Advanced prosthetics go for gold

Tom Shelley reports on how technical advances in artificial limbs are likely to prove to be winners in the Paralympics with subsequent benefits to be reaped by all



Chas. A. Blatchford and Sons, the UK's leader in high technology artificial legs and feet, is aiming to develop new products specifically aimed at securing gold for British athletes in the 2012 Paralympics, which will run alongside the main Olympic events for the non disabled.

Just as motor sport acts as a spur and test bed for the development of new concepts and technologies for motor vehicles, disabled sport acts as a spur and test bed for the development of prosthetics.

While the initial goal is to have winning athletes in the Paralympics equipped with the company's prostheses, the ultimate goal is to develop products that can improve quality of life for leg amputees, of whom there are presently about 1 million across the globe.

Blatchford's intelligent self adapting knee joint has already been the subject of an article in Eureka in September 2001, which explained how it used microprocessor based control of a stepping motor to vary hydraulic damping. The latest innovative product to come from the Blatchford Stable, however, relies not on microprocessor based electronics, but on innovative use of springs made of advanced materials in the 'Elite' 'All Terrain Foot'.

Product Development manager Saeed Zahedi and Design Manager Graham Harris explained that this uses three carbon fibre leaf springs to store energy from the user's downward foot stroke, absorbing shock and subsequently releasing it to give forward power. One spring is in the heel and two are in what would in a non-amputee be the rest of the foot, one on each side. As well as absorbing shock and storing energy, the toe springs also provide ground conformity. In order to function with maximum efficiency, these have a shape that thins but widens towards the toes and then narrows again.

We were told that a lot of development work went into the design, partly finite element analysis using the FEA in I-DEAS Master Series, and partly by iteration - making product, testing it, modifying the design and making a new version. An important part of the design process was coming up with a product that could easily be made in different configurations to meet the needs of amputees of different weights and with different life styles. This has required the development of nine different spring sets to cover amputee weights from 60kg to 150kg with variations to accommodate feet all the way from size 22 to size 30. 1

To reduce the number of moulds required, the company has developed a novel manufacturing process which does not require use of large numbers of totally enclosing moulds, but which allows different profile springs to be manufactured using a very small number of tools.

For the Paralympics, Blatchford intends to develop designs of the feet and knee joints that can be optimised for each event. Some events, such as cycling, require maximising power output beneath the instep, while others require athletes to spend much of their time on their toes. The knee joints will not be based on the electronically adaptive knees, but on the manually adjustable 'Mercury Junior' units. The name 'Junior' is not meant to imply that these are made for children, but that they are smaller ins size than other products, with a stronger carbon fibre box section and needle roller bearings. For the Paralympics, it is intended to further develop the product to take higher loads.

But the ultimate purpose is to use the opportunity to develop better products for general usage, including, possibly a completely integrated foot/ankle/knee artificial leg. We have not mentioned ankles so far, but these are also an essential part of legs, both natural and artificial, and the company has developed a new 'Multiflex' ankle, with a ball and socket joint plus constraint provided by a stiff rubber ring. From September 2005, this is to be integrated into the feet.

Ultimately, Saeed Zahedi told us that his ultimate goal is to move Blatchford to mass manufacture that can deliver best possible technology solutions to all the amputees across the world who can benefit from it2. This will mean going from a world class manufacturing operation to a world scale manufacturing operation, but still with design and development based in England. "Innovation is at the heart of Blatchford", Saeed Zahedi explained. "Our main competitor in the UK imports from China, but their products have no innovation in them." One of the results of more active usage by customers, is that artificial feet, for example, last typically only four years, as opposed to ten years previously. And when a product comes to the end of its serviceable life, as in the case with mobile phones and virtually everything else, the customers want the latest technology that is available.

Zahedi, however, can see a time when his company partners with Chinese manufacturing to conquer world markets whilst keeping complex and high added value manufacturing in Basingstoke3. Apart from anything else, in order to capture the larger world market, something has to be done to bring down manufacturing costs, which in the case of the foot, are hundreds of pounds, translating to an end sale price fitted to a patient of nearly a thousand pounds. Zahedi is aware, however, that there will be many challenges to overcome, both design, technical, organisational and people based, before this happens. Sadly, with the continued use of land mines, and growth of motor vehicle ownership coupled with longer life spans, there is likely to be no likely shortage of end customers.

Chas. A. Blatchford and Sons

Eureka says: Technical advances in artificial limbs are of benefit to all amputees, and if the Paralympics provide a spur to improve them, these could be the biggest benefits to come out of the UK winning the 2012 Olympics.

Pointers

* New prosthetic feet provide additional functionality and ease to use to amputees by making use of latest advances in high technology materials and developing new manufacturing processes

* The new products could well form the basis of transforming a craft manufacturing business into a world size manufacturing one

Author
Tom Shelley

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