The Epidemiology of Lateral Ligament Complex Ankle Sprains in National Collegiate Athletic Association Sports

Transcription

1 The Epidemiology of Lateral Ligament Complex Ankle Sprains in National Collegiate Athletic Association Sports Karen G. Roos,* y PhD, MSPT, ATC, Zachary Y. Kerr, y PhD, MPH, Timothy C. Mauntel, z PhD, MA, ATC, Aristarque Djoko, y MS, Thomas P. Dompier, y PhD, ATC, and Erik A. Wikstrom, z PhD, ATC Investigation performed at the Datalys Center for Sports Injury Research and Prevention Inc, Indianapolis, Indiana, USA Background: Ankle sprains are a common injury in collegiate sports. Few studies have examined the epidemiology of individual ligament injuries, specifically the lateral ligament complex (LLC) of the ankle. Purpose: To describe the epidemiology, including the estimated yearly national incidence, of LLC sprains among National Collegiate Athletic Association (NCAA) athletes. Study Design: Descriptive epidemiology study. Methods: Injury surveillance data for 25 sports from the NCAA Injury Surveillance Program (NCAA-ISP) for the academic years to were used for analysis. All injuries included for analysis had a diagnosis of an LLC sprain. LLC sprain rates and rate ratios (RRs) with 95% CIs were calculated. From the sample, national estimates of the annual incidence of LLC sprains across the entire student-athlete body from these 25 sports were also calculated. Results: During the to academic years, 2429 LLC sprains were reported, for a rate of 4.95 per 10,000 athlete-exposures (AEs). LLC sprains comprised 7.3% of all reported collegiate sports injuries in the NCAA-ISP. Also, an estimated 16,022 LLC sprains occurred annually among the 25 sports. The sports with the highest LLC sprain rates were men s basketball (11.96/10,000 AEs) and women s basketball (9.50/10,000 AEs). Most LLC sprains occurred during practices (57.3%); however, the LLC sprain rate was higher in competitions than in practices (RR, 3.29; 95% CI, ). Also, 11.9% of LLC sprains were identified as recurrent injuries, with the largest proportions of recurrent LLC sprains being found within women s basketball (21.1%), women s outdoor track (21.1%), women s field hockey (20.0%), and men s basketball (19.1%). In 44.4% of LLC sprains, the athlete returned to play in less than 24 hours; in 3.6%, the athlete required more than 21 days before returning to play (including those who did not return to play at all). Conclusion: LLC sprains were the most commonly reported injury diagnosis among United States collegiate student-athletes. Continued examination of interventions that aim to reduce the incidence, severity, and recurrence of LLC sprains, specifically in women, is warranted. Keywords: ankle sprain; college; injury *Address correspondence to Karen G. Roos, PhD, MSPT, ATC, Datalys Center for Sports Injury Research and Prevention Inc, 401 West Michigan Street, Suite 500, Indianapolis, IN 46202, USA ( kroos@ datalyscenter.org). y Datalys Center for Sports Injury Research and Prevention Inc, Indianapolis, Indiana, USA. z University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. One or more of the authors has declared the following potential conflict of interest or source of funding: The Injury Surveillance Program was funded by the National Collegiate Athletic Association. K.G.R., Z.Y.K., A.D., and T.P.D. are employed by the Datalys Center for Sports Injury Research and Prevention Inc. The American Journal of Sports Medicine, Vol. 45, No. 1 DOI: / Ó 2016 The Author(s) Ankle ligament sprains are one of the most common injuries in collegiate athletics. 1,2,13,16 However, the majority of published research regarding these injuries investigated ankle sprains in general, without examining specific individual ligament structures, and the different functions that they serve. The lateral ligament complex (LLC) consists of the anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament. 37 These 3 ligaments work together to stabilize the lateral aspect of the ankle in concert with the dynamic stabilizers that cross over the ankle joint. 37 If lateral ankle stability is compromised, it may predispose an athlete to further injuries. 11,20 LLC sprains vary in their severity, ranging from overstretching and microtears of the ligaments (grade 1) to complete ligament ruptures (grade 3). 12 Immediate treatment 201

2 202 Roos et al The American Journal of Sports Medicine options for LLC sprains also vary and range from minimal modification of physical activity to surgical reconstruction of the LLC. 8 This range of outcomes may affect the reported incidence of LLC sprains, as historically, the sports epidemiological literature did not include injuries that restricted participation for less than 24 hours (otherwise known as non time loss [NTL] injuries). 