Traumatic spinal injury-related hospitalizations in the United States, 2016–2019: a retrospective study

Abstract

Background:

Traumatic spinal injury (TSI) is associated with significant fatality and social burden; however, the epidemiology and treatment of patients with TSI in the US remain unclear.

Materials and methods:

An adult population was selected from the National Inpatient Sample database from 2016 to 2019. TSI incidence was calculated and TSI-related hospitalizations were divided into operative and nonoperative groups according to the treatments received. TSIs were classified as fracture, dislocation, internal organ injury, nerve root injury, or sprain injuries based on their nature. The annual percentage change (APC) was calculated to identify trends. In-hospital deaths were utilized to evaluate the prognosis of different TSIs.

Results:

Overall, 95 047 adult patients were hospitalized with TSI in the US from 2016 to 2019, with an incidence rate of 48.4 per 100 000 persons in 2019 (95% CI: 46.2–50.6). The total incidence increased with an APC of 1.5% (95% CI: 0.1–3%) from 2016 to 2019. Operative TSI treatment was more common than nonoperative (32.8 vs. 3.8; 95% CI: 32.3–33.2 vs. 3.6–4%). The number of operations increased from 37 555 (95% CI: 34 674–40 436) to 40 460 (95% CI: 37 372–43 548); however, the operative rate only increased for internal organ injury (i.e. spinal cord injury [SCI])-related hospitalizations (APC, 3.6%; 95% CI: 2.8–4.4%). In-hospital mortality was highest among SCI-related hospitalizations, recorded at 3.9% (95% CI: 2.9–5%) and 28% (95% CI: 17.9–38.2%) in the operative and nonoperative groups, respectively.

Conclusions:

The estimated incidence of TSI in US adults increased from 2016 to 2019. The number of operations increased; however, the proportion of operations performed on TSI-related hospitalizations did not significantly change. In 2019, SCI was the highest associated mortality TSI, regardless of operative or nonoperative treatment.

Introduction

Highlights

• The International Classification of Diseases, Tenth Revision identified traumatic spinal injury (TSI) patients and their treatment.

• TSI patients treated with surgery were less likely to die in hospital than those with nonoperative treatment.

• The proportion and number of spinal cord injury (SCI) patients treated with surgery increased from 2016 to 2019.

• TSI and SCI incidence increased; the incidence of SCI had a significant annual percentage change.

Traumatic spinal injury (TSI) involves fracture, dislocation, spinal cord injury (SCI), nerve root injury, and sprain¹. It is a global public health challenge that 800 000 patients worldwide experience TSIs each year². TSI causes motor and sensory deficits that can lead to disability (e.g. quadriplegia)^3,4. TSI also places a heavy financial burden on the healthcare system, with a 2019 US study reporting that the annual direct cost of a patient with SCI is $50 280 and the total cost of all SCI-related hospitalizations is $15.7 billion⁵.

Although TSI includes injuries not only to the spinal cord and osseous structures but also to the nerve roots and ligamentous structures of the spine¹, existing spine trauma guidelines^6,7 usually only focused on the former, possibly because of a lack of sufficient evidence to support the development of recommendations for other subtypes of TSI. For example, in the United States (US), previous nationally representative TSI studies^8–10 did not include all subtypes of TSI. In addition, the most recent TSI study in the US⁸ used the data up to 2015. To address these issues, our study used data from 2016, included all subtypes of TSI, and provided results from all subtypes in the hope of providing evidence to support future relevant guidelines and a more comprehensive and updated understanding of TSI in the US population overall and by all subtypes.

Operative treatment is common in patients with TSI, especially those with neurological deficits^11–14. Most previous studies on spinal surgery have used the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) and have included only common procedures, such as spinal fusion and laminectomy^15–17, which may lead to an underestimation of operative rates. The ICD-10 Procedure Coding System (ICD-10-PCS) includes nine associated codes and more detailed classification in the procedure (e.g. body part and root operation), which allows more accurate definitions that reflect the patient’s condition and information relevant to treatment compared to ICD-9^18,19.

