Boy internally decapitated in car crash saved by off-duty policeman

Boy now one third of an inch taller due to his spine being stretched during incident

The damaged cars after the crash that severely injured both Killian Gonzalez and his mother, Brandy. (Leah Woodward)

An off-duty police officer and his wife saved a boy whose skull was separated from his spine in a car crash.

Killian Gonzalez was driving home to Nevada with his mother, Brandy, when they were caught in hailstorm in Idaho.

Their car skidded on the ice and smashed head on into another car.

Witnessing the crash was policeman Joel Woodward and his wife Leah, who heard the four-year-old boy screaming from inside the car as they ran to help.

With the car doors still locked, Mr Woodward smashed in the back window and saw the extent of Killian's injuries.

He then told his wife to hold the boy's head steady until emergency services arrived.

Ms Woodward told the New York Times: "As a mom, that just goes right to your heart. My immediate instinct was: ‘You have to help that little guy'.

"My first instinct would have been to cradle the little guy, but clearly that would have been the wrong choice."

Killian Gonzalez, 4, recovering in hospital after the crash (Leah Woodward)

They draped his broken arm against his side and covered him in a blanket. Ms Woodward saw a pinkish gel splattered over the backseat which she was later told could be spinal fluid.

While holding his head for over 30 minutes she spoke to Killian in an effort to keep his attention after finding out details about him from his trapped mother, Brandy.

At one point, Ms Woodward remembered him saying: "I don't hurt anymore, I am done."

It took emergency services an hour and a half to retrieve his mother from her car.

Killian, his mother and the other driver were flown by air ambulance to hospitals, local police said.

According to his grandmother, the four-year-old suffered a right upper arm fracture, several broken ribs and a fracture at the base of his skull where the brain stem connects to the spinal cord.

This is colloquially known as clinical or internal decapitation and happens when the ligaments, muscles and joints connecting the base of the skull and the top of the spine are damaged.

Both lungs were bruised. As a result of the incident, the boy is one third of an inch taller due to his spine being stretched.

Ms Gonzalez was left with an open lower fracture in her left leg, a right upper leg fracture and a left lower arm fracture.

Killian has been discharged from hospital and is walking around unassisted, albeit while wearing a hard collar to protect his head and neck.

Grandmother Leslie Dorn has set up a fundraising page to help pay for medical expenses. Nearly $21,000 has been raised of the $100,000 target.