Pictured above is the oldest surviving prosthetic. Found in the necropolis of Thebes near modern-day Luxor, this prosthetic constructed of wood and leather is 3,000 years old. Testing was conducted as to whether the find was a functional prosthetic or merely a cosmetic fix; the determination was that it served as the former. See this article for 15 other examples recognized as the oldest surviving items of their type.
Image: BBC.com.