Certain particular bony areas are prone to development of osteonecrosis because of their relatively precarious blood suply
Avascular necrosis occurs in other bones, particulary:
-Humeral head
-Femoral condiles
-Tibial plateau
-Talus
-Lunate
-Scafoid
Causes:
-Trauma (femoral neck fractures, or posterior hip dislocations)
-sickle cell anemia
-corticosteroids
-deconpression sickness (embolization with nitrogen bubbles)
-Gaucher`s disease
-Legg-calvé-perthes`s disease
-Diabetes
-Infarction causes marrow edema and venous outflow obstruction, increasing pressure and widening the area of infarction.
-Hiperemia of the sorrounding bones causes osteoporosis of living bone,while infarcted bone retains its density and thus appears whiter or denser on roentgenogram.
-The bone is gradually revascularized. But bone reabsortion can lead to mecanical failure, with subcondral fractures (crescent sign).
-the result is flattening of femoral head, whith incongruity of joint and rapidy progression of secondary osteoarthritis.
-Hip pain, particulary with weigth bearing and rotation.
-limitation of wiegth bearing and motion.
-Can be normal initially,but frequently shows increased density of necrotic bone.
-Conbination of osteoclastic and new bone formation in revascularized areas creates x-ray appearance of mottled density.
-When collapse of segment of necrotic bone occurs, the compression more bone into smaller area also produces increased x-ray density.
-Evaluation includes and AP view and frog-leg lateral x-rays of hip.
-Often shows increased uptake around the necrotic bone.This represents acumulation of radionuclide in the area of increased bone turnover, at the junction beetwen dead and reactive bone.
-Prefered method for differential diagnosis and for radiollogically occult necrosis, since its more sensitive than bone scans or plain films.
-also used to outline the area of involvement.
-Sinovitis
-Transient osteoporosis
-Femoral neck stress fractures
-Metastatic diseases
| Stage | Pain | Radiographs | Pathology |
| I | none | incresead density | creeping substitution |
| II | none | reactive rim | rim, reinfarction |
| III | occasionaly | crescent sign | fracture |
| IV | limp | step of flatening | loose fragments |
| V | continous | collapse | cartilage flaps |
| VI | severe | deformed | advance arthritis |
-Core decompression - Wherin a channel is drilled throught the femoral neck.This procedure does give good relief. But this procedure is very controversial, because subsequent series have had failed.
-Total hip arthroplasty - Ongoing concern over cement disease, particulate matter, and stress shield changes in the femur inthe cemented or non cemented protheses makes a total hip arthroplasty a less desirably option. Can, also be tried for stage VI.
-Bipolar arthroplasty - Worst results are found, probably because of use of thin polyethylene in young heathy patients.
-Arthrodesis - Poor choice for bilateral necrosis (50 - 80%)
Mankin HJ: Non traumatic necrosis of bone (osteonecrosis). N Engl J Med 1992;326:1473
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