My lower back. I had already had 2 surgeries there - first time was a bone fusion because I had spondylolistheses and Harrington Rods were new-ish and my surgeons were 'so excited'. That was a disaster: one rod broke in half. The next surgery roughly 10 years later, involved the doctor trying to remove the rods but they were so embedded in bone that he only got out half of one. He then added 6 screws to stabilize things. That didn't help either.