A 37-year-old man comes to the office due to a 2-month history of left-sided groin pain. The patient has a progressive, achy pain that is present at rest and worse with ambulation and weight bearing. He was treated for poison ivy dermatitis with a 5-day course of oral prednisone a year ago but has had no other medical conditions and takes no medications. The patient drinks 5 or 6 alcoholic beverages a day. He works as a gardener for a landscaping service and plays soccer twice a week. Vital signs are normal. BMI is 24 kg/m². On examination, the patient appears mildly uncomfortable and anxious. Examination of the hip and groin shows no erythema, warmth, or swelling. Active and passive range of motion at the left hip is decreased in extension, abduction, and internal and external rotation. X-ray of the hip is shown in the exhibit. Which of the following is most likely contributing to this patient's condition?

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11ec25c8_d970_d54b_bc81_1bb2d7622846_MD0003_00 This patient has osteonecrosis (avascular necrosis) of the femoral head, presenting with chronic groin pain and decreased range of motion. The diagnosis is confirmed on x-ray showing flattening and patchy sclerosis of the femoral head; x-ray has low sensitivity, and MRI, which can visualize the boundary between normal and ischemic bone, may be performed if x-ray is nondiagnostic. flattening and patchy sclerosis MRI Osteonecrosis is caused by disruption of perfusion due to macro- or microvascular occlusion, endothelial dysfunction, or increased intraosseous pressure. Excessive alcohol intake is a major risk factor. The risk is proportionate to the amount and duration of use, with most cases occurring in individuals consuming ?24 drinks/week (?400 mL/week) for ?8 years. Alcohol-related osteonecrosis is likely due to fat embolism in the setting of hyperlipidemia, particularly hypertriglyceridemia; additional contributing factors include adipocyte hypertrophy in the marrow with resulting venous stasis. (Choice A) Autoimmune arthritis, primarily rheumatoid arthritis (RA), can affect the hip and cause chronic pain and loss of motion. However, monoarticular hip RA is rare, and most patients have polyarticular disease. In addition, the typical x-ray findings of RA (eg, periarticular bony erosions and osteopenia, concentric loss of joint space) are not present in this patient; he has no erythema, warmth, or swelling to suggest inflammatory synovitis. (Choice C) Excess loading of the hip due to obesity or mechanical deformity can lead to osteoarthritis (OA). Although OA can cause chronic hip pain, x-ray typically shows decreased joint space and periarticular osteophytes. This young man with a normal BMI is unlikely to have OA. decreased joint space (Choice D) Systemic corticosteroid use is a major risk factor for osteonecrosis. However, it is seen primarily in patients receiving chronic, supraphysiologic doses. The risk from a single short course of prednisone, like this patient had, is very low, as is the risk from nonsystemic (eg, inhaled, intraarticular) corticosteroids. (Choice E) Human leukocyte antigen-B27 serotype is a risk factor for ankylosing spondylitis and psoriatic arthritis. Ankylosing spondylitis can affect the hip, but most patients have chronic back and sacroiliac pain. Psoriatic arthritis can present as a distal, small-joint arthritis; mixed oligoarthritis; or spondyloarthropathy. Large-joint monarthritis is rare. Educational objective: Osteonecrosis of the femoral head presents with chronic groin pain and decreased hip range of motion. It is caused by disruption of perfusion due to vascular occlusion, endothelial dysfunction, or increased intraosseous pressure. Excessive alcohol use is a major risk factor, with the risk proportionate to the amount and duration of use.

A 37-Year-Old Man Comes to the Office Due to a 2-Month