Can you tell me if it's ever too late to undergo surgery to fix a congenital hand defect?

Probably ok: Most likely, reconstructive surgery can be performed at any age. Speak to a plastic surgeon who specializes in hands for a more complete answer.

Congenital hand: While it is never "too late" to offer treatment, the avenues that are open to a one year old may not be suitable for an adult. Find a hand surgeon that cares for children and adults who has experience treating congenital problems AND problem of adults, get a few opinions and weigh your option carefully, You have had a lifetime now to establish certain use patterns and may not want to change