Case: We report 2 cases of Loder-unstable slipped capital femoral epiphysis (SCFE). Both patients had initial pinning followed by surgical hip dislocation where complete avulsion of the lateral epiphyseal vessels from the nutrient foramina was identified. Both patients underwent epiphysiodesis to revascularize the femoral head but developed osteonecrosis with collapse 9 months after their injury. Conclusion: Avulsion of the lateral epiphyseal vessels currently represents a nonreversible mechanism of avascularity in SCFE. Although Loder previously theorized the existence of this mechanism, it has never been clinically identified and there are no surgical techniques proven to prevent osteonecrosis in this variant.