Welcome. I am sorry to hear about your son but glad you found this site. You'll get a lot of support here.
I don't know much about the congenital form of scoli but I'd recommend that you see a pediatric scoliosis specialist if you are not already. Not a general orthopedist. Consider getting a second or third opinion. A great doctor will welcome a second opinion. We live in Southern CA and see Dr Peter Newton who is wonderful and we'll be seeing Dr. Betz and his team in Philadelphia for a consult in a few months. Via email and mail contact with the Physician Assistant at Shriners in PA, Janet, she was glad to review my daughter's records long distance.
Also, just my gut reaction, 2 cm leg length discrepancy seems like a significant difference that it deserves to be addressed too. Worth following up on that as well.
Best Wishes. You are not alone!
Resilience
treated w Milwaukee Brace FT for 3 yrs
currently 46 with 35 LL and 40 RT curves
8 yr old diagnosed w Scoli 8/10 with 27 LL and 27 RT
11/10 TLSO Full Time
4/11 22 LL and 24 RT on waiting list for VBS at Shriners Phila
12/11 curves still in the 20s but now has some rib cage changes from the brace
VBS 4/25/12 with Dr. Samdani. Pre Op: 29 RT and 25 LL Post Op: 17 RT and 9 LL
10/13: 15 RT and 10 LL