Northwest China is an economically backward region in China with low coverage of health insurance and educational level, but it is still developing rapidly. A large number of people are engaged in traditional manual labor or industrial production. Traffic factors and falls are both important injury factors for TSCI in labor force (industry, agriculture and husbandry). In the past, we have conducted single-center studies  However, despite its under-development with low population density, the total area of five provinces in northwest China is nearly 3.08 million square kilometers, which is a vast area covers about 1/3 land area of China. In order to get timely treatment, local patients usually choose a nearby medical center. Therefore, multi-center study in multiple regions can better represent the whole region than single-center research. We collected the data of patients with TSCI admitted to 14 hospitals located in QH, SN-N, SN-C, SN-S to understand the changes in the incidence of spinal cord injury patients before and after the emergence of COVID-19 (2017-2020). It can optimize the allocation of medical resources then provide timely healthcare to the population of more areas.
Annual count result demonstrated an increasing trend in TSCI patient count from 2017 to 2019, This trend is consistent with previous research findings.[6, 15, 16] Unusually, the patient count in 2020 was significantly lower than the previous year, there were 12.8% fewer patients in 2020 than in 2019. We speculate that this is due to the shutdown and some "work-at-home" proposals implemented by the Chinese government in the first two quarters of 2020 to prevent the COVID-19 epidemic. Recent studies of other traumatic diseases have reached similar conclusions.[17–19] In addition, from the perspective of patients from urban or rural areas, the impact of these policies on urban population is far greater than that of rural population, the number of patients in urban population in 2020 is only 53.3% of the last year, while the number of patients in rural areas in 2020 is still increasing compared with the previous year. We consider this to be related to the feasibility of shutdown policies and "work-at-home" proposals. In cities, where there are more office workers and students, it is easier to work or study online, which largely shields them from the exposure of many outdoor injury factors, while agricultural or livestock production is hard to move online. Another indication is that the proportion of patients aged over 60 in 2020 shows a significant increase. Due to bone degenerative changes and hypofunction of sensory and motor, non-traffic and low-energy injury factors are more likely to cause TSCI in elderly people Compared with young and middle-aged people. [20, 21] Combined with the epidemic policy mentioned earlier, this evidence is consistent with our conclusions. Although the COVID-19 pandamic brings immeasurable economic losses and damages human health, it also facilitates the development of online work and learning, which makes it possible for many jobs to be performed online at home for a long time. From our conclusion, promoting online office work and learning will make a lot of sense to reduce the incidence of traumatic diseases among people at labor age, especially for urban resident.
In our investigation, the male to female ratio in patients with TSCI was 3.67:1, it is similar to the rate reported in other regions. [6, 14, 22] This indicates that most of the patients with TSCI are male. This can be attributed to the fact that most workers in dangerous, physically demanding jobs are male, and that a greater proportion of drivers are male, too.
Most of the injuries were in the 21-40 age group (49.9%, 1309 cases), followed by the ≥61 age group (24.9%, 652 cases) and 41-60 age group (20.9%,547 cases). There are two age groups with high incidence. Such a "bimodal" trend seems to be different from the conclusions of previous studies. Most of the previous literatures described a "unimodal" trend with the highest age group around 40±10 years old. [6, 23, 24] This may be due to the difference in group spacing and the increased incidence of the elderly under the 2020 epidemic policy. The mean age of patients in our data was 48 (±14.9), which was higher than the domestic average age and global average age given by previous literatures. [10, 25] We estimate that this result may be influenced by the aging of society and the policy of delaying retirement time.
Our study also revealed the etiology of the patients with TSCI in Northwest China, included high falls (41.0%), traffic (23.9%), sports (2.6%), low fall (27.7%), high fall (38.8%) and other violence (7.0%). Groups were observed according to age firstly, we find that high energy injury factors, such as high fall, were the most common cause of TSCI in 21-40 and 41-60 age groups, accounting for 45.2% and 37.1%, respectively and for people over 60 years old, low energy factors, such as low falls or slips, accounted for 45.9% of the total cases. This is consistent with the conclusion of the study in Guangdong province.  Then groups were observed according to gender, result indicated that male group was more likely to have high energy factors causing TSCI.
