Sorry to hear that you're having this problem.
In most cases where an impact hits the screen of an LCD, it breaks the liquid crystals in the panel.
Unfortunately, I'm not sure how to remove a "bruise" from an LCD screen. The panel could be replaced, but typically, that's not an inexpensive endeavor.
Plasma won't "bruise" since it's a glass panel, but I'd consult a retailer in your local (high elevation) area to get their take on how they'll work in your area.
I have a 40" Series 4 450 Model which I unfortunatly tripped and fell against, causing a moon shaped "bruise" in a portion of the picture. Most of the time, the bruise is not seen, or when seen, simply makes that portion of the screen look a bit dirty, and it can be tolerated. I'm not sure I want, however, to tolerate it.
Some questions ...
Can the "bruise" be repaired for a reasonable price?
If not, are the new LCD TVs as easily bruised?
How about LCD LEDs? Do the bruise?
I live in the mountains at 6220 feet above sea level. Should I consider Plasma TVs? Do they bruise?