Avascular Necrosis and Legg-Calve’-Perthes Disease

Avascular Necrosis (AVN)

• Can occur as a complication of a femoral head or neck fracture.
• If not related to a fracture, it typically affects individuals between 20 and 50 years old.
• The cause is often unknown but is more common in men and frequently affects both hips (bilateral).
• After initial tissue death (infarction), the femoral head collapses, fragments, and heals with deformity, leading to osteoarthritis.

Legg-Calve’-Perthes (LCP) Disease (Coxa Plana)

• A self-limiting disorder characterized by degeneration of the femoral head due to disrupted blood supply (avascular necrosis).
• A portion of the femoral head undergoes avascular necrosis, causing the weight-bearing surface to flatten (coxa plana).
• The necrotic bone is eventually reabsorbed and replaced by new bone.
• The cause is unknown but may be related to trauma, genetics, inflammation of the joint lining (synovitis), vascular abnormalities, or infection.
• Four times more common in males than females, typically affecting children between the ages of 4 and 8.
• A long-term complication is osteoarthritis due to the uneven joint surfaces.

Stages of Legg-Calve’-Perthes Disease

• Condensation/Necrosis: The femoral head's blood supply is disrupted, leading to inflammation, stiffness, and pain. This stage lasts for several months to a year.
• Fragmentation: The body removes dead bone cells and replaces them with new bone cells. The joint remains stiff and painful. This stage lasts for 1-2 years.
• Re-ossification: Blood supply is restored, allowing new bone growth. This stage lasts for 2-3 years.
• Remodeling: Normal bone replaces new bone cells. The femoral head may become mushroom-shaped or flattened (coxa plana).

Clinical Features of Legg-Calve’-Perthes Disease

• Gradual onset of symptoms.
• Painful walking, leading to an antalgic gait (a limp).
• Pain relieved by rest.
• Positive Trendelenburg sign (due to weakness of the gluteus medius muscle).
• Decreased range of motion in the hip joint.
• Pain at extreme movements.
• Tenderness over the front of the hip.