Duncan, who could not be reached for further comment, confirmed she had withdrawn from the meeting following a crash during an event in Taranaki last weekend.
It is unclear how bad her injuries are at this stage.
Duncan was going to use the event has preparation for the defence of her Women’s Motocross World Championship series title which is scheduled to get under way in Italy in late April.
International commitments have restricted Duncan’s involvement in the New Zealand Motocross Grand Prix.
But Duncan, who turned 25 this week, was looking forward to competing this year.
She has previously raced against men at the event but was to compete in the women’s grade to lower her risk before the world championships.
It is the 60th anniversary of the Woodville event and Duncan was the headline attraction, so it will be a blow for the meeting.
Manawatu Orion Motorcycle Club president Brad Ritchie said last week he was thrilled to have Duncan complete.
"To have a two-time world champion at the event will be spectacular. We have been delving into the history of the event and recognising people who have played a part over the years," he said then.
"For them to be able to watch Courtney Duncan from the spectator embankment will be pretty special, I’m sure."
