With the score level at 44-44, Touya and Keeth Smart lunged simultaneously. The American's sabre cut through the webbing around the knuckles of the Frenchman's glove.
The blade emerged through his palm, leaving Touya in considerable pain. After a 10-minute time-out, he bravely pulled on his glove and after two further simultaneous attacks that kept the scores tied, he finally produced the hit that sent his team into the final against Italy.
"It showed great courage for Damien to make that last play as he was in terrible pain," said French coach Christian Peeters who toyed with the idea of using the reserve Boris Sanson to complete the match.
"It was very difficult for our nerves but in the end I wanted to listen to Damien. In the end it is the fencer who has the last word and he wanted to carry on. He was formidable."
Whether Touya will be available to join his brother Gael and Julien Pillet for the final later on Wednesday will depend on how his hand responds to medical treatment.
"We will see," said Peeters.
Even before the injury it was a classic team match with Smart pulling the Americans back from 42-44 down to level the score.
There was similar drama in the other semi-final where Italy had to rely on their last fencer Luigi Tarantino coming from behind to beat Russia, the defending champions, 45-42.