Hip Osteonecrosis

Topic updated on 03/24/16 5:43pm
  • Also known as avascular necrosis
  • Epidemiology
    • incidence
      • 20,000 new cases per year in the United States
      • accounts for 10% of total hip arthroplasties performed
    • demographics
      • male > females
      • average age at presentation is 35 to 50
    • location
      • bilateral hips involved 80% of the time
      • multifocal osteonecrosis
        • disease in three or more different joints
        • 3% of patients with osteonecrosis have multifocal involvement
    • risk factors
      • direct causes
        • irradiation
        • trauma
        • hematologic diseases (leukemia, lymphoma)
        • dysbaric disorders (decompression sickness, "the bends") - Caisson disease
        • marrow-replacing diseases (e.g. Gaucher's disease)
        • sickle cell disease 
      • indirect causes
        • alcoholism
        • hypercoagulable states
        • steroids (either endogenous or exogenous)
        • systemic lupus erythematosus (SLE)
        • transplant patient
        • virus (CMV, hepatitis, HIV, rubella, rubeola, varicella)
        • protease inhibitors (type of HIV medication)
        • idiopathic
  • Pathophysiology
    • idiopathic AVN
      • intravascular coagulation is the final common idiopathic pathway
      • pathoanatomic cascade
        • coagulation of the intraosseous microcirculation
        • venous thrombosis
        • retrograde arterial occlusion 
        • intraosseous hypertension 
        • decreased blood flow to femoral head
        • AVN of femoral head 
        • chondral fracture and collapse 
    • AVN associated with trauma
      • due to injury of femoral head blood supply (medial femoral circumflex)
  • Associated conditions
    • AVN rates of specific traumatic injuries
      • femoral head fracture: 75-100%
      • basicervical fracture: 50%
      • cervicotrochanteric fracture: 25%
      • hip dislocation: 2-40% (2-10% if reduced within 6 hours of injury)
      • intertrochanteric fracture: rare
    • higher risk of AVN with greater initial displacement and poor reduction
    • decompression of intracapsular hematoma may reduce risk
    • quicker time to reduction may reduce risk
  • Prognosis
    • risk of femoral head collapse with osteonecrosis is based on the modified Kerboul combined necrotic angle  
      • calculated by adding the arc of the femoral head necrosis on a mid-sagittal and mid-coronal MR image
        • Low-risk group = combined necrotic angle less than 190° 
        • Moderate-risk group = combined necrotic angle between 190° and 240° 
        • High-risk group = combined necrotic angle of more than 240° 

Steinberg Classification (modification of Ficat classification)
0 normal normal MRI and bone scan  
I normal abnormal MRI and/or bone scan  
II cystic or sclerosis changes abnormal MRI and/or bone scan  
III crescent sign (subchondral collapse) abnormal MRI and/or bone scan  
IV flattening of femoral head abnormal MRI and/or bone scan  
V narrowing of joint abnormal MRI and/or bone scan  
VI advanced degenerative changes abnormal MRI and/or bone scan  

  • Symptoms
    • insidious onset of pain
    • pain with stairs, inclines, and impact
    • pain common in anterior hip
  • Physical exam
    • mostly normal initially
    • advanced stages similar to hip OA (limited motion, particularly internal rotation)
  • Radiographs
    • recommended views
      • AP hip
      • frog-lateral of hip
      • AP and lateral of contralateral hip 
    • classification systems based largely on radiographic findings (see below)
  • MRI
    • highest sensitivity (99%) and specificity (99%)
    • double density appearance
      • T1: dark (low intensity band)
      • T2: focal brightness (marrow edema)
    • order when radiographs negative and osteonecrosis still suspected
    • presence of bone marrow edema on MRI is predicitve of worsening pain and future progression of disease 
  • Bone scan
  • Nonoperative
    • bisphosphonates
      • indicated for precollapse AVN (Ficat stages 0-II)
      • trials have shown that alendronate prevents femoral head collapse in osteonecrosis with subchondral lucency 
        • However, other studies have also shown no benefit of preventing collapse with bisphosphonates
  • Operative
    • core decompression with or without bone grafting
      • indications
        •  for early AVN, before subchondral collapse occurs
        • reversible etiology
      • technique
        • traditional method
          • drill an 8-10  mm hole through the subchdonral necrosis
        • alternative method
          • pass a 3.2 mm pin into the lesion two to three times for decompression
        • relieves intraosseous hypertension equals less pain
        • stimulates a healing response via angiogenesis
    • rotational osteotomy
      • indications
        • only for small lesions (<15%) in which the lesion can be rotated away from a weight bearing surface 
      • technique
        • typically performed through intertrochanteric region
      • outcomes
        • reported success rate of 60% to 90%
        • distorts the femoral head making THA more difficult
    • curettage and bone grafting through trapdoor technique
      • indications
        • preferably pre-collapse
      • technique
        • open a trap door through the cortex of the femoral neck to access the necrotic area of the femoral head and place bone graft
    • vascularized free-fibula transfer
      • indications
        •  for both pre-collapse and collapsed AVN in young patient
        • reversible etiology preferred
      • technique
        • remove the necrotic area with large core hole
        • fibular strut is placed under subchondral bone to help prevent collapse or tamp up small areas of collapse
      • outcomes
        • some centers demonstrating 80% success at 5 to 10-year follow-up
        • less predictable in patients >40
      • complications
        •  related to donor site morbidity
          • sensory deficit
          • motor weakness
          • FHL contracture
          • tibial stress fracture from side graft is taken
    • total hip replacement  
      • indications
        • younger patient with crescent sign or more advanced femoral head collapse, +/- acetabular DJD
        • irreversible etiology (chronic steroid use)
        • patients >40 with large lesions
      • techniques
        • cementless cup and stem
        • care must be taken while preparing the femur as there are high rates of femoral canal perforation  
      • outcomes
        • in young patients with osteonecrosis, there is a higher rate of linear wear of the polyethylene liner and a higher rate of osteolysis than compared to older patients who have THA for osteoarthritis 
        • provides good pain relief and function
    • total hip resurfacing
      • indications
        • in advanced DJD with small, isolated focus of AVN
        • requires adequate bone to support resurfacing component
        • contraindicated in underlying disease process or chronic steroid use causing AVN (poor bone quality) and renal disease (metal ions from metal-on-metal implant)
      • outcomes
        • medium-term follow-up showing problems with acetabular erosion and pain
    • hip arthrodesis
      • indications
        • only consider in the very young patient in a labor intensive occupation


