Background: Comparisons between patients with penetrating spinal cord injury (PSCI) and blunt spinal cord injury (BSCI) are scarce. Purpose: To describe baseline characteristics and neurological and functional outcomes for patients with BSCI and PSCI. Methods: Participants with BSCI (n = 5,316) and PSCI (n = 1,062) were extracted from the Spinal Cord Injury Model Systems database from January 1994 to January 2015. Participant injury and demographic characteristics were recorded. Outcomes were measured using the International Standards for Neurological Classification of Spinal Cord Injury and FIM motor scores. Outcomes for patients with American Spinal Injury Association Impairment Scale (AIS) complete injuries were analyzed separately from incomplete injuries at three time points: acute hospitalization, SCI rehabilitation, and 1-year follow-up. Results: Patients with PSCI compared to those with BSCI were more likely to present with complete injuries (56.8% vs 35.9%; p < .001) and were less likely to undergo spine surgery (19.6% vs 80.6%; p < .001). For incomplete injuries, no significant differences were observed between groups in FIM scores or AIS grade improvement at 1 year. For complete injuries, patients with BSCI showed an increased one-grade (15.7% vs 9.1%; p < .001) and three-grade (5.4% vs 1.9%; p = .014) AIS improvement at 1 year. Multivariate regression analysis demonstrated an independent effect for BSCI on AIS improvement at 1 year (odds ratio [OR], 1.74; 95% CI, 1.13–2.70; C-stat = 0.66). Conclusion: Patient with PSCI had more complete injuries and lower surgery rates. Patients with complete BSCI show greater AIS improvement at 1 year, and incomplete injuries show no difference in neurological improvement between groups. Overall, patients with PSCI demonstrated worse functional outcomes at 1 year.
The injury mechanism in a patient with traumatic spinal cord injury (SCI) can be divided into two major categories: blunt spinal cord injury (BSCI) and penetrating spinal cord injury (PSCI). BSCI includes injury mechanisms such as falls and motor vehicle accidents. BSCI accounts for the vast majority of all SCI1,2 and remains the major focus of outcomes research and clinical practice guidelines in the United States.
By comparison, PSCI includes injury mechanisms such as gunshot wounds and stab wounds. Outcomes for patients with PSCI remain relatively understudied, and no national clinical practice guidelines exist for patients with PSCI.3 The evaluation and treatment of patients with PSCI is based largely upon experience in the BSCI population.3
The rates of fatal and nonfatal firearm injuries in the United States have remained constant since the early 2000s at approximately 6 per 100,000 people and 175 per 100,000 people, respectively.4 The National Spinal Cord Injury Statistical Center estimates approximately 17,000 new cases of SCI each year, with PSCI accounting for approximately 14% of all SCIs overall.1 Over 95% of PSCI is secondary to gunshot wounds.
In this study, we analyzed the Spinal Cord Injury Model Systems (SCIMS) database to describe the epidemiology, treatment, and outcomes of patients with BSCI compared to patients with PSCI. We hypothesized that patients with PSCI would be less likely to have neurological and functional improvement during long-term follow-up.
Materials and Methods
The SCIMS national database was queried to identify all SCI admissions to rehabilitation facilities in the United States participating in the SCIMS program from January 1994 through January 2015. The SCIMS is a national project funded by the US Department of Health and Human Services National Institute on Disability, Independent Living, and Rehabilitation Research (NIDILRR). The project is the largest and longest running prospective, multicenter, longitudinal study of people with SCI following participation in a coordinated system of acute hospital care and SCI rehabilitation.5 Institutions that are designated as SCIMS centers must have access to Level 1 trauma center care, acute spine surgery care, comprehensive inpatient rehabilitation services, and long-term interdisciplinary follow-up and rehabilitation services. Currently there are 14 SCIMS centers and five additional follow-up centers across the United States. SCIMS database inclusion criteria are (1) traumatic SCI that is associated with a motor or sensory deficity, (2) admission to SCIMS center within 1 year of injury, (3) acute hospital care and inpatient rehabilitation received within a participating SCIMS center, and (4) informed consent signed by the patient and/or guardian.
