Introduction

Traumatic spinal fractures (TSFs) are often associated with a significant impact on activities of daily living, resulting in a considerable socioeconomic burden1,2,3,4,5,6. Motor vehicle collisions (MVCs) are the main causes of TSFs, accounting for 15–67% in different studies7,8,9,10,11,12,13. TSFs have been discussed in many studies, especially TSFs caused by MVCs14,15,16,17,18,19,20,21. Age plays an important role in the pattern of TSFs resulting from MVCs18,19,20. Thoracic and lumbar spine fracture patterns are influenced by the age of the occupant. Extension injuries occur in older obese individuals and are associated with a high fatality rate20.

MVC is a serious health problem that results in associated injuries (ASOIs), such as orthopaedic fractures, craniocerebral injury, and thoracoabdominal injuries, and complications including deep venous thrombosis, pneumonia, pressure sores, urinary infection and postoperative infection. TSFs due to MVCs are commonly associated with orthopaedic fractures. This association occurs in distinct patterns and influences patient outcomes15. Thoracic and abdominal injuries account for 10.5% of MVC-related TSFs16. Traumatic spinal cord injuries (TSCIs) have a devastating effect on the quality of life of patients. Most TSCIs with TSFs caused by MVCs affect young patients and involve severe neurological impairments21. The characteristics of SCIs caused by MVCs have not been thoroughly studied, especially according to sex, age group, role and geographic location. Delays in the diagnosis of SCI and associated injuries (ASOIs), such as craniocerebral injury (CCI), intrathoracic injury (ITI) and intra-abdominal injury (IAI), may cause significantly increased morbidity and mortality.

In most of the studies on spinal fractures, researchers have simply reported that MVCs were the main cause of spinal fracture and indicated trends regarding related MVCs but have not discussed the specific epidemiological characteristics of the MVCs7,8,9,10,11,12,13. Reports from studies on spinal fracture caused by MVCs have included discussions of only some aspects of MVCs14,15,16,17,18,19,20,21, such as injured front-seat occupants14, paediatric passengers18 or elderly subjects19, traumatic spinal injury associated with orthopaedic fractures15, thoracoabdominal injuries16, and thoracolumbar fractures17,20. Although much is known about the characteristics of TSFs, TSFs caused by MVCs have not been discussed in depth according to different sexes, age groups, roles and geographic locations in a single study. In the current study, cases from multicentre tertiary hospitals in Chongqing and Shenyang that occurred between January 2013 and December 2019 were reviewed and analysed. The main purpose of the study was to investigate sex, age, role and geographic differences, especially in the pattern of ASOIs, spinal cord injuries and complications of TSFs caused by MVCs in adults (≥ 18 years old).

Materials and methods

Study population

We retrospectively identified 798 patients presenting to our hospitals with acute TSFs caused by MVCs between January 1, 2013, and December 31, 2019. There were 521 male and 277 female patients, with a mean age of 44.4 ± 13.7 years (range 18–90 years old) and a sex ratio of 1.88. Among the cases of TSF, 501 occurred in Chongqing, which is located in the southwest hot-moist region of China (the CQ group), and 297 occurred in Shenyang, which is located in the cool northern region of China (the SY group). Chongqing is the economic and financial centre of the upper Yangtze River and is mainly hilly and mountainous, with a large area of sloping land known as the “mountain city” and “foggy Chongqing.” It has a humid subtropical climate with annual temperatures ranging from 4 to 29 °C. The average temperature is 16–18 °C, and the annual precipitation is 1000–1350 mm. Shenyang is located in the cool northern region of China, the central part of Liaoning Province, extending mainly to the plains. It has a semihumid temperate continental climate, with annual temperatures ranging from − 35 to 36 °C. The average temperature is 8.3 °C, and the annual precipitation is 500 mm. The patients representing these cases were then categorized into a male group (n = 521) and a female group (n = 277) and a young adult group (n = 687) and an elderly group (n = 111) as well as driver (n = 333), passenger (n = 215) and pedestrian groups (n = 250). Data were collected from the General Hospital of Northern Theater Command, which is the largest military hospital in Northeast China (Shenyang), and Xinqiao Hospital and Southwest Hospital of Army Medical University, which are the two largest military hospitals in Southwest China (Chongqing). The hospitals where the patients were admitted are the main hospitals where patients with TSF and SCI are treated.