19 There is currently limited information on the incidence of LLC sprains as a separate measure from ankle sprains in general and even less information on NTL LLC sprains in collegiate athletes. This study describes the epidemiology of LLC sprains in 25 National Collegiate Athletic Association (NCAA) sports during the to academic years. METHODS This study was approved by the NCAA Research Review Board. Deidentified injury surveillance data on collegiate ankle LLC sprains and sports exposures from the NCAA Injury Surveillance Program (NCAA-ISP) were used for analyses. The NCAA-ISP collects data prospectively and is managed by the Datalys Center for Sports Injury Research and Prevention, an independent, nonprofit research organization. The NCAA-ISP methodology during the to academic years has been previously described but is briefly summarized below. 19 Data Collection Data were collected from a convenience sample of NCAA varsity teams from 25 sports, although the number of programs providing data varied by sport and year. Certified athletic trainers (ATs) reported data from participating teams during all team-sanctioned practices and competitions including varsity-level practices, conditioning sessions, and competitions. Individual weight-lifting and conditioning sessions were excluded. These data included the number of athletes at each sanctioned team event as well as variables associated with each event (eg, location, season, conditions). Sports-related injury and adverse health event data (eg, heat illness, infection, general medical conditions) were collected as injuries occurred or were reported to the athletic training staff. Once an injury was identified, detailed information regarding the injury including, but not limited to, the body part affected, injury diagnosis, mechanism of injury, and activity at the time of injury was collected and reported to the electronic medical record (EMR). Individual ATs used their experience and expertise to assess these injury elements. All injuries reported to ATs and documented within their EMR were available for analysis. ATs had the ability to review and update the data as needed over the course of a season. Deidentified common data elements (CDEs) were extracted from the EMRs of participating ATs. All CDEs were stripped of any identifiers and encrypted prior to exporting to the central aggregate research database. As this CDE standard uses the existing documentation programs of the ATs, they did not have to separately enter injuries for surveillance purposes. Exported data passed through an automated verification process that conducted a series of range and consistency checks. Data were reviewed and flagged for invalid values. The AT and data quality assurance staff were notified and worked together to resolve the issue. Data that passed the verification process were then placed into the aggregate research dataset. Definitions A reportable injury was any injury that occurred as a result of participation in a team-sanctioned event and required attention from an AT or physician. Only injuries with a diagnosis of an LLC sprain of the ankle within the NCAA-ISP were included in this analysis. A reportable athleteexposure (AE) was defined as 1 student-athlete participating in 1 NCAA-sanctioned practice or competition in which he or she was exposed to the possibility of an athletic injury regardless of the time associated with that participation. Only athletes with playing time in a competition, including warm-up time, were included in competition exposures. LLC injuries were also categorized by the number of days lost to sports (ie, the date of injury subtracted from the date of return). NTL injuries were those resulting in participation restriction of less than 24 hours; all other injuries are referred to as time loss. A category for severe injuries included injuries resulting in participation restriction of over 3 weeks, the student-athlete choosing to prematurely end his or her season, or a medical professional having the student-athlete prematurely end his or her season. National Estimates To calculate the national estimates of the number of injuries and AEs, poststratification sample weights, based on the sport, division, and academic year, were applied to each reported injury and AE. Poststratification sample weights were calculated using the following formula: Number of ISP schools 1 ijk weight ijk 5 ; Number of sponsoring schools ijk where weight ijk is the weight for the ith sport of the jth division in the kth year. Weights were further adjusted to correct for underreporting. According to findings from Kucera et al, 21 which estimated that the NCAA-ISP captured 88.3% of all time-loss injury events that required medical care, weighted counts were scaled up by a factor of Statistical Analysis LLC sprain rates per 10,000 AEs and percentages were calculated, using injury counts and AEs. Percentage distributions were calculated for the amount of time lost to sports, total LLC sprains that were recurrent within each individual sport, and sex-comparable sports. Rate ratios (RRs) were calculated to compare rates of LLC injuries by event

