Avascular necrosis of the femoral head

■ Case study Mary, a 58-year-old obese, White female, presents to your offi ce with left knee and groin pain that has been ongoing for 4 months. The pain has become increasingly worse and has prompted today’s visit. She is an established patient in your offi ce and you are seeing her for the fi rst time today. Mary denies any trauma to the left leg or knee, tick or insect bites, fever, or chills. She is awakened at night due to pain of the left knee and thigh. She states that she ties a tourniquet type of bandage to the left thigh at night before bed, “I put the bandage on in hopes that it will help relieve the pain.” The patient was advised to discontinue the practice of using the tourniquet on her leg due to potential adverse outcomes. The patient verbalized understanding of this and stated that she would no longer use it. She rates her pain as a 10 on a scale of 0 to 10 (0 being no

Avascular necrosis (AVN) of the femoral head is an acute condition that commonly presents as unilateral hip pain. AVN (also known as osteonecrosis) may be misdiagnosed as degenerative joint disease, as patients may complain of hip, knee, lower back, or groin pain. 1 NPs in the primary care setting can make an accurate diagnosis of AVN of the femoral head by eliciting a comprehensive history, performing a thorough physical exam, and utilizing appropriate diagnostic testing. There are three main causes of AVN: traumatic, nontraumatic, and idiopathic. In this case study the cause of AVN is nontraumatic.
■ Case study Mary, a 58-year-old obese, White female, presents to your offi ce with left knee and groin pain that has been ongoing for 4 months. The pain has become increasingly worse and has prompted today's visit. She is an established patient in your offi ce and you are seeing her for the fi rst time today. Mary denies any trauma to the left leg or knee, tick or insect bites, fever, or chills. She is awakened at night due to pain of the left knee and thigh. She states that she ties a tourniquet type of bandage to the left thigh at night before bed, "I put the bandage on in hopes that it will help relieve the pain." The patient was advised to discontinue the practice of using the tourniquet on her leg due to potential adverse outcomes. The patient verbalized understanding of this and stated that she would no longer use it. She rates her pain as a 10 on a scale of 0 to 10 (0 being no pain and 10 being the worst pain imaginable). Mary cannot tolerate full-weight bearing and does not use any assistive devices to ambulate. "I just hold on to things to get around in my house." Alleviating pain factors include sitting or lying down. Factors that aggravate the pain include standing or walking. Mary has tried over-the-counter acetaminophen and ibuprofen with no relief.

■ Patient history
Mary has a 35-year history of asthma that was well controlled until 8 years ago. She has been admitted to the hospital for asthma exacerbations three times in the last 2 years. She has been treated for multiple asthma exacerbations in the past and was prescribed short courses of high-dose corticosteroids with long tapers as treatment. She was diagnosed with hypertension 10 years ago and denies other medical conditions. Mary had two vaginal births and denies history of any type of surgery.
Mary denies history of tobacco use and denies illicit drug use. She states she drinks one glass of wine on special occasions. Mary was a cashier and is currently unemployed because of her inability to stand for long periods of time.
Her current medications include hydrochlorothiazide 12.5 mg/ lisinopril 20 mg (Prinzide)one tablet orally every day, albuterol (Proventil HFA)inhaler two puffs every 4 to 6 hours as needed for wheezing or dyspnea, and mometasone furoate (Asmanex twisthaler) two puffs (440 mg total) daily in the evening.

