a b s t r a c t

Background: Softball is a popular participant sport in the United States. This study investigated the epidemiology of softball injuries with comparisons between children and adults.

Methods: Data from the National Electronic Injury surveillance System for patients 7 years and older treated in an emergency department (ED) for a softball injury from 1994 through 2010 were analyzed.

Results: An estimated 2107823 (95% confidence interval [CI], 1736417-2479229) patients were treated in US EDs for a softball injury during the 17-year study period. The annual number of injuries decreased by 23.0% from 1994 to 2010 (P b .001); however, during the last 6 years of the study, injuries increased by 11.7% (P = .008). The annual rate of softball injuries increased significantly during the study period (P = .035). The most commonly injured body regions were the hand/wrist (22.2%) and face (19.3%). Being hit by a ball was the most common mechanism of injury (52.4%) and accounted for most of face (89.6%) and head (75.7%) injuries. Injuries associated with running (relative risk, 2.36; 95% CI, 1.97-2.82) and diving for a ball (relative risk, 4.61; 95% CI, 3.50-6.09) were more likely to occur among adult than pediatric patients.

Conclusions: To our knowledge, this is the first study to investigate softball injuries using a nationally Representative sample. Softball is a common source of injury among children and adults. Increased efforts are needed to promote safety measures, such as face guards, mouth guards, safety softballs, and break-away bases, to decrease these injuries.

(C) 2013

Introduction

Softball is one of the most popular participant sports in the United States. Between competitive league and recreational adult and adolescent play, an estimated 14 million [1] to 40 million [2] people play softball annually. Organized softball leagues have grown in popularity. Over the last 3 decades, the membership and number of registered teams among all ages have at least doubled [3].

? Conflicts of interest and sources of support: The authors have no conflicts of interest or financial disclosures relevant to this article to declare. John C. Birchak received a student research scholarship from the Medical Student Research Scholarship Fund of The Ohio State University College of Medicine while he worked on this study.

?? Disclaimer: The interpretations and conclusions in this article are those of the

authors and do not necessarily represent the official position of the US Department of the Army.

* Corresponding author. Center for Injury Research and Policy, The Research Institute at Nationwide Children’s Hospital, Columbus, OH 43205. Tel.: +1 614 355

5850; fax: +1 614 355 5897.

E-mail address: [email protected] (G.A. Smith).

Among high school athletes, softball was responsible for 27% more injuries than baseball [4], and girls softball had a higher injury rate than boys baseball (14.4 vs 11.8 per 100 players) [5]. Among adults, softball was the fifth most likely activity to account for lost-workday injuries among Air Force personnel, second in terms of sports only to basketball [6]. In addition, shoulder, knee, and hand/wrist dislocation injuries are nearly twice as likely for high school softball players than baseball players [7]. As with most sports, softball injuries may be classified into 2 categories. Overuse injuries occur from repetitive use of muscles and ligaments in physically exerting motions, usually in the context of pitching and throwing [8,9]. acute injuries refer to sudden trauma, usually from collision with another player, the ground, or a moving ball. Previous research on softball injuries has mostly focused on specific age groups [6,10,11], body region of injury [12], or injury as it pertains to certain player positions [10,13]. Although national studies have characterized injuries for other sports [14-17], there is no nationally representative study that describes the epidemiology of softball injuries. Therefore, the purpose of this study is to investigate the characteristics of softball injuries among all players seeking treatment in US hospital emergency departments (EDs) using a

nationally representative sample.

0735-6757/$ - see front matter (C) 2013 http://dx.doi.org/10.1016/j.ajem.2013.02.039

Methods

Data source

The US Consumer Product Safety Commission operates the National Electronic Injury Surveillance System , which contains information regarding sports and recreational activity and consumer product-related injuries treated in US EDs. The NEISS pools data from approximately 100 hospitals, which represent a stratified probability sample of more than 5000 US hospitals with a 24-hour ED with at least 6 beds [18]. At each participating hospital, an NEISS coder records data concerning each in-scope ED patient visit into the database. Data include age, sex, injured body region, diagnosis, product or Sport activity involved, disposition from the ED, and a brief narrative describing the circumstances of the injury.

