- Discussion: (See: Blood Supply to Femoral Head)
- there are certain areas of bone in which vascular supply is precarious;
- these areas are subject to infarction and avascular necrosis;
- three such regions are head of femur, body of talus, & scaphoid;
- they have the common feature that a very large portion of their total surface is covered with articular cartilage through which vessels do not penetrate;
- blood supply for these bones enters through very restricted spaces, & there is limited collateral circulation;
- when principal route of the circulation to these bones is interrupted by trauma or disease, the collateral circulation is inadequate and necrosis ensues;
- avascular necrosis occurs in other bones, particularly body of talus, scaphoid, the lunate, and the head of the second metatarsal;
- occasionally, it develops in multiple areas in the same patient;
- this condition has been found to be frequent complication of prolonged steroid therapy used in patients with kidney transplants;
- interference w/ blood supply to femoral head results in infarction that may involve the entire head; more frequently, it is limited to a segment of the head;
- in infarcted area, there is death of marrow elements & of osteocytes;
- bone death is recognized histologically by disappearance of osteocytes from their lacunae;
- following infarction, there is an attempt at revascularization that extends inward from the adjacent viable bone;
- this revascularization process is very slow in the femoral head;
- hyperemia of surrounding bones causes osteoporosis of living bone, while infarcted bone retains its density and thus appears whiter or denser on roentgenogram;
- as vessels approach necrotic area, osteoclastic resorption of dead bone may so weaken the femoral head that a portion of it will collapse, resulting in
an irregular articular surface that sets the stage for painful degenerative arthritis
- references:
- Role of impairment of blood supply of the femoral head in the pathogenesis of idiopathic osteonecrosis.
- A microangiographic study of idiopathic osteonecrosis of the femoral head.
- Intraosseous arterial architecture in nontraumatic avascular necrosis of the femoral head. Microangiographic and histologic study.
- Selective digital subtraction arteriography in necrosis of the femoral head.
- Intraosseous pressure, oxygenation, and histology in arthrosis and osteonecrosis of the hip.
- Intra-osseous pressure and oxygen tension in avascular necrosis and osteoarthritis of the hip.
Current concepts on the pathogenesis of osteonecrosis of the femoral head.