Positive Cutibacterium acnes Intervertebral Discs Are Not Associated with Subsidence Following Anterior Cervical Discectomy and Fusion at 3 or 6 Months

<b>Background/Objectives:</b><i>Cutibacterium acnes</i> (<i>C. acnes</i>), formerly known as <i>Propionibacterium acnes</i> (<i>P. acnes</i>), is an anaerobic, low-virulent bacterium that has been associated with postoperative infections of the shoulder, knee, and cervical spine. Recent studies have highlighted an association between <i>C. acnes</i> and the development of degenerative disc disease (DDD). The aim of this study is to ascertain whether <i>C. acnes</i> increases the risk of subsidence following anterior cervical discectomy and fusion (ACDF). <b>Methods:</b> After IRB approval, consecutive patients undergoing elective ACDF for DDD from 2017 to 2018 were enrolled in this prospective cohort study. Intervertebral disc samples were taken at each affected level and cultured. A total of 66 patients with radiographic follow-ups were included in the final analysis. The extent of subsidence and cervical lordosis was determined immediately postoperatively and at the 3- and 6-month follow-ups. <b>Results:</b> No significant difference in subsidence was observed at 3 months (<i>p</i> = 0.07) or 6 months (<i>p</i> = 0.11) between culture-positive and -negative cohorts. Additionally, there was no significant difference detected in the change in cervical lordosis observed at 3 months (<i>p</i> = 0.16) or 6 months (<i>p</i> = 0.27) between culture-positive and -negative cohorts. For the most inferiorly fused segment, there was a significant difference in subsidence observed at 3 months (1.5 mm, 95% CI: 0.2-2.7 mm, <i>p</i> = 0.02) but not at 6 months (<i>p</i> = 0.17). <b>Conclusions:</b> Intervertebral discs with a positive <i>C. acnes</i> culture were not associated with greater levels of subsidence at 3 or 6 months following ACDF for DDD. Further research is necessary to endorse these results and to gauge the clinical significance of <i>C. acnes</i> infection.