Russian freestyle ski federation spokesman Mikhail Verzeba said Komissarova fractured the 12th dorsal vertebrae in her lower-middle back and was taken to a hospital near the Rosa Khutor Extreme Park for emergency surgery.
"The operation is over ... it's been successful," Verzeba said.
The International Olympic Committee was monitoring the situation. President Thomas Bach said, "Our thoughts are with the athlete and we wish her a full and speedy recovery."
The Russian presidential website said Vladimir Putin visited Komissarova Saturday night in the hospital where she underwent surgery.
Medical staff briefed Putin on the surgery and further treatment and the president "wished her a speedy recovery," the statement said.
Putin also called the skier's worried father and told him "doctors will do everything possible for her recovery."
The statement gave no update on Komissarova's condition.
The national freestyle ski federation issued a statement after the surgery saying a team of specialists inserted a metal implant in Komissarova's spine.
The federation said Komissarova was conscious, and described her condition as "grave" but stable, adding that it was likely she'd need further surgery within weeks.
The 23-year-old Komissarova was practicing for next Friday's contest on a sunny morning on the 1,200-meter course, which has nine banked turns and 25 jumps.
In the main competition, four skiers race against each other, with the top two advancing through heats until the final.
Normally during practice runs, skiers are on the course themselves, or travelling down the mountain in loosely packed bunches.
"The course is difficult. It's of the highest possible level of complexity, there is nothing simple about it," Verzeba said. "However, this all is irrelevant now, she got injured, and the rest does not matter."
Jenny Wiedeke, spokeswoman for the International Ski Federation, said the accident occurred on a series of jumps near the top of the course and that Komissarova fell while exiting the third jump.
She was taken by sled to the medical services tent, and from there to the hospital. Team doctors decided to do the surgery immediately instead of transporting Komissarova down to Sochi.
Komissarova is ranked 33rd in the current World Cup standings and recovered from a leg injury last year to qualify for the Olympics. Her best World Cup finish was a second place at a race in Switzerland in 2012. At the same event, Canadian skicross racer Nik Zoricic suffered fatal head injuries in a crash near the final jump of a heat in the men's race.
"Nik's death wasn't anything that happened with contact," American racer John Teller said. "But we all understand how dangerous it is."
Teller said the biggest concern for any skicross racer comes during the racing part, not training or qualifications, which are individual runs down the mountain.
He said most of the competitors had been complimentary of the course setup for the Sochi Games but labeled it a "bigger course."
"It's like a North American style course," he said. "We race skicross all year long in Europe. They tend to be smaller courses. I feel like this course is more of an X Games style of course."
Several athletes have been injured during the games, including a Russian ski jumper who broke his ribs after landing awkwardly in a training accident, and an ice worker at the sliding venue broke both legs when he was hit by a sled before a practice run on Thursday.
Associated Press writer Varya Kudryavtseva and AP Sports Writers Will Graves, Stephen Wilson and Graham Dunbar contributed to this report.
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