Trauma, defined as any serious physical injury to the body that requires medical attention,[[1]] is one of the major causes of disability and death worldwide.[[2,3]] More than one quarter of the five million global deaths from physical injuries annually are the result of motor vehicle crashes (MVCs).[[4]] New Zealand (NZ) is a high-income country with a population of approximately 5.1 million.[[5]] Māori, the Indigenous people of New Zealand, account for 16.5% of the total population.[[6]] Around 50,000 people are hospitalised as a result of injury in New Zealand annually, with an economic cost estimated at NZ$10.2 billion per year.[[7]] An additional NZ$5.7 million is the estimated economic burden per fatality.[[8]] The New Zealand Ministry of Health (MoH) reported in 2016 that an estimated 8% of total health loss from all causes was attributed to injuries.[[3]] However, little is known about the incidence of injuries that have the potential to cause death or long-term disability (major trauma).[[9]]

Major trauma is commonly defined in terms of injury severity. Although there is not an internationally recognised definition of major trauma,[[10]] it has been variably defined as an Injury Severity Score (ISS) greater than 15, which is associated with a mortality risk of 10%.[[11–14]] Since the introduction of the Abbreviated Injury Scale (AIS) AIS-2005-Updated 2008, an ISS>12 is also considered as major trauma.[[10,15–17]]

In order to reduce morbidity and mortality resulting from major trauma, it is important to understand how major trauma is distributed in terms of time, geographic location and population groups. Therefore, this systematic review of the literature aimed to describe the incidence and characteristics of major trauma in New Zealand.

Methods

Inclusion criteria

Studies describing the incidence of major trauma in New Zealand published up to September 2021 were included. For the purposes of this review, “major trauma” was defined as death or an ISS greater than 12 or greater than 15, depending on the AIS version used at the time the injuries were coded.[[11,17]] The AIS is an anatomical scoring system used internationally to rank the severity of individual injuries by body region on a scale of 1 (minor) to 6 (un-survivable injury).[[18,19]] The AIS is the basis of the ISS, which is used to determine the overall severity of multiple injuries.[[20–23]] The ISS is “the sum of the squares of the highest AIS grade in each of the three most severely injured areas”; its maximum score is 75, which is considered as the worst prognosis.[[11,24]] For the purposes of this review, in studies where ISS was not provided but the study included fatal and non-fatal cases, the deaths were assumed to be major trauma and thus were included.

The review considered all injury intents, all age groups, injuries resulting in admission to hospital, prehospital injury deaths and injury deaths occurring in hospital. Studies focusing on treatment injuries were excluded. Non-physical injuries that could not be scored by ISS such as drownings, poisonings and asphyxiations were also excluded (note codes for these three mechanisms were introduced in AIS 2005[[25]]).

Search strategy

Bibliographic computerised searches based on a MEDLINE search strategy were conducted in the following databases: PubMed, EMBASE, CINAHL and Scopus. Medical Subject Headings (MeSH) and keyword search terms used to identify published articles included: “Wounds and Injuries,” “Fatal Injuries,” “Injury Severity Score,” “Major Trauma,” “Severe Trauma,” “Injury Scale,” “Epidemiology,” “Incidence,” “Prevalence” and “Mortality.”  Additional electronic databases, the Te Hononga Whētuki ā-Motu, the National Trauma Network (formerly Major Trauma National Clinical Network (MTNCN)) website and the reference lists of all included studies were examined to identify any potentially relevant articles missed by the electronic search.

Limitations of English language, human population and New Zealand studies were applied. Searches were not restricted by date. LM conducted the initial search, LM and BK independently reviewed the title and abstracts.

Data extraction and appraisal

Duplicates were identified and removed before the titles and abstracts were screened by LM and BK. Full versions of studies potentially meeting the inclusion criteria were then reviewed, and ineligible studies excluded. The following information was abstracted from included studies: study design, information sources, study population, case definitions and main findings. The quality of studies was assessed using the GATE LITE[[TM]] critical appraisal form (www.epiq.co.nz).[[26]] The PRISMA guidelines were followed during data extraction, analysis and reporting.[[27]]

Results

The initial search identified 239 studies. Based on the title and abstract, 61 were considered potentially relevant. Of these, 39 studies fulfilled the inclusion criteria (Figure 1).