The NEISS database was examined for all ED visits involving softball injuries (NEISS code 5034) among patients 7 years and older from 1994 through 2010. The search produced 50950 unweighted cases. The narrative for each case was examined to ascertain relevance, and 246 cases involving injuries sustained to coaches, umpires, and spectators or injuries unrelated to game play, such as bites from team mascots, were excluded. Injuries resulting from playing catch or batting practice were included in the study because these are ways of training for the sport. Previous research has demonstrated that NEISS data extraction is accurate and sensitive for capturing product-related injuries treated in US EDs when compared with the original medical record [19-21]. When the mechanism of injury was described in this study, case narratives provided an unambiguous description for the mechanism; all cases were reviewed by the same study researcher for classification.

Variables

The mechanism of injury was grouped into 14 categories: (1) hit by a ball; (2) sliding into base; (3) unintentional falls; (4) player- player collision; (5) sliding with player-player collision; (6) running;

(7) catching; (8) throwing; (9) diving for a ball; (10) batting; (11) collision with fixed objects, such as a fence; (12) hit by the bat; (13) cleat-induced; and (14) other, including heat exhaustion. For injuries associated with being hit by a ball, the contact was described as occurring from a batted, thrown, or pitched ball. Injuries associated with sliding with player-player collision were coded for the person injured: the slider vs the player guarding the plate. The term game play was used to collectively refer to mechanisms that involve proper play of the game, specifically, diving for a ball, running, catching, throwing, and batting; although a part of proper play, sliding into a base was not included because the injury involved contact with an object and was, therefore, inherently different.

The NEISS categories for injured body region were condensed into 9 groups: (1) head; (2) face, including mouth, eye, and ear; (3) trunk/ neck, including pubic region; (4) hand/wrist, including fingers; (5) arm, including upper arm, elbow, and forearm; (6) foot/ankle, including toes; (7) leg, including the upper leg, knee, and lower leg;

(8) shoulder; and (9) other, including more than 25% of the body, aspiration/ingestion, and burns. injury diagnosis was collapsed into 7 broader categories: (1) concussion/closed head injury (CHI), including concussions and internal injuries to the head; (2) soft tissue injury; (3) fracture/dislocation; (4) laceration; (5) Dental injury; (6) strain/ sprain; and (7) other. Disposition from the ED was categorized as (1) treated and released, including leaving against medical advice and (2) admitted, including hospital transfers and being held for observation. Eight fatal injuries were excluded from the study: 6 cardio/pulmonary arrest cases, 1 Commotio cordis case, and 1 instance of being struck by lightning. Location of injury was condensed into: (1) home; (2) school;

(3) sport/recreation facility; and (4) other, including streets and other

public property. Children were defined as patients 7 to 17 years of age, and adults included patients 18 years or older.

Data analysis

Data were analyzed using IBM SPSS Statistics 19 (SPSS, an IBM Company Inc, Armonk, NY), Epi Info 6 (USD, Stone Mountain, GA), and SAS version 9.3 (SAS Institute, Cary, NC). Statistical weights provided by the Consumer Product Safety Commission were used to calculate national Injury estimates; all values presented in this article are weighted national estimates unless otherwise stated. Statistical analyses included ?² tests and calculation of Relative risks (RRs) with 95% confidence intervals (CIs); weighted Linear regression analysis of the annual injury number and rate was used to test for trends. The US Census Bureau obtains recreational exposure data for softball participation from the National Sporting Goods Association [1]. These data are based on 10000 to 15000 households surveyed annually, with a participant defined as an individual 7 years or older, who played softball more than once during the year. Annual exposure data were used to calculate injury rates; data were not available beyond 2009; therefore, 2010 injury rates were not calculated.

