Ah, the good old trephination debate. I have tried this both ways. The 29999 rarely (if ever) gets paid even with the op report and explanation of why it's being reported. Trying to do both just delays payment and causes records requests which ultimately get denied anyway for a generally "easy to pay" surgery one-liner. I would report 29881 since meniscectomy was performed. The trephination would be included in that in my view. It seems it's just an additional technique used while in there to promote healing. Was it really that much more work (while in there for 29881) to justify an additional 29999?
If the only thing performed was the trephination you would have to report the unlisted. But, in this case, I wouldn't.