A Closer Look at Avascular Necrosis of the Hip

Avascular necrosis accounts for approximately 10% of all total hip arthroplasties performed in the United States. Avascular necrosis can be caused when decreased blood flow is caused at the femoral head, which then leads to cellular death, fracture, and eventual collapse of the articular surface. Ultimately, of individuals who are diagnosed with...
2017-12-06-17-john-Snyder-AVN-775x250

Avascular necrosis accounts for approximately 10% of all total hip arthroplasties performed in the United States. Avascular necrosis can be caused when decreased blood flow is caused at the femoral head, which then leads to cellular death, fracture, and eventual collapse of the articular surface. Ultimately, of individuals who are diagnosed with AVN, there is a collapse rate of 67% in asymptomatic and 85% in symptomatic patients.1,2

Who is at Risk?

Moyer-Angeler and colleagues performed a review of the indirect and direct risk factors for the eventual development of AVN and found the following results:1

Direct Risk Factors Indirect Risk Factors
Femoral Head/Neck Fracture Chronic Corticosteroid Use
Hip Dislocation Excessive Smoking and/or Alcohol Use
Slipped Capital Femoral Epiphysis Coagulation Disorders
Radiation Therapy Hemoglobinopathies
Sickle Cell Disease Dysbaric Phenomena
Caisson Disease Autoimmune Diseases
Myeloproliferative Disorders Hyperlipidemia

What is the Clinical Presentation?

Clinical presentation may include subjective complaints like asymptomatic pain in early stages, and groin pain radiating to the knee or ipsilateral buttock. X-ray imaging may be negative in early stages as well.1,3,4

The physical examination may reveal painful, global restrictions in active and/or passive range of motion (especially internal rotation). Bilateral symptoms are also common, and are reported in 70% of cases. The patient may also present with an antalgic gait pattern.

Symptoms may be distributed as follows:

  • Hip Region (97%)
    • Groin (93%)
    • Buttock (34%)
    • Greater Trochanter (9%)
  • Referred Pain (77%)
    • Knee (68%)
    • Anterior Thigh (36%)
    • Lower Leg (18%)
    • Low Back (8%)

Pain from AVN is significantly more frequent in the knee and lower leg, but significantly less frequent in the lower back than pain from osteoarthritis.1,3,4

What About Special Testing?

The tables below show the accuracy of various diagnostic tests:7

Hip Extension < 15 Degrees
Reliability Sensitivity Specificity +LR -LR
N/A 0.19 0.92 2.38 .88

 

Hip External Rotation < 60 Degrees
Reliability Sensitivity Specificity +LR -LR
N/A .38 .73 .48 .85

 

Pain with Internal Rotation
Reliability Sensitivity Specificity +LR -LR
N/A 0.13 0.86 0.93 1.01

Is Conservative Management Effective?

Unfortunately, based on the few studies available evaluating the effectiveness of conservative and physical therapy intervention, there is no evidence supporting the ability of these interventions to decrease symptoms or prevent disease progression.5,6 At present, the best options available for this patient population involves either total hip arthroplasty (see the video animation below) or core decompression. Having the ability to rule out/in this disorder is of utmost importance in order for the appropriate surgical intervention to be applied.

Source: www.medbridgeeducation.com