Increasing prevalence of anterior cruciate ligament injuries in a collegiate population.
Abstract: Objective: To detect a possible increasing trend in the annual prevalence of anterior cruciate ligament (ACL) injuries in a collegiate population and whether gender, sport, or year of the participant was predictive of a prior ACL injury.

Design: Retrospective case series

Setting: West Virginia University

Participants: Review of 3,079 physical examination forms for prior ACL injury in athletes presenting for collegiate participation from 1996-2008.

Main Outcome Measures: Presence or absence of ACL injury at presentation for preparticipation physical examination.

Results: There was a slight increase in the annual prevalence of ACL injuries over the study period. Gender and sport of the participant were not predictive of a prior ACL injury.

Conclusions: Prevalence of ACL injuries increased over time in the population. Further research is needed to determine if this result is reflective of a growing national trend in athletes with a prior ACL injury presenting for collegiate participation.
Article Type: Clinical report
Subject: Prevalence studies (Epidemiology) (Analysis)
Sports injuries (Risk factors)
Sports injuries (Demographic aspects)
Anterior cruciate ligament (Injuries)
Authors: Lively, Mathew W.
Feathers, Christopher C.
Pub Date: 07/01/2012
Publication: Name: West Virginia Medical Journal Publisher: West Virginia State Medical Association Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2012 West Virginia State Medical Association ISSN: 0043-3284
Issue: Date: July-August, 2012 Source Volume: 108 Source Issue: 4
Geographic: Geographic Scope: United States Geographic Code: 1USA United States
Accession Number: 310150678
Full Text: Introduction

Rupture of the anterior cruciate ligament (ACL) from sports participation has been the focus of many studies in recent years with most centering on the difference in incidence between male and female athletes. Although the overall rate of ACL injuries has remained stable in the collegiate population (1-3) and possibly increased in high school populations, (4) most studies confirm that female athletes, at all levels of participation, suffer ACL injuries at a significantly higher rate than their male counterparts. (1-9) An increased injury rate in high school athletes coupled with a rising number of athletes participating in high school sports could result in a larger number of ACL-injured athletes presenting for collegiate participation.

The purpose of this study is to detect a potential increasing trend in the annual prevalence of ACL injuries in a collegiate population over a thirteen-year period and whether the gender, sport, or year of participation was predictive of a prior ACL injury.

Methods

All athletes at our institution are required to undergo a physical examination prior to the start of their participation. The process includes questions about previous joint injuries and a detailed musculoskeletal examination by either a team physician or a nationally certified athletic trainer. At the time of the physical examination, the presence of a previous ACL injury, the year it occurred, and whether or not it was surgically reconstructed was noted on the examination form. One of the authors reviewed all examination forms prior to the athlete being cleared for participation. The form was then placed in the athlete's medical record.

A retrospective review of all examination forms from 1996-2008 was preformed with documentation made of previous ACL injuries, the gender of the athlete and the sport involved. An athlete suffering more than one ACL injury was recorded as a single occurrence for the purposes of determining the prevalence rate. The study protocol was approved by the institutional review board.

Statistical analysis was performed using a multiple logistic regression model with a two-level dependent variable of presence or absence of an ACL injury and independent variables of sport, gender and year. A simple linear regression model was utilized to show trends in the annual prevalence rate of ACL injuries over time.

Results

A total of 3,079 preparticipation physical examinations were performed from 1996-2008. Seventy-seven athletes (2.5%) had a prior ACL injury with football and soccer alone accounting for 46 of the total number of ACL injuries. The number of ACL injuries by sport and gender is presented in Table 1 and the number of ACL injuries per year is listed in Table 2. Independent predictors of sport (p=0.41) and gender (p=0.71) were not statistically significant in explaining the variability in ACL injury. However, the independent predictor of year (p=0.02) was statistically significant in explaining injury variability. The graph of a simple linear regression model performed for the prevalence rate of ACL injury per year is illustrated in Figure 1. Sport and gender were excluded from the linear regression model given no statistical significance. The odds of an ACL injury being present showed a slight increase of 1.1 per year resulting in an increasing trend in the prevalence rate over the study period. Across the entire thirteen year period, athletes in 2008 had a 2.7 greater odds of having a previous ACL injury versus those who arrived in 1996.

