Bone flap management strategies for postcraniotomy surgical site infection

Diagnostic, clinical management, and outcome of bone flap-related osteomyelitis after cranioplasty

OBJECTIVES

We aimed to describe diagnostic, management, and outcome of bone flap-related osteomyelitis after cranioplasty.

METHODS

Patients followed up in our tertiary care hospital for bone flap-related osteomyelitis after cranioplasty were included in a retrospective cohort (2008-2021). Determinants of treatment failure were assessed using logistic regression and Kaplan-Meier curves analysis.

RESULTS

The 144 included patients (81 [56.3%] males; median age 53.4 [interquartile range [IQR], 42.6-62.5] years) mostly presented wound abnormalities (n = 115, 79.9%). All infections were documented, the main pathogens being Staphylococcus aureus (n = 64, 44.4%), Cutibacterium acnes (n = 57, 39.6%), gram-negative bacilli (n = 40, 27.8%) and/or non-aureus staphylococci (n = 34, 23.6%). Surgery was performed in 140 (97.2%) cases, for bone flap removal (n = 102, 72.9%) or debridement with flap retention (n = 31, 22.1%), along with 12.7 (IQR, 8.0-14.0) weeks of antimicrobial therapy. After a follow-up of 117.1 (IQR, 62.5-235.5) weeks, 37 (26.1%) failures were observed: 16 (43.2%) infection persistence, three (8.1%) relapses, 22 (59.5%) superinfections and/or two (1.7%) infection-related deaths. Excluding superinfections, determinants of the 19 (13.4%) specific failures were an index craniectomy for brain tumor (odds ratio = 4.038, P = 0.033) and curettage of bone edges (odds ratio = 0.342, P = 0.048).

CONCLUSION

Post-craniectomy bone flap osteomyelitis are difficult-to-treat infection, necessitating prolonged antimicrobial therapy with appropriate surgical debridement, and advocating for multidisciplinary management in dedicated reference centers.

Epigenetic Regulation of Leukocyte Inflammatory Mediator Production Dictates Staphylococcus aureus Craniotomy Infection Outcome

Staphylococcus aureus is a common cause of surgical-site infections, including those arising after craniotomy, which is performed to access the brain for the treatment of tumors, epilepsy, or hemorrhage. Craniotomy infection is characterized by complex spatial and temporal dynamics of leukocyte recruitment and microglial activation. We recently identified unique transcriptional profiles of these immune populations during S. aureus craniotomy infection. Epigenetic processes allow rapid and reversible control over gene transcription; however, little is known about how epigenetic pathways influence immunity to live S. aureus. An epigenetic compound library screen identified bromodomain and extraterminal domain-containing (BET) proteins and histone deacetylases (HDACs) as critical for regulating TNF, IL-6, IL-10, and CCL2 production by primary mouse microglia, macrophages, neutrophils, and granulocytic myeloid-derived suppressor cells in response to live S. aureus. Class I HDACs (c1HDACs) were increased in these cell types in vitro and in vivo during acute disease in a mouse model of S. aureus craniotomy infection. However, substantial reductions in c1HDACs were observed during chronic infection, highlighting temporal regulation and the importance of the tissue microenvironment for dictating c1HDAC expression. Microparticle delivery of HDAC and BET inhibitors in vivo caused widespread decreases in inflammatory mediator production, which significantly increased bacterial burden in the brain, galea, and bone flap. These findings identify histone acetylation as an important mechanism for regulating cytokine and chemokine production across diverse immune cell lineages that is critical for bacterial containment. Accordingly, aberrant epigenetic regulation may be important for promoting S. aureus persistence during craniotomy infection.

Surgical Site Infections in Glioblastoma Patients-A Retrospective Analysis

Surgical site infections (SSIs) after craniotomy lead to additional morbidity and mortality for patients, which are related to higher costs for the healthcare system. Furthermore, SSIs are associated with a longer hospital stay for the patient, which is particularly detrimental in glioblastoma patients due to their limited life expectancy. Risk factors for SSIs have already been described for craniotomies in general. However, there is limited data available for glioblastoma patients. As postoperative radiation influences wound healing, very early radiation is suspected to be a risk factor for SSI. Nevertheless, there are no data on the optimal timing of radiotherapy. To define risk factors for these patients, we analyzed our collective. We performed a retrospective analysis of all operations with histological evidence of a glioblastoma between 2012 and 2021. Open biopsy and tumor removal (gross total resection, subtotal resection) were included. Stereotactic biopsies were excluded. Demographic data such as age and gender, as well as duration of surgery, diameter of the trepanation, postoperative radiation with interval, postoperative chemotherapy, highest blood glucose level, previous surgery, ASA score, foreign material introduced, subgaleal suction drainage, ventricle opening and length of hospital stay, were recorded. The need for surgical revision due to infection was registered as an SSI. A total of 177 patients were included, of which 14 patients (7.9%) suffered an SSI. These occurred after a median of 45 days. The group with SSIs tended to include more men (57.1%, p = 0.163) and more pre-operated patients (50%, p = 0.125). In addition, foreign material and subgaleal suction drains had been implanted more frequently and the ventricles had been opened more frequently, without reaching statistical significance. Surprisingly, significantly more patients without SSIs had been irradiated (80.3%, p = 0.03). The results enable a better risk assessment of SSIs in glioblastoma patients. Patients with previous surgery, introduced foreign material, subgaleal suction drain and opening of the ventricle may have a slightly higher for SSIs. However, because none of these factors were significant, we should not call them risk factors. A less radical approach to surgery potentially involving these factors is not justified. The postulated negative role of irradiation was not confirmed, hence a rapid chemoradiation should be induced to achieve the best possible oncologic outcome.

