A 68-year-old woman is brought to the emergency department with severe right hip pain after a fall. She tripped on a rug and fell against a wall and then to the floor, landing on her right hip. The patient has a history of depression and polymyalgia rheumatica. Medications include sertraline and low-dose prednisone. She also has a 40-pack-year smoking history. Blood pressure is 145/85 mm Hg and pulse is 96/min. The patient appears to be in significant pain. She is unable to move the right hip, and the right leg appears shorter than the left. A pelvic x-ray is shown in the image below:
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Injury involving which of the following arteries is most likely to lead to osteonecrosis in this patient?
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This patient's x-ray shows a right femoral neck fracture, which is common in elderly patients with osteoporosis who have fallen. Femoral neck fractures, especially when displaced, put the femoral head at risk for osteonecrosis if its blood supply is disrupted. The blood supply to the femoral head derives mainly from the ascending cervical and retinacular branches of the medial circumflex femoral artery. These vessels are especially vulnerable to damage from fractures of the femoral neck due to their close association with it.
(Choice A) The deep femoral artery gives rise to the medial and lateral circumflex femoral arteries. However, injury to the deep femoral artery is less likely because it is remote from the femoral neck.
(Choices B and C) Branches of the lateral circumflex femoral and superior and inferior gluteal arteries join with the medial circumflex femoral artery to form the trochanteric anastomosis. However, these arteries provide only minor contributions to the blood supply of the femoral head and neck.
(Choice E) The obturator artery gives rise to the artery of the ligamentum teres, which supplies a minor portion of the femoral head. This vessel is important in children because it supplies the region of the femoral head proximal to the epiphyseal growth plate, but it is of minimal clinical significance in adults.
Educational objective:
The medial circumflex femoral artery and its branches provide the majority of the blood supply to the femoral head and neck. Injury to these vessels due to a displaced femoral neck fracture can cause osteonecrosis of the femoral head.