The effect of playing surface on the incidence of ACL injuries in National Collegiate Athletic Association American Football

Prevalence of Concomitant Injuries by Sport in Pediatric Patients With ACL Rupture

Background

Although the risk of concomitant injury with anterior cruciate ligament (ACL) tears as a function of specific sports participation has been studied in adults, the topic has not been examined in pediatric and adolescent patients.

Purpose/Hypothesis

The purpose of the study was to determine if certain sports were associated with a higher risk of concomitant injuries in the setting of an ACL tear. It was hypothesized that the risk of concomitant injuries with ACL tears will differ by type of sport participation in the pediatric population.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Patients ≤18 years old from 2 tertiary children's hospitals who had undergone primary ACL reconstruction between 2006 and 2018 were included. Sport at the time of injury, demographic factors, and injury pattern (medial meniscal [MM] tears, lateral meniscal [LM] tears, posterior cruciate ligament [PCL] tears, medial collateral ligament [MCL] tears, lateral collateral ligament [LCL] tears, and any concomitant injury) were identified.

Results

A total of 855 patients with a mean age of 15.5 ± 1.7 years (range, 7-22 years) met the inclusion criteria. Of the included patients, 353 (41.3%) had an isolated ACL tear. A concomitant MM tear was identified in 27.6% of patients, LM tear in 42.9%, PCL injury in 0.4%, MCL injury in 3.0%, and LCL injury in 0.5%. There was no difference in the likelihood of concomitant MM injuries by sex (29.3% for male patients vs 26% for female patients; P = .31) or by sex within basketball (29.3% for male patients vs 25.6% for female patients; P = .96) or soccer (32.3% vs 26.3%; P = .06). Boys had higher proportions of LM injuries overall (51.7% for male patients vs 34.6% for female patients; P < .001) but not within the basketball subgroup (50.5% vs 40.0%; P = .86) or the soccer subgroup (59.7% vs 40.0%; P = .19). No statistically significant associations were found between patient age and specific ACL concomitant injury patterns. When stratifying by body mass index, it was found overweight and obese individuals constituted a greater proportion of LM (49.6% vs 39.1%; P = .01) but not MM (29.4% vs 25.5%; P = .28) injuries when compared to normal-weight patients. Using basketball as the comparison group, soccer and football injuries were 18% more likely to result in any concomitant injury, including concomitant MM, LM, PCL, MCL, and LCL injuries.

Conclusion

In the pediatric population, soccer and football players were more likely to present with a concomitant injury in addition to ACL injury relative to basketball players. This study aids in understanding sport-associated ACL injury patterns and can help physicians with patient counseling and injury prevention.

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.

Anterior Cruciate Ligament Injury Prevention and Rehabilitation

At all levels of American football, knee injuries are common, with injuries to the anterior cruciate ligament (ACL) making up a significant proportion. Historically, ACL injuries were career-altering for professional players, but innovative techniques in surgery and rehabilitation have returned many to the field. While there is a consensus on surgical techniques for ACL reconstruction, significant discrepancies remain on injury prevention and rehabilitation programs. This review article describes the burden of ACL injury on players in the National Football League, best practices in injury prevention and rehabilitation, and evidence-based recommendations for preparing injured athletes to return to play.

Comparison of side-cutting maneuvers versus low impact baseball swing on knee ligament loading in adolescent populations

BACKGROUND

High impact sports are associated with an increased incidence rate for knee ligament injuries, specifically pertaining to the anterior cruciate ligament and medial collateral ligament. What is less clear is (i) the extent to which high impact activities preferentially load the anterior cruciate ligament versus the medial collateral ligament, and (ii) whether both ligaments experience similar stretch ratios during high loading scenarios. Therefore, the goal of this project was to assess how different loading conditions experienced through more at-risk sporting maneuvers influence the relative displacements of the anterior cruciate ligament and medial collateral ligament. The focus of the study was on adolescent patients - a group that has largely been overlooked when studying knee ligament biomechanics.

METHODS

Through kinetic knee data obtained through motion capture experimentation, two different loading conditions (high vs low impact) were applied to 22 specimen-specific adolescent finite element knee models to investigate the biomechanical impact various sporting maneuvers place on the knee ligaments.

FINDINGS

The high impact side cutting maneuver resulted in 102% and 47% increases in ligament displacement compared to the low impact baseball swing (p < 0.05) for both the anterior cruciate ligament and medial collateral ligament.

INTERPRETATION

Quantifying biomechanical risks that sporting activities place on adolescent subjects provides physicians with insight into knee ligament vulnerability. More specifically, knowing the risks that various sports place on ligaments helps guide the selection of sports for at-risk patients (especially those who have undergone knee ligament surgery).

Lower Extremity Injury Rates on Artificial Turf Versus Natural Grass Playing Surfaces: A Systematic Review

BACKGROUND

No study has provided a comprehensive systematic review of sports injuries on artificial turf versus natural grass.

PURPOSE

To comprehensively examine the risk of overall injuries and multiple types of lower extremity injuries across all sports, all levels of competition, and on both old-generation and new-generation artificial turf.

STUDY DESIGN

Systematic review; Level of evidence, 3.

METHODS

A systematic review of the English-language literature was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. All included articles compared overall injury rates or lower extremity (hip, knee, or foot and ankle) injury rates on artificial turf and natural grass. All sports, levels of competition, and turf types were included. Studies were excluded if they did not include overall injury rates or lower extremity injury rates. Because of the heterogeneity of the included studies, no attempt was made to aggregate risk ratios to conduct a quantitative meta-analysis.

RESULTS

A total of 53 articles published between 1972 and 2020 were identified for study inclusion. Most studies on new-generation turf (13/18 articles) found similar overall injury rates between playing surfaces. When individual anatomic injury locations were analyzed, the greatest proportion of articles reported a higher foot and ankle injury rate on artificial turf compared with natural grass, both with old-generation (3/4 articles) and new-generation (9/19 articles) turf. Similar knee and hip injury rates were reported between playing surfaces for soccer athletes on new-generation turf, but football players, particularly those at high levels of competition, were more likely to sustain a knee injury on artificial turf than on natural grass.

CONCLUSION

The available body of literature suggests a higher rate of foot and ankle injuries on artificial turf, both old-generation and new-generation turf, compared with natural grass. High-quality studies also suggest that the rates of knee injuries and hip injuries are similar between playing surfaces, although elite-level football athletes may be more predisposed to knee injuries on artificial turf compared with natural grass. Only a few articles in the literature reported a higher overall injury rate on natural grass compared with artificial turf, and all of these studies received financial support from the artificial turf industry.

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.

Unilateral versus Bilateral Landing after Spike Jumps in Male and Female Volleyball: A Systematic Review

Background: The spike is a key action in volleyball, and the landing technique and its asymmetries are commonly associated with an increased risk of injury. Objectives: The aim of this systematic review was to assess how male and female volleyball players land (i.e., unilaterally, or bilaterally) after spike jumps in matches and analytical settings (field or laboratory). Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines were followed, with eligibility criteria defined according to participants, interventions, comparators, study design (PICOS): (p) healthy indoor volleyball players of any sex, age group, or competitive level; (i) exposure to landing after spike actions during official matches AND/OR simulated 6 vs. 6 games AND/OR analytical training conditions AND/OR laboratorial experiments; (c) not mandatory; (o) data on landing mechanics after spike actions, including reporting of whether the landing was unilateral or bilateral; (s) no restrictions imposed on study design. Searches were performed in seven electronic databases (Cochrane Library, EBSCO, PubMed, Scielo, Scopus, SPORTDiscus, and Web of Science) on 23 April 2021. Results: Automated searches provided 420 results. Removal of 119 duplicates resulted in 301 records being screened for titles and abstracts. A total of 25 studies were eligible for full-text analysis. Of these, eight studies were deemed eligible for inclusion in the review. Studies showed that (i) attackers landed asymmetrically 68% of the times (61% left leg, 7% right leg); (ii) bilateral asymmetries were observed for the hip, knee, and ankle joints; (iii) bilateral asymmetries were observed even when players were instructed to land evenly on two feet; (iv) landing contact of the leg opposite to the hitting arm preceded the contact of the homolateral leg. One match analysis study showed that men landed more often on the left (31.5%) or right foot (8.5%) than women (23.7% and 1.6%). Conclusions: Studies analyzing spike landing showed a prevalence of unilateral landings (mostly the left leg first, for right-handed players) in men and women but more prevalently in men. Registration INPLASY202140104, DOI: 10.37766/inplasy2021.4.0104.

