This op note is inadequate to prove that it was 3 or more parts.
Your options are to ask your surgeon to edit or amend the operative report to clarify, possibly resubmit with radiographs or CT scan confirming the number of articular fragments, etc.
I would educate your surgeon on the fact that they will routinely get denied for this unless they learn how to dictate their operative reports to the extent that they justify the appropriate code.