Thus, this study aimed to estimate the incidence of TSI-related hospitalizations and the proportion of operative treatments among TSI-related hospitalizations overall and by subtypes (i.e. fracture, SCI, dislocation, nerve root injury, and sprain) in 2019 and to describe changes since 2016 in the US.

Materials and methods

Data collection

The National Inpatient Sample (NIS) is part of the Healthcare Cost and Utilization Project (HCUP), sponsored by the Agency for Healthcare Research and Quality. It is the largest publicly available, all-payer inpatient care database in the US. In 2016, the NIS covered more than 97% of the US population and approximated a 20% stratified sample of US community hospital discharges. To facilitate the production of national estimates, discharge weights are provided by the NIS, along with the information necessary to calculate the variance of estimates²⁰.

Information on age, sex, race/ethnicity, ICD-10-CM diagnosis, ICD-10-PCS procedure, length of stay (LOS), death during hospitalization, and total charges were extracted from the NIS and analyzed. Based on the method proposed by the official group, the cost-to-charge ratio from the HCUP²¹ was used to convert charges to costs²². Patients with TSI were classified with ICD-10 codes; whether operative or nonoperative treatments were used was recorded. Other information was gathered to describe the demographic and clinical characteristics of the patients.

To calculate TSI incidence in the US, we accessed the US census data, including the annual estimated resident population from 2016 to 2019. The population data were divided by sex, race, ethnicity (Hispanic or non-Hispanic), single age, and age group²³. TSI incidence was analyzed according to these variables. For the description of the current status, we only used the 2019 data on incidence and clinical characteristics.

The proposed framework for presenting injury data provides a standard framework using ICD-10-CM²⁴. Compared to ICD-9-CM, ICD-10-CM has two advantages in the identification of injury. One is that ICD-10-CM provides clearer identification of two subtypes of TSI (i.e. fracture and SCI), and another is that ICD-10-CM contributes to a more accurate estimation of the incidence of TSI. In ICD-9-CM, fracture is classified as fracture with SCI and fracture without mention of SCI, and SCI is classified as SCI with fracture and SCI without evidence of spinal bone injury. However, in ICD-10-CM, fracture and SCI are identified separately. In addition, ICD-10-CM includes the new medical encounter information (i.e. initial and subsequent medical encounters) for injury patients. The code of initial encounter is used while the patient is receiving active treatment for the condition, and the code of subsequent medical encounters is used for situations after the patient has received active treatment for the condition and is receiving routine care during the recovery period²⁴. Based on a study published by the Centers for Disease Control and Prevention²⁵, the identification of injury cases should be limited to initial encounters only, which contributes to more accurately estimate the incidence of TSI. In the proposed framework, the injury diagnosis codes were classified by nature and body region simultaneously to recognize TSI by the body region of the ʻspine and backʼ. It also described the nature of spinal injuries, noting that TSI included not only spinal cord injuries, but also fractures, dislocations, and other specific injuries (i.e. nerve root injuries or sprains) of the spine. Considering the sequelae code, this framework requested an initial encounter (i.e. the seventh character of A, B, or C) for the injury as well²⁴. Hospitalized patients were included if their principal diagnosis was an ICD-10-CM coded injury²⁶. Patients aged less than 18 were excluded.

Based on these criteria, we included all adult patients with TSI regardless of its nature and collated their detailed ICD-10-CM codes (Supplementary Table 1, Supplemental Digital Content 1, http://links.lww.com/JS9/A927). In 2019, one more variable, ʻinjury ICD-10-CM diagnosis reported on recordʼ²⁷, was included in the NIS to identify injury discharges. This variable was consistent with our criteria.

Treatment

ICD-10-PCS codes were used to identify TSI patients’ treatments and distinguish operative and nonoperative treatments. Beginning in the fourth quarter of 2015, ICD-10-PCS procedures reported on HCUP records were stored instead of ICD-9 procedures²⁸. This transition enabled more detailed information and more specific treatment classification, with 19 times more procedure codes²⁹.

