Abstract
Study Design
Literature review.
Objective
The aim of this literature review was to detail the effects of smoking in spine surgery and examine whether perioperative smoking cessation could mitigate these risks.
Methods
A review of the relevant literature examining the effects of smoking and cessation on surgery was conducted using PubMed, Google Scholar, and Cochrane databases.
Results
Current smokers are significantly more likely to experience pseudarthrosis and postoperative infection and to report lower clinical outcomes after surgery in both the cervical and lumbar spines. Smoking cessation can reduce the risks of these complications depending on both the duration and timing of tobacco abstinence.
Conclusion
Smoking negatively affects both the objective and subjective outcomes of surgery in the lumbar and cervical spine. Current literature supports smoking cessation as an effective tool in potentially mitigating these unwanted outcomes. Future investigations in this field should be directed toward developing a better understanding of the complex relationship between smoking and poorer outcomes in spine surgery as well as developing more efficacious cessation strategies.
Introduction
With an estimated 42.1 million cigarette smokers in the United States, leading to 480,000 deaths annually, smoking is a major public health concern. 1 Although the cardiovascular and respiratory complications are well documented, an emerging body of literature suggests that tobacco addiction predisposes users to an increased incidence of postoperative complications in most surgical disciplines. Of particular interest to the practicing spine surgeon are the increased risks of nonunion, postoperative wound complications, and diminishment of both objective and subjective postoperative outcomes. The purpose of this article is to detail the effects of tobacco use and cessation on spine surgery within the current medical literature.
Arthrodesis
Smoking increases the risk of nonunion in both lumbar and cervical spine procedures. 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 Though the mechanism of tobacco-related inhibition on bony fusion is not completely understood, the three most commonly accepted theories for the phenomena include a decrease in systemic bone mineral density, osteoblastic cellular metabolism, and local blood flow and angiogenesis. 10 In combination, these negative effects create a challenging fusion environment that has been documented by numerous investigators in both human and animal studies.
Multiple animal models have demonstrated a correlation between nicotine exposure and diminished bone healing.
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In a study examining single-level posterior lateral lumbar fusion in New Zealand white rabbits, Silcox et al reported significantly higher rates of fusion in control specimens than those exposed to systemic nicotine (56 versus 0%,
Lumbar Spine
Multiple investigators have reported cigarette use as a major independent risk factor for the development of a lumbar pseudarthrosis (Table 1).
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In a review of 357 patients undergoing one- or two-level lumbar fusion, Glassman et al reported a statistically significant increased risk of nonunion in smokers (26.5 versus 14.2%,
Arthrodesis rates in lumbar fusion procedures
Cervical Spine
Although the effects of cigarette use may be less detrimental in cervical fusion than lumbar procedures,
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multiple investigators have demonstrated a link between smoking and cervical nonunion (Table 2).
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In a retrospective review of 132 patients who underwent anterior cervical diskectomy and fusion, Bishop et al reported a nonunion rate of 14% in smokers compared with 0% in smokers.
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Additionally, the investigators noted significantly higher rates of delayed union, greater disk space collapse, and diminishment of the disk angle in the smoking population.
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Although two large retrospective reviews by An et al and Bohlman et al both demonstrated trends toward higher rates of pseudarthrosis in smokers undergoing anterior cervical interbody fusion, neither reached statistical significance.
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However, it should be noted that in each of these studies ∼50% of patients had a single-level fusion. Similarly, in a population of 573 patients undergoing single-level anterior cervical diskectomy and fusion with allograft bone and rigid fixation, Luszczyk et al reported no significant difference in the fusion rates among smokers and nonsmokers.
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In an attempt to determine the effects of smoking on 131 multilevel anterior cervical interbody fusions, Hilibrand et al reported a significantly higher fusion rate in nonsmokers (76 versus 50%,
Arthrodesis rates in cervical fusion procedures
Abbreviation: ACDF, anterior cervical diskectomy and fusion.
