* Russian skicross racer injures back, has surgery
* Putin visits her in hospital, calls father (Updates with Putin meeting skier, call to father)
By Ossian Shine and Alexei Anishchuk
SOCHI, Russia, Feb 15 (Reuters) - Russian Olympic skicross racer Maria Komissarova underwent six-and-a-half hours of spinal surgery on Saturday after breaking her back in a Sochi 2014 training crash.
The 23-year-old had a metal implant inserted and surgeons said they would not know how successful the operation had been for three or four days.
Her condition was serious but she was in a stable condition, the Russia Freestyle Skiing Federation said, adding that she was likely to be taken to a Moscow hospital or go abroad for treatment when it was possible to move her.
Her mother, Maria, was due to arrive in Sochi on Sunday.
President Vladimir Putin visited Komissarova on Saturday evening to wish her a rapid recovery and doctors briefed him on the surgery, the federation said.
Komissarova told Putin her father was extremely worried, so the president called him to offer his assurances that the doctors were doing their best to help her make a full recovery, it added.
The International Olympic Committee (IOC) said in a statement: "Our thoughts are with the athlete and the family".
Komissarova suffered the injury during training at the PSX Olympic skicross venue at Rosa Khutor Extreme Park. She was taken to Krasnaya Polyana Hospital Number 8, which was specially built for the Olympics, where doctors decided to operate.
"During one of her training runs, Maria injured her spine," the freestyle team's head of press Mikhail Verzhba said. "It is a serious injury."
Verzhba said the athlete had received medical assistance almost immediately.
The 1,200-metre skicross course at Extreme Park is a medium-pitch slope which features cambered turns, gap jumps, drops and flat sections.
The skiers race down the course in groups of four in a test of speed, skill and aggression with the first across the line the winner.
"You will never be able to exclude any kind of risk," IOC President Thomas Bach said.
"We feel very sorry for the athlete. We hope that the operation will be successful and that she will be back."
Bach said that, as he understood it, the accident had nothing to do with conditions at the Extreme Park.
"The first information is that it was nothing to do with the infrastructure, the snow conditions. It was in a training session and this unfortunate incident happened.
"Our thoughts are with the athlete."
Komissarova's accident comes two days after a track worker at the Feb. 7-23 Olympics was struck by a bobsleigh, suffering two broken legs.
The worker was hit by the "forerunner", which is sent down the track ahead of the official competitors to check for safety.
Russian ski jumper Maksim Maksimochkin was taken away on a stretcher on Wednesday night after crashing during practice on the large hill. He spent the night in hospital and was diagnosed with two fractured ribs.
On the slopes, Liechtenstein's medal hope Tina Weirather missed the downhill and super-G after suffering a heavy bruise when she fell in downhill training on Sunday. She was not entered in the combined.
Slovenia's Rok Perko broke his nose in a fall in men's downhill training, while French skier Brice Roger tore his anterior cruciate ligaments in the same training session and is out for six months.
Canadian Marie-Michele Gagnon dislocated her shoulder after straddling a gate in the super-combined on Monday. She returned for the super-G today but skied out.
In figure skating, Jeremy Abbott slammed into the barriers after falling on his opening jump. He lay grimacing in pain for almost a minute but then finished his programme.
Komissarova's crash, though, marks the first major athlete accident of the Sochi Games.
Four years ago, a tragic pall hung over the Winter Olympics in Vancouver when Georgian luger Nodar Kumaritashvili died in a crash during a training run on the day of the opening ceremony. (Additional reporting by Nick Mulvenney and Alexei Anishchuk in Sochi, Alan Baldwin and Dmitry Rogovitskiy in Rosa Khutor; Editing by Peter Rutherford)