Introduction: Posterior spinal fusions (PSF) can treat numerous spinal pathologies, but may be complicated by surgical site infections (SSI). Patients undergoing long-segment fusions may be at higher risk of SSI. Identifying factors associated with SSI and its sequelae could help risk stratify patients and tailor clinical management.
Methods: We identified and retrospectively analyzed all long-segment PSFs (7 or more levels) performed at our institution from 2000 to 2015. Data was collected on patients' clinical characteristics, procedural factors, and antimicrobial management, and multivariable analysis identified factors independently associated with the outcomes of interest.
Results: 628 patients were identified. SSI was associated with steroid use (p=0.024, OR=2.54), and using cefazolin (p<0.001, OR=4.37) or bacitracin (p=0.010, OR 3.49) for antibiotic irrigation, as opposed to gentamicin or other irrigants. Gram-positive infections were more likely with staged procedures (p=0.021, OR 4.91) and bacitracin irrigation (p<0.001, OR=17.98), and less likely with vancomycin powder (p=0.050, OR 0.20). Gram-negative infections were more likely with a history of peripheral vascular disease (PVD) (p=0.034, OR=3.21) or cefazolin irrigation (p<0.001, OR 25.47). Readmission within 30 days was more likely after staged procedures (p=0.003, OR=3.31), cervical spine surgery (p=0.023, OR=2.28), or cefazolin irrigation (p=0.039, OR=1.85). Any reoperation within 30 days was more common with more comorbid diagnoses (p=0.022, OR 1.09), staged procedures (p<0.001, OR=4.72), cervical surgeries (p=0.013, OR=2.36), more participants in the surgery (p=0.011, OR=1.06), using cefazolin (p<0.001, OR=3.12) or bacitracin (p=0.009, OR=3.15) irrigation, and higher ESR at readmission (p=0.009, OR=1.04). Washouts were more likely among patients with more comorbid diagnoses (p=0.013, OR=1.16), or who used steroids (p=0.022, OR=2.92), and less likely after cervical surgery (p=0.028, OR=0.24). Hardware removal was more common among patients who used bacitracin for irrigation (p=0.013, OR=31.76).
Conclusions: Whether a procedure is staged, and choice of antibiotic irrigation, affects risk of SSI and the subsequent management required.
Patient Care: Patients undergoing long segment posterior spinal fusions are particularly at a higher risk of post operative SSI, 30 day reoperation and readmission. Specific modifiable risk factors are associated are identified some of which are novel. There is an opportunity to optimize these factors preoperatively
Learning Objectives: Patients undergoing long segment posterior spinal fusions are particularly at risk of postoperative SSI.
In this population and following controlling of multiple confounders the choice of antibiotic irrigation and staged procedures were significant risk factors
30 day reoperation and readmission were associated with more comorbid diagnosis, staged surgeries and, more participant surgeons during surgery.