Her right hand was all-but severed, "hanging on by a tiny tendon", according to the Canberra Hospital plastic surgeon Ross Farhadieh.

It was December 6. Thoughts of many were turning to Christmas and winding down for the holidays. Mr Farhadieh's too. He had family in town. That Sunday afternoon he'd told his mum that he expected things to be quiet. They were off to see the latest James Bond movie.

He parked his car. And then his mobile rang with news of Sarah's accident.

The movie was ditched and Mr Farhadieh was in another theatre altogether by Sunday evening for what turned out to be epic 14-hour surgery in which he painstakingly re-attached Sarah's hand.

One toilet break. No food. Just hour after hour of focus and concentration that stretched well into Monday morning, as Mr Farhadieh performed what he believes could be the surgery of his life, mending bones, tendons, nerves, arteries, veins.

"It was effectively a hand transplant," he said.

"I don't expect to see another one for the remainder of my career."

Within two weeks of the surgery, Sarah, who is right-handed, was writing Christmas cards with the re-attached hand. A year later, she is back at uni, determined to live her life to the full.

Mr Farhadieh believes the world-standard microsurgery services at the Canberra Hospital saved Sarah's hand, but so too did her own quiet determination to not give in and to continue with intensive rehabilitation.

"There are some people who are just very good at dealing with adversity," he said.

"And just because you look at them from the outside and they look very fragile or gentle, it doesn't mean they don't have that iron core. And she's definitely one of those people."

A year later, 21-year-old Sarah is close to tears as she speaks about what her doctors mean to her.

"Oh, I don't even have words," she said. "Just so grateful."

A series of things worked in Sarah's favour on the day of the accident, which was likely the result of fatigue. The first was that an off-duty paramedic was among the first on the scene and helped to get her quickly to hospital by the Snowy Hydro SouthCare helicopter.

Four hours is the critical threshold for a severed limb to be without a blood supply before the muscles start to die. So the hand had to be reattached in Canberra. Mr Farhadieh had blood pumping again to the hand a little over four hours after Sarah's accident.

"It was literally on the cusp so as soon as I saw her hand pink-up, I was like, 'Yes!'," he said.

But the drama did not end there.

There was a push from some to have Sarah transferred to Sydney because it was closer and she could go by helicopter.

Mr Farhadieh was adamant she be flown by fixed-wing aircraft to Melbourne to be in the care of Professor Wayne Morrison at St Vincent's Hospital, the man who led the surgical team that performed Australia's first hand transplant in 2011.

Not only that, Professor Morrison was a mentor to Mr Farhadieh, having trained him during this medical studies.

It would take longer to transport Sarah to Melbourne, but Mr Farhadieh believed it was worth it.

"Really, you want the most experienced people around you to fix this and the guy who did the hand transplant is the world's foremost authority, right?" he said.

Sarah was back in surgery in Melbourne by the Monday evening, the day after her accident. Professor Morrison focused on grafting skin and fat from her thigh on to her damaged arm.

There were three operations in Melbourne and within two weeks, Sarah was home in Moruya, recovering with parents Terry and Annette, with the support of siblings Amy and Nathan.

Mr Farhadieh said for all the trauma experienced by Sarah, everything that could go right, did go right.

"Sarah's outcome has been a spectacular Christmas miracle for all of us," he said.

"Her sensation and motor function has returned and she has a highly-functional hand again."

Apart from everything else, her experience is another reminder to be safe on the roads during the holiday season.

On the day of the accident, Sarah had finished her part-time job and was feeling tired. She still believed she was well enough to drive almost three hours to Moruya. Witnesses say her car simply drifted off to the side of the road.

"I thought I was fine," she said.

"I'd just say to people, 'Take a break, drive with someone'. Or don't drive at all if you're tired."

She remembers little of the accident other than waking up and being told she was in a hospital in Melbourne. She had no other injuries except a graze on her leg. How the hand was actually cut remains a mystery.

Accepting the injury took some time.

"I don't think I looked at my arm for a couple of months," she said.

"You slowly take time. I mean I've got a lot of people around me who are great."

At the time of the accident, Sarah was studying to be a primary school teacher. She has since switched to public health, planning to become perhaps an occupational therapist or psychologist.

The accident played a part in diverting her life path.

"I think I always had a passion [for health] but this probably pushed me more to change and do it," she said.

Mr Farhadieh, meanwhile, is a migrant who moved to Australia from Iran with his family when he was 13. Among his many achievements is  writing a plastic surgery textbook now studied around the world. He says after "being the beneficiary of the brilliant education in this country", he wanted to work in the public health system and help people like Sarah.

"If you don't give back, what's the point?" he said.