Yeah, my doctors at the hospital say, don't you remember tackling me and 3 others?

I'll tell you one thing, never try to subdue or hold down somebody who is having a tonic conic seizure

How do they go about breaking, tension, flashing around uncontrollably?

My rotator cuffs are ruined from bad seizures. I've also broken my left elbow and 4 fingers. If I wasn't afraid of anesthesia I would definitely get my shoulders fixed.

I damaged one of my shoulders in highschool due to a seizure. I tried physio for it, but than I'd have a seizure.
My seizures are a bit better now... but I think my shoulder has been sitting to long.
Talk to your doctor and surgeon. They're the one's you need to talk to. If a surgery is plausible for your son you'd be talking to them about recovery time, and how you should respond during a seizure if/when he has one. If it's to much of a risk... he wouldn't be able to get this surgery.