"This was a quite astonishing finding," Mr Milne said, "given that I played competitive football and tennis right up to the accident and following the accident could barely walk to university.
"I had never had a serious injury and I had a blunt impact injury in an avalanche. You can't have a much more intense injury happen than an avalanche; it's obviously a one-off event that's caused it."
He had had one minor sprain in the past. A scan showed some inflammation in the ankle, but in the surgeon's opinion, this was not related to the pain, which was caused by the avalanche injury.
"The surgeon said the other thing going on in my ankle was something that might affect me when I'm 50, but not when I'm 21."
Mr Milne immediately sought a review, but, because that process could take months, his parents paid for the operation to be done privately last June. It cost around $8000.
Last month, ACC reversed its decision and agreed to pay.
"Before the [review] was heard, ACC had considered the evidence and concluded that my application for surgery was legitimate.
"It seems as though ACC is arbitrarily declining surgery requests without realising the effect on people's lives. Not everybody has a spare $20,000 lying around to fund an operation."
Mr Milne said his ankle was making good progress since the operation.