A teenage girl has become the first to receive a revolutionary implant that could spare her years of painful surgery.
The device will help Kat's leg grow
Kat Reid, 13, lost a large section of bone from her leg after she was diagnosed with osteosarcoma, a cancer which attacks bone.
Most young patients who undergo such an operation need to have an implant to support the remaining bone - but if they are still growing, the implant has to grow too, meaning that extra procedures are needed regularly to extend it little by little.
The £9,000 implant fitted in Kat's leg should remove the need for these.
It can be operated from outside the body - Kat simply has to insert her leg into an electromagnetic box which spins a magnetic gearbox inside the device.
As this rotates at 3,000 revolutions a minute, the implant extends fraction by fraction.
Kat, from Wimbledon in London, is delighted with the results.
She told the BBC: "It's amazing. It's such a relief.
"At first I was a bit nervous, but actually, I didn't feel a thing.
Kat is delighted with the results
"Some people call me a guinea pig - but I'd rather be the first person to have the new implant than the last person to get the old one, as it's so much better."
She says her walking is almost back to normal, and she has returned to school to take up her studies again.
The procedure to lengthen her leg should take just 15 minutes, and can be carried out in a clinic rather than an operating theatre.
Consultant surgeon Mr Tim Briggs, from the Royal National Orthopaedic Hospital in Stanmore, London, said: "This is a huge advance - Kat was the first time we'd tried it on a human.
"It should become the norm for prosthetics for the suitable age group.
A simple procedure activates the implant
"It should also be beneficial for people who have one leg shorter than the other, as well as those with curvature of the spine."