Force-limiting and the mechanical response of natural turfgrass used in the National Football League: A step toward the elimination of differential lower limb injury risk on synthetic turf

Lower limb injury rate in the National Football League (NFL) is greater on synthetic turf than on natural turfgrass. Foot loading in potentially injurious situations can be mitigated by damage to natural turfgrass that limits the peak load by allowing relative motion between the foot and the ground. Synthetic turf surfaces do not typically sustain such damage and thus lack such a load-limiting mechanism. To guide innovation in synthetic turf design, this paper reports 1) the peak loads of natural turfgrass when loaded by a cleated footform and 2) corridors that define the load-displacement response. Kentucky bluegrass [Poa pratensis, L.] and two cultivars of hybrid bermudagrass [Cynodon dactylon (L.) Pers × C. transvaalensis Burtt Davy] were tested with two cleat patterns in three loading modes (anterior-posterior or AP translation, medial-lateral or ML translation, and forefoot external rotation) at two power levels (full-power, which generated potentially injurious loads, and reduced-power, which generated horizontal forces similar to non-injurious ground reaction forces applied by an elite athlete during play). All tests generated peak force<4.95 kN and torque<173 Nm, which is in a loading regime that would be expected to mitigate injury risk. In full-power tests, bermudagrass withstood significantly (p < 0.05) greater peak loads than Kentucky bluegrass: (3.86 ± 0.45 kN vs. 2.66 ± 0.23 kN in AP, 3.25 ± 0.45 kN vs. 2.49 ± 0.36 kN in ML, and 144.8 ± 12.0 Nm vs. 126.3 ± 6.1 Nm in rotation). Corridors are reported that describe the load-displacement response aggregated across all surfaces tested.

Athletic Play Surfaces and Injury Risk

ABSTRACT

Advancements in technology and the economic desires to maximize use of athletic playing surfaces have led to the development of various playing surfaces across the spectrum of sports. Each of these surfaces possesses specific safety profiles which are sport and population specific. Despite the growing medical literature on outdoor playing surfaces, inconsistent data exist on both orthopedic injuries and general medical concerns, such as surface component exposure toxicity and infection risk. Unfortunately, there is a paucity of data regarding various indoor playing surfaces and their effects on injury risk; this is an area ripe for further medical investigation. Understanding the differences in various play surfaces and their associated injury and health concerns is crucial for all medical staff providing care to athletes across the spectrum of skill and competition.

Effects of overground surfaces on running kinematics and kinetics in habitual non-rearfoot strikers

This study aimed to investigate the effects of different overground surfaces on running biomechanics of non-rearfoot strikers. Thirty-one male habitual non-rearfoot strikers were required to run at 3.3 ± 0.2 m/s on a customized runway with artificial grass, concrete, or synthetic rubber surfaces in a random order. Vertical loading rates, three-dimensional ground reaction forces (GRFs), and lower-limb joint angles and moments were compared among surfaces. Regarding kinematics, significances were only detected in maximum knee flexion angle, with greater values when running on artificial grass compared to synthetic rubber or concrete. Regarding kinetics, changes were demonstrated in GRF peaks and lower-limb joint moments. GRF peaks were significantly greater when running on synthetic rubber or artificial grass compared to concrete; lower-limb joint moments were significantly lower when running on synthetic rubber compared to concrete; these changes were inconsistent when running on artificial grass compared to concrete. Significant differences were demonstrated in running kinetics when habitual non-rearfoot strikers ran on different overground surfaces. Running on artificial grass or synthetic rubber caused greater GRFs than running on concrete. However, only synthetic rubber could reduce joint loads.

Anterior cruciate ligament injury patterns and their relationship to fatigue and physical fitness levels - a cross-sectional study

Anterior cruciate ligament (ACL) injury is one of the most common knee injuries that leads to many consequences such as early osteoarthritis and knee joint instability.To explore the association of the types of ACL tear (complete and partial) and side of injury (dominant vs nondominate) with types of playing surfaces, sports, shoes, and mechanism of injuries as well as to determine whether higher levels of fatigue and physical fitness are risk factors for complete ACL tear.This cross-sectional study used a questionnaire to collect information from young male adults with a confirmed ACL injury who were attending rehabilitation programs. The outcomes of interest were patterns of ACL injury, levels of fatigue before the injury on a 0 to 10 scale, and levels of physical fitness (hours per week). Mann-Whitney U and Kruskal Wallis tests were used to assess the differences between groups, while the odds ratios were calculated to evaluate risk factors for complete ACL tear.One hundred thirteen young male adults with a confirmed ACL injury were enrolled. Most of the reported ACL injuries in this study were complete tear (80.5%) and occurred more frequently in the dominant leg (74.6%) due to noncontact mechanism (63.6%). More ACL injuries happened while playing soccer (97.2%) on artificial turf (53.3%). The level of fatigue before ACL injury was significantly higher in partial ACL tear injuries compared to complete ACL tear injuries (P = .014). For every 1-point increase in the level of fatigue on a 0-10 scale, there was a 25% reduction in complete ACL injury risk (P = .023).The pattern of ACL types of tear and side of injury varies in different playing surfaces and mechanisms of injuries. Higher levels of fatigue seem to be associated with a partial tear of the ACL and reduction of a complete ACL tear risk factor.

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

Background:

Anterior cruciate ligament (ACL) injury is prevalent among National Collegiate Athletic Association (NCAA) soccer players. Controversy remains regarding the effect of the surface type on the rate of ACL injury in soccer players, considering differences in sex, type of athletic exposure, and level of competition.

Hypothesis:

Natural grass surfaces would be associated with decreased ACL injury rate in NCAA soccer players. Sex, type of athletic exposure (match vs practice), and level of competition (Division I-III) would affect the relationship between playing surface and ACL injury rates.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Using the NCAA Injury Surveillance System (ISS) database, we calculated the incidence rate of ACL injury in men and women from 2004-2005 through 2013-2014 seasons. The incidence was normalized against athletic exposure (AE). Additional data collected were sex, athletic activity at time of injury (match vs practice), and level of competition (NCAA division) to stratify the analysis. Statistical comparisons were made by calculating incidence rate ratios (IRR). Statistical significance was set at an alpha of .05.

Results:

There were 30,831,779 weighted AEs during the study period. The overall injury rate was 1.12 ACL injuries per 10,000 AEs (95% CI, 1.08-1.16). Women comprised 57% of the match data (10,261 games) and 55% of practice data (26,664 practices). The overall injury rate was significantly higher on natural grass (1.16/10,000 AEs; 95% CI, 1.12-1.20) compared with artificial turf (0.92/10,000 AEs [95% CI, 0.84-1.01]; IRR, 1.26 [95% CI, 1.14-1.38]) (P < .0001). This relationship was demonstrated consistently across all subanalyses, including stratification by NCAA division and sex. The injury rate on natural grass (0.52/10,000 AEs; 95% CI, 1.11-1.26) was significantly greater than the injury incidence during practice on artificial turf (0.06/10,000 AEs; 95% CI, 0.043-0.096). Players were 8.67 times more likely to sustain an ACL injury during practice on natural grass compared with practice on artificial turf (95% CI, 5.43-12.13; P < .0001). No significant difference was found in injury rates between matches played on grass versus turf (IRR, 0.93; 95% CI, 0.84-1.03; P = .15).

