Researchers at Hospital for Special Surgery (HSS) have provided the first evidence that the shape of a person’s knee could be a factor in the decision of whether a patient should undergo anterior cruciate ligament (ACL) reconstruction after an ACL tear.
“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, ” said Suzanne Maher, Ph.D., associate director of the Department of Biomechanics at HSS, New York City, in the July 2, 2013 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.”
The investigators used nine cadaveric knees to examine how knee shape impacts knee mechanics during walking, after a person has torn their ACL. The researchers used a sensor that measured the contact stresses of a critical weight-bearing area (the tibial plateau). They then mounted the knees on a machine that flexed and extended the specimens while applying forces in many directions (mimicking walking).
Asked about the most surprising thing to come to light, Dr. Maher told OTW, “The most surprising finding was the variability in contact mechanics after ACL rupture; with some knees showing significant increases in contact stresses and others showing minimal or no changes.
“The knees that showed changes in the front of the knee had specific shape features. For example, they had a less concave tibial plateau, ” said Dr. Maher in the news release. “If the tibial plateau has a very deep valley and then you have a femur (thigh bone) sitting in a deep well, that is going to give you a very stable knee. So, when you tear your anterior cruciate ligament, it is not going to have a huge effect.” Increased tibial slope was another predictor of increased stress.
Regarding future research, Dr. Maher told OTW, “We measured changes in contact stresses in cadaveric knees after ACL rupture, but it is unclear how changes in contact stress relate to tissue damage in patients knees. We are about to embark on an innovative study, funded through the AOSSM [American Orthopaedic Society for Sports Medicine], where we will measure contact stresses in patients’ knees and then follow them with MRI scans—in a goal to connect contact stress with likelihood of tissue damage. Ultimately, we will use this information, together we with what we have learned from our cadaveric study, to design a clinical study to more comprehensively define if specific osseous anatomic features can predict increased likelihood of joint degeneration after ACL injury.”
“The complexity of the response of the human knee to ACL injury is in part driven by variability in osseous geometry. Future clinical-based studies that can explore this issue in greater detail will conceivably add yet another dimension to the decision of choosing ACL reconstruction after injury.”
