Abstract
Background
In-hospital bacterial meningitis following cervical spine fusion is an uncommon but potentially devastating complication. Due to its rarity, limited data exist regarding its incidence, associated clinical factors, and impact on hospitalization outcomes. This study aimed to characterize the incidence, clinical associations, and outcomes of bacterial meningitis occurring during the index hospitalization following elective cervical spine fusion using a large national database.
Methods
A retrospective cross-sectional analysis of patients aged ≥18 years who underwent elective cervical spinal fusion between 2002 and 2014 was performed using the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS). Cervical fusion procedures were identified using International Classification of Diseases (ICD)-9-CM procedure codes for anterior (81.02) and posterior (81.03) cervical fusion. In-hospital postoperative bacterial meningitis was identified using ICD-9 diagnosis codes (320.0–320.9) recorded during the index admission. Postoperative cerebrospinal fluid (CSF) leak was identified using ICD-9 diagnosis codes for dural tear and CSF-related complications. Patient characteristics, CSF leak status, surgical approach, length of stay (LOS), hospital charges, and mortality were analyzed. Given the extremely low event rate, regression analyses were considered exploratory and interpreted cautiously.
Results
A total of 325,241 elective cervical fusion admissions were identified, including 296,894 (91.3%) anterior and 28,347 (8.7%) posterior cervical fusion procedures. In-hospital bacterial meningitis occurred in 12 patients (0.004%). Patients with a documented postoperative CSF leak had a higher observed incidence of meningitis compared with those without a CSF leak [0.4% (6/1,390) vs. 0.002% (6/323,851)]. Among patients with CSF leaks, posterior cervical fusion was associated with a higher likelihood of meningitis compared with anterior fusion in exploratory regression analysis [odds ratio (OR) 8.4; 95% confidence interval (CI): 1.44–48.6; P=0.02]. Patients with meningitis experienced longer hospitalizations (19.0±9.9 vs. 1.91±2.4 days; P<0.001), higher hospital charges ($202,739.6±177,448.7 vs. $48,176.8±41,244.4; P<0.001), and higher mortality [2/12 (16.7%) vs. 0.1%].
Conclusions
Bacterial meningitis following cervical spine fusion during the index hospitalization is exceedingly rare but associated with substantial morbidity. A postoperative CSF leak was strongly associated with meningitis occurrence, particularly among patients undergoing posterior cervical fusion. These findings support heightened clinical awareness and early diagnostic evaluation in patients who develop CSF leakage after cervical fusion. Further studies are needed to validate these associations and determine preventive strategies.
Keywords: Cervical spine, spinal fusion, meningitis, cerebrospinal fluid leak (CSF leak), Nationwide Inpatient Sample (NIS)
Highlight box.
Key findings
• There was significantly increased risk of bacterial meningitis among patients with cerebrospinal fluid (CSF) leak vs. without CSF leak (0.4% vs. 0.002%, P<0.05).
• Among patients with CSF leak, posterior approach was associated with higher meningitis risk vs. anterior [odds ratio (OR) 8.4, P=0.02].
• Bacterial meningitis was associated with longer length of stays (19.0±9.9 vs. 1.9±2.4 days, P<0.0001), higher hospital charges ($202,740±177,449 vs. $48,177±41,244, P<0.001), and increased mortality (16.7% vs. 0.1%, P<0.05).
What is known and what is new?
• Patients undergoing cervical spine surgery face higher risks of postoperative bacterial meningitis.
• We have limited knowledge on risk factors associated with postoperative bacterial meningitis due to rarity of complication.
• Our study results show that patients who develop postoperative CSF leak after cervical spine fusion using the posterior approach are at higher risk for developing postoperative bacterial meningitis.
What is the implication, and what should change now?
• Our findings support heightened surveillance and early diagnostic evaluation for meningitis in patients who develop postoperative CSF leaks following cervical spine fusion.
