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Zorluk: OrtaInterpreting Imaging Results

A 42-year-old woman with systemic lupus erythematosus on chronic glucocorticoid therapy presents with progressive right groin pain exacerbated by weight-bearing. She is diagnosed with osteonecrosis (avascular necrosis) of the femoral head. Staging and subsequent treatment (e.g., core decompression versus total hip arthroplasty) rely heavily on the interpretation of specific radiologic features over time. Arrange the following imaging findings in chronological order, representing the natural progression of untreated osteonecrosis from the earliest pathologic stage to the most advanced, terminal stage.

  1. 1Normal plain radiography of the hip with bone marrow edema and focal signal changes identified only on magnetic resonance imaging (MRI)
  2. 2Appearance of mixed osteosclerotic and radiolucent (cystic) changes within the femoral head on plain radiography, with a preserved articular contour
  3. 3Presence of a subchondral radiolucent line (the 'crescent sign') on plain radiography, indicating subchondral microfracture
  4. 4Flattening and macroscopic collapse of the femoral head articular surface with progressive joint space narrowing and secondary osteoarthritic changes

Cevap

The correct chronological sequence is: normal radiographs with MRI edema (Stage I), followed by radiographic sclerotic/cystic changes with preserved contour (Stage II), then the subchondral 'crescent sign' (Stage III), and finally femoral head flattening with joint space narrowing (Stage IV).
The natural history of osteonecrosis begins with ischemic cell death that is initially undetectable on plain X-rays but identifiable on MRI as marrow edema. As the surrounding living bone attempts to remodel the necrotic zone, mixed sclerosis and cysts appear on X-rays. With continued mechanical stress on weakened necrotic bone, a subchondral microfracture occurs (the crescent sign). Ultimately, the structural integrity of the femoral head fails, causing flattening, collapse, and secondary degenerative joint disease.

Adım Adım Çözüm

1
Identify the earliest pathologic changes of osteonecrosis on imaging.
Normal plain radiography with bone marrow edema visible only on MRI (Item 1).
Before structural bone remodeling occurs, ischemic death of bone cells causes edema that is uniquely detectable by MRI.
2
Determine the initial radiographic changes prior to structural failure.
Mixed osteosclerotic and radiolucent (cystic) changes on plain radiography (Item 2).
The body attempts to repair the necrotic area via creeping substitution, leading to areas of resorption (cysts) and new bone formation (sclerosis) without altering the femoral head contour.
3
Identify the imaging sign of initial mechanical failure.
Presence of a subchondral radiolucent line or 'crescent sign' (Item 3).
As the necrotic bone weakens, microfractures occur beneath the articular cartilage, visible on X-ray as the crescent sign, heralding impending collapse.
4
Recognize the terminal imaging findings of untreated disease.
Flattening and collapse of the femoral head with secondary osteoarthritic changes (Item 4).
Loss of structural integrity results in flattening of the femoral head, which subsequently damages the acetabulum and leads to joint space narrowing and advanced osteoarthritis.

Anahtar Kavram

The progression of imaging findings in avascular necrosis of the femoral head follows a predictable sequence: pre-radiographic MRI changes (Stage I), radiographic remodeling without collapse (Stage II), subchondral fracture indicated by the crescent sign (Stage III), and structural collapse with secondary osteoarthritis (Stage IV).
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Interpreting Imaging Results

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