Injuries in Field Hockey Players: A Systematic Review

Background To commence injury prevention efforts, it is necessary to understand the magnitude of the injury problem. No systematic reviews have yet investigated the extent of injuries in field hockey, despite the popularity of the sport worldwide. Objective Our objective was to describe the rate and severity of injuries in field hockey and investigate their characteristics. Methods We conducted electronic searches in PubMed, Embase, SPORTDiscus, and CINAHL. Prospective cohort studies were included if they were published in English in a peer-reviewed journal and observed all possible injuries sustained by field hockey players during the period of the study. Results The risk of bias score of the 22 studies included ranged from three to nine of a possible ten. In total, 12 studies (55%) reported injuries normalized by field hockey exposure. Injury rates ranged from 0.1 injuries (in school-aged players) to 90.9 injuries (in Africa Cup of Nations) per 1000 player-hours and from one injury (in high-school women) to 70 injuries (in under-21 age women) per 1000 player-sessions. Studies used different classifications for injury severity, but—within studies—injuries were included mostly in the less severe category. The lower limbs were most affected, and contusions/hematomas and abrasions were common types of injury. Contact injuries are common, but non-contact injuries are also a cause for concern. Conclusions Considerable heterogeneity meant it was not possible to draw conclusive findings on the extent of the rate and severity of injuries. Establishing the extent of sports injury is considered the first step towards prevention, so there is a need for a consensus on injury surveillance in field hockey. Electronic supplementary material The online version of this article (10.1007/s40279-017-0839-3) contains supplementary material, which is available to authorized users.


Introduction
Field hockey is an Olympic sport played by men and women at both recreational and professional levels. The five continental and 132 national associations that are members of the International Hockey Federation [1] demonstrate the high level of popularity of field hockey worldwide. Field hockey participation may contribute to players' health through the well-known benefits of regular exercise. However, participation in field hockey also entails a risk of injury [2].
In general, sports injuries result in individual and societal costs [3], hamper performance, and compromise a teams' success over the sporting season [4,5]. Therefore, injury prevention strategies are of great importance for teams at both recreational and professional levels. Establishing the extent of the injury problem is considered the first step towards effective prevention [6]. In field hockey, as well as in other sports, this information can aid researchers and health professionals in developing appropriate strategies to reduce and control injuries [6].
To the best of our knowledge, no systematic reviews have provided a synthesis of information on injuries sustained by field hockey players. Systematic reviews involve gathering evidence from different sources to enable a synthesis of what is currently known about a specific topic (e.g., injuries) and may facilitate the link between research evidence and optimal strategies for healthcare [7]. Therefore, the aim of this study was to systematically review the literature on injuries sustained by field hockey players, in order to describe the extent of such injuries in terms of rate and severity as well as to identify injury characteristics according to body location, type, and mechanism of injury.

Information Sources and Search Strategy
Electronic searches were conducted in PubMed, Exerpta Medical Database (Embase), SPORTDiscus, and Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases with no limits on the publication date. The search strategy combined keywords for injury, field hockey, and study design: ((((((((((((injur*) OR traum*) OR risk*) OR overuse) OR overload) OR acute) OR odds) OR incidence) OR prevalence) OR hazard)) AND (((field AND hockey)) OR (hockey NOT ice))) AND (((prosp*) OR retrosp*) OR case*). The detailed search strategy for each database can be found Appendix S1 in the Electronic Supplementary Material (ESM). The last search was conducted on 31 May 2017.

Eligibility Criteria
Studies were eligible for inclusion if they were published in the English language in a peer-reviewed academic journal, were prospective cohort studies, and observed all possible injuries sustained by field hockey players during the period of the study (i.e., studies that looked only at specific injuries were not included). To minimize the possibility of recall bias, only prospective cohort studies were included [8,9]. Studies were not included if they described field hockey injuries together with those from other sports, and specific data on field hockey could not be distinguished. Conference abstracts were not included.