Introduction
Postoperative meningitis, though rare, is a severe complication following cervical spine fusion surgery, often resulting from a dural leak (1,2). Previous studies have reported postoperative meningitis rates ranging from 0.10% to 0.18% following spinal procedures; however, most available literature consists of small institutional series due to the rarity of this complication (3,4). Patients undergoing cervical spine surgery may have unique risks related to complex anatomy, proximity to neural structures, and potential for incidental durotomy (5).
When postoperative meningitis occurs, it may result in prolonged hospitalization, additional interventions, increased healthcare utilization, and significant morbidity (6-9). Diagnosis may be challenging because postoperative patients may not demonstrate the classic clinical triad of fever, neck stiffness, and altered mental status, potentially delaying recognition and treatment (10,11). Therefore, understanding clinical factors associated with this complication may assist surgeons in identifying patients requiring increased surveillance.
Although cerebrospinal fluid (CSF) leakage is recognized as a potential pathway for bacterial invasion of the meninges, the incidence and clinical characteristics of postoperative bacterial meningitis following cervical fusion have not been well characterized at a national level. Furthermore, the relationship between surgical approach, CSF leak, and meningitis occurrence remains unclear.
The purpose of this study was not to develop a predictive model but rather to characterize the incidence, clinical associations, and hospitalization outcomes of in-hospital bacterial meningitis following elective cervical spine fusion using a nationally representative administrative database. We hypothesized that postoperative CSF leak would be associated with increased occurrence of bacterial meningitis and that affected patients would experience increased healthcare utilization and mortality. We present this article in accordance with the STROBE reporting checklist (available at https://jss.amegroups.com/article/view/10.21037/jss-2026-1-0011/rc).
Methods
Database
Data were obtained from the Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS) database from January 2002 through December 2014. The NIS is the largest publicly available all-payer inpatient database in the United States and contains de-identified information regarding patient demographics, diagnoses, procedures, hospital characteristics, length of stay (LOS), and hospitalization charges.
Due to the complex survey design of the NIS, analyses were performed using recommended HCUP methodology incorporating discharge-level weighting, stratification, and clustering variables to generate national estimates and appropriate variance calculations. The 2012 NIS redesign was accounted for according to HCUP recommendations.
Study population and identification of cervical fusion
Patients aged 18 years and older who underwent cervical spinal fusion were identified using International Classification of Diseases (ICD)-9 procedure codes for anterior cervical fusion (81.02) and posterior cervical fusion (81.03). Patients with non-elective admissions or diagnoses inconsistent with elective cervical fusion were excluded as shown in Figure 1.
Figure 1.
Flowchart of patient selection, exclusion criteria, and clinical outcomes among 325,241 patients undergoing elective cervical spine fusion (2002–2014). CSF, cerebrospinal fluid; HCUP, Healthcare Cost and Utilization Project; ICD, International Classification of Diseases.
Definition of in-hospital bacterial meningitis and CSF leak
Given that the NIS does not provide complete temporal sequencing of diagnoses relative to procedures, the outcome was defined as in-hospital postoperative bacterial meningitis during the index hospitalization following cervical fusion. Bacterial meningitis was identified using ICD-9 diagnosis codes 320.0–320.9 recorded in any diagnosis field during the hospitalization. Postoperative CSF leak was identified using ICD-9 diagnosis codes associated with dural tear and CSF-related complications: 349.3, 349.31, 349.39, and 997.09. Due to the inability of administrative coding to confirm microbiologic diagnosis or exact timing of complication onset, residual misclassification remains possible.
Outcomes of interest
The primary outcome was the occurrence of in-hospital bacterial meningitis following elective cervical fusion. Secondary outcomes included: LOS, total hospital charges and inpatient mortality.
Hospital charges were reported rather than healthcare costs because NIS provides charge data and does not directly provide cost estimates without additional cost-to-charge conversion methods.
