Page 53 - ITU KALEIDOSCOPE, ATLANTA 2019

MODULE STRUCTURE FOR FOOT PROSTHETIC AND INTERFACE
STANDARDIZATION

1
Yoshitoshi Murata ; Tomoki Yamato 2
1 Faculty of Software and Information Science, Iwate Prefectural University
2 Solution Strategic Department, DOCOMO Technology, Inc.

ABSTRACT One of the main reasons why the cost of introducing existing
powered prosthetics is too expensive may be that the
Several million people around the world live with limb loss. prosthetic market is not open. A number of manufacturers
Prosthetics are useful to improve their quality of life, and provide them as an integrated device, and the components
some powered prosthetics enable them to walk naturally. are not compatible between different manufacturers.
However, most are too expensive for most amputees to afford.
We propose a module structure for a foot prosthetic and Introducing a module structure to prosthetics and
standardized interfaces between modules to lower the price standardizing the interface between modules will enable the
of powered ones. The prosthetic is battery-powered and price of powered prosthetics to be lower. In this paper, we
controlled by data from sensors built into the heel of a shoe propose a module structure for foot prosthetics with
for a healthy foot. Some modules can be applied to people standardized components.
with walking disabilities. Such standardization can lower the
price of such modules, and many amputees and people with Our paper is outlined as follows. Existing power-assist
walking disabilities, such as hemiplegia, can easily afford prosthetic leg designs are introduced in section 2. The results
them, which can help improve their quality of life. of our research related to the gait of stroke patients are
introduced in section 3. We developed a walking assist shoe
Keywords – Amputee, foot prosthetic, gait assist, walking that has a coil and leaf spring to easily raise the heel. Its
disability structure and effect of raising the heel are introduced in
section 4. Our proposed module structure for a foot
1. INTRODUCTION prosthetic is introduced in section 5. The heel-up spring,
which is one of the modules comprising the foot prosthetic,
As the percentage of elderly people in the world’s population is derived from the results of the walking assist shoe
is increasing [1], the number of functionally impaired people, introduced in section 4. We conclude in section 6.
such as those with cerebrovascular diseases, will also
increase. People with such diseases often have walking 2. EXISTING POWER-ASSIST FOOT
disabilities, which increases their risk of falling and PROSTHETIC
consequently injuring themselves [2]. One main cause of this
is due to their inability to raise their heel and swing their toes In this section, we introduce existing powered foot
up because of muscle weakness [3]. prosthetics. Ottobock in Germany and Ösuur in Iceland
provide such prosthetics to consumers and the
There are nearly 2 million people living with limb loss in the Biomechatronics Group, a research group within MIT Media
United States [4]. Maurice LeBlanc estimated the number of Lab., has also developed some models.
amputees was approximately 10 million in the world, with
30% comprising arm amputees [5]. Therefore, the number of Ottobock provides a power-assist foot prosthetic called “1B1
leg amputees was 7 million. Leg amputees use foot Meridium [6].” Its mechanism is shown in Figure 1. It adopts
prosthetics to improve their quality of life. However, low- a hydraulic pressure mechanism, in which a hydraulic
priced foot prosthetics have rigid ankle parts and no power pressure cylinder pushes and pulls a lever on the toe plate,
drive mechanism, which makes it difficult to raise the heel causing the instep to rise and fall, respectively.
and swing the toes up. Therefore, most users need more
power to move their foot. Powered foot prosthetics enable Össur provides a power-assist foot prosthetic called
users to move their foot easily and walk more naturally. “PROPRIO FOOT [7]” shown in Figure 2. Due to a lack of
®
However, such prosthetics are too expensive for most relevant material on the product's operation, we assume from
amputees. One example is that in Japan it costs more than 2 observations that an air cylinder positioned in the area of the
million yen ($18,000). Achilles' tendon raises and lowers the foot part.

978-92-61-28401-5/CFP1968P-ART @ ITU 2019 – 33 – Kaleidoscope