A 65-year-old man with a history of chronic alcohol abuse and poor nutritional status presents with a displaced intracapsular fracture of the femoral neck (Garden grade III). He is medically fit for surgery. At 6 weeks post-operatively following internal fixation with three cannulated screws, he develops severe groin pain and progressive loss of hip abduction strength. Radiographs show lucency around the screw heads with evidence of femoral head collapse. Which of the following is the most likely explanation for this complication, and what is the primary mechanism underlying its development?