Study characteristics

The review period included studies published between 1987 and 2021. Out of the 39 studies included in this review, 19 were based on trauma registry data,[[28–46]] 11 were based on hospital or emergency medical services (EMS) records[[47–57]] and nine involved routinely collected national morbidity and mortality data from the MoH.[[58–66]]

The majority of studies were descriptive observational studies (n=37), two were population-based cohort studies using prospectively gathered trauma database information from the Auckland region.[[30,31]] Twenty-one studies included people of all ages (Table 1), 11 included adults only (Table 2) and seven included children only (under 16 years) (Table 3). Five of the seven studies focusing on children focused on single mechanisms of injuries.[[33,48,53,62,64]]

The majority of studies included patients admitted to hospital following injury (n=16),[[29–32,35–38,40,44,46,47,50,54–56]] with two studies describing trauma admissions to the intensive care unit (ICU).[[51,52]] Four studies considered trauma due to all-terrain vehicles as a primary focus,[[33,39,48,64]] three studies included injuries occurring at home,[[62,63,65]] three studies limited to a particular injury type,[[49,57,66]] two studies considered penetrating trauma[[28,45]] and two studies described bicycle injuries.[[34,58]] Other single mechanisms of injury focused studies included pedestrian injuries,[[53]] motorcycle crashes,[[59]] work-related injuries,[[41]] animal-related injuries,[[43]] livestock-related injuries,[[42]] aircraft crashes[[60]] and river rafting injuries.[[61]]

The definition of major trauma was an ISS>12 in nine studies,[[33–38,40,42,47]] an ISS>15 or death in 16 studies[[29–32,39,41,43,44,50–56,64]] and death in 10 studies,[[28,45,46,58,59,61–63,65,66]] seven of which did not include information of ISS.[[58,59,61–63,65,66]] Four studies did not provide a clear definition of major trauma but reported data on ISS.[[48,49,57,60]]

Figure 1: Summary of study selection (PRISMA flow diagram). View Figure 1.

Only 13 studies provided a full description of the characteristics of major trauma.[[30,31,35–37,46,47,55,58,59,61–63]] The remaining studies presented information about the incidence of major trauma in trauma populations and the characteristics of trauma in general.

Due to the heterogeneity of included studies, it was not possible to explore trends in the characteristics and incidence of major trauma over the period reviewed.

Incidence of major trauma

Paediatric trauma

Among studies that described paediatric trauma, the proportion of major trauma cases among studies that focused on single mechanisms of injuries[[33,48,53,62,64]] ranged from 7%[[48]] for quad bike injuries to 95%[[53]] for pedestrian injuries (Table 3).

In contrast, the study that included all types of paediatric injuries that resulted in admission to hospital reported a prevalence of major trauma of 63%.[[32]] Studies that focused on a particular injury type showed a similar proportion of major trauma (5% for liver injury[[57]] and 6% for pelvic fractures[[49]]).

The study by Creamer et al analysed 2004 trauma registry data (all ages) from the Auckland region and reported a major trauma (ISS≥16) rate for children aged less than 15 years of 17/100,000, the lowest rate among all age groups.[[30]] Kool et al in their analysis of hospitalisations (2000–2009) and deaths (1999–2008) due to head injury reported that the lowest trauma rates were among children aged 5–9 (2.3/100,000).[[66]] However, Collins et al, in their review of pedal bicycle injuries among all ages resulting in death and hospitalisation (1979–1988), found that boys aged 10–14 had the second highest trauma rate (2.3/100,000).[[58]]

Table 1: Epidemiology of major trauma in New Zealand: summary of included studies (all ages). View Table 1.

Table 2: Epidemiology of major trauma in New Zealand: summary of included studies (adults). View Table 2.

Table 3: Epidemiology of major trauma in New Zealand: summary of included studies (paediatric population). View Table 3.

The studies reviewed showed that boys are more affected by major trauma than girls.[[32,33,48,53,62,64]] The review of national morbidity and mortality data by Collins et al found that boys aged 5–9 years and those aged 10–14 years had a higher incidence of major trauma (2.0/100,000 and 2.3/100,000 person-years respectively) than girls (0.6/100,000 and 1.3/100,000 respectively).[[58]] Kool et al found similar results where the incidence of major trauma was higher in boys than in girls aged 5–9 (2.7/100,000 cf. 1.9/100,000) and among those aged 10–14 (4.3/100,000 cf. 2.6/100,000).[[66]] Additionally, Creamer et al found that injury rates among boys aged 0–14 were approximately twice that of girls (23/100,000 cf. 12/100,000).[[30]]

