A pioneering surgery to repair a large gap in her spine using bone taken from her legs was undertaken on a five-year old girl from Walsall in the West Midlands.
Before the operation, Rosie Davies was "basically a timebomb," her family said.
Missing bones in her spine meant her upper body weight was unsupported and her inner organs were being crushed.
The lifesaving surgery came at the cost of her lower legs, which she had always been unable to move, the BBC reported.
Rosie was born with a very rare disorder called spinal segmental dysgenesis.
Five bones which made up part of her spine were missing, leaving a 10cm gap in her backbone. Her legs were also contorted up against her belly and she had very little feeling in them.
She was slowly running out of space in her chest - and running out of time. Eventually the internal crush would have led to Davies' organs failing, which would have killed her.
In her last scan before the operation there was evidence of her kidneys being crushed.
Davies' legs were amputated from the knee down and a section of bone was taken to bridge the gap in her spine.
Two metal rods were then bolted to the upper spine and the hips to provide extra support.
The operation at Birmingham Children's Hospital took 13 hours.
Her dad Scott said: "Before she was basically a timebomb - we never knew how long it would take to go off, we never knew how long we actually had with her."
"Since having the op she's now had her life expectancy increased to that of a normal child," he said.
Since the surgery there have been early signs of sensation returning to her legs, which means it may be possible for Rosie to one day walk with prosthetic legs.