Knee Shape May Predict Who'll Benefit From ACL Surgery, Study Says
X-rays could aid decision-making, researchers note
Friday, July 19, 2013
"This is the first study to show that after your ACL is ruptured, the changes in the mechanics of the knee can really be affected by the shape of the knee," Suzanne Maher, associate director of the biomechanics department at the Hospital for Special Surgery in New York City, said in a hospital news release.
"Previously, researchers had only conducted studies looking at whether a particular knee shape makes a person more likely to have an ACL injury, specifically in the athletic population," she noted.
Each year in the United States, about 200,000 people suffer an ACL tear, and these injuries cost the health care system $1 billion. An ACL tear increases the risk of developing osteoarthritis, joint degeneration and loss of cartilage that helps stabilize the knee.
ACL reconstruction may prevent these problems, but not all patients require this surgery. Some people have more stable knees and won't develop further knee problems after an ACL tear. Skipping surgery may be an option for patients who do not play sports that involve pivoting, such as soccer or basketball. However, it's difficult to identify patients who can avoid surgery without developing further problems.
In this study, published online ahead of print in Proceedings of the Institution of Mechanical Engineering, researchers conducted experiments with nine knees from dead people to examine how knee shape affects knee mechanics during walking after an ACL tear.
The knees were outfitted with a sensor that measured the contact stresses of a critical weight-bearing area on the top of the shinbone called the tibial plateau. The knees were then mounted on a machine that replicated the action of walking. The knees were tested before and after the ACL was cut to mimic a tear.
The results showed that the shape of the knee can help determine which patients are more likely to develop further cartilage damage in the front and the back of the knee after an ACL tear. This means that X-rays may help doctors identify patients who do not require surgery.
"This is a limited study because these are dead knees, we are only looking at walking, it is only a small sample size, we have focused on the inside of the knee, etc., but it provides a glint of information about how the knee functions after an ACL rupture," Maher pointed out in the news release. "Even though this is a lab-based study, it suggests that the shape of a person's knee may be ultimately used as some guidance as to whether certain patients should have their ACL replaced or repaired versus other patients."