Conclusion:

NCAA soccer players who practice on natural grass have increased risk of ACL injury compared with the risk of those practicing on an artificial surface, regardless of sex or NCAA division of play. No difference in risk of ACL injury between playing surfaces was detected during matches. Further research is necessary to examine the effect of multiple factors when evaluating the effect of the surface type on the risk of ACL injury in soccer players.

Plantar Loads of Habitual Forefoot Strikers during Running on Different Overground Surfaces

The objective of this study is to investigate plantar loads characteristics of habitual forefoot strike runners while running on different surfaces. Twenty-six runners (age: 28.2 ± 6.8 y, height: 172.9 ± 4.1 cm, weight: 67.7 ± 9.6 kg, BMI (body mass index): 22.6 ± 2.8 kg/m2, running age: 5.0 ± 4.2 y, running distance per week: 14.6 ± 11.7 km) with habitual forefoot strike participated in the study. Runners were instructed to run at 3.3 ± 0.2 m/s on three surfaces: grass, synthetic rubber and concrete. An in-shoe pressure measurement system was used to collect and analyze plantar loads data. Running on the synthetic rubber surface produced a lower plantar pressure in the lateral forefoot (256.73 kPa vs. 281.35 kPa, p = 0.006) than running on concrete. Compared with the concrete surface, lower pressure–time integrals were shown at the central forefoot (46.71 kPa⋅s vs. 50.73 kPa⋅s, p = 0.001) and lateral forefoot (36.13 kPa⋅s vs. 39.36 kPa⋅s, p = 0.004) when running on the synthetic rubber surface. The different surfaces influence plantar loads of habitual forefoot strikers and runners should choose appropriate overground surface to reduce the risk of lower extremity musculoskeletal injuries.

Movement Technique During Jump-Landing Differs Between Sex Among Athletic Playing Surfaces

Pryor, JL, Burbulys, ER, Root, HJ, and Pryor, RR. Movement technique during jump-landing differs between sex among athletic playing surfaces. J Strength Cond Res XX(X): 000-000, 2020-Whether athletic surface type affects movement technique, a causal factor for lower extremity injury, is unclear. This study evaluated the influence of 4 common athletic surfaces on movement technique using the Landing Error Scoring System (LESS). Secondarily, we aimed to evaluate differences in movement technique between men and women among surfaces. Recreationally active men and women (n = 38) completed jump-landing tests on 4 common athletic surfaces in a quasi-randomized crossover fashion. Vertical jump height, perceptual fatigue, and muscle soreness were evaluated before jump-landing movement analyses and were similar across testing sessions (p > 0.05). Men achieved higher LESS scores on hardwood and artificial pellet turf compared with women (p ≤ 0.037). Women exhibited lower LESS scores on grass and artificial turf vs. concrete (p ≤ 0.048). Data indicate differential lower extremity movement technique and therefore injury risk across athletic surface types and sex, challenging the generalizability of the LESS construct. Athletic playing surface should be considered during movement technique assessment and implementation of injury prevention programs.

Incidence of Knee Injuries on Artificial Turf Versus Natural Grass in National Collegiate Athletic Association American Football: 2004-2005 Through 2013-2014 Seasons

BACKGROUND

The use of artificial turf in American football continues to grow in popularity, and the effect of these playing surfaces on athletic injuries remains controversial. Knee injuries account for a significant portion of injuries in the National Collegiate Athletic Association (NCAA) football league; however, the effect of artificial surfaces on knee injuries remains ill-defined.

HYPOTHESIS

There is no difference in the rate or mechanism of knee ligament and meniscal injuries during NCAA football events on natural grass and artificial turf playing surfaces.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

The NCAA Injury Surveillance System Men's Football Injury and Exposure Data Sets for the 2004-2005 through 2013-2014 seasons were analyzed to determine the incidence of anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), medial meniscus, and lateral meniscal tear injuries. Injury rates were calculated per 10,000 athlete exposures, and rate ratios (RRs) were used to compare injury rates during practices and competitions on natural grass and artificial turf in NCAA football as a whole and by competition level (Divisions I, Divisions II and III). Mechanisms of injury were calculated for each injury on natural grass and artificial turf surfaces.

RESULTS

A total of 3,009,205 athlete exposures and 2460 knee injuries were reported from 2004 to 2014: 1389 MCL, 522 ACL, 269 lateral meniscal, 164 medial meniscal, and 116 PCL. Athletes experienced all knee injuries at a significantly higher rate when participating in competitions as compared with practices. Athletes participating in competitions on artificial turf experienced PCL injuries at 2.94 times the rate as those playing on grass (RR = 2.94; 95% CI, 1.61-5.68). When stratified by competition level, Division I athletes participating in competitions on artificial turf experienced PCL injuries at 2.99 times the rate as those playing on grass (RR = 2.99; 95% CI, 1.39-6.99), and athletes in lower NCAA divisions (II and III) experienced ACL injuries at 1.63 times the rate (RR = 1.63; 95% CI, 1.10-2.45) and PCL injuries at 3.13 times the rate (RR = 3.13; 95% CI, 1.14-10.69) on artificial turf as compared with grass. There was no statistically significant difference in the rate of MCL, medial meniscal, or lateral meniscal injuries on artificial turf versus grass when stratified by event type or level of NCAA competition. No difference was found in the mechanisms of knee injuries on natural grass and artificial turf.

CONCLUSION

Artificial turf is an important risk factor for specific knee ligament injuries in NCAA football. Injury rates for PCL tears were significantly increased during competitions played on artificial turf as compared with natural grass. Lower NCAA divisions (II and III) also showed higher rates of ACL injuries during competitions on artificial turf versus natural grass.

Anterior cruciate ligament injury risk factors in football

INTRODUCTION

Anterior cruciate ligament (ACL) lesion represents one of the most dramatic injuries in a football (soccer) player's career. There are many injury risk factors related to intrinsic (non-modifiable) and/or extrinsic (modifiable) factors of ACL injury.

EVIDENCE ACQUISITION

Research of the studies was conducted until September 2018 without publication data limitation or language restriction on the following databases: PubMed/MEDLINE, Scopus, ISI, EXCERPTA.

EVIDENCE SYNTHESIS

To date, evidence from the literature suggests that the risk of ACL injury is multifactorial and involves biomechanical, anatomical, hormonal, and neuromuscular factors. Despite this relative complexity, the mechanisms of injury are well known and rationally classified into two categories: mechanisms of injury based on contact or on non-contact with another player, with the non-contact injury mechanisms clearly prevailing over the mechanisms of contact injury. One of the most frequent biomechanical risk factors, associated with ACL non-contact injury, is represented by the valgus knee in the pivoting and cutting movements and in the landing phase after jumping. Gender-related risk factors show female populations to have a higher predisposition to ACL injury than males However, there are still some theoretical and practical aspects that need further investigation such as; genetic risks together with the role of estrogen and progesterone receptors in female populations, and the in-vivo interaction shoe-playing surface. In particular, the genetic risk factors of ACL lesion seem to be an interesting and promising field of investigation, where considerable progress has still to be made.

CONCLUSIONS

This narrative review provides an insight into the risk factors of ACL injury that could be used by practitioners for preventing injury in football (soccer).

Higher Rates of Lower Extremity Injury on Synthetic Turf Compared With Natural Turf Among National Football League Athletes: Epidemiologic Confirmation of a Biomechanical Hypothesis

BACKGROUND

Biomechanical studies have shown that synthetic turf surfaces do not release cleats as readily as natural turf, and it has been hypothesized that concomitant increased loading on the foot contributes to the incidence of lower body injuries. This study evaluates this hypothesis from an epidemiologic perspective, examining whether the lower extremity injury rate in National Football League (NFL) games is greater on contemporary synthetic turfs as compared with natural surfaces.

