Avascular necrosis of hip

Case contribution: Dr Radhiana Hassan

Clinical: 

• A 43 years old lady
• With underlying connective tissue disease
• On prolong steroid treatment

Radiographic findings:

• There is flattening of left femoral head (white arrow)
• The flattening involving less than one third of the head region
• Associated with mixed lytic and sclerotic changes
• There is presence of crescent sign
• The joint space is not narrowed
• Medullary nephrocalcinosis also noted at both renal region (yellow arrows), more on the right side

MRI findings:

• There is abnormal flattening of left femoral head, about 2-3 mm depression
• Abnormal signal intensity which is hypointense on both T1 and T2-weighted images
• Area of abnormal signal involving less than 30% of femoral head region
• No joint effusion, no joint space narrowing
• No obvious acetabular involvement is seen.

Diagnosis: Avascular necrosis of left hip.

Discussion:

• Avascular necrosis also known as osteonecrosis
• It can be traumatic or non-traumatic, bilateral in 40-80% of non traumatic cases
• Risk factors: chronic corticosteroid therapy, alcoholism, smoking, SLE, hyperlipidaemias, HIV, hemoglobinopathies, chronic renal failure, DM and pregnancy-related.
• A few classification and staging based on clinical, x-rays, mri and bone scan
  

  Stage	Ficat and Arlet classification	Steinberg staging
  Stage 0	Plain radiograph normal, MRI normal, clinical symptoms nil	normal or non-diagnostic radiograph, MRI or bone scan
  Stage 1	Plain radiograph normal or minor osteopenia, MRI oedema, Bone scan increased uptake, clinical symptoms: pain at groin	Normal radiograph, abnormal bone scan and/or MRI; A-mild head involvement <15%, B-moderate: 15-30% and C severe >30%.
  Stage II	Plain radiograph mixed osteopenia and/or sclerosis and/or subchondral cyst without any subchondral lucency, MRI geographic defect, bone scan increased uptake, clinical symptoms pain and stiffness	Cystic and sclerotic radiographic change A-mild head involvement <15%, B-moderate: 15-30% and C severe >30%.
  Stage III	Plain radiograph crescent sign and eventual cortical collapsed, MRI same as plain radiograph, clinical symptoms pain and stiffness +/- radiation to knee and limp	Subchondral lucency or crescent sign;  A-mild <15% head involvement, B-moderate, 15-30% and C-severe >30%
  Stage IV	Plain radiograph end stage with evidence of secondary degenerative change, MRI same as plain radiograph, Clinical sypmtoms oain and limp	Flattening of femoral head, with depression graded into A mild (<2mm), B-moderate (2-4 mm) and C-severe (>4 mm)
  Stage V	–	Joint space narrowing with or without acetabular involvement (A, B, C-depends on femoral head involvement as in Stage IV)
  Stage VI	–	Advanced degenerative changes