@PaulSim
Yes, I can identify with your struggles. I, too, had SCFE as a youngster (I was 13 when I had both hips pinned) and unfortunately, I always had residual hip problems following the surgery. The hip-pinning surgery just stabilized the slips; it didn't reposition the hips into the correct anatomical position, therefore, my hip anatomy was always abnormal. The ball portions of both hips were misshapen and distorted, with the right hip (the bad one) being the most deformed.
My right hip was a severe slip, and my left hip was a moderate slip -- but both hips were always stiff and problematic. Growing up, I never had normal hip mobility; my hips were always restricted, and my gait was a bit awkward, with my feet tending to splay outwards as I walked. And although I led a very active lifestyle and didn't have to really avoid anything per se, I never felt normal physically and always felt restricted and a bit awkward while engaging in various physical activities; I simply couldn't move or bend or pivot or twist normally, and that made being an athlete (or just a hyper-athletic person) somewhat difficult.
I also had chronic pain over the years related to my altered hip biomechanics. This pain problem was a fixture of my life all through my late teens, 20s, 30s, and now into my 40s; I've been in some type of pain pretty much since about age 17 or thereabouts. I had two or three excellent years following the hip-pinning surgery where I had zero pain, but after that, the pain started. The pain was mostly lower leg pain (knee pain, shin pain, ankle pain) along with lower back stiffness and right leg weakness (my right leg was always underdeveloped and weak relative to my left leg, and this imbalance greatly contributed to my overall awkwardness). But now into my 40s, my lower back pain and stiffness has increased, and my hips are stiffer than they have ever been, to the point where I frequently wake up in the morning walking around like Frankenstein, all stiff and immobile. It generally takes several hours for me to loosen up.
My goal is to have my right hip replaced later this year at HSS in New York City. My right hip has degraded enough and is sufficiently arthritic to warrant hip replacement, so I think that this year is the year to finally start fixing these problems that have been dogging me all these years. I've suffered a lot emotionally and psychologically over the years because of my hip problems (and because of the limitations that they have imposed upon my life), and I'm hopeful that I can alleviate much of that while regaining a high level of physical activity. Because my athletic capability has shrunk significantly over the last several years, and I'm increasingly becoming more sedentary, which I don't like.
Good luck to you in your journey, and I hope that you find a good solution to your hip problem. As long as you select an experienced, competent surgeon, you should have an excellent result. And the chances are high that your hip replacement will last a long time, as the newer plastics and ceramics in use nowadays are highly durable and long lasting.