Epidemiology of Anterior Cruciate Ligament Injury on Natural Grass Versus Artificial Turf in Soccer: 10-Year Data From the National Collegiate Athletic Association Injury Surveillance System

Examining the Prevalence of Anterior Cruciate Ligament Injuries on Artificial Turf Surfaces Compared to Natural Grass Surfaces in Athletes: A Scoping Review

The anterior cruciate ligament (ACL) is commonly injured in sports such as American football and soccer. It is currently unknown if ACL injuries are more prevalent on natural grass or artificial turf fields. The purpose of this scoping review is to analyze research studies evaluating the effect of the playing surface on the prevalence of ACL injuries. We hypothesize that athletes face a greater risk of suffering ACL injuries while playing on artificial turf compared to natural grass. Our team conducted a comprehensive literature review by screening three databases (PubMed, Embase, and Cochrane) that comprised a wide range of peer-reviewed articles on ACL injuries suffered on natural grass and artificial turf surfaces. Inclusion criteria consisted of epidemiological and cohort studies published after 1990 that were written in English and focused on athletes ranging in skill level from youth to professional. Exclusion criteria consisted of biomechanical studies, review articles, and papers that focused on injuries of structures other than the ACL. Bias was assessed with the MINORS criteria. Results were presented by injury rates, calculated ratios, and confidence intervals. The final analysis included nine papers published in peer-reviewed journals. Three of nine papers found that ACL injuries are more likely to occur on artificial turf than on natural grass. Three papers found that there is no difference in the prevalence of ACL injuries between surfaces and one paper stated that ACL injuries are more likely on natural grass than artificial turf. Two papers did not report confidence intervals for ratios comparing injury rates between playing surfaces. There is no consensus in the current literature regarding the prevalence of ACL injuries on artificial turf versus natural grass surfaces. The primary limitation of this study was that the papers used a variety of methods to compare rates of ACL injuries on artificial and natural surfaces, making comparisons between the nine papers difficult.

Does playing surface affect the risk of anterior cruciate ligament injuries in the National Football League? A look at the 2017 - 2021 NFL seasons

BACKGROUND

Anterior cruciate ligament (ACL) injuries are devastating injuries for athletes. Prior studies have shown increased ACL injury rates on non-natural surfaces versus natural grass in several sports. The purpose of this study is to calculate the prevalence of ACL injuries in the NFL on natural versus non-natural surfaces to determine if there is a significant increase on non-natural surfaces.

METHODS

Accessing publicly available data for NFL seasons beginning with the 2017-2018 season through 2021-2022 seasons, all ACL injuries with publicly available data concerning timing and playing surface were recorded and categorized according to playing surface. Practice injuries or those without an identifiable playing surface were excluded. Incidence rates, defined as ACL ruptures per game, were calculated. ACL injuries were recorded for each playing surface, as well as the combined category of non-natural grass surface. Odds ratio was calculated to compare the risk of ACL rupture on non-natural surfaces vs natural grass.

RESULTS

During the 2017-2021 NFL seasons, 173 ACL ruptures were identified with known surfaces. Injury rate for non-natural surfaces was 0.134 compared to 0.097 for grass. Injury rate ratio for non-natural vs natural grass surfaces was 1.211, a 21.1% increased risk of ACL injury in the NFL on non-natural surfaces vs natural grass. OR for non-natural surfaces 1.239 (95% CI 0.900-1.704). Based on these findings there is a trend toward increased risk of ACL injury on non natural grass surfaces, however this did not reach statistical significance.

CONCLUSION

Numerous published studies show trends toward increasing rates of ACL injuries on non-natural playing surfaces vs natural grass. Based on our findings the difference is not statistically significant, however it does trend toward increased risk of ACL injury with non-natural surfaces. Further studies should be performed with larger sample sizes in order to further determine the risk of non-natural surfaces.

Validity of Research Based on Publicly Obtained Data in Sports Medicine: A Quantitative Assessment of Concussions in the National Football League

CONTEXT

Numerous researchers have leveraged publicly available internet sources to publish clinical research concerning incidence and recovery from injuries in National Football League (NFL) players.

OBJECTIVE

This study aims to (1) provide a comprehensive systematic review of all publicly obtained data studies (PODS) regarding concussions in NFL athletes and (2) quantify the percentage of injuries identified by these studies in comparison with published concussion data from the NFL injury database.

STUDY SELECTION

A systematic review was conducted in accordance with PRISMA guidelines to identify all published studies utilizing publicly obtained data regarding concussions in NFL athletes.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Manuscript details, factors related to the athletes of interest (eg, study period, positions included), and results (eg, concussion rate, number of total concussions, return-to-play data) were extracted independently by 2 authors. Results were compared with incident concussions reported from 2015 to 2019 by each medical staff member to the NFL database linked to the League's electronic health record (EHR).

RESULTS

A total of 20 concussion-focused manuscripts based on PODS were identified from 2014 to 2020. PODS captured between 20% and 90% of concussions (mean, 70%) reported by medical staff to the injury database. PODS reported that 55% of concussions occurred on offensive plays, 45% on defensive plays and <1% occurred during special teams plays, compared with 44%, 37%, and 18%, respectively, as indicated by published data from the NFL injury database. When analyzed by position groups, running backs and quarterbacks comprised the most over-represented positions concussed in PODS, while offensive linemen, defensive backs, and linebackers comprised the most under-represented positions.

CONCLUSION

PODS captured approximately 70% of concussions reported by NFL medical staff to the NFL injury database. There is heterogeneity in the degree to which PODS were able to identify concussions, with a bias toward concussions among players at higher profile positions.