Statistical analysis
Descriptive statistics were used to characterize patient demographics, surgical approach, CSF leak status, and hospitalization outcomes. Comparisons between groups were performed using appropriate categorical and continuous variable testing. Given that only 12 meningitis events were identified, statistical analyses involving regression modeling were considered exploratory due to potential instability associated with rare-event outcomes.
Binary logistic regression was used to assess the association between individual patient and operative characteristics and the development of in-hospital bacterial meningitis following cervical spine fusion. Exploratory multinomial logistic regression analyses were performed to evaluate associations between surgical approach and meningitis occurrence among patients with CSF leakage while adjusting for clinically relevant demographic variables. The results were interpreted cautiously given the limited number of outcome events. All analyses were performed using IBM SPSS Statistics version 24.0 (IBM Corp., Armonk, NY, USA). Statistical significance was defined as P<0.05.
Ethical consideration
This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The NIS database contains de-identified patient information; therefore, institutional review board approval was not required for this study.
Results
Patient characteristics and incidence of in-hospital bacterial meningitis
A total of 325,241 patients undergoing elective cervical fusion during the study period were identified. Among these patients, 296,894 (91.3%) underwent anterior cervical fusion and 28,347 (8.7%) underwent posterior cervical fusion.
In-hospital bacterial meningitis during the index admission occurred in 12 patients (0.004%). The incidence of meningitis was substantially higher among patients with a documented postoperative CSF leak compared with those without a CSF leak [0.4% (6/1,390) vs. 0.002% (6/323,851)]. Given the limited number of meningitis events, comparisons of demographic characteristics and comorbidities should be interpreted as exploratory (Table 1).
Table 1. Demographic and clinical characteristics of patients undergoing cervical fusion according to in-hospital postoperative bacterial meningitis status [2002–2014].
| Category | Total patients with cervical fusion included in the analysis | Cervical fusion without In-hospital postoperative bacterial meningitis | Cervical fusion with In-hospital postoperative bacterial meningitis | P value† |
|---|---|---|---|---|
| Number of admissions | 325,241 (100) | 325,229 (99.996) | 12 (0.004) | |
| Mean age (years) | 53.35±11.9 | 53.35±11.96 | 55.83±11.57 | 0.47 |
| Sex | ||||
| Male | 155,880 (47.9) | 155,872 (47.9) | 8 (66.7) | >0.05 |
| Female | 169,122 (52.0) | 169,118 (52.0) | 4 (33.3) | >0.05 |
| N/A | 239 (0.1) | 239 (0.1) | 0 (0) | |
| Race | ||||
| White | 215,568 (66.3) | 215,564 (66.3) | 4 (33.3) | <0.05 |
| Black | 22,773 (7.0) | 22,770 (7.0) | 3 (25.0) | <0.05 |
| Hispanic | 12,394 (3.8) | 12,393 (3.8) | 1 (8.3) | >0.05 |
| Asian | 2,936 (0.9) | 2,935 (0.9) | 1 (8.3) | <0.05 |
| Native | 1,046 (0.3) | 1,046 (0.3) | 0 (0.0) | >0.05 |
| Other | 6,083 (1.9) | 6,083 (1.9) | 0 (0.0) | >0.05 |
| N/A | 64,441 (19.8) | 64,438 (19.8) | 3 (25.0) | |
| CSF leak | ||||
| No | 323,851 (99.6) | 323,845 (99.6) | 6 (50.0) | <0.05 |
| Yes | 1,390 (0.4) | 1,384 (0.4) | 6 (50.0) | <0.05 |
| Surgical approach | ||||
| Posterior | 28,347 (8.7) | 28,341 (8.7) | 6 (50.0) | <0.05 |
| Anterior | 296,894 (91.3) | 296,888 (91.3) | 6 (50.0) | <0.05 |
| Mortality | ||||
| Yes | 303 (0.1) | 301 (0.1) | 2 (16.7) | <0.05 |
| No | 324,799 (99.9) | 324,789 (99.9) | 10 (83.3) | <0.05 |
| Elixhauser comorbidity index | ||||
| 0 | 116,663 (35.9) | 116,660 (35.9) | 3 (25.0) | >0.05 |
| 1 | 94,618 (29.1) | 94,615 (29.1) | 3 (25.0) | >0.05 |
| 2 | 62,437 (19.2) | 62,434 (19.2) | 3 (25.0) | >0.05 |
| ≥3 | 49,564 (15.2) | 49,561 (15.2) | 3 (25.0) | >0.05 |
| N/A | 1,959 (0.6) | 1,959 (0.6) | 0 (0.0) | >0.05 |
Data are presented as n (%) or mean ± standard deviation. †, comparisons were conducted using the z-test with p-values adjusted using the Bonferroni method. N/A: missing data. CSF, cerebrospinal fluid.