Results

Demographic features and injury trends

From 1994 through 2010, an estimated 2 107 823 (95% CI, 1736417-2479229) patients 7 years and older were treated in US EDs for an injury sustained while playing softball, with an average of 123990 injuries annually or 1 person every 4 minutes. Children sustained 771575 (95% CI, 627164-915986) injuries (8.44 per 1000

players), and 1336248 (95% CI, 1095947-1576548) were sustained

by adults (8.86 per 1000 players). Ages ranged from 7 to 96 years

(Fig. 1), with an average age of 24.9 (95% CI, 24.4, 25.4) years

(children: mean, 13.5 [95% CI, 13.4-13.6] years; adults: mean, 31.5 [95% CI, 31.1-32.0] years). Most softball injuries occurred to females (52.8%), and injury rates were greater for females (9.56 per 1000 female players) than for males (7.93 per 1000 male players). Among children, females accounted for 86.3% of all ED visits, but among adults, they were responsible for only 33.5% of visits. Of the 1517046 cases (72.0%) where location of injury was documented, 81.2% of injuries occurred at a sports/recreation place, 9.8% occurred at school, and 5.7% occurred at home. Emergency department visits from April through July, which overlap with most softball seasons, accounted for 66.1% of injuries.

Among all ages, the annual number of softball injuries significantly decreased by 23.0% from 153034 cases in 1994 to 117818 cases in

2010 (m = -2278.0, P b .001, Fig. 2); however, injuries significantly

increased by 11.7% between 2005 (105515 cases) and 2010 (m = 2671.2, P = .008). The annual number of injuries among adults significantly decreased from 1994 through 2010 (m = -2360.1, P b

.001); however, there was no significant change for children (m = 80.0, P = .657). Among all ages, annual injury rates per 1000 players significantly increased from 1994 to 2009 (m = 0.115, P = .035). Annual injury rates per 1000 players for adults showed no significant change from 1994 through 2009 (m = -0.018, P = .762); however, injury rates among children significantly increased (m = 0.342, P b

.001). Although the injury rate for children in 2007 was almost 3 SDs from the mean, the increasing secular trend in annual injury rates among children remained significant even with the exclusion of this extreme value (m = 0.291, P b .001).

Body region and diagnosis

The most commonly injured body region was the hand/wrist (22.2%), with fingers predominating. Overall, Finger injuries

Fig. 1. Number of softball injuries treated in hospital EDs by age and sex, United States, 1994-2010.

accounted for 12.6% of all softball injuries. Hand/wrist injuries were largely fractures/dislocations (40.2%), strains/sprains (26.5%), and soft tissue injuries (24.6%). Face injuries comprised 19.3% of injuries and were mostly lacerations (38.5%), soft tissue injuries (32.8%), and fractures/dislocations (22.2%). A large portion of injuries occurred to the leg (17.5%) and foot/ankle (17.0%). Leg injuries mostly involved the knee, which accounted for 10.0% of all softball injuries. Adult patients were more likely to experience leg injuries than children (RR, 1.61; 95% CI, 1.49-1.74). Fig. 3 displays the distribution of injuries by body region among children and adults.

Head injuries accounted for 6.0% of all softball injuries, with almost two-thirds (64.8%) being concussions/CHIs. Pediatric patients were more likely to have concussions/CHIs than adults (RR, 1.38; 95% CI, 1.22-1.57), and female patients were more likely to experience a concussion/CHI than males (RR, 1.38; 95% CI, 1.23-1.55). Shoulder injuries comprised 6.0% of softball injuries and were mostly strains/ sprains (41.6%) or fractures/dislocations (30.1%). Male patients were more likely to have a Shoulder injury than females (RR, 2.15; 95% CI, 1.95-2.38).

The 2 most common softball injury diagnoses were strains/sprains (31.3%) and soft tissue injuries (27.0%). The foot/ankle was the most common body region diagnosed with a strain/sprain (36.9%). Dental injuries made up a small percentage (0.5%) of all softball injuries and were more likely to occur to female patients (RR, 1.46; 95% CI, 1.08- 1.98) than males. Male patients were more likely to experience lacerations (RR, 1.65; 95% CI, 1.52-1.80) and fractures/dislocations

(RR, 1.32; 95% CI, 1.26-1.38) than females.

