"Knee surgery - wrong parts?"

I have been attending this hospital for over a year with a knee injury.   I need an operation but this has been cancelled three maybe four times.   In June this year I was booked in for the surgery and was in the operating room when the surgeon cancelled the operation.   When I asked what was going on I was told that they had ordered and received the wrong parts for my knee surgery? ?   I put in a complaint to the health board and I had a meeting last week with the surgeon, who blamed the new registrar for ordering the wrong parts - but how could this happen? how come they were not checked earlier?   I now have a possible future date for my operation in October.   Advised by a nurse to share my story.