Clinical associations with in-hospital bacterial meningitis
Patients with a documented postoperative CSF leak demonstrated a strong association with the occurrence of bacterial meningitis during the index hospitalization. In exploratory regression analysis, CSF leak was associated with increased odds of meningitis compared with absence of CSF leak [odds ratio (OR) 163.8; 95% confidence interval (CI): 50.9–526.6; P<0.001].
Posterior cervical fusion was also associated with increased odds of meningitis compared with anterior cervical fusion in unadjusted analysis (OR 6.4; 95% CI: 2.0–20.7; P=0.002). However, because posterior procedures are frequently performed for more extensive pathology, including multilevel disease and deformity correction, this association may be influenced by differences in surgical complexity (Table 2).
Table 2. Clinical factors associated with in-hospital postoperative bacterial meningitis following cervical fusion.
| Variable | Model (binary regression model), OR (95% CI) | P value |
|---|---|---|
| CSF leak status | ||
| No | Ref | |
| Yes | 163.8 (50.9–526.6) | <0.001 |
| Surgical approach | ||
| Anterior approach | Ref | |
| Posterior approach | 6.4 (2.0–20.7) | 0.002 |
Binary regression analysis should be interpreted as exploratory because of the limited number of meningitis events. Odds ratios may be unstable due to the rare-event nature of the outcome. CI, confidence interval; CSF, cerebrospinal fluid; OR, odds ratio.
Among patients with postoperative CSF leakage, posterior cervical fusion remained associated with increased odds of meningitis compared with anterior fusion in exploratory regression analysis adjusting for available demographic variables (OR 8.4; 95% CI: 1.44–48.6; P=0.02). These findings should be interpreted cautiously given the limited number of outcome events (Table 3).
Table 3. Characteristics of patients with postoperative CSF leak according to in-hospital postoperative bacterial meningitis status.
| Variable | Model, OR (95% CI) | P value |
|---|---|---|
| Age | 0.98 (0.91–1.05) | 0.53 |
| Sex | ||
| Female | Ref | |
| Male | 1.52 (0.26–8.9) | 0.64 |
| Race | ||
| White | Ref | |
| Black | 3.46 (0.30–39.9) | 0.32 |
| Other | 4.48 (0.73–27.5) | 0.11 |
| Surgical approach | ||
| Anterior approach | Ref | |
| Posterior approach | 8.4 (1.44–48.6) | 0.018 |
| Elixhauser comorbidity index | ||
| 0 | 1.99 (0.154–25.8) | 0.60 |
| 1 | 2.00 (0.18–22.9) | 0.57 |
| 2 | 3.46 (0.30–39.9) | 0.32 |
| ≥3 | Ref |
Multivariate logistic regression adjusted for age, sex, race, Elixhauser, and approach. Due to the small number of meningitis events among patients with CSF leak, regression estimates should be considered exploratory. CI, confidence interval; CSF, cerebrospinal fluid; OR, odds ratio.
