It is always important to wear your protective gear and to know your limits while rollerblading. We see a lot of wrist fractures from rollerbladers that aren't wearing wrist guards. He is very concerned about needing hip replacement surgery, but feels that this could be problematic because he is so young. There is no specific age requirement for hip replacement surgery. Depending on what the problem is you can consider other options.
Some people have hip fusions.
But if it is both hips, that wouldn't be a good option. Fusion is when the bones are fused together and there is no motion at the hip joint. The hip replacement is where you actually replace the joint with metal and plastic. I still have a substantial bump on that kneecap. It is extremely painful to kneel on that side.