Comorbidities increase the risk of surgical site infections

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Steven Kurtz, Exponent Inc, Philadelphia, USA, and others reported in the Journal of Neurosurgery: Spine that patient comorbidities are the greatest risk factor for surgical site infections (SSIs) after instrumented lumbar spine fusion.

Using data from a Medicare population, Kurtz et al identified patients who underwent instrumented lumbar spine fusion between January 1997 and December 2009. They assessed the prevalence of deep and superficial infections among this population and correlated the prevalence with preoperative risk factors.

Krutz et al found that overall, during 10-years of follow-up, that SSIs were present in 8.5% of primary procedures and in 12.2% of revisions. They wrote: “Among the factors considered, the overall infection risk (including superficial and deep infection) within 10 years was most influenced by comorbidities: for a Charlson Comorbidity Index score of five versus 0, the adjusted hazard ratio (AHR) was 2.48 (p<0.001).” They added that a higher number of levels being fused (≥9 vs. 2–3), revision (rather than primary) surgery, obesity, surgical approach, lower socioeconomic status, and age were also found to increase the risk of a SSI. However, although the AHR was 1.54 for patients aged ≥85 years compared with patients aged 65-69 years, it was 0.792 for patients aged 75-79 years compared with patients aged 65-69 years.

The authors commented that compared with the number of risk factors for SSIs overall (including both deep and superficial infections), there were fewer significant risk factors for deep infections alone. These risk factors included number of levels fused, history of previous surgery, and diagnosis of obesity.

Kurtz et al concluded that the “high rate” of infections observed following instrumented fusion “warrants increased focus in infection risk mitigation, especially for patients with comorbid conditions.”