Elsevier

The Spine Journal

Volume 13, Issue 10, October 2013, Pages 1171-1179
The Spine Journal

Clinical Study
Patient factors, comorbidities, and surgical characteristics that increase mortality and complication risk after spinal arthrodesis: a prognostic study based on 5,887 patients

https://doi.org/10.1016/j.spinee.2013.02.071Get rights and content

Abstract

Background context

The impact of patient factors and medical comorbidities on the risk of mortality and complications after spinal arthrodesis has not been well described. Prior works have been limited by small sample size, single center data, or the inability to be broadly generalized.

Purpose

To determine if there is an association between the patient demographic factors, comorbidities, nutritional status, and surgical characteristics and the occurrence of mortality and complications after spinal arthrodesis.

Study design

Retrospective review of prospectively collected data in the National Surgical Quality Improvement Program (NSQIP).

Patient sample

Patients who underwent spinal arthrodesis and had data registered with the NSQIP between 2005 and 2010.

Outcome measures

Primary outcomes were death or any complication after spinal arthrodesis. Secondary measures were the development of a specific complication, including wound infection, thromboembolic disease, or cardiac arrest/myocardial infarction.

Methods

The data set of the NSQIP from 2005 to 2010 was queried to identify all patients who underwent spinal arthrodesis. Demographic information, body mass index (BMI), medical comorbidities, arthrodesis procedure, operative time, American Society of Anesthesiologists (ASA) classification, and preoperative albumin were recorded for all patients identified. Mortality, the development of postoperative complications, and the presence of specific complications were also abstracted. Risk factors for mortality and complications were initially evaluated using chi-square and univariate logistic regression analyses. The risk factors that maintained p values less than .2 in univariate analysis were then combined in a multivariate fashion that identified significant, independent, predictors of mortality and complications while controlling for other factors present in the model. Sensitivity analysis was also performed, discriminating between the impact of risk factors on major and minor complications and the relative contribution to overall risk of morbidity. Multivariate analysis resulted in odds ratios (ORs) with 95% confidence intervals (CIs) for each risk factor. Only those predictors with ORs and 95% CI exclusive of 1.0 and p values less than .05 were considered statistically significant.

Results

In all, 5,887 patients who underwent spinal arthrodesis were identified. The average age of patients was 55.9 (±14.5) years. Twenty-five (0.42%) patients died after surgery, whereas 608 (10%) sustained a complication. Wound infection was the most common specific complication occurring in 2% of the cohort. Age (p=.03) and pulmonary conditions (p=.002) were found to have a significant association with the risk of mortality. Age exceeding 80 years was found to carry the highest risk of mortality. Age, pulmonary conditions, BMI, history of infection, ASA classification more than 2, neurologic conditions, resident (i.e., trainee) involvement, and procedural times exceeding 309 minutes increased the risk of complications. Body mass index, ASA classification more than 2, resident involvement, and procedural times exceeding 309 minutes were associated with the risk of infection. Although limited to univariate analysis, serum albumin 3.5 g/dL or less increased the risk of mortality, complications, wound infection, and thromboembolic disease. The OR for postoperative mortality among patients with albumin 3.5 g/dL or less was 13.8 (95% CI, 4.6–41.6; p<.001).

Conclusions

Several factors, including patients' age, BMI, ASA classification more than 2, pulmonary conditions, procedural times, and nutritional status likely influence the risk of postoperative morbidity to varying degrees. The risk factors identified here may be more generalizable to the American population as a whole because of the design and methodology of the NSQIP in comparison with previously published studies.

Introduction

Evidence & Methods

Delineating patients at risk for complications and mortality following treatment is important for decision making and truly informed consent.

In this assessment of data from NSQIP, the authors found that the elderly, those with low albumin (malnourished), and those with underlying pulmonary conditions were at increased risk of mortality following spinal fusion surgery. Similar underlying characteristics coupled with longer operative times (and resident involvement), increased BMI, and history of infection were important for complication development.

This is Level 4 data derived from an incomplete data set—many other individual factors (known and unknown) may have impacted morbidity and mortality that were not collected as part of NSQIP. This weakness is inherent in most administrative database analysis. As the registries improve (greater volume and detail of collected data) so will the reliability of the conclusions that follow. The findings here add support to much of what had been concluded from smaller studies. Randomized trials, high quality comparative cohort studies, and formal prospective case-control studies provide higher quality evidence.