IL-10 production by granulocytes promotes Staphylococcus aureus craniotomy infection

BACKGROUND

Treatment of brain tumors, epilepsy, or hemodynamic abnormalities requires a craniotomy to access the brain. Nearly 1 million craniotomies are performed in the US annually, which increase to ~ 14 million worldwide and despite prophylaxis, infectious complications after craniotomy range from 1 to 3%. Approximately half are caused by Staphylococcus aureus (S. aureus), which forms a biofilm on the bone flap that is recalcitrant to antibiotics and immune-mediated clearance. However, the mechanisms responsible for the persistence of craniotomy infection remain largely unknown. The current study examined the role of IL-10 in promoting bacterial survival.

METHODS

A mouse model of S. aureus craniotomy infection was used with wild type (WT), IL-10 knockout (KO), and IL-10 conditional KO mice where IL-10 was absent in microglia and monocytes/macrophages (CX3CR1CreIL-10 fl/fl) or neutrophils and granulocytic myeloid-derived suppressor cells (G-MDSCs; Mrp8CreIL-10 fl/fl), the major immune cell populations in the infected brain vs. subcutaneous galea, respectively. Mice were examined at various intervals post-infection to quantify bacterial burden, leukocyte recruitment, and inflammatory mediator production in the brain and galea to assess the role of IL-10 in craniotomy persistence. In addition, the role of G-MDSC-derived IL-10 on neutrophil activity was examined.

RESULTS

Granulocytes (neutrophils and G-MDSCs) were the major producers of IL-10 during craniotomy infection. Bacterial burden was significantly reduced in IL-10 KO mice in the brain and galea at day 14 post-infection compared to WT animals, concomitant with increased CD4+ and γδ T cell recruitment and cytokine/chemokine production, indicative of a heightened proinflammatory response. S. aureus burden was reduced in Mrp8CreIL-10 fl/fl but not CX3CR1CreIL-10 fl/fl mice that was reversed following treatment with exogenous IL-10, suggesting that granulocyte-derived IL-10 was important for promoting S. aureus craniotomy infection. This was likely due, in part, to IL-10 production by G-MDSCs that inhibited neutrophil bactericidal activity and TNF production.

CONCLUSION

Collectively, these findings reveal a novel role for granulocyte-derived IL-10 in suppressing S. aureus clearance during craniotomy infection, which is one mechanism to account for biofilm persistence.

Immediate Titanium Mesh Cranioplasty After Debridement and Craniectomy for Postcraniotomy Surgical Site Infections and Risk Factors for Reoperation

BACKGROUND

We previously published a novel strategy for management of postcraniotomy bone flap infection consisting of single stage debridement, bone flap removal, and immediate titanium mesh cranioplasty.

METHODS

Postcraniotomy patients with surgical site infections treated with surgical debridement, bone flap removal, and immediate titanium mesh cranioplasty were retrospectively reviewed. The primary outcome measure was reoperation due to persistent infection or wound healing complications from the titanium mesh.

RESULTS

We included 48 patients, of which 15 (31.3%) were female. The most common primary diagnoses were glioblastoma (31.3%), meningioma (18.8%), and vascular/trauma (16.7%). Most patients had a history of same-site craniotomy prior to the surgery complicated by surgical site infection and 47.9% had prior cranial radiation. Thirty-six (75.0%) patients achieved resolution of their infection and did not require a second operation. Twelve (25.0%) patients required reoperation: 6 (12.5%) patients were found to have frank intraoperative purulence on reoperation, whereas 6 (12.5%) had reoperation for poor wound healing without any evidence of persistent infection. Cochran Armitage trend test revealed that patients with increasing number of wound healing risk factors had significantly higher risk of reoperation (P = 0.001). Prior intensity modulated radiotherapy alone was a significant risk factor for reoperation (6.5 [1.40-30.31], P = 0.002). Median follow-up time was 20.5 weeks.