HYPOTHESIS

Incidence of lower body injury is higher on synthetic turf than on natural turf among elite NFL athletes playing on modern-generation surfaces.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Lower extremity injuries reported during 2012-2016 regular season games were included, with all 32 NFL teams reporting injuries under mandated, consistent data collection guidelines. Poisson models were used to construct crude and adjusted incidence rate ratios (IRRs) to estimate the influence of surface type on lower body injury groupings (all lower extremity, knee, ankle/foot) for any injury reported as causing a player to miss football participation as well as injuries resulting in ≥8 days missed. A secondary analysis was performed on noncontact/surface contact injuries.

RESULTS

Play on synthetic turf resulted in a 16% increase in lower extremity injuries per play than that on natural turf (IRR, 1.16; 95% CI, 1.10-1.23). This association between synthetic turf and injury remained when injuries were restricted to those that resulted in ≥8 days missed, as well as when categorizations were narrowed to focus on distal injuries anatomically closer to the playing surface (knee, ankle/foot). The higher rate of injury on synthetic turf was notably stronger when injuries were restricted to noncontact/surface contact injuries (IRRs, 1.20-2.03; all statistically significant).

CONCLUSION

These results support the biomechanical mechanism hypothesized and add confidence to the conclusion that synthetic turf surfaces have a causal impact on lower extremity injury.

The First Decade of Web-Based Sports Injury Surveillance (2004-2005 Through 2013-2014): Methods of the National Collegiate Athletic Association Injury Surveillance Program and High School Reporting Information Online

OBJECTIVE: 

To describe the methods of the National Collegiate Athletic Association (NCAA) Injury Surveillance Program (ISP) and High School Reporting Information Online (HS RIO) system as a complement to the sport-specific manuscripts that will follow.

BACKGROUND: 

The NCAA-ISP and HS RIO collect injury and exposure data from samples of collegiate and high school sports programs, respectively. The NCAA-ISP, which the NCAA has maintained since 1982, was relaunched as a Web-based platform at the beginning of the 2004-2005 academic year. In 2005, the HS RIO was introduced to capture data on high school athletes and modeled after the NCAA-ISP. Relevant data are shared with the NCAA and high school sport and policy committees to develop evidence-based rules and programs that help protect the health and safety of student-athletes.

DESCRIPTION: 

The NCAA-ISP and HS RIO monitor participation in school-sanctioned competitions and practices that occur from the first preseason practice to the final postseason contest for more than 25 sports. For this series of publications in the Journal of Athletic Training, injury information on 13 sports at the collegiate level during the 2004-2005 through 2013-2014 academic years and the high school level during the 2005-2006 through 2013-2014 academic years was evaluated.

CONCLUSIONS: 

Athletic trainers have been a vital source of data collection over the past decade to help produce the largest datasets of collegiate and high school sports injuries. Such data have helped various sport and policy committees advance protocols that aim to increase sports safety. This series of publications will aid by continuing to provide data to stakeholders in the sports community.

Synthetic Turf: History, Design, Maintenance, and Athlete Safety

CONTEXT:

Synthetic turf has become an increasingly common playing surface for athletics and has changed dramatically since its introduction more than 50 years ago. Along with changes to surface design, maintenance needs and recommendations have become more standardized and attentive both to upkeep and player-level factors. In particular, synthetic turf maintenance as it relates to athlete health and safety is an important consideration at all levels of play.

EVIDENCE ACQUISITION:

A literature search of MEDLINE and PubMed for publications between the years 1990 and 2018 was conducted. Keywords included s ynthetic turf, artificial turf, field turf, and playing surface. Additionally, expert opinion through systematic interviews and practical implementation were obtained on synthetic turf design and maintenance practices in the National Football League.

STUDY DESIGN:

Clinical review.

LEVEL OF EVIDENCE:

Level 5.

RESULTS:

Synthetic turf has changed considerably since its inception. Playing surface is a critical component of the athletic environment, playing a role both in performance and in athlete safety. There are several important structural considerations of third-generation synthetic turf systems currently used in the United States that rely heavily on strong and consistent maintenance. A common misconception is that synthetic turf is maintenance free; in fact, however, these surfaces require routine maintenance. Whether athletes experience more injuries on synthetic over natural surfaces is also of interest among various levels and types of sport.

CONCLUSION:

Modern synthetic turf is far different than when originally introduced. It requires routine maintenance, even at the level of local athletics. It is important for sports medicine personnel to be familiar with playing surface issues as they are often treating athletes at the time of injury and should maintain a level of awareness of contemporary research and practices regarding the relationships between synthetic turf and injury.

The NFL's Chop-Block Rule Change: Does It Prevent Knee Injuries in Defensive Players?

Background:

The chop block, a football maneuver in which an offensive player blocks an opponent around the thigh while another offensive player engages the same opponent above the waist, was declared illegal by the National Football League (NFL) before the 2016-2017 season. Chop blocks have been hypothesized to be associated with medial collateral ligament and anterior cruciate ligament injury, especially in offensive/defensive linemen.

Purpose:

To quantify the impact that the chop-block rule change had on the incidence of knee injuries to defensive players in the NFL over 4 seasons (2014-2018).

Study Design:

Cohort study; Level of evidence, 3.

Methods:

NFL injury data for all defensive players from regular-season games played from 2014 through 2018 were collected. For this study, all knee injuries were attributed to competitive game play. Injury rates were reported as the number of injuries per 1000 athletic exposures (with 95% CIs).

Results:

A total of 256 games were played during the 2014-2015, 2015-2016, 2016-2017, and 2017-2018 NFL regular seasons, and all were included in this study. Among defensive players, the relative risk for a knee injury per 1000 athletic exposures was 0.84 (95% CI, 0.75-0.96) for the 2 seasons after the chop-block rule change (2016-2017 and 2017-2018) versus the 2 seasons before (2014-2015 and 2015-2016) (P = .009). Thus, the relative risk reduction was 16%. The relative risk for a defensive player to be placed on injured reserve per season was 0.90 (95% CI, 0.72-1.13) for the 2 seasons after the rule change versus the 2 seasons before (P = .39).

Conclusion:

The NFL’s recent ruling against in-game chop blocks may have reduced the incidence of knee injuries among defensive players.

Video Analysis of Anterior Cruciate Ligament Tears in Professional American Football Athletes

BACKGROUND

Anterior cruciate ligament (ACL) injuries are prevalent in contact sports that feature cutting and pivoting, such as American football. These injuries typically require surgical treatment, can result in significant missed time from competition, and may have deleterious long-term effects on an athlete's playing career and health. While the majority of ACL tears in other sports have been shown to occur from a noncontact mechanism, it stands to reason that a significant number of ACL tears in American football would occur after contact, given the nature of the sport. Hypothesis/Purpose: The purpose was to describe the mechanism, playing situation, and lower extremity limb position associated with ACL injuries in professional American football players through video analysis to test the hypothesis that a majority of injuries occur via a contact mechanism.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A retrospective cohort of National Football League (NFL) players with ACL injuries from 3 consecutive seasons (2013-2016) was populated by searching publicly available online databases and other traditional media sources. Of 156 ACL injuries identified, 77 occurred during the regular season and playoffs, with video analysis available for 69 injuries. The video of each injury was independently viewed by 2 reviewers to determine the nature of the injury (ie, whether it occurred via a noncontact mechanism), the position of the lower extremity, and the football activity at the time of injury. Playing surface, player position, and time that the injury occurred were also recorded.

