If the surgery was to treat an illness or defect in the body, and not primarily for cosmetic purposes, the portion of the costs not reimbursed by your insurance would be a deductible medical expense. Please keep in mind you can only claim as itemized deductions
the amount of medical expenses that exceed 10% (7.5% if you are over age 65) of
Adjusted Gross Income.
The following guidance is taken from IRS Pub. 502 Medical and Dental
Expenses:
"Medical expenses are the costs of diagnosis, cure, mitigation, treatment, or prevention of disease, and the costs for
treatments affecting any part or function of the body.
These expenses include payments for legal medical services rendered by physicians, surgeons, dentists, and
other medical practitioners. They include the costs of
equipment, supplies, and diagnostic devices needed for
these purposes.
Medical care expenses must be primarily to alleviate or
prevent a physical or mental defect or illness. They don't
include expenses that are merely beneficial to general
health, such as vitamins or a vacation."
"Generally, you can't include in medical expenses the
amount you pay for unnecessary cosmetic surgery. This
includes any procedure that is directed at improving the
patient's appearance and doesn't meaningfully promote
the proper function of the body or prevent or treat illness
or disease." [Emphasis added.]