Procedures were only included if they involved surgery on the spine and back (i.e. injuries related to the vertebral column or spinal cord)²⁴. Although the overall coverage of procedures was far too complex, the most common treatments were included; for example common operative treatment procedures included internal fixation, vertebroplasty, kyphoplasty, laminoplasty, spinal fusion, and decompression³⁰. Common nonoperative treatment procedures included physical treatment, traction, pharmacotherapy, and external orthosis and bracing³¹. The complete codes are listed in Supplementary Table 2 and Supplemental Digital Content 2, http://links.lww.com/JS9/A928. Patients who underwent surgery and nonoperative treatment were placed in the operative group so the nonoperative group only consisted of patients who received no operative treatment¹⁷.

Demographic characteristics

Demographic characteristics included sex (male and female), age (18–44, 45–64, 65–84, and ≥85), and race/ethnicity (non-Hispanic White, non-Hispanic African American, Hispanic, Asian or Pacific Islander, and Native American).

Statistical analysis

Stratified sampling weights from the NIS were used to estimate national features. We used strata and cluster variables to calculate standard errors (SEs) and 95% CIs. The annual estimates for the US population by sex, age, race, and Hispanic origin from the US Census Bureau²³ were used to calculate the overall incidence and subgroup incidence. Subgroup analyses were developed with demographic characteristics (i.e. sex, age, and race/ethnicity) in the trend of incidence and outcome after treatment. Based on the reviewer’s suggestion, one additional subgroup analysis was added through classifying fracture as cervical, thoracic, lumbar, and sacral/coccygeal. Incidences were reported as the number of hospitalizations per 100 000 population. As the US Census Bureau modified the race category to assign individuals who selected the ʻSome Other Raceʼ category to an Office of Management and Budget (OMB) race category³², the estimated population lacked the classification of other races compared with the race category of the NIS. Consequently, we calculated the race-stratified incidence rate excluding this race category. Research on traumatic brain injuries has also neglected this category when calculating the incidence by race/ethnicity³³. The annual percentage change (APC) was calculated to estimate trends in TSI incidence rate and treatment. The 95% CI and significant differences were also calculated. In the treatment analysis, the weighted number of cases and proportion of hospitalizations receiving each type of treatment were calculated with SE and 95% CI for five types of injuries and the overall scale. The LOS, cost, and in-hospital mortality were used to evaluate the outcome of TSI-related hospitalizations after operative or nonoperative treatment. Considering the distribution of statistics, the LOS and cost were reported as the median with their interquartile ranges, while in-hospital mortality was calculated with a 95% CI. Multivariate analyses were performed to assess the associations between demographic variables and corresponding outcomes, with linear regression analyses for mean LOS and costs and logistic regression analyses for in-hospital mortality. As both LOS and costs are skewed, a log transformation was carried out prior to the formal analysis³⁴.

To protect the participants’ information, the incidence, number, proportion, and average value analyses were only allowed when there were greater than or equal to 10 cases; otherwise, these were reported as NA. All statistical analyses were completed using SPSS (version 27.0.1.0), Stata (version 15.1), R program (version 4.1.3), and Joinpoint (version 4.9.1.0).

This work has been reported in line with the strengthening the reporting of cohort, cross-sectional, and case–control studies in surgery (STROCSS) criteria³⁵ (Supplemental Digital Content 6, http://links.lww.com/JS9/A932).

Results

The data of 97 096 patients diagnosed with TSI as their primary diagnosis were collected from the NIS database between 2016 and 2019. Overall, 95 047 patients aged 18 years or older were included in the study. The weighted mean age was 65.6 years (SE, 0.1), and 51.6% of hospitalizations were female. A total of 77.7% were non-Hispanic White, 7.8% were non-Hispanic African American, and 8.6% were Hispanic. Regarding injury nature, 84 767 (89.2%) were fractures, 1884 (2%) were dislocations, 7477 (7.9%) were internal organ injuries, 86 (0.1%) were nerve root injuries, and 833 (0.9%) were sprains (Fig. 1).

Figure 1.

Flowchart of extracting traumatic spinal injury-related hospitalizations data from National Inpatient Sample.