Loading mechanisms of the anterior cruciate ligament

This review identifies the three-dimensional knee loads that have the highest risk of injuring the anterior cruciate ligament (ACL) in the athlete. It is the combination of the muscular resistance to a large knee flexion moment, an external reaction force generating knee compression, an internal tibial torque, and a knee abduction moment during a single-leg athletic manoeuvre such as landing from a jump, abruptly changing direction, or rapidly decelerating that results in the greatest ACL loads. While there is consensus that an anterior tibial shear force is the primary ACL loading mechanism, controversy exists regarding the secondary order of importance of transverse-plane and frontal-plane loading in ACL injury scenarios. Large knee compression forces combined with a posteriorly and inferiorly sloped tibial plateau, especially the lateral plateau-an important ACL injury risk factor-causes anterior tibial translation and internal tibial rotation, which increases ACL loading. Furthermore, while the ACL can fail under a single supramaximal loading cycle, recent evidence shows that it can also fail following repeated submaximal loading cycles due to microdamage accumulating in the ligament with each cycle. This challenges the existing dogma that non-contact ACL injuries are predominantly due to a single manoeuvre that catastrophically overloads the ACL.

Increased Risk of ACL Injury for Female but Not Male Soccer Players on Artificial Turf Versus Natural Grass: A Systematic Review and Meta-Analysis

Background:

Both natural grass (NG) and artificial turf (AT) are popular playing surfaces for soccer. Biomechanical studies have found increased frictional forces on AT that may lead to anterior cruciate ligament (ACL) injury. The increased risk of ACL injury during soccer in female participants may amplify this effect.

Purpose:

To systematically review the literature for studies comparing ACL injury risk in soccer players on AT versus NG and to specifically determine whether there were differences in injury risk in male versus female players when considering the playing surface.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

A systematic review was performed using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Three databases were searched for studies with evidence level 1 to 3 that compared the incidence of ACL injuries on AT versus NG in soccer players. Data recorded included study characteristics, sex, competition level, exposure setting (games or practices), turf type, and ACL injury information. Study methodological quality was analyzed using the methodological index for non-randomized studies (MINORS) score, and incidence rate ratios (IRRs) were calculated.

Results:

Included were 7 articles (3 studying professional soccer, 3 collegiate soccer, 1 youth-level soccer; 4 male cohorts, 2 female cohorts, and 1 male and female cohort; mean MINORS score, 20 ± 0.8). Pooled ACL injury IRRs demonstrated no significant differences in overall ACL injury risk when playing soccer on AT compared with NG (IRR = 0.57 [95% CI, 0.21-1.53]; P = .31). A significantly increased risk of ACL injury in games played on AT compared with NG was detected for female (IRR = 1.18 [95% CI, 1.05-1.31]; P = .004) but not for male players (IRR = 1.18 [95% CI, 0.97-1.42]; P = .09). Subgroup analyses showed no significant differences in injury risk for games (IRR = 1.07 [95% CI, 0.97-1.18]; P = .20) or practices (IRR = 0.21 [95% CI, 0.04-1.23]; P = .09).

Conclusion:

Findings indicated that female soccer players had a significantly higher risk of ACL injury when playing games on AT versus NG, whereas no significant difference was seen in male players. No differences were found for the combined male/female cohort or for soccer games or training sessions played on AT compared with NG.

Epidemiological Comparison of ACL Injuries on Different Playing Surfaces in High School Football and Soccer

Background:

Anterior cruciate ligament (ACL) injuries are among the most common serious injuries to athletes in the United States. Among high school sports, the highest rates of ACL injury occur in soccer and football.

Purpose:

To compare ACL injuries on artificial turf and natural grass using a nationally representative sample of high school athletes participating in football and boys’ and girls’ soccer.

Study Design:

Descriptive epidemiology study.

Methods:

ACL injuries among high school athletes participating in football and soccer were obtained from the High School Reporting Information Online surveillance system during the 2007-08 through 2018-19 school years. National estimates and injury proportion ratios (IPRs) with 95% CIs were calculated for ACL injuries that occurred on artificial turf versus natural grass.

Results:

A total of 1039 ACL injuries were reported, which represented an estimated 389,320 (95% CI, 358,010-420,630) injuries nationally. There were 74,620 estimated football-related ACL injuries on artificial turf and 122,654 on natural grass. Likewise, 71,877 of the estimated soccer-related ACL injuries occurred on artificial turf and 104,028 on natural grass. A contact-injury mechanism accounted for 50.2% of football-related ACL injuries on artificial turf and 60.8% on natural grass. For soccer-related ACL injuries, a noncontact mechanism predominated on artificial turf (61.5%) and natural grass (66.4%). Among all injuries, ACL injuries were more likely to occur on artificial turf than natural grass in both football (IPR, 1.23 [95% CI, 1.03-1.47]) and girls’ soccer (IPR, 1.53 [95% CI, 1.08-2.16]); however, no significant association was found in boys’ soccer (IPR, 1.65 [95% CI, 0.99-2.75]). Among lower extremity injuries, ACL injuries were more likely to occur on artificial turf than natural grass in both boys’ soccer (IPR, 1.72 [95% CI, 1.03-2.85]) and girls’ soccer (IPR, 1.61 [95% CI, 1.14-2.26]); however, the association was not significant in football (IPR, 1.17 [95% CI, 0.98-1.39]).

Conclusion:

ACL injuries were more likely to occur (ie, had larger IPRs) on artificial turf than natural grass; however, this relationship was not statistically significant for all sports.