Study Selection and Data Collection Process
Two reviewers (SDB and CJ) independently screened all records identified in the search strategy in two steps: title and abstract screening, and full-text screening. References of full texts were also screened for possible additional studies not identified in the four databases. Conflicts between reviewers' decisions were resolved through discussion. A third reviewer (EV) was consulted for consensus rating when needed.
One reviewer (SDB) extracted the following information from the included studies: first author, publication year, country in which the study was conducted, primary objective, setting, follow-up period, number and description of field hockey players, injury definition, injury data collection procedure, number of injured players, number of injuries sustained by players during the study, and severity of injuries (Table 1). The number of injuries normalized by exposure to field hockey (i.e., injury rate) was also extracted. In addition, information on injury according to body location, type of injury, mechanism, and player position was gathered whenever possible. When different studies used the same dataset (Table 1), the results of such studies were combined in one row in all other tables for simplicity.

Risk of Bias Assessment
Two independent reviewers (SDB and CJ) assessed the risk of bias in the included studies using ten criteria previously used in systematic reviews on sports injury [9,10]. All criteria were rated as 1 (i.e., low risk of bias) or 0 (i.e., high risk of bias). When insufficient information was presented in a study to rate a specific criterion as 1 or 0, the rating was categorized as 'unable to determine' (UD) and counted as 0. The assessment of each reviewer was compared, and conflicts were resolved through discussion. The ten criteria are described in Table 2. (2) any injury causing cessation of player's customary participation on the day following the day of onset; (3) any fracture, even though the athlete did not miss any regularly scheduled session; (4) any dental injury, including fillings, luxations, and fractures, 3 Results

Search Results
We retrieved 810 records from the four databases. Of those, 193 were duplicates. After screening 617 titles and abstracts and 21 full texts, ten studies matched the inclusion criteria. Screening the references of the full texts resulted in 12 additional records. In the end, 22 studies were included in the review. The flowchart of the inclusion process is presented in Fig. 1.
One study [24] was the follow-up of a previous study [23]. Six studies (27%) focused on describing field hockey injuries only [14,18,19,28,29,32]. The other 16 studies (73%) described the epidemiology of injuries in field hockey together with those in other sports [11-13, 15-17, 20-27, 30, 31]. The period of follow-up varied between studies from a 6-day championship tournament [20] to 15 consecutive seasons of field hockey [28]. The sample size varied between 26 [22] and 5385 participants [28]. Risk of bias: low = 1, high = 0. Unable to determine fields (UD) were counted as zero in the score 1 definition of injury clearly described; 2 prospective design that presents incidence or prevalence data; 3 description of field hockey players (e.g., recreational or professional level); 4 the process of inclusion of athletes in the study was at random (i.e., not by convenience) or the data collection was performed with the entire target population; 5 data analysis performed with at least 80% of the athletes included in the study; 6 injury data reported by players or by a healthcare professional; 7 same mode of injury data collection used; 8 injury diagnosis conducted by medical professional; 9 follow-up period of at least 6 months; 10 incidence or prevalence rates of injury expressed by a ratio that represents both the number of injuries as well as the exposure to field hockey (i.e., number of injuries/hours of field hockey exposure, or number of injuries/ sessions of field hockey exposure) However, seven studies (32%) did not report the number of field hockey players studied [11,13,14,19,21,25,27]. The definition of injury varied across the studies. Common criteria to define an injury as recordable were a musculoskeletal condition requiring medical attention and/ or leading to field hockey time loss (Table 1). The proportion (%) of injured players varied from 6% (in 7 months of high school) to 33% (in 6 days of university games). Twelve studies (55%) did not report the number or proportion of players who had sustained an injury over the study period [11-15, 18, 19, 25, 26, 28, 29, 32]. Table 2 shows the risk-of-bias assessment for the 22 included studies. The total score ranged from three to nine of a possible ten points. The studies published during and since 2000 scored higher (range 7-9) [23][24][25][26][27][28][29][30][31]. Three studies (14%) did not provide a clear definition of injury [11,15,18], and three did not describe any characteristics of the players studied [11,15,19]. These studies were published before the year 2000.
In the studies describing injuries according to players' time at risk, injury rates ranged from 0.1 injuries (in school-aged players) [12] to 90.9 injuries (in Africa Cup of Nations) [32] per 1000 player-hours of field hockey ( Table 3). The injury rate in the studies describing injuries according to players' sessions at risk varied from one injury (in high-school women) [13] to 70 injuries (in under-21 age women) [29] per 1000 player-sessions. The injury rates were higher in games than in training sessions in two [21,28] of the three studies that investigated this outcome [21,28,29]. In major tournaments, injury rates were higher in men [25,32]. Table 1 presents the classification of injuries according to severity. Most of the studies (55%) used field hockey time loss to report the severity of injuries [11,13,17,19,21,[25][26][27][28][29][30][31], but reported the days of time loss differently. Some studies reported the average days of time loss [11,17] and others used diverse cut-off points to report injury-related days of time loss, such as two days [19], eight days [21,27], and ten days [26,28]. The majority of injuries were in the less severe category in all studies reporting days of time loss due to injury, regardless of the cut-off points used [13,14,19,21,25,28,29,31]. Six studies (27%) included severity measures in the methodology but did not specify the number or proportion of injuries according to severity in the results [12,16,20,23,24,32]. Three studies (14%) did not mention severity of injury at all [15,18,22].

