Your 401k or 403b plan for your retirement may allow you to take a loan against the funds that you have already saved without a penalty. These plans differ from employer to employer, but most will allow you to withdraw 50% of your vested balance up to $50,000.
The length of time allowed for repayment varies, but if you leave your place of employment before you repay the money there can be substantial tax penalties. You will lose the interest you would have earned on the money you withdraw, but you will not be paying interest on the loan as you would with traditional borrowing.
If you have a Roth IRA, you may be able to access the funds to pay for your surgery. Typically a Roth IRA is not managed by employers, but by individual investors, so you may have to do your own research. Start by calling the customer service number for your fund and inquire about taking money out of the IRA before retirement age.