Design: The Millennium Collection No 10: The Blatchford Intelligent Prosthesis (IP)

So far, more than 200 Millennium objects have been chosen for their excellent design. Each week we examine one

LEGS, UNLIKE arms, are used primarily for mobility so it is much easier to replace a missing leg with a prosthesis than to manufacture an artificial arm with all of an arm's various functions.

I imagine most people think that a false limb is just something practical, to be worn or not, but it is much more than that. A limb is a hugely important part of one's body and nothing can replace it either psychologically or emotionally; a prosthesis is meant to restore self-confidence but, ironically, by emphasising that one ought to look like everyone else it can actually diminish that confidence.

Leg prostheses are practical; legs are important for mobility, so the greater the range of movement and the more natural the operation of a prosthesis the better. Prosthetics are not modern. They have been found in India dating from 3500BC. Herodotus describes a wooden foot being fitted, and artificial arms have been found buried with Egyptian mummies. But the sophistication of prostheses is much more recent. One of the reasons I had always thought having one arm preferable to having one leg was the thought of not being able to run or go for long walks.

Now Blatchford have produced a lightweight Intelligent Prosthesis; the current model automatically adjusts the swing of the knee to match the individual amputee's normal walking speeds, and the model scheduled for 1999 will adjust to modes of locomotion which will also enable the user to walk on rough terrain and descend stairs easily and safely.

After the limb has been professionally fitted and precisely adjusted to the individual's pre-operation mode of walking, a microchip in the prosthesis adjusts the gait automatically and ensures the wearer can walk slowly or swiftly at will. Although the limb uses high technology it is user-friendly in that it is both light and easy to wear, with two easily replaceable batteries which have a life expectancy of up to a year. Those and an annual inspection are all that is needed to keep the artificial limb operating smoothly.

The IP is suitable for most amputees including children aged 12 and over. The main advantages are that as the limb requires far less effort to operate, users waste less energy and no longer need to think about walking bec ause there is no need to consciously kick the leg to ensure full extension.

The revolutionary difference between this and earlier prostheses was that although in the past the way amputees walked was taken into account, the crucial element of different walking speeds was not.

The IP is available on the NHS and is exported all over the world. But it is too expensive for general use and consequently not available to the thousands of landmine victims in the poorer developing countries.

Patient reports have been very positive and the IP has won the 1996 Prince of Wales Award for Innovation, the Queens Award for Technological Achievement