**Question:** A 75-year-old man is transported to the emergency department with severe pain in his right hip and thigh. A radiographic examination reveals avascular necrosis of the femoral head. Which of the following conditions most likely occurred to produce avascular necrosis in this patient?

A. Alcohol abuse
B. Trauma
C. Glucocorticoid therapy
D. Inherited coagulopathy

**Answer Explanation:**

**Core Concept:** Avascular necrosis (AVN), also known as osteonecrosis or necrosis of bone, is a condition characterized by a disruption of blood supply to a bone, leading to reduced oxygen and nutrient supply and eventual bone death.

**Why the Correct Answer is Right:**

The correct answer, C. Glucocorticoid therapy, is the most likely cause of avascular necrosis in this patient. Glucocorticoids, such as prednisolone, are a class of corticosteroids used for their anti-inflammatory and immunosuppressive properties. However, prolonged or high-dose usage can lead to bone marrow suppression, which impairs the production of red and white blood cells, platelets, and cortisol. This results in an imbalance in bone remodeling, causing a decrease in bone mineral density and predisposing the individual to avascular necrosis.

**Why Each Wrong Option is Incorrect:**

A. Alcohol abuse (option A) is a relatively uncommon cause of avascular necrosis. While excessive alcohol consumption can lead to osteonecrosis of the femoral head, it is less likely in a 75-year-old patient and does not explain the bilateral involvement in this case (right and left hip).

B. Trauma (option B) is a risk factor for avascular necrosis but does not explain the bilateral involvement in this case. Additionally, trauma is less likely to cause avascular necrosis in an elderly patient without pre-existing osteoporosis or other risk factors.

D. Inherited coagulopathy (option D) is a rare cause of avascular necrosis and does not explain the bilateral involvement in this case. Inherited coagulopathies typically present with unexplained bleeding or thrombosis and not bilateral osteonecrosis.

**Core Concept:** Avascular necrosis can be caused by various factors leading to impaired blood flow to the bone, causing ischemia and subsequent necrosis. The correct answer, glucocorticoid therapy, is a common cause of avascular necrosis due to its immunosuppressive and anti-inflammatory properties.

**Clinical Pearls:**

1. Glucocorticoid-induced osteonecrosis is a well-known complication of prolonged or high-dose glucocorticoid use, particularly in elderly patients.
2. Bilateral involvement (right and left hip) suggests a systemic cause, such as glucocorticoid therapy, rather than local factors like trauma.
3. The patient's age also makes trauma less likely as a cause of osteonecrosis.
4. Inherited coagulopathies typically present with bleeding or thrombotic episodes, not bilateral osteonecrosis.