Patient selection and characteristics
We identified all patients with an SCI who were admitted on the day of injury to participating SCIMS centers between January 1994 and January 2015, and we divided these patients into those with BSCI and those with PSCI. BSCI is defined in the SCIMS database as a mechanism of injury that includes motor vehicle accidents, falls, sport/recreational trauma, and so on. PSCI is defined in the SCIMS database as patients with a mechanism of injury that includes gunshot wounds, explosions, stabbing, and impalements. The vast majority of all PSCIs in the SCIMS database (>95%) are secondary to gunshot wounds. All acute hospital-related factors known to influence postdischarge outcomes in SCI patients that are present in the SCIMS database were analyzed including clinical information, demographics, and socioeconomic factors. Race was dichotomized into African American and non–African American. Hispanic ethnicity was collected separately from race. Completeness of SCI was documented using the American Spinal Injury Association Impairment Scale (AIS).6 Patients with complete SCIs as measured by the AIS were coded AIS A and were analyzed separately from patients with incomplete spinal cord injuries coded AIS B through D. The neurological level of injury was recoded into groups as cervical for C1-C8 injuries, thoracic for T1-T11 injuries, and lumbar for T12-L5 injuries for clinical descriptive purposes. The “spinal surgery” variable in the SCIMS database includes both decompression and fusion procedures, and further detailed surgical information is not available. Insurance type was coded as none, private, and government (ie, Medicaid or Medicare) payments types. Education level was recoded into high school or less, college degree or some college, and graduate levels of education.
Outcomes were measured at acute hospital admission, SCI rehabilitation admission, SCI rehabilitation discharge, and at 1-year follow-up time periods. Follow-up AIS grades were obtained at discharge from SCI rehabilitation and at 1-year follow-up only. Changes in AIS grade over time were measured by recoding each AIS alpha score into a numerical score and subtracting the AIS numerical score at SCI rehabilitation discharge and 1-year follow-up from the initial AIS score obtained during acute hospitalization. The FIM motor score was measured at all three follow-up time periods.7 Pain level was recorded on a 10-point scale at 1-year follow-up. The percentage of patients requiring any kind of mechanical ventilation asssistance was recorded at admission and discharge from SCI rehabilitation. The percentages of patients who required rehospitalization, who lived at home, and who died were all measured at 1-year follow-up only. Satisfaction with Life Scale (SWLS)8 and the Craig Handicapp Handicap Assessment Tool (CHART)9 were measured at the 1-year follow-up interview. The SWLS is a Likert scale with scores possible from 5 to 35; higher scores indicate better satisfaction with life. The CHART mesaures level of social participation. The NSCI database includes four of the CHART's subscales; physical independence, mobility, occupation, and social integration. For each scale, the higher the score, the greater the participation in the community. Subjective pain severity at 1 year was measured on a scale from 0 to 10, with 0 meaning no pain and 10 meaning the worst pain.
Patient baseline characteristics and outcomes were compared across BSCI and PSCI groups using Pearson's chi-square tests for categorical variables and Mann Whitney U test for all non-parametric continuous variables. A multivariate logistic regression analysis was performed in forward stepwise fashion to evaluate independent predictors of a one-grade AIS improvement at 1-year follow-up. Predictor variables with p ≤ .1 after bivariate analysis were included in the final model. Receiver operator curves were generated and model fit was assessed by calculating the area under the curve expressed by the C-statistic. P value was set at ≤.05 and all odds ratios (OR) are expressed with a 95% confidence interval (CI). Analyses were performed using IBM SPSS software (version 24.0; IBM, Armonk, NY).
A total of 6,378 SCI admissions were identified in the SCIMS database from 1994 to 2015: 5,316 (83%) patients with BSCI and 1,062 (17%) patients with PSCI. The annual percentages of BSCI and PSCI patients in the SCIMS database remained relatively stable over the previous two decades (Figure 1).
Baseline characteristics differed significantly between patients with BSCI and PSCI (Table 1). Patients with PSCI were younger and more likely to be male, African American, and Hispanic. Significantly more patients with PSCI presented as AIS A complete injuries (56.8% vs 35.9%; p < .001) and most injuries for patients with PSCI occurred at the thoracic spinal levels, whereas most injuries for patients with BSCI occurred at the cervical spinal levels. More patients with BSCI than patients with PSCI underwent surgical intervention during their acute care hospitalization (80.6% vs 19.6%; p < .001). Surgical rates showed a slight increase throughout the study period for both groups (Figure 2). Patients with PSCI were also more likely to have government insurance, less likely to be married or employed, and less likely to have a college education.
