I agree that that day of surgery is not considered post-op and if the only care the surgeon provided was on the day of surgery, you would just bill with the -54 and be done.. But, if the post-op period itself is split between surgeon and regular doctor, this is what Medicare instructs. Per North Carolina's MAC website (Palmetto GBA):
http://goo.gl/9GMuL
Surgeon: Dr. X
Date of Service CPT Code / CPT Modifier Place of Service Quantity Item 19
1/07/2012 66984-54 24 1 Blank
1/07/2012 66984-55 24 '10' "Care relinquished to Dr. Y on 1/17/2012"
Physician to whom care was transferred to: Dr. Y
Date of Service CPT Code / CPT Modifier Place of Service Quantity Item 19
1/07/2012 66984-55 24 80 "Care assumed from Dr. X; 80 days to follow 1/18/2012"
This of course all depends on if, when, and how the post op care is split, but is one example of how you could potentially be required to bill both the surgery and the post-op care on the same day.
I hope we hear back from Lizzy; it'll be interesting to know the details. Until then this is all an interesting theoretical exercise.