Elsevier

World Neurosurgery

Volume 85, January 2016, Pages 114-124
World Neurosurgery

Original Article
Inpatient Outcomes and Postoperative Complications After Primary Versus Revision Lumbar Spinal Fusion Surgeries for Degenerative Lumbar Disc Disease: A National (Nationwide) Inpatient Sample Analysis, 2002–2011

https://doi.org/10.1016/j.wneu.2015.08.020Get rights and content

Introduction

The present study investigates outcomes in patients undergoing elective primary versus revision fusion surgery for lumbar degenerative pathologies with the use of a large population based database.

Methods

A total of 126,044 patients registered in the National Inpatient Sample (NIS) database were identified to have undergone elective fusion of the lumbar spine (primary fusion: 94%; redo fusion: 6%) for degenerative pathologies, between 2002 and 2011. A multivariable logistic regression model was built that adjusted for patient demographics and clinical and hospital characteristics to explore clinical outcomes and postoperative complications.

Results

The mean age of the cohort was 54.91 ± 13.98 years, and 58% were women. Multivariable regression analysis revealed patients undergoing redo lumbar fusion had a greater likelihood for an unfavorable discharge (odds ratio [OR] 1.17; 95% confidence interval [95% CI] 1.08–1.26; P < 0.0001), prolonged length of stay (OR: 1.80; 95% CI 1.68–1.92; P < 0.0001), greater hospital charges (OR 1.60; 95% CI 1.51–1.71; P < 0.0001), neurologic complications including dural tears and nerve root injuries (OR 2.06; 95% CI 1.80–2.37; P < 0.0001), deep venous thrombosis (OR 2.35; 95% CI 1.76–3.14; P < 0.0001), pulmonary embolism (OR 1.72; 95% CI 1.45–2.03; P < 0.0001), would infections (OR 2.40; 95% CI 1.79–3.22; P < 0.0001) and wound complications (OR 1.59; 95% CI 1.32–1.91; P < 0.0001), and gastrointestinal complications (OR 1.23; 95% CI 1.04–1.45; P = 0.016), compared with patients undergoing a primary lumbar fusion procedure.

Conclusions

The association of a likely postoperative complication in patients undergoing revision lumbar spine fusion compared with those undergoing primary fusion procedures at the same region of the spine is quantified. Our analysis provides baseline estimates that could aid in preoperative risk stratification and as an adjunct in patient education and counseling, and policy makers for higher reimbursements for these sicker patients.

Introduction

Lumbar degenerative disc disease (DDD), characterized by intervertebral lumbar disc narrowing, loss of disc signal intensity, and reduced disc height, is one of the most common conditions that is associated with and predisposes to chronic low back pain.1, 2 Considered as an inevitable, ubiquitous process occurring in most humans, it is estimated that approximately one-third of the asymptomatic, nonathletic population have at least one level of disc degeneration.3, 4 Although the exact etiology of disc degeneration remains largely unknown, an interplay of various risk factors are thought to be implicated in its pathogenesis. The nonmodifiable factors include advanced age, female sex and genetics, whereas modifiable factors include morbid obesity, cigarette smoking, occupational exposures (including activities involving lifting heavy physical loads,5, 6, 7, 8 back bending and twisting, vibrations from motor vehicle driving, trauma), and prolonged non-neutral and ergonomically inappropriate spine postures.9 Treatment options for symptomatic lumbar DDD and chronic low back pain span from conservative approaches to surgical interventions, aimed at stabilizing the spine.10 Treatments may include physical therapy, epidural injections, intradiscal electrothermal therapy, nucleoplasty, surgical decompression, and/or fusion and biologic therapies.

National statistics provided by the U.S. Department of Health & Human Services via the Health Care Utilization Project (HCUP)11 reveal an increased frequency of spinal fusion surgeries for all indications, irrespective of spinal level, during the past 20 years. Hospitalizations for spinal fusions increased from 61,000 in 1993 to 296,211 in 2002, and to more than 451,000 in 2012. This translates to an overall increase of more than 630% in the annual rate of spine fusions performed in the United States from 1993 to 2012.11 Between subset years 2002 and 2009, the annual rates of primary fusion surgery were greatest for the lumbar spine in comparison with the cervical and thoracic levels, soaring from 44.70 per 100,000 in 2002, to 71.74 per 100,000 in 2009, an increase of 60.5%.12 Alongside this increase in primary lumbar spine fusion surgeries in the United States between 2002 and 2009, Rajaee et al12 unsurprisingly noted a contemporary 52% increase in the annual number of revision fusion procedures for lumbar spine, albeit, at a lower rate than primary lumbar fusion procedures.