Patients who developed bacterial meningitis demonstrated higher observed rates of several comorbid conditions, including congestive heart failure, diabetes, and pulmonary disease. However, given the limited number of meningitis cases and sparse event distribution, these comparisons should be considered hypothesis-generating rather than definitive associations (Table 4).
Table 4. Distribution of baseline comorbidities among patients undergoing cervical fusion according to in-hospital postoperative bacterial meningitis status.
| Category | Total patients with cervical fusion included in the analysis | Cervical fusion without meningitis | Cervical fusion with bacterial meningitis | P value† |
|---|---|---|---|---|
| Acquired immune deficiency syndrome (AIDS) | 177 (0.1) | 177 (0.1) | 0 (0) | >0.05 |
| Alcohol abuse | 3,393 (1.0) | 3,393 (1.0) | 0 (0) | >0.05 |
| Chronic deficiency anemia | 8,643 (2.7) | 8,642 (2.7) | 1 (8.3) | >0.05 |
| Chronic lung disease | 47,361 (14.7) | 47,361 (14.7) | 0 (0) | >0.05 |
| Coagulation deficiency | 1,911 (0.6) | 1,911 (0.6) | 0 (0) | >0.05 |
| Congestive heart failure | 3,565 (1.1) | 3,564 (1.1) | 1 (8.3) | <0.05 |
| Depression | 39,416 (12.2) | 39,416 (12.2) | 0 (0) | >0.05 |
| Diabetes mellitus, uncomplicated | 42,767 (13.2) | 42,766 (13.2) | 1 (8.3) | >0.05 |
| Diabetes mellitus, complicated | 3,443 (1.1) | 3,441 (1.1) | 2 (16.7) | <0.05 |
| Drug abuse | 2,591 (0.8) | 2,591 (0.8) | 0 (0) | >0.05 |
| Fluid and electrolyte disorder | 7,755 (2.4) | 7,755 (2.4) | 2 (16.7) | <0.05 |
| Hypertension | 131,793 (40.8) | 131,789 (40.8) | 4 (33.3) | >0.05 |
| Hypothyroidism | 25,785 (8.0) | 25,784 (8.0) | 1 (8.3) | >0.05 |
| Liver disease | 2,776 (0.9) | 2,776 (0.9) | 0 (0) | >0.05 |
| Neurologic disorder | 10,311 (3.2) | 10,310 (3.2) | 1 (8.3) | >0.05 |
| Obesity | 28,260 (8.7) | 28,260 (8.7) | 0 (0) | >0.05 |
| Solid tumors without metastasis | 1,371 (0.3) | 1,370 (0.3) | 1 (8.3) | <0.05 |
| Metastatic cancer | 540 (0.2) | 540 (0.2) | 0 (0) | >0.05 |
| Lymphoma | 551 (0.2) | 551 (0.2) | 0 (0) | >0.05 |
| Paralysis | 3,767 (1.2) | 3,764 (1.2) | 3 (25.0) | <0.05 |
| Peripheral vascular disease | 3,764 (1.2) | 3,764 (1.2) | 0 (0) | >0.05 |
| Psychiatric disorder | 6,400 (2.0) | 6,400 (2.0) | 0 (0) | >0.05 |
| Pulmonary circulatory disorder | 789 (0.2) | 789 (0.2) | 1 (8.3) | <0.05 |
| Renal failure | 3,885 (1.2) | 3,885 (1.2) | 0 (0) | >0.05 |
| Rheumatoid arthritis and/or collagen vascular disease | 7,837 (2.4) | 7,837 (2.4) | 0 (0) | >0.05 |
| Valvular heart disease | 6,904 (2.1) | 6,904 (2.1) | 0 (0) | >0.05 |
| Weight loss | 846 (0.3) | 846 (0.3) | 0 (0) | >0.05 |
Data are presented as n (%). †, comparisons were conducted using the z-test with P values adjusted using the Bonferroni method. Comorbidity comparisons are exploratory due to the low number of meningitis events. Descriptive differences should be interpreted cautiously.