Adult trauma

The proportion of major trauma cases among the total trauma cases reported in the adult population ranged from 4%[[41]] to 89%[[51]] in the studies reviewed (Table 2). A review of trauma registry data from the Auckland region (2004 data) by Creamer et al reported an overall major trauma (ISS≥16) incidence rate of 34/100,000 per year, with rates highest among young adults (15–29 years; 60/100,000) and older adults (≥75 years; 50/100,000).[[30]]

The studies reviewed showed that major trauma occurs most commonly among males.[[40,41,44,45,47,51,61]] The study by Gardiner et al of adult ICU trauma admissions to Auckland Hospital over a 10-year period (1988–1997) found that males had a significantly higher incidence of trauma than females (53.8 cf. 16.7 per 100,000 person-years).[[51]] These findings are consistent with a review of trauma registry records of work-related injuries in the Midland region (2012–2015) by Kool et al, who reported that rates among male workers were approximately five times greater (238/100,000 workers) than among females (44/100,000 workers).[[41]]

Additionally, the review of pedal bicycle injuries among all ages resulting in death and hospitalisation by Collins et al found that males aged 80 years or more had the highest trauma rate (3.5/100,000). However, the authors recommended treating this finding with caution because of the small number of fatalities in this group.[[58]]

Trauma among Māori

Although more than 35% of paediatric major trauma cases occurred among children of European origin[[33,48,53,64]] (range from 38%[[53]] to 89%[[33]]), Māori experienced the highest trauma rates (Table 3).[[31,53]] The review of trauma registry data of injured child pedestrians (<15 years) admitted to Auckland Hospital (1986–1989) by Roberts et al. reported higher trauma rates among Māori children (13.2/100,000) than children of European origin (4.2/100,000).[[53]] These findings are consistent with the population-based study of trauma registry data by Creamer et al, who reported that injury rates among Māori males aged 0–14 years were higher (50/100,000 per year) than among other ethnicities combined (12/100,000 per year).[[31]] However, the same study showed that for females aged 0-14 years, the incidence rate among Pacific children was almost double the rate among Māori children (35/100,000 cf. 19/100,000).[[31]]

Adult trauma rates were higher among Māori than other ethnicities.[[31,51,58]] The population-based study by Creamer et al of trauma registry data reported higher major trauma (ISS≥16) rates among Māori (61.4/100,000 per year) and Pacific people (39/100,000 per year) compared to people of NZ European and other ethnicities combined (29/100,000 per year).[[31]] Gardiner et al found similar results among adult ICU trauma admissions, where the rates for Māori and Pacific patients were greater (123/100,000 and 70/100,000 respectively) than for NZ European patients (36/100,000).[[51]]

For all age groups, the review of major trauma admissions for Māori in the Canterbury region (2006–2018) by Kandelaki et al showed that 9% of major trauma cases occurred among Māori, with Māori males the most affected (75%).[[35]] It also reported similar incidence rates among Māori and other ethnicities (57.9/100,000 cf. 57.3/100,000).[[35]]

Although trauma incidence rates among males[[40,41,44,45,47,51,61]] and Māori[[31,51,58]] were highest in most studies reviewed, a review by O’Leary et al of older adult (≥65 years) trauma cases from the Midland trauma registry between 2012 and 2014 found that injury rates were higher among females (608/100,000) than males (557/100,000) and non-Māori than Māori (594/100,000 cf. 460/100,000).[[40]]

Mechanism of injury

Blunt trauma accounted for more than 80% of all trauma-related admissions among all ages in the studies reviewed (Table 1).[[32,42,51,54–56]] MVCs and falls were the most common mechanism of injury among trauma patients across all age groups.[[31,32,36–38,40,47,51,54,59]] The review of Midland trauma registry data by Kool et al reported that contact with machinery (26%) and falls (19%) were the most common cause of work-related injuries.[[41]] Couch’s review of trauma records of 82 children (<15 years) admitted to two child emergency departments (ED) over one-year period found that MVCs accounted for 57% of all trauma, of which 61% involved pedestrians. Additionally, falls and other mechanisms in this age group (including non-accidental injury) accounted for 34% and 12% of injuries, respectively.[[32]]

