With a WC claim , much of it is in the details, was a fall or hit to the back recorded & reported at the time of the claim filing?

If not it would need to be added to the claim, but is usually only successful if you had no prior back injury. Possibly it could be added as an aggravation by the original injury(concussion).

Depending on the details and how the injury occurred, or if the back didn't hurt before and is now starting too..
\like with whiplash , often it begins to hurt after the fact, sometimes much later.

Do you have a wc atty representing you?
Do you have your own dr providing care & treatment?
With complicated claims , multiple injuries you really need a atty on your side.

I know state laws/rules differ, so maybe the wc system where you are is not the same as I experienced.

I was able to use my own dr (approved by wc) and my dr rx'd the treatments /therapy, restrictions/time off etc and wc (& employer) accepted it or denied it.

At one point I did go on a cash basis , no ins forms or paperwork - outside of the wc system -to get some help from a expert chiropractor & an evaluation/helpful suggestions from an adv PT person, as I was not seeing much improvement with only wc allowed limited PT.

Some wc attys have suggested drs lists that tend to be helpful for injury/claims.