Mechanism of injury

The mechanism of injury was described for 1365949 cases (64.8%) (Table). Among these cases, being hit by a ball accounted for 52.4% of injuries. Among the 113692 patients, who were hit by a ball and for whom it was documented how the contact occurred, most sustained injuries from batted balls (53.0%), followed by thrown (25.3%) and pitched (21.7%) balls.

Being hit by a ball accounted for 89.6% of face injuries, 75.7% of head injuries, and 94.7% of dental injuries; hence, being hit by a ball

Fig. 2. Annual number and rate of softball injuries among children and adults, United States, 1994-2010.

Fig. 3. Softball injury by body region among children and adults, United States, 1994-2010.

was 7.83 (95% CI, 7.19-8.54) times more likely to affect the face and

2.82 (95% CI, 2.47-3.22) times more likely to affect the head than other mechanisms of injury. Being hit by a ball accounted for most soft tissue injuries (72.2%), making it 2.36 (95% CI, 2.24-2.48) times more likely to cause soft tissue injury than other mechanisms. In addition, pediatric patients were at greater risk for being hit by a ball than adults (RR, 1.16; 95% CI, 1.13-1.20). Being hit by a bat accounted for only 1.8% of all softball injuries and was more likely

to occur among pediatric patients than adults (RR, 2.50; 95% CI, 2.02-3.09).

The most common body region injured by sliding into a base was the foot/ankle (40.0%), followed by the leg (27.1%) and hand/wrist (16.4%). Sliding into base was more likely to result in sprains/strains (RR, 2.54; 95% CI, 2.38-2.71) and fractures/dislocations (RR, 1.35; 95% CI, 1.29- 1.41) than other mechanisms of injury. Most strains/sprains were caused either by game play (28.9%) or sliding into a base (25.9%).

Table

Mechanism of injury for softball injuries among children and adults, United States, 1994-2010

Mechanism of injury Age 7-17 y Age >=18 y Total

Actual no. of cases

National estimate

95% CI %^a Actual no. of cases

National estimate

95% CI %^a Actual no. cases

National estimate

95% CI %^a

Hit by a ball	7643	305200	(248031-362370)	57.3	9332	410254	(331611-488898)	49.2	16975	715455	(584598-846312)	52.4
Sliding into base	1656	66780	(53672-79887)	12.5	2365	98850	(79468-118233)	11.9	4021	165630	(134986-196274)	12.1
Unintentional falls	1087	42969	(34590-51348)	8.1	2435	103786	(84259-123313)	12.5	3522	146755	(120113-173396)	10.7
Player-player collision	909	35602	(27898-43305)	6.7	1423	58657	(46354-70960)	7.0	2332	94258	(75519-112998)	6.9
Running	295	11169	(8191-14148)	2.1	1042	41202	(31097-51307)	4.9	1337	52371	(40256-64487)	3.8
Catching	395	16238	(12305-20170)	3.0	503	20224	(15686-24761)	2.4	898	36461	(28764-44159)	2.7
Throwing	290	12281	(9612-14950)	2.3	406	17654	(13633-21676)	2.1	696	29936	(23988-35883)	2.2
Hit by a bat	373	15329	(11801-18856)	2.9	218	9591	(7133-12050)	1.2	591	24920	(19546-30293)	1.8
Diving for a ball	74	2719	(1818-3620)	0.5	460	19616	(14754-24479)	2.4	534	22336	(16906-27766)	1.6
Collision with a fixed	108	3895	(2861-4928)	0.7	404	17497	(13291-21704)	2.1	512	21392	(16659-26125)	1.6
object
Batting	88	3503	(2368-4638)	0.7	208	9074	(6942-11206)	1.1	296	12577	(9726-15428)	0.9
Sliding with	150	5246	(3605-6888)	1.0	156	6404	(4555-8253)	0.8	306	11650	(8554-14746)	0.9
player-player collision Cleat-induced	46	1976	(1269-2683)	0.4	79	2921	(2048-3793)	0.4	125	4897	(3701-6094)	0.4
Other	259	9914	(7407-12422)	1.9	413	17397	(13587-21206)	2.1	672	27311	(21593-33029)	2.0
Unknown	5943	238754	(184330-293178)		11936	503120	(402303-603937)		17879	741874	(589930-893819)

^a Percent national estimate of known mechanisms of injury; percentages may not total to 100.0% due to rounding error.

