Originally Posted by
jeff juel
Most people with DAI are vegetables until they die.
Really? I thought that DAI was just a description of a mechanism of axon damage that could be experienced as a spectrum of problems[1] ranging from some functional problems through to vegetative coma. The same citation also claims that DAI is more common in road-traffic accidents than simple falls (making your case rarer.)
Originally Posted by
jeff juel
I had what is called a closed-head traumatic brain injury.
I've got to say that your post reads as though you've made an incredibly good recovery. I'm glad for you.
Originally Posted by
jeff juel
I'm an engineer, so I've given this a little analysis...
The helmet effectively increased the twisting force that was spun into my brain in two ways:
1) The helmet "grabbed" the pavement better than my scalp would have. (Without the helmet, a piece of my scalp might have been ripped off. Not pretty, but it's better than a large torque causing a TBI and being a vegetable for life.)
2) The helmet increased the length of the moment arm that the friction force acted through. This resulted in a greater torque and an increased angular acceleration of my head.
My helmet resulted in a more severe twisting force being cranked into my head by the impact. I'm very confident that in my case, my helmet exacerbated my injury.
It sounds plausible, but I don't see how you can be any more confident that it's correct than the people that claim that a "helmet saved my life." On the Helmets Cramp My Style thread that closetbiker posted about one of the contributors is fond of quoting a paper by Mills et al which claims to show that the increased rotation due to a helmet is negligible[2]
Originally Posted by
jeff juel
For many or most accidents, it's likely that a helmet reduces the severity of an injury.
That's an assumption that is completely at odds with the data gathered in Australia over the past decade. There's a further problem in that you're lumping together all sorts of head injuries: it may be true that helmets can prevent tears to the scalp, but it remains to be shown that they prevent the sort of life-threatening problems you've experienced.
Originally Posted by
jeff juel
I would love to know if any of the helmet manufacturers have considered this scenario and if they have determined how frequently this type of injury happens to crashing bike riders wearing helmets.
Wow, almost reads like a viral-marketing exercise for the Phillips helmet[3].
1.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1031929/
2. Mills, N.J. & A. Gilchrist. International Journal of Impact Engineering Volume 35, Issue 9, September 2008, Pages 1075-1086
3.
http://www.newscientist.com/article/dn418-soft-hat.html