3 AJSM Vol. 45, No. 1, 2017 Lateral Ligament Complex Ankle Sprains 203 TABLE 1 Incidence and Rates of LLC Sprains in 25 Sports a LLC Sprains, n Rate per 10,000 Athlete- Exposures (95% CI) b Competition vs Practice Rate Sport Competition Practice Overall Competition Practice Overall Ratio (95% CI) Men s football ( ) 4.04 ( ) 6.87 ( ) 8.19 ( ) d Men s wrestling ( ) 3.41 ( ) 3.72 ( ) 1.88 ( ) Women s volleyball ( ) 5.94 ( ) 6.92 ( ) 1.58 ( ) d Women s field hockey ( ) 2.93 ( ) 3.04 ( ) 1.15 ( ) Women s gymnastics ( ) 6.03 ( ) 6.19 ( ) 1.28 ( ) Men s ice hockey ( ) 0.58 ( ) 1.52 ( ) 7.62 ( ) d Women s ice hockey ( ) 0.47 ( ) 0.96 ( ) 4.96 ( ) d Men s soccer ( ) 4.96 ( ) 7.43 ( ) 3.30 ( ) d Women s soccer ( ) 4.61 ( ) 8.36 ( ) 4.36 ( ) d Men s basketball ( ) ( ) ( ) 1.62 ( ) d Women s basketball ( ) 7.06 ( ) 9.50 ( ) 2.48 ( ) d Men s lacrosse ( ) 3.31 ( ) 4.57 ( ) 3.29 ( ) d Women s lacrosse ( ) 4.01 ( ) 4.87 ( ) 2.13 ( ) d Men s baseball ( ) 1.19 ( ) 1.59 ( ) 1.90 ( ) Women s softball ( ) 1.74 ( ) 2.22 ( ) 1.72 ( ) Men s indoor track ( ) 1.14 ( ) 1.35 ( ) 3.03 ( ) d Women s indoor track ( ) 1.15 ( ) 1.18 ( ) 1.30 ( ) Men s outdoor track ( ) 1.15 ( ) 1.25 ( ) 1.58 ( ) Women s outdoor track ( ) 1.19 ( ) 1.88 ( ) 4.53 ( ) d Men s cross-country ( ) 3.32 ( ) 3.51 ( ) 1.67 ( ) Women s cross-country ( ) 2.31 ( ) 2.28 ( ) 0.87 ( ) Men s swimming and diving ( ) 0.08 ( ) 0.15 ( ) ( ) Women s swimming and diving ( ) 0.31 ( ) N/A Men s tennis ( ) 2.74 ( ) 3.78 ( ) 2.82 ( ) Women s tennis ( ) 3.90 ( ) 4.73 ( ) 1.94 ( ) Men s sports total c ( ) 3.19 ( ) 4.13 ( ) 2.44 ( ) d Women s sports total c ( ) 2.99 ( ) 4.36 ( ) 3.13 ( ) d Overall total ( ) 3.48 ( ) 4.95 ( ) 3.29 ( ) d a LLC, lateral ligament complex; N/A, not applicable. b An athlete-exposure was defined as 1 athlete participating in 1 National Collegiate Athletic Association sanctioned practice or competition. c Only includes sports in which both sexes participated (ie, soccer, basketball, ice hockey, lacrosse, baseball/softball, indoor track, outdoor track, cross-country, swimming and diving, tennis). d Statistically significant. type, season, time loss, and sex (for sex-comparable sports only). Standard large-sample Poisson assumptions were used for these count data to compute 95% CIs for all injury rates and RRs. All 95% CIs not containing 1.00 were considered statistically significant. Data were analyzed using SAS-Enterprise Guide software (version 4.3; SAS Institute Inc). RESULTS Overall Frequencies and Rates Overall, 2429 LLC sprains were reported in 25 NCAA sports from the to academic years, resulting in an LLC sprain overall rate of 4.95 per 10,000 AEs (Table 1). An LLC sprain was the most common injury diagnosis reported to the NCAA-ISP, comprising 7.3% of all injuries (Table 2). The sports in which LLC sprains contributed the largest proportions of injuries were men s basketball (15.0%), women s basketball (14.5%), women s volleyball (10.7%), and women s lacrosse (10.2%). In addition, an LLC sprain was the most common injury diagnosis in 12 NCAA sports and within the top 5 for an additional 9 NCAA sports. LLC sprains also comprised 73.9% of all reported ankle sprains. The sports with the highest rates of LLC sprains were men s basketball (11.96/10,000 AEs), women s basketball (9.50/10,000 AEs), and women s soccer (8.36/10,000 AEs). Most LLC sprains occurred during practices (57.3%). However, the LLC sprain rate was higher in competitions than in practices (RR, 3.29; 95% CI, ). In sex-comparable sports (ice hockey, soccer, basketball, lacrosse, baseball/softball, indoor track, outdoor track, crosscountry, swimming and diving, and tennis), LLC sprain rates did not differ overall (RR, 0.95; 95% CI, ) or in practices (RR, 1.07; 95% CI, ). However, the LLC sprain rate in competitions was lower in men than in women (RR, 0.83; 95% CI, ). When examining sports-specific sex differences, the only difference was found in basketball, in which men had a higher rate of LLC sprains than women overall (RR, 1.26; 95% CI, ), and in practices (RR, 1.49; 95% CI, ). The 2429 reported LLC sprains in the NCAA-ISP equates to a national estimate of 96,135 LLC sprains (or 16,022 per year) across the student-athlete population in the 25 NCAA sports over the 6 years of this study (Table 2). It is estimated that the majority of these LLC sprains occur in men s football

4 204 Roos et al The American Journal of Sports Medicine TABLE 2 Percentage of All Reported Injuries and National Estimates of Lateral Ligament Complex Sprains in 25 Sports National Estimates, n Sport Ranking Based on Most Reported Injury Within Sport % of All Reported Injuries Within Sport During Study Period Average Annual Estimate Men s football , Men s wrestling Women s volleyball Women s field hockey Women s gymnastics Men s ice hockey Women s ice hockey Men s soccer Women s soccer Men s basketball , Women s basketball Men s lacrosse Women s lacrosse Men s baseball Women s softball Men s indoor track Women s indoor track Men s outdoor track Women s outdoor track Men s cross-country Women s cross-country Men s swimming and diving Women s swimming and diving Men s tennis Women s tennis Overall total ,136 16,023 (n = 21,633), men s basketball (n = 14,358), women s basketball (n = 9147), women s soccer (n = 8947), and men s soccer (n = 7269). Injury Mechanism The most common injury mechanisms for LLC sprains overall were player contact (41.4%), noncontact (27.4%), and surface