I was working my 4 year old Appaloosa gelding in an arena. He was feeling quite frisky and energetic that day. The best thing to do with him when he's feeling like that is to give him a job. The first of my mistakes was to give him a job: I took him over 3 trot poles that were at a 45 degree angle to the wall. He decided to jump the middle trot pole (and just that trot pole). In the middle of that jump he bucked, which caused my second mistake: I fought to keep my seat instead of letting myself off his back on my own terms. Once he landed, he took off at a fast canter and/or a gallop down the wall of the arena. When he took off, I was leaning hard right, and managed to pull myself back into seat somewhat.
The rest is somewhat blurry to me, but here it is as I remember it: -I was leaning over the wall of the arena -I looked up and saw one of the girders supporting the roof of the arena (I-beam shaped, with a curve to it moving up to an arch in the top middle of the arena) - I leaned into the arena slightly and ducked my head -Falling with my arm scraping along the wall on the way down (I have a scar from the abrasion) -I was dragged for 10-15 feet with my foot caught in the right-hand stirrup (wall side) -Lying there for a moment before getting up to my knees I was concussed as... Well, suffice it to say, I had a pretty decent concussion. I wrestled in high school and played lacrosse in college, and this is the most severe concussion I've ever had, and I've had a few.
My helmet hit the edge of that steel I-beam and left a black mark there where it hit. I ended up backboarded and taken to the hospital. CT scan showed that I only had a sprained neck, thank God. It took a couple of weeks to get over the neck pain, but, without a helmet, I wouldn't have even had a chance to have any neck pain. 4 inches lower and I would not even have the chance to write this. That's not even to mention the likelihood of what would have happened if I hadn't been wearing a helmet.
Thank you, Troxel, for building helmets to the quality that you do. The picture involved here was taken in the Emergency Department. The cracks are just on the right hand side of the vent. The picture doesn't show them very well, but they're about 2 mm deep in separation between the two sides of the crack on the immediate right of the vent. From there, they move to 1 mm deep and more shallow the farther they get from the crack in a slope. I got lucky. Wear your helmet.