Incidence of traumatic spinal injuries

TSI incidence was calculated across the demographic characteristics of age, sex, and race/ethnicity, with distinctive features evident between the types of TSIs. In 2019, the estimated overall incidence of TSI was 48.4 per 100 000 persons (95% CI: 46.2–50.6). The incidence of fractures, dislocations, internal organ injuries, nerve root injuries, and sprains was 42.7 (95% CI: 40.8–44.6), 1 (95% CI: 0.8–1.2), 4.3 (95% CI: 3.9–4.6), 0.06 (95% CI: 0.03–0.08), and 0.4 (95% CI: 0.3–0.4) per 100 000 persons, respectively. Excluding nerve root injuries-related hospitalizations, age-stratified data revealed a higher incidence of TSIs in patients aged 85 years or older, particularly for fracture injuries, where the incidence was over twenty times higher compared to patients aged 18–44 (396.5 vs. 14.5, respectively). There were differences in the sex-stratified data, whereby the incidence of females with fractures was higher but lower among other injury types. The most significant sex-based difference was seen in SCI-related hospitalizations, where the incidence of females was 2.3 per 100 00 persons (95% CI: 2.1–2.6), and the incidence of males almost tripled at 6.3 per 100 000 persons (95% CI: 5.7–6.9). The incidence of fractures was higher among non-Hispanic White hospitalizations (52.5 per 100 000; 95% CI: 49.9–55), and the incidence of other spinal injuries was higher among non-Hispanic African American (Table 1).

Table 1.

Characteristics of traumatic spinal injury-related hospitalizations in 2019, weighted incidence per 100 000 (95% CI).

	Nature of injury
Characteristic	Fracture	Dislocation	Internal organ injury	Nerve root injury	Sprain	Overall
All discharges	42.7 (40.8–44.6)	1 (0.8–1.2)	4.3 (3.9–4.6)	0.06 (0.03–0.08)	0.4 (0.3–0.4)	48.4 (46.2–50.6)
Age
18–44	14.5 (13.4–15.5)	0.8 (0.6–1.1)	2.2 (1.9–2.4)	0.04 (0.03–0.05)	0.2 (0.2–0.3)	17.8 (16.5–19.1)
45–64	26.5 (24.9–28.1)	1.1 (0.8–1.5)	4.7 (4.2–5.2)	0.05 (0.03–0.07)	0.3 (0.2–0.4)	32.7 (30.7–34.7)
65–84	92.2 (88.1–96.2)	0.9 (0.7–1.2)	7.7 (7–8.4)	0.04 (0.02–0.06)	0.5 (0.4–0.7)	101.4 (96.9–105.8)
≥85	396.5 (377.9–415.1)	1.1 (0.5–1.6)	11.7 (9.7–13.6)	NAa	2.3 (1.5–3.2)	411.7 (392.4–430.9)
Sex
Male	40.1 (38–42.2)	1.2 (0.9–1.5)	6.3 (5.7–6.9)	0.07 (0.03–0.1)	0.4 (0.3–0.5)	48 (45.5–50.6)
Female	45.2 (43.3–47.1)	0.8 (0.6–0.9)	2.3 (2.1–2.6)	0.04 (0.02–0.07)	0.3 (0.3–0.4)	48.7 (46.7–50.8)
Race
Non-Hispanic White	52.5 (49.9–55)	0.7 (0.6–0.8)	4.4 (4–4.8)	0.04 (0.03–0.05)	0.3 (0.3–0.4)	58 (55.1–60.8)
Non-Hispanic Black	21.8 (19.5–24.1)	1.9 (1.3–2.4)	6.1 (5.1–7.1)	0.07 (0.04–0.1)	0.5 (0.4–0.7)	30.4 (27.2–33.7)
Hispanic	21.1 (19.1–23.2)	1.1 (0.5–1.7)	2 (1.6–2.3)	NAa	0.3 (0.2–0.4)	24.5 (22.1–26.8)
Non-Hispanic Asian or Pacific Islander	18.6 (16–21.1)	0.5 (0.2–0.9)	2.1 (1.4–2.8)	NAa	0.2 (0.1–0.4)	21.4 (18.2–24.6)
Native American	30.8 (21–40.6)	1.1 (0–2.2)	5.5 (2.7–8.3)	NAa	0.8 (0–1.8)	38.2 (25.8–50.6)

^a Number of patients less than 10 is shown as NA but still included in the overall.

