Russian freestyle skier Maria Komissarova during a night training session for the 2014 Sochi Winter Olympics at the extreme park in Rosa Khutor, Russia, on Feb. 2. Reuters 
 
 SOCHI, Russia—A Russian skier broke her back and dislocated a vertebra during a practice session on the Olympic freestyle course here Saturday, landing her in a 6.5-hour emergency surgery that has stabilized her condition. 
 
 Maria Komissarova, a 23-year-old from St. Petersburg, was training for a Feb. 21 competition in ski cross, a freestyle event added to the Games in 2010 in which skiers race down a mountain while negotiating artificial obstacles including big-air jumps and rollers. 
 
 Komissarova failed to clear an obstacle during the practice session Saturday morning and crashed, breaking her T12 vertebra, according to the Freestyle Federation of Russia, which said her prognosis wouldn't become clear for three to four days. 
 
 Mikhail Verzhba, a spokesman for the association, described the injury as a fracture with a dislocation. Komissarova remains in serious but stable condition. 
 
 Verzhba confirmed through a translator that Russian President Vladimir Putin visited Komissarova in the hospital Saturday night. The translator said Komissarova was conscious and spoke with the president. 
 
 Doctors immediately rushed to assist Komissarova on the course of the Rosa Khutor Extreme Park after the incident and quickly decided she would need to undergo surgery immediately at the newly built hospital in Sochi's Krasnaya Polyana district. Komissarova couldn't be transferred to a hospital in Moscow or abroad because of the emergency nature of the surgery, Verzhba said. 
 
 The skier remained conscious after the injury and before entering surgery, where doctors reconstructed her vertebra and inserted a metal implant. She will remain in Sochi until doctors can move her to a special hospital in Moscow or abroad for further operation, the Federation said in a news release. 
 
 "It's a very dangerous discipline," Verzhba said. He said it is unclear why exactly Komissarova crashed. Such accidents are common in ski cross and other freestyle sports, he said. Competitors in ski cross take serious air off of massive jumps while speeding down the course, making it a particularly dangerous pursuit. 
 
 As is standard, the ski-cross course was inspected Saturday, an official training day, where all athletes and coaches were present. There were no major complaints about the course, according to Tom Kelly, a spokesman for the U.S. Ski and Snowboard Association, whose coach, John Teller was there. 
 
 Komissarova has avoided the most negative outcome, which would be damage to her spinal cord, her coach, Vladimir Baryshnikov, told the Russian sports newspaper Sovetsky Sport. 
 
 Before the surgery had concluded on Saturday, Verzhba said he didn't know the extent to which Komissarova's spine had been damaged during the accident and was waiting to hear from doctors. He says other people with similar injuries have recovered fully. 
 
 "We are hoping for a recovery back to health," he said, though he warned the final prognosis remains unclear. Komissarova won't compete in the Sochi Games. 
 
 The Russian skier finished second in the ski cross World Cup in Grindelwald, Switzerland, in 2012. It was the same competition where Canadian ski-cross competitor Nik Zoricic died after flying off the side of a jump on the course and smashing into the safety net. Canadian freestyle skier Sarah Burke, who excelled at halfpipe skiing and successfully pushed for its inclusion in the Olympics for the first time this year, died in a training accident in the U.S. the same year. 
 
 Extreme sports including freestyle skiing and snowboarding are among the newest and most dangerous Winter Olympic disciplines. "These are the sports that have had more injuries in recent years," said Bill Mallon, an Olympic historian and orthopedic surgeon based in the U.S. 
 
 Mallon said a dislocation at the T12 vertebra, such as the one suffered by Komissarova, could cause some paralysis, but he said the prognosis depends on the extent of damage to the spinal cord. He said it is unclear whether any nerve damage would be permanent. 
 
 Komissarova currently is receiving medical care at City Hospital No. 8, a facility near the Olympic venues in Sochi's Krasnaya Polyana mountain district. Organizers overhauled and completely rebuilt the hospital ahead of the Games, installing an array of foreign medical equipment to prepare for any serious Olympics-related injuries. 
 
