Normally, it's probably not a good idea to get any kind of skin treatment, including tattoos, right before surgery. This is because these treatments compromise the quality of your skin, essentially "damaging" it and making it more sensitive—and your skin (and body) should be in its best state so that it can recover better from your surgery. Being in a better state also decreases the risk of complications that could occur, such as infection. Having said that, however, if it's far away from the treatment area, like on your ankle, and it's small, then it might be okay. But keep in mind that your surgery may be postponed if you suffer from a complication related to getting the tattoo. The best thing you should do is to ask your surgeon about this. Best of luck!