I worked at a hospital as my summer job during undergrad and you see lot of people that get into accidents and have to get surgery, but their body for w.e reason couldn't cope so they get an infection which eventuall leads to amputation ( lot of variables but main ones were the patients age, medical background, and seviriety of the accident ). I still remember one grandma that got hit by a car in her leg and had to get surgery, and for couple of weeks she seemed to be fine + had a good relationship/was friendly with the ICU team, but her leg got an infection or something and she had to get it amputated. I am not sure what happened at the end but she went through some mania/depression cycle and then eventually passed away ( her family visited her frequently + her husband always sat next to her for like 8 hours a day/7 days a week so that was pretty sad to see ).
But besides that I feel the chances for amputation for LL is really low since it's a very controlled surgery that's planned months/years ahead. If you are young, healthy, and go to a reputable surgeon with good track record/surgery center you should be fine.