X-ray, computed tomography (CT) and magnetic resonance imaging (MRI) examinations were performed to make a definite diagnosis of spinal fractures. Data regarding sex (male and female), age (18–60 and ≥ 60), district (Chongqing and Shenyang), injury season (spring, summer, autumn and winter), role (driver, passenger and pedestrian), vehicle involved (car, motorcycle, truck, battery electric vehicle, bicycle, taxi, bus, tricycle, van), ASOI, complications, fracture location and spinal cord injury (SCI) were recorded. ASOIs included upper limb fractures (ULFs), lower limb fractures (LLFs), pelvic fractures (PFs), craniocerebral injury (CCI), ITI and IAI. Complications included deep venous thrombosis, pneumonia, pressure sores, urinary infection, and infection. Fracture locations included cervical, thoracic, lumbar, cervical + thoracic, cervical + lumbar, thoracic + lumbar and others. The American Spinal Injury Association (ASIA) scoring standard was used to assess SCI. Noncontiguous spinal fractures (NSFs) were defined as fractures in which there was at least one intact vertebra present between two injured or fractured vertebrae. The study was approved by the Ethics Committee of General Hospital of Northern Theater Command, and informed consent was obtained from all individual participants included in the study.

Statistical analysis

All data were analysed using SPSS software (version 24.0, SPSS Inc., USA). The chi-square test or Fisher's exact test was used for the frequency data. Student’s t test was used to compare continuous variables between the two groups. One-way analysis of variance was used for comparisons among different groups. P < 0.05 was considered indicative of statistical significance.

Ethical approval and informed consent

All procedures were in accordance with the ethical standards of the Institutional Research Committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The study protocol was approved by the Ethics Committee of the General Hospital of the Northern Theater Command of the Chinese PLA.

Results

General characteristics of TSFs and TSCIs

The records of 798 patients who presented with TSFs resulting from MVCs between 2013 and 2019 were retrospectively reviewed (Table 1). There were 521 (65.3%) male and 277 (34.7%) female patients. The mean age of the patients was 44.4 ± 13.7 years (range: 18–90 years). Fractures most often occurred in the winter (26.6%) season. The roles were divided into driver (333, 41.7%), passenger (215, 26.9%) and pedestrian (250, 31.3%). The most common vehicles involved were cars (69.8%), motorcycles (11.5%), trucks (4.7%), battery electric vehicles (2.5%) and bicycles (3.3%). The most common fracture locations were the lumbar segment (287, 36.0%), cervical segment (244, 30.6%) and thoracic segment (175, 21.9%).

Table 1 Sex differences in TSFs caused by MVCs.
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There were 389 patients (48.7%) who presented with ASOIs, 62 patients (7.8%) who presented with coma after injury, 35 patients (4.4%) who presented with complications, 425 patients (53.3%) who presented with SCI and 101 patients (12.7%) who presented with NSFs. The most common associated injuries were ITIs (214 cases, 26.8%), CCIs (102 cases, 12.8%) and LLFs (65 cases, 8.1%). The most common complications were pneumonia (22 cases, 2.8%) and deep venous thrombosis (7 cases, 0.9%). Using the ASIA classification, 107 patients (13.4%) exhibited ASIA A, 34 patients (4.3%) exhibited ASIA B, 47 patients (5.9%) exhibited ASIA C, 137 patients (17.2%) exhibited ASIA D, and 373 patients (46.7%) exhibited no neurological deficits (Table 1).

Gender differences in TSFs

Significant differences in the distribution of district (p = 0.018), role (p < 0.01), motorcycle (p = 0.011), battery electric vehicle (p = 0.045), bicycle (p = 0.027), coma after injury (p = 0.002), pelvic fracture (p = 0.021), craniocerebral injury (p = 0.008) and fracture location (p < 0.01) were observed between the male and female groups. Driver and cervical fracture were observed at a higher frequency among male patients than among female patients. Passenger, pedestrian, thoracic fracture and lumbar fracture were observed at a higher frequency among female patients than among male patients (Table 1) (Figs. 1, 2, 3, 4).

