Is my hair loss reversible?

When I was little I had a serious neck injury that required me to wear a few different halos before finally getting surgery. One of the halos I had to wear had a part that rested on the back of my head, and frequently rubbed my hair, eventually leaving a bald spot. It was usually pretty easy to hide since I've always had long hair, but there were certain hairstyles I couldn't wear or had to modify so that it wouldn't be visible. I don't know why my parents never looked into getting it fixed, but I don't want to have to worry about it being seen anymore. My only concern is that I know certain types of baldness are hard to correct and I don't know if the fact that I've had it for several years would make it harder to fix. Any information on this would be greatly appreciated.