contact (22.2%) (Figure 1). Women s gymnastics had the highest proportion of LLC sprains due to surface contact (71.4%). All running sports, with the exception of men s outdoor track, had more than 50% of injuries caused by surface contact. Women s tennis also had a high percentage of injuries due to surface contact (59.1%). Across all sexcomparable sports, men had a larger proportion of injuries due to player contact than women (39.9% vs 32.7%, respectively; injury proportion ratio [IPR], 1.22; 95% CI, ). In contrast, women had a larger proportion of injuries due to surface contact than men (28.1% vs 20.1%, respectively; IPR, 1.40; 95% CI, ). Recurrence In total, 11.9% of LLC sprains were identified as recurrent injuries by the ATs who report the data (Figure 2). Across sex-comparable sports, the proportion of recurrent LLC sprains in men and women did not differ (14.4% vs 14.9%, respectively; IPR, 0.97; 95% CI, ). Women s basketball and women s outdoor track had the highest percentages of recurrent LLC sprains (21.1% each), followed by women s field hockey (20.0%) and men s basketball (19.1%). In contrast, men s and women s swimming and diving, women s cross-country, and women s indoor track did not report any recurrent LLC sprains. Participation Restriction Time Overall, 44.4% of LLC sprains were NTL injuries, and 3.6% were severe (Figure 3). Sports with the largest proportions of NTL LLC sprains included women s swimming and diving (80.0%, although only 5 LLC sprains were reported), men s indoor track (61.9%), women s ice hockey (57.1%), women s indoor track (55.6%), and men s ice hockey (51.6%). Sports with the largest proportions of severe injuries included women s swimming and diving (20.0%), women s gymnastics (14.3%), men s tennis (14.3%), men s ice hockey (12.9%), and women s outdoor track (10.5%). Sex differences were not found in the proportions of injuries that were NTL or severe, with the exception of soccer in which women had a larger proportion of severe LLC sprains than men (7.6% vs 2.1%, respectively; IPR, 3.60; 95% CI, ).

5 AJSM Vol. 45, No. 1, 2017 Lateral Ligament Complex Ankle Sprains 205 Men's Football (n=771) Men's Wrestling (n=39) Women's Volleyball (n=141) Women's Field Hockey (n=15) Women's Gymnastics (n=35) Men's Ice Hockey (n=62) Women's Ice Hockey (n=14) Men's Soccer (n=143) Women's Soccer (n=225) Men's Basketball (n=346) Women's Basketball (n=237) Men's Lacrosse (n=96) Women's Lacrosse (n=72) Men's Baseball (n=36) Women's Softball (n=47) Men's Indoor Track (n=21) Women's Indoor Track (n=18) Men's Outdoor Track (n=14) Women's Outdoor Track (n=19) Men's Cross Country (n=22) Women's Cross Country (n=13) Men's Swimming and Diving (n=2) Women's Swimming and Diving (n=5) Men's Tennis (n=14) Women's Tennis (n=22) Men's Sports Total (n=756) a Women's Sports Total (n=672) a Overall total (n=2429) 0% 20% 40% 60% 80% 100% Player contact Surface contact Other contact Non-contact Overuse Other/Unknown Figure 1. Distribution of the mechanism of injury of lateral ligament complex sprains in 25 sports: National Collegiate Athletic Association Injury Surveillance Program from academic years to a Only includes sports in which both sexes participated (ie, soccer, basketball, ice hockey, lacrosse, baseball/softball, indoor track, outdoor track, cross-country, swimming and diving, tennis). Men's Football (n=771) Men's Wrestling (n=39) Women's Volleyball (n=141) Women's Field Hockey (n=15) Women's Gymnastics (n=35) Men's Ice Hockey (n=62) Women's Ice Hockey (n=14) Men's Soccer (n=143) Women's Soccer (n=225) Men's Basketball (n=346) Women's Basketball (n=237) Men's Lacrosse (n=96) Women's Lacrosse (n=72) Men's Baseball (n=36) Women's Softball (n=47) Men's Indoor Track (n=21) Women's Indoor Track (n=18) Men's Outdoor Track (n=14) Women's Outdoor Track (n=19) Men's Cross Country (n=22) Women's Cross Country (n=13) Men's Swimming and Diving (n=2) Women's Swimming and Diving (n=5) Men's Tennis (n=14) Women's Tennis (n=22) Men's Sports Total (n=756) Women's Sports Total (n=672) a Overall total (n=2429) a 0.0% 0.0% 0.0% 0.0% 7.7% 5.1% 8.5% 6.5% 7.1% 5.6% 6.4% 4.8% 9.4% 11.4% 14.0% 12.9% 12.5% 14.3% 13.6% 14.3% 18.2% 14.4% 14.9% 11.9% 20.0% 19.1% 21.1% 21.1% 0% 5% 10% 15% 20% 25% % of lateral ligament complex sprains that are recurrent Figure 2. Lateral ligament complex (LLC) sprain recurrences as a percentage of the total LLC sprain incidence in 25 sports: National Collegiate Athletic Association Injury Surveillance Program from academic years to a Only includes sports in which both sexes participated (ie, soccer, basketball, ice hockey, lacrosse, baseball/softball, indoor track, outdoor track, cross-country, swimming and diving, tennis). DISCUSSION LLC sprains are the most common injury in United States collegiate athletes. Our data provide a greater understanding of the incidence and clinical burden of LLC sprains as well as their potential impact within the NCAA studentathlete population. Among the 25 NCAA sports examined, our study estimates that 16,022 LLC sprains are sustained by collegiate student-athletes each year. With 453,713 student-athletes