Today's News

Saturday, February 26, 2005

Three studies examine causes, prevention of ACL injuries in women

New research presented yesterday includes important findings on the causes of anterior cruciate ligament (ACL) injuries in female athletes, such as posture and body movement. These findings may be key in the effort to find ways to prevent these types of injuries.

Athletes are particularly susceptible to ACL injuries because this ligament, which connects the femur to the tibia, can be torn when a person changes direction rapidly, slows down from running or lands from a jump. These tears prevent the knee from being able to support the body, and often require surgical repair.

Women experience ACL injuries at a significantly higher rate than men. Data collected since 1995 finds that the incidence of ACL injuries among women basketball players is twice that for men, and that female soccer players are four times more likely to experience an ACL tear than their male counterparts. Much research has been conducted to determine why these differences exist, and how these painful injuries can be prevented.

Trunk and hip motion
Presenting his Paper No. 207 yesterday, Spero G. Karas, MD, reported on research at the University of North Carolina-Chapel Hill that examined the mechanical motion of the trunks and hips of elite soccer players (18 women and 17 men) as they performed two types of side-step cutting maneuvers, a "run-and-cut" and a "jump-and-cut." Researchers collected trunk and hip kinematics on each athlete's dominant leg with an electromagnetic motion analysis system. They performed independent t-tests to compare men and women on each dependent variable.

The study found that the women tended to hold their trunks and hips in a more erect posture while performing running and jumping maneuvers, suggesting that this difference may contribute to the increased risk of ACL injury. During initial ground contact and at maximal joint angles, women athletes demonstrated significantly less trunk flexion in both the "run-and-cut" and the "jump-and-cut" tasks (p < .05). Women also had increased hip internal rotation during the "run-and-cut" task (p=.002)

As the first study to look at the effect of trunk and hip motion on ACL injury, these findings provide a new avenue for physicians and trainers looking to help female athletes protect their ACLs. Trunk and hip kinematic differences may be an unrecognized contributor to the increased incidence of ACL injury in female athletes. The results suggest that training female athletes to perform athletic maneuvers with more trunk flexion may decrease the risk of ACL injury.

"Knowing that the trunk and hip may be an important variable in this problem, we should consider appropriate intervention strategies," said Dr. Karas. "These would include instructing and training female athletes to perform maneuvers in a less erect posture, stressing the importance of trunk and knee flexion."

Dr. Karas was assisted in his research by Michael DiStefano, MS, and Troy Blackburn, MS, of Chapel Hill, N.C.; Darin Padua, PhD, of Charlottesville, Va., and William E. Prentice, PhD, of Pittsboro, N.C.

Proprioception differences
Data collected from a separate study and presented in Paper No. 238 suggested that there were inherent gender differences in elite athletes' ability to reproduce various squatting positions, particularly with regard to more erect posturing. Researchers at the Medical College of Ohio, compared collegiate soccer players - 33 men versus 33 women.

"The women athletes were able to reproduce deep squatting positions just as well as their male counterparts; however, women do not stay in these bent-knee positions during sport," said lead researcher Henry T. Goitz, MD. "This could be that perhaps women fatigue in these positions more easily than men, or perhaps it is just a habit. If either is the case, female athletes should be conditioned to place themselves in a more protective position in sport activities, and, thereby, reduce ligament injury."

The research team also examined two additional groups in which leg control is an integral part of training-gymnasts and ballet dancers. Gymnasts have a relatively high ACL injury incidence, but ballet dancers have an extremely low incidence. Data collected from studying 22 elite female gymnasts (level 8 and above) was nearly identical to that of the female college soccer players. However, the study of eight female professional ballet dancers found that this group exhibited superior scores compared to all groups, both men and women. "The training of the female ballet dancer may provide the key to our understanding of ACL injury prevention," explained Dr. Goitz.

Working with Dr. Goitz were Lynsey Ebel, BS; Rebecca Mocniak, BS; and Jeff Nofitz, PT, all of Toledo, Ohio.

The Pill's effect
Another study pinpointed an additional method to reduce women's chances of suffering an ACL injury. The primary author of Paper No. 204, Paul A. Martineau, MD, determined that taking the oral contraceptive pill may help women reduce their chances of experiencing ACL injuries. The study of 127 female athletes found that those who used oral contraceptives had less knee laxity in their ACLs, making them less likely to suffer injuries to those ligaments.

"While more research needs to be done with a larger group of women for a longer period of time, the preliminary findings are encouraging," Dr. Martineau said. "This study has provided evidence that oral contraceptives may provide women with some protection to the ACL."

Working with Dr. Martineau were Eric Lenczner, MD, and Mark L. Berman, MD. All are from Montreal, Quebec, Canada.

Motion differences
Gender differences were also found in the mechanical motion of the knee, according to Poster P361. Researchers studied a group of 18 male and 17 female high school basketball players as they performed lateral jumps, a task that is known to cause noncontact ACL injuries. Female athletes bent their knees less and turned them in more than the males, a difference that could be partially responsible for the disparity in the number of ACL injuries.

"Because women are more at risk for ACL injuries, they need to pay particular attention to prevention," said research coordinator Timothy C. Sell, PhD, PT, of Pittsburgh. "Knowing that there are differences in the way female athletes move can aid in the creation of training programs to reduce the forces that can cause these injuries. This information needs to be shared directly with the coaches and trainers who work with college, high school and even junior high athletes."

Working with Dr. Sell were Cheryl M. Ferris, PhD, of Bridgeville, Penn., and John P. Abt, MS; Yung-Shen Tsai, MA; Joseph B. Myers, PhD; Freddie H. Fu, MD; and Scott M. Lephart, PhD., all of Pittsburgh.

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