Significantly fewer prosthetic joint infections as well as other revision knee operation complications occurred within one year after surgery if a person gets both knees replaced at the same time instead of stretching out the operations over time. Simultaneous replacement may be the way to go according to a new study, instead of doing one at a time on separate occasions.

According to the American Academy of Orthopedic Surgeons (AAOS), there are about 270,000 knee replacement operations performed each year in the United States. Although about 70% of these operations are performed in people over the age of 65, a growing number of knee replacements are being done in younger patients. Orthopedic surgeons evaluate patients individually. Recommendations for surgery are based on a patient’s pain and disability, not age. Total knee replacements have been performed successfully at all ages, from the young teenager with juvenile arthritis to the elderly patient with degenerative arthritis.

However, simultaneous replacement was associated with a moderately higher risk of adverse cardiovascular outcomes within 30 days, according to a study presented this week at the 2011 Annual Meeting of the American Academy of Orthopedic Surgeons (AAOS).

John P. Meehan, MD, study author and orthopedic surgeon from the University of California, Davis explains:

“Our study found that the risk of developing a serious joint infection that required an additional knee revision surgery was two times higher in patients who had staged knee replacements compared to the patients who had both knees replaced at the same time (2.2% after staged knee replacements and 1.2 percent after bilateral knee replacements). These findings indicate that performing simultaneous knee replacements would significantly reduce the incidence of major orthopedic complications, and at the same time reduce the number of hospitalizations and the number of operating room sessions.”

11,445 patients who underwent simultaneous bilateral knee replacement and 23,715 patients who had both knees replaced in two stages several months apart were compared in the new study.

The results were interesting to say the least. Those persons having both knees replaced at the same time demonstrated a higher risk of heart attack and pulmonary embolism, similar risk of death and stroke, but lower risk of major joint infection or major mechanical malfunction.

The knee is the largest joint in the body. Normal knee function is required to perform most everyday activities. The knee is made up of the lower end of the thighbone (femur), which rotates on the upper end of the shin bone (tibia), and the kneecap (patella), which slides in a groove on the end of the femur. Large ligaments attach to the femur and tibia to provide stability. The long thigh muscles give the knee strength.

The joint surfaces where these three bones touch are covered with articular cartilage, a smooth substance that cushions the bones and enables them to move easily. All remaining surfaces of the knee are covered by a thin, smooth tissue liner called the synovial membrane. This membrane releases a special fluid that lubricates the knee, reducing friction to nearly zero in a healthy knee. Normally, all of these components work in harmony. But disease or injury can disrupt this harmony, resulting in pain, muscle weakness, and reduced function.

This particular study also found that the risk of adverse cardiovascular events such as having a heart attack or developing a blood clot that travels to the lungs was higher after undergoing simultaneous knee replacements, but there was no significant difference in overall mortality.

Source: American Academy of Orthopedic Surgeons News Release

Written by Sy Kraft, B.A.