participating in these 25 NCAA sports in the academic year, 28 this translates into at least 1 in 28 collegiate student-athletes sustaining an LLC sprain each academic year. The incidence of LLC sprains not only presents a burden to injured student-athletes and medical staff but also an economic burden. Medical costs due to ankle sprains have been reported to range from e87.44 to e per injury 18 (approximately US$95-$178). Verhagen et al 38 also estimated that it cost e (approximately US$483) to prevent 1 ankle sprain; however, when the prevention program was implemented among only those athletes with a history of ankle sprains, the cost decreased to e51.68 (approximately US$56). This indicates that the monetary cost of treating LLC sprains in collegiate student-athletes would be upwards of e2 million a year (approximately US$2.2 million), although in the collegiate setting, these costs are often mitigated by the presence of ATs and/or other health care providers who diagnose and manage such injuries at the onset of injury. Nevertheless,

6 206 Roos et al The American Journal of Sports Medicine Men's Football (n=771) Men's Wrestling (n=39) Women's Volleyball (n=141) Women's Field Hockey (n=15) Women's Gymnastics (n=35) Men's Ice Hockey (n=62) Women's Ice Hockey (n=14) Men's Soccer (n=143) Women's Soccer (n=225) Men's Basketball (n=346) Women's Basketball (n=237) Men's Lacrosse (n=96) Women's Lacrosse (n=72) Men's Baseball (n=36) Women's Softball (n=47) Men's Indoor Track (n=21) Women's Indoor Track (n=18) Men's Outdoor Track (n=14) Women's Outdoor Track Men's Cross Country (n=22) Women's Cross Country Men's Swimming and Diving Women's Swimming and Men's Tennis (n=14) Women's Tennis (n=22) Men's Sports Total (n=756) a Women's Sports Total (n=672) a Overall total (n=2429) 0% 20% 40% 60% 80% 100% <24 hours 1-6 days 7-21 days >21 days Unknown Figure 3. The distribution of time loss from sports of lateral ligament complex sprains in 25 sports: National Collegiate Athletic Association Injury Surveillance Program from academic years to a Only includes sports in which both sexes participated (ie, soccer, basketball, ice hockey, lacrosse, baseball/softball, indoor track, outdoor track, cross-country, swimming and diving, tennis). even with the presence of sports team medical staff, costs remain in terms of time devoted to patient care and rehabilitation and supplies required, such as tape, braces, and modalities. Our findings highlight the need for the continued development of interventions to reduce the incidence and severity of LLC sprains among collegiate student-athletes in order to decrease both the monetary and nonmonetary costs. Our study builds on previous college-level surveillance by utilizing more recent data as well as a more specific examination of LLC sprains. Previous research that used data from the NCAA-ISP during the to academic years estimated an overall ankle sprain rate (including LLC sprains and all other types of ankle sprains) of 8.3 per 1000 AEs (approximately 83/10,000 AEs) and a national estimate of 11,000 ankle sprains that occurred in the academic year across 15 collegiate sports. 16 These rates are notably higher than our current rate of LLC sprains of 4.95 per 10,000 AEs. However, caution must be taken when comparing this previous research to our current findings. First, our current study includes 25 sports, including men s and women s indoor track, outdoor track, cross-country, swimming and diving, and tennis, which were not examined in the previous study. While it may seem that additional sports would increase the rate, these sports had the lowest rates of LLC sprains. In fact, in this analysis, these 10 sports only contributed 6% of the LLC sprains, but contributed 26% of the AEs, which ultimately decreases our rates of LLC sprains. It should also be noted that the previous studies included all ankle sprain diagnoses, and our study was limited to LLC sprains, which will decrease the incidence of injuries in this study. Second, although most ankle sprains in our study and in previous research were found to be LLC sprains, 33 the previous findings only included injuries with a time loss of at least 24 hours. Therefore, previous research excluded LLC sprains that were NTL, whereas the current NCAA-ISP found that nearly half of reported LLC sprains were NTL. Last, the steady increase in the number of NCAA student-athletes since the previous study will also contribute to the larger national estimates. 28 Although the past decade has introduced a number of efficacious ankle sprain prevention programs, 10,30,35 there is little information regarding the population effects of such interventions. Further investigation is needed regarding the expanded implementation and effectiveness of these programs outside of highly constrained randomized controlled trials to determine their effectiveness, specifically considering the continued high incidence of ankle sprains, including LLC sprains. 24,25 Previous sports injury surveillance at the collegiate and high school levels has also found that basketball and soccer have the highest rates of ankle sprains. 16,22,33 Our study, which is specific to LLC sprain rates, found similar

