Rates of ACL Injuries in Females and Males

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Different rates of ACL injuries in females and males explored

ORLANDO, Fla.--Research has confirmed that females have a disproportionately higher number of injuries to their anterior cruciate ligaments (ACL) than males participating in the same sports activities. Two new studies presented at the 67th annual meeting of the American Academy of Orthopaedic Surgeons discovered probable causes for the higher injury rate and ways to reduce future injuries.

The studies reported the movements of females--whether they are participating in contact or noncontact activities--create more ACL damage than their male counterparts.

One study of ACL injury risk in females showed that women are at a higher risk for ACL injuries because they use their leg muscles differently than males. A study of 51 collegiate basketball and soccer players (25 female and 26 male) looked at maximum voluntary contraction (MVC) for knee bending and extension in opposite legs. The researchers watched three consecutive, two-minute knee bending and extension exercise routines performed by the athletes to follow their actions of each leg muscle.

Each athlete's muscle contractions were measured using electromyography (commonly known as an EMG), the diagnostic test evaluates the function of nerves and muscles during various activities. The results show different patterns of muscle use and function between the female and male athletes.

"Our most important finding confirms that females seem to activate their quadriceps muscles during some exercises which may put them at higher risk for ACL injuries," said study author Klane White, MD, resident, department of orthopaedic surgery, University of California at San Diego, San Diego, Calif.

Dr. White also noted that additional studies may be able to show how female athletes can reduce ACL injuries by altering their training programs. "Long-term, we may be able to change muscle firing characteristics so that a better balance is created in the female ACL which will reduce their higher risk of ACL injuries."

Co-authors of the study, from the department of orthopaedic surgery, University of California at San Diego, are Robert A. Pedowitz, MD, PhD, chief of sports medicine; Alan R. Hargens, PhD, professor of orthopaedics; Steven Lee, MD, resident; and Adnan Cutuk and Marcia Klaiber, ATC, department of athletics, University of California at San Diego.

In a related study on ACL injuries in females, a new four-year prospective knee evaluation followed 956 students at West Point Military Academy to determine why some students injured their ACLs and others did not. Researchers found an injury rate of .04 percent for females and .027 percent for males.

A research team of orthopaedic surgeons and physical therapists evaluated both knees of each student. The notch width index (NWI) which measures the notch width, the area where the ACL resides, between the ligament and the knee joint, the eminence width index (suggesting ACL size) and the notch width/eminence width (NW/EW) ratio which was hypothesized to reflect ACL size in relationship to its confining notch on the knee joint, were recorded.

"We found a correlation between the size of the NWI and ACL tears for both men and women. However, the EWI only predicted ACL tears in the male population," said John M. Uhorchak, MD, chief, department of surgery, Keller Army Community Hospital, West Point, N.Y. "ACL injuries are really multi-faceted and this is another piece of the puzzle that will help orthopaedic surgeons continue to advance their knowledge to improve patient care."

Co-authors of the study are Patrick St. Pierre, MD, on-staff at Madigan Army Medical Center in Tacoma, Wash.; Dean C. Taylor, MD, chief of orthopaedics and David O. DeWitt, PA, staff physician assistant, Keller Army Community Hospital, West Point, N.Y.; Billy Maloney, PhD, department of mathematics, U.S. Military Academy, West Point, N.Y.

The 24,500-member American Academy of Orthopaedic Surgeons (www.aaos.org) is a not-for-profit organization that provides education programs for orthopaedic surgeons, allied health professionals and the public, and is an advocate for improved patient care.

In the first year of the United Nations-declared Bone and Joint Decade (2000-2010) (http://www.boneandjointdecade.org), the Academy is holding its annual meeting at the Orange County Convention Center, Orlando, March 15-19.

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