Risk factors for surgical site infection and urinary tract infection after spine surgery

This study aimed to identify and compare risk factors for surgical site infection (SSI) and non-surgical site infections (non-SSIs), particularly urinary tract infection (UTI), after spine surgery. We retrospectively reviewed 825 patients (median age 59.0 years (range 33-70 years); 442 males) who underwent spine surgery at Kagoshima University Hospital from January 2009 to December 2014. Patient parameters were compared using the Mann-Whitney U and Fisher's exact tests. Risk factors associated with SSI and UTI were analyzed via the multiple logistic regression analysis. P < 0.05 was considered statistically significant. SSI occurred in 14 of 825 cases (1.7 %), and non-SSI occurred in 23 of 825 cases (2.8 %). Most non-SSIs were UTIs (20 of 23 cases, 87.0 %). In the 14 patients with SSI, UTI occurred before SSI onset in one patient, and after SSI onset in two patients. UTI onset before SSI was not a risk factor for SSI. Multiple logistic regression analysis indicated that common risk factors for SSI and UTI were operation time (P = 0.0019 and 0.0162, respectively) and ASA classification 3 (P = 0.0132 and 0.0356, respectively). The 1 week post-operative C-reactive protein (CRP) level was a risk factor for UTI (P = 0.0299), but not for SSI (P = 0.4996). There was no relationship between SSI and symptomatic UTI after spine surgery. Risk factors for post-operative SSI and UTI were operative time and ASA classification 3; 1 week post-operative CRP was a risk factor for UTI only.