02 Oct ACL Injury Risk Factors Different For Men than Women
MedicalResearch.com Interview with:
Dr. Bruce Beynnon
McClure Professor of Musculoskeletal Research
Dept Orthopedics and Rehabilitation
University of Vermont College of Medicine
Burlington, VT 05405-0084
Medical Research: What are the main findings of the study?
Dr. Beynnon: The anterior cruciate ligament (ACL) is an important stabilizer of the joint, and the study investigated how geometry of this ligament and surrounding bone is related to non-contact injury of this ligament. Specifically, the study focused on MRI-based measurements of the size of the ACL, measured as its volume, and the size of the femoral intercondylar notch, or the small space located in the center of the femur in which the ACL resides. Our study revealed that a decrease in the volume of the ACL and a decrease in the size of the intercondylar notch were associated with an increased risk of suffering a non-contact ACL injury in athletes.
This finding may be explained by the fact that a smaller ligament is associated with a decrease in its biomechanical properties, such as a smaller ultimate failure load. An alternative explanation is that a decreased femoral intercondylar notch size could result in a greater tendency for the ACL to impinge against the walls of the femoral notch during high demand activities, and increase the risk of injury.
The investigation was a longitudinal study with a nested case-control analysis of young, healthy high school and college athletes. The investigation was rigorously designed to control for age, sex, and participation on the same sports team. This enabled us to determine which combination of geometric parameters of the ACL and adjacent bony structures influence risk of suffering a first time non-contact ACL injury.
Medical Research: What was most surprising about the results?
Dr. Beynnon: Our study conducted separate analyses of the data obtained from males and females and this revealed that ACL volume is more strongly associated with risk of injury in males, while femoral intercondylar notch ridge is more strongly associated with risk in females. When included together in analysis that adjusts for body weight, the effects of the geometric measures of ACL and femoral notch are similar in males and females. If body weight is not taken into consideration, ACL size is not associated with ACL injury risk in females. These findings stress the importance of investigating risk factors in combination and indicate that the risk factors for an ACL injury may be different for males in comparison to females. This suggests the mechanisms for this devastating injury may be different between the sexes.
Medical Research: What should clinicians and patients take away from your report?
Dr. Beynnon: The important finding to take away from our report is that the risk factors for suffering an ACL injury are multifactorial and different for males and females. The models including femoral notch and ACL injury were similar for males and females, only when the results for females were adjusted for body weight. For males and females, a decreased ACL volume and narrower intercondylar femoral notch in combination with an increased bony ridge thickness of the notch was associated with increased risk of suffering non-contact ACL injury. An individual who has the characteristic of a small femoral intercondylar notch alone has less inherent risk of injury compared to an individual who has a small notch in combination with a large femoral intercondylar notch ridge or a smaller ACL.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Beynnon: Future research should continue to build on the results of this study. We have broadened our investigation to include ACL and notch geometry in combination with the geometry of the tibial plateau articular surface, the geometry of the menisci, and the geometry of the tibial spines. Other non-anatomic measurements have also been identified as risk factors for ACL injury, including family history, muscle strength, knee laxity, and generalized joint laxity. Further investigation should consider both anatomic and non-anatomic based measurements to continue to build a more comprehensive understand of what influences the risk of suffering an ACL injury. In addition, knowledge of the risk factors for injury helps us establish an improved understanding of the mechanisms by which the injury occurs. Further, findings from this study have the potential to aid in the development of new screening tools that may be used to identify individuals at increased risk for injury, and the development of improved intervention programs. The incidence rates for ACL injuries have been reported to range between 200,000 and 400,000 per year in the US alone. Current treatment options are not effective at preventing the early onset of osteoarthritis that can appear 10-15 years after the injury. Consequently, injury prevention is the best strategy to reduce the incidence of ACL injury, and mitigate its long-term effects.
Whitney DC1, Sturnick DR1, Vacek PM2, DeSarno MJ2, Gardner-Morse M1, Tourville TW1, Smith HC1, Slauterbeck JR1, Johnson RJ1, Shultz SJ3, Hashemi J4, Beynnon BD5.
Am J Sports Med. 2014 May 27;42(8):1796-1805. [Epub ahead of print]