The accident occurred Saturday night just before Canadian teen idol Justin Bieber was to appear on the show, prompting him to say on his Twitter account: "Please pray for Samuel Koch & his family as we wait and hope for his health and safety."
Koch's stunt may have gone terribly wrong because the special shoes he was wearing for the jump, featuring a suspension system, malfunctioned.
Andreas Rentz, Getty Images
Samuel Koch jumps over the third car of five cars before his accident Saturday night on the German game show "Wetten, Dass?" (I Bet That?).
Broadcaster ZDF said the accident by the 23-year-old prompted it to cancel the live broadcast of the "Wetten, Dass?" (I Bet That?), which had an audience of about 10 million people, according to German media.
Koch suffered multiple back injuries and fractures, underwent surgery Sunday, and his condition was initially life threatening, the German news agency DPAD quoted Duesseldorf hospital Dr. Wolfgang Raab as saying.
But it remained unclear if or when Koch would fully recover since "he is in an extremely critical stage," Raab told journalists.
Bieber, a 16-year-old singer, added on Twitter that he felt sorry for not being able to perform in Germany, but "some things are more important than putting on a show. We will be back I promise."
The TV show also was to include a gig by singer Robbie Williams, and Phil Collins, Cher or actress Cameron Diaz were among the guests, according to the broadcaster's website.
"Wetten, Dass?" has been on TV for nearly 30 years and is one of Germany's most successful shows.