Poster 250: Increased Risk of Anterior Cruciate Ligament Injuries for Female but Not Male Soccer Players on Artificial Turf Versus Natural Grass: A Systematic Review and Meta-Analysis

Abstract

Objectives:

Both natural grass (NG) and artificial turf (AT) are popular playing surfaces for soccer. Biomechanical studies have found increased frictional forces on artificial turf that may lead to anterior cruciate ligament (ACL) injury. Few studies have examined the differences between ACL injury risk in male and female soccer athletes playing on AT versus NG. Given the higher risk for female ACL injury in sports, and soccer in particular, it is important to define whether AT may compound this injury risk. The purpose of this investigation was to systematically review the literature for studies comparing ACL injury risk on AT versus NG in soccer, and to specifically determine if there were differences in injury risk in males versus females when considering the playing surface.

Methods:

A systematic review was pre-registered on PROSPERO and performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, SCOPUS, and Cochrane Central Register of Controlled Trials were searched for Level I-III studies that compared the incidence of ACL injuries on AT versus NG in soccer players. Data recorded included study demographics, 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. Incidence rate ratios (IRRs) were calculated by dividing the incidence of ACL injury on AT over NG, where IRRs < 1 indicate a lower incidence of ACL injuries on AT compared to NG, and IRRs > 1 signify a higher incidence of ACL injuries on AT compared to NG. A Mantel-Haenszel random effects model was used for meta-analyses of IRRs, and forest plots were generated for the pooled IRR for ACL injuries in game and training settings. Additionally, sub-analyses based on athlete sex were conducted for IRRs of ACL injuries in games. A p-value of less than 0.05 was set as significant.

Results:

Seven articles (four male, two female, one male and female cohort; mean MINORS score 20 + 0.8) were included and analyzed (Figure 1). There were two studies that investigated ACL injuries in a female only cohort, four studies that used a male only cohort, and one study that included both males and females (Table 1). Levels of play included professional (n = 3 studies), college (n = 3 studies), and youth (n = 1 studies). Pooled ACL injury IRRs demonstrated no significant differences in overall ACL injury risk when playing soccer on AT compared to NG (IRR = 0.61 [0.23-1.60], p = 0.31; Figure 2). A significantly increased risk of ACL injury in games played on AT compared to NG was detected for females (IRR = 1.18 [1.05-1.31], p = 0.004) but not for males (IRR = 1.18 [0.97- 1.42], p = 0.09; Figure 3). Subgroup analyses showed no significant differences in injury risk for games (IRR = 1.07 [0.97- 1.18], p = 0.20) or practices (IRR = 0.21 [0.04-1.23], p = 0.09; Figure 2). A total of 3,023 ACL injuries occurred on NG and 526 ACL injuries happened on AT, and the majority of soccer exposures in each study was on NG (range: 50.33% - 85.74%).

Conclusions:

.This investigation found that females had a significantly higher risk of ACL injury when playing games on AT versus NG, whereas no significant difference was seen in males. No differences were found for the combined male/female population nor soccer games or training sessions played on AT compared to NG.

Figure 1.

Flow diagram summarizing the literature search, screening, and review.

Figure 2.

Forest plot of the pooled incidence rate ratios {IRRs) for anterior cruciate ligament (ACL) injury on artificial turf (AT) versus natural grass (NG) in soccer players with sub-analysis by exposure setting (game versus training). CI - Confidence Interval

Figure 3.

Forest plot of the sub-analysis based on sex (male or female) of pooled incidence rate ratios (IRRs) for anterior cruciate ligament (ACL) injury in soccer games played on artificial turf (AT) versus natural pass (NG). CI - Confidence Interval

Table 1.

Summary of study demographics for included articles. MINORS - Methodological Index for Non-Randomized Studies; BJSM - British Journal of Sports Medicine, AJSM - American Journal of Sports Medicine; KSSTA - Knee Surgery, Sports Traumatology, Arthroscopy; OJSM - Orthopaedic Journal of Sports Medicine; SJMSS -Scandinavian Journal of Medicine & Science in Sports; NS - Not Specified