A 52-year-old Caucasian woman presents to the office for the evaluation of a constant left groin pain. The pain started spontaneously about a week ago and is gradually progressive. It is worse with walking and weight bearing. She has a past medical history of systemic lupus erythematosus, chronic renal insufficiency, and hypertension. She has been maintained on 20 mg/day of prednisone for eight months. Attempts to decrease the dose of prednisone in the past have caused a flare of lupus activity. She does not smoke or drink alcohol. On physical examination, she walks with a limp. There is marked discomfort and limitation of the range of motion on the left side.
Which of the following is the most sensitive imaging modality to diagnose the patient's condition?

Question

A 52-year-old Caucasian woman presents to the office for the evaluation of a constant left groin pain.  The pain started spontaneously about a week ago and is gradually progressive.  It is worse with walking and weight bearing.  She has a past medical history of systemic lupus erythematosus, chronic renal insufficiency, and hypertension.  She has been maintained on 20 mg/day of prednisone for eight months.  Attempts to decrease the dose of prednisone in the past have caused a flare of lupus activity.  She does not smoke or drink alcohol.  On physical examination, she walks with a limp.  There is marked discomfort and limitation of the range of motion on the left side.
Which of the following is the most sensitive imaging modality to diagnose the patient's condition?

Quizplus · Accepted Answer

Explanation: The patient's clinical presentation is consistent with osteonecrosis of the femoral head, also known as avascular necrosis or osteochondritis dissecans. Osteonecrosis usually occurs in the anterolateral femoral head, although it can also affect the humeral head, femoral condyles, vertebrae, proximal tibia, and small bones of the hand and foot. The disorders that are associated with the development of osteonecrosis include systemic lupus erythematosus (SLE), sickle cell disease, antiphospholipid antibody syndrome, chronic renal insufficiency and hemodialysis, trauma, Gaucher's disease, HIV infection, following renal transplantation, and Caisson's disease. Although a variety of disorders and disease processes can cause osteonecrosis, corticosteroid use and excessive alcohol intake are responsible for approximately 90% of the cases. Those who are at greatest risk are the SLE patients on chronic high-dose corticosteroid therapy (more than 15 to 20 mg/day). An early diagnosis of osteonecrosis is important to prevent bone collapse and the need for joint replacement. Physical findings are usually nonspecific, making it necessary to obtain sensitive imaging. MRI scanning is far more sensitive than plain films or bone scanning. Focal lesions are well demarcated, and changes can be seen early in the course of the disease when other studies are negative. (Choices A and B) Plain films have a poor sensitivity for detecting early disease. These can remain normal even months after the onset of symptoms of osteonecrosis, thereby causing a delay in the diagnosis and treatment. (Choice C) Technetium 99-m scanning is useful in patients with suspected disease with unilateral symptoms or no risk factors. MRI is still far more sensitive in diagnosing early disease. (Choice D) Pelvic ultrasound has no role in the diagnosis of osteonecrosis of the femoral head. Educational objective: MRI scanning is the most sensitive imaging modality for diagnosing osteonecrosis of the femoral head. Early diagnosis and treatment is important to prevent joint destruction.

A 52-Year-Old Caucasian Woman Presents to the Office for the Evaluation