This review found that, although major trauma due to falls is common across all age groups in New Zealand, the incidence is highest in older adults (≥65 years).[[40,52,67]] The review of older adult trauma cases in the Midland trauma registry published by O’Leary et al found that among older major trauma (ISS≥13) patients, the prevalence of MVCs was higher than the prevalence of falls in this age group (43% cf. 39%).[[40]]

Among the studies that analysed trauma due to pedal cycles, motorbikes or all-terrain vehicles, the main mechanisms of injury were falls from the vehicle and collisions with motor vehicles.[[39,48,58,64]] Wood et al reviewed data from the Waikato Hospital trauma registry on major trauma patients (ISS>15) with quad-bike related injuries between 2007 and 2011 and found that the main mechanism of injury was rollovers (37%).[[39]]

Studies analysing animal and livestock-related injuries reported that falls from horses (81%) and being hit by cattle, sheep, pigs or goats were the most common cause of injuries, respectively.[[42,43]] Penetrating injuries were uncommon.[[28,45]]

Severity

The head was the most commonly injured body region in major trauma patients in the studies included in this review.[[32,39,40,48,51,53,56,58,66]] The prevalence of head injuries ranged from 26%[[48]] in a review of quad bike injuries in children to 100%[[66]] in a study of incidence and mortality due to head injury. Pearce’s review of paediatric ICU (PICU) records found that, in children under 16 years of age admitted to Starship Children’s Hospital between 2007 and 2014 with head injuries due to a quad bike incident, the mean ISS was 19.4 (range 5–43), which was slightly higher in those who were not wearing helmet at the time of the injury (mean ISS 21.8; range 9–43).[[48]]

Upper and lower extremity injuries were common among major trauma cases. However, these did not represent life threatening injuries.[[33,34,41–43]] Singh et al found that 52% of cycling-related injuries involved extremities.[[34]] A study of major work-related trauma by Kool et al,[[41]] and a study of injuries due to animals by Johns et al[[43]], which reviewed trauma registry data, found similar proportion of extremity injuries (48%[[41]] and 49%[[43]] respectively).

A study by Civil et al of 114 patient hospital records over a six-month period found that 40% of patients with major injuries admitted to hospital had an ISS between 16 and 24, and that no patients with an ISS≥50 survived.[[55]] Safih et al, in their review of Auckland Hospital ICU records, found no difference in the mean ISS between younger (<65 years) and older adult (≥65 years) patients (26 cf. 25).[[52]] Similar results from among patients with liver injuries were reported by Wakeman et al, who did not find difference in the mean ISS (17.5 cf. 17.0) between paediatric (0–17 years) and adult population (≥18 years).[[57]] However, the study of Starship PICU records by Pearce et al found that ISS was higher in children under 5 years of age (mean ISS 22.3) compared to children aged 5–10 years of age (mean ISS 10.5).[[48]]

In terms of ethnicity, the study by Wood et al that examined data from 101 Waikato Hospital trauma registry cases with quad-bike related injuries found that Māori had a significantly higher mean ISS compared to their NZ European counterparts (16.8 cf. 10).[[39]]

Three of the studies reviewed reported an association between length of hospital stay (LOS) and ISS.[[43,47,50]] Czuba et al, in a cohort of 112 patients with major trauma (ISS≥12) from two hospitals in Auckland, found that the median LOS was greater in patients with higher ISS. The results of this study showed that patients with an ISS≤25 stayed in hospital for a maximum 10 days, whereas patients with an ISS>25 were in hospital between 22 and 25 days.[[47]]

Deaths occurring among major trauma patients

The proportion of deaths among major trauma patients in the studies reviewed ranged from 1%[[39]] to 30%.[[55]] An age gradient was evident in some studies, with an in-hospital case fatality rate approximately twice as high in older patients (≥65 years) compared to younger (<65 years) patients (28% cf. 13%; p<0.001).[[29,52]] The review of national morbidity and mortality data (1989 to 1998) by Gulliver et al, where they examined injuries sustained in the home among young children (<5 years of age), found that mortality rates reduced as age increased. Annualised mortality rates among children aged 0–11 months were 28/100,000 compared with 5/100,000 among children aged 48–59 months.[[62]] Collins et al, in their review of pedal bicycle injuries resulting in death and hospitalisation (1979–1988), found that 39% of the fatalities occurred in children between 5 and 14 years old.[[58]] However, in their review of head injuries resulting in death (1999–2008) and hospitalisation (2000–2009), Kool et al found that only 4% of the fatalities occurred in children between 5 and 14 years old.[[66]]

