Avascular Necrosis of the Femoral Head

Aka: Avascular Necrosis of the Femoral Head, Hip Avascular Necrosis, Hip Osteonecrosis, Hip AVN

1. See Also
   1. Hip Pain
   2. Hip Pain Causes
   3. Leg-Calve-Perthes Disease
2. Epidemiology
   1. Incidence: 20,000/year in United States
   2. Most common in men ages 30-50 years old
   3. Leg-Calve-Perthes Disease is idiopathic osteonecrosis of the femoral head in children ages 2-12 years old
3. Risk Factors (compromise femoral head blood supply further)
   1. Most significant common cases denoted (*)
      1. Pregnancy
      2. Chemotherapy
      3. Radiation Therapy
      4. Sickle Cell Anemia
   2. Hematologic Causes
      1. Coagulopathy
      2. Sickle Cell Disease (*)
   3. Gastrointestinal Causes
      1. Chronic Liver Disease
      2. Chronic Pancreatitis
   4. Rheumatologic Causes
      1. Gout
      2. Systemic Lupus Erythematosus
   5. Medication, substances and exposures
      1. Chemotherapy (*)
      2. Radiation Therapy (*)
      3. Alcohol Abuse
      4. Systemic Corticosteroids
      5. Tobacco Abuse
   6. Lipid Disorders
      1. Hyperlipidemia
      2. Gaucher Disease
   7. Miscellaneous Causes
      1. Diabetes Mellitus
      2. Pregnancy (*)
4. Pathophysiology
   1. Femoral head subchondral bone with irreversible anoxia
      1. Results in secondary osteocyte death
      2. Osteoblasts are active in surrounding bone
   2. Subchondral trabeculae fails and result in collapse of Hip Joint space
5. Symptoms
   1. Progressive Groin Pain or Hip Pain, gradually increasing over weeks to months
   2. Starts unilaterally (but ultimately bilateral in over 70% of cases)
   3. Radiation into medial thigh
   4. Provoked with weight bearing (especially while standing with all weight on affected leg)
   5. Pain at rest suggests advanced avascular necrosis
6. Signs
   1. Hip Range of Motion
      1. Normal initially
      2. Later significantly limited active and passive range of motion due to joint destruction and collapse
7. Differential Diagnosis
   1. See Hip Pain
8. Diagnosis
   1. Typically delayed diagnosis until advanced stages (due to insidious, gradual presentation)
9. Imaging
   1. MRI Hip (preferred)
   2. CT Hip
   3. XRay Hip (first-line, initial study)
      1. Stage 0 and 1: Normal XRay
      2. Stage 2: Hip sclerosis, bone cysts and Osteopenia
      3. Stage 3: Crescent sign
         1. Femoral head flattening of the superior aspect
         2. Subchondral Fracture parallel to articular surface
      4. Stage 4: Femoral head collapse
      5. Stage 5-6: Joint destruction
10. Management
    1. Orthopedic referral
    2. Non-Sickle Cell patients
       1. Hip replacement in nearly all cases
    3. Sickle-Cell patients
       1. Conservative management with focus on pain relief and mobility, physiotherapy
       2. Surgery is rarely indicated in Femoral Head AVN in Sickle Cell Anemia
11. Prognosis
    1. Responsible for 12% of all hip replacements in the United States
12. References
    1. Shahideh (2013) Crit Dec Emerg Med 27(9):10-18
    2. Welsh and Welsh (2016) Crit Dec Emerg Med 30(11): 15-23