It depends on where the medical records were generated. In Georgia(USA) medical records should be kept on file at a physicians office for at least 10 years after the last visit.
In a hospital setting, medical records must be kept on file for 6 years past the last visit. However, in either instance, if the patient experienced a bad outcome(they died, or had something happen out of the ordinary) like a "re-operation", the custodian of the records should keep them indefinitely.
The medical records of minor children must be kept until the child reaches 27 years of age. Present day health-care facilities commonly convert paper records to an electronic format to facilitate record keeping.