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Discussion

The results of this study show a slight increase in the annual prevalence rate of ACL injuries in a collegiate population over a thirteen year period ending in 2008. Neither the gender nor the sport of the participant was a predictive of the presence of an ACL injury at the time of the preparticipation examination.

As the large majority of athletes presenting for a preparticipation examination at our institution are direct high school graduates as opposed to transfers from another college, our yearly prevalence could be a reflection of changes in the incidence of ACL injuries in high school athletics. Most of the literature on high school knee injuries cover the time period between 1995 and 2006 (4,8,10,11) corresponding well with the 1996-2008 time frame in our study. Comparison of overall data between high school and college is difficult, though, because most studies, either high school or collegiate, focus primarily on the incidence of ACL injuries in basketball and soccer alone. Also, there is limited high school data on the rate of ACL injuries over time as most studies examine only total number of injuries during a specific time period.

Micheli et al (4) did study the number of high school athletes undergoing ACL reconstructive surgery for soccer and basketball from 1992-1997. Their data showed an increase over time in the number of ACL surgeries for both genders but females had a significantly higher incidence of surgery over males in both soccer and basketball. (4) Other studies (8,10-12) also support a higher incidence of knee surgeries in female high school athletes compared to their male counterparts. Figures from the National Federation of State High School Associations show a 61.3% increase in the number of females participating in high school soccer from 1995-2007 compared with an increase in male participation of 33.2%. (13) Although not as large, most high school sports also show increases in the number of participants over the same time period. A larger number of competing high school athletes coupled with an increasing rate of ACL surgeries could result in more athletes presenting to college with a prior ACL injury. Although our study showed that sport and gender were not predictive of a prior ACL injury, it seems reasonable to assume the increased annual prevalence of injury in our study is reflective of an underlying rising incidence of injury in high school athletics. Another possible explanation is the number of high school ACL injuries has not increased, but instead, more athletes are continuing participation after injury than in previous years. Data from the National Football League (NFL) combine physicals show that the odds of failing an examination at the professional level due to an ACL injury has declined over time. (14) Future research looking at the rate of high school ACL injuries over time would be helpful in determining the source of a rising prevalence in college athletes.

In collegiate athletes, the overall rate of ACL injury has remained stable since 1989 (1-3) but females continue to show a 2- to 4- fold increase in the incidence of ACL injuries compared to males. (1-3,5-7,9) In our study, football players had the highest number of ACL injuries, but female soccer athletes had a higher percentage of injuries per participant. Due to the wide variation in number of participants, direct statistical comparison between sports was not performed in this study.

There are limitations to this study. One is that the results are from one institution; our data may not be indicative of an increasing prevalence in ACL injuries on a national scale. Similar studies from other institutions would aid in confirming the results of this study. Another limitation is that no documentation was made on the physical examination form of how the athlete originally injured the ACL. As such, we cannot determine if athletes were participating in the same sport at the time of injury as they desired to play in college. It is also possible the athletes suffered the ACL injury during conditioning activity that may not have been directly related to their specific sport activity. Due to these limitations, the study was designed to reflect only the overall prevalence of ACL injuries at presentation to collegiate athletics. The data was also obtained in part from athlete recall, although the impact of this potential error should have been minimized by the fact that all athletes underwent a physical examination of the knee by an experienced operator who should have been able to detect an unreported ACL deficit knee and/ or observed the presence of a scar from a ligament reconstruction.

The results of this study show an increasing prevalence of ACL injuries in a specific collegiate population. If these findings are reflective of a general trend in collegiate athletics, it lends support to initiating prevention strategies in high school athletes since such programs can reduce the rate of ACL injuries, particularly in female athletes. (15)

Further research on the incidence of ACL injuries over time at the high school level would be helpful in determining whether an increase in the collegiate prevalence is due to an overall increase in high school injuries versus more athletes continuing participation after injury than in previous years--or a combination of both factors.

Conclusion

The results of this study show an increasing prevalence over time of ACL injuries in a collegiate population. Sport and gender of the participant were not predictive of the presence of an ACL injury at the time of the preparticipation examination. Further research is needed to confirm whether these results reflect a growing trend in the number of collegiate athletes presenting for participation with a prior ACL injury.

