Monday, May 31, 2010

Avascular Necrosis of Femoral Head and costs of treatment

Avascular necrosis of the femoral head (AVN) is an increasingly common cause of musculoskeletal disability, and it poses a major diagnostic and therapeutic challenge. Although patients are initially asymptomatic, AVN usually progresses to joint destruction, requiring total hip replacement (THR), usually before the fifth decade. It is estimated that almost 10% of the nearly 500,000 THRs performed each year in the United States are intended to treat AVN; at a cost of more than 1 billion dollars, THRs performed to treat AVN constitute approximately 25% of the total national costs for THR.

Axial CT in a patient without avascular necrosis of the femoral head shows prominent and thickened but normal trabeculae (arrow) within the femoral head. Note the delicate, sclerotic, raylike branchings emanating in a radial fashion from the central dense band. This is the asterisk sign.

Avascular necrosis, femoral head. Anteroposterior view of the pelvis shows flattening of the outer portion of the right femoral head from avascular necrosis (arrow), with adjacent joint space narrowing, juxta-articular sclerosis, and osteophytes representing degenerative joint disease.

Avascular necrosis, femoral head. Coronal T1-weighted MRI in a patient showing hypointense signal within the proximal femoral neck and intertrochanteric regions (arrows) representing hematopoietic marrow. Increased signal is present within the greater trochanters and femoral capital epiphysis representing normal fatty marrow .


Radiation Exposure

Abdominal CT versus X-Ray
Organ doses of radiation from CT scanning are considerably larger than those from corresponding conventional radiography. A conventional anterior-posterior abdominal x-ray examination results in a dose to the stomach of approximately 0.25 mGy, which is at least 50 times smaller than the corresponding stomach dose from an abdominal CT scan. A posterior-anterior chest x-ray would result in a radiation dose to the lungs of 0.01 mGy and a lateral chest x-ray, of a radiation dose of 0.15 mGy to the lungs.
Morning Report Questions

Q: Why are more children undergoing diagnostic testing with CT scanning?
A: The major growth area in CT use for children has been for the presurgical diagnosis of appendicitis, for which CT appears to be both accurate and cost-effective — though usually no more so than ultrasonography. A considerable literature questions the use of CT, particularly as a primary diagnostic tool for acute appendicitis in children. A poll of pediatric radiologists (Slovis, Pediatr Radiol, 2002) suggested that perhaps one third of all CT studies could be replaced by alternative approaches or not performed at all.

Q: What is a gray (Gy) — the unit used to describe the radiation dose delivered by a CT scan?
A: Various measures are used to describe the radiation delivered by CT scanning, the most relevant being absorbed dose, effective dose, and CT dose index. The absorbed dose is the energy absorbed per unit of mass and is measured in grays (Gy). One gray equals 1 joule of radiation energy absorbed per kilogram.


Foley's catheter insertion in male and female