Explanation:
Correct Option: A. The most critical determinant for preserving the viability of the femoral head and minimizing the risk of avascular necrosis (AVN) in a young adult with a displaced femoral neck fracture is the urgency and quality of the anatomic reduction and stable internal fixation. While capsulotomy (Option B) remains a debated topic with some theoretical benefits for reducing intracapsular pressure and restoring blood flow, extensive literature and meta-analyses have consistently demonstrated that an accurate, anatomic reduction—achieved as emergently as safely possible—plays the paramount role in re-establishing hemodynamics and preventing late osteonecrosis. Poor reduction severely disrupts the tenuous residual blood supply from the medial circumflex femoral artery. Fixation construct (Option C) affects biomechanical stability but not initial vascular insult, and postoperative weight-bearing (Option D) does not alter the initial ischemic event. (Ref: Swiontkowski et al., J Bone Joint Surg Am, 1984; Jain et al., J Orthop Trauma, 2002)