References

(1.) Agel J, Arendt EA, Bershadsky B. Anterior cruciate ligament injury in National Collegiate Athletic Association basketball and soccer. Am J Sports Med. 2005;33(4): 524-531.

(2.) Arendt EA, Agel J, Dick R. Anterior cruciate ligament patterns among collegiate men and women. J Athl Train. 1999;34(2):86-92.

(3.) Mihata LCS, Beutler AI, Boden BP. Comparing the incidence of anterior cruciate ligament injury in collegiate lacrosse, soccer, and basketball players. Am J Sports Med. 2006;34(6):899-904.

(4.) Micheli LJ, Metzl JD, Di Canzio J, et al. Anterior cruciate reconstructive surgery in adolescent soccer and basketball player. Clin J Sport Med. 1999;9(3):138-141.

(5.) Arendt E, Dick R. Knee injury patterns among men and women in collegiate basketball and soccer. NCAA data and review of literature. Am J Sports Med. 1995;23(6):694-701.

(6.) Bjordal JM, Arnoy F, Hannestad B, et al. Epidemiology of anterior cruciate ligament injuries in soccer. Am J Sports Med. 1997;25(3):341-345.

(7.) Harmon KG, Dick R. The relationship of skill level to anterior cruciate ligament injury. Clin J Sport Med. 1998;8(4):260-265.

(8.) Powell JW, Barber-Foss KD. Sex-related injury patterns among selected high school sports. Am J Sports Med. 2000;28(3):385-391.

(9.) Prodromos CC, Han Y, Rogowski J, et al. A meta-analysis of the incidence of anterior cruciate ligament tears as a function of gender, sport, and a knee injury--reduction regimen. Arthroscopy. 2007;23(12):1320-1325.

(10.) Fernandez WG, Yard EE, Comstock RD. Epidemiology of lower extremity injuries among U.S. high school athletes. Acad Emerg Med. 2007;14:641-645.

(11.) Ingram JG, Fields SK, Yard EE, et al. Epidemiology of knee injuries among boys and girls in U.S. high school athletics. Am J Sports Med. 2008;36(6):1116-1122

(12.) Zillmer DA, Powell JW, Albright JP. Gender-specific injury patterns in high school varsity basketball. J Women's Health. 1992;1(1):69-76.

(13.) National Federation of State High School Associations. NFHS participation figures search. Available at: www.nfhs.org/custom/participation_figures. Accessed February 13, 2009.

(14.) Brophy RH, Barnes R, Rodeo SA, et al. Prevalence of musculoskeletal disorders at the NFL Combine--Trends from 1987 to 2000. Med Sci Sports Exerc. 2007;39(1):22-27.

(15.) Cheatham SA, Johnson DL. Current concepts in ACL injuries. Phys Sportsmed. 2010;38(3):61-68.

Mathew W. Lively, DO

Professor of Internal Medicine and Pediatrics

West Virginia University

Christopher C. Feathers, MD

Sports Medicine Fellow

Geisinger Health System
Table 1. ACL Injury by Sport and Gender

                Number      Number        Male          Female
Sport             of       with ACL
                Athletes    Injury    Total   #ACL    Total   #ACL

Football            745          28     745     28       0       0
Soccer              413          18     203      7     210      11
Baseball             256          6     256      6       0       0
Track                253          6     122      2     131       4
Basketball           157          3      82      0      75       3
Cheerleading         190          5      85      2     105       3
Swimming             234          3     137      0      97       3
Dance                 46          2       0      0      46       2
Wrestling            428          2     248      2       0       0
Cross Country         99          1      34      0      65       1
Rowing               174          1       0      0     174       1
Volleyball            65          1       0      0      65       1
Gymnastics            77          1       0      0      77       1
Rifle                 41          0      28      0      13       0
Tennis                81          0      26      0      55       0

Total               3079         77    1966     47    1113      30

Table 2. ACL Injury by Year

                Number of     Number of
Year of Exam   ACL Injuries   Athletes

1996                4            238
1997                4            259
1998                4            228
1999                7            269
2000                2            173
2001                5            254
2002                8            284
2003                7            224
2004                10           240
2005                4            241
2006                11           244
2007                6            190
2008                5            235

Total               77          3079
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