Figure 1
figure 1

Distributions of age, sex and role according to different groups.

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Figure 2
figure 2

Distributions of associated injuries and complications according to different groups.

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Figure 3
figure 3

Distributions of fracture locations according to different groups.

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Figure 4
figure 4

Distributions of spinal cord injury (ASIA classification) according to different groups.

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Age differences in TSFs

Significant differences in the distribution of district (p < 0.01), role (p < 0.01), car (p = 0.013), coma after injury (p = 0.003), lower limb fracture (p = 0.016), fracture location (p = 0.001) and spinal cord injury (p < 0.01) were observed between the young adult and elderly groups. Driver, passenger, and cervical fracture were observed at a higher frequency among adult patients than among elderly patients. Pedestrian and lumbar fracture were observed at a higher frequency in elderly patients than in adult patients (Table 2) (Figs. 1, 2, 3, 4).

Table 2 Age differences in TSFs caused by MVCs.
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Role differences of TSFs

Significant differences in the distributions of sex ratio (p < 0.01), age (p < 0.01), district (p < 0.01), most vehicles involved (P < 0.01), lower limb fractures (p < 0.01), pelvic fracture (p < 0.01), fracture locations (p < 0.01), complications (p < 0.01), and spinal cord injury (p < 0.01) were observed among the three different groups. Drivers presented with a higher sex ratio. Pedestrians presented with a higher frequency of elderly patients, LLFs and PFs than those in the driver and passenger groups. Pedestrians presented with higher frequencies of thoracic and lumbar fractures and a lower frequency of cervical fracture than drivers and passengers. Drivers and passengers presented with a higher frequency of SCI and a lower frequency of complications than pedestrians (Table 3) (Figs. 1, 2, 3, 4).

Table 3 Role differences in TSFs caused by MVCs.
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Geographic differences in TSFs

Significant differences in the distributions of sex ratio (p = 0.018), age (p < 0.01), role (p < 0.01), most vehicles involved (p < 0.01), coma after injury (p = 0.030), LLFs (P = 0.002), pelvic fracture (p < 0.01), craniocerebral injury (p = 0.011), intrathoracic injuries (p < 0.01), intra-abdominal injuries (p < 0.01), complications (p = 0.033) and spinal cord injury (p < 0.01) were observed between the Chongqing and Shenyang groups. The patients in the CQ group presented with a higher sex ratio and a higher frequency of adult patient, driver, passenger, SCI and complications than those in the SY group (Table 4) (Figs. 1, 2, 3, 4).

Table 4 Geographic differences in TSFs caused by MVCs.
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Discussion

Among MVC-related injuries, abdominal and thoracic injuries are serious, resulting in approximately 10% and 25% of MVC-related deaths, respectively22,23. Thoracic and abdominal injuries increase the risk of spinal injuries24. Thoracic injuries, especially dorsal spinal injuries, commonly accompany TSFs. Thoracic injuries account for 41% of TSF patients and are considered to be the most common TSF-associated injuries7. The in-depth analysis of the association discussed above is more important following MVCs because MVCs result in more TSF-associated injuries than situations involving lower energy mechanisms7,25,26. This in-depth analysis will contribute to a better understanding of the disease and more effective prevention of injury.

Gender plays an important role in the pattern of TSFs resulting from MVCs. Male patients were more frequently associated with driver, cervical fracture, and CCI than female patients. Female patients were more frequently associated with passenger, pedestrian, thoracic and lumbar fracture, and SCI than male patients. A previous study showed that thoracic and abdominal injuries accounted for 10.5% of MVC-related TSFs, and male patients with MVC-related TSI were more frequently associated with thoracic- and abdominal-associated injuries than females16. In the current study, the number of male patients exceeded the number of female patients, a phenomenon that could be explained by gender demographics and the Chinese culture; men are involved in more social activities than women, and women rarely drive motorcycles.

