Long-term clinical outcomes after fusion for spondylolisthesis: the effect of BMI and smoking

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Multilevel arthrodesis can be employed to manage spondylolisthesis and reduce the risk of traumatic dislocation. The pre-operative risk factors for complications and inferior outcomes in these patients are not clearly understood. We studied the impact of 2 specific risk factors, smoking and body mass, on the long-term clinical and occupational outcomes after arthrodesis for spondylolisthesis. 

Prospectively collected data were retrospectively reviewed from  228 patients, age 62.7 (19.1-85.8 years) who had undergone open posterior instrumented fusion with BMP for symptomatic spondylolisthesis at one spine center from 2002-2011. Patients included required a minimum 2 year clinical and radiographic follow-up.  Fusions average 2 levels (range 1-7); 213 had TLIF’s and 8 had ALIF’s. BMI and smoking status were recorded on each patient.  Clinical outcomes included perioperative and long-term complications, preoperative and 2 year Visual Analog Pain Scale (VAS) and Oswestry Disability Index (ODI). Using logistic regression, the association of BMI and smoking status on outcome measures was analyzed.

At an average follow-up of 5 years (24-120 months). Complications included nonunion-3, infection-3, adjacent fractures-6, long-term adjacent degeneration-101. Revision or extension of fusion was required in 9 (3.9%).  The average BMI was 29.3 (17.8-47.2) with 29 patients who were smokers. At 2 years post-operative the average VAS and ODI were 3.3 (0-9) and 27.3 (0-78%), respectively. Logistic regression found that neither BMI nor smoking were significant predictors of post-operative VAS and ODI scores.  The only significant predictors of post-operative VAS and ODI scores were preoperative VAS and ODI scores (p<0.001).  The overall complication rate was 10% in this study. Smoking and BMI had an Odds Ratio (OR) of 7.87 (95% CI 2.28-27.13) and 1.07 (1.00-1.15) for rate of complications. Gender and age had an OR of 4.26 (95% CI 1.19-15.17) and 1.05 (1.00-1.11) with complications more common in the female and older patients. None of the lumped complications were especially common.

While both smoking and obesity were associated with an increased risk of complications, smoking had a much larger odds ratio for complication than increasing BMI. While this study is not powered to detect increased risk for individual complications, it suggests that additional discussion may be warranted when counseling patients of who smoke regularly as to their risk of surgical complication.