Smoking's effect on fusion rates in individuals undergoing multilevel fusion through an anterior cervical corpectomy or a posterior cervical fusion may not be as profound. In a review of 59 patients undergoing corpectomy and strut grafting, Hilibrand and colleagues reported identical rates of fusion between smokers and nonsmokers (93%). 21 However, in a study of 132 patients undergoing cervical corpectomy, Lau et al reported pseudarthrosis rates of 16% in smokers versus 4.3% in nonsmokers at 1 year. 22 Although this difference failed to reach statistical significance, a possible explanation for the trends toward higher rates of pseudarthrosis may be that the average follow-up for this investigation was only 1 year after surgery as opposed to the 2-year period used in the Hilibrand review. This shorter follow-up may be significant; at least two investigators have reported that smoking decreases the rate of fusion even in individuals who ultimately develop a stable union. 7 , 17 In a retrospective case series of 158 patients undergoing posterior cervical fusion with lateral mass screw fixation, Eubanks et al noted identical fusion rates among smokers and nonsmokers (100%). 23 The results of these investigations seem to suggest that in patients who smoke with multiple-level pathology, considering corpectomy or posterior-based procedures when appropriate may provide higher fusion rates than performing multiple-level anterior interbody fusions.
Clinical Outcome Measures
Multiple investigators have reported a correlation between smoking and diminished clinical outcomes with both operative and nonoperative treatment for spinal conditions. 6 , 21 , 23 , 24 , 25 , 26 Although increases in surgical complications such as pseudarthrosis and infection undoubtedly contribute to the diminished postoperative results seen in the smoking population, the systemic effects of nicotine are likely also significant. 6 , 23 , 27 One of the documented effects of smoking is increased rates of disk degeneration in both the cervical and lumbar spine. 27 , 28 , 29 The most commonly proposed mechanism for this phenomenon is that smoking decreases the blood flow to the disk tissue, which leads to decreased cellular metabolism within the intervertebral disk tissue and earlier disk degeneration. 29 , 30 This process likely continues into the postoperative period, potentially predisposing cigarette users to increased rates of recurrent pathologic changes at the operated levels and adjacent-level disease. This smoking-related disk degeneration provides a likely explanation for the higher rates of recurrent or adjacent-level disease requiring reoperation observed in numerous studies. 31 , 32 , 33 , 34 , 35 Nicotine is also a central pain-modulating agent and individuals with higher rates and intensity of spine-related pain may be predisposed to addiction to help mitigate their symptoms. 6 , 36 , 37 , 38 Finally, the higher incidence of depression among smokers predisposes this population to increased back-related disability, which could negatively affect postoperative outcome measures. 6 , 39 , 40 The combination of these factors likely contributes to the differences between smokers and nonsmokers in clinical outcomes with both operative and nonoperative treatment of spinal pathology.
Lumbar Spine
Multiple investigators have demonstrated an association between smoking and worse clinical outcome measures and return to work rates in individuals undergoing lumbar spine procedures.
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In a review of 825 patients undergoing microdecompression for degenerative lumbar stenosis, Gulati et al noted a significant difference in Oswestry Disability Index (ODI) score change from the preoperative baseline levels in smokers versus nonsmokers (4.2 points, 95% confidence interval [CI] 0.98 to 7.34,
Smoking has also been correlated to worse surgical outcomes and lower return to work rates in procedures involving lumbar fusion. Glassman et al reported significantly higher return to work rates (71 versus 53%,
Cervical Spine
In cervical spine procedures, smokers appear more likely to experience a suboptimal clinical outcome than nonsmokers irrespective of the approach employed. Hilibrand et al noted significantly higher rates of excellent or good functional outcomes in nonsmokers undergoing multilevel anterior cervical diskectomy and fusion compared with nonsmokers (89 versus 72.5%,
Postoperative Infection
Postoperative infection represents one of the greatest fears for the practicing spine surgeon due to its association with increased costs, longer hospitalization times, and higher rates of secondary surgeries and nonunion.
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Tobacco use increases the risk of wound complications and infection by creating a temporary reduction in tissue oxygenation and blood flow and decreasing the effectiveness of inflammatory cell function and oxidative bactericidal mechanisms; in addition, reparative cell function is inhibited.
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Researchers from multiple surgical disciplines have correlated smoking with higher rates of wound complications and infections.
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More specifically, these effects have been illustrated in spine surgery by multiple investigators (Table 3).
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In a review of the Department of Veterans’ Affairs National Surgical Quality Improvement Program database, Veeravagu et al reported that smokers had a statistically significant higher rate of infection than nonsmokers (OR 1.19, 95% CI 1.02 to 1.37).
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In a retrospective review of 1,629 procedures, Fang et al reported a postoperative infection rate of 4.4%.