Among patients with CSF leakage, congestive heart failure was the only comorbidity demonstrating a statistically significant difference between groups. These findings require validation in larger clinical datasets (Table 5).
Table 5. Distribution of baseline comorbidities among patients with postoperative cerebrospinal fluid leak according to in-hospital postoperative bacterial meningitis status.
| Category | Total patients with cervical fusion with CSF leak | Cervical fusion without meningitis | Cervical fusion with bacterial meningitis | P value† |
|---|---|---|---|---|
| Acquired immune deficiency syndrome (AIDS) | 0 (0.0) | 0 (0.0) | 0 (0.0) | – |
| Alcohol abuse | 11 (0.8) | 11 (0.8) | 0 (0.0) | >0.05 |
| Chronic deficiency anemia | 63 (4.6) | 63 (4.6) | 0 (0.0) | >0.05 |
| Chronic lung disease | 242 (17.5) | 242 (17.6) | 0 (0.0) | >0.05 |
| Coagulation deficiency | 20 (1.4) | 20 (1.5) | 0 (0.0) | >0.05 |
| Congestive heart failure | 27 (2.0) | 26 (1.9) | 1 (16.7) | <0.05 |
| Depression | 201 (14.5) | 201 (14.6) | 0 (0.0) | >0.05 |
| Diabetes mellitus, uncomplicated | 261 (18.9) | 261 (19.0) | 0 (0.0) | >0.05 |
| Diabetes mellitus, complicated | 21 (1.5) | 21 (1.5) | 0 (0.0) | >0.05 |
| Drug abuse | 11 (0.8) | 11 (0.8) | 0 (0) | >0.05 |
| Fluid and electrolyte disorder | 114 (8.2) | 113 (8.2) | 1 (16.7) | >0.05 |
| Hypertension | 701 (50.7) | 699 (50.8) | 2 (33.3) | >0.05 |
| Hypothyroidism | 141 (10.2) | 140 (10.2) | 1 (16.7) | >0.05 |
| Liver disease | 14 (1.0) | 14 (1.0) | 0 (0.0) | >0.05 |
| Neurologic disorder | 55 (4.0) | 55 (4.0) | 0 (0.0) | >0.05 |
| Obesity | 207 (15.0) | 207 (15.0) | 0 (0.0) | >0.05 |
| Solid tumors without metastasis | 6 (0.4) | 6 (0.4) | 0 (0.0) | >0.05 |
| Metastatic cancer | 3 (0.2) | 3 (0.2) | 0 (0.0) | >0.05 |
| Lymphoma | 3 (0.2) | 3 (0.2) | 0 (0.0) | >0.05 |
| Paralysis | 87 (6.3) | 85 (6.2) | 2 (33.3) | <0.05 |
| Peripheral vascular disease | 35 (2.5) | 35 (2.5) | 0 (0) | >0.05 |
| Psychiatric disorder | 31 (2.2) | 31 (2.3) | 0 (0) | >0.05 |
| Pulmonary circulatory disorder | 18 (1.3) | 18 (1.3) | 0 (0.0) | >0.05 |
| Renal failure | 32 (2.3) | 32 (2.3) | 0 (0.0) | >0.05 |
| Rheumatoid arthritis and/or collagen vascular disease | 47 (3.4) | 47 (3.4) | 0 (0.0) | >0.05 |
| Valvular heart disease | 30 (2.2) | 30 (2.2) | 0 (0.0) | >0.05 |
| Weight loss | 22 (1.6) | 22 (1.6) | 0 (0.0) | >0.05 |
Data are presented as n (%). †, comparisons were conducted using the z-test with P values adjusted using the Bonferroni method. Because of the limited number of meningitis cases in this subgroup, these analyses are descriptive and hypothesis-generating. CSF, cerebrospinal fluid.
