A review of synthetic playing surfaces, the shoe-surface interface, and lower extremity injuries in athletes

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.

Turf Toe Injuries in the Athlete: an Updated Review of Treatment Options, Rehabilitation Protocols, and Return-to-Play Outcomes

PURPOSE OF REVIEW

First metatarsophalangeal joint sprains or turf toe (TT) injuries occur secondary to forceful hyperextension of the great toe. TT injuries are common among athletes, especially those participating in football, soccer, basketball, dancing, and wrestling. This review summarizes the current treatment modalities, rehabilitation protocols, and return-to-play criteria, as well as performance outcomes of patients who have sustained TT injuries.

RECENT FINDINGS

Less than 2% of TT injuries require surgery, but those that do are typically grade III injuries with damage to the MTP joint, evidence of bony injury, or severe instability. Rehabilitation protocols following non-operative management consist of 3 phases lasting up to 10 weeks, whereas protocols following operative management consist of 4 phases lasting up 20 weeks. Athletes with low-grade injuries typically achieve their prior level of performance. However, among athletes with higher grade injuries, treated both non-operatively and operatively, about 70% are expected to maintain their level of performance. The treatment protocol, return-to-play criteria, and overall performance outcomes for TT injuries depend on the severity and classification of the initial sprain. For grade I injuries, players may return to play once they experience minimal to no pain with normal weightbearing, traditionally after 3-5 days. For grade II injuries, or partial tears, players typically lose 2-4 weeks of play and may need additional support with taping when returning to play. For grade III injuries, or complete disruption of the plantar plate, athletes lose 4-6 weeks or more depending upon treatment strategy.

Influence of playing surface on match injury risk in men's professional rugby union in England (2013-2019)

The use of artificial playing surfaces in professional rugby union is growing, but their effect on the injury risk profile remains unclear. The aim of this study was to examine the effect of playing surface on match injury risk in men's professional rugby in England. Six seasons of injury data (2013/14-2018/19) were collected from 15 professional English, men's rugby teams participating in domestic and European competition. The incidence, severity, and burden of match injuries were compared across playing surfaces. The dataset included 3351 injuries from a combined European and domestic data set (separated in to 2 categories; artificial and natural/hybrid surfaces) and 2675 injuries from a domestic only dataset (separated into 3 categories; artificial, hybrid, and natural surfaces). There were no differences in incidence rates between surface types on combined European and domestic match data, but injury burden was significantly greater on artificial (3082 days/1000 h, 95% CI 2847-3337) in comparison with natural/hybrid surfaces (2364 days/1000 h, 95% CI 2277-2454, p < 0.001). These differences were primarily driven by a significantly greater mean severity of hip/groin, and foot/toe injuries on artificial surfaces. This is the largest study to date to examine the relationship between surface type and injury risk in rugby union. The average severity and burden of injuries sustained on artificial surfaces was significantly greater compared with those sustained on hybrid/natural grass surfaces. This study can inform those involved in selection of surface for elite sport, weighing up the positive and negative elements of the varying surface types.

The Utility of Ultrasound in the Evaluation of Traumatic Hallux Valgus

Isolated disruption of the medial collateral ligament of the great toe is rare and often misdiagnosed as turf toe. It may progress to acquired traumatic hallux valgus, often requiring operative intervention and a longer return to play. This case of a grade II medial collateral ligament injury highlights the importance of a thorough physical examination and consideration of the mechanism of injury. It demonstrates the utility of diagnostic musculoskeletal ultrasound in establishing a specific diagnosis upon initial patient presentation with great toe pain. It is an example of the use of ultrasound in guiding treatment and monitoring interval healing. In this case, differentiation of the injury from the classic "turf toe" led to proper stabilization with a toe spacer and activity modification, thus preventing progression of traumatic hallux valgus and leading to successful nonoperative treatment with full return to sport.

LEVEL OF EVIDENCE

Level V.

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.

Epidemiology of Lower Leg Soft Tissue Injuries in High School Athletes

Background

Annually there are an estimated 4.5 million sports- and recreation-related injuries among children and young adults in the United States. The most common sports-related injuries are to the lower extremities, with two-thirds occurring among children and young adults (age range 5-24 years). The objective is to describe the epidemiology of lower leg injuries across 27 high school (HS) sports over a 3-year period.

Methods

The Datalys Center for Sports Injury Research and Prevention provided lower leg injury data for 27 sports in 147 high schools for 2011-2012 through 2013-2014 academic years from National Athletic Treatment, Injury and Outcomes Network (NATION) HS Surveillance Program.

