1. Introduction

Polytrauma is a term used to describe injuries the involve multiple parts of the body or body cavity and as a result, other physiological processes or bodily organs may also be compromised, despite not being involved in the initial injuries. Since the 1980s, the treatment of polytrauma has became an integrated treatment model in which multidisciplinary teams are responsible for polytrauma with the rapid development of trauma treatment systems and damage control technologies, such as emergency resuscitation, emergency surgery, Intensive Care Unit (ICU) treatment, and definitive surgery. However, the definition of polytrauma has been debated for a long time, which has led to difficulties in multi-centre research, academic exchanges, treatment systems, and technical level evaluation. Baker [1] proposed that the injury severity score (ISS) can be used to describe the severity of polytrauma in 1974. In 1975, Border et al. [2] defined polytrauma as wounds at more than two sites. In 1978, Schweiberer [3] divided polytrauma into three levels: grade I covers moderate injuries which require hospitalisation; grade II covers severe injury with shock and a loss of 25% of blood volume; and grade III covers emergency and life-threatening injuries with severe shock and loss of about 50% of blood volume. Ertel and Trentz [4] thought that polytrauma could be defined as multiple lesions with ISS ≥ 16, coupled with secondary systemic reactions which can cause distant organ dysfunction. In 2002, Osterwalder [5] proposed the basis for the modern definition of polytrauma: two or more sites were injured in six sites of ISS with abbreviated injury scale (AIS) ≥2. Keel [6] described polytrauma in 2006, as a combination of injuries where ISS > 17 points and SIRS for at least one day. In 2009, Butcher and Balogh [3] pointed out that there was still no consensus on the definition of polytrauma that could be supported by high-level evidence.

To date, there are still many different views on the definition of polytrauma. The purpose of this study is to collect the articles about polytrauma definitions from the past decade, so that the evolution and trends in application of different definitions can be investigated.

2. Methods

3. Results

3.2 The definition of polytrauma

Based on different definitions of polytrauma, the selected articles were grouped into four categories: (1) definition of polytrauma based on ISS score (277 articles), (2) definition of polytrauma based on the new injury severity score (NISS, 18 articles), (3) definition of polytrauma based on AIS (16 articles), and (4) descriptive definition of polytrauma (10 articles). The ISS definition was the most common, being used in 86% of the articles. Conversely, the descriptive definition of polytrauma was the least common, used in only 3% of the studies (Fig. 1).

Fig. 1.The number of articles in different groups.

3.3 Publication year

The selected 321 articles were published between 2008 and 2018, with more studies published in 2018 than any other year (n = 49), whilst the lowest number of studies were published in 2008 (n = 15). As time goes on, the number of articles published increased, as shown in Fig. 2. From 2008 to 2012, a total of 106 articles were published, including 88 in the ISS group, 10 in the NISS group, 5 in the AIS group, and 3 in the descriptive definition group. A total of 215 articles were published between 2013 and 2018, including 189 in the ISS group, 8 in the NISS group, 11 in the AIS group, and 7 in the descriptive definition group (Table 1). The numbers of published articles in the first five years and the second five years were compared between the four groups and there were no statistically significant differences (P > 0.05).

Fig. 2.The number of articles is published in different years.

Table 1.The number of published articles in the first five years and the next five years.

Yeas	ISS	NISS	AIS	Descriptive definition	Total
2008-2012	88	10	5	3	106
2013-2018	189	8	11	7	215
χ2	3.497
P	0.321

4. Discussion

The polytrauma definition based on ISS score was still the most widely used in the past decade. However, different articles had different understanding of the ISS definition, which was reflected in the different ISS thresholds (ISS > 15 [7], ISS > 16 [8, 9, 10], ISS > 18 [11], ISS ≥ 18 [12], or ISS > 25 [13]) and the decision to include anatomical sites or not. The most common definition of ISS-defined polytrauma was based on ISS of ≥ 16. At the same time, there were a small number of ISS definitions that required the injury sites to be greater than or equal to 2. The second largest group was the NISS group, of which the most common definition of polytrauma was when NISS > 15. The third was the AIS group, and in this case, polytrauma was mostly defined by AIS > 2, with at least two injury sites. The least common definition was the purely descriptive definition. In general, over the past 10 years, the most widely used definition of polytrauma in clinical research was ISS-based.

In terms of the year publication, the number of articles published in 2018 was the largest, and the number published in 2008 was the least. We found that the number of research articles on the definition of polytrauma has shown an increasing trend in the last ten years. This shows that more and more research and resources are being devoted to polytrauma. It also reflects the importance and urgency of defining the definition of polytrauma. The author compared the number of publications in the first five years and last five years and found that there was no significant difference in the application of the definition of polytrauma with the four groups. This shows there was no significant change in the application of multiple trauma definitions in the past decade, so there is still a long way to go for the application and promotion of a new definition.