Discussion
To the best of our knowledge, the present study is the first systematic review to summarize the descriptive evidence of injuries sustained by field hockey players. We included only prospective studies to ensure we gathered the most reliable information available on the extent of injuries in field hockey in terms of rate and severity as well as injury characteristics according to body location, type, and mechanism of injury. To reduce and control field hockey injuries, as for all sports, we must first establish the extent of the injury problem [6]. The substantial heterogeneity between studies included in this review prevented conclusive findings on the extent of the rate and severity of injuries in field hockey (Tables 1, 2). Such heterogeneity may be caused by the different definitions and methods employed to record and report injuries and the different characteristics and levels of players studied.     Values represent percentages of injured players (i.e., not injuries) and do not add to 100% as some players sustained more than one injury c Same data as Hootman et al. 2007 [26] Injuries in Field Hockey 861  This systematic review shows that, despite the long history of field hockey and its popularity worldwide, prospective studies focusing on overall field hockey injuries are still lacking. The majority of the studies investigated field hockey injuries together with injuries in other sports [11-13, 15-17, 20-27, 30, 31]. Within such studies, injury rates in field hockey were comparable to those in other team sports, such as basketball [23,24,26], netball [23,24], lacrosse [26], and softball [21,27]. The injury rate in field hockey can be considered low compared with football (soccer) [21,[25][26][27]. However, in major tournaments, the rate of time loss injuries in field hockey [32] can be considered higher than that in football (soccer) [4]. These findings confirm that the risk of sustaining an injury in field hockey should not be neglected.
Despite the considerable heterogeneity between studies, it is still possible to observe similar characteristics of injuries with regard to body location, type, and mechanism of injury. Most of the injuries described in the studies included in this review were to the lower limbs (Table 4), affecting mainly the knee and the ankle. This is in line with previous studies on team sports involving running and stepping maneuvers, such as football (soccer) [33] and lacrosse [34], and justifies a focus on preventive efforts in this body area. Interestingly, the majority of injuries sustained by women during major tournaments were to the head [25,32]. A specific analysis of head injuries in collegiate women's field hockey showed that 48% of these injuries occurred due to contact with an elevated ball [35]. Most (39%) of the concussions were due to direct contact with another player, and 25% were due to contact with an elevated ball [35].
Contusions and hematomas were common types of injury, as were abrasions and lacerations, which might be due to players' contact with the ball, stick, and playing surface [2,28]. A specific analysis of ball-contact injuries in 11 collegiate sports showed that injury rates were the highest in women's softball, followed by women's field hockey and men's baseball [36]. In field hockey, the common activities associated with ball-contact injuries were defending, general play, and blocking shots [36]. To reduce the injury burden, the International Hockey Federation stated that goalkeepers must wear protective equipment comprising at least headgear, leg guards, and kickers [37]. Field players are recommended to use shin, ankle, and mouth protection [37], and other research suggested that the use of such equipment should be mandatory [2]. Accordingly, some national associations have updated their rules to make shin, ankle, and mouth protection obligatory [38,39].
It is important to note that non-contact injuries are also a cause for concern in field hockey ( Table 6). Although protective equipment has a fundamental role in injury prevention, it may not prevent most of the non-contact injuries. During the last decades, different studies have shown that it is possible to prevent injuries in team sports with structured exercise [40][41][42][43][44]. Yet, to our knowledge, evidence showing the implementation of such programs in field hockey is lacking. Nevertheless, exercise programs that have proven effective in preventing sports injury can be introduced as part of the regular training schedule of the field hockey team, especially programs focusing on the prevention of lower limb injuries [40][41][42]. While there is no structured exercise program for field hockey, stakeholders can also use open source resources for overall and specific injury prevention that are supported by the International Olympic Committee, such as exercise programs and guidelines on load management and youth athletic development [45][46][47].

