Hip Osteonecrosis Workup

Updated: Dec 29, 2015
  • Author: Michael Levine, MD; Chief Editor: William L Jaffe, MD  more...
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Workup

Laboratory Studies

Lab tests have limited utility in the diagnosis of osteonecrosis, with exceptions as follows:

  • Sickle cell testing in African Americans

  • Lipid profile

  • Screening for coagulopathies -Protein S and protein C deficiencies, factor V Leiden disease

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Imaging Studies

Anteroposterior (AP) radiographs (see image below) and frog lateral radiographs of both hips are the primary diagnostic modalities.

Osteonecrosis, hip. Anteroposterior radiograph sho Osteonecrosis, hip. Anteroposterior radiograph showing Ficat stage III disease.

AP and frog lateral tomograms

  • Indicated if patients have evidence of disease on radiographs but have no collapse

  • Often helpful in staging

MRI

  • Sensitivity and specificity is greater than 98%, which is higher than all other modalities.

  • This study is ideal if x-ray findings are normal and clinical suspicion is high. MRI should be performed in all patients with osteonecrosis to assess the extent of the disease. Three-dimensional MRI scanning with image registration may be used to assess changes in lesion size.

  • MRI is recommended to identify bilateral disease when 1 hip has radiographic signs of disease and the other is normal (see image below).

    MRI showing osteonecrosis of right hip, normal lef MRI showing osteonecrosis of right hip, normal left hip.

Bone scanning (see image below)

Bone scan showing osteonecrosis of right hip. Bone scan showing osteonecrosis of right hip.

See the list below:

  • Helpful when x-ray findings are normal if MRI cannot be obtained

  • Low-cost alternative when index of suspicion is low

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Diagnostic Procedures

Core biopsy (see image below) and interosseous pressure measurement

Osteonecrosis, hip. Anteroposterior radiograph cor Osteonecrosis, hip. Anteroposterior radiograph core biopsy.

See the list below:

  • An open biopsy of 10-mm core of bone from the femoral head can be used for diagnosis.

  • Measurement of interosseous pressure can be obtained before and after biopsy to confirm decompression of intraosseous space.

Venography

  • Injection of contrast under image intensification has been used as part of the functional evaluation of bone when measuring intraosseous pressure.

  • This can be used to confirm presence of the needle within the head and venous congestion.

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Histologic Findings

The first histologic findings are marrow and adipocyte necrosis. Next, liquefaction necrosis and interstitial edema occur. Pyknotic nuclei with empty lacunae are identified as osteocyte necrosis occurs. Eventually, the zone of necrosis is surrounded by repair tissue as revascularization proceeds. During this phase, the subchondral plate is weakened as resorption occurs faster than reformation, leading to subchondral collapse and eventual cartilage damage.

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Staging

Several radiographic staging systems are currently used.

  • Ficat classification [7]

    • Stage 0 - No pain, normal radiographic findings, abnormal bone scan or MRI findings

    • Stage I - Pain, normal x-ray findings, abnormal bone scan or MRI findings

    • Stage IIa - Pain, cysts and/or sclerosis visible on x-ray, abnormal bone scan or MRI findings, without subchondral fracture

    • Stage III - Pain, femoral head collapse visible on x-ray, abnormal bone scan or MRI findings, crescent sign (subchondral collapse) and/or step-off in contour of subchondral bone

    • Stage IV - Pain, acetabular disease with joint space narrowing and arthritis (osteoarthrosis) visible on x-ray, abnormal MRI or bone scan findings

  • Steinberg staging system [8]

    • Stage 0 - Normal or nondiagnostic radiographic, bone scan, and MRI findings

    • Stage I - Normal radiographic findings, abnormal bone scan and/or MRI findings

      • A - Mild: < 15% of head affected

      • B - Moderate: 15-30%

      • C - Severe: >30%

    • Stage II - Lucent and sclerotic changes in femoral head

      • A - Mild: < 15%

      • B - Moderate: 15-30%

      • C - Severe: >30%

    • Stage III - Subchondral collapse (crescent sign) without flattening

      • A - Mild: < 15% of articular surface

      • B - Moderate: 15-30%

      • C - Severe: >30%

    • Stage IV - Flattening of femoral head

      • A - Mild: < 15% of surface or < 2-mm depression

      • B - Moderate: 15-30% of surface or 2- to 4-mm depression

      • C - Severe: >30% of surface or >4-mm depression

    • Stage V - Joint narrowing and/or acetabular changes

      • A - Mild: Average of femoral head involvement as in stage IV and estimated acetabular

      • B - Moderate involvement

      • C - Severe

    • Stage VI - Advanced degenerative changes

  • International classification of osteonecrosis of the femoral head (Association Research Circulation Osseus [ARCO]) [9]

    • Stage 0 - Bone biopsy results consistent with osteonecrosis; other test results normal

    • Stage I - Positive findings on bone scan, MRI, or both

      • A - < 15% involvement of the femoral head (MRI)

      • B - 15-30% involvement

      • C - >30% involvement

    • Stage II - Mottled appearance of femoral head, osteosclerosis, cyst formation, and osteopenia on radiographs; no signs of collapse of femoral head on radiographic or CT study; positive findings on bone scan and MRI; no changes in acetabulum

      • A - < 15% involvement of the femoral head (MRI)

      • B - 15-30% involvement

      • C - >30% involvement

    • Stage III - Presence of crescent sign lesions classified on basis of appearance on AP and lateral radiographs

      • A - < 15% crescent sign or < 2-mm depression of femoral head

      • B - 15-30% crescent sign or 2- to 4-mm depression

      • C - >30% crescent sign or >4-mm depression

    • Stage IV - Articular surface flattened; joint space shows narrowing; changes in acetabulum with evidence of osteosclerosis, cyst formation, and marginal osteophytes

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