Trends in the incidence of traumatic spinal injuries

Although only a slight increase in the trend of incidence of TSI-related hospitalizations from 2016 to 2019 was seen overall (APC, 1.5%; 95% CI: 0.1–3%), there were more significant changes evident in specific types of TSI. The most evident decrease in hospitalizations was in sprain injuries-related hospitalizations (APC, −5.9%; 95% CI: −9.8to –1.8%). In contrast, increases were observed in SCIs-related hospitalizations (APC, 9.9%; 95% CI: 1.4–19.2%) and it stayed stable in fractures-related hospitalizations (APC, 0.9%; 95% CI: −0.1–1.9%), dislocations (APC, −0.3%; 95% CI: −10.3–10.9%), and nerve root injuries (APC, 19.7%; 95% CI: −15.4–69.3%; Table 2).

Table 2.

Trend of traumatic spinal injury-related hospitalizations, 2016–2019, weighted incidence per 100 000 (95% CI).

	Calendar year (n=unweighted number)
Type	2016 (n=23 611)	2017 (n=23 861)	2018 (n=24 436)	2019 (n=25 188)	APC (95% CI)
Fracture	41.5 (38.9–44.2)	41.7 (39–44.4)	42 (39.3–44.6)	42.7 (40.1–45.4)	0.9 (−0.1–1.9)
Dislocation	0.97 (0.77–1.17)	0.9 (0.72–1.07)	0.9 (0.73–1.07)	0.97 (0.75–1.19)	−0.3 (−10.3–10.9)
Internal organ injury	3.3 (3–3.6)	3.3 (3–3.7)	3.9 (3.5–4.3)	4.3 (3.8–4.7)	9.9a (1.4–19.2)
Nerve root injury	0.03 (0.01–0.04)	0.05 (0.03–0.06)	0.04 (0.02–0.06)	0.06 (0.03–0.08)	19.7 (−15.4–69.3)
Sprain	0.45 (0.37–0.52)	0.43 (0.37–0.49)	0.41 (0.34–0.47)	0.37 (0.31–0.43)	−5.9a (−9.8to−1.8)
Total	46.3 (43.3–49.3)	46.4 (43.4–49.5)	47.2 (44.2–50.3)	48.4 (45.3–51.5)	1.5a (0.1–3)

^a Indicates that the Annual Percentage Change (APC) is significantly different from zero at the alpha=0.05 level.

The rate of spinal fractures-related hospitalizations increased more in the older age group. The APC of patients aged 85 years or older was 1.9% (95% CI: 0.2–3.6%). Conversely, the rate of hospitalization decreased among patients aged 18–44, with an APC of −4.2% (95% CI: −6.3to–2.1%). Considering different fracture configurations, thoracic vertebral fracture increased (APC, 2.3%; 95% CI: 1–3.7%). A significant increase was observed in all subgroups of SCI-related hospitalizations, except among Asian or Pacific Islander and Native American. The incidence of non-Hispanic White dislocation-related hospitalizations decreased (APC, −6.7%; 95% CI: −8.6to–4.8%); however, the incidence of Hispanic dislocation-related hospitalizations increased (APC, 23.8%; 95% CI: 0.7–52.3%). A dramatically increased incidence of back sprains was seen in patients aged 85 years (APC, 16.6%; 95% CI: 4.2–30.5%; Supplementary Table 3, Supplemental Digital Content 3, http://links.lww.com/JS9/A929).

Treatment of traumatic spinal injuries

Operative and nonoperative treatments were compared in terms of number and proportion from 2016 to 2019. Operative treatments increased from 37 555 (95% CI: 34 674–40 436) to 40 460 (95% CI: 37 372–43 548), with a 2.7% increase in APC (0.7–4.8%). Nonoperative treatments increased from 4420 (95% CI: 3853–4987) to 4640 (95% CI: 4049–5231), with a 2% increase in APC (−1.7–5.9%). The proportion of hospitalizations undergoing these treatments was 32.8% (95% CI: 32.3–33.2%) and 3.8% (95% CI: 3.6–4%), respectively, with neither demonstrating a significant change over the studied period.

