Dario Franchitti has left the Memorial Hermann Texas Medical Center in Houston and is heading back to Indianapolis, where he will receive further evaluation and faces a second surgery on his broken right ankle.

Franchitti was photographed by his racing driver brother Marino as he walked under his own power - albeit somewhat gingerly and using a walker to help him. He was wearing a temporary caste on his right ankle, and also a back brace to support and protect his two fractured vertebrae, and was pictured with his dogs who had been flown in by his estranged wife, actress Ashley Judd.

"I'm overwhelmed by the outpouring of support and I'm thankful to have such a great family and such wonderful friends and fans," said Franchitti in a statement released by his IZOD IndyCar Series team, Chip Ganassi Racing, and also carried on Franchitti's personal Twitter feed.

"Thanks to everyone at the hospital and the track who took such good care of me during my stay in Houston," Franchitti added. "I look forward to watching Scott, Alex and the Target team next weekend on television, and will be pulling for them as they go for another championship."

Franchitti has already had initial surgery to stabilise the ankle fracture a few hours after the crash in the last lap of the weekend's second doubleheader race in Houston, but will need a second surgery in the coming days to effect a more permanent treatment for the injury.

IndyCar's medical director Dr Michael Olinger confirmed that Franchitti would not require surgery for the fractured vertebrae, which are expected to heal with normal rest and rehabilitation over the winter. Franchitti also suffered a concussion in the violent accident which occurred after a collision with Takuma Sato, who was not injured in the incident.

With Franchitti ruled out of action for the final race of the 2013 season, his place in the #10 car will be taken at Auto Club Speedway in Fontana, California by his old friend Alex Tagliani.

"I'm sure as Tag has put out there before, it's a tough situation for anybody to be in," said Franchitti's team mate Scott Dixon, who goes into the final race of the year in the lead of the championship standings and facing a head-to-head duel for the title at Fontana with Penske's Helio Castroneves.

"I think they picked the best guy, I'm great friends with Tag, we hang out a fair bit, and it makes it an easy transition," said Dixon. "Obviously last year Alex was very fast at Fontana until he had a mechanical issue and exited the race, but he was running, I think, in first or second position for most of the later parts of it. So welcome to the team, and as I said, he's a good friend and a hell of a competitor, and he's going to be tough to beat there next weekend, I think."

As welcome a replacement as Tagliani is, Dixon would understandably rather have had his regular team mate alongside him for the climax of the title battle.

"Personally, I would have liked Dario (Franchitti) to be there next weekend and to be in fighting spirits and helping me win the championship," Dixon agreed. " But it's nice to know that Dario is doing okay. He's going to mend well, but obviously he can't race at the moment and won't be able to come out for a little bit."

"As we all know, he was pretty beat up," Dixon continued. "I think he arrives back in Indy today, so that's a good thing - I know he's got control of his phone again, so that's a good sign! You know, he seems to be in good spirits.

"I know he wants to come out to Fontana and support the team, so we'll see how his recovery goes and see what choice he makes on coming out to the West Coast," Dixon added. "But very lucky - and just sad that he's not going to be my teammate come next weekend to try and finish this out.

Castroneves added that he'd also been in touch with Franchitti, as part of the regular post-race banter between the drivers.

"Just joking around internal with all the drivers, they were kind of like send emails but were not having him respond, but we understand he probably was on medication," said the Brazilian. "But since finally he was able to answer to all of us, he mentioned that he is on a lot of painkillers so he's not feeling so much. He is joking right now he's not feeling much.

"But we are very glad I mean, it could be more serious than that," he added. "The catch fence did their work, glad that it at least bend a little bit so the impact didn't hurt more than it was and also hit spectators. All about this, it's kind of like checking and make sure that those type of scenarios, at least the car did the job, the safety aspect did their job. And for him, unfortunately he's in this situation, but he will have time to recover and not miss any races for next year."