Integrate the above etiological results, the age of high incidence of TSCI is still dominated by the labor age, especially male. So the labor security agencies of governments and the employers of workers should also strengthen labor safety measures and enhance safety education for employees.  In addition, the specialization and mechanization of agricultural and animal husbandry workers should be promoted so that dangerous and strenuous manual labour can be left to machines as far as possible.
Spinal cord injury is usually associated with spinal cord injury, and the levels of injury are corresponding. We counted the segments of the patient's vertebra and the types of fractures, it is the same as the previous literature, the proportions of injuries in cervical, thoracic and lumbar vertebra were similar, and the high incidence of spinal fracture caused by TSCI in each part was C5-C6, T11-T12, and L1-L2. The distribution of injury segments showed a "bimodal" distribution with C6 and L1 as the centers, with 1-2 adjacent segments. [23, 26] On the whole, the T11-L3 segment had the highest proportion of injuries, with a total of 1397 cases, accounting for 42.6% of all injured cases. The main fractural types of cervical, thoracic and lumbar vertebrae are also different, which is related to their anatomical structure and mechanical characteristics.
From the severity of the injury and the outcome of treatment, our results reveal a less optimistic condition after treatment. As a result of consensus, incomplete injury (72.8%) occurred more often than complete injury (27.2%). Given the large number of patients with incomplete TSCI, this issue should be the focus of basic research related to neural regeneration, such as "how to promote the compensation of surviving neurons in the injured area" or "how to achieve differentiation of uninjured stem cells into neurons in the incomplete injured segment".  ASIA scale of most patients did not change before and after treatment both in operational group (71.6%) or conservative group (80.6%). This illustrates the importance of prevention in improving tertiary prevention measures and rehabilitation techniques as an important guarantee of improved treatment outcomes. Moreover, the patients who were treated operationally had a higher improvement rate (22.4%) and deterioration rate (0.5%) than the patients who were treated conservatively (improvement rate is 11.6%, deterioration rate is 0.0%). Therefore, improving surgical methods on the basis of reducing postoperative complications is also a strategy to improve the efficacy of TSCI.
Our study also focused on urban-rural differences that had not previously been noticed by investigators. The annual difference in the number of cases was mentioned earlier, and we also compared the length of time between the onset and the treatment of patients in urban and rural areas. From our results, we can see that almost all urban residents can rush to the hospital for emergency treatment after get injured immediately (<1 h), whereas by the time most patients from rural areas arrive at the hospital for treatment, it has been 4 to 7 hours since they were injured. This reflects the delay in the treatment of patients caused by poor transport conditions in rural areas. In fact, some hospitals in developed areas are already using helicopter emergency medical service (HEMS) to save treatment time for patients in remote areas.  This kind of traffic measure is not restricted by the topography and is of great significance for patients with various acute diseases in rural areas such as the Loess Plateau and the Qinghai-Tibet Plateau in Northwest China. The problem is the high cost of HEMS, which also requires better allocation of resources and funding by the public health system.
Finally, we estimated the incidence of TSCI in Northwest China based on the hospital coverage population from 2017 – 2020, the incidence ranged from 112.2 to 152.4 cases per million people. That is higher than 23.7 per million people in Tianjin and 60.6 per million people in Beijing. [29, 30] The incidence of TSCI is difficult to calculate due to the unpredictability of the occurrence of trauma. Sampling methods, inclusion criteria, regional demographic differences and other factors will affect the results. Our estimated results only provide a reference for the incidence of TSCI in northwest China, and more scientific design and observational studies are needed to accurately obtain its incidence.
However, as a retrospective study, there are irreparable misrecords or incomplete information in the data we obtained, which may lead to deviation between our results and the actual situation. Furthermore, we ignore the data of treatment cost and medicare coverage, which can well reflect the economic pressure of patients and the development level of the region. Therefore, there is insufficient evidence in some descriptions of the severity of TSCI in Northwest China.