The proportion of operative treatments varied across TSI types. Dislocation-related hospitalizations (73.6%; 95% CI: 70.5–76.4%) and SCI-related hospitalizations (61.8%; 95% CI: 60.6–62.9%) were more likely to undergo an operation, while sprain-related hospitalizations (8.2%; 95% CI: 6.4–10.3%) were the least likely. The proportion of SCI-related hospitalizations undergoing operative treatments significantly increased (APC, 3.6%; 95% CI: 2.8–4.4%) (Fig. 2), as did the number (APC, 14.8%; 95% CI: 5.3–25.1%). Nonoperative treatment was less common (Supplementary Table 4, Supplemental Digital Content 4, http://links.lww.com/JS9/A930).

Figure 2.

Trends of the proportion of operative treatments among traumatic spinal injury-related hospitalizations, 2016–2019 (* Indicates that the Annual Percentage Change is significantly different from zero at the alpha=0.05 level).

The clinical characteristics of hospitalizations in 2019 who underwent operative and nonoperative treatments were compared. Data on LOS, cost, and in-hospital death were compared across the five TSI injury types. The operative group was associated with increased mean cost and decreased inpatient mortality. Inpatient mortality in the operative treatment group was highest among SCI-related hospitalizations (3.9%; 95% CI: 2.9–5%) and lowest among dislocation-related hospitalizations (1.7%; 95% CI: 0.3–3%) and fracture-related hospitalizations (1.3%, 95% CI: 1–1.6%). SCI-related hospitalizations had the highest mean hospitalization cost. The mean cost of SCI-related hospitalizations who underwent operative treatment was $64 931 (95% CI: $61 629–68 233) and $51 726 (95% CI: $35 950–67 502) for those who underwent nonoperative treatment. Compared to fracture-related hospitalizations who underwent nonoperative treatment, fracture-related hospitalizations who underwent operative treatment had a longer mean LOS [8 vs. 6.2 (95% CI: 7.8–8.2 vs. 5.6–6.7)]. Like the cost findings, the LOS of SCI-related hospitalizations in both the operative and nonoperative groups were the highest among all TSI types (Table 3). The clinical characteristics among different age, sex, and race were compared of different TSI types and were regressed utilizing all variables. The analysis showed some significant differences (e.g. in operative group of fracture and SCI, 65–84 and ≥85 patients were associated with higher mortality compared to 18–44 patients and male was associated with longer LOS, higher cost, and more in-hospital death) (Supplementary Table 5, Supplemental Digital Content 5, http://links.lww.com/JS9/A931).

Table 3.

Clinical characteristics of traumatic spinal injury-related hospitalizations after different treatment in 2019.

	Clinical characteristics
Type	LOS, median days (Q1, Q3)	LOS, mean days (95% CI)	Cost, median $ (Q1, Q3)	Cost, mean $ (95% CI)	Mortality, mean (95% CI)
Fracture
Operative	6 (4–10)	8 (7.8–8.2)	30 079 (17 803–49 148)	39 550 (38 093–41 008)	1.3% (1–1.6%)
Nonoperative	4 (2–7)	6.2 (5.6–6.7)	10 827 (6847–18 941)	17 931 (16 079–19 784)	4% (2.4–5.7%)
Dislocation
Operative	3 (2–7)	5.9 (4.8–7)	28 135 (16 681–42 572)	39 066 (33 963–44 169)	1.7% (0.3–3%)
Nonoperative	5 (3, 13)	6.8 (3.6–9.9)	23 310 (9121–40 037)	31 178 (15 923–46 434)	23.1% (0.6–45.6%)
Internal organ injury
Operative	10 (6–16)	14.5 (13.4–15.7)	49 503 (32 517–79 846)	64 931 (61 629–68 233)	3.9% (2.9–5%)
Nonoperative	8 (4–18)	15.2 (10–20.4)	25 049 (13 432–57 678)	51 726 (35 950–67 502)	28% (17.9–38.2%)
Nerve root injury
Operative	NAa	NAa	NAa	NAa	NAa
Nonoperative	NAa	NAa	NAa	NAa	NAa
Sprain
Operative	5 (3, 10)	9 (1.9, 16.1)	25 776 (21 352–46 481)	40 338 (23 953–56 723)	NAa
Nonoperative	NAa	NAa	NAa	NAa	NAa

^a Number of patients less than 10 is shown as NA but still included in the overall.