RESULTS

Contrary to our hypothesis, the majority of ACL injuries occurred via a noncontact mechanism (50 of 69, 72.5%), with the exception of injury to offensive linemen, who had a noncontact mechanism in only 20% of injuries. For noncontact injuries, the most common football activity at the time of injury was pivoting/cutting, and the most common position of the injured extremity included hip abduction/flexion, early knee flexion/abduction, and foot abduction/external rotation. There was no association between injury mechanism and time of injury or playing surface in this cohort.

CONCLUSION

In this study of players in the NFL, the majority of ACL tears involved a noncontact mechanism, with the lower extremity exhibiting a dynamic valgus moment at the knee. These findings suggest that ACL injury prevention programs may reduce the risk of noncontact ACL tears in American football players.

Does the FIFA 11+ Injury Prevention Program Reduce the Incidence of ACL Injury in Male Soccer Players?

BACKGROUND

The FIFA 11+ injury prevention program has been shown to decrease the risk of soccer injuries in men and women. The program has also been shown to decrease time loss resulting from injury. However, previous studies have not specifically investigated how the program might impact the rate of anterior cruciate ligament (ACL) injury in male soccer players.

QUESTIONS/PURPOSES

The purpose of this study was to examine if the FIFA 11+ injury prevention program can (1) reduce the overall number of ACL injuries in men who play competitive college soccer and whether any potential reduction in rate of ACL injuries differed based on (2) game versus practice setting; (3) player position; (4) level of play (Division I or II); or (5) field type.

METHODS

This study was a prospective cluster randomized controlled trial, which was conducted in 61 Division I and Division II National Collegiate Athletic Association men's soccer teams over the course of one competitive soccer season. The FIFA 11+ is a 15- to 20-minute on-the-field dynamic warm-up program used before training and games and was utilized as the intervention throughout the entire competitive season. Sixty-five teams were randomized: 34 to the control group (850 players) and 31 to the intervention group (675 players). Four intervention teams did not complete the study and did not submit their data, noting insufficient time to complete the program, reducing the number for per-protocol analysis to 61. Compliance to the FIFA 11+ program, athletic exposures, specific injuries, ACL injuries, and time loss resulting from injury were collected and recorded using a secure Internet-based system. At the end of the season, the data in the injury surveillance system were crosshatched with each individual institution's internal database. At that time, the certified athletic trainer signed off on the injury collection data to confirm their accuracy and completeness.

RESULTS

A lower proportion of athletes in the intervention group experienced knee injuries (25% [34 of 136]) compared with the control group (75% [102 of 136]; relative risk [RR], 0.42; 95% confidence interval [CI], 0.29-0.61; p < 0.001). When the data were stratified for ACL injury, fewer ACL injuries were reported in the intervention group (16% [three of 19]) compared with the control group (84% [16 of 19]), accounting for a 4.25-fold reduction in the likelihood of incurring ACL injury (RR, 0.236; 95% CI, 0.193-0.93; number needed to treat = 70; p < 0.001). With the numbers available, there was no difference between the ACL injury rate within the FIFA 11+ group and the control group with respect to game and practice sessions (games-intervention: 1.055% [three of 15] versus control: 1.80% [12 of 15]; RR, 0.31; 95% CI, 0.09-1.11; p = 0.073 and practices-intervention: 0% [zero of four] versus control: 0.60% [four of four]; RR, 0.14; 95% CI, 0.01-2.59; p = 0.186). With the data that were available, there were no differences in incidence rate (IR) or injury by player position for forwards (IR control = 0.339 versus IR intervention = 0), midfielders (IR control = 0.54 versus IR intervention = 0.227), defenders (IR control = 0.339 versus IR intervention = 0.085), and goalkeepers (IR control = 0.0 versus IR intervention = 0.0) (p = 0.327). There were no differences in the number of ACL injuries for the Division I intervention group (0.70% [two of nine]) compared with the control group (1.05% [seven of nine]; RR, 0.30; CI, 0.06-1.45; p = 0.136). However, there were fewer ACL injuries incurred in the Division II intervention group (0.35% [one of 10]) compared with the control group (1.35% [nine of 10]; RR, 0.12; CI, 0.02-0.93; p = 0.042). There was no difference between the number of ACL injuries in the control group versus in the intervention group that occurred on grass versus turf (Wald chi square [1] = 0.473, b = 0.147, SE = 0.21, p = 0.492). However, there were more ACL injuries that occurred on artificial turf identified in the control group (1.35% [nine of 10]) versus the intervention group (0.35% [one of 10]; RR, 0.14; 95% CI, 0.02-1.10; p = 0.049).

CONCLUSIONS

This program, if implemented correctly, has the potential to decrease the rate of ACL injury in competitive soccer players. In addition, this may also enhance the development and dissemination of injury prevention protocols and may mitigate risk to athletes who utilize the program consistently. Further studies are necessary to analyze the cost-effectiveness of the program implementation and to analyze the efficacy of the FIFA 11+ in the female collegiate soccer cohort.

LEVEL OF EVIDENCE

Level I, therapeutic study.

The influence of playing surface on injury risk in italian elite rugby players

BACKGROUND

There is a growing interest in the use of artificial turf surfaces in rugby. In particular, artificial surfaces may be an useful means of increasing participation in the sport by allowing greater usage of a given pitch, especially in regions where natural turf pitches are difficult to maintain.

METHODS

The incidence of site, nature, cause, and severity of training and match injuries was prospectively recorded in two professional teams (one equipped with World Rugby certified third generation artificial turf and the other with natural grass over the 2014-2015 season).

RESULTS

A total of 23,840 minutes of exposure was displayed for the whole sample, 1,440 minutes during matches and 22,400 during training sessions. We recorded 37 (48%) traumatic injuries and 39 (52%) overuse injuries. For traumatic injuries, we did not find significant differences in the overall risk injury between grass and artificial turf considering match exposure and training sessions. For overuse injuries, there were significant differences in the overall risk injury between grass and artificial turf considering match exposure (p=0.03) and training sessions (p=0.02).

CONCLUSION

In elite Italian rugby players, artificial turf seems to be safe in regards to traumatic injury while it seems to be a risk factor for overuse injuries.

LEVEL OF EVIDENCE

II.

Prevention of Primary ACL Injuries: A Novel, Innovative Approach

Anterior cruciate ligament (ACL) injuries are increasing amongst professional and recreational athletes, and creating prevention programs to reduce the occurrence of ACL damages is becoming a necessity. To prevent an ACL tear, it is necessary to comprehend the mechanisms and the risk factors of injury. Biomechanical and clinical studies try to understand these complex mechanisms in order to identify factors that can be improved and to develop training programs to prevent at least non-contact ACL injuries. There are several promising programs, but there are still many questions to answer. This paper analyzes the risk factors for ACL injuries and some aspects of the modern programs developed to decrease the rate of ACL tears.

EFFECTS OF FOOTWEAR VARIATIONS ON THREE-DIMENSIONAL KINEMATICS AND TIBIAL ACCELERATIONS OF SPECIFIC MOVEMENTS IN AMERICAN FOOTBALL

American football is associated with a high rate of non-contact chronic injuries. Players are able to select from both high and low cut footwear. The aim of the current investigation was to examine the influence of high and low cut American football specific footwear on tibial accelerations and three-dimensional (3D) kinematics during three sport specific movements. Twelve male American football players performed three movements, run, cut and vertical jump whilst wearing both low and high cut footwear. 3D kinematics of the lower extremities were measured using an eight-camera motion analysis system alongside tibial acceleration parameters which were obtained using a shank mounted accelerometer. Tibial acceleration and 3D kinematic differences between the different footwear were examined using either repeated measures or Friedman’s ANOVA. Tibial accelerations were significantly greater in the low cut footwear in comparison to the high cut footwear for the run and cut movements. In addition, peak ankle eversion and tibial internal rotation parameters were shown to be significantly greater in the low cut footwear in the running and cutting movement conditions. The current study indicates that the utilization of low cut American football footwear for training/performance may place American footballers at increased risk from chronic injuries.

