Infarcts of The Bone

• also termed…

• aseptic necrosis

• avascular necrosis

• osteonecrosis

Clinically-important etiologies

• prolonged steroid therapy

• alcoholism

• trauma with dislocation or fracture

Ossification centers

• in one condition you can, for reasons unknown, get necrosis of ossification centers of various bones, and these are now referred to eponymously

• Legg-Perthes-Calvé disease involves infarction of the ossification center in the upper femur

• photograph of an infarcted femoral head

• when bone is deprived of normal vascular supply, the area becomes pale and very well-circumscribed. this is dead bone

Bone necrosis: stages

• stage I: yellow area is dead tissue. normally, what is covering the head of the femur? cartilage. just like in a myocardial infarct, there is a relatively ischemic area next to dead tissue, and reactive hyperemia of the immediately-adjacent, normal tissue is
  

  
  

• stage II: you have to heal this infarct. vessels come in with fibroblasts and try to heal the area. this is new bone formation taking place. you also see a small crack

• stage III: the crack we saw in stage II separates some of the cartilage with subjacent bone apart from the rest of the dead tissue. this crack is called a crescent sign

• stage IV: there will be problems secondary to the infarct of the bone. because of weight-bearing, the bone has lost its cartilage, and arthritis results. this is termed secondary degenerative osteoarthritis

• infarcted bone often concentrates radiopharmaceuticals, and this can be seen upon imaging

• sometimes, the infarct may not be apparent on X-ray or even radiopharmaceutical imaging. so, use MRI

• MRI of an infarct secondary to prolonged steroid therapy

Category: Pathology Notes