Franchitti also fractured two vertebrae in his spine and received a concussion. He had surgery on the ankle Sunday night and remained in the hospital afterward. Franchitti is expected to return to Indianapolis on Wednesday and have a second surgery on his ankle.
"Thank you to everyone for all the well wishes. They mean a lot to me," Franchitti said in a statement from Target Chip Ganassi Racing. " I would also like to send my best to all the fans involved in the accident and hope that everyone is all right."
Thirteen fans and an IndyCar official were injured by debris that flew into the grandstand. Two people were taken to the hospital; Tony Kanaan tweeted a picture of himself and fellow driver Scott Dixon visiting one of the fans and wrote: "Glad to see everybody is ok."
The accident occurred when Franchitti ran into the back of Takuma Sato's car and launched over it and into the fence. Sato appeared to have a problem with his car and was limping toward the finish when Franchitti came up quickly behind him in Turn 5.
The force of the crash tore apart a section of the fence and showered debris into the grandstand, which had a second fence in front of the fans. Franchitti's car ricocheted back onto the track and spun several times before coming to a stop.
IndyCar threw the yellow flag, ending the race under caution, but drivers still had to navigate their way through the wreckage on their way back to pit road. It created a scene reminiscent of Dan Wheldon's fatal 2011 crash at Las Vegas, where competitors also had to drive past Wheldon's car and through the debris.
It was a sobering moment for race winner Will Power, who broke his back in the Las Vegas crash, and for Dixon, Franchitti's teammate. Dixon took control of the IndyCar championship race on Sunday but passed by teammate Franchitti's car and waved in an attempt to get an update on his condition.
Power watched replays of the accident on the big screen, and said the accident reminded him of Las Vegas, where he and Wheldon both sailed into the fence.
"I just saw Dario's car and him sitting in it with a lot of damage, and yes, that's what it reminded me of," said Power. "I hate seeing that. We try to keep these cars on the ground."
The accident ended a weekend that saw Dixon move into the points lead following mechanical failures for Helio Castroneves on consecutive days.
Castroneves came to Houston with a 49-point lead over Dixon. But a gearbox problem Saturday when Dixon won allowed Dixon to pull within eight points. Then his gearbox broke on Sunday, and Dixon now has a 25-point lead in the standings and needs only to finish fifth or better in the Oct. 19 finale in California to win his third IndyCar title.
"It's still going to come down to the wire," he said. "It's still going to be the last lap, last corner kind of situation. At least I hope that it ends that way."