Alfa Romeo Formula 1 junior Juan Manuel Correa underwent 17 hours of surgery on Sunday, which doctors deemed successful.
Correa has been in hospital since being involved in the same crash that claimed the life of fellow Formula 2 racer Anthoine Hubert at Spa at the end of August.
The Sauber Junior Team driver - a podium finisher in his maiden F2 season - was taken to hospital in Liege with serious leg injuries, but then contracted a condition where his lungs filled with fluid and was placed in an induced coma on a life support machine.
After fighting through that, Correa then had to quickly recover from the drugs he had been on and decided whether to have part of his right leg amputated, which he decided against in favour of initial surgery on Sunday.
Speaking for the first time since the crash in a statement issued on his behalf on Thursday, Correa said: "This past few weeks have been extremely tough, tougher than anything I have ever faced both physically and mentally.
"I understand my future regarding the recovery of my legs, specifically my right leg is still quite uncertain, and that my physical rehab will be extremely long and complicated.
"I am still processing everything that has, and is, happening.
"I want to thank every single person who one way or another has shown me their support.
"I am humbled by the immense number of caring and affectionate messages I have received.
"Thank you all from the bottom of my heart, and know that your encouragement and positivity have made a difference."
The statement confirmed that doctors believed the surgery had been a success on Sunday, but that the three-day period following it was crucial for his health.
Explaining the procedure, the statement read: "The days following the surgery were stressful as though deemed a success in the operating room, the next 48-72 hours were critical in the final outcome of the Flap Surgery procedure.
"Now, Thursday, and more than 72 hours later, doctors are confident in a successful procedure while still under careful observation.
"During the procedure, doctors were forced to remove more bone material than they anticipated and solve several blood vessel issues, but state that the main objective of the surgery was achieved.
"Juan Manuel remains in a London hospital and he is scheduled for one additional, less complex surgery in two weeks' time."