Strains/sprains were more likely to be associated with game play (RR, 3.20; 95% CI, 2.99-3.42) than other injury mechanisms. Among patients with an injury attributable to sliding with player-player collision, 49.1% were the slider, and 50.9% were guarding the base.

Game play injuries accounted for a greater proportion of softball injuries among adult patients than pediatric patients (RR, 1.50; 95% CI, 1.38-1.64). More specifically, adult patients were more likely to experience an injury associated with running (RR, 2.36; 95% CI, 1.97- 2.82), diving for a ball (RR, 4.61; 95% CI, 3.50-6.09), and batting (RR, 1.66; 95% CI, 1.24-2.21) than children. Shoulder injuries were largely the result of game play (33.9%) and unintentional falls (31.2%). Adult patients were more likely to experience injuries resulting from unintentional falls (RR, 1.54; 95% CI, 1.42-1.69) and collisions with fixed objects (RR, 2.87; 95% CI, 2.19-3.77) than children. Among adult patients, males were more likely to sustain injuries associated with sliding into base (RR, 1.45; 95% CI, 1.32-1.59) and game play (RR, 1.35; 95% CI, 1.20-1.50) than females, whereas females were more likely to be hit by a ball (RR, 1.31; 95% CI, 1.26-1.36) than males.

Discussion

To our knowledge, this is the first study of softball injuries among the US population using a nationally representative sample. Since 1994, the annual number of softball-related ED visits among all ages decreased significantly by 23%. Patient visits dropped from 1994 to their lowest in 2005 and then increased through 2010. The rate of softball injury significantly increased over the study period. The injury trends for children and adults differed. Adult injuries decreased in number, but not rate, over the study period. The annual number of Pediatric injuries was stable over the study period, but there was a significant increase in the pediatric injury rate. These age group- specific secular trends are probably due to variation in the popularity of softball, combined with the institution of safety measures during organized play and possible changes in emergency care-seeking behavior following an injury; these factors also may have contributed to the overall decreasing trend in the number of ED visits followed by the increase during recent years. Injury rates among all ages were higher for females than for males, which is a finding consistent with past research [4,22].

The strong relationship between being hit by a ball and sustaining a facial injury may be due, in part, to failed attempts at catching softballs but may also be amplified by increased care-seeking behavior when the face is affected for cosmetic reasons. Although most studies demonstrating the benefit of protective equipment in batting sports have been done for baseball, it is reasonable to assume that this protective equipment would provide similar protection to softball players. Helmets with faceguards for high-risk positions, such as the batter and base runners, have been shown to reduce the risk of oculofacial injuries among baseball players [23]. Similarly, protective polycarbonate eyewear has been recommended to decrease the risk of eye injury [24]. This option has advantages for the higher risk infield positions [25] because it would be less cumbersome than a faceguard but still afford eye protection. Although the current study was unable to determine whether face shields were worn based on case narratives, the large number of face injuries suggests that this preventive measure should be used more consistently. Despite dental injuries comprising a small proportion of softball injuries (0.5%) in this study, mouth guard usage by players should be encouraged to decrease the severity of dental trauma, especially among infielders. Not only are mouth guards inexpensive, but they have been shown to decrease mouth injuries, including lacerations and tooth avulsions [26].

Because more than half of softball injuries were associated with

being hit by a ball, it seems prudent that safety softballs be used by children, inexperienced players, and during practice and informal softball games among all age groups. These balls are softer and produce less force upon impact. The use of softer balls is endorsed for

youth leagues by the American Academy of Orthopedic surgeons as a means to reduce injury [27], and the Amateur Softball Association of America also recommends that a softer ball, safety ball, or lower coefficient of restitution and compression softball be considered for inexperienced children or in coed adult games with players with disparate softball skills [28].