The jounals that had published articles on polytrauma during the ten years were mainly from Europe and America. Injury as a well-known, authoritative journal in the traumatic world and is the journal that published the highest proportion of the selected articles. From its report on polytrauma, we can find that this is still a very popular research direction. According to journal impact factor, we divided the journals of the selected articles into two grades: impact factors of 0-6, and impact factors of > 6. We found that the proportion of articles from the AIS and NISS groups that were published in the high impact factor journals was significantly higher than that of the articles in the ISS group. We suspect that this may be related to the better prediction of mortality and morbidity by the AIS group and the NISS group [3, 14, 15]. Of all the journals where the selected articles were published, JAMA has the highest impact factor, followed by Intensive Care Medicine. This shows that the research into polytrauma has also been recognised by world-leading medical journals.

Similar to the journals, the authors were also largely from Europe and the United States. This shows that the European and American scholars are the mainstay in the field of multi-injury research. Germany, Switzerland, and the United States were the top three countries in terms of the number of articles published. Germany and Switzerland were close to each other, and there was extensive cooperation in their trauma research. The AO organisation was born in Switzerland. Here, there was very in-depth research into pre-hospital emergency care, hospitalisation, and postoperative rehabilitation. It is worth mentioning that there were also quite a number of articles published in China in the past decade. There were two main reasons for this. Firstly, with the development of the economy, the car ownership rate in China increased, which led to a large increase in accidents and injuries [16]. Secondly, the focus on polytrauma research increased, resulting in rising amounts of data being obtained [17].

Large-sample, multi-centred research was largely focused on the European region, particularly Germany and Switzerland. The Trauma Register DGU in Germany, established in 1993, was the most widely used. The aim of this multi-centre database is to anonymise and standardise the documentation of severely injured patients. It is a European multi-centre cooperative organisation, with prospective, standardised, and anonymous documentation of severely injured patients from more than 145 trauma centres. In other parts of the world, especially in Asia, Africa and South America, there was a lack of large sample databases, so their multiple-injury studies were often limited to research in single-centre settings. The authors believe that it is imperative to promote the establishment of a worldwide database of polytrauma, as it is crucial for the advancement of polytrauma research.

The first step for developing a large-scale database is to harmonise the definition of polytrauma. However, there was no significant change in the application of the definitions of polytrauma in the past decade, and the various definitions remain mixed. In 2017, C.S. Rau [18] applied a new definition of multiple trauma in their clinical reseach. This definition was called the “New Berlin Definition” and was first proposed in 2014 by Pape et al. [19]. Using this definition, polytrauma is defined as two injuries that score ≥ 3 on the AIS, coupled with and one or more additional diagnoses of hypotension (systolic blood pressure #8804; 90 mm Hg), unconsciousness (GCS score #8804; 8), acidosis (base deficit #8804; -6.0), coagulopathy (PTT ≥ 40 seconds or INR ≥ 1.4), or age (≥ 70 years). The addition of a relevant physiological condition or pathophysiological change in combination with AIS is reasonable to increase its predictive power for mortality [20]. The “New Berlin Definition” is a new standard for the definition of polytrauma in recent years. It is evidence-based and derived from a large database, rather than level IV (expert opinion). It covers various physiological and pathological factors and is worthy of promotion in clinical applications. Based on the original definition, and in combination with a number of indicators closely related to vital signs, it makes the new standard more realistic and applicable for polytrauma patients [18]. However, the “New Berlin Definition” has not yet been widely applied, and its predictive capacity and potential to reduce mortality need further research and testing.

This study is the first to identify, rank and characterise the articles from the past decade in the field of the definition of polytrauma. The results of the research show the application status and characteristics of the definition of polytrauma, while providing the necessary information for scholars in related fields to improve the definition of polytrauma. The main limitations of this study are twofold. Firstly, the time span is not long enough. If the study period was 20-30 years, then a more comprehensive analysis of the clinical application of the definition of polytrauma could be performed. Secondly, the selected articles are all in English, therefore, some articles written in other languages could not be included in the study.

5. Conclusions

In the past decade, the definition of polytrauma in clinical research has been mainly based on ISS. The appearance of the “New Berlin Definition” provides a new direction for its development. However, there is still much variation between definitions which is unhelpful, and a globally recognised definition of polytrauma established through the WHO consensus meeting would be highly beneficial.

Abbreviations

AIS, Abbreviated injury scale; ICU, Intensive Care Unit; ISS, Injury severity score; NISS, New injury severity score; RCTs, Randomized control trials.

Ethics approval and consent to participate

Not applicable.

Author contributions

Ding Xu and Peng Luo designed the study. Ding Xu and Yulong Shi collected the data. Yulong Shi and Peng Luo analyzed the data. Ding Xu and Weijun Guo analyzed the results and drafted the manuscript.

Acknowledgements

Thanks to all the peer reviewers for their opinions and suggestions, especially Professor Hans-Christoph Pape (University of Zurich, Switzerland).

Funding

Not applicable.

Conflict of interest

The authors declare that there is no conflict of interest regarding the publication of this article.

Availability of data and material

All data generated or analysed during this study are included in this published article.