 Russia's Freestyle Federation said it received many calls from "friends and completely unknown people offering all sorts of help." 
 
 "That included offers to organize a charter for the athlete's delivery to any point in the world and money to pay for treatment," the Federation said in a statement. "We thank everyone for their participation and sympathy." 
 
 Write to Paul Sonne at paul.sonne@wsj.com ||||| Story highlights Maria Komissarova is on a ventilator, Russian TV reports 
 
 Komissarova broke her back during training 
 
 The decision was made to operate immediately 
 
 She was training for the ski-cross competition 
 
 Russian freestyle skier Maria Komissarova has undergone more than six hours of surgery after breaking her back during a training run at the Winter Games in Sochi, the Russian Freestyle Federation spokesman said Saturday. 
 
 Komissarova, 23, fractured a vertebra and dislocated her spine when she crashed at the PSX Olympic skicross venue at Rosa Kuhtor, federation spokesman Mikhail Vezhba told the state-run RIA Novosti news agency. 
 
 "The operation lasted 6½ hours, and it was successful," Vezhba said. "We'll know more about the details later." 
 
 A source close to the situation earlier told the Russian news agency that Komissarova's condition was too serious to transfer her to Moscow. 
 
 The skier was reportedly in "unbearable" pain when she was rushed to the hospital, the news agency reported. 
 
 Komissarova placed second in a World Cup event in 2012 but was not considered a medal contender in Sochi. She injured her leg last year, requiring surgery and keeping her off the slopes for almost six months. 
 
 Russian President Vladimir Putin visited with Komissarova in the hospital, news channel Russia-24 reported. 
 
 Footage showed Putin meeting with the skier, who was on a ventilator, in the hospital. He patted her head as he spoke. ||||| ROSA KHUTOR, Russia, February 15 (R-Sport) – Doctors have performed a successful 6 1/2-hour operation on a Russian freestyle skier who suffered a broken back in a training crash in the mountains above Sochi, the Russian Freestyle Federation spokesman told R-Sport on Saturday. 
 
 Skicross racer Maria Komissarova sustained the injury while training Saturday morning at the PSX Olympic skicross venue at Rosa Khutor Extreme Park, the federation said. 
 
 She was rushed to Krasnaya Polyanskaya Hospital No. 8, where the 23-year-old was immediately operated on. The diagnosis was a fractured and dislocated spine, officials said. 
 
 "The operation lasted 6 1/2 hours, and it was successful," Mikhail Vezhba, the federation's spokesman told R-Sport. "We'll know more about the details later." 
 
 A source close to the situation earlier told R-Sport that Komissarova's condition was too grave to transfer her to Moscow. 
 
 Russian President Vladimir Putin's spokesman said Putin had "decided to visit" Komissarova, who he said was already conscious. 
 
 Komissarova's best career result came with second place at a World Cup event in 2012, but she was not expected to be a medal contender in the women's ski cross competition Friday. The federation has not commented on the nature of the injury other than to say it is "serious" and that Komissarova is ruled out of competition. 
 
 So far in the February 7-23 Sochi Olympics, serious injuries have been rare. A track worker broke both legs when hit by a non-competition bobsled Thursday, and a Russian ski jumper broke two ribs in a training crash Wednesday. 
 
 On Tuesday, Canadian slopestyle skier Yuki Tsubota suffered a broken jaw when her own knee struck her in the face during a crash in the final of her competition. 
 
 Updated with Putin’s plan to visit Komissarova.
– After she broke her back, Olympic skier Maria Komissarova of Russia had "successful" surgery, a rep for the Russian Freestyle Federation tells RIA Novosti. Now, she is in stable condition, the Wall Street Journal reports. The good news is that the accident didn't damage her spinal cord, her coach says. Surgeons rebuilt one of Komissarova's vertebrae; she also received a metal implant, the Journal reports, noting that she was conscious following the accident. Now she's due for a hospital visit from Vladimir Putin, CNN reports. As for this year's Games, we won't be seeing her on the slopes.