Published 11/1/2007
Carolyn Rogers

Simple diagnostic test may predict foot and ankle instability

Study also finds foot type is unrelated to instability

A patient’s risk of foot and ankle injury does not appear to be related to foot type—cavovarus, flatfoot, or neutral—according to a study presented at the American Orthopaedic Foot & Ankle Society’s (AOFAS) 2007 Annual Meeting in Toronto. The study, led by Richard T. Laughlin, MD, of Wright State University, Dayton, Ohio, reevaluated the correlation between foot types and the incidence of foot and ankle injuries in college athletes.

The purpose of the study was threefold, Dr. Laughlin says:

  • To describe the demographics of foot alignment in a college athlete population
  • To try and predict who might be at risk for injury
  • To evaluate the interobserver reliability of a recently proposed diagnostic test for determining patients’ malleolar indices

For the study, Dr. Laughlin and his colleagues measured the ankles of 524 University of Dayton athletes from various sports. The athletes also received physical examinations to detect the incidence of subtle cavovarus feet, flat feet, or neutral feet. The school’s athletic trainers observed the athletes for any ankle injuries.

Simple diagnostic test
Previous studies identified a posteriorly positioned fibula as a contributing factor for recurrent ankle instability. In those studies, the position of the fibula was evaluated using radiographic analysis, computed tomography, and magnetic resonance imaging.

In contrast, this study used a simple clinical diagnostic test—previously described by John E. McDermott, MD, and Pierce E. Scranton Jr., MD—for determining the patient’s malleolar index. A positive malleolar index means that the lateral malleolus is posterior to the medial malleolus. An index of 1.3 or greater has been associated with an increased risk of ankle instability.

Two medical students and two orthopaedic surgeons used this simple test to measure the Ohio athletes’ malleolar indexes. Seventeen of the student athletes served as a control group, and their feet were measured by all four investigators.

This simple method of determining a posteriorly positioned fibula proved to be extremely reliable, according to the researchers.

“The intraclass correlation coefficient in our study for interobserver reliability was 0.919,” said Gurpal Ahluwalia, MD, who presented the results at the AOFAS meeting. “This means that there was slight variation between the observers, but overall they were measuring from the same point to the same point for each participant.”

Comparing injury rates
The researchers also investigated whether any of the foot types had a higher injury rate compared to the others and evaluated whether the malleloar index was different between injured athletes and noninjured athletes for each foot type.

Overall, 12 percent of the athletes had subtle cavovarus feet; 24 percent had flat feet, and 64 percent had neutrally aligned feet, according to the study.

The overall injury rate was approximately 26 percent.

“Injury rates for the individual foot types were not significantly different from one another,” Dr. Laughlin reports.

Among athletes with a malleolar index of 1.3 or greater, those with flat feet had a 28 percent injury rate, those with cavovarus feet had a 23 percent injury rate, and those with neutral alignment had a 24 percent injury rate.

According to Dr. Laughlin, the study is exciting not only because it was performed on college atheletes, but also because the test can easily be used by others.

“The method was found to have excellent interobserver reliability and thus could be easily performed by people involved in the daily care of athletes,” he says.

Future research
This research study will continue as Dr. Laughlin conducts further data analysis to determine if recurrence of injury is related to either alignment or malleolar index.

“Foot type may have an effect on injury patterns and, more importantly, on the ability of the athlete to recover,” he says. “Chronic injuries, such as peroneal tendon problems, stress fractures, and posterior tibial tendinitis, have been linked to foot alignment. Looking at an athlete’s foot alignment may allow for preventive measures to be taken and may alert the athletic trainer to those athletes who may not recover fully from injuries or be at risk for chronic conditions.”