I may have figured out the problem... the denial you're getting "the procedure is inconsistent with the modifier used or a required modifier is missing" doesn't seem to make sense because 20553 doesn't bundle with 97710. But when I searched that denial reason, I came across a listing of denial types (from my local MAC).
The denial stating "the procedure is inconsistent with the modifier used or a required modifier is missing" falls under a denial reason/category/umbrella of "Not covered when performed during the same session/date as a previously processed service for the patient." SO, that's perhaps what they're actually trying to relay.
20553 is a surgical procedure, so mod 25 wouldn't be an option as it's only applicable to E/M services. Are the TPIs given prior to the PT? What is the purpose for them? I assume if they are done prior to the PT, the intent is to help minimize pain that would be cause by the therapy itself. If that's the case, I'd add a 59 to 20553 and appeal with documentation; you need to prove the injections were required, for medically necessary reasons. For example, if the PT wouldn't be able to be carried out without the injections because the pain would be too great and cause unnecessary suffering to the patient, that more than proves the TPIs were necessary and separates them from the procedure, if that makes sense. The documentation would have to specifically state that's the case though.
If they're being done after the PT... you could do the same thing, add the 59 and appeal, but building the medical necessity case will be more challenging. The documentation would have to state that the pain post-PT would be so intense that it would cause undue harm to the patient, or something similar.
I could be totally wrong, but it's the only thing I've found that seems to be the most logical.