Explanation:
Intracapsular femoral neck fractures disrupt the retinacular vessels supplying the femoral head. These vessels arise primarily from the medial femoral circumflex artery. Disruption can compromise blood flow and lead to avascular necrosis. The risk increases with displacement of the fracture. Early surgical fixation or arthroplasty is often required. Prompt treatment improves outcomes and reduces complications. Reference: Garden RS. "Low-angle Fixation in Fractures of the Femoral Neck." Journal of Bone and Joint Surgery, 1961.