Osteonecrosis of the Hip

February 7, 2021 | By : OrthoFixar | Reconstruction
| Last updated on February 15, 2021


  • Osteonecrosis of the Hip is a progressive disease that is a result of a loss of circulation to the femoral head from numerous potential causes.
  • Formerly referred to as avascular necrosis, the term osteonecrosis is now preferred.
  • Osteonecrosis means “dead bone”.

Epidemiology

  • 20,000 new cases of osteonecrosis of the hip are diagnosed each year in the United States.
  • 18% of all total hip arthroplasties performed in the United States are done for osteonecrosis.
  • Male > females.
  • Osteonecrosis generally affects patients in the age of 30-50 years.
  • Bilateral osteonecrosis occurs in 80 % of cases.

Risk factors for osteonecrosis:

  1. Trauma
  2. Corticosteroid use
  3. Alcohol abuse
  4. Smoking
  5. Hemoglobinopathies (e.g., sickle cell anemia)
  6. Coagulation disorders
  7. Myeloproliferative disorders (Gaucher disease, leukemia)
  8. Caisson disease
  9. Human immunodeficiency virus infection
  10. Pregnancy
  11. Systemic lupus erythematosus (SLE)
  • Trauma results in damage to the medial femoral circumflex artery which is the main blood supply to the femoral head. This leads to the death of cells within the bony matrix.
  • Other risk factors may cause intravascular coagulation:
    • Coagulation of the intraosseous microcirculation results in venous thrombosis.
    • This leads to arterial occlusion due to the lack of venous outflow.
    • The arterial occlusion causes an increase in pressure within the bone which ultimately leads to decreased blood flow to the femoral head and eventual death of the cells.
  • Once the cells die, the reparative process begins and results in bony collapse and arthritic changes and collapse.

Classification

Modified Ficat classification for Osteonecrosis of the Hip (Steinberg Classification)

StageMRIBone ScanRadiographsPatient Status
0PositivePositiveNegativeAsymptomatic
1PositivePositiveNegativeSymptomatic
2PositivePositivePositive – No crescent signSymptomatic
3PositivePositivePositive – Crescent sign without flatteningSymptomatic
4PositivePositivePositive – Femoral head flatteningSymptomatic
5PositivePositiveJoint narrowing and/or acetabular changesSymptomatic
6PositivePositiveAdvanced degenerative changesSymptomatic
Modified Ficat classification (Steinberg Classification)

Clinical Evaluation

Symptoms & signs:

  • Patients are typically asymptomatic in early stage.
  • Insidious onset of pain in the anterior region of the hip.
  • Pain is increased with stairs, inclines, and impact.

Physical Examination:

  • Normal in early stages.
  • In late stages, hip movement restriction (especially internal rotation)
  • Special hip tests include:
    1. Log Roll test.
    2. The Stinchfield test.
  • It is essential to obtain a full, detailed history pertaining to the symptomatology including onset, location of the pain, duration of symptoms, the characteristics of the pain, alleviating and aggravating symptoms, radiation of symptoms, and timing of symptoms.

Imaging Evaluation:

Radiography Imaging:

  • Recommended views:
    • Pelvis antero-posterior (AP)
    • Lateral radiographs view (Frog-Leg).
  • Radiographic changes seen in osteonecrosis depend on the stage of the disease.
  • Plain films may appear normal in the early stages, but changes are noted as the disease progresses, such as increased density or lucency in the femoral head.
  • Crescent sign is visible on plain films (best seen on frog-leg lateral views)
  • In the end stages of the disease, femoral head collapse occurs, and severe arthritic changes may be seen on both sides of the joint.

MRI:

  • MRI is the standard imaging modality when radiographs are negative and osteonecrosis is suspected.
  • High sensitivity (99%) and specificity (99%).
  • When plain radiographs show changes in only one joint, MRI of the pelvis is indicated, not only to define clearly the extent of the disease in the symptomatic hip but also to evaluate the asymptomatic hip.
  • Findings include:
    • “Double density” appearance which appears dark on the T1 sequence and bright on the T2 sequence. 
    • The presence of a bright signal on the T2 sequence indicates bone marrow edema and is predictive of worsening pain and progression of the disease. 

Bone scanning:

  • Bone scanning can be useful, especially in assessing the status of multiple joints.
  • The uptake of technetium-99m usually is decreased in the very early stage of disease and is variable or increased at a stage when symptoms occur.

Treatment

Non-Operative:

  • Indications:
    • Pre-collapse of osteonecrosis of the hip (before crescent sign appearing) which is Ficat stages 0-II.
  • Methods:
    • Bisphosphonate treatment will decrease risk for head collapse.

Operative:

  • Surgical treatment depends on these major variables:
    1. Head collapse (crescent sign).
    2. Age (40 or younger).
    3. Etiology (reversible or not):
      • Irreversible etiology may include:
        1. Continued steroid use
        2. Idiopathic
        3. Hypercoagulable state
    4. Extent of head involvement (by osteonecrosis)
      • Percent of head involved on AP image multiplied by percent head involved on lateral image (e.g., 50% × 50% = 25% volume head involvement).
        1. A—small lesion: less than 15% head involvement.
        2. B—medium lesion: 15% to 30% head involvement.
        3. C—large lesion: greater than 30% head involvement.

Different conditions of surgical treatment

  1. Younger age patient (< 40 years) and crescent sign:
    • Total Hip Arthroplasty is the recommended treatment.
  2. Younger age patient (< 40 years) and NO crescent sign:
    • Core decompression: Stimulates a healing response.
    • Vascularized fibular strut.
    • Curettage of necrotic bone and bone grafting through femoral neck trap door.
    • Rotational proximal femoral osteotomy.
  3. Age 40 years or older and medium (B) or large (C) lesion:
    • Total Hip Arthroplasty is the recommended treatment.
  4. Older than 40 years and small (A) lesion:
    • Best option is core decompression.
  • Core decompression indications includes:
    1. No crescent sign.
    2. Reversible etiology:
      • Patients on chronic steroids have poor results with core decompression.
    3. Small head lesion (A lesion):
      • Patients with medium and large head lesions frequently collapse.
  • Vascularized fibular strut indications includes:
    1. Medium (B) and large (C) lesions
    2. No crescent sign (preferred)
    3. Reversible etiology.
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