—The Editors

As the number of spinal arthrodesis procedures has increased, so have concerns regarding elevated risks of mortality and postoperative complications, particularly compared with nonarthrodesis spinal procedures [1], [2], [3], [4]. This concern has been accentuated with the popularity of performance-based medicine within the medical community and among government and third-party payers [3]. In light of these trends, the importance of an in-depth understanding of patient-based characteristics, surgical factors, and medical conditions on perioperative morbidity and mortality after spinal arthrodesis is paramount.

Despite voluminous literature produced over the last 20 years, appreciation of the influence of specific risk factors on perioperative complications in the setting of spinal arthrodesis remains incomplete. Some previous works have focused only on a single complication (eg, wound infection) [5], [6], [7], [8], [9], [10] or relied on small samples [6], [11], [12], [13], [14]. Others have limited capacity for generalization. Even in prior studies that have used large data repositories or registries [5], [7], [9], [10], [15], [16], [17], [18], [19], there has been lack of sufficient specificity to facilitate an in-depth determination of the impact of various risks on outcome. As a result, the literature to date provides data that are either heavily informed by work performed at single centers among relatively small, and select, populations or yields recommendations derived from large data sets that enable only the most generic conclusions with limited relevance to individual patients or practitioners.

In light of the above findings, the present study was designed using patient-centered information obtained from the National Surgical Quality Improvement Program (NSQIP). With this data, the authors hoped to generate a more complete determination of the role that patient demographic factors, comorbidities, nutritional status, and surgical characteristics (eg, operative time, resident involvement, and procedure) may play in the occurrence of mortality or complications after spinal arthrodesis.

Section snippets

Materials and methods

This study received approval from our institution's investigational review board and the NSQIP of the American College of Surgeons. No funding was received in support of the preparation of this article, and the authors maintain no conflicts of interest to report.

Results

Between 2005 and 2010, 5,887 patients were identified as having undergone a spinal arthrodesis in the NSQIP database. The mean age of the cohort was 55.9 (±14.5) years, with a median age of 56 years and a range from 16 to 90 years. Most patients (58%) were age 59 years or younger and only 4% of patients were age 81 years and older. Fifty-three percent of patients were females (Table 1). The mean BMI approached obese (29.8±6.7), with only 23% of the cohort defined as underweight or normal.

Generalizable data

The population under study approached 6,000 patients who underwent surgery within a recent 5-year period. Moreover, the average age, body habitus, and demographic composition of the cohort approximated those of many other investigations in the spine surgical literature [4], [5], [6], [7], [11], [16], [23], [26], [27]. Additionally, the incidence of mortality [15], [16], [17], [18], [19], [23], [27] and the rates of overall morbidity [11], [23], [27] and specific complications, such as wound

Conclusions

Although recognizing its limitations, the present study suggests an elevated risk of mortality for older patients and those with a history of pulmonary conditions. The data found an increased risk of complications among older patients and those with ASA classification more than 2, pulmonary conditions, neurologic conditions, and a history of wound infection. Surgical characteristics, such as procedural length and resident involvement, were also influential. Our results are unique, in that serum

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    FDA device/drug status: Not applicable.

    Author disclosures: AJS: Nothing to disclose. PAC: Nothing to disclose. AWC: Nothing to disclose. JOB: Fees for participation in review activities such as date monitoring boards, statistical analysis, end point committees, and the like William Beaumont Army Medical Center (Contract with the University of Texas at El Paso for statistical support to cover part of my salary, Paid directly to institution/employer). CMB: Royalties: Wolterks Kluwer, Informa Healthcare (B); Other: Trial Design Team, Harvard Clinical Research Institute (B), Data Safety Monitoring Board, Intrinsic Therapeutics (B).

    The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.

    Disclaimers: Some authors are employees of the U.S. Federal Government and the United States Army. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of William Beaumont Army Medical Center, the Department of Defense, or United States government. The National Surgical Quality Improvement Program remains the full and exclusive property of the American College of Surgeons. The American College of Surgeons is not responsible for any claims arising from works based on the original data, text, tables, or figures.

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