The study by Langley et al which reviewed national mortality data relating to motorcycle crashes (1978–1987) reported a mortality rate of 3.5/100,000 persons per year for all age groups, with males experiencing higher rates than females in those aged 15–24 years (3.4/100,000 cf. 2.0/100,000).[[59]] Similarly, in their study of people aged 25–59 years who died as a result of unintentional falls at home, Kool et al found the fatality rate for males was three-times higher than the female rate (0.63/100,000 cf. 0.20/100,000).[[63]]

Mortality rates in the studied reviewed also varied by ethnicity. Although Māori accounted for less than 30% of all trauma-related deaths[[31,59,65]] (range from 9%[[59]] to 25%[[65]]), this group experienced the highest fatality rates. The Auckland regional study by Creamer et al of trauma registry data (ISS>15) reported higher injury mortality rates among Māori (28.4/100,000 per year) and Pacific (16.4/100,000 per year) compared to NZ European and other ethnicities combined (11.9/100,000 per year).[[31]] Kool et al found similar results in patients aged 20–64 years for unintentional injuries that occurred at home, with fatality rates of 5.4/100,000 among Māori and 3.0/100,000 for NZ European.[[65]] However, the review of major trauma admissions for Māori conducted by Kandelaki at al showed that the proportion of deaths was lower for Māori compared to other ethnicities (5% cf. 11%).[[35]]

The main causes of death in major trauma patients in the studies reviewed were MVCs[[30,31,46,58]] (range 32%[[46]] to 88%[[58]]) and falls[[30,31,46,63,65]] (range 10%[[46]] to 23%[[31]]). The study of unintentional injuries occurring at home resulting in death (1998–2007) or hospitalisation (2000–2009) conducted by Kool et al found that over a 10-year period burns were one of the main mechanisms of injury resulting in death (12%).[[65]]

In relation to the nature of injuries sustained, head injuries were common (60%–100%) among fatal injury cases.[[58,66]]

Impact of COVID-19 in major trauma admissions

Coronavirus disease 2019 (COVID-19) has changed the live and daily routine of many people around the world. Due to its rapid spreading, the World Health Organization (WHO) declared it as a global pandemic on 11 March 11 2020.[[68]] Two weeks later, on 25 March at 11:59pm, New Zealand moved to level 4 (lockdown), the highest level of a four-level alert system announced by the New Zealand Government, in order to eradicate the virus and avoid overburdening the healthcare systems.[[36,37,69]] Although the effects of the lockdown are yet unknown, some studies conducted in New Zealand have shown a significant impact on the number of major trauma admissions.[[36–38]]

The study conducted by Christey et al of trauma patients admitted to a level one trauma centre in New Zealand pre-lockdown (5–18 March 2020) and during lockdown (26–April 8 March 2020) showed a reduction of 50% in all major trauma admissions. This study also found that it was a decrease in the number of trauma admissions for males (50% reduction), children aged 0–14 years (48% reduction) and Māori (39% reduction). Although it was a significant reduction in the number of trauma admissions due to falls and MVCs (48% and 74%, respectively), these continue being the most common mechanism of injury during lockdown in New Zealand.[[38]] Similarly, in their study of major trauma patients admitted to Christchurch Hospital before (22 February–25 March), during (26 March–27 Arpil) and after lockdown (28 April–30 May), Fan et al found a 42% reduction in the number of major trauma admissions during lockdown in all sex and age groups. The most common mechanism of injury before and after lockdown was transport-related injuries. However, during lockdown falls were the most common injury (48%). Road and home were the most common places of injury across all periods.[[37]]

The study by McGuinness et al, which reviewed major trauma registry data in the Northern Region (16 March–8 June 2020, and in the same period in 2019), reported a decreased in major trauma admissions of 25% in 2020 compared to 2019. Although it was a reduction in age, gender, mechanism of injury, type of injury and injury intent, the differences were not statistically significant. An increase in the number of injuries occurring at home was observed in 2020 compared to 2019 (35% cf. 20%).[[36]]

Discussion

The aim of this review of the published literature was to describe the incidence and characteristics of major trauma in New Zealand. Thirty-nine studies met the review eligibility criteria. The studies included were mainly descriptive observational studies that had analysed routinely collected data from trauma registries, hospital records or national morbidity and mortality data. The proportion of major trauma reported in the studies reviewed was variable, ranging from 4%[[41]] to 95%.[[53]] This in part reflects the heterogeneous case definitions used, and the different populations studied (eg, trauma registry data cf. MoH morbidity and mortality data).

