This one discusses limiting procedures per year. Apparently in one example a surgeon could do 4000+ safely with a lead apron and only 300 without one. https://insights.ovid.com/crossref?an=00007632-201304010-000...
There appears to be plenty more material out there relating to this.
Ul Haque M, Shufflebarger HL, O'Brien M, Macagno A. Radiation exposure during pedicle screw placement in adolescent idiopathic scoliosis: is fluoroscopy safe?. Spine 2006;1;31(21):2516-20.
I know about it from here: https://www.nuvasive.com/solutions/lessray/