Was the hamburger unfit for its ordinary purpose?

Fred Goodman and a friend stopped for lunch at a Wendy’s restaurant in Hillsborough, North Carolina. Goodman had eaten about half of his double hamburger when he bit down and felt immediate pain in his lower jaw. He took from his mouth a triangular piece of cow bone, about one-sixteenth to one-quarter inch thick and one-half inch long, along with several pieces of his teeth. Goodman’s pain was intense, and his dental repairs took months.
The restaurant purchased all of its meat from Greensboro Meat Supply Company (GMSC). Wendy’s required its meat to be chopped and “free from bone or cartilage in excess of 1/8 inch in any dimension.” GMSC beef was inspected continuously by state regulators and was certified by the United States Department of Agriculture (USDA). The USDA considered any bone fragment less than three-quarters of an inch long to be “insignificant.”
Goodman sued, claiming a breach of the implied warranty of merchantability. The trial court dismissed the claim, ruling that the bone was natural to the food and that the hamburger was therefore fit for its ordinary purpose. The appeals court reversed this, holding that a hamburger could be unfit even if the bone occurred naturally. Wendy’s appealed to the state’s highest court.