The results demonstrate that differences in trauma rates exist in New Zealand by sex, ethnicity and age. This review found rates of major trauma are highest among young adults (15–29 years) and older people (≥75 years), and lowest among children aged 0–14 years.[[30,58]] These findings are consistent with a review of Japan’s trauma registry data by Kojima et al, which found that moderate to major trauma (ISS≥9) occurs most commonly among elderly people aged 60 years or older (53%), and less common among children (9%).[[70]]

This review also showed that in both the paediatric and adult populations, males[[32,33,40,41,44,45,47,48,51,53,61,62,64]] and Māori[[31,51,53,58]] are the subgroups most affected by major trauma in New Zealand. These results are consistent with data from annual report (2018–2019) of the New Zealand Major Trauma Registry & National Clinical Network (MTNCN), which showed the incidence of major trauma was higher among males in all age groups, and that Māori experienced higher major trauma rates (56/100,000) than non-Māori (43/100,000).[[71]]

Blunt trauma due to MVCs and falls were the main mechanisms of trauma resulting in hospitalisation and death in New Zealand in this review.[[30–32,36–38,40,42,46,47,51,54,56,58,59,63,65]] For the paediatric population, these findings are consistent with a review of five years of data from a Swiss trauma registry, which found blunt trauma represented 92% of all admissions and that 42% of the patients had major injuries (ISS>15), of which 76% were males with injuries primarily due to falls (40%) and MVCs (34%).[[72]]

Chico-Fernández et al reported that 79% of the trauma patients admitted to ICU in Spain (2012–2015) were young men, and that the main mechanism of injury was falls (37%).[[73]] A study conducted in Australia by Harris et al, which included 355 patients with major trauma, found that 63% of the cases were due to MVCs and that males were more overrepresented (72%).[[74]] Similar results were found by Alberdi et al in another Spanish study investigating the epidemiology of severe trauma in all age groups, where the main cause of trauma among patients aged 15–25 years was road traffic related injury, and that older patients (>65 years) had a greater mortality rate than younger people (35% cf. 15%).[[75]]

Major trauma studies in Australia have found that males aged between 15 and 24 years account for the majority of all trauma admissions, with blunt trauma from MVCs being the main cause of injury.[[76,77]] However, the New Zealand MTNCN’s annual report (2018–2019) showed that there are three age peaks (15–29, 45û60 and 85+), with the 15–29 age group having the greatest burden of injury.[[78]] Although patterns of trauma are similar in Australia and New Zealand, incidence rates differ.[[77]] According to the Victorian State Trauma, the incidence of major trauma in 2016–2017 was 55/100,000,[[79]] which is greater than that reported by the New Zealand MTNCN in 2018–2019 (48/100,000).[[71]]

In the current review, among major trauma patients the head was the most common body region injured. [[32,39,40,48,51,53,56,58,66]] A Spanish study conducted by Rastogi et al of 748 patients (all ages) admitted to a major trauma centre in India reported 57% of patients had sustained head injuries.[[80]] Alberdi et al, in their study of the epidemiology of severe trauma in Spain, found a lower prevalence (33%–47%).[[75]] The Spanish studies both identified a statistically significant association between ISS and mortality.[[73,75]] The studies included in this review suggest that length of stay in hospital is influenced by ISS.[[43,47,50]] However, the relationship between ISS and mortality could not be examined in this review because seven of the 10 included studies defined major trauma as death and did not include information about ISS.[[58,59,61–63,65,66]]

Trauma admissions in New Zealand have experienced a decrease during the COVID-19 pandemic,[[36–38,81]] mainly due to the restrictions on the free movement orchestrated by different governments around the world, reinforcing the notion that trauma is a social disease. The studies reviewed reveal a reduction of more than 40% in major trauma admissions during lockdown, with the greatest reductions observed in males, children aged 0–14 years and MVCs.[[36,37]] The New Zealand MTNCN’s annual report (2019–2020) showed the incidence of major trauma was lower in 2019/20 than in 2018/19 (44/100,000 cf. 48/100,000) and reported a 50% reduction in major trauma admissions across the country during the initiation of level 4 (lockdown), mainly due to changes in transport injuries.[[82]] Similar results were found in a study conducted in South Australia by Harris et al, who reported a 33% reduction in major trauma admissions, especially for those aged 40 years or older and for transport-related trauma (45% reduction in each case).[[83]]

