Avascular Necrosis
From Medical-Wiki
When there is cellular death of bone components because of ischemia, the process is known as avascular necrosis. This condition can occur in the context of a variety of circumstances, usually affecting the epiphysis of long bones, but it most commonly occurs in the hip. Crucial to the treatment of AVN is early diagnosis. Early intervention can, for example, prevent the loss of the femoral head and the subsequent need for surgical replacement.
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Causes
The most common anatomic feature of those bones prone to AVN is a single terminal blood supply. This occurs in the femoral head, carpals, talus, and humerus. The limited collateral blood supply makes interruption of blood supply makes this more likely along with resultant necrosis of marrow, medullary bone, and cortex. [1]
Obviously, AVN can occur if there has been severe trauma to a bone, such as a fracture. Other factors leading to a higher incidence include the use of corticosteroids and heavy use of alcohol. Less common causes include sickle cell disease, Gaucher’s disease, lupus, the “bends,” and chemotherapy. [2]
Signs & symptoms
AVN may be completely asymptomatic. AVN of the hip may present with groin pain—worse when standing or walking. AVN of the wrist may present with wrist pain or finger weakness. If AVN occurs in the knee, the typical presenting complaint is knee pain, and the shoulder produces shoulder pain. [3]
Diagnosis
Government guidelines for AVN of the hip call for plain films (in the hip to include frog-leg views) as the most appropriate initial evaluation. Unfortunately, other than imaging techniques, there are no other specific lab tests or techniques to identify AVN. The guidelines thus conclude, “Radiographs are the least expensive and most widely available imaging technology. Radiographs should be obtained as the initial study in every patient suspected with AVN.” [4]
When there is need for additional imaging, MRI has proved to be far superior to CT or bone scans. [5]
Treatment
AVN is staged from 0 to stage VI. Medical management depends upon the stage of disease being treated. However, no medical management has been demonstrated to prevent and arrest AVN. Limited weight bearing and pain control can be used if the involvement is less than 15% and removed from a weight bearing region. Immobilization is sometimes used. Preliminary studies have been done on the use of bisphosphonates. Statin use is also being investigated.
There is really no consensual surgical treatment of AVN. In those stages that are precollapse, core decompression and possibly bone graft is the most common surgical procedure. Later in the disease, femoral head necrosis is most commonly treated with arthroplasty. [6]
Legg-Calvé-Perthes disease
Legg-Calvé-Perthes disease (LCPD) is AVN of the capital femoral epiphysis of the femoral head occuring in children between the age of 3 to 12 years of age. The median age of patients is 7 years. In 15% to 20% of cases, disease is bilateral.
A commonly accepted scenario for the disease postulates an initial interruption of blood supply that causes bone infarction in the face of continued normal growth of the articular cartilage. With the onset of revascularization, some children develop LCPD while others develop normal growth. LCPD occurs with the occurrence of a subchondral fracture—in response to normal activity.
Treatment for LCPD usually consists of observation and rest. Basically, efforts are directed towards keeping the femoral head within the acetabulum so that the acetabulum may serve to mold its regrowth. If diagnosis is made in young children, there is a better chance that degenerative changes will be avoided. [7]