7 AJSM Vol. 45, No. 1, 2017 Lateral Ligament Complex Ankle Sprains 207 findings but also found high rates in football, gymnastics, and volleyball. The high LLC sprain rates among these sports may be caused by the lower extremity agility needed to be a successful athlete in these sports. The largest injury rates observed in our study were seen among basketball athletes. This is likely because of the inherent demands of the sport. Basketball athletes commonly jump and land 35 to 46 times per game, which is up to 4 times greater than soccer or volleyball athletes. 23,26,29,31 Furthermore, basketball athletes change directions or activities every 2 to 3 seconds. 23,26 Changes of directions and activities require basketball athletes to quickly accelerate and decelerate. These accelerations commonly occur in the frontal plane, which may make basketball athletes more prone to LLC sprains. 5,6 It should also be noted that the most common injury mechanism for LLC sprains was player contact. As contact is an integral part of many of the sports included in this study, it is imperative to continue examining strategies to mitigate the risk of contact-related LLC injuries. This may be particularly true in competitions, where the LLC sprain rate exceeded that in practice. Approximately 1 in 8 LLC sprains were recurrent, which is similar to what has been found at the high school level among all ankle sprains. 33 At the high school level, recurrent ankle sprains also account for more than a quarter of all recurrent injuries. 34 However, previous investigations using medical records have reported much higher percentages of ankle sprains that were recurrent in high school football players (60%) 36 and adolescent soccer players (56%). 32 Medina McKeon et al 27 also reported that 21.4% of LLC sprains were recurrent in collegiate athletes across 13 sports. Similarly, an additional study estimated weighted recurrent ankle sprain percentages that were higher than the current findings in 11 different sports, ranging from 18% (windsurfing) to 75% (fencing). 4 Thus, the recurrencerelated estimates that we have reported may appear low, given the findings previously reported and the fact that a history of ankle sprains is a prominent risk factor for future ankle sprains. 7 However, these differences in recurrence are likely affected by the different sports and populations included in each study, as well as the study design, as the other mentioned studies did not use injury surveillance data. Continued surveillance of LLC sprains is needed to better estimate recurrence among LLC sprains. At the same time, compared to previous research, 9,15,27 we found a smaller proportion of LLC sprains that required over 3 weeks of participation restriction time. A study by Cross et al 9 reported that for LLC sprains, athletes required an average of 14.7 days (range, 3-40 days) to return to sport. However, it should be noted that Cross et al 9 did not include NTL injuries, which makes a direct comparison difficult. Medina McKeon et al 27 estimated that the median return-to-play time for new and recurrent LLC sprains were 3 days (interquartile range [IQR], same day to 7 days) and the next day (IQR, next day to 7 days), respectively. Medina McKeon et al 27 included NTL injuries, and their return-to-play times are consistent with the current findings. The inclusion of NTL injuries provides a more robust dataset that may provide insight into possible reasons for the development of residual symptoms. For example, inadequate and/or inappropriate treatment for acute LLC sprains is hypothesized to be a contributing factor in the development of chronic ankle instability (CAI). 27 CAI is a condition defined by recurrent ankle sprains, episodes of giving way, and the presence of residual symptoms (decreased self-reported function, sensorimotor dysfunction, ligamentous laxity, etc). 15 Hubbard and Hicks-Little 17 indicated that LLC healing takes between 6 and 12 weeks, while postural control remains impaired for at least 21 days after an LLC sprain. 14 Thus, returning approximately 80% of athletes to participation within 7 days and approximately 44% of LLC sprains in less than 24 hours may (1) fail to allow for adequate healing of the LLC tissues, (2) fail to provide adequate time to treat acute sensorimotor deficits, and (3) explain why residual symptoms are so common after an LLC sprain. 