Hospitalization outcomes in patients developing postoperative bacterial meningitis after cervical fusion
Patients who developed in-hospital bacterial meningitis experienced significantly longer hospitalizations compared with patients without meningitis (19.0±9.9 vs. 1.91±2.4 days; P<0.001). Hospital charges were also substantially higher among patients with meningitis ($202,739.6±177,448.7 vs. $48,176.8±41,244.4; P<0.001). Mortality occurred in two of 12 patients with meningitis (16.7%) compared with 0.1% among patients without meningitis (P<0.05). Given the small number of events, mortality estimates should be interpreted with caution (Table 6).
Table 6. In-hospital outcomes among patients undergoing cervical fusion according to postoperative bacterial meningitis status.
| Hospitalization outcome | Cervical fusion without bacterial meningitis (%) | Cervical fusion with bacterial meningitis (%) | P value |
|---|---|---|---|
| Length of stay (days) | 1.91±2.4 | 19.0±9.9 | <0.001 |
| Total hospital charges (Dollars) | $48,176.8±41,244.4 | $202,739.6±177,448.7 | <0.001 |
| In-hospital mortality | 301 (0.1) | 2 (16.7) | <0.05 |
Data are presented as n (%) or mean ± standard deviation. Mortality estimates should be interpreted cautiously because deaths occurred in only two patients with meningitis.
Discussion
Postoperative bacterial meningitis after cervical spine fusion is an uncommon but potentially devastating complication associated with substantial morbidity and mortality. Previous studies have reported an incidence ranging from 0.10% to 0.18% following spinal surgery, although these estimates vary depending on the population studied and the inclusion of different spinal procedures (3,4). The majority of postoperative meningitis cases are believed to result from direct communication between the surgical field and CSF spaces, most commonly in the setting of incidental durotomy or persistent CSF leakage (12). Despite its rarity, postoperative meningitis remains clinically important because delayed recognition may result in severe neurological consequences, prolonged hospitalization, and increased healthcare utilization.
The diagnosis of postoperative bacterial meningitis can be challenging because clinical manifestations may overlap with other postoperative inflammatory conditions, including aseptic or chemical meningitis (13). Furthermore, patients may not demonstrate the classic triad of fever, altered mental status, and neck stiffness, potentially delaying diagnosis even among patients with recognized risk factors (11,14). Differentiating bacterial from aseptic meningitis remains essential because bacterial meningitis requires urgent antimicrobial therapy, whereas aseptic meningitis is often self-limited (15). Although CSF culture remains the diagnostic standard, sensitivity may be reduced after antibiotic exposure (9,16,17). Additional biomarkers, including CSF lactate, have been investigated; however, their diagnostic accuracy remains variable and insufficient to completely replace clinical assessment (18). Given these diagnostic limitations, identifying clinical circumstances associated with postoperative meningitis may improve early recognition and management.
In this nationwide analysis of 325,241 elective cervical fusion procedures, in-hospital postoperative bacterial meningitis during the index admission was exceedingly rare, occurring in only 12 patients (0.004%). The primary clinical association identified was postoperative CSF leak. Patients with a documented CSF leak demonstrated a markedly higher likelihood of meningitis compared with patients without CSF leakage. This finding is biologically plausible, as CSF leakage may provide a pathway for bacterial migration from the surgical wound into the central nervous system. Previous studies have similarly identified dural tears and CSF leaks as important contributors to postoperative infectious complications following spine surgery (1,5). However, because of the extremely low number of meningitis events in our cohort, the magnitude of association should be interpreted cautiously and should not be considered a definitive predictive estimate.
