Microbiome impacts surgical outcomes– comparison of gut microbiome dysbiosis in patients undergoing lumbar microdiscectomy: results from the MISO pilot study

Background: More than 10% of patients undergoing lumbar microdiscectomy for symptomatic lumbar disc herniation (LDH) develop failed back surgery syndrome (FBSS) often without clear cause. Recent findings of pathobiont gut bacteria in degenerative intervertebral discs (IVDs) suggest a potential “gut-disc axis,” where microbiome-mediated inflammation and disc colonization might undermine surgical outcomes. This novel pilot study aims to determine whether changes in gut microbial composition (dysbiosis) can predict FBSS after one level lumbar microdiscectomy for symptomatic LDH. Methods: 20 adult patients undergoing one-level lumbar microdiscectomy for symptomatic LDH were prospectively studied. Numerical rating scale (NRS) and Oswestry Disability Index (ODI) scores were collected preoperatively and at 3 months and 6 months postoperatively. Achievement of minimum clinically important difference (MCID) was defined as a > 30% improvement in NRS and ODI score. Preoperative Stool samples were analyzed using 16 S rRNA sequencing. Alpha diversity and beta diversity were assessed to determine microbial diversity differences. Taxonomic composition was compared at the phylum and genus levels. Results: Of the 20 patients, 16 achieved MCID, while 4 developed FBSS at 3 and 6 months. There were no significant differences in age, sex, BMI, race, level of surgery, and pre-operative NRS and ODI between groups. Alpha diversity was similar (p = 0.437), but beta diversity showed significant differences in microbial community structure (p < 0.05). Differential abundance analysis identified patients who experienced FBSS had higher levels of pro-inflammatory Prevotella (U = 2, p = 0.002) and lower levels of commensal Bacteroides (U = 61, p = 0.003)) and Faecalibacterium (U = 53, p = 0.047). Conclusion: This study is the first to identify a Prevotella-dominant enterotype, along with a reduction in the anti-inflammatory genera Bacteroides and Faecalibacterium, as potential contributors to an increased risk of FBSS. Studies of higher power are required to estimate the effect sizes of these associations, investigate causation, and consider the viability of synbiotic therapy to improve spine surgery outcomes.