Each week, Osmosis shares a USMLE® Step 1-style practice question to test your knowledge of medical topics. Today’s case involves a 62-year-old man who comes into the clinic to tell you about a pain in his right leg that comes and goes with activity. When you inspect his leg, you notice the leg isn’t swollen, but the skin has a dry, shiny texture. Can you figure out what’s going on and help him out?
A 62-year-old man comes to the clinic complaining of right leg pain for three months. The pain is characterized by a continuous cramping in the right thigh that starts after walking two blocks and goes away at rest. The patient has a history of hypertension, diabetes, and coronary artery disease. The patient smokes 1 pack of cigarettes per day. The patient’s temperature is 37.0 °C (98.6 °F), pulse is 80/min and regular, respirations are 20/min, and blood pressure is 155/95 mmHg. Physical exam shows decreased hair growth on the right thigh and calf compared to left. The skin on the right leg is dry and shiny. There is no swelling or tenderness. Pain does not occur with bending forwards or backwards at the waist. Which of the following muscles is directly supplied by the artery most likely involved in this patient’s disease?
A. Gluteus maximus
B. Rectus femoris
C. Quadratus femoris
D. Gastrocnemius
E. Abductor hallucis
Scroll down to find the answer!
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The correct answer to today’s USMLE® Step 1 Question is…
B. Rectus femoris
Before we get to the Main Explanation, let’s look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
A. Gluteus maximus
Incorrect: The gluteus maximus (main extensor of the hip) is supplied by the superior gluteal artery, a branch of the internal iliac artery. Occlusion of the internal iliac artery would cause pain in the buttocks and hips with exertion.
C. Quadratus femoris
Incorrect: The quadratus femoris (external rotator and adductor of the thigh) is supplied by the inferior gluteal artery, a branch of the internal iliac artery. Occlusion of the internal iliac artery would cause pain in the buttocks and hips with exertion.
D. Gastrocnemius
Incorrect: The gastrocnemius (flexor of the foot and leg) is supplied by the popliteal artery. Occlusion of the popliteal artery would cause pain below the knee but not in the thigh.
E. Abductor hallucis
Incorrect: The abductor hallucis (abductor and flexor of the great toe) is supplied by the tibial artery. Occlusion of the tibial artery would cause pain in the lower calf, ankle, and foot but not in the thigh.
Main Explanation:
This patient with athersclerotic risk factors is presenting with intermittent claudication in the right thigh, making peripheral artery disease (PAD) the most likely diagnosis. Claudication is characterized by cramping pain in the affected area that comes about during exercise and is relieved with rest. Peripheral artery disease, a type of peripheral vascular disease (PVD), is caused by insufficient tissue perfusion due to narrowing or occlusion of the aorta or one of the more distal branches supplying the limbs. Similar to coronary artery and cerebrovascular disease, the development of an atherosclerotic plaque that narrows or completely occludes an artery is the number one cause of peripheral artery disease, and therefore these diseases often exist together. Risk factors for atherosclerosis, such as hypertension, diabetes mellitus, smoking and hyperlipidemia, raise the suspicion for peripheral artery disease.
The location of a patient’s pain can indicate where the occlusion is:
This patient’s thigh pain, without pain in the hips or buttocks, suggests there is an occlusion in the femoral artery. The femoral artery gives rise to the deep femoral artery (profunda femoris) which branches to form the lateral femoral circumflex artery. The lateral femoral circumflex artery supplies blood to the rectus femoris muscle, which functions to flex the thigh at the hip joint and extend the leg at the knee joint. In addition to claudication, chronic limb ischemia may produce physical changes. These include decreased skin temperature (termed poikilothermia), decreased hair and nail growth, and loss of sensation. On physical exam, the pulses distal to the obstruction are weak, and there is diminished capillary refill in the affected area.
Major Takeaway:
Peripheral artery disease is caused by an occlusion in an artery supplying the extremities, usually the legs, characterized by claudication (pain with exertion) and diminished peripheral pulses. More proximal occlusions (closer to the aorta) will cause pain in the hips and thighs, while distal occlusions (in the leg) will cause calf and foot pain.
→ Peripheral artery disease: pathology review.
References:
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The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). Osmosis is not affiliated with NBME nor FSMB.
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