Recent technical and operative advances in spine surgeries, including improved instrumentation and greater-quality implants, minimally invasive techniques, neuro-monitoring and spinal neuronavigation, enhanced precision imaging modalities, and newer bone grafting options including introduction of biological fusion enhancement products, have been instrumental to the success of spinal fusion. Nevertheless, in contrast to other lumbar spinal surgeries, such as laminectomies or discectomies, fusion is associated with greater complication rates because of its greater complexity, more extensive dissection, prolonged operative periods,13 greater risk of intraoperative blood loss,14, 15 and implant/instrumentation failure, necessitating the need for a redo procedure in selected group of patients. As expected, revision fusion procedures often are associated with even greater perioperative complications, including delayed or poor wound healing and greater chances of a dural tear than primary procedures, thus predisposing patients to greater costs and resource use.

With a shift of focus towards outcomes-based research, it is critical to identify complication rates after surgical procedures, and several national analyses,16, 17, 18, 19, 20, 21 single institutional retrospective,15, 22, 23 and prospective studies24, 25, 26, 27 have identified associations of unfavorable outcomes after lumbar fusion and refusion surgeries.28 However, limited data are available in regard to an outcome-based comparison between primary lumbar fusions versus redo fusions with the use of a national database. To this effect, we used a large population-based prospective database, the National Inpatient Sample (NIS), to compare outcomes after primary and revision lumbar fusion surgeries for lumbar degenerative disease. Consisting of a random, stratified and validated sample, representing one-fifth of all admissions to nonfederal hospitals across the United States, the NIS incorporates data from diverse clinical practice settings and geographical locations and renders an appropriate statistical sampling power for analysis. By using the NIS, we investigated the association of unfavorable outcomes, including mortality, discharge disposition, length of stay, hospital charges, and postoperative complications after primary and revision lumbar fusion surgery for elective lumbar degenerative disease.

Section snippets

Data Source

The NIS database formulated by the Agency for Healthcare Research and Quality (Rockville, Maryland, USA) for the HCUP was the data source used for the present study.29 With discharge data collected prospectively over time, cumulatively from more 1000 nonfederal hospitals, the NIS is the largest publicly available inpatient database in the United States that includes an all-payer mix. The inpatient data sequenced in the NIS represent a 20% (one-fifth) random, stratified subsample of all

Cohort Definition and Selection Criteria

The NIS database was queried for the years 2002–2011 to identify adult patients (>18 years) registered in the database who underwent lumbar spine fusion surgery, either as primary (first) (ICD-9-CM codes 81.04–81.08) or a secondary (revision) procedure (ICD-9-CM codes 81.34–81.38). Because these procedural codes have overlap with thoracic and sacral levels, it was pertinent to screen patients undergoing a “definitive” fusion and refusion for degenerative pathologies at lumbar spinal levels

Patient Demographics and Clinical Characteristics

During the selected study period (2002–2011), 463,551 patients registered in the NIS underwent fusion surgery of the thoracolumbar and lumbosacral spine for various indications as depicted in Figure 1. On the basis of our selection criteria as described previously, 126,044 adult patients (>18 years old) were identified to have undergone “definitive” elective fusion surgery, either primary or revision procedure, for lumbar degenerative pathologies only, and thus constituted our study cohort for

Discussion

Since the earliest description of spinal fusions,38, 39 spinal arthrodesis has undergone dramatic improvement in operative techniques, instrumentation, and patient outcomes. Enhanced understanding of spinal biomechanics, continually evolving techniques, and innovations in instrumentation during the past 3 decades have contributed to a multifold increase in the number and indications for spinal fusion procedures. 12, 14, 40, 41, 42, 43, 44, 45, 46, 47 From initial use for stabilizing a

Conclusion

Using the NIS, we compared outcomes in adult patients undergoing primary versus revision lumbar spine fusion surgery for lumbar degenerative pathologies. The outcomes included inpatient mortality, unfavorable discharge, prolonged LOS, high-end hospital charges, neurologic complications, DVT, PE, wound infections and complications, gastro-intestinal, cardiac and respiratory complications and ARF. Greater rates of unfavorable outcomes and complications as seen in the revision cohort could serve

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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