SPINE Volume 39, Numher 8, pp 673-677 ©2014, Lippincott Williams & Wilkins
Cerebral Vascular Accidents After Lumbar Spine Fusion Alejandro Marquez-Lara, MD, Sreeharsha V. Nandyala, BA, Steven J. Fineberg, MD, and Kern Singh, MD
Study Design. Retrospective cohort. Objective. To determine the impact of a cerebral vascular accident (CVA) after lumbar spinal fusion, a population-based database was analyzed to identify the incidence, potential risk factors, hospital resource utilization, and the early postoperative outcomes. Summary of Bacitground Data. A lumbar fusion (LF) is an effective surgical procedure to treat lumbar degenerative pathology. Although rare, a CVA can be a catastrophic event after an LF. Methods. The Nationwide Inpatient Sample database was queried from 2002-2011. Ffetients undergoing an elective anterior lumbar fusion, a posterior lumbar fusion, or a combined anteriorposterior lumbar fusion were separated into subcohorts. F^tients with a documented postoperative CVA were identified. Patient demographics, comorbidities (Charlson Comorbidity Index), length of stay, costs, early postoperative outcomes, and mortality were assessed. Statistical analysis involved 7 tests, x' analysis, and binary logistic regression with P < 0.001 denoting significance. Results. A total of 264,891 LFs were identified between 2002 and 2011 of which 340 (1.3 per 1000) developed a postoperative CVA. Patients with a CVA were significantly older and demonstrated a greater comorbidity burden (Charlson Comorbidity Index). Patients with a CVA incurred a significantly greater length of stay, total hospital costs ($41,454 vs. $25,885), and a greater mortality rate (73.7 vs. 0.8 per 1000 patients). Regression analysis demonstrated that age more than 65 years and a history of neurological disorders, paralysis, congestive heart failure, or electrolyte imbalance were associated with an increased risk of a postoperative CVA. Conclusion. Patients who developed a postoperative CVA demonstrated a significantly greater incidence of postoperative complications, mortality, and total hospital costs. This study From the Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL. Acknowiedgment date: August 6, 2013. Revision date: November 20, 2013. Acceptance date: December 16, 2013. The manuscript submitted does not contain information ahout medical device(s)/drug(s).
highlights important associated risk factors (e.g., age more than 65, neurological disorders, congestive heart failure) that may enable surgeons to identify high-risk patients prior to surgery. Further studies are warranted to characterize these risk factors and to establish guidelines to mitigate the complications associated with a postoperative CVA. Key words: Nationwide Inpatient Sample database, cerebral vascular accident, lumbar fusion, postoperative complications, hospital costs, length of stay, short-term outcomes.
Level of Evidence: 4 Spine 2014;39:673-677
he estimated in-hospital costs associated with a cerebral vascular accident (CVA) are $31.8 billion per year. This figure represents nearly half of all direct and indirect CVA-related costs in the United States ($65.5 billion).' Although rare, a postoperative CVA is a devastating complication after a lumbar fusion (LF).--' In the published literature, the reported incidence of a postoperative CVA ranges from 0.2 to 10.2 per 1000 cases.^-^-"' However, most studies are limited due to the small sample sizes and the variability of the study designs. LFs have demonstrated good clinical outcomes for the management of degenerative pathology.'^" However, several authors have reported risk factors associated with major postoperative complications after lumbar spine surgery.^-'"•''' These risk factors include advanced age (>65 yr), preoperative comorbidities, and complex procedures. However, there is little evidence to support the specific association of these risk factors to a postoperative cerebrovascular event. As such, the purpose of this study was to use a populationbased database to better define the incidence, patient characteristics, hospital costs, and short-term outcomes associated with a postoperative CVA after an LF in the United States.
No funds were received in support of this work.
MATERIALS AND METHODS
Relevant financial activities outside the submitted work: board membership, consultancy, royalties.
