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Old 10-29-2015, 02:25 AM   #23661
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What causes basilar skull fractures in motor sports incedents? All Google turns up is "a hard blow to the head". What movements stress the skull enough to break it?
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Old 10-29-2015, 03:21 AM   #23662
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What causes basilar skull fractures in motor sports incedents? All Google turns up is "a hard blow to the head". What movements stress the skull enough to break it?
High-speed frontal crash, in particular while wearing a helmet and with the upper torso restrained with harnesses.

Yes, you should buy a HANS.

--Ian
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Old 10-29-2015, 06:56 AM   #23663
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I have a Hans. And yes I know that does it. But how.
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Old 10-29-2015, 09:38 AM   #23664
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I have a Hans. And yes I know that does it. But how.
Because your torse remains stationary and your head does not. As has already been explained.

Go watch some IIHS (or whatever it's called) crash test videos if for some reason this still isn't making sense. Your head gets whipped about mightly in even low speed crashes.
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Old 10-29-2015, 09:39 AM   #23665
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Jesus guys. I get the physics of the crash. What happens anatomically. Is it just the impact? Or is it something in your neck.
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Old 10-29-2015, 09:59 AM   #23666
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Since our shoulder harnesses cover both shoulders holding them firmly back into our seats, a sudden deceleration injury would allow our head to flex rapidly forward and down, thereby causing fractures to the base of the skull and/or the upper cervical vertebrae. This typically causes death by several means, including damage to the upper spinal cord and/or lower part of the brain resulting in the inability to move and breath.
Race Car Driver Deaths: The Medical Causes of Racing Deaths w Examples

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Old 10-29-2015, 10:53 AM   #23667
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Jesus guys. I get the physics of the crash. What happens anatomically. Is it just the impact? Or is it something in your neck.
Basically, the skull just tears in half from the forces generated by the rapid deceleration of the head as it tries to pull itself free from the body. That particular part of the skull happens to be the weakest link in the chain.

A brief synposis from Race Drivers' Head Injuries Misunderstood - tribunedigital-chicagotribune


When a car crashes, usually against an immovable concrete retaining wall, the "rapid deceleration"--i.e., the sudden stop--creates surges of energy, many times the force of gravity, called "G-spikes."

Inertia, which is the physical tendency of mass to continue in motion at a sustained rate, tries to keep the human body moving forward inside the car. But the driver's safety "harness" (a system of lap and shoulder belts) stops the pelvis first, then the torso. That leaves the head, which at 10-12 pounds is the heaviest part of the human body, in motion--and in violent velocity relative to the car.

"The neck is now acting as the restraint, or the tether, for the head," Melvin says. And when the head reaches the end of its tether but strains to continue moving under tremendous "G-loading," the fatal damage occurs "right then and there," Melvin says.

The forces are trying to pull everything in the head and neck straight through the top of the skull. But the top is strong enough that when, literally, something has to give, the base--the weakest part of the skull--usually cracks. If it doesn't, then the neck usually breaks and/or severe brainstem stretching occurs.
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Old 10-29-2015, 01:00 PM   #23668
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...

When a car crashes, usually against an immovable concrete retaining wall, the "rapid deceleration"--i.e., the sudden stop--creates surges of energy, many times the force of gravity, called "G-spikes."

Inertia, which is the physical tendency of mass to continue in motion at a sustained rate, tries to keep the human body moving forward inside the car. But the driver's safety "harness" (a system of lap and shoulder belts) stops the pelvis first, then the torso. That leaves the head, which at 10-12 pounds is the heaviest part of the human body, in motion--and in violent velocity relative to the car.

"The neck is now acting as the restraint, or the tether, for the head," Melvin says. And when the head reaches the end of its tether but strains to continue moving under tremendous "G-loading," the fatal damage occurs "right then and there," Melvin says.

The forces are trying to pull everything in the head and neck straight through the top of the skull. But the top is strong enough that when, literally, something has to give, the base--the weakest part of the skull--usually cracks. If it doesn't, then the neck usually breaks and/or severe brainstem stretching occurs.
Sounds like playing "crack the whip" with your spine as the whip and your head as the cracker on the end of it.



Also not mentioned, the added weight of a helmet only exacerbates the problem.
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Old 10-29-2015, 01:05 PM   #23669
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Why does the base break? I'm still a little confused on the anatomy. What is the actual force in the base of the head?
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Old 10-29-2015, 01:08 PM   #23670
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Feel the back of your head. Besides your face, which has no force acted on it in this case, it's the flatest part of your skull. Strength of flat< strength of curve.
I've seen some pretty impressive skull fractures, and the basal type is the most common.
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Old 10-29-2015, 01:10 PM   #23671
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I get that theres alot of force. And it's a weak part of your skull. But for something to break don't you need forces in opposite directions on it?
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Old 10-29-2015, 01:13 PM   #23672
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I'm not even sure what you aren't understanding at this point.

