I'm not sure the universe of fusion surgeries is going to be AT ALL relevant to your son's situation. I don't even think the non-Chiari fusions (i.e., AIS, Marfan's etc.) in kids are necessarily relevant but what do I know?
What will be most relevant are surgeries for Chiari done with modern instrumentation at a particular bone age.
Sharon, mother of identical twin girls with scoliosis
No island of sanity.
Question: What do you call alternative medicine that works?
"We are all African."