CONCLUSIONS

Immediate titanium mesh cranioplasty at the time of debridement and bone flap removal is an acceptable option in the management of post-craniotomy bone flap infection. Patients with multiple wound healing risk factors are at higher risk for reoperation.

Comparison of Infection Rates Following Immediate and Delayed Cranioplasty for Postcraniotomy Surgical Site Infections: Results of a Meta-Analysis

Postoperative surgical site infections (SSIs) in neurosurgery are rare. However, they pose a formidable challenge to the treating neurosurgeon and substantially worsen patient outcomes. These infections require prompt intervention in the form of débridement, including removal of craniotomy bone. Reconstruction of the craniotomy defect can be performed along with the débridement or can be performed at a later time. Although there have been concerns about performing cranioplasty at the same time as débridement, recent studies have advocated performance of cranioplasty at the same time as the débridement, as it avoids the morbidity associated with having a craniectomy defect and avoids the need for another surgical procedure. We conducted a literature review and meta-analysis to examine the data on immediate cranioplasties and delayed cranioplasties performed for postcraniotomy SSIs. We analyzed 15 articles with a total of 353 patients. Our analysis revealed that the pooled proportion of treatment failure was 10.4% (95% confidence interval [CI] 5.9%-17.8%) when an immediate cranioplasty was done and 16.1% (95% CI 7.2%-32.1%) when delayed cranioplasty was done. The pooled proportion of treatment failure was 12% (95% CI 5.9%-22.9%) when the same bone was used for cranioplasty and was 8% (95% CI 3%-20%) when prosthetic material such as titanium was used for cranial vault reconstruction. Thus, the rate of treatment failure was less when an immediate single-stage cranioplasty was done compared with a delayed cranioplasty following SSIs.

Transcriptional Profiling of Phagocytic Leukocytes and Microglia Reveals a Critical Role for Reactive Oxygen Species in Biofilm Containment during Staphylococcus aureus Craniotomy Infection

Craniotomies are performed to treat a variety of intracranial pathology. Surgical site infection remains a complication of craniotomy despite the use of prophylactic antibiotics and universal sterile precautions. Infections occur in 1-3% of procedures, with approximately half caused by Staphylococcus aureus that forms a biofilm on the bone flap and is recalcitrant to systemic antibiotic therapy. We used an S. aureus-dsRed construct to compare the phagocytic capacity of leukocytes and microglia in vitro and in vivo using a mouse model of craniotomy infection. In addition, single-cell RNA sequencing (scRNA-seq) was applied to determine whether a transcriptional signature could be identified for phagocytic versus nonphagocytic cells in vivo. S. aureus was phagocytosed to equivalent extents in microglia, macrophages, neutrophils, and granulocytic myeloid-derived suppressor cells in vitro; however, microglial uptake of S. aureus was limited in vivo, whereas the other leukocyte populations exhibited phagocytic activity. scRNA-seq comparing the transcriptional signatures of phagocytic (S. aureus-dsRed+) versus nonphagocytic (S. aureus-dsRed-) leukocytes identified classical pathways enriched in phagocytic cells (i.e., reactive oxygen species [ROS]/reactive nitrogen species, lysosome, iron uptake, and transport), whereas nonphagocytic populations had increased ribosomal, IFN, and hypoxia signatures. scRNA-seq also revealed a robust ROS profile, which led to the exploration of craniotomy infection in NADPH oxidase 2 knockout mice. S. aureus burden, leukocyte recruitment, and intracellular bacterial load were significantly increased in NADPH oxidase 2 KO compared with wild-type animals. Collectively, these results highlight the importance of ROS generation in phagocytes for S. aureus biofilm containment, but not clearance, during craniotomy infection.

Investigation of the Effects of Large Bone Flap Craniotomy on Cerebral Hemodynamics, Intracranial Infection Rate, and Nerve Function in Patients with Severe Craniocerebral Trauma

In order to explore the clinical value of large bone flap craniotomy, the effects of standard large bone flap craniotomy on cerebral hemodynamic indexes, incidence of postoperative intracranial infection, and neurological function in patients with severe craniocerebral trauma are investigated. 89 patients with severe craniocerebral trauma admitted from January 2020 to June 2021 are analyzed retrospectively. All patients are divided into a large craniotomy group (n = 45) and control group (n = 44) according to different surgical methods. The large craniotomy group is treated with large craniotomy decompression, and the control group is treated with traditional craniotomy decompression. The incidence of intracranial infection in each group is recorded, and NIHSS is applied to observe the neurological function recovery of 2 groups before and 1 month after operation. Besides, the patients are followed up after surgery and the Kaplan-Meier survival curve is obtained to compare the survival rate of patients in the two groups. It is clearly evident that the two surgical methods have certain clinical efficacy in the treatment of patients with severe craniocerebral trauma. Comparatively, the large craniotomy can further improve brain blood supply and improve neurological function recovery. Also, it can obtain low incidence of postoperative adverse reactions and intracranial infection.