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Qbank (9 Questions)

(OBQ13.50) Which of the following is the most common intraoperative complication in a patient with sickle cell disease undergoing a total hip arthroplasty? Topic Review Topic

1. Periprosthetic fracture distal to the implant
2. Iatrogenic fracture causing pelvic discontinuity
3. Perforation of the femoral canal
4. Cardiac arrest from fat embolization to lungs
5. Injury to the sciatic nerve

(OBQ12.254) A 45-year-old with a history of sickle cell anemia reports hip pain for the past 6 months. A radiograph of the affected hip is shown in Figure A. Which of the following interventions has been shown to have the best outcomes in this patient population? Topic Review Topic
FIGURES: A          

1. Observation
2. Bisphosphonates
3. Hemi-arthroplasty
4. Uncemented metal on polyethylene total hip arthroplasty
5. Cemented metal on polyethylene total hip arthroplasty

(OBQ12.270) A 65-year-old patient was treated with an open reduction/internal fixation for a left femoral neck fracture sustained 25 years ago. Five years ago he developed hip pain and was converted to a left hip hemiarthroplasty. He presents with complaints of groin pain for the past 6 weeks. A recent radiograph is shown in Figure A. The patient’s physical exam is limited secondary to pain. Serum laboratory values are WBC-8.0, ESR-20, CRP-0.5. A synovial fluid aspirate of the hip demonstrates < 500 cells (60% PMN). What is the most likely cause of this patient's symptoms? Topic Review Topic
FIGURES: A          

1. Acetabular protrusio
2. Infected hip hemiarthroplasty
3. Lumbar radiculopathy
4. Impingement of the hip hemiarthroplasty
5. Iliopsoas tendinitis

(OBQ11.196) A 47-year-old man presents with 1 week of left leg pain. 6 months prior he underwent a vascularized free-fibula bone graft from his left leg to his right hip for avascular necrosis. The pain is located at the level of his donor site and is worse with weight-bearing and relieved by rest. Physical exam shows focal tenderness over his tibia. A lateral radiograph from the day of presentation is shown in Figure A. WBC, ESR, and CRP are all within normal limits. What is the next best step in management to confirm the diagnosis? Topic Review Topic
FIGURES: A          

1. Compartment pressure measurements
2. CT scan
3. MRI scan
4. Ultrasound to rule out deep abscess
5. Bone biopsy

(OBQ09.8) In patients with sickle cell disease and asymptomatic osteonecrosis of the femoral head identified with magnetic resonance imaging, what percentage will eventually go on to femoral head collapse? Topic Review Topic

1. < 10%
2. 11% to 25%
3. 26 to 50%
4. 51 to 75%
5. > 75%

(OBQ08.239) A 40-year-old man complains of increasing groin pain. Radiographs show femoral head avascular necrosis with subchondral lucency but without femoral head collapse. Which of the following medical treatments have been shown to decrease the risk of subsequent femoral head collapse? Topic Review Topic

1. Cyclic parathyroid hormone therapy
2. Bisphosphonate therapy
3. RANK ligand therapy
4. RANK therapy
5. Selective estrogen receptor modulator therapy

(OBQ04.220) A 41-year-old male has steroid-induced avascular necrosis of the hip and decides to undergo metal on polyethylene total hip arthroplasty. His 80-year-old, sedentary father had a total hip replacement 5 years ago. With comparison to his father, the patient should be informed of the following risk? Topic Review Topic

1. Increased risk of sciatic nerve palsy
2. Increased longevity of prothesis
3. Increased risk for polyethylene wear and osteolysis
4. Reduced range of motion
5. Lower likelihood of revision surgery

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