Leah Washington was one of four people seriously hurt last week when two carriages collided on the Smiler ride.
Doctors have confirmed that the teenager, from Barnsley in South Yorkshire, has had her left leg amputated above the knee and suffered a fractured hand in the incident.
Leah’s boyfriend, 18-year-old Joe Pugh, was treated for two broken knees and extensive hand injuries, University Hospitals of North Midlands NHS Trust said.
Alton Towers, which opened yesterday for the first time since Tuesday’s crash, said that it was “deeply saddened” by news of Leah’s injuries and insisted it would provide “full support” for all 16 people who were hurt.
In a statement issued by the hospital, Leah’s father, David Washington, said: “We would like to thank our family and friends and all the well-wishers for their support.
“Leah has suffered a life-changing injury and now has many months of rehabilitation ahead of her.
“We have done this to put people’s minds at rest and we would also ask everyone to respect Leah’s privacy as she undergoes this rehabilitation.
“We would like to thank all the emergency services at the scene and all the hospital staff who saved Leah’s life.”
Leah; her boyfriend Joe; 27-year-old old hotel assistant manager Daniel Thorpe from Buxton in Derbyshire; and 20-year-old Vicky Balch, from Leyland in Lancashire, have been described as the most seriously injured.
Balch suffered potentially life-changing injuries in the crash, and is expected to make a “substantial claim for damages” to support her recovery, her solicitor said last week.
The four are being treated at the Royal Stoke University Hospital and the University Hospital Coventry.
A spokesman for the University Hospital Coventry declined to comment on Thorpe’s condition, while Balch’s solicitor said there was no update on her recovery.
Pugh’s father, Simon, said: “I would like to thank our friends and family for their support.
“We would also like to thank the staff at the hospital who have been very accommodating, have been lovely to us and have protected our privacy.
“We would ask people to respect Joe’s privacy now and over the weeks and months ahead.”
An Alton Towers spokeswoman said: “We have made contact with all the families and have assured them that we will provide full support to all of those involved now, and throughout their recovery and rehabilitation.”