Trikki Beltran's bad concussion and his helmet

Per David Damerell:
Why you think something that increases the lever arm won't hurt in
torsional impacts.

I'm more or less of a helmet zealot since undergoing a little attitude
adjustment some years back.

But in support of your observation, I'm pretty sure I messed up my neck a couple
years back taking a header in the water at 20+ mph wearing a helmet
(windsurfing).

There was a definate sensation of the helmet catching water and twisting my
neck.

I'd extrapolate from that to believe that there's a risk factor in bike helmets
around the helmet catching on something (i.e. MTB riding...).

I still wear the things - but it's not a black-white issue with me.
--
PeteCresswell

These threads are all so tiresome. This subject has been beat to
death, and still no conclusion has been reached. You guys can go on
all you want citing statistically insignificant personal events, but
you are neither convincing anyone, nor proving anything. An issue like
this needs scientific study, not the opinion of some random guy off
rec.bicycles.misc.

As for me, I'm taking no side, as both are as unconvincing as the other.

gym.gravity wrote:

Will wrote:

gym.gravity wrote:

gwhite wrote:

Good thing he was wearing a helmet.

**** off!

Given the gentle response above, one might assume that it is too late
for you to get much benefit from a helmet g.


I was just trying to fast forward the thread to it's inevitable
conclusion.

Hitler! Nazis!

There. Thread over. Move along folks, nothing to see here, go back to
your homes.

We now return you to your normally scheduled RBR, RBT, RBM programming.

Mark

David Damerell wrote in
:

Quoting Qui si parla Campagnolo :
Jay Beattie wrote:
Like, does the name Casartelli ring a bell?
He actually hit more of his face than his upper head but I agree...
Helmets-don't hurt, may help. What's so diffuclt to understand?

Why you think something that increases the lever arm won't hurt in
torsional impacts.

Why you think something that dissapates and redistributes the point
stresses that will inevitably also be present in the non-torsional part of
the impact isn't a good thing?

Compare and contrast the maybe 1" difference, allowing for the obviously
different coefficient of friction of skin vs plastic along with the slip in
the helmet suspension, with the abrasions and non-rotational trauma
inflicted.

I personally knew at least one child and one father who would be alive
today if they had been wearing helmets after they died from the trauma of
minor bicycle falls; I know of nobody who has died from a twisted neck.

I also wish I had had a helmet on when I smashed my glass lens into my face
on a fall and took 8 stitches to put the eyebrow and other skin back in
place. It's nice to know you can duck and cover on a fall instead of
trying to keep your cranium off the ground.

On Fri, 15 Jul 2005 23:07:35 -0400, wvantwiller
wrote:


Why you think something that increases the lever arm won't hurt in
torsional impacts.

Why you think something that dissapates and redistributes the point
stresses that will inevitably also be present in the non-torsional part of
the impact isn't a good thing?

But there is no known case where cyclist safety has improved with
increasing helmet use, so obviously what goes on after the crash is
only part of the story.

I personally knew at least one child and one father who would be alive
today if they had been wearing helmets after they died from the trauma of
minor bicycle falls; I know of nobody who has died from a twisted neck.

You think? I wonder why, then, there is no robust evidence that
helmets actually save lives?

Mind you, what would I know? I suffered a serious bicycle crash many
years ago and wasn't wearing a helmet, so obviously I'm dead!

But you misunderstand. The torsional force is important not because
of its effect on the neck, but because of the differential movement it
causes between the hemispheres of the brain. These torsional forces
are reckoned to be a (some say the) major source of permanent
disabling brain injury.


Guy
--
http://www.chapmancentral.co.uk

"Let’s have a moment of silence for all those Americans who are stuck
in traffic on their way to the gym to ride the stationary bicycle."
- Earl Blumenauer

On Fri, 15 Jul 2005 23:07:35 -0400, wvantwiller
wrote:


I personally knew at least one child and one father who would be alive
today if they had been wearing helmets after they died from the trauma of
minor bicycle falls;

How do you know that?

JT

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Just zis Guy, you know? wrote:

But you misunderstand. The torsional force is important not because
of its effect on the neck, but because of the differential movement it
causes between the hemispheres of the brain. These torsional forces
are reckoned to be a (some say the) major source of permanent
disabling brain injury.

Total BS.

John Forrest Tomlinson wrote in
:

On Fri, 15 Jul 2005 23:07:35 -0400, wvantwiller
wrote:


I personally knew at least one child and one father who would be alive
today if they had been wearing helmets after they died from the trauma
of minor bicycle falls;

How do you know that?