Effect of Exposure Type and Timing of Injuries in Division I College Football: A 4-year Single Program Analysis

BACKGROUND

Football players compete with a high risk of injury due to the sport. With the recent efforts to improve safety, the National Collegiate Athletic Association (NCAA) established new terminology to clearly define exposure types and reduce the number of high contact exposures.

OBJECTIVES

To compare football injury rates (IR) with a focus on game versus practice, time in season of injury, mechanism of injury and utilizing recent exposure types defined by the NCAA (live contact, full-pads and non-contact).

METHODS

Licensed medical professionals monitored a college football program regular season from 2012-2015. Each injury was classified by timing of the injury, mechanism of injury, and whether it occurred in game or practice. Player attendance and type of exposure (non-contact, full-pad or live contact, which involves live tackling to the ground and/or full-speed blocking and can occur in full-pad or half-pad ('shell') equipment) was documented. IR were calculated per 1000 athlete-exposures (AE). Mid-exact P tests compared rates between variables.

RESULTS

The game IR was over three times as high as the practice IR (p < .001). Live contact exposures had the greatest IR of 5.702/1000 AE and were seven times more likely to produce an injury compared to non-contact exposures (p < .001); whereas, live contact exposures were about two times more likely to produce an injury compared to full-pad exposures (p = .004). The majority of injuries observed occurred from a contact mechanism (IR: 2.508/1000 AE). The highest IR during the fall football season occurred in the pre-season at 5.769/1000 AE.

CONCLUSION

Overall IR observed in this cohort were lower than prior studies published before recent NCAA rule changes and guideline implementation to improve athlete safety. Athletes in this cohort were at significantly increased risk of injury from live contact exposures.

Incidence and Epidemiology of Foot and Ankle Injuries in Elite Collegiate Athletes

BACKGROUND

Foot and ankle injuries are increasing in competitive professional and collegiate athletics. Many of these injuries result in considerable missed time from sports and often require surgical intervention. To develop and implement effective practice participation strategies, return-to-play protocols, and injury prevention programs, an understanding of injury trends and epidemiology is vital.

PURPOSE

This study aimed to evaluate the incidence of foot and ankle injuries in elite athletes participating in 37 sports at a single National Collegiate Athletics Association (NCAA) Division 1 institution.

STUDY DESIGN

Descriptive epidemiological study.

METHODS

We evaluated the injury records of all varsity sports at a single NCAA Division 1 athletics program, including 1076 athletes participating in 37 sports. Detailed injury data were prospectively collected in a secure electronic database over a 2-year period. We reviewed the database for all foot/ankle injuries. Inclusion criteria were any foot/ankle injury that was sustained during an NCAA-sanctioned event and subsequently received medical treatment. Independent variables included athlete and injury demographics, missed days, physician visits, imaging results, and whether the injury required surgery. Injury incidence, relative frequency distributions, and sample proportions were dependent metrics for this investigation.

RESULTS

During the study period, a total of 3861 total musculoskeletal injuries were recorded. There were 1035 foot/ankle injuries (27%). Of all foot/ankle injuries, 21% (218 of 1035) caused the athlete to miss at least 1 day of participation, with an average of 12.3 days of time loss from sport. Furthermore, 27% of athletes with foot/ankle injuries were referred for office evaluation by a physician, and 84% of these required radiologic imaging. The overall injury incidence rate was 3.80 per 1000 athlete-exposures (AEs). The 4 sports with the highest incidence rate (>75th percentile) were women's gymnastics, women's cross-country, women's soccer, and men's cross country. The most frequently occurring foot/ankle injuries were ankle ligament injuries, tendinopathies or fasciopathies, and bone stress injuries.

CONCLUSION

The prevalence of foot/ankle injury in a large NCAA Division 1 athletics program was 27% of total musculoskeletal injuries over a 2-year period, with 21% of these injuries resulting in missed time. There were significantly higher foot and ankle injury incidence rates and more missed time in female athletes and women's sports.

Increasing Lower Extremity Injury Rates Across the 2009-2010 to 2014-2015 Seasons of National Collegiate Athletic Association Football: An Unintended Consequence of the "Targeting" Rule Used to Prevent Concussions?

BACKGROUND

Sports-related concussions (SRCs) have gained increased societal interest in the past decade. The National Collegiate Athletic Association (NCAA) has implemented legislation and rule changes to decrease the incidence and risk of head injury impacts. The "targeting" rule forbids initiating contact with the crown of a helmet and targeting defenseless players in the head and neck area; however, there are concerns that this rule change has unintentionally led to an increased incidence of lower extremity injuries.

PURPOSE/HYPOTHESIS

The purpose of this study was to evaluate the change in lower extremity injury rates in NCAA football during the 2009-2010 to 2014-2015 seasons. We hypothesized that the lower extremity injury rate has increased across the time period.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Sixty-eight NCAA football programs provided 153 team-seasons of data to the NCAA Injury Surveillance Program. Lower extremity injuries (ie, hip/groin, upper leg/thigh, knee, lower leg/Achilles, foot/toes) and SRCs sustained during NCAA football games were examined. We calculated injury rates per 1000 athlete-exposures (AEs) for lower extremity injuries and SRCs. Rate ratios (RRs) compared injury rates between the 2009-2010 to 2011-2012 and 2012-2013 to 2014-2015 seasons.

RESULTS

Overall, 2400 lower extremity injuries were reported during the 2009-2010 to 2014-2015 seasons; most were to the knee (33.6%) and ankle (28.5%) and caused by player contact (59.2%). The lower extremity injury rate increased in 2012-2013 to 2014-2015 compared with 2009-2010 to 2011-2012 (23.55 vs 20.45/1000 AEs, respectively; RR, 1.15; 95% CI, 1.06-1.25). This finding was retained when restricted to injuries due to player contact (RR, 1.19; 95% CI, 1.07-1.32) but not for injuries due to noncontact/overuse (RR, 0.96; 95% CI, 0.80-1.14). When examining player contact injury rates by anatomic site, only ankle injuries had an increase (RR, 1.36; 95% CI, 1.13-1.64). The SRC rate also increased in 2012-2013 to 2014-2015 compared with 2009-2010 to 2011-2012 (3.52 vs 2.63/1000 AEs, respectively; RR, 1.34; 95% CI, 1.08-1.66).

CONCLUSION

The lower extremity injury rate has increased in NCAA football athletes. Similarly, SRC rates have increased, although this may be caused by concurrent policies related to better education, identification, and management. Targeting rule changes may be contributing to increased rates of player contact-related ankle injuries. Alongside continued surveillance research to examine longitudinal time trends, more in-depth individual-level examinations of how targeting rule changes influence coaching and player behaviors are warranted.

Variables Affecting Return to Play After Anterior Cruciate Ligament Injury in the National Football League

BACKGROUND

Anterior cruciate ligament (ACL) injuries are common in the National Football League (NFL). Limited literature exists regarding return to play (RTP) and the factors affecting RTP after ACL reconstruction in NFL players.

PURPOSE/HYPOTHESIS

To determine RTP rates after ACL reconstruction in NFL players and to ascertain which variables affect RTP in these players. We hypothesized that RTP in this population will be less than in the general population and similar to the limited studies published previously.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 92 NFL athletes who sustained ACL injuries requiring ACL reconstruction from 2013 to 2015 were retrospectively studied to determine rate of RTP and the variables affecting RTP.

