The Effect of Cigarette Smoking and Vitamin D Status on Fusion Rates after Posterior Lumbar Interbody Fusion Surgery: Does Sound Radiological Fusion Correlates with Better Clinical Outcomes?

Abstract

Background Data: Lumbar interbody fusion surgeries are the gold standard surgical option in degenerative disc disorders and spondylolisthesis. Achieving solid arthrodesis at the operated segment remains the main goal of surgery. Yet, the correlation of sound radiological fusion with better clinical outcomes is not well established. In recent years, spinal surgeons had much greater awareness of the influence of vitamin D deficiency and cigarette smoking on spinal fusion. Purpose: To assess the influence of vitamin D deficiency and cigarette smoking on the rate of spinal arthrodesis after posterior lumbar interbody fusion (PLIF) in degenerative disc disorders and whether successful fusion correlates with clinical outcomes. Study Design: A prospective cohort study. Patients and Methods: The study was conducted on 67 patients (with a total of 92 levels) who underwent operation for PLIF with pedicle screw fixation. Twenty-six patients had degenerative spondylolisthesis, 20 had herniated discs, and 21 patients showed degenerative disc changes with segmental canal stenosis. In 29 patients, a local bone graft was used as soft PLIF. In the remaining 38 patients, a PEEK interbody cage was utilized. Patients were categorized according to both their serum vitamin D status (39 low; 28 normal) and cigarette smoking habits (18 smokers; 49 non-smokers). The final assessment was done 6 months postoperatively. Clinical outcomes were measured by the Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) for low back pain. Radiological fusion status was assessed on plain radiographs and graded according to Bridwell’s interbody fusion grading system. The relationship between vitamin D status and cigarette smoking and radiological outcomes was also evaluated. Results: Twenty-two males and 45 females were included in this study. The mean age was 55.8±±3.78 years. L4-L5 was the most commonly operated level, followed by L5-S1 and L3-4 (51.1%, 36.95%, and 11.95%, resp.). There were significant improvements in the mean ODI and VAS measures at final assessment regardless of the differences in vitamin D status or smoking habits. The fusion rate in the low vitamin D group was 79.5% versus 96.4% in the normal level group (P=0.045). 66.7% of those with poor radiological fusion were smokers versus 20.7% of those with sound fusion (P=0.004). There was no significant difference in fusion rates between the PEEK cage group and the bone graft group (P=0.128). There was no significant correlation between sound radiological fusion and better clinical outcomes (P=0.077 and P=0.157 for ODI and VAS, resp.). Conclusion: Smoking habits and low serum vitamin D seem to have a significant negative effect on the success of radiological spinal fusion. There was no significant relationship between radiological fusion and clinical outcomes. (2019ESJ190)

Keywords

• posterior lumbar interbody fusion
• degenerative disc disease
• vitamin d
• cigarette smoking
• radiological outcomes