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Physician Assistant Exam: Hip Conditions

Several hip-related conditions make regular appearances on the Physician Assistant Exam (PANCE). You should be able to answer questions and know the basics regarding avascular necrosis, hip fractures, hip dislocation, and the slipped capital epiphysis.

Avascular necrosis (AVN)

When a person has a lack of blood supply to the head of the femur over a period of time, avascular necrosis (AVN) can result. Basically, avascular means “no blood.” Something inhibits the blood supply to the head of the femur, which is bad because bones need blood. Ischemic changes lead to necrosis, and the necrosed head actually collapses.

The initial presentation of avascular necrosis is often groin pain, but you may also see pain in the knee, hip, or gluteal region. The pain is worse with walking or standing and is better with sitting. On exam, trying to elevate the leg while the affected person is lying down can cause a lot of pain.

One of the most recognized causes of avascular necrosis is long-term steroid use. Other medical conditions that have been linked to avascular necrosis include connective tissue disease, vasculitis, long-term ethanol use, and trauma.

Because avascular necrosis can affect both hips, both hips should be imaged, even if the pain affects only one side. Initial radiographs may be nondiagnostic, so the gold standard for diagnosing avascular necrosis is the MRI.

The treatment for avascular necrosis is comprehensive and usually involves the use of a cane or walker to reduce the degree of weight bearing. A range of surgical options is available, one being removal of the necrotic areas.

Which one of the following conditions is not associated with the development of avascular necrosis?

(A) Steroids
(B) Trauma
(C) Sickle-cell anemia
(D) Alcohol use
(E) Emphysema

The answer is Choice (E), emphysema. All the other choices — steroids, trauma, sickle-cell anemia, and alcohol use — are associated with the risk of avascular necrosis. You may be thinking to yourself, wouldn’t someone with emphysema be on steroids? Although he or she can be, emphysema in and of itself hasn’t been associated with the development of avascular necrosis. Don’t read too much into the question.

The slipped capital femoral epiphysis

In slipped capital femoral epiphysis (SCFE, or skiffy), the femoral head slips inferiorly through a weakened area in the physis, or growth plate. This condition primarily affects children and teenagers, more males than females. The clinical presentation can be similar to avascular necrosis: groin pain, knee pain, and/or hip pain. As with avascular necrosis, standing or walking can make the pain worse.

Determine the degree of slippage using radiography. You need radiographs of the pelvis and hips taken with an anterior-posterior view as well as a frog-lateral radiograph. Any displacement of 50 percent or greater is categorized as severe.

The treatment of SCFE is usually surgical, with physical therapy and not bearing weight on the affected leg and hip as long as necessary.

Determining the cause of the SCFE may require a medical workup. Consider an endocrine disorder, looking mainly at pituitary abnormalities and bone disorders such as osteomalacia. Bone disease secondary to kidney dysfunction is also in the differential diagnosis.

There’s a small risk of SCFE developing into avascular necrosis.

Hip fractures and dislocations

A hip fracture is something that healthcare professionals see in many elderly people admitted to the hospital after a fall. Elderly people may have bone-health problems such as osteoporosis, vitamin D deficiency, malignancy (usually metastatic to the bone), and/or renal osteodystrophy. Osteodystrophy increases the risk of a fracture.

If you examine someone who fell and fractured the neck of the femur, you see that the affected leg looks shorter than the opposite leg. The affected leg is also externally rotated. Order radiographs of the femur and pelvis to look for the severity and type of fracture.

Hip fracture is a generalized term, referring to fractures that can affect either the femur or trochanter. For test purposes, you need to know two types of hip fractures:

  • Femoral neck fractures: These fractures are usually treated surgically. Because a femoral neck fracture can affect the blood supply to the head of the femur, the person has a risk of developing avascular necrosis.

  • Intertrochanteric fractures: These fractures, which occur between the greater and lesser trochanters, usually occur below the femoral neck. The majority of the time, they’re treated surgically and have a good chance of healing well.

A hip fracture commonly involves the femoral neck, whereas a dislocation involves the head of the femur. With a dislocation, you see displacement of the femur’s head from the acetabulum. The dislocation may be posterior (the most common type) or anterior. The most common cause of a hip dislocation is high-impact trauma, such as in a motor vehicle accident.

The hip is shortened in both a hip fracture and a dislocation. But unlike the femur neck fracture, where the leg is externally rotated, a dislocated hip is internally rotated. Imaging for a hip fracture includes radiographs of the hips and pelvis.

If no fracture is present, then the hip simply needs to be reduced. This reduction often occurs in the emergency room, without surgery (a closed reduction). If the hip can’t be reduced in the ER, then the patient may need to be taken to the OR for an open reduction.

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