RESULTS

Sixty-two percent (57/92) of NFL athletes returned to NFL game play prior to the end of the 2015-2016 postseason. ACL injuries were noted in 10 different player positions, with 81.5% of all injuries as isolated ACL injuries (75/92) and 18.5% with concomitant knee injuries. A significant difference in ability to RTP was found for players who sustained in-season injuries compared with those who sustained off-season/preseason injuries (P = .02). No significant differences in RTP were found for players who played less than 4 years in the NFL compared with those who played longer. The mean draft round of players who returned was 3.96, with the odds ratio favoring RTP at 4.44 (P = .003) for players drafted in the first 3 rounds of the NFL draft compared with those drafted in the fourth round or later. No significant differences were found with regard to playing surface, laterality, concomitant injury, previous ipsilateral or contralateral ACL reconstruction, final outcome of the game, or contact compared with noncontact injuries.

CONCLUSION

The RTP rates we reported after ACL reconstruction in NFL players are similar to prior studies; however, running backs and wide receivers had lower rates of RTP than previously reported. As previously published, quarterbacks were found to have high RTP rates. Most ACL injuries take place during the preseason or early regular season. Early selection in the NFL draft was a strong predictor of ability to RTP.

The role of shoe design on the prediction of free torque at the shoe-surface interface using pressure insole technology

The goal of the current study was to expand on previous work to validate the use of pressure insole technology in conjunction with linear regression models to predict the free torque at the shoe-surface interface that is generated while wearing different athletic shoes. Three distinctly different shoe designs were utilised. The stiffness of each shoe was determined with a material's testing machine. Six participants wore each shoe that was fitted with an insole pressure measurement device and performed rotation trials on an embedded force plate. A pressure sensor mask was constructed from those sensors having a high linear correlation with free torque values. Linear regression models were developed to predict free torques from these pressure sensor data. The models were able to accurately predict their own free torque well (RMS error 3.72 ± 0.74 Nm), but not that of the other shoes (RMS error 10.43 ± 3.79 Nm). Models performing self-prediction were also able to measure differences in shoe stiffness. The results of the current study showed the need for participant-shoe specific linear regression models to insure high prediction accuracy of free torques from pressure sensor data during isolated internal and external rotations of the body with respect to a planted foot.

A Direct Method for Mapping the Center of Pressure Measured by an Insole Pressure Sensor System to the Shoe's Local Coordinate System

A direct method to express the center of pressure (CoP) measured by an insole pressure sensor system (IPSS) into a known coordinate system measured by motion tracking equipment is presented. A custom probe was constructed with reflective markers to allow its tip to be precisely tracked with motion tracking equipment. This probe was utilized to activate individual sensors on an IPSS that was placed in a shoe fitted with reflective markers used to establish a local shoe coordinate system. When pressed onto the IPSS the location of the probe's tip was coincident with the CoP measured by the IPSS (IPSS-CoP). Two separate pushes (i.e., data points) were used to develop vectors in each respective coordinate system. Simple vector mathematics determined the rotational and translational components of the transformation matrix needed to express the IPSS-CoP into the local shoe coordinate system. Validation was performed by comparing IPSS-CoP with an embedded force plate measured CoP (FP-CoP) from data gathered during kinematic trials. Six male subjects stood on an embedded FP and performed anterior/posterior (AP) sway, internal rotation, and external rotation of the body relative to a firmly planted foot. The IPSS-CoP was highly correlated with the FP-CoP for all motions, root mean square errors (RMSRRs) were comparable to other research, and there were no statistical differences between the displacement of the IPSS-CoP and FP-CoP for both the AP and medial/lateral (ML) axes, respectively. The results demonstrated that this methodology could be utilized to determine the transformation variables need to express IPSS-CoP into a known coordinate system measured by motion tracking equipment and that these variables can be determined outside the laboratory anywhere motion tracking equipment is available.

Risk of Anterior Cruciate Ligament Injury in Athletes on Synthetic Playing Surfaces: A Systematic Review

BACKGROUND

The effect of synthetic playing surfaces on the risk of injury in athletes is frequently debated in the orthopaedic literature. Biomechanical studies have identified increased frictional force at the shoe-surface interface, theoretically increasing the risk of injury relative to natural grass. This increase in frictional force is potentially relevant for the risk of anterior cruciate ligament (ACL) rupture, where noncontact mechanisms are frequent. However, clinical studies examining this issue have shown mixed results.

HYPOTHESIS/PURPOSE

The purpose of this study was to systematically review the available literature on risk of ACL rupture on natural grass versus artificial turf. We hypothesized that the risk of ACL rupture on synthetic playing surfaces would not be higher than that of natural grass playing surfaces.

STUDY DESIGN

Systematic review.

METHODS

A systematic keyword search was performed of OVID, EMBASE, the Cochrane Library of Systematic Reviews, and the PROSPERO International Prospective Register of Systematic Reviews. Candidate articles were included if they reported the risk ratio of ACL rupture on natural grass versus synthetic playing surfaces, were of level 3 evidence or better, and included only ACL injuries sustained during organized athletic events. Exclusion criteria included a study with non-field-related sports and the use of historical cohorts for calculating risk ratios.

RESULTS

A total of 10 studies with 963 ACL injuries met criteria for inclusion, all of which reported on soccer and football cohorts. Among these, 4 studies (753 ACL injuries) found an increased risk of ACL injury on artificial playing surfaces. All 4 of these articles were conducted using American football cohorts, and they included both earlier-generation surfaces (AstroTurf) and modern, 3rd-generation surfaces. Only 1 study in football players found a reduced risk of ACL injury on synthetic playing surfaces. No soccer cohort found an increased risk of ACL injury on synthetic surfaces.

CONCLUSION

High-quality studies support an increased rate of ACL injury on synthetic playing surfaces in football, but there is no apparent increased risk in soccer. Further study is needed to clarify the reason for this apparent discrepancy.

Effects of the NFL's Amendments to the Free Kick Rule on Injuries during the 2010 and 2011 Seasons

Recognizing the chronic health effects associated with playing football, the National Football League (NFL) has enacted policies and rules aimed at improving player health and safety. Prior to the 2011 season, amendments to the Free Kick rule were implemented, whereby the restraining line was moved from the 30- to the 35-yard line and all kicking team players other than the kicker were required to line up no more than 5 yards behind their restraining line. The objective of this analysis was to evaluate the effects of these rule changes on injury rates. Data for injuries occurring on special teams plays during the 2010 and 2011 NFL seasons were obtained from publically available NFL gamebooks and injury reports. Injury rates for kickoff plays across seasons were statistically compared using incidence rate ratios (RR) and 95% confidence intervals. To evaluate whether injury rate changes could be attributable to the rule amendments, comparisons were made with punt injury rates (presumably unaffected by the Free Kick rule changes) and distributions of potential confounders were assessed across seasons. Incidence of injuries occurring on kickoff plays fell from 2010 to 2011 (RR: 0.45, 95% CI: 0.28-0.73), although on kickoff plays where the ball was returned, this decrease became non-significant (RR: 0.67, 95% CI: 0.41-1.08). While the incidence of head injuries decreased by approximately 3-fold during kickoff plays, this change was not statistically significant (RR: 0.33, 95% CI: 0.09-1.21). No difference was observed in injury incidence during punts between the two seasons, and the distribution of confounding factors was largely uniform across seasons. The observed decrease in injuries occurring during kickoffs was likely directly attributable to the Free Kick rule amendments, principally from the increased frequency of touchbacks. The absence of a significant change in head injuries during kickoffs was unexpected, but may be attributable to small sample size. Despite the injury rate reductions, the rule changes likely had little effect on player safety during active gameplay.

Trends in Anterior Cruciate Ligament Reconstruction in the United States

Background:

The anterior cruciate ligament (ACL) is the most frequently injured ligament in the knee for which surgery is performed. United States national estimates of ACL reconstruction vary widely.

Purpose:

This study sought to use the most recently available Centers for Disease Control and Prevention data to investigate changes in the utilization of inpatient and ambulatory surgery for ACL tears in the United States.

Study Design:

Descriptive epidemiology study.

