Neck twisting

[Cap'n Refsmmat]

So today we were having a little debate about a rather gruesome subject: Is it really possible to kill someone by twisting their neck until it snaps? (Twisting in the same axis as you'd turn your head left to right. Presumably this would be done by grabbing the victim's head and turning. It's very popular in movies.)

 

One person claimed she had asked her chiropractor and was told it was impossible. (I find this funny, as studies have shown the neck manipulations and twists chiropractors do can cause strokes.) I'm on the other side, as I seriously doubt such a twist would be very good for the spine. I just don't know if you can actually sever the spinal cord by twisting far enough.

 

Who's right?

[iNow]

It's better to jerk it forward or backward quickly than to twist it, but it's certainly possible. What you're going for is a cervical dislocation. Mokele mentioned this recently as a way to quickly and painlessly kill lab mice.

 

http://en.wikipedia.org/wiki/Cervical_dislocation

[Mokele]

Yes, you can easily kill someone that way.

 

Basically, your vertebrae have a solid bone disk (the centrum), and towards your back (dorsal/posterior), your spinal cord lays on top of it, with a ring of bone encircling it. If you rotate about the centra (as such rotations always are), you can pinch/sever the spinal cord (which isn't really very strong).

 

It's doubly bad in the neck, where you have two large arteries running parallel to the centra on each side, enclosed by bone rings. Theoretically, a strong enough twist could sever those as well.

 

Mokele

[ecoli]

Mokele mentioned this recently as a way to quickly and painlessly kill lab mice.

 

there's also a way to do it by quickly pulling the tail, but its only painless if you do it right.

[Mokele]

Pulling on the tail is part of cervical dislocation - restrain the animal by pressure on the neck and pull backwards via the tail.

[Cap'n Refsmmat]

Mokele: So basically you're saying that the axis of rotation on the vertebra (the point they pivot around) is not where the spinal cord runs through, making the vertebra pinch the cord when they are rotated too far?

 

It's hard to visualize without a diagram, sorry.

[Mokele]

Make a circle with the thumb and middle finger of each hand. Stack your hands on top of each other, with your wrists on top of each other and the holds aligned (this may be a bit uncomfortable). Now bend one hand at the wrist.

 

[Cap'n Refsmmat]

Aha. That makes sense. That's sort of what I was envisioning, but none of the diagrams made sense.

 

Thanks.

 

 

(So this means I should drop the habit of popping my neck by twisting?)

[Mr Skeptic]

From that diagram, would the Spinous process normally bump into the one of the protrusions on the vertebrae below it, preventing it from turning past that point? Ie, breaking someone's neck would require either breaking one of the bone protrusions, or separating two vertebrae?

[iNow]

(So this means I should drop the habit of popping my neck by twisting?)

 

I don't think you could apply enough force, nor do so quickly enough, for this to really ever cause cervical dislocation. As I understand it, it's more about air bubbles popping. When I was prepping for my black belt test, my neck, back, and shoulders got worked out very heavily, and my neck would pop all of the time. It doesn't happen so much anymore, and while it's probably better to avoid over-doing it, I can't see that it would be related to the harm described in this thread (can anyone perchance confirm/refute this for us?).

 

 

Mr Skeptic - I'm not really sure, but I postulate that the bone would not need to break or separate to pinch or sever the spinal cord. It could likely do it while remaining intact, just at a lower order of probability. One way or the other, I'm confident that Mokele or ecoli are better suited to address the particulars.

[blike]

From that diagram, would the Spinous process normally bump into the one of the protrusions on the vertebrae below it, preventing it from turning past that point? Ie, breaking someone's neck would require either breaking one of the bone protrusions, or separating two vertebrae?

