can I be replaced

[genia]

I work for a School system in Louisiana. I was tripped at work by a student by accident in March of '08 and now have a neck injury. No lawyers are involed. After many Doctors & appointments my long awaited surgery should be in a couple of weeks on my neck I will finally be able to go back to work after 16 months. When I went to give them another update I was told that my position is being filled. That you only have one year to get fixed and return are someone is hired to fill it. Is this something they can do? I was in my postion for about 15 years.