The force of the impact (eg, sudden deceleration) pulls your head forward. Your body cannot move with it because you're strapped to your seat.
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Old 10-29-2015, 01:15 PM   #23673
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I get that theres alot of force. And it's a weak part of your skull. But for something to break don't you need forces in opposite directions on it?
Your body is moving forwards at 100 mph. The car hits the wall and stops, the seat is bolted to the car, so the seat stops, the harnesses are bolted to the cage, so the harnesses stop, your body is strapped in with the harnesses so your body stops.

Your head, OTOH, is only restrained by your neck. Basically it's like giant fingers come down and try to pull your head off.

--Ian
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Old 10-29-2015, 01:15 PM   #23674
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I think you might be confused about the nature of the fracture. In this case, it isn't caused by compression, but rather tension. Think of it as the base of your skull being torn apart.
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Old 10-29-2015, 01:16 PM   #23675
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Yes. That is physics. I understand this.

Tell me what makes the skull break.

What I've heard so far is:

You break your leg when you fall from a tall building.

Not: the force of your body impacts onto your leg which had met an imovable object.
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Old 10-29-2015, 01:16 PM   #23676
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I get that theres alot of force. And it's a weak part of your skull. But for something to break don't you need forces in opposite directions on it?
The head (which is in motion and retains momentum) is literally trying to tear itself off of the torso (which has stopped moving, and therefore has no momentum.) That's your "opposing forces."

Once the torso stops moving, the head is still carrying significant momentum. It flexes forward across the neck, and wants to continue moving forward. The brain, the skull, the helmet, all that stuff is trying to pull the moving head forward against the stationary body.

The skull is anchored to the body by the tendons and ligaments of the neck, which attach to the skull at a point near the base. That's roughly where the fracture occurs.



I don't see why this is hard to understand.



Imagine that you have an elevator at the top floor of the World Trade Center. The elevator is your head, and the building is your body. The cable between the two is your neck.

You release the brakes and de-clutch the motor, which allows the elevator to start plummeting towards the ground. At about the 30th floor, you suddenly apply the brakes to the cable spool up on the roof. The elevator car has built up a lot of momentum during its fall, so it starts straining against the cable. The cable starts to stretch. If the part of the elevator car to which the cable attaches is weaker than the cable itself, then that section of the car will be ripped off and remain attached to the cable, while the rest of the car falls to the ground. That attachment point is the base of the skull.
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Old 10-29-2015, 01:17 PM   #23677
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I think you might be confused about the nature of the fracture. In this case, it isn't caused by compression, but rather tension. Think of it as the base of your skull being torn apart.
Thank you. We are getting closer.

So your neck muscles pull on your head? And pull a bit of skull off?

So the tendons are stronger than the bit of skull where it fractures?
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Old 10-29-2015, 01:20 PM   #23678
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Your neck muscle are just holding the base of your skull stationary, which makes for a nice anchor.
Unfortunately, inertia tears the skull off at the anchor.
Like this:

Not like this:

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Old 10-29-2015, 01:21 PM   #23679
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Thank you. We are getting closer.

So your neck muscles pull on your head? And pull a bit of skull of?
From http://www.caranddriver.com/features...-neck-feature:

"Basically," Hubbard explains, "our heads are secured to our bodies by a series of tendons and ligaments. These tendon and ligament fibers penetrate into the base of the skull and anchor into the bone tissue.

"When a racing car goes headfirst into a tire wall," he continues, "the driver's body is fairly well secured to the car via the seatbelts, and as the car decelerates quickly, so does the body. The driver's head, which weighs about 10 pounds without a helmet, keeps moving. It's like a pendulum that's anchored at the shoulders and relies on the neck to hold it in place. The strain on those neck tendons and ligaments is enormous, and the weak link is the base of the skull, the anchor point for the head. If the accident is severe enough, the base of the skull breaks. Then you get stretching of the spinal cord and the breaking of major blood vessels that go to and from the brain. The skull fracture itself isn't deadly, but either the brain trauma or the loss of blood flow is."

--Ian
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Old 10-29-2015, 01:31 PM   #23680
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From http://www.caranddriver.com/features...-neck-feature:

"Basically," Hubbard explains, "our heads are secured to our bodies by a series of tendons and ligaments. These tendon and ligament fibers penetrate into the base of the skull and anchor into the bone tissue.

"When a racing car goes headfirst into a tire wall," he continues, "the driver's body is fairly well secured to the car via the seatbelts, and as the car decelerates quickly, so does the body. The driver's head, which weighs about 10 pounds without a helmet, keeps moving. It's like a pendulum that's anchored at the shoulders and relies on the neck to hold it in place. The strain on those neck tendons and ligaments is enormous, and the weak link is the base of the skull, the anchor point for the head. If the accident is severe enough, the base of the skull breaks. Then you get stretching of the spinal cord and the breaking of major blood vessels that go to and from the brain. The skull fracture itself isn't deadly, but either the brain trauma or the loss of blood flow is."

--Ian
This is the answer I was looking for.

Joe. You once again explained the physics of the crash. Not the anatomy of the injury.
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