About 150 people received notices last February informing them they should undergo tests as a precaution.
The McGill University Health Centre's medical director of infection prevention, Dr. Charles Frenette, told CBC News that 89 per cent of the patients have responded to the notices, and all have tested negative.
The hospital is trying to track down the remaining 11 per cent of patients to ensure they get tested.
Frenette said a routine review of cleaning and sterilization procedures found that the tool hadn’t been completely disassembled during past cleanings.
The tool — a liver retractor — is used to lift the liver to allow the surgeon a better view of the stomach.
Frenette said surgical debris was discovered in a connection point that hadn’t been unscrewed.
“It might have been old dust. It could have been old blood, which is why we recalled all the patients,” he said.
The risk of infection was minimal, said Frenette.
“But in circumstances like that, we take no chances and do a recall,” he said.
Health Canada and Montreal’s public health agency have also been notified of the problem to ensure other hospitals are made aware of the proper cleaning procedure for the tool.