3 It should be noted that some LLC sprains may be misdiagnoses (eg, a peroneal strain) or LLC sprains with concurrent injuries. However, without direct visualization of the lateral structures, misdiagnoses will always be possible, and at least anecdotally, few imaging techniques are ordered to assess soft tissue damage after suspected LLC sprains. It is also possible that some of the NTL injuries may not be true ankle sprains (eg, a givingway episode); however, it is unlikely that a giving-way episode, with no recovery burden, would be diagnosed as an LLC sprain and entered into the EMR. Thus, we speculate that the observed NTL injuries are mild LLC sprains that were walked off despite having a recovery burden. As highlighted by Medina McKeon et al, 27 this treatment pattern (ie, immediate return to participation for NTL injuries or return to participation prior to known recovery timelines) is particularly curious when compared to the typical restriction time of 2 to 8 weeks for a mild to moderate medial collateral ligament sprain of the knee, which is a musculoskeletal injury typically treated nonoperatively. It is important to examine the association between participation restriction time, injury recurrence, and the development of CAI. The relationship between these 3 outcomes may be specifically important for female athletes. Although no sex differences were found across all sex-comparable sports combined, 4 of the 5 sports with the highest percentages of LLC sprain recurrence were women s sports (basketball, outdoor track, field hockey, and tennis). Because surveillance data such as in the NCAA- ISP do not examine specific individual risk factors alongside specific components of recovery and treatment, future etiological research is needed to better examine strategies to help ensure proper and timely return to participation. Areas of exploration may include examining whether sufficient time was provided to properly heal from the initial injury or differences in ligamentous stability after an LLC sprain. Limitations Our findings may not be generalizable to other settings, particularly those programs that did not provide data or are outside of the NCAA setting. For certain sports, such as swimming and diving, few LLC sprains were reported,

8 208 Roos et al The American Journal of Sports Medicine which consequently affected the ability to provide more indepth analyses of the epidemiology of LLC sprains within those sports. The assignment of injury diagnosis, mechanism of injury, and whether an LLC sprain was recurrent was at the discretion of the AT and may not have accounted for any LLC sprains that were sustained prior to the AT s working relationship with the student-athlete. As a result, estimates of LLC sprain recurrence may be conservative. The data also cannot account for injuries not reported to ATs. Our AE measure did not account for the individual variation in participation time among student-athletes; however, acquiring individual participation times for every student-athlete may have been too burdensome for ATs collecting data while also providing care. Last, national estimates were adjusted to account for potential injury underreporting. However, this weight adjustment was based off data from soccer that only considered injuries resulting in a time loss of at least 24 hours; the extent of underreporting among other sports and for NTL injuries may vary. CONCLUSION In our study of 25 NCAA sports during the to academic years, LLC sprains were the most reported type of injury, comprising 7.3% of all injuries reported in the NCAA-ISP. It was estimated that in these 25 sports, 16,022 LLC sprains are sustained annually. Nearly 1 in 2 LLC sprains were NTL, and approximately 1 in 8 were recurrent. Continued examination of interventions that aim to reduce the incidence, severity, and recurrence of LLC sprains, specifically in women, is warranted. ACKNOWLEDGMENT The authors thank all athletic trainers who participate in injury surveillance. REFERENCES 1. Agel J, Evans TA, Dick R, Putukian M, Marshall SW. Descriptive epidemiology of collegiate men s soccer injuries: National Collegiate Athletic Association Injury Surveillance System, through J Athl Train. 2007;42(2): Agel J, Palmieri-Smith RM, Dick R, Wojtys EM, Marshall SW. Descriptive epidemiology of collegiate women s volleyball injuries: National Collegiate Athletic Association Injury Surveillance System, through J Athl Train. 2007;42(2): Anandacoomarasamy A, Barnsley L. Long term outcomes of inversion ankle injuries. Br J Sports Med. 2005;39(3):e Attenborough AS, Hiller CE, Smith RM, Stuelcken M, Greene A, Sinclair PJ. Chronic ankle instability in sporting populations. Sports Med. 2014;44: Ben Abdelkrim N, Castagna C, Jabri I, Battikh T, El Fazaa S, El Ati J. Activity profile and physiological requirements of junior elite basketball players in relation to aerobic-anaerobic fitness. J Strength Cond Res. 2010;24: Ben Abdelkrim N, El Fazaa S, El Ati J. Time-motion analysis and physiological data of elite under-19-year-old basketball players during competition. Br J Sports Med. 2007;41: Beynnon BD, Vacek PM, Murphy D, Alosa D, Paller D. First-time inversion ankle ligament trauma the effects of sex, level of competition, and sport on the incidence of injury. Am J Sports Med. 2005;33: Cho BK, Kim YM, Shon HC, Park KJ, Cha JK, Ha YW. A ligament reattachment technique for high-demand athletes with chronic ankle instability. J Foot Ankle Surg. 2015;54: Cross KM, Worrell TW, Leslie JE, Van Veld KR. The relationship between self-reported and clinical measures and the number of days to return to sport following acute lateral ankle sprains. J Orthop Sports Phys Ther. 2002;32: Cumps E, Verhagen E, Meeusen R. Efficacy of a sports specific balance training programme on the incidence of ankle sprains in basketball. J Sports Sci Med. 2007;6: Denegar CR, Hertel J, Fonseca J. The effect of lateral ankle sprain on dorsiflexion range of motion, posterior talar glide, and joint laxity. J Orthop Sports Phys Ther. 2002;32: Dias LS. The lateral ankle sprain: an experimental study. J Trauma. 