Stretching a leg - day by day

Amani Khader has had to have a series of operations

Many people have one leg that's longer than the other - most barely notice.

But for some, the difference can be up to 12 inches, meaning they have to rely on wheelchairs, callipers or crutches.

Up to 1,000 people every year - mainly children and infants - have surgery to correct the difference.

BBC News Online looks at how doctors are working to better predict how successful the operation will be - and hears how one little girl has been offered hope by the procedure.

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Amani Khader, like many 12-year-olds, celebrated her birthday by going bowling with her friends.

But her party had to be brought forward - because she was due to be admitted to hospital to have the 13th operation of her life, aimed at making her legs the same length.

It is hoped it will reduce the current difference in the length of her legs, which is more than 12cm.

Amani, from Edinburgh, suffered a congenital hip fracture as a baby, leaving her left leg significantly longer than her right.

It is very difficult living with this problem, especially when people - particularly children - stare at me as if I'm a monster or an alien

Amani Khader, 12

She was put in a hip spica, a special plaster for the legs, hip and pelvis, when she was three days old.

Operations since have lessened the difference in leg length, but aggravated the hip dislocation.

She says it has been difficult: "It is very difficult living with this problem, especially when people - particularly children - stare at me as if I'm a monster or an alien."

In this latest five-hour operation, she was fitted with a state-of-the-art Ilazarov frame from her pelvis to her heel.

By turning the screw on her frame less than half a millimetre every day it is hoped she will lessen the difference in length of her legs.

Research

Although doctors can carry out the leg lengthening procedure using methods, including the Ilazarov frame, there is currently no way of knowing whether a patient is going to benefit.

In addition, the soft tissues can be damaged by the procedure, sometimes permanently.

Amani wants to be an orthopaedic surgeon when she is older

Children's charity Action Research has ploughed £60,000 into a two-year research project at the Universities of Hull and Edinburgh, and University College Medical School, London.

It aims to look into both the causes of limb length discrepancy, and what determines whether a patient is going to benefit from surgery.

Scientists believe tracking the presence of key proteins could help them see if the limb-lengthening is working.

During the process of muscle fibre regeneration, key proteins are produced.

Regrowth

Professor Hamish Simpson, professor of the University of Edinburgh's Musculoskeletal Research Units said: "It is no use, for example, trying to increase a limb by 9cm in one single operation if its been shown that the patient's muscles won't recover after 7cm."

During the operation, the bone is broken -sometimes in several places - and a set of metal wires and screws attached to each end.

These are then attached to a metal frame running parallel to the limb, which is designed to stimulate new bone growth.

The amazing thing is that the body will form new bone, nerves and muscle in between the gaps

Professor Hamish Simpson, University of Edinburgh

Pins on the frame, which act as "gripping" devices allow the patient to make tiny adjustments a few times a day, in which the bone is very slowly separated.

The technique forces the leg to grow, but keeps it stable while the new tissue forms.

Patients can gain up to 2-3cm in length in a month.

Professor Simpson, who cared for Amani, explained: "The amazing thing is that the body will form new bone, nerves and muscle in between the gaps purely in response to this mechanical stimulus."

Amani now swims, dances, plays badminton and rides horses with her friends - and says she wants to be an orthopaedic surgeon when she grows up so that she can help other children with the same condition.

But she may still need further surgery in the future.