Kaplan-Meier analysis shows local recurrence-free survival (LRFS) of patients with osteosarcoma using the Birmingham classification. Birmingham 1a (≥ 90% chemotherapy necrosis, > 2-mm margins) 99% 5-year LRFS (95% CI, 91%–99.8%). Birmingham 1b (≥ 90% chemotherapy necrosis, ≤ 2-mm margins) 92% 5-year LRFS (95% CI, 83%–96%). Birmingham 2a (< 90% chemotherapy necrosis, > 2-mm margins) 84% 5-year LRFS (95% CI, 73%–91%). Birmingham 2b (< 90% chemotherapy necrosis, ≤ 2-mm margins) 76% 5-year LRFS (95% CI, 77%–83%).