The role of shoe design in ankle sprain rates among collegiate basketball players

Journal of Athletic Training, May-June, 2008 by Claudia K. Curtis, Laudner, Kevin G., Todd A. McLoda, Steven T. McCaw

Ankle sprains are one of the most common injuries in the United States, accounting for as many as 23000 injuries per day. (1) Authors (2) of a study in 1983 reported that the United States spent approximately $2 billion that year on moderate and severe ankle sprains: the 2008 estimate is $4.22 billion with inflation? Thus, although ankle sprains are often seen as commonplace, the economic ramifications are significant. Studies (4) l0 of athletes have shown that these statistics carry over to the sports world, particularly basketball. Basketball players frequently land on another competitor's foot, causing an awkward, plantar-flexed inversion moment and stretching the lateral ankle ligaments beyond their capacity, resulting in an ankle sprain. (4,9,11-15) These ankle sprains leave the competitor with initial pain and swelling (6,7) but can also lead to long-term problems, such as costly medical bills, subsequent sprains, (16,17) decreased strength, (6,16) instability (6,16) delayed muscle reaction time, (16,18) and disability. (16,18) Preventing ankle sprains becomes critically important to basketball players, coaches, strength and conditioning experts, team physicians, and certified athletic trainers (ATs) in order to minimize time and money lost and maximize their success. (7.9,14-17)

The mission statements of many athletic footwear manufacturers focus on creating innovative designs using technology to improve comfort and athletic performance. (19-21) Some shoes are marketed to absorb energy during impact and release it during liftoff, aiming to increase force output. According to the Web site, (21) Nike shoes are reported to increase vertical jump height and improve propulsion ability, resulting in faster sprint times. Currently, this concept has been delivered in the form of spring-like columns ("cushioned column systems") under the heel of the shoe in place of conventional heel counters. (22) The effect of this design on ankle sprain risk has not been reported. Therefore, the purpose of our study was to determine the effect of shoes with cushioned column systems under the heel on the frequency of lateral ankle sprains. We hypothesized that collegiate basketball players wearing the cushioned column shoe design would have a higher incidence of lateral ankle sprains than those not wearing this shoe type.

METHODS

Participants

Twenty-two collegiate ATs from National Collegiate Athletic Association (NCAA) Divisions I, II, and III institutions participated in this study. The ATs recorded the type of shoe, practice and game exposures, and lateral ankle injuries for 141 male and 89 female collegiate basketball players between the ages of 18 years and 24 years (age = 20.2 [+ or -] 1.5 years).

Athletes with a history of a lower extremity injury within the past 3 months or any neurologic condition were excluded from this study. Consent to participate in this study was obtained by each team's AT, and the study was approved by the Illinois State University Institutional Review Board.

Instrumentation

A survey was constructed to address the specifics of each lateral ankle sprain encountered throughout the 2005-2006 basketball season. The survey was posted online at a Web page accessible to the ATs to record lateral ankle sprains and total exposures (practices and games) on a weekly basis. The AT was responsible for recording information about each sprain, including ankle sprain type and any prophylactic measures in place when injured. Other information recorded included sex, division of competition, and the setting in which the sprain occurred (practice or game). We specifically looked at the type of shoes worn when the lateral ankle sprain was sustained. The AT was required to document the number of total exposures as a weekly demographic measurement. An exposure was defined as 1 athlete's participation in 1 game or practice. (23)

Procedures

A list of all NCAA participating institutions was obtained using the 2005 NCAA directory. (24) A search of the institutions' Web sites was performed to obtain contact information for those ATs working with basketball players. All ATs were contacted via e-mail about participating in the study. The 22 ATs who consented were responsible for maintaining records on each ankle sprain they evaluated and treated during the 2005-2006 collegiate basketball regular season. An ankle sprain was defined as an injury to the ankle ligaments. (25) Only injuries to the ankle ligaments resulting in absence from at least 1 day of activity were recorded by ATs as ankle sprains. (26) Cushioned column shoes were defined by Aguinaldo and Mahar (22) as rearfoot cushioning systems made in the form of spring-like columns.

At the beginning of the season, the ATs at participating schools received a cover letter describing the purpose of our study along with a sample questionnaire. This form provided the AT with a guide to the information to be recorded during the season in an attempt to improve the return rate. All ATs were informed that a cushioned column shoe should be defined as one with a spring-like rearfoot cushioning system, column-like in design. Each AT filled out questionnaires on a weekly basis documenting the number and types of exposures encountered that week. In this information, the ATs were required to stratify their exposures based on prophylactic measures in place during the activity. Any ankle injuries encountered that week were reported at that time as well. Specifics about the ankle sprain were documented (Table 1). Participants with questions were directed to correspond with the authors via e-mail. We sent monthly e-mails reminding the ATs to continue to submit their data.