If the change is due to a risk to the patient, you should consider issueing a field safety corrective action - FSCA do not have to just be recalls, they can be for informational purposes as well i.e. IFU updates. Certainly within the UK the MHRA distributes to hospitals and the hospital should communicate to the relevent parties.
Additionally, as advised in previous posts, most implantables I've worked with have sales reps attend theatre and advise the surgeons on appropriate techniques...The sales reps will know all the surgeons using your products, should have a good relationship with them and should be in a position to communicate changes to them.