Injuries, treatment, and impairment caused by different types of fireworks; results of a 10 year multicenter retrospective cohort study

This was a retrospective, multicenter, observational case series. Potential participants were selected from two tertiary referral hospitals in the Southwest Netherlands: a level 1 trauma center and a specialized burn center. This study was exempted by the Medical Research Ethics Committee Erasmus MC (Rotterdam, the Netherlands; registration number MEC-2018-1254).

All patients (no age limit) with fireworks-related injuries, treated at one of the participating hospitals between December 1 and January 31 during the years 2007 (December) to 2017 (January), were eligible for participation. Patients were excluded if they died within the first 24 h due to other injuries and if patients’ medical records were incomplete regarding their injuries. Eligible patients (or parents/guardians) had to provide informed consent.

Potential participants were identified by searching the medical records on the terms “fireworks”, “bangers”, and “rockets”. They were screened for eligibility and were asked for informed consent by email or telephone. A reminder was sent after two and 4 weeks. Patients who refused participation were excluded. DTVY and JND screened patients for eligibility, obtained informed consent, and collected data by reviewing the patient’s medical records.

A formal sample size calculation for this observational study was not constructive because of the descriptive and non-comparative study design. The Dutch Consumer Safety Institute – an institute responsible for public accident and injury prevention – mentioned 574 patients treated with fireworks-related injuries in 2014–2015 in the Netherlands [10]. With 2 months for inclusion and participation of two tertiary referral centers for advanced trauma care and burn injuries, approximately 200 patients in 10 years were estimated.

The primary outcome was the number of patients with any type of injury caused by fireworks. The number of injuries, including location and type (e.g., burns, soft tissue damage, or eye injury) were recorded. Burns were categorized as superficial, partial thickness (dermal), full thickness (subdermal), and mixed depth (partial and full thickness). Eye injury was categorized based upon the anatomical region affected, and soft tissue damage in superficial and deep lacerations. Amputations of digits were scored as full or partial. An amputation above the metacarpal phalangeal joint was considered as a partial amputation.

The secondary outcome measures were patient and injury characteristics, treatment details, and the percentage whole person impairment (WPI). Patient characteristics included age and gender. Accident information included the role of the patient (operator or bystander), the type of fireworks (explosive, decorative, calcium carbide, or homemade), and whether the fireworks was legal or illegal. Details regarding the definition of the different types of fireworks are provided in Table 1. Regarding treatment characteristics the hospital and intensive care unit (ICU) admission rates and length of stay were noted. Furthermore, the number and type of surgical interventions and the need for rehabilitation (physical, hand, and occupational therapist) was registered. For each injury, the percentage WPI was registered, according to the American Medical Association’s Guides to the Evaluation of Permanent Impairment [11]. For example: a complete hand amputation accounted for 56% WPI and a blind eye for 25%. In patients with more than one injury a combined WPI percentage was determined according to the guideline.

Statistical analyses were performed using the Statistical Package for the Social Sciences version 25 (SPSS, Chicago, Ill., USA). Data were reported following the ‘Strengthening the Reporting of Observational studies in Epidemiology’ (STROBE) guidelines.

Normality of continuous data was tested with the Shapiro-Wilk test. This showed that all data deviated from the standard normal distribution. Missing values were not replaced by imputation.

Descriptive analyses were performed in order to report the data for the entire population as well as for the main types of fireworks. For continuous data, median and quartiles were reported. For categorical data, number and frequencies were reported. No statistical comparison was made between the types of fireworks.

Of the 297 patients who met the eligibility criteria, 25 patients were excluded because they refused to participate. A total of 272 patients were included in this study (Fig. 1). The median duration of clinical follow-up was 13 (P₂₅-P₇₅ 3–87) days.

The number of patients treated annually is shown in Fig. 2. This figure shows information for the entire group and for the different types of fireworks. From 2007 to 2017, between 21 and 40 patients were treated annually. The total number of patients treated increased from 24 in 2007 to 40 patients in 2014, and decreased again to 22 patients in 2017. From 2010 to 2014, explosive fireworks accounted for the greatest proportion of injuries. During this period, between 20% (N = 8) and 42% (N = 13) of patients had injuries induced by explosive fireworks. From 2014 this number decreased to levels comparable with other types of fireworks. The number of patients injured by rockets decreased over the last 4 years, from seven in 2014 to one in 2017. No clear increase or decrease was observed in the total number of patients treated and in the number of patients per type of fireworks.

Information on patient and fireworks characteristics are presented in Table 2. For the entire group, the median age was 18 (P₂₅-P₇₅ 13–30) years. A total of 114 (42%) patients were children younger than 16 years old. The majority of patients (N = 227; 84%) were males and nearly half of all patients (N = 87; 40%) were bystanders. More than half of the patients (N = 50; 60%) were injured by legal fireworks.

The majority of injuries were caused by decorative fireworks (N = 89; 51%), in particular rockets (N = 45; 50%), followed by explosive fireworks (N = 67; 39%). In 99 (25%) patients the type of fireworks was unknown. The median age differed widely per type of fireworks, from 13 years in the group ‘others’ to 29 years in the group of aerials. In all subgroups, males accounted for more than 80% of the patients, except for the rockets subgroup (N = 29; 64%). Rockets had the highest percentage of bystanders (N = 27; 77%); all other groups had less than 39% bystanders.

