I have a pain doctor that performed an RFA on the L5-S1 and S1, S2, S3. Which I know would be the 64635, 64636. However, on the 2nd & 3rd levels, the procedure wasn't completed. It says it was attempted but was unable to perform (no documentation as to why). Would the 64636 be billed with the 53 modifer? The provider did not mark this for coding.