A 24-year-old man presents to his primary care physician with left groin pain. The pain started a year ago and has progressed. He now has 8/10 pain when climbing stairs or rising from a seated position. He localizes the pain to the front of his groin. He denies any erythema or swelling. He has a history of hypertension, sickle cell anemia, and a splenectomy. He drinks a glass of wine with dinner every night and took up scuba diving 2 months ago but otherwise does not exercise. His temperature is 97.5°F (36.4°C), blood pressure is 124/68 mmHg, pulse is 82/min, and respirations are 16/min. His body mass index (BMI) is 18.1 kg/m^2. Physical exam reveals left groin pain at the terminal ranges of hip abduction and internal rotation. There is no point tenderness. A radiograph is obtained as in Figure A. Which of the following components of this patient’s history most strongly predisposed him to this condition?
Low BMI
Scuba diving
Alcohol use
History of sickle cell disease
History of sickle cell disease
This patient with sickle cell disease (SCD) presents with anterior groin pain, especially with weight-bearing, and radiographic findings of amorphous lytic and sclerotic lesions of the femoral head, consistent with avascular necrosis. SCD is a predisposing factor for avascular necrosis.

Avascular necrosis has a multitude of direct causes, including irradiation, trauma (history of femoral neck fracture), hematologic diseases such as leukemia, SCD, and idiopathic etiology. In traumatic causes, injury to the medial femoral circumflex artery supplying the femoral head causes vascular disruption with resulting osteonecrosis. In SCD, the propensity for sickle-shaped erythrocytes to stick to one another and occlude blood vessels results in loss of circulation to the femoral head with consequent osteonecrosis. Avascular necrosis of the femoral head presents with insidious onset of anterior groin pain. The diagnosis can be secured with plain radiographs, although magnetic resonance imaging has the highest sensitivity and specificity for uncertain cases. Treatment consists of bisphosphonates with crutches (non-weight-bearing) and/or surgery depending on the degree of femoral head collapse and etiology.

Akinyoola et al. studied the risk factors associated with avascular necrosis of the femoral head in patients with sickle cell disease. The authors found that the rate of pain crises and annual hospitalizations are associated with avascular necrosis. The authors recommend further study to explain differences in the prevalence of osteonecrosis in different populations with sickle cell disease.

Figure/Illustration A shows a plain radiograph of the left hip in a skeletally mature individual, demonstrating amorphous cortical lesions (red arrows) in the femoral head and cortical irregularity (blue arrow) typical of avascular necrosis.

Incorrect Answers:
Answer A: Excess alcohol use has been associated with the risk of avascular necrosis. This patient uses alcohol in moderation (2 drinks or fewer per day for men) and has no history of alcohol use disorder.

Answer C: Lack of physical activity is a predisposing factor for osteoporosis but is not associated with avascular necrosis. Osteoporosis may increase the risk of a hip fracture, which would present with a painful, shortened, and externally rotated lower extremity.

Answer D: Low BMI is not a predisposing factor for avascular necrosis. In contrast, obesity has been associated with an increased risk of avascular necrosis.

Answer E: Scuba diving can indirectly predispose patients to avascular necrosis through decompression sickness (Caisson Disease). In decompression, dissolved gases in the arterial supply form gas emboli, leading to microvascular occlusion and dysbaric osteonecrosis. However, this patient’s symptoms have been present for 1 year whereas he only recently began scuba diving.

Bullet Summary:
Sickle cell disease is a predisposing factor for avascular necrosis of the femoral head, which presents as insidious anterior groin pain.