9. The impact of nasal screening for methicillin-resistant staphylococcus aureus on surgical site infection after primary lumbar fusion

Abstract

<h3>BACKGROUND CONTEXT</h3> Surgical site infections (SSI) constitute significant morbidity in spine surgery. Efforts at SSI prevention include preoperative methicillin-resistant Staphylococcus aureus (MRSA) screening and decolonization, with demonstrated success for arthroplasty patients along with vascular and cardiothoracic surgical patients. The variety of surgical approaches and anatomic regions within spine surgery can limit the impact of analyses at the subspecialty level. Despite the success of MRSA nasal screening and decolonization in reducing SSI rates in other disciplines, the impact on spine surgery is less understood. <h3>PURPOSE</h3> To determine the relationship between nasal MRSA testing and operative debridement rates for surgical site infection after primary lumbar fusion. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort study at two academic tertiary referral centers. <h3>PATIENT SAMPLE</h3> Adult patients (>18 years) were identified from January 2015 to March 2020 based on CPT codes for spinal instrumentation and fusion. Inclusion criteria were primary instrumented posterior lumbar fusion between 1-3 levels and exclusion criteria were revision surgery, tumor, infection, lateral-only surgery or operative surgeon with fewer than 20 cases. <h3>OUTCOME MEASURES</h3> Operative incision and drainage (I&D) of the index lumbar spine wound within 90-days after surgery was the primary outcome. <h3>METHODS</h3> Chart text, operative reports and laboratory reports were reviewed for data abstraction. Multivariable logistic regression modeling assessed for demographic differences between MRSA testing groups as well as factors contributing to I&D risk. <h3>RESULTS</h3> There were 2,148 patients included with a mean age 62.5 (SD 12.9), 56.9% female, and mean BMI 29.4 (SD 6.2). MRSA testing 90 days prior to surgery was completed in 884 (41.1%) of patients, and 19 (2.2%) of tested patients were colonized with MRSA preoperatively. Thirty-six (1.7%) patients underwent surgical I&D within 90 days of their index procedure for a surgical site infection. I&D risk was not associated with presence or result of MRSA testing, preoperative mupirocin prescriptions, or type of intraoperative antibiotic after controlling for surgeon. I&D risk was associated with higher BMI (5.7% increased risk for every 1 unit increase in BMI or a coefficient of 0.057, 95% confidence interval 0.017 to 0.097, p = 0.005) after controlling for age, diabetes and smoking status. <h3>CONCLUSIONS</h3> The present study demonstrates no difference in surgical I&D rates between patients who underwent MRSA testing, who had positive MRSA colonization or who underwent other interventions aimed at decreasing SSI rates such as preoperative mupirocin decolonization or addition of intraoperative vancomycin. Increased BMI was associated with risk of undergoing an operative I&D for surgical site infection, suggesting that patient factors dominate over clinical interventions in the prevention of surgical site infection after primary lumbar spine fusion. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.