Among patients with postoperative CSF leakage, posterior cervical fusion was associated with a higher occurrence of meningitis compared with anterior cervical fusion. This finding should be interpreted within the broader clinical context of cervical surgical decision-making. Posterior cervical fusion is frequently performed for more extensive pathology, including multilevel degenerative disease, cervical deformity, instability, and conditions requiring broader decompression. These procedures may involve greater soft tissue dissection, larger operative fields, and increased potential for wound-related complications compared with many anterior cervical procedures. Prior studies have reported higher overall complication rates following posterior cervical decompression and fusion, although these differences may reflect both surgical approach and the complexity of the underlying pathology (19). Importantly, the NIS database does not provide detailed operative characteristics, including number of fused levels, revision status, extent of decompression, instrumentation details, or operative duration. Therefore, the observed association between posterior approach and meningitis may partly reflect differences in surgical complexity rather than the approach itself.
The clinical implications of this study should be interpreted appropriately. This analysis does not establish a predictive model or identify interventions proven to prevent postoperative meningitis. Rather, the findings identify CSF leakage, particularly following complex cervical fusion procedures, as a clinical scenario requiring increased awareness. Patients with postoperative CSF leaks may benefit from closer neurological monitoring, careful evaluation of concerning symptoms, and prompt diagnostic investigation when meningitis is suspected. Given the rarity of this complication, large prospective studies or multicenter registries would likely be required to determine whether specific preventive strategies can reduce its occurrence.
This study has several important limitations. First, the retrospective nature of the NIS database limits clinical granularity and introduces potential misclassification. Because NIS captures diagnoses during hospitalization, our analysis reflects in-hospital postoperative bacterial meningitis diagnosed during the index admission and does not capture cases presenting after discharge or during subsequent readmission. Therefore, the true incidence of postoperative meningitis after cervical fusion may be underestimated. Additionally, the database does not provide complete temporal sequencing between the surgical procedure and diagnosis for all years analyzed, and residual misclassification remains possible.
Second, the extremely low number of meningitis events (12 cases) substantially limits statistical power for multivariable analyses. Although the large overall sample size provides a robust denominator for estimating the rarity of this complication, logistic regression reliability depends primarily on the number of outcome events rather than total cohort size. With only 12 events, ORs may be unstable, CIs may be wide, and associations should be considered exploratory rather than definitive. Similarly, mortality findings should be interpreted cautiously, as the reported mortality rate represents only two deaths among 12 affected patients.
Third, important operative variables associated with CSF leakage and postoperative infection risk are unavailable within the NIS database. These include the presence and extent of decompression, number of operative levels, revision surgery, intraoperative dural repair techniques, operative duration, and surgeon-specific factors. These limitations may introduce unmeasured confounding, particularly regarding the relationship between posterior approach and meningitis risk.
Finally, identification of meningitis and CSF leak relied on ICD-9 diagnosis codes, which may be subject to coding inaccuracies. Although administrative databases allow evaluation of rare complications across large populations, they lack microbiological confirmation, clinical examination findings, and laboratory data necessary to distinguish bacterial from aseptic or chemical meningitis with certainty.
Despite these limitations, this study represents one of the largest evaluations of postoperative bacterial meningitis following cervical fusion and provides important epidemiologic information regarding this rare complication. The findings highlight CSF leakage as an important clinical marker associated with postoperative meningitis and emphasize the need for heightened vigilance and early recognition in affected patients. Future prospective studies are needed to validate these associations and determine strategies to reduce morbidity associated with this uncommon but serious complication.
Conclusions
Postoperative bacterial meningitis following cervical spine fusion is an exceptionally rare in-hospital complication. Patients who develop postoperative CSF leakage, particularly after posterior cervical fusion procedures, represent a population warranting increased clinical surveillance and prompt evaluation for infectious complications. Due to the rarity of this event, these findings should be considered hypothesis-generating and require validation in future studies.
Supplementary
The article’s supplementary files as
Acknowledgments
None.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The NIS database contains de-identified patient information; therefore, institutional review board approval was not required for this study.
Footnotes
Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-2026-1-0011/rc
Funding: None.
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-2026-1-0011/coif). The authors have no conflicts of interest to declare.
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