The angle of the spinous process varies based on the segment of the spine you're looking at. In the case of the cervical vertebra, they protrude at a higher angle from the vertebral body. If you take a look at the image below, in the left pane, you can see the spinous processes protruding posteriously (the patient's back, i.e. posterior, is on the right). What that means is that at least some element of extension would have to be in place for the spinous process to play a huge role. What you're more likely to see is either disarticulation of the superior and inferior facets of adjacent vertebra, or a fracture of the facets resulting in the same thing. Either way, the end result is that the spinal cord could either be compressed, twisted, or even severed by protruding bone fragments. If this occurs at a high enough level (and with enough cord compromise), it would result in quadripeligia and would likely paralyze the diaphgram, arresting respirations and resulting in death.

 

[Durro]

Hi,

 

I'm new here and just saw this topic. I am a Radiographer who takes X-rays and CT scans for a living, so I might be able to add to this discussion.

 

Cervical spines can and do become unstable from various flexion and extension and/or rotational forces. I've seen this literally thousands of times from car accidents, sporting injuries, diving accidents and othe mechanisms of force. I presume that given enough force, the cervical spine would be susceptible to injury from someone twisting the neck forcefully.

 

The neck is stabilised by a number of ligaments that run between the vertebral bodies and between various other parts such as the facet joints. The joints themselves also place limitations on normal range of movement - the facets allow a small amount of rotation and flexion/extension, but there are limits.

 

However, if these limits ar exceeded by force, the ligaments can tear and the bones forming the joints can break as well. The superior and/or inferior articular facets, which form either side of the facet joint, can actually break and allow unstable movement of the vertebral column. The cervical spine can then move and damage the cervical spinal cord.

 

Sudden force can also create intervertebral disc herniation, particularly from forced neck flexion. Disc herniations can also cause nerve damage.

 

The nerves that supply the diaphragm exit the cervical spine at the C4 level. Severe spinal damage above this level is fatal, as the body loses the ability to breathe. Below this level, various degrees of quadriplegia (now called tetraplegia) or paraplegia can occur, depending on the level of damage and which spinal nerves exit at an undamaged level.

 

So, can a neck be "broken" with human hands. I really think so, but it would have to be very forceful to overcome the stability of the cervical joinst and ligaments. I've seen necks broken and/or dislocated from diving onto the head, where 70 kilograms of body weight landing on the neck creates enough force to cause severe injury. Same with car accidents, where sudden deceleration of the body but continued forward movement of the head caused hyperflexion and bilateral facet dislocation. Hangman's fractures are caused by the suuden sideways movement of the C1/2 articulation when a head is forced laterally by the hangman's boose or other causes that mimic this.

 

If strong human hands can reproduce these types of forces, then yes, a cervical spine can be severely damaged and paralysis or even death could be caused.

 

Cheers,

 

Durro.

[KParcher]

I agree with Durro. Except I would like to clarify one point.

 

I've seen necks broken and/or dislocated from diving onto the head, where 70 kilograms of body weight landing on the neck creates enough force to cause severe injury.

 

In order to calculate the force we need to know the mass of the object (in this case 70 kg) and the acceleration (m/s^2) <In this case, we will use 3 miles per hour which = 1.34 m/s^2> Multiply the numbers for mass and acceleration to find the force of the object. 70 kg * 1.34 m/s^2 = 187.60 N ..... "creates enough force to cause severe injury."

Edited December 6, 2012 by KParcher

[John Cuthber]

I agree with Durro. Except I would like to clarify one point.

 

 

In order to calculate the force we need to know the mass of the object (in this case 70 kg) and the acceleration (m/s^2) <In this case, we will use 3 miles per hour which = 2.68 m/s^2> Multiply the numbers for mass and acceleration to find the force of the object. 70 kg * 2.68 m/s^2 = 187.60 N ..... "creates enough force to cause severe injury."

 

3 miles per hour isn't an acceleration, it's a speed.

It's known that little old ladies can deliver enough torque to snap the necks of birds so I guess a strong adult could snap someone's neck this way

 

http://www.dailymail.co.uk/news/article-6601/Queen-bloodsports-row.html