Your posts are confusing to us as you originally state bilateral trigger injections into the leg, now you are stating bilateral muscle injections into the back, regardless, the location doesn't matter so much as how many muscles were given trigger point versus just an IM injection. If you take the "bilateral" out of your thought process and just add up the total number of muscles you will successfully code this correctly. Originally you told us that a total of 4 muscles are injected, so your CPT code should be 20553, not 20552-50 and definitely not x 4 units. These codes are limited to 1 unit on a claim for a single DOS. But if you only did trigger point injections into 2 muscles TOTAL use the 20552.
Trigger point injections:
20552 use for 1-2 muscles anywhere on the body, leg, back, shoulders, neck etc.
20553 use for 3 or more muscles (whether 4, 5, 6, 7 etc)
Note: NOT to be billed bilaterally - mod-50 is incorrect/inappropriate
You would use the IM injection 96372 each time drugs were administered, either by drug or combination of drugs. Most importantly, you cannot bill a 96372 for a 2055X drug administration at the same site, it must be at a different site to apply the modifier 59 to the 96372. Based on my experience 96372 has an invisible unit limit of 3 per DOS and then records need to be sent with the claim to support more.
It is best to always share the actual procedure note verbiage so that we can see the whole picture.
Per this post information, this is the correct coding without reviewing the procedure note:
2 on each side in the multi-fidus and iliocostalis, IM injection of two additional drugs.
4 muscles total = 20553 (No modifier)
96372 x 2 - 59 (Toradol, Decadron)