Approach Considerations
In 2019, the Association Research Circulation Osseous (ARCO) published consensus-based diagnostic criteria for glucocorticoid- associated osteonecrosis of the femoral head (GA-ONFH)and alcohol-associated ONFA. The diagnosis is made by reference to symptoms, signs, imaging, and/or histological examination [9, 10]
Criteria for a diagnosis of GA-ONFH included the following [9] :
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The patient should have a history of glucocorticoid use > 2 g of prednisolone or its equivalent within a 3-month period
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Osteonecrosis should be diagnosed within 2 years after glucocorticoid usage
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The patient should not have other risk factor(s) besides glucocorticoids.
Criteria for a diagnosis of alcohol-associated ONFH included the following [10] :
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The patient should have a history of alcohol intake > 400 mL/wk (320 g/wk, any type of alcoholic beverage) of pure ethanol for more than 6 months
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ONFH should be diagnosed within 1 year after intake of this amount of alcohol
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The patient should not have other risk factor(s)
Laboratory Studies
Lab tests have limited utility in the diagnosis of osteonecrosis, with exceptions as follows:
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Sickle cell testing in African Americans
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Lipid profile
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Screening for hypercoagulability
Imaging Studies
Anteroposterior (AP) radiographs (see image below) and frog lateral radiographs of both hips are the primary diagnostic modalities.
AP and frog lateral tomograms are indicated if patients have evidence of disease on radiographs but have no collapse. These images are often helpful in staging.
Sensitivity and specificity of magnetic resonance imaging (MRI) 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.
Osteonecrosis is classically delineated on MRI by serpiginous hypointense signal with or without associated subchondral collapse or secondary osteoarthritis. [17] MRI is recommended to identify bilateral disease when 1 hip has radiographic signs of disease and the other is normal (see image below).
Bone scanning is a low-cost alternative when index of suspicion is low. They can be helpful when x-ray findings are normal if MRI cannot be obtained (see image below).
Diagnostic Procedures
Core biopsy and interosseous pressure measurement
An open biopsy of a 10-mm core of bone from the femoral head can be used for diagnosis (see image below). Measurement of interosseous pressure can be obtained before and after biopsy to confirm decompression of the 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.
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.
Staging
Nearly 20 classification systems have been developed to stage osteonecrosis and provide information on prognosis, guide treatment selection, and facilitate outcome comparison. The following are the three most widely used classification systems:
Ficat classification
The Ficat classification of osteonecrosis was developed before the MRI and is based on radiographic findings. [18] There is no assessment of the size or extent of the lesion. However, it still is widely utilized because it is simple and easy to use. The stages are as follows:
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Stage 0 - No pain, normal radiographic findings, abnormal bone scan or MRI findings
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Stage I - Pain, normal x-ray findings, abnormal bone scan or MRI findings
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Stage IIa - Pain, cysts and/or sclerosis visible on x-ray, abnormal bone scan or MRI findings, without subchondral fracture
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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
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Stage IV - Pain, acetabular disease with joint space narrowing and arthritis (osteoarthrosis) visible on x-ray, abnormal MRI or bone scan findings
The University of Pennsylvania classification of osteonecrosis (Steinberg system)
The University of Pennsylvania classification was developed by Steinberg and the important features of this system is that it includes measurement of lesion size and extent of joint involvement using MRI. [19, 20] The stages are defined in the table below.
Table 1. University of Pennsylvania classification of osteonecrosis (Open Table in a new window)
Stage |
Criteria |
0 |
Normal radiograph, bone scan, and magnetic resonance images |
I |
Normal radiograph. Abnormal bone scan and/or magnetic resonance images A: Mild (< 15 % of femoral head affected) B: Moderate (15–30 % of femoral head affected) C: Severe (>30 % of femoral head affected) |
II |
Cystic and sclerotic changes in femoral head A: Mild (< 15 % of femoral head affected) B: Moderate (15–30 % of femoral head affected) C: Severe (> 30 % of femoral head affected) |
III |
Subchondral collapse without flattening (crescent sign) A: Mild (< 15 % of femoral head affected) B: Moderate (15–30 % of femoral head affected) C: Severe (>30 % of femoral head affected) |
IV |
Flattening of femoral head A: Mild (< 15 % of surface and < 2 mm of depression) B: Moderate (15–30 % of surface and 2–4 mm of depression) C: Severe (>30 % of surface and > 4 mm of depression) |
V |
Joint narrowing or acetabular changes A: Mild B: Moderate C: Severe |
VI |
Advanced degenerative changes |
Association Research Circulation Osseous (ARCO) system
The Association Research Circulation Osseous (ARCO) system was an attempt to establish an internationally accepted classification with uniform definition and terminology. [21] The stages are defined in the table below.
Table 2. Association Research Circulation Osseous (ARCO) system (Open Table in a new window)
Stage |
Criteria |
0 |
Bone biopsy results consistent with osteonecrosis; other test results normal |
I |
Positive findings on bone scan, MRI, or both A: < 15% involvement of the femoral head (MRI) B: 15-30% involvement C: > 30% involvement |
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 |
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 |
IV |
Articular surface flattened; joint space shows narrowing; changes in acetabulum with evidence of osteosclerosis, cyst formation, and marginal osteophytes |
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Osteonecrosis, hip. Anteroposterior radiograph showing Ficat stage III disease.
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MRI showing osteonecrosis of right hip, normal left hip.
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Bone scan showing osteonecrosis of right hip.
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Osteonecrosis, hip. Anteroposterior radiograph core biopsy.
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Osteonecrosis, hip. A radiograph of a limited femoral resurfacing performed for a collapsed femoral head with damaged femoral head cartilage and intact acetabular cartilage.
Tables
Stage |
Criteria |
0 |
Normal radiograph, bone scan, and magnetic resonance images |
I |
Normal radiograph. Abnormal bone scan and/or magnetic resonance images A: Mild (< 15 % of femoral head affected) B: Moderate (15–30 % of femoral head affected) C: Severe (>30 % of femoral head affected) |
II |
Cystic and sclerotic changes in femoral head A: Mild (< 15 % of femoral head affected) B: Moderate (15–30 % of femoral head affected) C: Severe (> 30 % of femoral head affected) |
III |
Subchondral collapse without flattening (crescent sign) A: Mild (< 15 % of femoral head affected) B: Moderate (15–30 % of femoral head affected) C: Severe (>30 % of femoral head affected) |
IV |
Flattening of femoral head A: Mild (< 15 % of surface and < 2 mm of depression) B: Moderate (15–30 % of surface and 2–4 mm of depression) C: Severe (>30 % of surface and > 4 mm of depression) |
V |
Joint narrowing or acetabular changes A: Mild B: Moderate C: Severe |
VI |
Advanced degenerative changes |
Stage |
Criteria |
0 |
Bone biopsy results consistent with osteonecrosis; other test results normal |
I |
Positive findings on bone scan, MRI, or both A: < 15% involvement of the femoral head (MRI) B: 15-30% involvement C: > 30% involvement |
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 |
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 |
IV |
Articular surface flattened; joint space shows narrowing; changes in acetabulum with evidence of osteosclerosis, cyst formation, and marginal osteophytes |