Results

The overall rate of lower leg injuries over this 3-year period was 1.70 per 10 000 acute events (AEs) (95% CI, 1.59-1.82). In men, the highest number of lower leg injuries was in football (n=181), but indoor track had the highest rate of injury at 2.80 per 10 000 AEs (95% CI, 2.14-3.58). In women, the highest number of lower leg injuries and the highest rate of injury were in cross-country (n=76) at 3.85 per 10 000 AEs (95% CI, 3.03-4.81). The practice injury rate was 0.91 times the competition injury rate (95% CI, 0.78-1.07).

Conclusion

An improved understanding of the most common sports in which lower leg injuries are seen may help direct appropriate resource utilization. Our data would suggest efforts toward prevention of these overuse injuries, especially in football, track, and cross-country may have the greatest impact on the health of student athletes.

Level of Evidence:

Level IV, case series.

Synthetic playing surfaces increase the incidence of match injuries in an elite Rugby Union team

OBJECTIVES

To examine differences in match injury incidence between three playing surfaces in elite Rugby Union.

DESIGN

Prospective cohort.

METHODS

Match injury incidence was assessed in 89 elite Rugby Union players over two-seasons of professional competition (44 matches, 1014 h player exposure). Match injury incidence was assessed on three different playing surfaces; natural grass, hybrid (natural grass combined with approximately 3% synthetic fibres) and fully synthetic (sand and rubber infill). Overall injury incidence, contact and non-contact injury incidence, and the incidence of minor (≤7 d lost) and major (≥8 d lost) injuries were considered using mixed effect models.

RESULTS

Overall match injury incidence doubled on hybrid and synthetic surfaces compared to natural grass (hybrid: OR = 2.58 [95% CI 1.65-4.03], p < 0.001; synthetic: OR = 2.16 [95% CI 1.07-4.37], p = 0.033). Furthermore, the odds of sustaining a contact injury on a pitch containing any synthetic content also increased compared to natural grass (hybrid: OR = 2.31 [95% CI 1.41-3.78], p = 0.001; synthetic: OR = 2.19 [95% CI 1.00-4.77], p = 0.049). The hybrid surface elicited a four times greater likelihood of non-contact injury incidence compared to natural grass (OR = 4.18 [95% CI 1.16-15.04], p = 0.028). However, the playing surface did not affect the severity of match injuries (all p > 0.05).

CONCLUSIONS

The present study suggests that even a small percentage (3%) of synthetic content in the playing surface significantly increases match injury incidence, with an effect seen on both contact and non-contact injury incidence. These findings are important to enable practitioners to be aware of the injury implications of playing matches on hybrid and synthetic pitches.

Foot injuries, playing surface and shoe design: Should we be thinking more about injury prevention

The increasing use of artificial pitches has occurred in a multitude of sports at both professional and amateur levels. Artificial turf has become an extremely attractive option as it is felt to encourage a faster, safer and more entertaining play. However these pitches are not without controversy among sporting professionals and in the media. Foot and ankle injury in sport remains incredibly common and a significant burden on health professionals, but what impact do the new artificial surfaces have on these injuries. This review article aims to establish whether artificial turf has an impact on injury rates in the foot and ankle.

Differences in joint loading during a side-step cutting manoeuvre on different artificial turf infill depths

This study investigated differences in joint loading during a side-step manoeuvre on artificial grass turfs with different infill depths. The kinematics and kinetics of 17 trained male inter-college soccer players performing the manoeuvre were captured using 10 high-speed optical cameras synchronised to a force-platform at sampling frequencies of 250 Hz and 1000 Hz respectively. Significantly larger lateral forces (GRF_xpeak) (p = 0.036), larger anterior/posterior forces (GRF_ypeak) (p = 0.062) and larger vertical forces (GRF_zpeak) (p = 0.390) suggests that turf with greater infill depths may be firmer. This could elicit greater stresses on the lower extremity, thereby increasing the risk of knee ligament injuries. Significant differences were reported only for ankle inversion angle (p = 0.001; ES = 0.74), inversion/eversion ankle moment (p = 0.039; ES = 0.52) and abduction-adduction ankle moment (p = 0.022; ES = 0.79) at GRFz_peak. Lower extremity adaptations to execute the manoeuvre on turf with greater infill depths may have taken place at the ankle rather than the knee. While this change in technique may implicate injuries, greater infill depths can be counter-intuitive where a certain level of hardness in the artificial turf might be necessary which otherwise could affect the athletes' performance and potentially reduce injury risk.

The effect of the change of football turf on knee kinematics of adolescent male football players

BACKGROUND

The aim of this study was to investigate the effect of the change of football turf on knee kinematics of adolescent male football players.

METHODS

Thirteen adolescent male football players were tested by a portable infrared motion analysis system based on markers. The angular displacements of flexion/extension,valgus/varus and internal/external rotation were calculated respectively when players performed 90° shuttle running on artificial turf and natural turf.