Future Recommendations
The present systematic review shows that studies have used different definitions and methods to record and classify injuries and their severity, and this prevents conclusive findings on the extent of the injury problem in field hockey.
As establishing the extent of sports injury is considered the first step toward effective prevention [6], one of the main findings of this review is the recognition of the need for a consensus on the methodology of injury surveillance in field hockey. Consensus statements on the methodology of injury surveillance have been made available for a variety of sports [8,[48][49][50][51][52][53][54]. A consensus statement represents the result of a comprehensive collective analysis, evaluation, and opinion of a panel of experts regarding a specific subject (e.g., methodology of injury surveillance in field hockey) [55]. Consequently, consensus statements enable investigators from different settings to access and employ the same definitions and methods to collect and report injury data. Comparisons among different studies as well as data pooling for meta-analyses are then facilitated. The common goal in field hockey is to promote players' safety while maintaining the traditions of the sport [35]. Protecting the health of the athletes is also a priority of the International Olympic Committee [56], and resources for injury prevention have been made available for the public in general [45][46][47]. The field hockey community would benefit from studies investigating the implementation of such resources and from strategies that have been proven to be effective in other sports [40][41][42][43][44]. Until there is consensus on the methodology of injury surveillance in field hockey, investigators may use consensus from other team sports in future studies as an example [8,52,53]. Based on the gaps identified in the studies included in this review, the authors also suggest that future studies adhere to the reporting guidelines from the Enhancing the Quality and Transparency of Health Research (EQUATOR) Network. The EQUATOR Network provides comprehensive documentation on what information needs to be reported in scientific manuscripts depending on the study design [57]. By following an appropriate guideline such as that of the EQUATOR Network, future investigators will facilitate assessment of the generalizability, strengths, and limitations of studies on field hockey injuries.

Limitations
Electronic searches were conducted in four databases that were considered relevant for this systematic review. This does not rule out the possibility of eligible articles published in journals that were not indexed in any of these databases. To minimize this limitation, we screened the references of the full texts assessed for eligibility and included additional studies that were not identified in the database search. In addition, this systematic review included only scientific manuscripts published in English, although studies on field hockey injuries have been published in other languages. These were not included because the authors were unable to translate the papers accurately enough to extract their data.

Conclusion
The present systematic review shows that, despite the long history and the popularity of field hockey worldwide, few prospective studies have investigated the overall injury problem in field hockey. Most of the information on field hockey injuries registered prospectively comes from studies conducted in multi-sport settings. The range of definitions, methods, and reporting employed by studies prevents conclusive findings on the rate and severity of injuries in  [26] field hockey. To facilitate the development of evidencebased strategies for injury prevention, field hockey may benefit from a consensus on the methodology of injury surveillance. While no specific consensus is available for field hockey, future studies may use widely accepted consensus from other sports, such as football (soccer). In addition, future studies on field hockey injuries are encouraged to adhere to the reporting guidelines from the EQUATOR Network. Despite the considerable heterogeneity, it is clear that most of the injuries sustained by field hockey players affect the lower limbs, justifying efforts to develop preventive strategies for this body area. Contact injuries, such as contusions/hematomas, and abrasions, are frequent, and the use of protective equipment for the ankle, shin, hand, mouth, and eye/face has been recommended. Nevertheless, non-contact injuries are also common in field hockey, and most of these may not be prevented by protective gear. To reduce the burden of injuries, field hockey stakeholders may implement exercise-based injury-prevention programs and guidelines on load management and youth athletic development that have been supported by the International Olympic Committee.