Which artery provides the primary blood supply to the adult femoral head and is at greatest risk of disruption in a displaced femoral neck fracture?

Explanation:
The medial femoral circumflex artery (MFCA), specifically its lateral epiphyseal branch, provides the predominant blood supply to the adult femoral head. Its disruption is the primary cause of avascular necrosis following a displaced femoral neck fracture. Reference: Rockwood and Green's Fractures in Adults.