JT

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Mostly the newspaper articles quoting the doctors that the internal
trauma would probably been prevented if the riders had been wearing
helmets. Both accidents were recent enough to have involved newer
helmets, also.

In neither case did the victim go to the hospital, but decided just to
take a nap after the fall.

And, as usual, I suppose your experience in your person medical practice,
including all that trauma room experience during your internship and
residence, give you better insights?

Also, I suppose you were there and can vouch that my other example that
I'd be a few stitch marks to the better if I had been wearing my helmet
is ALSO false?

Or do you only consider the evidence you want to?

Must be a conspiracy. Go on wearing your aluminum skullcap.

I submit that on or about Sat, 16 Jul 2005 07:52:57 -0600, the person
known to the court as Rich made a statement
in Your Honour's bundle) to the
following effect:

But you misunderstand. The torsional force is important not because
of its effect on the neck, but because of the differential movement it
causes between the hemispheres of the brain. These torsional forces
are reckoned to be a (some say the) major source of permanent
disabling brain injury.

Total BS.

Plenty of cites are available, but this will do as a quick layman's
guide: http://www.emedicine.com/radio/topic216.htm

Background: Diffuse axonal injury (DAI) is a frequent result of
traumatic deceleration injuries and a frequent cause of persistent
vegetative state in patients. DAI is the most significant cause of
morbidity in patients with traumatic brain injuries, which most
commonly are the result of high-speed motor vehicle accidents.

DAI is a significant medical problem because of the high level of
debilitation of the patient, the stress that the patient's family must
endure when the patient is in a persistent vegetative state, and the
staggering medical cost of sustaining an individual in this state. DAI
typically consists of several focal white matter 1-15 mm lesions in a
characteristic distribution (see below).

Pathophysiology: The pathophysiology of DAI first was described by
Holbourn in 1943 using 2-dimensional gelatin molds. His work led to
the understanding that shear injury is not induced by linear or
translational forces but rather by rotational forces. Sudden
acceleration-deceleration impact can produce rotational forces that
affect the brain. The injury to tissue is greatest in areas where the
density difference is greatest. For this reason, approximately two
thirds of DAI lesions occur at the gray-white matter junction.

The result of shearing forces in areas of greater density differential
is trauma to the axons, which results in edema and axoplasmic leakage
that is most severe during the first 2 weeks after injury. The exact
location of the shear-strain injury depends on the plane of rotation
and is independent of the distance from the center of rotation.
Conversely, the magnitude of injury depends on 3 factors, including
(1) the distance from the center of rotation, (2) the arc of rotation,
and (3) the duration and intensity of the force.

The true extent of axonal injury typically is worse than visualized
using current imaging techniques. On the microscopic level, the axon
may not be torn completely by the initial force, but the trauma still
can produce focal alteration of the axoplasmic membrane, resulting in
subsequent impairment of axoplasmic transport. Axoplasmic swelling
ensues, and the axon then splits in two. A retraction ball forms,
which is a pathologic hallmark of shearing injury. The axon then
undergoes wallerian degeneration. Dendritic restructuring may occur,
with some regeneration possible in mild-to-moderate injury.

Within the basal ganglia, the effect of DAI produces parenchymal
atrophy brought on by shrinkage of astrocytes in the lateral and
ventral nuclei, with sparing of the anterior and dorsomedial nuclei,
the pulvinar, centromedian nuclei, and lateral geniculate bodies.
Cholinergic neurons have been found to be slightly more susceptible to
trauma than neurons belonging to other neurotransmitters. Peripheral
lesions usually are smaller than central lesions. The lesions
typically are ovoid or elliptical, with the long axis parallel to the
direction of the involved axonal tracts. A high association is seen
between thalamic injury and DAI.

Both silver stains and beta-amyloid precursor protein
immunohistochemical staining have proven useful in the pathologic
identification of DAI lesions.

DAI classically was believed to represent a primary injury (occurring
at the instant of the trauma). Currently, however, it is apparent that
the axoplasmic membrane alteration, transport impairment, and
retraction ball formation may represent secondary (or delayed)
components to the disease process.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

85% of helmet statistics are made up, 69% of them at CHS, Puget Sound

On Sat, 16 Jul 2005 10:08:38 -0400, wvantwiller
wrote:



And, as usual, I suppose your experience in your person medical practice,
including all that trauma room experience during your internship and
residence, give you better insights?

I'm not the one making claims so I have no need to back anything up.

JT

PS -- unless the medical people you're talking about are comparing
people who fell and were uninjured, I don't see how they could come to
conclusions about helmets. Think about it.

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