The Nationwide Inpatient Sample (MS) database, developed by the Healthcare Cost and Utilization Project under the Agency for Healthcare Research and Quality, represents the largest available health care database in the United States." The database collects entries from nearly 8 million hospital admissions annually from more than 1000 hospitals, representing an approximate 20%
Address correspondence and reprint requests to Kern Singh, MD, Department of Orthopaedic Surgery, Rush University Medical Center, 1611 W. Harrison St, Suite 300, Chicago, IL 60612; E-mail: [email protected]
DOI: 10.1097/BRS.0000000000000197 Spine
Stratified sample of all US hospitals.'^ The MS provides all of the diagnoses and procedures performed during each admission through the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) coding system.
Data Collection The M S database was queried from 2002-2011. Patients who underwent an anterior lumbar fusion (ALF, 81.06), a posterior lumbar fusion (PLF, 81.08), or an anterior-posterior lumbar fusion (81.06 and 81.08) were identified. To isolate only lumbar procedures, patients were further stratified using ICD-9-CM coding for degenerative pathologies of the lumbar spine including: lumbar radiculopathy, herniated nucleus pulposus, degenerative disc disease, and lumbar spinal stenosis. Patients who developed a postoperative CVA were identified (997.02) and separated into groups within each stratified surgical procedure. Patients younger than 18 years were excluded from this analysis. Patient demographics, comorbidities, length of stay (LOS), postoperative outcomes, hospital costs, and mortality were compared between the stratified study groups. At the time of this study the hospital cost to charge ratio were not available for 2011. Therefore, the cost analysis refiects the data from 2002-2010. Comorbidities were calculated using a previously described modified Charlson Comorbidity Index.'*"''
Data Analysis Statistical analysis was performed with SPSS version 20 (IBM; Armonk, NY). Statistical differences between discrete variables were compared with independent sample T tests or 1-way analysis of variance and categorical data were evaluated with x^ tests. Factors associated with the development of a postoperative CVA were identified with a binary logistic regression analysis using a 95% confidence interval (CI). In addition, the risk for a postoperative CVA, with a 95% CI, was assessed for each age group ( 1 8 ^ 4 , 45-64, 65-74, and >75). The MS's large sample size allowed for significance criteria of F s 0.001. This strict level of significance has been used by previously published studies from the MS data.^""^^
RESULTS There were a total of 264,891 LFs identified in the M S database from 2002 to 2011, of which 26,267 (9.9%) were ALFs, 215,019 (81.2%) were PLFs, and 23,605 (8.9%) were anterior-posterior lumbar fusions. Overall, there were 340 (1.3 per 1000 cases) patients who developed a postoperative CVA (Table 1). Patients with a postoperative CVA were significantly older (64.4 vs. 55.0) and demonstrated a greater comorbidity burden (Charlson Comorbidity Index: 4.03 vs. 2.51) than unaffected patients (Table 1). The procedure specific incidences of a CVA were 0.4, 1.5, and 0.7 per 1000 cases for the ALF, PLF, and anterior-posterior lumbar fusion cohorts, respectively (Table 2). The reported incidence of a CVA in PLF-treated patients demonstrated to be significantly greater than those in other surgical approaches (Table 3). Patients who developed a postoperative cerebrovascular event underwent a greater proportion of complex cases 674
Cerebral Vascular Accidents After Lumbar Fusion • Marquez-Lara et al
(Table 1 ). Deformity correction represented 12.6% oí patients with a CVA and only 6.5% in the unaffected patients. Similarly, 22.5% of the case in the patients with a CVA involved a 3-1--level fusion compared with 12.2% of the cases in the unaffected group. Revision cases approached statistical significance representing 4.1 % of the cases in the patients with a CVA versus 1.9% in unaffected patients (Table 1). Regardless of the surgical technique, patients who developed a postoperative CVA incurred a significantly greater LOS (8.9 vs. 3.8 d), total hospital costs ($41,454 vs. 25,885), and mortality (73.7 vs. 0.8 per 1000) than the unaffected patients (Table 1). Logistic regression identified factors associated with a postoperative cerebrovascular event with a 95% CI (Table 4). These risk factors included congestive heart failure
InliWteristics, Risk Factors, Outcomes jn 'Rat»ents^W¡^^^» •r ^ Lumbar ^ Fusion Su r g e r i ^ H ^ H «iiiaL;
Total (n = count)
CVA incidence (per 1000 cases)