Jockey William Buick will see a specialist to determine the extent of the injury he sustained in America.

Buick was riding the Mark Johnston-trained Permian when the Royal Ascot winner fatally fractured a foreleg and unseated him shortly after crossing the line in the Secretariat Stakes at Arlington Park in Chicago last weekend.

Initial reports suggested Buick was suffering from a fracture to his T-12 vertebra and while he was allowed to fly home on Sunday, the rider has yet to find out how long he will be sidelined.

Buick is the No.1 rider for Godolphin trainer Charlie Appleby.

"He sees a specialist late tomorrow afternoon (Saturday AEST) and we'll know an awful lot more after that," Appleby siad.

"Until he sees someone, we're none the wiser.

"He's upwardly mobile and getting about, but tomorrow is when we'll know more.

"At this stage there is no time-scale, but he's been into the yard. He just can't do anything else until we know what is wrong."