A 50 year old woman presents with constant left hip pain with associated dull ache and throbbing groin pain. She has a past medical history of systemic lupus erythematosus (SLE), hypertension, and chronic kidney disease. Her SLE is difficult to control and she has been of prednisone 20 mg daily for more than a year and hydroxychloroquine. She claims the pain started spontaneously about a week ago and has gradually worsened. The pain is worse with walking and weight bearing. She walks with a limp and has marked discomfort and limitation of the range of motion on the left side.
Which of the following imaging modalities is diagnostic of the patient’s condition?
The correct answer is:
C) Magnetic Resonance Imaging (MRI) of the left hip
This patient has osteonecrosis of the left hip; therefore, MRI is the diagnostic imaging modality most appropriate in this case. The patient is being treated with prednisone for her systemic lupus erythematosus (SLE). SLE is one of the diseases associated with osteonecrosis; others include: sickly cell disease, antiphospholipid antibody syndrome, hemodialysis, trauma, Gaucher’s disease, HIV infection, following renal transplantation, Caisson’s disease.
Answer A: is incorrect. Pelvic ultrasound has no role in the diagnosis of osteonecrosis and is mostly used to diagnose hip dysplasia in infants.
Answer B: is incorrect. Technetium 99m scanning is useful in patients with suspected disease with unilateral symptoms with no risk factors, however MRI is still far more sensitive in diagnosis of early osteonecrosis.
Answers D and E: are incorrect. Plain films have poor sensitivity for detecting early disease and are not diagnostic of osteonecrosis.
Key Learning Point
MRI is the preferred diagnostic test for avascular osteonecrosis.
