Millimetere by millimetre the bone calcified, while time ticked towards the qualifying deadline for the 2020 Games.

But the eight-time world champion and two-time Olympian has been cleared to ride after nearly two years of setbacks, and now sets her sights on qualifying for the Tokyo Olympic Games.

Buchanan has had three operations on her sternum to repair the damage caused by off-road accident near Cooma at the end of 2017, which resulted in life-threatening injuries.

She broke her sternum, had collapsed lungs, a broken nose and dangerous bleeding around her heart, keeping her off the bike for nineteen months.

The 28-year-old Olympian suffered several setbacks during rehabilitation but her body has finally healed after the last sternum reconstruction, with doctors giving her clearance to ride.

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"It was like watching paint dry as I waited three months for the final CT scans," Buchanan said.

"I watched my sternum bone get a little bit wider and more calcification. It was definitely a slow bone to heal but to finally see it healed and the cardiovascular surgeon to say, 'you're not necessarily cleared to ride but more-so you're cleared to crash'.

"It was a huge relief and opened up a pathway towards the Olympic Games. This is the hardest part now - to build back the strength and condition side, but having been at two Olympics previously reminds me that I can do it again."

Buchanan spoke as part of an Oakley promotion to thank the sponsors for supporting her after almost two years of no racing.

Buchanan has been one of Australia's leading medal contenders at the past two Olympics, but she hasn't been able to finish on the podium.

Australia has two qualifying positions for the BMX event but Buchanan finds herself outside the ranking system with less than a year before the Tokyo opening ceremony.

The two-time Olympian will spend six weeks to build herself back into the rankings system and help secure Australia maximum quota spots for the 2020 Games.

Buchanan will ride in her first Tokyo Olympic points round in Indonesia next month, before heading to Tokyo, Switzerland and back home to Australia for international events.

"It's a long shot but I'm coming in with no target on my back and with the best support network behind me," Buchanan said.

"My focus is with the team and as we moved towards this goal, we have to make sure we're not skipping any steps now."

Buchanan will return to Australia for a BMX camp at Shepparton to train on a course which will be used for four Olympic qualifiers.

The venue will also host the opening BMX 2020 World Cup round in January, which will be the first time Buchanan competes on home soil since winning her maiden world title in Canberra ten years ago.

"It was an absolute fairytale moment to win my maiden world title in my hometown," Buchanan said.

"The whole surreal story behind it - leading from the ashes, losing our family home in the [2003] fires, to then have this world class facility and win my first world title. It was a snowball.

"Looking back now I realise how much that really diverted my career from being just a BMX athlete to the diverse, dual cycling and disciplined athlete I am today. It's a real testament to Canberra.

"I basically haven't raced an event in Australia since the World Championships in Canberra to now have four Olympic qualifiers on two different weekends in Shepparton. It's really been ten years since I've had the Aussie home soil advantage."

Buchanan returned to training two months ago and has a new coach to help her journey towards the Olympics with the new limitations to her body.

Buchanan was considering a bid to compete in both the freestyle and racing BMX events in Tokyo, but injuries narrowed her focus on her specialist event.

"It's been a whirlwind from having ten years of my career being injury free - with two Olympic Games and eight world titles - to then having a lot setbacks with not only life challenges but medical complications," Buchanan said.

"It's the mental aspect of never being as strong as I am now. The last two Olympics mentally let me down and I've had a lot of time to focus on different ways to wind down and focus.

"The mental toughness I've gained from these situations is going to be key coming into Tokyo."