Discussion

This study evaluated national trends in the incidence and treatment of TSI in the US from 2016 to 2019 and described the demographic and clinical characteristics of TSI-related hospitalizations as seen in 2019. A trend of increased TSI-related hospitalizations and SCI-related hospitalizations was observed. Furthermore, the number and rate of operative treatments among SCI-related hospitalizations increased. We estimated the incidence of TSI and found that, consistent with previous studies^36–38, spinal fractures were the most common.

For spinal fractures, consistent with a previous study³⁹, the incidence was highest among the elderly, non-Hispanic White, and female populations. One possible reason is that old age and being white and/or female are risk factors for vertebral osteoporosis⁴⁰. For SCIs, the incidence was higher in males, which has been reported in several other studies on SCI^41–44, where a 3–4 times higher incidence rate for males has been reported. The sex distribution of SCI is attributed to males engaging in behaviors that have a higher risk of trauma⁴⁵. Regarding age stratification, patients aged greater than or equal to 85 years had the highest incidence of TSIs; however, only a 2015 NIS study⁴¹ supported this finding. This could be due to differences in the data sources used by other studies. For spinal sprains, the incidence was the highest in patients aged greater than or equal to 85 years. This could be due to bone degeneration and ligament stiffness. Elderly individuals can reduce this risk by ensuring adequate intake of calcium and vitamin D and engaging in appropriate exercise^46,47. Furthermore, these individuals are more likely to get injured by falling due to medication use, cognitive impairment, or sensory deficits^48,49. Therefore, preventive measures are needed to reduce these injuries. In all types of TSI, except spinal fractures, the incidence was highest in non-Hispanic Africans, which may be related to the etiology of injuries among different races/ethnicities, whereby trauma due to violence may be more common in the non-Hispanic African population^42,50,51.

The incidence of TSI demonstrated a slight increase from 2016 to 2019. Conversely, Algahtany et al.³⁷ reported that the incidence of TSIs in emergency departments across 2002–2007 increased by 5.15% per year. In addition, our study reported an increased APC for SCI and no significant change in spinal fractures compared to that study³⁷. These differences may be owing to our study only including hospitalizations from the NIS database between 2016 and 2019; these four years may not represent the actual overall trend. For example, we found that the incidence of SCI increased dramatically from 2017 to 2018, which resulted in a significantly increased APC from 2016 to 2019, which could mislead us into thinking that the incidence of SCI increased rapidly during these 4 years. The finding was inconsistent with a previous GBD study from 1990 to 2016, which reported no obvious increase in TSI incidences⁵². The underlying reason for these differences may be the uneven growth of SCI incidence, which has been presented by Jain et al.⁴¹ The incidence of spinal fractures, sprains, and overall injuries among patients greater than or equal to 85 years increased from 2016 to 2019. One reason for this could be that this population maintained an active lifestyle in old age⁵³.

Similar to previous studies^17,51, operative treatment was more common than nonoperative treatment for TSI-related hospitalizations; however, operation rates varied among different types of TSIs. Operations may be more common than conservative treatments owing to the more sophisticated surgical, anesthetic, and radiographic techniques used^12,30. Furthermore, many studies have reported better outcomes associated with surgical interventions^17,54. From 2016 to 2019, the overall operation rate remained stable as the number of hospitalizations receiving operative treatment and the number of TSI-related hospitalizations increased simultaneously. Though the overall operation rate did not increase, the operative rate for SCI-related hospitalizations did increase. Two other studies involving cervical SCI demonstrated the same trend^11,51. One possible reason for this is the motor function improvement seen after an operation like surgical decompression, as well as the limited role of nonoperative treatment for treating neurological deficits^11,14,55. However, further research is needed to understand the impact of different treatments on TSI.