Sliding into a base was the second most frequent cause of injury in this study and was more likely to result in strains/sprains and fractures than other injury mechanisms. A slide is a complex athletic motion with a large opportunity for error, particularly for inexperi- enced players [29]. Traditional fixed bases are poorly designed to accommodate players just learning how to slide. Typically anchored in concrete, ordinary bases are immobile, whereas bases that detach upon impact have been shown to decrease the occurrence of injuries [30,31]. According to the American Academy of orthopedic surgeons, break-away or detachable bases have been demonstrated to increase the safety of the game without interfering with game play [32]. We, therefore, endorse the use of break-away bases in softball among all age groups.

Limitations

This study has several limitations. More than one-third of injury mechanisms could not be ascertained because of insufficient information in case narratives, which is a potential source of bias. The NEISS underestimates the number of softball injuries because some injuries are treated in non-ED settings, such as urgent care centers, private physician offices, or by athletic trainers. Injuries included in the NEISS also may not be representative of all softball injuries. In addition, valuable information on player position or whether the injury occurred during a game or practice could not be determined from case narratives.

We used recreational exposure data from the US Census Bureau to calculate injury rates. To our knowledge, these data are the most accurate data available for calculating softball injury rates for the US population. However, these participation numbers are based on self- report, and rates calculated in this study did not account for variability within the sample survey.

Conclusions

To our knowledge, this is the first study to investigate softball injuries among the US population using a nationally representative sample. Although the annual number of softball injuries decreased during the first 11 years of the study period, there was an increase between 2005 and 2010. In addition, the annual rate of softball injury increased significantly during the study period. Therefore, increased efforts are needed to promote safety measures, such as faceguards, mouth guards, safety softballs, and break-away bases, to decrease softball injuries.

Acknowledgments

We thank Natalie McIlvain for her helpful comments and suggestions. The authors also gratefully acknowledge support from the Medical Student Research Scholarship Fund of The Ohio State University College of Medicine, which provided a student research stipend for author JCB, while he worked on this study. Interpretations and conclusions expressed in this article do not necessarily represent those of the funding institution.

References

1. The 2012 Statistical Abstract. US Census Bureau. 2012. http://www.census.gov/ compendia/statab/2012edition.html (Accessed December 29, 2012) http://www.

   census.gov/compendia/statab/past_years.html (Accessed December 29, 2012).

   Janda DH, Wild DE, Hensinger RN. Softball injuries. Aetiology and prevention. Sports Med 1992;13(4):285-91.

2. Flynn M. Softball slides into the 21st century - growth in popularity of softball in schools. Parks and Recreation 1995;30(4):36-42.
3. Powell JW, Barber-Foss KD. Sex-related injury patterns among selected high school sports. Am J Sports Med 2000;28(3):385-91.
4. Powell JW, Barber-Foss KD. Injury patterns in selected high school sports: a review of the 1995-1997 seasons. J Athl Train 1999;34(3):277-84.
5. Burnham BR, Copley GB, Shim MJ, Kemp PA, Jones BH. Mechanisms of slow-pitch softball injuries reported to the HQ Air Force Safety Center: a 10-year descriptive study, 1993-2002. Am J Prev Med 2010;38(1 S):S126-33.
6. Kerr ZY, Collins CL, Pommering TL, Fields SK, Comstock RD. Dislocation/separation injuries among US high school athletes in 9 selected sports: 2005-2009. Clin J Sport Med 2011;21(2):101-8.
7. Dyle FM. Review of the windmill pitch: biomechanics and injuries. J Chir Med 2004;3(2):53-62.
8. Park SS, Loebenberg ML, Rokito AS, Zuckerman JD. The shoulder in baseball pitching biomechanics and related injuries-part 1. Bull Hosp Jt Dis 2002;61(1-2):68-79.
9. Krajnik S, Fogarty KJ, Yard EE, Comstock RD. Shoulder injuries in US high school baseball and softball athletes, 2005-2008. Pediatrics 2010;125(3):497-501.
10. Hosey RG, Puffer JC. Baseball and softball sliding injuries incidence, and the effect of technique in collegiate baseball and softball players. Am J Sports Med 2000;28(3):360-3.
11. Fernandez WG, Yard EE, Comstock RD. Epidemiology of lower extremity injuries among U.S. high school athletes. Acad Emerg Med 2007;14(7):641-5.
12. Werner SL, Jones DG, Guido JA, Bruent ME. Kinematics and kinetics of elite windmill softball pitching. Am J Sports Med 2006;34(4):597-603.
13. Lawson BR, Comstock RD, Smith GA. Baseball-related injuries to children treated in hospital emergency departments in the United States, 1994-2006. Pediatrics 2009;123(6):e1028-34.
14. Singh S, Smith GA, Fields SK, McKenzie LB. Gymnastics-related injuries to children treated in emergency departments in the United States, 1990-2005. Pediatrics 2008;121(4):e954-60.
15. Shields BJ, Smith GA. Cheerleading-related injuries to children 5 to 18 years of age:

