Doctors told the TV mogul he was “very lucky” not to have suffered paralysing injuries.
Cowell is thought to have missed damaging his spinal cord – part of the body’s central nervous system – by a centimetre.
The source said: “It was a really, really bad fall – but he’s very lucky to have escaped with the injuries he has.
“Had he damaged the spinal cord he could have been looking at life in a wheelchair, but thanks to the doctors he is hopeful of making a full recovery.”
Hollywood’s Christopher Reeve spent the final decade of his life in a wheelchair after damaging his spinal cord in a fall from a horse.
Cowell was taken to Providence Saint John’s hospital in Santa Monica, a short drive from his £18 million ($A32 million) beachside property in Malibu.
Lauren, 43, joined him at the medical centre on Saturday afternoon. He was later taken into theatre for an operation by some of California’s best surgeons.
He was in theatre for more than five hours, under general anaesthetic, as doctors inserted a series of screws and a metal rod to stabilise his spine.
Cowell was awake today talking to medical staff and members of his team by phone.
He now faces an anxious wait to learn the extent of the damage – and almost certainly faces a lengthy stay in hospital.
Those close to him hope he will suffer no lasting effects but say it could take “several weeks” before they know for sure.
“He’s only just out of surgery and feeling very groggy but is awake and upbeat,” a source added.
“Everyone hopes he will make a full recovery but they don’t want to count their chickens just yet. Ultimately he has had a very, very serious accident.
“He’s lucky to be even in the state he is in with a metal rod in his back and multiple breaks.
“It’ll be several weeks for the bruising and swelling to go down and then we’ll know how serious the lasting effects could be.”
A spokesman for The X Factor and Britain’s Got Talent boss said: “Simon has broken his back in a number of places in a fall from his bike while testing a new electric bike in the courtyard of his home in Malibu with his family.
“He was taken to hospital where they operated overnight. He’s under observation and is doing fine.”
Cowell, a workaholic who was discussing business from his hospital bed after coming around from the anaesthetic, is now likely to miss a string of TV commitments – not least AGT.
Insiders say he optimistically hopes to be well enough to return for the end of the new AGT series, in late September.
The America’s Got Talent final is scheduled for September 23 with Cowell planning to fly home the next day so he can also be at the final Britain’s Got Talent.
This articleoriginally appeared on The Sunand was reproduced with permission