RESULTS

The maximum valgus angle and range of valgus/varus were larger when they were changed from artificial turf to natural turf (P<0.05). There were no significant differences in the maximum flexion angle, maximum extension angle, range of flexion/extension, maximum varus angle, maximum internal rotation angle, maximum external rotation angle and range of internal/external rotation (P>0.05).

CONCLUSIONS

The change of football turf has a significant effect on knee kinematics of adolescent male football players. The risk of noncontact anterior cruciate ligament (ACL) injury is increased when players who are changed from artificial turf to natural turf.

An assessment of hallux limitus in university basketball players compared with noncompetitive individuals

BACKGROUND

Injuries of the first metatarsophalangeal joint have lately been receiving attention from researchers owing to the important functions of this joint. However, most of the studies of turf toe injuries have focused on sports played on artificial turf.

METHODS

This study compared the range of motion of the first metatarsophalangeal joint in collegiate basketball players (n = 123) and noncompetitive individuals (n = 123).

RESULTS

A statistically significant difference (P < .001) in range of motion was found between the two groups. The difference between the two sample means was 21.35°.

CONCLUSIONS

With hallux rigidus being a potential sequela of repeated turf toe injuries, it seems likely that subacute turf toe injuries occur in basketball players, leading to degenerative changes that result in hallux limitus.

Shoe and Field Surface Risk Factors for Acute Lower Extremity Injuries Among Female Youth Soccer Players

OBJECTIVE

To describe acute lower extremity injuries and evaluate extrinsic risk factors in female youth soccer.

DESIGN

Nested case-control study.

SETTING

Youth soccer clubs in Seattle, WA.

PARTICIPANTS

Female soccer players (n = 351) ages 11 to 15 years randomly selected from 4 soccer clubs from which 83% of their players were enrolled with complete follow-up for 92% of players.

INTERVENTIONS

Injured players were interviewed regarding injury, field surface, shoe type, and position. Uninjured controls, matched on game or practice session, were also interviewed.

MAIN OUTCOME MEASURES

The association between risk factors and acute lower extremity injury using logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

One hundred seventy-three acute lower extremity injuries occurred involving primarily the ankle (39.3%), knee (24.9%), and thigh (11.0%). Over half (52.9%) recovered within 1 week, whereas 30.2% lasted beyond 2 weeks. During practices, those injured were approximately 3-fold (OR, 2.83; 95% CI, 1.49-5.31) more likely to play on grass than artificial turf and 2.4-fold (95% CI, 1.03-5.96) more likely to wear cleats on grass than other shoe and surface combinations. During games, injured players were 89% (95% CI, 1.03-4.17) more likely to play defender compared with forward.

CONCLUSIONS

Half of the acute lower extremity injuries affected the ankle or knee. Grass surface and wearing cleats on grass increased training injuries.

CLINICAL RELEVANCE

The majority, 64%, of female youth soccer players' acute injuries involve the ankle and knee and injury prevention strategies in this age group should target these areas. When considering playing surfaces for training, communities and soccer organizations should consider the third-generation artificial turf a safe alternative to grass.

Influence of Extrinsic Risk Factors on National Football League Injury Rates

Background:

The risk of injury associated with American football is significant, with recent reports indicating that football has one of the highest rates of all-cause injury, including concussion, of all major sports. There are limited studies examining risk factors for injuries in the National Football League (NFL).

Purpose:

To identify risk factors for NFL concussions and musculoskeletal injuries.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

Injury report data were collected prospectively for each week over the 2012-2013 and 2013-2014 regular seasons for all 32 teams. Poisson regression models were used to identify the relationship between predetermined variables and the risk of the 5 most frequent injuries (knee, ankle, hamstring, shoulder, and concussion).

Results:

A total of 480 games or 960 team games (TGs) from the 2012-2013 and 2013-2014 regular seasons were included in this study. A trend to an increasing risk of concussion and TG ankle injury with decreasing mean game-day temperature was observed. The risk of TG concussion (incidence rate ratio [IRR], 2.16; 95% CI, 1.35-3.45; P = .001) and TG ankle injury (IRR, 1.48; 95% CI, 1.10-1.98; P = .01) was significantly greater for TGs played at a mean game-day temperature of ≤9.7°C (≤49.5°F) compared with a mean game-day temperature of ≥21.0°C (≥69.8°F). The risk of TG shoulder injury was significantly increased for TGs played on grass surfaces (IRR, 1.36; 95% CI, 1.02-1.81; P = .038) compared with synthetic surfaces. The risk of TG injury was not associated with time in season, altitude, time zone change prior to game, or distance traveled to a game.