Outcomes for patients with BSCI and PSCI differed significantly (Table 2). Median hospital length of stay (LOS) was longer for patients with PSCI (median days, 14 vs 12; p < .001), although rehabilitation LOS was longer for patients with BSCI (41 vs 36; p < .001). FIM motor scores were higher for patients with PSCI upon admission to and discharge from SCI rehabilitation. However, no difference in FIM motor scores was observed at 1-year follow-up. CHART scores at 1 year for physical independence, mobility, occupation, and social integration were better for patients with BSCI. Patients with BSCI had lower median pain scores and higher SWLS scores at 1 year as well.
A larger percentage of BSCI patients experienced an improvement of one AIS grade at 1-year follow-up (27.2% vs 15.9%; p < .001), but no difference between PSCI and BSCI groups was observed for a two- or three-grade improvement (Table 2). Patients with PSCI and BSCI were also similar in the rates of mechanical ventilation, living at home, rehospitalization events, and survival at 1-year follow-up. However, patients with PSCI had lower marriage rates and were less likely to be employed at 1-year follow-up.
Complete SCI outcomes
When outcomes were stratified by completeness of injury, complete BSCI patients had longer rehabilitation stays than complete PSCI patients (49 vs 37 days; p < .001) (Table 3). FIM motor scores were higher for patients with complete PSCI at rehabilitation admission, rehabilitation discharge, and 1-year post injury. However, patients with complete BSCI showed a significantly higher percentage of one- and three-grade AIS improvement at 1-year follow-up. Patients with BSCI also demonstrated better CHART scores for occupation, social integration, and lower pain scores at 1 year. Patients with complete BSCI were also more likely to be married and working at 1-year post injury.
Incomplete SCI outcomes
For patients with incomplete injuries, hospital and rehabilitation LOS were similar between patients with PSCI and incomplete BSCI (Table 4). FIM motor scores were higher for patients with incomplete PSCI at rehabilitation admission, rehabilitation discharge, and 1-year post injury. However, FIM score gains were larger for patients with incomplete BSCI. No differences were observed in the rate of AIS improvement between groups at 1-year follow-up. As with the complete injuries, incomplete BSCI patients had better CHART scores than the incomplete PSCI patients and lower median pain scores as well. Patients with incomplete BSCI were more likely to be married and working at 1-year post injury.
Multivariate analysis overall
Multivariate logistic regression analysis of the entire study population demonstrated that BSCI was an independent predictor for one-grade AIS improvement at 1-year follow-up (OR, 1.74; 95% CI, 1.13–2.70; C-stat = 0.66) (Table 5). In addition, cervical level of injury was an independent predictor for AIS improvement (OR, 1.73; 95% CI, 1.32–2.28; C-stat = 0.66). Complete SCI was an independent predictor of worse AIS improvement at 1 year (OR, 0.26; 95% CI, 0.17–0.39; C-stat = 0.66)
Our results demonstrate that PSCI is significantly more common among young, minority patients who are single, less educated, and more likely to have government insurance such as Medicaid. Injuries are more likely to occur at the thoracic spinal level in patients with PSCI and in the cervical spinal level in patients with BSCI. Patients with PSCI are more likely to present with a complete SCI and are much less likely to undergo surgery.
Patients with complete SCIs showed poor AIS grade improvement regardless of PSCI or BSCI injury mechanism. However, patients with complete BSCIs showed significantly higher rates of one- and three-grade AIS improvement at 1-year follow-up. Patients with incomplete BSCI also showed larger FIM score gains from rehabilitation admission to 1-year follow-up. These findings together suggest greater potential for neurological and functional improvement in patients with BSCI compared with PSCI.
Median FIM scores were higher among patients with either complete or incomplete PSCI. However, this finding likely reflects differences in baseline characteristics between the two groups. BSCI patients had significantly more cervical injuries and therefore would be expected to have lower FIM scores due to higher rates of tetraparesis/tetraplegia in the BSCI group as opposed to paraparesis/paraplegia in the PSCI group. CHART scores and other measures of social integration including employment and marital rates all show worse social outcomes for PSCI patients, which is likely related to baseline sociodemographic differences between the groups.