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In this study, smokers represented 33% of the population who developed infections compared with only 16.8% of those who healed uneventfully (
Risk of infection with smoking in spine surgery
Abbreviation: CI, confidence interval.
Smoking Cessation
The overall health benefits related to smoking cessation are well documented and include decreased risks of multiple types of primary malignancies, coronary and peripheral arterial disease, respiratory infection, cerebral vascular accident, and chronic pulmonary disease.
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Similarly, multiple investigators have reported significant benefits associated with tobacco cessation in patients undergoing spine surgery. In a retrospective analysis of 86 patients with documented nonunion at 88 levels, Carpenter et al noted that smoking cessation significantly affected patient outcome scores on a questionnaire that addressed pain, functional status, progress after the surgery, and postoperative satisfaction.
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In this study, individuals who successfully stopped smoking scored 65/100 and patients who continued smoking scored 45/100 (
When to quit and how long to refrain from smoking are important questions for the practicing clinician to answer when advising patients considering elective spine surgery. Although there is no definitive data, several investigators have provided meaningful information on which to base recommendations. Glassman et al noted significant improvements in fusion rates, satisfaction scores, and return to work rates in patients who refrained from smoking postoperatively, 6 with results tending to be better in individuals who quit for more than 6 months after surgery. 6 Interestingly, preoperative smoking cessation did not significantly alter the postoperative outcomes. 6 Notably, the investigators found no association between preoperative smoking cessation and fusion rates, satisfaction scores, or return to work rates. 6 Despite these findings, preoperative smoking cessation for 4 weeks is associated with a decreased risk of infection, perioperative respiratory, and wound complications. 49 , 61 , 62 In a meta-analysis of studies from a range of surgical specialties, Mills et al reported a 41% risk reduction of postoperative complications for patients who quit smoking before surgery. 63 Within the studies analyzed, trials that consisted of smoking cessation for 4 weeks or greater had a significantly larger treatment effect than those investigating shorter periods of abstinence from tobacco. 63 A patient's ability to stop smoking preoperatively may also be an important predictor of their ability to refrain from smoking after surgery. 6 To this end, Glassman et al noted that less than 10% of patients who smoked up until the day of surgery were able to stop postoperatively. 6 As a result of these findings in our own practice, we request patients be free of tobacco 4 weeks before undergoing elective spine surgery and continue to refrain from smoking for 6 months after surgery.
With reported success rates as low as 8 to 27.5% in the general population, 64 , 65 , 66 many spine surgeons are skeptical of a patient's ability to reliably quit smoking around the time of surgery. 67 In a retrospective review of 426 patients who underwent lumbar fusion, Andersen et al noted that only 13% of patients were able to stop smoking after surgery with counseling alone. 4 Of the individuals who did quit, 50% experienced a relapse at some point during their postoperative course. 4 Although these abysmal rates of success lead some to question the value of time invested in tobacco cessation attempts, conflicting evidence suggests that patients preparing for elective spine procedures may quit at higher rates than the general smoking population. To this end, Glassman et al reported that 63.8% of smokers quit for at least 1 to 6 months and 40.4% quit for at least 6 months after surgery. 6 Impressively, 90% of this population did not need the aid of nicotine-containing gums or patches or other medications. 6 These findings may indicate that individuals considering spine surgery represent a portion of the population more likely to quit if counseled appropriately on the risk of continuing to smoke in the postoperative period. However, given the conflicting data of the efficacy of counseling alone, physicians should consider offering any of the host of validated cessation aids in conjunction with preoperative patient education to maximize the success rate.
Conclusion
Due to its association with higher rates of postoperative infection and pseudarthrosis and lower clinical outcome measures, smoking presents a major challenge to the practicing spine surgeon. Fortunately, these risks appear to be mitigated to some extent with tobacco cessation in the perioperative period. As a result, surgeons should counsel smokers on their elevated risk prior to surgery and assist in the development of a comprehensive cessation program that ideally would start at least 4 weeks prior to surgery and continue 6 months postoperatively. Future investigations in this field should be directed toward developing a better understanding of the complex relationship between smoking and its effect on individuals undergoing spine surgery as well as the development of more efficacious cessation strategies.
Disclosures
Keith L. Jackson II: none
John G. Devine: none
Footnotes
Disclaimer
The views expressed herein are those of the author(s) and do not reflect the official policy of the Department of the Army, Department of Defense, or the U.S. Government.
