|North West 200 international road races|
|Date: Saturday 13 May Venue: Triangle Circuit, Portstewart, Coleraine, Portrush|
|Coverage: All races live on the BBC sport website and BBC Radio Ulster; Highlights on BBC One NI Friday 12 May, Sunday 14 May and Monday 15 May|
John McGuinness broke four vertebrae and three ribs in addition to the leg fracture that he sustained in his crash at the North West 200 on Thursday.
Initial reports indicated McGuinness, 45, had sustained a broken leg.
The English rider's Honda team said on Friday that McGuinness would remain in Belfast's Royal Victoria Hospital for another week.
"John will wear a cast for up to six weeks in treatment for the vertebrae," said the Honda statement.
McGuinness ruled out of Isle of Man TT
McGuinness' injuries mean he will miss the Isle of Man TT which starts in two weeks.
"John has been diagnosed with a compound fracture to his right lower leg, while in theatre on Thursday night it was not possible to plate the leg as initially thought due to the extent of the injury, and tomorrow an external fixator will be fitted," added the Honda statement.
"In addition, John has also suffered four broken vertebrae and has three broken back ribs."
The Englishman has earned 23 career wins at the Isle of Man event which begins with a week of qualifying on 27 May before competition starts on 3 June.
His wins tally puts him second in the all-time TT list behind the legendary late Joey Dunlop, who won 26 times at the Isle of Man meeting.
Martin also out of Superbike and Superstock classes
Following McGuinness' crash, Honda Racing have opted to withdraw their bikes from the Superstock and Superbike events in Saturday's North West 200 races.
English star Guy Martin was scheduled to also compete for the team in both races although he will still race for the Wilson Craig outfit in the Supersport class.
Honda team manager Jonny Twelvetrees said that McGuinness had sustained "a substantial injury to his right tibia and fibula".
"It is a real blow to John and the team, but he's got an incredible amount of spirit and is in very good hands with the medical staff at the Royal Victoria Hospital," added the Honda team boss.
McGuinness has also earned six North West 200 wins during his 27-year career.
Thursday's accident happened at the Primrose Hill section of the course around 20 minutes before the practice session was scheduled to end.
McGuinness dislocated a thumb during a Honda team test at Castle Combe in early April.
Action resumed on Thursday evening at the Northern Ireland road racing meeting when Supersport, Superstock and Supertwins races took place.
There will be five further races on Saturday's main race day at the event.