Overall, our data suggest that patients with either complete or incomplete PSCI show lower rates of neurological recovery and demonstrate worse functional outcomes at 1-year follow-up than patients with BSCI. These findings are consistent with previous studies, which all demonstrate poor neurological and functional outcomes for patients with PSCI and worse outcomes for patients with complete PSCI.3,10–15 The study by Sidu et al represents the largest review of studies to date and demonstrates how small sample size, lack of standardized outcome measures, and variable follow-up has significantly limited our understanding of outcomes in PSCI over several decades of research. None of these studies have compared PSCI and BSCI outcomes directly. Moreover, penetrating injury in a general trauma population is a poor predictor of outcome independent of insurance status and other demographic variables such as age, sex, and race.16 Our study is the only study, of which we are aware, that has shown penetrating injury status to be an independent predictor of poor neurological improvement in SCI as measured by the AIS grade at 1-year follow-up.
Comparisons between PSCI and BSCI populations are rare in the literature and might inform better understanding of treatment options, rehabilitation strategies, and prognosis.3 One recent study compared baseline characteristics between patients with PSCI and BSCI but was limited by small sample size and a lack of outcome measures.17 A study by Putzke et al compared these two populations and found similar worse social outcomes and higher pain scores for patients with PSCI, but the comparison portion of the study was small and did not describe surgical rates or examine neurological improvement.18 With limited information available, national guidelines and most research studies focus on treatment and outcomes for patients with BSCI and do not specify treatment standards for patients with PSCI.19 In fact, well-known studies of surgical timing for acute SCI and blood pressure augmentation in the setting of acute SCI are based solely on a BSCI population.20,21
Most of the literature on treatment for patients with PSCI has focused on the possible neurological or functional benefits of surgical decompression in the setting of PSCI.22–24 Overall, this literature has demonstrated mixed results and is limited by small sample size and lack of long-term follow-up, although indications for surgery remain for patients with progressive neurological decline, persistent CSF leak, or bullet migration.25–27 In contrast, decompressive surgery for BSCI is well-established in the literature and standardized in national guidelines.19
Our results from a national, multicenter database may reflect a knowledge gap in the treatment of PSCI compared with BSCI. About 60% more patients with BSCI had surgery compared with PSCI. This discrepancy may reflect uncertainty over the neurological benefit of surgery for patients with PSCI. However, no studies have examined surgeon's attitudes or regional variations in the surgical treatment of PSCI compared with BSCI, which would help to better explain the difference in surgical rates.
Precisely why neurological and functional outcomes for patients with PSCI are worse than those with BSCI remains unknown. The effect of PSCI on poor outcome is even independent of other known predictors of outcome such as completeness and neurological level of SCI. These findings suggest that standardized treatment for patient with BSCI such as blood pressure augmentation, surgical decompression, and rehabilitation therapies do not have the same effect on patients with PSCI. Future research should focus on novel treatment options for patients with PSCI.
Our study was a retrospective analysis of prospectively collected data and carries several limitations. Study results are limited by selection bias in those patients who were admitted to an SCIMS institution and in those who underwent treatment and rehabilitation, and they may not be generalizable to a population outside the SCIMS. However, our study was large and multicentered, which improves the generalizability of our results. Patients with BSCI represent a more heterogeneous group than patients with PSCI and include a wider age range and high- and low-speed injury mechanisms such as falls or motor vehicle accidents, which may be associated with any differences in outcomes. The majority of 1-year follow-up interviews in the SCIMS database are conducted via telephone without in-person clinical assessment, and so about two-thirds of AIS scores were missing at 1-year follow-up. In contrast, the majority of FIM scores were present in the database at 1-year follow-up since scoring can be completed via telephone interview. The FIM score has known ceiling effects in long-term follow-up of SCI patients, however, and may not be sufficiently sensitive to changes at the upper end of the scale. In addition, we only included patients who were admitted to an SCIMS center on the day of injury, because baseline severity measures such as the AIS are recorded only for these patients.
PSCI is significantly more common among young patients who are single, less educated, and have government-issued insurance. Patients with BSCI are less likely to present with a complete injury and are significantly more likely to undergo surgery. Neurological recovery is poor for patients with complete PSCI and BSCI. However, patients with complete BSCI show greater FIM score gains and patients with incomplete BSCI show improved one- and three-grade AIS recovery at 1-year follow-up.
The SCI Model Systems national database is a multicenter study of the SCI Model System Centers Program and is supported by the National Institute on Disability, Independent Living and Rehabilitation Research (NIDILRR), a center within the Administration for Community Living (ACL), Department of Health and Human Services (HHS). This project was supported by NIDILRR SCI Model System grant 90SI2025. The contents of this article do not necessarily reflect the opinions or views of the SCI Model System Centers, NIDILRR, ACL, or HHS. The authors declare no conflicts of interest.