Antibiotic Prophylaxis in Instrumented Lumbar Spine Surgery: Cefazolin Outperforms Clindamycin Regardless of Duration

<b>Background:</b> Surgical site infections (SSIs) are a significant postoperative complication in instrumented lumbar spine surgery, and the selection and duration of appropriate prophylactic antibiotics are key to their prevention. The aim of our study was to evaluate the effectiveness of various prophylactic antibiotics, primarily cefazolin and clindamycin, as well as the role of the duration of antibiotic prophylaxis in the development of SSI in instrumented lumbar spine surgeries through retrospective analysis. <b>Methods:</b> We performed a retrospective analysis of data from 915 patients who underwent instrumented lumbar spine surgery between 2016 and 2024 in a university center database. We examined the incidence of SSI according to the type of antibiotic used (cefazolin 1 g or 2 g, or clindamycin 0.6 g) and the duration of prophylaxis (single dose versus 72 h administration). We used the Fisher test and Welch test as a statistical analysis to examine the differences between SSI rates. <b>Results:</b> The incidence of SSI was 11.7%. We measured a significantly lower infection rate with cefazolin compared to clindamycin (OR = 0.45; 95% CI: 0.23-0.94; <i>p</i> = 0.0206), regardless of the duration of antibiotic administration. The 72 h cefazolin prophylaxis showed a slight but statistically insignificant advantage over single dose prophylaxis. The risk of SSI was significantly higher in multi-segment surgeries (<i>p</i> = 0.0005). <b>Conclusions:</b> Cefazolin is a more effective prophylactic antibiotic than clindamycin during instrumented lumbar spine surgery. The duration of antibiotic administration has less influence on the risk of SSI development; therefore, short-term, adequate-dose cefazolin prophylaxis is recommended, which also minimizes the risk of antimicrobial resistance and side effects.