Infection of the surgical site following spine surgery is a dangerous post-operative complication that can result in prolonged recovery time, poor wound healing, the need for further treatment, as well as more serious consequences like sepsis, organ failure, and even death.¹ Even though incision sites are kept sterile throughout the procedure, infections are relatively common: a study of 108,419 spinal procedures found that between 2.1 and 5.4 percent of patients contracted some type of infection.² Moreover, it was found that certain factors increased risk of infection, including revision surgery, spinal fusion, and placement of implants.¹ It is therefore of clinical relevance to characterize and determine preventative methods for surgical site infection following spine surgery.

Such infections have generally been attributed to infiltration of the open wound by gram-positive bacteria present on the skin, such as Staphylococci and Streptococci.³ However, a recent publication by Long et al. revealed that many other microbial agents may also be involved.⁴ The study examined 351 infections following spinal fusion surgery and noted that a diverse range of microbes were responsible: around 44 percent of infections were multi-microbial, and 20 percent of mono-microbial infections were caused by enteric (non-gram-positive) species. Additionally, the authors reported an anatomic gradient of infectious agents: gram-positive infections tended to manifest near the cervical spine, whereas enteric infections were more common in the lumbosacral spine. These findings would suggest that epidermal flora varies drastically along the spine and that preventative treatment for infection should adjust accordingly.

Long et al. also evaluated the effectiveness of multiple surgical antibiotic prophylaxis regimens. Patients included in the study were treated with cefazolin, cefazolin plus vancomycin, vancomycin only, or clindamycin only. It was found that over half of the infection cases developed at least one prophylactic antibiotic-resistant microbe, and that the most common of these was cefazolin-resistant enteric species in the lower thoracic and lumbosacral regions. The second most common was methicillin-resistant gram-positive infections in the cervical and upper thoracic regions. These findings would again indicate anatomical specificity in skin flora, which could be used to anticipate microbial antibiotic resistance.

The authors recommended that physicians implement a more rigorous anti-gram-negative microbial regimen, including improved implementation of protocols for mobility, toileting, and pain control, standardized drain management, and use of incisional negative-pressure wound therapy (NPWT). These measures should be considered particularly in patients who have a high risk for gram-negative infections, such as those who have undergone cervical and upper-thoracic spinal fusion surgery. Given that the majority of MRSA infections occurred in patients who tested negative for MRSA preoperatively, the authors also suggested increasing screening sensitivity for MRSA by testing multiple sites and using PCR-based assays.

The study’s findings hold major implications for the prevention of surgical site infection following spine surgery. Physicians may use the anatomical gradient to predict, characterize, and avert microbial infections.

References 

1. TorpyJM, Burke AE, Glass RM (2010). Postoperative Infections. JAMA. https://doi.org/10.1001/jama.303.24.2544 
2. Smith, J. S.,Shaffrey, C. I., Sansur, C. A., Berven, S. H., Fu, K. M., Broadstone, P. A., Choma, T. J., Goytan, M. J., Noordeen, H. H., Knapp, D. R., Jr, Hart, R. A., Donaldson, W. F., 3rd, Polly, D. W., Jr, Perra, J. H., Boachie-Adjei, O., & Scoliosis Research Society Morbidity and Mortality Committee (2011). Rates of infection after spine surgery based on 108,419 procedures: a report from the Scoliosis Research Society Morbidity and Mortality Committee. Spine, 36(7), 556–563. https://doi.org/10.1097/BRS.0b013e3181eadd41 
3. Stonham, C. (2009). A Manual of Surgery. 3 vol.
4. Long, D. R., Bryson-Cahn, C.,Pergamit, R., Tavolaro, C., Saigal, R., Chan, J. D., & Lynch, J. B. (2021). 2021 Young Investigator Award Winner: Anatomic Gradients in the Microbiology of Spinal Fusion Surgical Site Infection and Resistance to Surgical Antimicrobial Prophylaxis. Spine, 46(3), 143–151. https://doi.org/10.1097/BRS.0000000000003603