The Lachine Hospital says about 150 patients received a letter last February suggesting they get tested.
The tool in question was a liver retractor and officials are describing the sterilization procedure as "incomplete."
Roughly 89 per cent of the 150 patients have been tested and all came back with negative results.
Dr. Charles Frenette says the hospital is doing what it can to find those patients who haven't yet been tested.
The hospital is part of the McGill University Health Centre and is one of the few places in the city where such a procedure is performed.