The 40-year-old Briton was taken to hospital yesterday after suffering two spinal fractures, a concussion and broken ankle. He was awake and alert when he was sent to hospital and had surgery to stabilize his right ankle.
Franchitti's car went airborne and destroyed a portion of the catch fence before spinning several times while debris was sprayed toward the grandstands after he made contact with Japanese driver Takuma Sato on the final lap.
"Thank you to everyone for all the well wishes. They mean a lot to me," Franchitti said in a statement released by IndyCar, which is reviewing the incident.
"I would also like to send my best to all the fans involved in the accident and hope that everyone is alright."
Once he is released from the Houston hospital, Franchitti will be transferred to Indianapolis, where his Chip Ganassi team is based, for further evaluation, according to IndyCar.
An IndyCar official and two spectators were also sent to hospital for evaluation, while media reports have said 11 other spectators were evaluated on-site.
The crash came less than eight months after nearly 30 fans were injured at the Daytona International Speedway when a 10-car crash sent debris, including a tire, into the crowd during the final lap of a Nationwide NASCAR race.
It is also nearly two years since the motor racing world was left reeling when one of Franchitti's best friends, fellow Briton Dan Wheldon, died after a fierce 15-car crash in the IndyCar season-finale at Las Vegas Motor Speedway.
