If you really want to let your horse graze this is a 2 step process.
FIRST, train with a tying ring, like Clinton Anderson and Julie Goodnight sell. http://downunderhorsemanship.com/sto...G-LOK%20CHROME Goodnight
Get your horse SO WELL VERSED to being tied, like about one year of reliable tying, that you can trust him. Then...
SECOND, get a picket pin. http://www.relicman.com/miscellaneou...ous/M0792A.JPG Ridgeway Reference Archive* Horse equipment, picket pin
FYI: Florida Reenactors Online--Cavalryman's Accoutrements
This sutler sells them for $50.00 Civil War Saddles & Tack
Picket Pin - Civil War $50.00
You can call Fall Creek Sutlery, but need to get an online catalog or pay $6 for a printout version.
We used them many, many times over the years when we went to CW Events (for 26 years) and on vacations. The rope needs to be at least 15 ft. long, preferably 25-30 ft. The pin is pounded into the ground and the rope is attached to a ring that swivels, and this sits a few inches above ground. Your horse will chew a circle in the grass, then you can move it. We would picket them for an entire weekend, when we weren't trail riding.
IF your horse panics--I cannot be there to train her, so I don't know--when she catches a foot she might get a rope burn on the back of the pastern, but not as badly as you
I've done your accident one better. When "Beaner", who had tying problems and also threw me and broke my arm in 2004, was tied to my power pole in the area in front of my barn, he panicked and pulled down the rotten pole INCLUDING the power lines to my barn. I had two of my best horses tied out. How NOBODY was electrocuted, I'll never know.
Since then I've had my lines from the house buried.