Long-term clinical outcomes and complications after surgical treatment of degenerative spinal diseases: The Effect of BMI and Smoking

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Degeneration diseases of the spine cause symptoms such as pain and radiculopathy.  After exhausting non-surgical options, decompression and fusion is utilized to treat symptoms.  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 index (BMI), on the long-term clinical outcomes including complications after arthrodesis for spinal degenerative disease.

Prospectively gathered data were retrospectively reviewed from 228 patients, age 57.1 (21.2-86.3 years) who underwent open posterior spinal fusion with BMP for spinal degeneration from 2002-2011 at one spine center.  All patients had a minimum of 2 year clinical and radiographic follow-up. Fusions averaged 2.3 (range1-7) levels; 195 had TLIF, 22 had ALIF.  The BMI and smoking status of the patient were recorded. 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 5.8 years (24.1-125.6 months) complications included nonunion-9, infection-5, adjacent fractures-5 and long-term adjacent degeneration-97. Revision or extension of fusion was required in 43 (19%). The average BMI was 28.8 (16.2-43.6)) with 36 patients who were smokers.  The average preoperative VAS and ODI were 6.7 (0-10) and 52.8% (8-92%), respectively. At 2 years post-operative the average VAS and ODI were 4.1 (0-9) and 34.6 (0-78.0%), 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) and increasing age (p=0.033).  The overall complication rate was 14% in this study. Smoking and BMI had an Odds Ratio (OR) of 5.02 (95% CI 1.87-13.49) and 1.09 (95% CI 1.01-1.18) for rate of complications.  Age had an OR of 1.06 (95% CI 1.02-1.10)

At an average of 5 years of follow-up after PSF for spinal degeneration, one in five patients required revision or extension of their index procedure. Both smoking and BMI increased the odds of complications with smoking having a stronger predictive value.  Age was also weakly associated with increased complications.