Hip Osteonecrosis

Question 1

What are causes of hip AVN?

Answer 1

Idiopathic (most common)
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
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

Question 2

What is the classification of hip osteonecrosis?

Answer 2

Steinberg (modified Ficat)
0- normal XR, normal MRI and bone scan	 
I- normal	XR, abnormal MRI 
II- cystic or sclerosis changes on XR
III- crescent sign (subchondral collapse) on XR 
IV- flattening of femoral head
V- narrowing of joint		 
VI- advanced degenerative changes

Question 3

What stage of hip AVN presents with subchondral collapse (“Crescent sign”)?

Answer 3

Steinberg stage III

Question 4

What treatment for early stage hip AVN in young patients can present with lower leg pain?

Answer 4

Vascularized free-fibula strut graft; leg pain is sign of tibia stress fracture

Question 5

Which stage is THA indicated for hip AVN?

Answer 5

Steingberg stage III; once head collapse occurs THA has most predictable outcome

Question 6

What is the most common intraoperative complication in a patient with sickle cell disease undergoing a total hip arthroplasty?

Answer 6

Femoral canal perforation; due to metaphyseal widening with scattered areas of sclerosis; some surgeons will ream over a guide wire to prevent

Question 7

A patient with osteonecrosis of his hip returns to your office to discuss findings of a recent MRI. Bone marrow edema seen on the MRI is most predictive of what?

Answer 7

Bone marrow edema seen on an MRI of a hip with osteonecrosis is the best indicator of worsening pain and likely progression to collapse of the femoral head

Question 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?

Answer 8

> 75%; other causes of AVN lead to collapse ~33% of the time