A letter of pre-determination or pre-certification from your insurance company means that a medical review department within your insurance company has decided, based on the information provided, that your surgery is medically necessary. However, this does not guarantee your insurance company will cover your surgery. The medical review department does not review the terms of your individual insurance policy. It simply determines whether or not the surgery is medically necessary. It is important for you to understand the terms, conditions and limitations of your insurance coverage. If you have questions about your coverage, contact your employer's human resources department or your insurance company directly.