The 30-year-old was hit by a scooter in Hengelo and underwent overnight surgery for his injuries.
His wife has confirmed the horrific incident to TC Tubantia as her husband continues to recover in hospital.
An ambulance arrived shortly after the collision and provided first aid to the Dutchman, who was then taken to hospital with brain damage.
Lammertink was due to take part in the Tour de France next week.
He is currently riding for the UCI WorldTeam Intermarché – Wanty – Gobert Materiaux.
Lammertink was the first on the Tour de France start list in 2017 and 12 months later he competed in the Giro d’Italia.
The highlight of his career came when he won the general classification of the Tour de Luxembourg ahead of Philippe Gilbert and Alex Kirsch bin 2016.
British sprinter Mark Cavendish will make his first Tour de France return since 2018 after being named to Deceuninck-Quick-Step’s eight-man squad for the race
The 36-year-old has enjoyed a renaissance in recent months and will now have the chance to add to his 30 stage wins – a number only improved by legendary Eddy Merckx.
“I am delighted to be returning to the Tour de France with Deceuninck-Quick-Step,” said Cavendish.
“Obviously the circumstances with Sam could be better – he had a Special Tour last year and I’m sad he can’t defend his green jersey.
“But at the same time, I’m delighted to come back to a race with which I have such an affinity and where I have so much history.
“It’s the biggest bike race in the world, and I’m going to do everything I can to grab this opportunity with both hands. “
Slovenian Tadej Pogacar is the favorite to win the Tour, while Briton Geraint Thomas is expected to offer some tough competition.