Methods:

The National Survey of Ambulatory Surgery, conducted in 1994, 1995, 1996, and 2006 (data from 1994, 1996, and 2006 were used in the study), and the National Hospital Discharge Survey, conducted between 1990 and 2007, were used to identify cases of ACL reconstruction. The data were analyzed for trends in demographics, treatment, and utilization.

Results:

Between 1994 and 2006, the population-adjusted estimate of the rate of ACL reconstructions increased by 37% (33.0/100,000 capita or 86,837 total procedures to 45.1/100,000 capita or 134,421 total procedures). There was an increase in the proportion of females undergoing reconstruction in both the ambulatory (30% to 40%) and inpatient (29% to 47%) settings over the study period, with a 304% increase in the sex-adjusted estimate of the rate of female ambulatory procedures between 1994 and 2006. Age-adjusted estimates of the rates of ambulatory ACL reconstruction increased among all age groups, with a 924% increase in patients less than 15 years of age. Concurrent meniscectomy remained relatively constant in the ambulatory (37% to 40%) and inpatient (37% to 33%) settings between 1994 and 2007. Private insurance was the largest compensator, representing 77% of cases in 2006. Between 1994 and 2006, the use of peripheral nerve blocks during ambulatory surgery increased from 0.7% to 30.8%.

Conclusion:

The rate of ACL reconstruction increased dramatically between 1990 and 2007 based on the National Survey of Ambulatory Surgery and National Hospital Discharge Survey databases, which represents the most up-to-date publicly available data. Knowledge of this increase and national practice patterns may aid policy makers and surgeons in appropriately allocating health care resources to ensure quality patient care.

Effects of two football stud configurations on biomechanical characteristics of single-leg landing and cutting movements on infilled synthetic turf

Multiple playing surfaces and footwear used in American football warrant a better understanding of relationship between different combinations of turf and footwear. The purpose of this study was to examine effects of shoe and stud types on ground reaction force (GRF) and ankle and knee kinematics of a 180° cut and a single-leg 90° land-cut on synthetic turf. Fourteen recreational football players performed five trials of the 180° cut and 90° land-cut in three shoe conditions: non-studded running shoe, and football shoe with natural and synthetic turf studs. Variables were analyzed with a 3 × 2 (shoe × movement) repeated measures analysis of variance (p < 0.05). Peak vertical GRF (p < 0.001) and loading rate (p < 0.001) were greater during 90° land-cut than 180° cut. For 180° cut, natural turf studs produced smaller peak medial GRFs compared to synthetic turf studs and non-studded shoe (p = 0.012). For land-cut, peak eversion velocity was reduced in running shoes compared to natural (p = 0.016) and synthetic (p = 0.002) turf studs. The 90° land-cut movement resulted in greater peak vertical GRF and loading rate compared to the 180° cut. Overall, increased GRFs in the 90° land-cut movement may increase the chance of injury.

National collegiate athletic association injury surveillance system: review of methods for 2004-2005 through 2013-2014 data collection

BACKGROUND

Since 1982, the National Collegiate Athletic Association has used the Injury Surveillance System (ISS) to collect injury and athlete-exposure data from a representative sample of collegiate institutions and sports. At the start of the 2004-2005 academic year, a Web-based ISS replaced the paper-based platform previously used for reporting injuries and exposures.

OBJECTIVE

To describe the methods of the Web-based National Collegiate Athletic Association ISS for data collection as implemented from the 2004-2005 to 2013-2014 academic years.

DESCRIPTION

The Web-based ISS monitored National Collegiate Athletic Association-sanctioned practices and competitions, the number of participating student-athletes, and time-loss injuries during the preseason, regular season, and postseason in 25 collegiate sports. Starting in the 2009-2010 academic year, non-time-loss injuries were also tracked. Efforts were made to better integrate ISS data collection into the workflow of collegiate athletic trainers. Data for the 2004-2005 to 2013-2014 academic years are available to researchers through a standardized application process available at the Datalys Center Web site.

CONCLUSIONS

As of February 2014, more than 1 dozen data sets have been provided to researchers. The Datalys Center encourages applications for access to the data.

Prevention of anterior cruciate ligament injuries in sports. Part I: systematic review of risk factors in male athletes

PURPOSE

The purpose of this study was to report a comprehensive literature review on the risk factors for anterior cruciate ligament (ACL) injuries in male athletes.

METHODS

All abstracts were read and articles of potential interest were reviewed in detail to determine on inclusion status for systematic review. Information regarding risk factors for ACL injuries in male athletes was extracted from all included studies in systematic fashion and classified as environmental, anatomical, hormonal, neuromuscular, or biomechanical. Data extraction involved general characteristics of the included studies (type of study, characteristics of the sample, type of sport), methodological aspects (for quality assessment), and the principal results for each type of risk factor.

RESULTS

The principal findings of this systematic review related to the risk factors for ACL injury in male athletes are: (1) most of the evidence is related to environmental and anatomical risk factors; (2) dry weather conditions may increase the risk of non-contact ACL injuries in male athletes; (3) artificial turf may increase the risk of non-contact ACL injuries in male athletes; (4) higher posterior tibial slope of the lateral tibial plateau may increase the risk of non-contact ACL injuries in male athletes.

CONCLUSION

Anterior cruciate ligament injury in male athletes likely has a multi-factorial aetiology. There is a lack of evidence regarding neuromuscular and biomechanical risk factors for ACL injury in male athletes. Future research in male populations is warranted to provide adequate prevention strategies aimed to decrease the risk of this serious injury in these populations.

Sport-specific injury pattern recorded during anterior cruciate ligament reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) injuries are more commonly seen with certain cutting and pivoting sports. However, injury patterns associated with these sports have not been well described.

PURPOSE

(1) To describe the patient demographics and injury pattern at the time of ACL reconstruction (ACLR) by activities that lead to ACL injuries and (2) to estimate the association of activities at the time of injury with the odds of isolated ACL injuries as well as with meniscus, cartilage, and multiligament injuries diagnosed at the time of ACLR.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

This study combined 2 ACLR registry cohorts, from Norway and the United States, from 2004 to 2011. A cohort of 10,958 primary ACLRs was included. The most prevalent sports activities at the time of injury were the following: soccer, skiing, American football, basketball, and team handball. The end points were the concurrent injury patterns at the time of ACLR: isolated ACL, meniscus, cartilage, and multiligament injuries.

RESULTS

All sports were compared with the most prevalent injury mechanism: soccer. Skiing injuries were 1.13 (95% confidence interval [CI], 1.01-1.27) times more likely to result in isolated ACL tears, 2.05 (95% CI, 1.01-4.16) times more likely to result in posterior cruciate ligament tears, 1.94 (95% CI, 1.51-2.49) times more likely to result in medial collateral ligament (MCL) tears, and 1.73 (95% CI, 1.38-2.17) times more likely to result in multiligament injuries. Athletes playing American football were 2.72 (95% CI, 1.32-5.62) times more likely to have MCL tears. Those injured playing basketball were 1.28 (95% CI, 1.06-1.54) times more likely to have lateral meniscus tears, 1.23 (95% CI, 1.01-1.51) times more likely to have cartilage damage, and 1.38 (95% CI, 1.11-1.72) times more likely to have meniscus and cartilage injuries. Athletes injured playing team handball were less likely to have MCL tears (odds ratio [OR], 0.68; 95% CI, 0.46-0.99) and more likely to have lateral meniscus injuries (OR, 1.27; 95% CI, 1.10-1.48).

CONCLUSION

Injury patterns were associated with certain sports. Compared with soccer, American football has a higher likelihood of resulting in multiligament injuries, whereas basketball has a higher likelihood of resulting in cartilage and lateral meniscus injuries. Injury patterns seen at the time of surgery may reflect the forces applied to the knee by the specific sports performed.