    United States, 1990-2002. Pediatrics 2006;117(1):122-9.

    Potter MR, Snyder AJ, Smith GA. Boxing injuries presenting to U.S. emergency departments, 1990-2008. Am J Prev Med 2011;40(4):462-7.

16. US Consumer Product Safety Commission Division of Hazard and Injury Data Systems. NEISS: The National Electronic Injury Surveillance System: A Tool for

    Researchers. US Consumer Product Safety Commission. http://www.cpsc.gov/ neiss/2000d015.pdf; 2000. (Accessed December 27, 2011).

    Hopkins RS. Consumer product-related injuries in Athens, Ohio, 1980-1985: assessment of emergency room-based surveillance. Am J Prev Med 1989;5: 104-12.

17. Annest JL, Mercy JA, Gibson DR, Ryan GW. National estimates of nonfatal firearm- related injuries: beyond the tip of the iceberg. JAMA 1995;273:1749-54.
18. Davis Y, Annest JL, Powell KE, Mercy JA. An evaluation of the National Electronic Injury Surveillance System for use in monitoring nonfatal firearm injuries and obtaining national estimates. J Safety Res 1996;27:83-91.
19. Ingram JG, Fields SK, Yard EE, Comstock RD. Epidemiology of knee injuries among boys and girls in US high school athletes. Am J Sports Med 2008;36(6):1116-22.
20. Danis RP, Hu K, Bell M. Acceptability of baseball face guards and reduction of oculofacial injury in receptive youth league players. Inj Prev 2000;6(3):232-4.
21. Rodriguez JO, Lavina AM, Agarwal A. Prevention and treatment of common eye injuries in sports. Am Fam Physician 2003;67(7):1481-8.
22. Collins CL, Comstock RD. Epidemiological features of high school baseball injuries in the United States, 2005-2007. Pediatrics 2008;121(6):1181-7.
23. Diab N, Mourino AP. Parental attitudes toward mouthguards. Pediatr Dent 1997;19(8):455-60.
24. American Academy of Orthopaedic Surgeons. Baseball Injury Prevention. American Academy of Orthopaedic Surgeons. http://orthoinfo.org/topic.cfm? topic=A00185; 2011. (Accessed December 27, 2011).
25. Amateur Softball Association of America. Safety Awareness Guide. Amateur Softball Association of America. http://www.usasoftball.com/uploads/ Softball_Safety_Awareness_Guide_Final.pdf; 2011. (Accessed December 27,

    2011).

    Baseball Excellence. Sliding into Bases. Baseball Excellence. http://www.baseball- excellence.com/index.cfm?Method=Instructions_Instructionsdetail&id=45; 2011. (Accessed December 27, 2011).

26. Janda DH. The prevention of baseball and softball injuries. Clin Orthop Relat Res 2003;409:20-8.
27. Janda DH, Bir C, Kedroske B. A comparison of standard vs. breakaway bases: an analysis of a preventative intervention for softball and baseball Foot and ankle injuries. Foot Ankle Int 2001;22(10):810-6.
28. American Academy of Orthopaedic Surgeons. Position Statement: Use of Breakaway Bases in Preventing Recreational Baseball and Softball Injuries. Am Acad Orthop Surg 2010. http://www.aaos.org/about/papers/position/1140.asp. (Accessed December 27, 2011).