Olisthetic scoliosis in a 13-year-old girl with sacralization of L5 and a pain-free 12% isthmic slip at L4. A) Cobb angle 26 degrees, Boston brace treatment started. B) Scoliosis progression to 44 degrees despite brace treatment, no slip progression. C) Instrumented posterolateral fusion of L3 to L5. The lateral tilt of L3 was fully corrected. D) A satisfactory result is seen 27 months after the operation: the Cobb angle is 24 degrees, fusion is solid, and implants are removed. The patient is free of symptoms.