What are the effects of smoking on spinal fusion outcomes in a 32-year-old male patient with ankylosing spondylitis?

Effects of Smoking on Spinal Fusion Outcomes

Smoking significantly increases the risk of reoperation for pseudarthrosis after spinal fusion surgery, with tobacco users facing a 32% risk of reoperation compared to nonsmokers, and active smokers should be strongly counseled to abstain from smoking both before and after surgery. 1

Primary Impact: Increased Reoperation Risk

The Congress of Neurological Surgeons provides Grade B evidence that smoking is independently associated with increased reoperation rates after spinal fusion. 1 This recommendation is based on 8 studies, with 6 demonstrating positive correlation between smoking and reoperation (all Class II evidence). 1

Key findings include:

• Tobacco users have a 32% risk of reoperation for pseudarthrosis versus significantly lower rates in nonsmokers (P = 0.027). 1
• In a large database review of 107,420 cervical fusion patients, smoking was identified as an independent risk factor for reoperation. 1
• The association between smoking and reoperation is consistent across both cervical (4 Class II studies) and lumbar fusion procedures. 1

Mechanisms of Impaired Fusion

Smoking compromises spinal fusion through multiple pathways that directly impair bone healing. 2, 3

Biochemical effects include:

• Impaired vascular supply to spinal tissues through atherosclerosis and thrombosis. 3
• Local tissue hypoxia, inflammation, and proteolysis that compromise disc, cartilage, bone, and blood vessels. 3
• Accelerated spondylosis and compromised cellular healing mechanisms. 3

Clinical Outcomes Beyond Fusion Rates

While fusion rates are the primary concern, smoking affects multiple perioperative outcomes. 2, 4

Additional complications include:

• Increased surgical site infection rates. 2
• Higher rates of adjacent-segment pathology. 2
• Increased risk of dysphagia in cervical procedures. 2
• Significantly better radiographic fusion success in non-smokers (P = 0.01). 4

Special Consideration for Ankylosing Spondylitis

For your 32-year-old male patient with ankylosing spondylitis, the smoking effects are particularly concerning because:

• The underlying inflammatory condition already compromises bone quality and healing. 3
• Younger patients may underestimate long-term risks, yet face decades of potential complications. 5
• The combination of inflammatory arthropathy and smoking creates compounded risk for pseudarthrosis. 2, 3

Smoking Cessation Recommendations

The evidence on preoperative cessation is nuanced but clinically important:

• There is insufficient evidence (Grade Insufficient) that preoperative cessation decreases reoperation risk, but patients should still be counseled to abstain before and after surgery. 1
• The most important recommendation is smoking cessation for at least 4 weeks after surgery. 2
• Recidivism rates are extremely high: 60% at 3 months, 61% at 6 months, and 68% at 1 year postoperatively. 5
• Older patients (mean age 55.2 years) are more likely to relapse compared to younger patients (mean age 44.2 years, P = 0.03). 5

Important Caveats

Single-level cervical fusion with rigid fixation may be an exception:

• One large study (573 patients) found no significant difference in fusion rates between smokers (91.0%) and nonsmokers (91.6%, P = 0.867) for single-level ACDF with allograft and locked plate. 6
• However, this finding applies specifically to single-level cervical procedures with rigid fixation and should not be extrapolated to multilevel fusions or lumbar procedures. 6

Risk Mitigation Strategies

When surgery cannot be delayed for smoking cessation:

• Consider bone morphogenetic proteins (BMPs) to reduce pseudarthrosis risk in smokers. 2
• Use rigid fixation techniques when appropriate (particularly for single-level cervical procedures). 6
• Nicotine replacement therapy remains an area of investigation, but definitive evidence for its efficacy in improving fusion outcomes is lacking. 2
• Counsel patients extensively about the 32% reoperation risk and emphasize the critical importance of postoperative abstinence. 1

Practical Clinical Approach

For your patient, the following algorithm applies:

1. Mandatory counseling: Document discussion of 32% reoperation risk with continued smoking. 1
2. Attempt cessation: Encourage immediate smoking cessation, though acknowledge insufficient evidence it will reduce reoperation risk if surgery proceeds soon. 1
3. Surgical planning: Consider BMP augmentation given smoking status and underlying inflammatory condition. 2
4. Postoperative management: Emphasize critical 4-week minimum abstinence period and arrange smoking cessation support given 60% recidivism rate. 2, 5
5. Long-term monitoring: Increased surveillance for pseudarthrosis with earlier imaging if symptoms suggest nonunion. 4