Age also plays an important role in the pattern of TSFs resulting from MVCs. Adult patients were more frequently associated with driver, passenger, cervical fracture and SCI than elderly patients. Elderly patients were more frequently associated with pedestrian and lumbar fracture than adult patients. Thoracic and lumbar spine fracture patterns are influenced by the age of the occupant and the type and use of seat belts. Extension injuries occur in older obese individuals and are associated with a high fatality rate20. Previous studies have shown that established risk factors for fatal teen driver crashes, including restraint nonuse, transporting teen passengers, and speeding, also increase the risk of nonfatal injury in single vehicle crashes27. Thus, more attention should be given to the timely diagnosis and treatment of cervical fracture and spinal cord injury among young patients, especially when the patient is rushed to the hospital for emergency treatment.

MVC patients with different roles, such as driver, passenger or pedestrian, exhibit different distributions of injury characteristics, and the phenomenon is directly related to the population studied and the local traffic situation28,29,30,31. Head injuries account for most pedestrian fatalities in crashes with powered 2-wheelers in India, and lower extremity injuries account for most nonfatal injuries28. Older pedestrians, male drivers, older drivers and intoxicated motorists are prevalent determinants of pedestrian fatalities in glare-related crashes29. Enhancing the conspicuity of pedestrians with the use of visibility aids may be beneficial for reducing crash risk or severity30. Pedestrians may be at increased risk of injury when the driver is male, when the driver is under the influence of alcohol, when the pedestrian is struck while in the travel lane, when the pedestrian is aged 65 or older, and when the pedestrian is under the influence of alcohol31.

In the current study, drivers, who presented with the highest sex ratio (3.7), accounted for 41.7% of TSFs caused by MVCs. Pedestrians were observed at a higher frequency among elderly patients, LLFs and PFs than drivers and passengers. Pedestrians exhibited a higher frequency of thoracic and lumbar fractures and a lower frequency of cervical fractures than drivers and passengers. Drivers and passengers exhibited SCIs at a higher frequency than pedestrians. Passengers presented with fewer lower extremity fractures due to the protective nature of the car cage. It has been shown that pedestrians are prone to CCIs, ITIs, LLFs and PFs due to multiple impacts. We should provide advanced life support measures at the scene, stabilize the airway and protect the entire spine of pedestrians. NSFs were observed at a greater frequency among passengers and pedestrians than among drivers. Much more attention should be given to passengers and pedestrians, especially if NSFs are found, to avoid a missed and delayed diagnosis. Enhancing vehicle safety features for pedestrians, forbidding driving and walking while intoxicated, investigating local pedestrian injury trends and making progress with public health prevention strategies will play important roles in reducing the risk and severity of crashes32,33. Advance-warning signs of TSFs caused by MVCs may provide information to policy-makers for educational efforts and facilitate the establishment of suitable and effective policies and strategies.

The use of motor vehicles is rapidly increasing in Chongqing, which is a mountainous city. Because of a lack of strict traffic safety regulations, the probability of sustaining a serious trauma caused by MVCs is high. Shenyang is located in the cool northern region of China, extending mainly to the plains, and the frequency at which pedestrian was observed was significantly higher in the SY group. Significant differences were observed in the distributions of age, role, motorcycle, battery electric vehicle, bicycle, taxi, coma after injury, LLFs, PFs, CCI, ITIs, IAIs, complications and SCIs between the CQ group and SY group. A previous study showed that India is a highly populous country with a significant number of powered 2-wheelers in its traffic mix. This mix and the density of both pedestrians and PTWs translate to a high potential for unsafe interactions between the 2 types of road users28. The empirical results that sun glare is a combined spatiotemporal factor associated with pedestrian fatalities may be unique to Taiwan because of its unique sunrise and sunset times and orientations29. Younger patients, especially those with MVCs involving motorcycles in Chongqing, should be given more attention to prevent nerve injuries. In Shenyang, more attention should be given to patients who present with associated injuries for the timely diagnosis and treatment of serious associated injuries.

Limitations

This study had some limitations. First, the retrospective design and the small number of patients may have resulted in selection bias. Second, there was a lack of information about bone mineral density. Despite these limitations, we believe that this valuable epidemiological information can be used as guidance for the prevention of TSFs caused by MVCs.

Conclusions

This study demonstrates the age-, gender-, role- and geographic-specific clinical characteristics of TSFs resulting from MVCs and reveals a significant relationship between different ages, sexes, roles, geographic locations and associated injuries, complications and spinal cord injury.