Colonization of Bone Flaps by Cutibacterium acnes During Decompressive Craniectomies for Traumatic and Non-traumatic Indications: A Retrospective Observational Study.

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Background Cutibacterium acnes (C. acnes) is one of the most common bacteria in the human skin microbiota. Due to it generally requiring special culturing techniques, it was generally not routinely included in culture. However, recent laboratory automation advancements have allowed C. acnes to be a routinely tested pathogen. Though this could improve outcomes by detecting a virulent pathogen early, it has raised concerns about potential false positives leading to increased costs and medical risks. This study aims to analyze the C. acnes colonization rates in traumatic craniectomies and compare it to non-traumatic craniectomies, the former including risk factors due to penetrations and the latter being conceptually similar to a craniotomy with a lack thereof. This would help establish a baseline rate to understand the pathogen's implications better. Methodology We analyzed the electronic health records of 124 patients who underwent a craniectomy followed by a cranioplasty at Inova Health System from January 1, 2018, to January 1, 2023. The following categories of data were recorded for each patient: patient descriptors, comprehensive surgical timelines and outcomes, and bone flap viability and microbial colonization assessment. The chi-squared tests of independence and Wilcoxon signed-rank tests were used to assess statistical significance between groups in the indications underlying surgery (traumatic vs. non-traumatic) with C. acnes colonization, flap status (reimplanted vs. discarded), hospital length of stay (LOS), and unexpected 30-day readmission. Results Traumatic (67%) and non-traumatic (33%) craniectomies were compared. There was no significant association between the two craniectomy etiologies in terms of C. acnes colonization (40% vs. 26.5%, p=0.19), flap discardment (40% vs. 24%, p=0.12), or readmission rates (20% vs. 9.6%, p=0.18). However, a significant association was found between C. acnes colonization and LOS during the index craniectomy procedure (24.8 vs. 25.9 days, p=0.049), indicating that colonization may influence LOS. No significant association was found between the type of cranial surgery and LOS (p=0.83), suggesting other factors may play a more crucial role in determining LOS. The findings highlight the need to consider the impact of C. acnes colonization on surgical outcomes and hospital protocols. Conclusion Our findings illustrate that there is no significant difference between C. acnes colonization in traumatic and non-traumatic craniectomies; therefore, C. acnes can be expected to be cultured at a baseline level regardless of the etiology. Furthermore, there was no association with surgical indication and flap status, LOS, and readmission rates. However, a significant association was found between C. acnes status and LOS, indicating the increased complexity of care associated with the pathogen's detection. These findings support the protocol of deferring C. acnes culturing unless specific concerns are found.