In 272 patients a total of 395 injuries were reported. Most injuries were located to the upper extremity (N = 177; 45%), followed by the head/neck (N = 101; 26%), and the eyes (N = 49; 12%; Table 3). Explosive fireworks mainly resulted in upper extremity (N = 65; 68%) injuries, while rockets (N = 24; 41%) and aerials (N = 7; 41%) mainly affected the head/neck region.

Burns were the most common injuries (N = 208; 53%), and they were mainly of partial thickness (N = 162; 78%). The second most common type of injuries were soft tissue lacerations (N = 67; 17%), of which most were superficial (N = 48; 73%), and the third most common type were eye injuries (N = 49; 12%). Six patients had bilateral eye injury. One child and five adults had a fully destructed eye and were considered legally blind. Thirty-one (8%) injuries were fractures, of which the finger (N = 19; 61%), hand (N = 7; 23%), and face (N = 6; 19%) were the most common locations. Furthermore, 19 (5%) injuries were amputations, which were all located to the hand or fingers. Two hands, 32 fingers (29 partial), and four thumbs (two partial) were amputated.

Decorative fireworks mostly resulted in burn injuries (N = 82; 68%), of which 60 (73%) injuries were of partial thickness. Explosive fireworks mostly caused soft tissue lacerations (N = 24; 25%), fractures (N = 16; 17%), and amputations (N = 14; 15%). Homemade fireworks mostly caused burns (N = 18; 58%). Eye injuries were mostly caused by rockets (N = 12; 24%) and explosive fireworks (N = 8; 16%).

In total 79 (29%) patients were admitted to a hospital for treatment, and 10 patients (4%) were admitted to the ICU (Table 4). The median hospital length of stay was 4 (P₂₅-P₇₅ 2–9) days. Fifty-one (19%) patients underwent surgery, of whom 22 (42%) underwent two or more procedures, with a maximum of 10. Furthermore, 57 (22%) patients received professional rehabilitation, of which most consulted a physical therapist (N = 29; 51%) or a hand therapist (N = 35; 61%).

Patients with injuries induced by carbide and homemade fireworks were most often admitted to a hospital (respectively N = 2; 100% and N = 12; 80%), followed by patients injured by explosive fireworks (N = 24; 36%). Patients from the subgroup ‘others’ had the longest hospital length of stay; 9 (P₂₅-P₇₅ 3–18) days. Homemade (N = 7; 47%) and explosive fireworks (N = 22; 33%) resulted in the highest percentage of injuries that required surgical treatment.

In this study, no fatal casualties were observed. The WPI found in this study ranged from 0 to 95%. In 34 (14%) patients, the injuries resulted in a WPI of ≥1%; 18 (53%) patients used explosive fireworks, four (12%) homemade fireworks, four (12%) rockets, two (6%) ‘others’, and six (18%) the type of fireworks was unknown. In 217 (84%) patients the injuries did not result into permanent impairment and in 21 (8%) patients it was not possible to determine the WPI due to missing data. In all groups, the median WPI was 0% (P₂₅-P₇₅ 0–0).

One child sustained traumatic brain injury resulting from shrapnel from an illegal banger, resulting in 95% WPI. Another child lost a hand from a banger and one adult lost a hand from unknown fireworks, both leading to a WPI of 56%. Seventeen patients with one or more amputations of the upper extremity had a WPI between 2% for a single fingertip amputation, and to 46% for extensive hand trauma with multiple amputations of digits. In fourteen of these patients the injuries were induced by explosive fireworks. Six patients lost an eye and turned blind, resulting in a WPI of 25%. Blind eyes were caused by explosive fireworks (N = 2), rockets (N = 2), homemade fireworks (N = 1), and unknown fireworks (N = 1).

A strength of this study is that it provides a long-term overview of patients who were treated in tertiary referral centers that frequently treat patients with severe fireworks-related injuries. This information provides more insight into the number of patients treated over the past 10 years and the outcomes after multiple years. It also provides more information about the injuries caused by fireworks and describes the association between the type of fireworks and the injuries, treatment, and to what extent it led to permanent impairment. This will help policy makers in developing the best strategy to prevent firework-related injuries.

A limitation in this study could be that only two specialized hospitals were selected to participate in this study. The aim of this study was to focus on the severely injured patients, who are more likely to be treated at a specialized hospital. However, patients with severe eye injuries were often immediately transported to a nearby specialized eye hospital, which functions as a national referral center. Therefore these patients were not included in this study. This likely led to an under representation of the patients with severe eye injuries. Data of these patients treated at this specialized eye hospital were recently published [21]. Furthermore, because of the retrospective design of this study, some data were not registered in patients’ medical records, such as the type of fireworks. This requires caution in making statements about causality. Moreover, a potential weakness of this study is that functional impairment was calculated based on data from hospital records only. For amputations and ocular enucleations, it is clear that impairment will remain. But it is likely that the degree of impairment – also for those who scored 0% WPI now – would have been higher after a specific physical investigation for the purpose of this study. An underestimation due to the calculation based on short term hospital records is very well possible.