■ Risk factors
There are many risk factors that may contribute to the development of nontraumatic AVN of the femoral head (see Risk factors of nontraumatic AVN). The number one cause of nontraumatic AVN of the femoral head is use of corticosteroids. 2 The diagnosis of AVN of the femoral head is bilateral in approximately 75% to 95% of patients in whom corticosteroids were identifi ed as the causative factor. 3 One retrospective study indicated that there is a 12-month risk period for femoral head AVN in patients receiving high-dose corticosteroid treatment of 1800 to 2000 mg of prednisone in 1 month as a minimum dose. 4 Another group of patients at higher risk of developing AVN are those with sickle cell disease (SCD). 5 In SCD, the femoral head is the most common site of AVN. 6 One study indicated that SCD patients with AVN had a history of more hospitalizations with painful crises than those without AVN. 6 The most signifi cant risk factor for idiopathic AVN is middle-aged male gender. 7 There is no defi nitive cause identifi ed for idiopathic AVN; it may be a result of multiple factors that cause decreased blood fl ow resulting in bone death. 8 ■ Pathophysiology AVN occurs when there is a compromise of the blood supply to the femoral head. Blood is vital to bone tissue like any other organ in the body. When the supply is decreased or disrupted, there is bone tissue death (see AVN of the femoral head). There is debate over the cause of the disruption of blood fl ow. One theory suggests that there is a connection between corticosteroid use and AVN. Corticosteroids cause the body to be unable to break down lipids, which leads to hyperlipidemia. The theory suggests that hyperlipidemia may cause a fat embolism that compromises the blood supply and results in AVN. 3,9 This theory suggests using a hydroxymethylglutaryl coenzyme A reductase inhibitor (statin) as preventive treatment with high-dose corticosteroid use. 3,10 Corticosteroids affect the stem cells in the marrow by differentiating them into lipogenic cells. Statins work at the cellular level in the marrow by reducing lipogenesis. 11 Another theory pertaining to corticosteroid use is that apoptosis of endothelial cells causes increased intraosseous pressure, decreasing blood fl ow to the femoral head. 10 Additional theories suggest that compromise to the blood vessels may be a result of arteritis and embolism. 7 In patients with SCD, one theory suggests that high hemoglobin and hematocrit levels were found in those who develop AVN. 5 There is also compelling evidence of problems in the clotting cascade with plasminogen activator inhibitor-1, tissue plasminogen activator, plasminogen, and factor VII, causing impaired coagulation that results in AVN. 5 There is more research needed on the many causes and prevention of AVN.

■ Signs and symptoms
The patient may present with an antalgic gait due to pain. The patient may complain of a gradual progressive onset or acute severe pain in groin, hip, thigh, or lower back. 1,7 Nocturnal pain is a classic symptom of femoral head AVN. 1,7,12 Some patients complain of increased pain with activity that may radiate to groin, back, or thigh (see Differential diagnoses for AVN).

■ Assessment
Observe the patient walking from waiting room to exam room for gait evaluation if possible. Another good evaluation of the hip in regards to fl exion, quadricep strength, and lumbosacral nerve root is to observe the patient getting up onto the exam table. 7 This is a quick observation and evaluation that can be done without the examiner causing any pain to the patient. A patient with femoral head AVN will not be able to get on the exam table with ease. There are no obvious visible deformities of the leg or hip on inspection. There may be a leg length discrep-ancy if there is a total collapse of the femoral head. It is good practice to evaluate the joint above and below the painful joint to rule out referred pain. Evaluate range of motion of the hip with fl exion, abduction, adduction, and internal and external rotation bilaterally; most patients with AVN will not be able to tolerate rotation to 30 degrees as it will elicit extreme pain. 7

(See Hip fl exion, abduction, and adduction, and Internal and external rotation.)
A Patrick or FABER test should be performed and will elicit a positive test in those with AVN (see Patrick

AVN of the femoral head
A coronal section shows a circumscribed area of subchondral infarction with partial detachment of the articular cartilage and subarticular bone. Mary's exam begins with observation of her gait on the way to the exam room. Mary has an antalgic gait and tries to steady herself by leaning on the wall in the hallway. In the exam room she has great diffi culty getting up onto the exam table. There are no visible deformities of the left lower extremity. There is point tenderness of the left knee medially. There is no obvious laxity, but the exam is diffi cult due to patient guarding. Abduction and adduction of the left hip elicit extreme pain. She has left hip fl exion to 70 degrees with increased pain. She has severe pain on internal and external hip rotation, unable to reach 30 degrees of rotation. A Patrick (FABER test) was positive on the left and negative on the right. She had a negative Ober test bilaterally. Her lower extremity muscle strength was 5/5 bilaterally, and she is neurovascularly intact.
It is important to document assessment fi ndings by specifi cally describing what was done and the patient response for each exam technique.