Conclusion:

This study evaluated extrinsic risk factors for injury in the NFL. A hazardous association was identified for risk of concussion and ankle injury with colder game-day temperature. Further research should be conducted to substantiate this relationship and its potential implication for injury prevention initiatives.

The incidence of injury in a Caribbean amateur women's football league

This prospective study looked at the incidence of injury (IN) sustained by players during a season in an amateur women's football league in Trinidad and Tobago where games were played on grass (GR) and on a new generation artificial turf (AT). The overall incidence of time loss injuries was 27.6/1000 player hours (95% CI: 17.0, 38.2). Most injuries were mild and players returned to play within one week of sustaining an injury. Players who trained predominately on, and played their home games on AT (PAT) sustained significantly fewer injuries when playing games on GR than those sustained while playing on AT (p=0.006). There were no differences in injury rates between games played on AT versus games played on GR (p=0.68). Most injuries were of a non-contact nature and so an injury prevention program should be implemented to reduce the injury rate in this amateur league.

Surgical options for anterior cruciate ligament reconstruction in the young child

PURPOSE OF REVIEW

To review the most recent literature on the epidemiology, diagnosis, treatment, and outcomes of pediatric anterior cruciate ligament injury.

RECENT FINDINGS

There is an increasing prevalence of anterior cruciate ligament injuries in pediatric and adolescent athletes, and nonoperative management of these injuries results in worse outcomes than surgical reconstruction. Prevention exercise protocols are cost-effective in preventing this injury in adolescent athletes. A number of techniques are currently in practice that address anterior cruciate ligament injuries in the skeletally immature, but there is no consensus on the optimal technique.

SUMMARY

The reported clinical outcomes from anterior cruciate ligament reconstruction in young patients are favorable.

Rotational and peak torque stiffness of rugby shoes

OBJECTIVE

Sports people always strive to avoid injury. Sports shoe designs in many sports have been shown to affect traction and injury rates. The aim of this study is to demonstrate the differing stiffness and torque in rugby boots that are designed for the same effect.

METHODS

Five different types of rugby shoes commonly worn by scrum forwards were laboratory tested for rotational stiffness and peak torque on a natural playing surface generating force patterns that would be consistent with a rugby scrum.

RESULTS

The overall internal rotation peak torque was 57.75±6.26 Nm while that of external rotation was 56.55±4.36 Nm. The Peak internal and external rotational stiffness were 0.696±0.1 and 0.708±0.06 Nm/deg respectively. Our results, when compared to rotational stiffness and peak torques of football shoes published in the literature, show that shoes worn by rugby players exert higher rotational and peak torque stiffness compared to football shoes when tested on the same natural surfaces. There was significant difference between the tested rugby shoes brands.

CONCLUSION

In our opinion, to maximize potential performance and lower the potential of non-contact injury, care should be taken in choosing boots with stiffness appropriate to the players main playing role.

Incidence and risk factors for turf toe injuries in intercollegiate football: data from the national collegiate athletic association injury surveillance system

BACKGROUND

Turf toe is the general term for a sprain of the first metatarsophalangeal (MTP) joint complex. Previously attributed to shoe design and artificial turf, the incidence of turf toe injury has been thought to decline with the advent of newer turf designs. However, the current incidence and epidemiology remain unknown as the majority of the literature consists of small series and addresses diagnosis and treatment rather than epidemiology and prevention.

METHODS

We examined data from the NCAA's Injury Surveillance System (ISS) for 5 football seasons (2004-2005 through 2008-2009), including all preseason, regular season, and postseason practice and competition data. The incidence, epidemiology, and risk factors for turf toe injury, defined as injury to the connective tissue of the first MTP joint, plantar plate complex, and/or sesamoid fracture, were determined.

RESULTS

The overall incidence of turf toe injuries in NCAA football players was 0.062 per 1000 athlete-exposures (A-Es; 95% CI 0.052, 0.072). Athletes were nearly 14 times more likely to sustain the injury during games compared to practice, with a mean days lost due to injury of 10.1 (7.9, 12.4). Fewer than 2% of turf toe injuries required operative intervention. There was a significantly higher injury rate on third-generation artificial surfaces compared to natural grass (0.087 per 1000 A-E [0.067, 0.11] vs 0.047 per 1000 A-E [0.036, 0.059]). The majority of injuries occurred as a result of contact with the playing surface (35.4%) or contact with another player (32.7%), and running backs and quarterbacks were the most common positions to suffer turf toe injury.

CONCLUSION

Our data suggest a significantly higher incidence of turf toe injuries during games, a greater susceptibility among running backs and quarterbacks, and a significant contribution of playing surface to risk of injury. Though turf toe injuries may be less common that previously reported in elite football players, these injuries warrant appropriate acute and long-term management to prevent long-term dysfunction.

LEVEL OF EVIDENCE

Level IV, case series.