review. Artificial organs, 28(6), [8] Lynch, C. L., & Popovic, M. R. (2008). Functional electrical stimulation. Control Systems, IEEE, 28(2), [9] Lyons, G. M., Sinkjær, T., Burridge, J. H., & Wilcox, D. J. (2002). A review of portable FES-based neural orthoses for the correction of drop foot. Neural Systems and Rehabilitation Engineering, IEEE Transactions on, 10(4), [10] Dai, R., Stein, R. B., Andrews, B. J., James, K. B., & Wieler, M. (1996). Application of tilt sensors in functional electrical stimulation. Rehabilitation Engineering, IEEE Transactions on, 4(2), [11] Ballesteros, M. L. F., Buchthal, F., & Rosenfalck, P. (1965). The pattern of muscular activity during the arm swing of natural walking. Acta Physiologica Scandinavica, 63(3), [12] Leung, J. and Moseley, A., Impact of ankle-foot orthoses on gait and leg muscle activity in adults with hemiplegia: systematic literature review. Phys Ther, [13] Sabut, S. K., Lenka, P. K., Kumar, R., & Mahadevappa, M. (2010). Effect of functional electrical stimulation on the effort and walking speed, surface electromyography activity, and metabolic responses in stroke subjects. Journal of Electromyography and Kinesiology, 20(6),