Comparative effectiveness of gram-positive versus mixed antibiotic prophylaxis on surgical site infection rates following three-column osteotomy for adult spinal deformity.

BACKGROUND

Surgical Site Infection (SSI) remains a major complication following spine surgery, particularly in complex procedures such as three-column osteotomies (3COs), where infection rates may reach up to 35 %. Standard perioperative antibiotic protocols primarily target gram-positive organisms, yet gram-negative bacteria have been increasingly implicated in SSIs, raising concerns about the adequacy of current prophylactic regimens. This study aims to evaluate whether the addition of gram-negative antibiotic coverage to standard gram-positive prophylaxis (Mixed Coverage, MC) reduces the incidence of SSI in adult patients with spinal deformity undergoing high-grade osteotomies.

METHODS

We retrospectively analyzed 236 adult patients who underwent lumbar 3CO and spinopelvic fixation at a tertiary academic center. Patients were divided into two sequential cohorts based on a change in institutional antibiotic prophylaxis protocol: gram-positive coverage alone (GPC, n = 128) and combined gram-positive and gram-negative coverage (MC, n = 108). The primary endpoint was SSI occurrence, categorized as superficial or deep. Statistical comparisons included both univariate and multivariate analyses.

RESULTS

Univariate analysis demonstrated a significantly lower SSI rate in the MC group (3 %) compared to the GPC group (10 %) (p = 0.03). However, after multivariate adjustment, the difference was not statistically significant (OR = 0.31, 95 % CI: 0.09 - 1.04, p = 0.059). Rates of deep infections (GPC: 2.4 %, MC: 0 %, OR = not estimable) and bacteremia (GPC: 3.9 %, MC: <1 %, OR = 4.1, p = 0.14) were also higher in the GPC group, though these differences did not reach statistical significance.

CONCLUSIONS

While univariate analysis suggests a potential benefit from adding gram-negative coverage, multivariate analysis did not confirm this effect. Larger prospective studies are needed to assess the efficacy and safety of expanded prophylactic regimens in high-risk spinal deformity surgery.