1979:19(4): Dick R, Ferrara M, Agel J, et al. Descriptive epidemiology of collegiate men s football injuries: National Collegiate Athletic Association Injury Surveillance System, through J Athl Train. 2007;42: Evans T, Hertel J, Sebastianelli W. Bilateral deficits in postural control following lateral ankle sprain. Foot Ankle Int. 2004;25: Gribble PA, Delahunt E, Bleakley C, et al. Selection criteria for patients with chronic ankle instability in controlled research: a position statement of the International Ankle Consortium. Br J Sports Med. 2013;43(8): Hootman JM, Dick R, Agel J. Epidemiology of collegiate injuries for 15 sports: summary and recommendations for injury prevention initiatives. J Athl Train. 2007;42: Hubbard TJ, Hicks-Little CA. Ankle ligament healing after an acute ankle sprain: an evidence-based approach. J Athl Train. 2008; 43: Janssen KW, Hendriks MR, van Mechelen W, Verhagen E. The cost effectiveness of measures to prevent recurrent ankle sprains: results of a 3-arm randomized controlled trial. Am J Sports Med. 2014;42(7): Kerr Z, Dompier T, Snook E, et al. National Collegiate Athletic Association Injury Surveillance System: review of methods for through data collection. J Athl Train. 2014;49: Kovaleski JE, Heitman RJ, Gurchiek LR, Hollis J, Liu W, Pearsall AW 4th. Joint stability characteristics of the ankle complex in female athletes with histories of lateral ankle sprain, part II: clinical experience using arthrometric measurement. J Athl Train. 2014;49: Kucera K, Marshall S, Bell D, DiStefano M, Goerger C, Oyama S. Validity of soccer injury data from the National Collegiate Athletic Association s Injury Surveillance System. J Athl Train. 2011;46: Lam KC, Snyder Valier AR, Valovich McLeod TC. Injury and treatment characteristics of sport-specific injuries sustained in interscholastic athletics: a report from the athletic training practice-based research network. Sports Health. 2015;7: Matthew D, Delextrat A. Heart rate, blood lactate concentration, and time-motion analysis of female basketball players during competition. J Sports Sci. 2009;27: McGuine TA, Brooks A, Hetzel S. The effect of lace-up ankle braces on injury rates in high school basketball players. Am J Sports Med. 2011;39: McGuine TA, Hetzel S, Wilson J, Brooks A. The effect of lace-up ankle braces on injury rates in high school football players. Am J Sports Med. 2012;40: McInnes SE, Carlson JS, Jones CJ, McKenna MJ. The physiological load imposed on basketball players during competition. J Sports Sci. 1995;13: Medina McKeon JM, Bush HM, Reed A, Whittington A, Uhl TL, McKeon PO. Return-to-play probabilities following new versus recurrent ankle sprains in high school athletes. JSciMedSport. 2014;17: National Collegiate Athletic Association. Student-athletes. Available at: Accessed November 2, 2015.

9 AJSM Vol. 45, No. 1, 2017 Lateral Ligament Complex Ankle Sprains Nedelec M, McCall A, Carling C, Legall F, Berthoin S, Dupont G. The influence of soccer playing actions on the recovery kinetics after a soccer match. J Strength Cond Res. 2014;28: Riva D, Bianchi R, Rocca F, Mamo C. Proprioceptive training and injury prevention in a professional men s basketball team: a sixyear prospective study. J Strength Cond Res. 2016;30(2): Sheppard JM, Gabbett TJ, Stanganelli LC. An analysis of playing positions in elite men s volleyball: considerations for competition demands and physiologic characteristics. J Strength Cond Res. 2009;23: Söderman K, Adolphson J, Lorentzon R, Alfredson H. Injuries in adolescent female players in European football: a prospective study over one outdoor soccer season. Scand J Med Sci Sports. 2001;11: Swenson DM, Collins CL, Fields SK, Comstock RD. Epidemiology of US high school sports-related ligamentous ankle injuries, 2005/ /11. Clin J Sport Med. 2013;23: Swenson DM, Yard EE, Fields SK, Comstock RD. Patterns of recurrent injuries among US high school athletes, Am J Sports Med. 2009;37: Taylor JB, Ford KR, Nguyen AD, Terry LN, Hegedus EJ. Prevention of lower extremity injuries in basketball: a systematic review and metaanalysis. Sports Health. 2015;7(5): Tyler TF, McHugh MP, Mirabella MR, Mullaney MJ, Nicholas SJ. Risk factors for noncontact ankle sprains in high school football players: the role of previous ankle sprains and body mass index. Am J Sports Med. 2006;34: van den Bekerom MP, Kerkhoffs GM, McCollum GA, Calder JD, van Dijk CN. Management of acute lateral ankle ligament injury in the athlete. Knee Surg Sports Traumatol Arthrosc. 2013;21: Verhagen E, Van Tulder M, van der Beek AJ, Bouter L, Van Mechelen W. An economic evaluation of a proprioceptive balance board training programme for the prevention of ankle sprains in volleyball. Br J Sports Med. 2005;39: For reprints and permission queries, please visit SAGE s Web site at