Avascular Necrosis (Aseptic Osteonecrosis).

Avascular necrosis (AVN), also referred to as aseptic osteonecrosis (AO), can develop in several osseous districts of the body. Most commonly described is avascular necrosis of the femoral head (AVNFH), a debilitating and progressively disabling condition with partially understood, wide-ranging etiology and pathogenesis. Pathology is chiefly caused by a reduced vascularization of a terminal vascular bed, such as the one perfusing the femoral head, or similar vascular distributions such as femoral condyles, humeral head, the talus, the calcaneus, the navicularis, and other bony structures. Hypoxic conditions mediate the condition and can improve with a course of hyperbaric oxygen (HBO₂). The Ficat classification is one of the most widely used staging systems for AVN of the femoral head. It classifies patients with osteonecrosis into four stages based on the appearance on a plain radiograph, at least before the advent of MRI, the ultimate golden standard for the specific case. I- Pain but no radiographic anomalies II- Increased density, cystic changes, or porosity III- Flattening of the femoral head and crescent sign IV- Full collapse of the femoral head with decrease in joint space Many of the treatment options proposed aim to achieve joint preservation. However, when the radiological signs progress to advanced bone collapse in the articular capsule, the single mandatory surgery approach is a femoral head replacement with total hip arthroplasty (THA).