The mortality of TSI in the nonoperative group was higher than in the operative group. Similar findings have been reported in previous studies on SCIs and fractures^13,17,51. Median cost and LOS were higher and longer, respectively, in the operative group in spinal fracture-related hospitalizations and SCI-related hospitalizations. Daniels et al.¹⁷ compared these three characteristics in axis fractures between operative and nonoperative treatments and reported comparable results. The result of our study still cannot infer a causal relationship between operative treatment and lower mortality, because it did not record the severity of the injury and other aspects of the patient’s condition (e.g. neurological involvement) that might influence the surgeon’s decision to perform surgery^{13,17,30,55,56}. The utilization of operative treatment is also associated with several challenges (e.g. infection, blood loss, damage to other tissues, and higher costs)^30,31,55,57. The development of medical technologies may mitigate some of these challenges and enable better outcomes. Female patients might have better rehabilitation outcomes, as we found lower costs, LOS, and mortality among SCI female patients regardless of treatment, as well as among fracture female patients in the operative group. This could be due to the preventive effect of female sex hormones and genes on trauma⁵⁸.

Limitations

There were several limitations in our study. First, the 2012 redesign of the NIS excluded long-term care hospitals, which primarily affected the statistics related to elderly patients. Therefore, the accuracy estimates of discharge counts, LOS, charges, and mortality were reduced for the older age groups²⁰. Second, the modification of race not only excluded the race classification of ʻOther Raceʼ but reassigned this population to other OMB race categories³². Thus, the incidence rates among each race were underestimated. Third, we did not determine the degree of damage, and the NIS database did not include variables to distinguish treatment effects. Consequently, we could only evaluate the outcomes regarding the clinical characteristics of LOS, in-hospital mortality, and cost, and did not categorize any type of TSI more specifically based on injury severity. Finally, owing to the limited availability of data, we could only analyze the trend over 4 years from 2016 to 2019. Therefore, the acquired APC values are not robust.

Implications for policy and research

Our study estimates the incidence of TSI-related hospitalizations and the proportion in operation among TSI-related hospitalizations overall and by subtypes in 2019 and to describe changes since 2016 in the US. In addition, the prognoses (i.e. LOS and in-hospital mortality) and costs were estimated to evaluate the outcomes of TSI-related hospitalizations after operative and nonoperative treatments in 2019. From 2016 to 2019, the incidence of TSI-related hospitalizations increases significantly, mainly due to a significant increase in SCI-related hospitalizations, indicating the need for more policy efforts to prevent SCI-related hospitalizations. Among all types of TSI, the proportion of operations among SCI-related hospitalizations increases significantly, which may indicate successful implementation of clinical guidelines recommending early operations. Mortality is significantly higher in the nonoperative treatment group compared with the operative treatment group, and current guidelines show a lack of high-quality evidence to support their recommendations for nonoperative treatment of TSI^59–62. Therefore, more relevant research is needed in the future to provide a reference for the management of nonoperative treatment for TSI-related hospitalizations.

Conclusion

The estimated incidence of TSI in US adults increased from 2016 to 2019. The number of TSI operations increased; however, the proportion remained stable. Among all types of TSI, a significant increase in the number and proportion of operative SCI treatments was reported. In 2019, SCI was the most severe TSI type and was associated with the highest LOS, cost, and mortality, regardless of operative or nonoperative treatment.

Ethical approval

None.

Consent

None.

Sources of funding

This study received no funding. Dr Hengxing Zhou was funded by Taishan Scholars Program of Shandong Province-Young Taishan Scholars (tsqn201909197).

Author contribution

J.S., Y., L.C., Z.: concept and design; J.S., Y., F., L.C., Z.: acquisition, analysis, or interpretation of data; J.S., Y., Z., Z., G.: drafting of the manuscript; J.S., Y., D., Z.C., Q.S.: statistical analysis; L.C., Z., F.: administrative, technical, or material support; L.C., Z., F.: supervision. All authors contributed in the critical revision of the manuscript for important intellectual content.

Conflicts of interest disclosure

The authors declare that they have no conflicts of interest.

Research registration unique identifying number (UIN)

1. Name of the registry: not applicable.

2. Unique identifying number or registration ID: not applicable.

3. Hyperlink to your specific registration (must be publicly accessible and will be checked): not applicable.

Guarantor

Hengxing Zhou had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Data availability statement

The data that has been used is confidential. Traumatic spinal injury-related hospitalizations in the United States, 2016–2019: a retrospective study.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Presentation

None.