Final answer:
Without the proper context from 'Gifted Hands: The Ben Carson Story,' it is not possible to accurately describe the most harrowing moment of the surgery for Patrick and Benjamin as per Ben Carson's account.
Step-by-step explanation:
In Gifted Hands: The Ben Carson Story, Dr. Ben Carson describes the surgery of conjoined twins Patrick and Benjamin Binder as an extremely delicate and risky procedure. The most harrowing moment of the surgery, according to Carson, might involve the point at which both their lives hung in balance, and any slight miscalculation could result in severe consequences. The exact details of this 'most harrowing moment' are not provided in the quoted text, which instead seems to be excerpts from different contexts and does not directly reference Carson's account of the Binder twins' surgery. Therefore, we cannot accurately convey what Dr. Carson identified as the most harrowing moment without proper information from the book.