Description

• Avascular (aseptic) necrosis results from the interruption of the blood supply to bone (either traumatic or nontraumatic occlusion).
• The femoral head is the most common site.
• A self-limiting idiopathic avascular necrosis of the hip that occurs in children is known as Perthes disease (see "Perthes Disease" chapter).

Pathophysiology

• Death and necrosis of bone with gradual return of blood supply
• Necrotic bone gradually resorbed and replaced by new bone
• During bone resorption, structural integrity of femoral head may be reduced, leading to collapse.

Etiology

• Traumatic
  • Slipped capital femoral epiphysis
  • Hip fracture
  • Hip dislocation
  • Complication of casting, bracing, surgery
• Nontraumatic
  • Steroids or chemotherapy
  • Malignancy (leukemia)
  • Idiopathic (older, after physeal closure); similar to adult avascular necrosis
  • Idiopathic (younger, before physeal closure, Perthes disease)
  • Caisson disease
  • Sickle cell disease
  • Septic arthritis
  • Gaucher disease
  • Viral infection (HIV, CMV)
  • Radiation therapy
  • Hypercoagulable states

History

• Onset (gradual or after traumatic event)
• Association with the following:
  • Trauma
  • Medications (steroids or chemotherapy)
  • Casting, splinting, surgery (iatrogenic)
  • Pain, limping
  • Stiffness (decreased range of motion)
  • Perthes disease may occasionally be bilateral or occur in contralateral hip at a later time point.

Physical Exam

• Gait
  • Limping
  • Antalgic ("against pain") gait (shortened stance phase relative to swing phase)
  • Trendelenburg gait (tilting of pelvis during the stance phase of gait; pelvis rises on the side not taking weight)
• Test and note range of motion:
  • Flexion and extension
  • Abduction and adduction
  • Internal and external rotation
• Hip joint irritability (short arc rotation)
• Signs of other disease processes associated with avascular necrosis (e.g., sickle cell disease)
• Physical examination pearl
  • Loss of internal rotation usually first and most affected loss of motion

Differential Diagnosis

• Trauma
  • Osteochondral fracture
  • Impaction fracture
  • Epiphyseal/physeal fracture
• Infection
  • Osteomyelitis
  • Septic arthritis
• Neoplastic process: epiphyseal tumors (chondroblastoma, Trevor disease, etc.)
• Rheumatologic processes
• Skeletal dysplasia, particular if bilateral hip involvement

Diagnostic Tests & Interpretation

• Laboratory examinations should be normal in most forms of avascular necrosis of the femoral head.
• Exceptions:
  • Sickle cell disease
  • Septic arthritis
  • Chemotherapy
• Radiographic findings:
  • Sclerosis
  • Subchondral fracture
  • Collapse
  • Reossification
  • Repair
• Magnetic resonance imaging (MRI)
  • Bone edema
  • If contrast medium used, area of reduce blood flow evident
• Bone scan
  • Reduced signal in affected hip
• Other potential findings:
  • Cysts
  • Physeal growth arrest (young)
  • Early osteoarthritis
  • Subluxation

Medication

• NSAIDs may reduce pain by decreasing associated inflammation but may also reduce new bone formation.
• If associated with corticosteroid use, discontinuation or elimination of steroids may be helpful.
• Antiresorptive therapy (bisphosphonate/receptor activator of nuclear factor-κB (RANK) ligand inhibitor) may reduce pain and preserve joint shape; research studies using this approach are ongoing.

General Measures

• Maintain range of motion (physical therapy, traction, continuous passive motion).
• Contain the femoral head in the acetabulum (see treatment principles listed in "Perthes Disease" chapter).
• Duration of therapy variable, depending on cause
• Reduced weight bearing on affected hip may help prevent collapse.

Surgery/Other Procedures

Redirectional osteotomy

• Femoral or acetabular reorientation
• Core decompression to stimulate new blood supply

Diet

• Thought not to alter disease process
• Recommend general balanced diet.
• During immobilization, excessive weight gain may occur.

Prognosis

• Depends on extent of femoral head collapse
• Good if mild involvement and patient is young
• Timing of improvement is variable, dependent on etiology.
• Moderate to severe cases often have significant collapse and end up requiring a total hip replacement.

Complications

• Joint collapse with decreased range of motion, pain, limping
• Osteoarthritis
• Physeal arrest with growth disturbance

ICD9

• 733.42 Aseptic necrosis of head and neck of femur
• 732.1 Juvenile osteochondrosis of hip and pelvis

ICD10

• M87.059 Idiopathic aseptic necrosis of unspecified femur
• M91.10 Juvenile osteochondrosis of head of femur, unspecified leg
• M87.052 Idiopathic aseptic necrosis of left femur
• M87.051 Idiopathic aseptic necrosis of right femur
• M91.11 Juvenile osteochondrosis of head of femur, right leg
• M91.12 Juvenile osteochondrosis of head of femur, left leg

SNOMED

• 444904004 aseptic necrosis of head of femur (disorder)
• 111255008 Avascular necrosis of the capital femoral epiphysis (disorder)
• 15739006 Juvenile osteochondrosis of hip AND/OR pelvis (disorder)