■ Diagnostics
The initial test should be plain fi lm X-rays of the pelvis, including while standing. This test may or may not reveal AVN. 13 If there are no radiologic indications of AVN then a magnetic resonance imaging (MRI) test should be ordered. 1,13 With MRI there is the ability of staging the degree of AVN, which helps to determine the course of treatment. 13 Mary had plain X-rays of her knees and pelvis with standing views. There was adequate joint spacing in her knees with no bony abnormalities noted. The pelvic films indicate a collapse of the femoral head on the left, which is diagnostic of AVN.

■ Treatment
If the radiology reports indicate AVN of the femoral head, it is appropriate to refer the patient to an orthopedic surgeon for evaluation. 1 Depending on the severity, a core decompression may be performed to provide symptom relief before a total joint replacement is needed. 1 If there is total collapse, a joint replacement is necessary. 1 The patient will require effective pain management until the time of surgery, and this plan should be individualized based on patient history. If the patient is not a good surgical candidate, the only other option is non-weight bearing status allowing for ambulation with no weight on the affected leg. Pain management will be necessary for non-weight-bearing patients. 1,7 Best practice includes recommendation for referral to a pain management

Internal and external rotation 7,14
The patient should lie supine with the knee fl exed to 90 degrees. The NP should place one hand on the ankle and the other hand just above the knee. For internal rotation, the lower leg should be rotated to the lateral side. To check external rotation, the leg should be rotated in toward the midline. Hip Adduction: The patient should lie supine, and the NP's hand should be placed on the ankle with the other hand on the opposite hip applying gentle pressure. The leg should be brought slowly across the body until resistance is felt.
Hip Abduction: The patient should lie supine, and the NP should place one hand on the ankle and the other hand on the opposite hip. The NP should slowly move the leg away from the patient's body. Repeat maneuver with the other leg.

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Clinical Case Report specialist who has experience with drug combinations for optimal pain control. As an adjunct to pharmacologic pain control, complementary and alternative medicine should be suggested if the patient is open to these therapies.
AVN of the femoral head is a condition that should not be missed, and prompt referral to an orthopedic surgeon is necessary to preserve function. NPs in primary care should be aware of this condition and be suspicious of AVN in patients with risk factors.
■ Case study outcome Mary had plain fi lm X-rays of the pelvis, including standing views that indicated she had a total collapse of the femoral head. There was no need for an MRI due to the X-ray fi ndings. She was immediately scheduled for a total hip replacement consultation with the joint replacement specialist in the clinic. Mary had intolerable pain, so she was given a prescription for acetaminophen with hydrocodone (Vicodin) until the consultation the following week. She was advised not to take the Vicodin with other products containing acetaminophen due to potential serious adverse effects on the liver. Mary was also given a cane for support while ambulatory.
■ Recommendations for NP practice Any acute, severe, nontraumatic hip pain with worsening nocturnal symptoms, an inability to bear weight, and pain that radiates to the groin or thigh is a red fl ag for AVN in patients with a history of highdose corticosteroid use, alcohol abuse, SCD, systemic lupus erythematosus (SLE), or middle-aged males with no risk factors other than age and gender. A plain fi lm X-ray of the pelvis with a standing view should be ordered as well as an MRI if plain fi lms are inconclusive. If radiologic fi ndings are indicative of AVN, then referral to an orthopedic surgeon is urgent for evaluation and determination of the treatment.

Ober test 7
The patient should lie on the side with knee fl exed on the side down. The NP should stand behind the patient and ask him or her to fl ex the other knee and hold it for support. With the other hand, the NP should put some pressure on the iliac crest. The hip should be slightly abducted and then extended. When letting go of the leg, the NP should provide support if the leg falls to avoid injury. If the leg does not fall down, then it is a positive test indicating that the iliotibial band is tight.

Patrick's or FABER test 7
The patient should lie supine with knees bent so that the ankle rests on the opposite knee. The NP should place one hand on the fl exed knee and the other hand on the opposite hip, applying gentle pressure. The action should be repeated on the other side. The test is positive if it elicits groin pain, which indicates a hip problem, or if there is pain in the spine, which indicates a problem with the sacroiliac joint.