Strengths and limitations

This review provides a useful summary of studies of major trauma in New Zealand that have been published up until September 2021, providing historical context for those working in the trauma or injury prevention fields. The strength of this review includes a rigorous methodology to identify relevant studies through an exhaustive search of the current data in multiple electronic databases. Two independent reviewers (LM and BK) performed the literature search, selected and evaluated the quality of the articles, which enhanced validity and reliability. Results have been reported following the PRISMA guidelines.[[27]]

The strengths of studies included in this review that analysed data from the MoH[[58–66]] include the ability to explore trends over time, and the population-based nature of the data. However, MoH morbidity databases do not include trauma-specific injury severity indices,[[58]] which explains why information related to ISS was not reported in some articles or had to be calculated in others using the AIS. Comparisons of findings between studies were difficult due to the differences in sample sizes, population groups and major trauma definitions.

The review findings need to be considered in light of some limitations. The review period included studies from 1987 to 2021, a time during which there were a number of AIS revisions,[[19,25]] resulting in potential differences in how major trauma is defined and having a potential impact on injury research. Since the development of AIS in 1971 by the Association for the Advancement of Automotive Medicine (AAAM), there have been some updates,[[15,25,84]] the most recent being the AIS 2015.[[19,85]] The AIS 2005 update brought significant changes in scores for some body regions, in particular for the thorax and head regions.[[15,84]] The 2008 update provided further refinements to the classification deficits.[[20,25]] The AIS 2015 update improved brain injury and spinal cord coding.[[85]] Palmer et al noted that there is a significant decrease in the number of patients classified as major trauma when converting AIS98-coded data to AIS08.[[86]] From the information provided, 48% of the studies included in this review used the AIS98 or previous versions, and the remaining studies used the AIS05/08 versions. Given the findings of Palmer et al, this may mean the earlier studies in this review may have overestimated the severity of injury reported.

Another limitation is the ability to calculate an overall estimate of the incidence of major trauma in New Zealand; this is challenging due to the lack of a clear definition of major trauma in included studies, and difficulties in comparing trauma registry studies with non-trauma registry studies due to the exclusion of non-physical trauma in the former (eg, poisoning, asphyxiation and drownings). Although ISS has been recognised as the “gold standard” scoring system for trauma, it has substantial limitations.[[11,12,24,87]] Firstly, ISS scoring is expensive as a significant amount of time and effort is required for AIS collection.[[88,89]] Moreover, the scored injuries are often not even the three most severe injuries as the ISS only considers at most only three of a given patient’s injuries, one per body region.[[11,24]] Additionally, it does not take account for contextual information such as comorbidities and issues relating to the event itself that may have contributed to patient outcomes.[[89]] A study of the accuracy of injury coding in New Zealand by Davie et al found, in a random sample of public hospital discharges, that 14% of the principal injury diagnosis and 26% of the external cause codes had inaccuracies, which were identified on the first, second or third characters.[[90]] This is likely to have affected the completeness of case ascertainment in the studies reviewed.

Only half of the studies reviewed reported ethnicity. Previous New Zealand research has highlighted that Māori are disproportionally represented in national injury data.[[91,92]] Additionally, it has been found that ethnicity reported on the national systems can differ to what patient identifies. The study of Scott et al evaluated the quality of ethnicity data (self-reported compared to that recorded by the Waikato Hospital trauma registry) and found the percentage of self-identified ethnicity that mismatched trauma registry ethnicity was 21% for Māori compared to 4% for non-Māori.[[93]]

There was limited South Island data included in the published studies reviewed. The majority of studies found were conducted or included data from the North Island, especially from Auckland and the Waikato region. Trends over time were unable to be described due to the heterogeneity of the included studies.

There is a scarcity of data relating to ethnicity, and major trauma among children in the international published literature which makes it difficult to compare the findings of this review with those from other countries.

Conclusion

The incidence of major trauma in New Zealand varies by age, sex and ethnicity. Although the New Zealand MTNCN has provided national level data on the incidence and outcomes of major trauma since 2015, the findings of this review highlight the need for further analytical studies that can explore factors that may impact survival from major trauma and continued efforts to prevent injuries in New Zealand. Changes in major trauma admissions during the COVID-19 pandemic as part of public health interventions, reinforce the notion that trauma is a social disease.