Unexpected intraoperative positive culture (UIPC) in presumed aseptic revision spine surgery: a systematic review and meta-analysis

Does intraoperative antiseptic solution soaking reduce microbial contamination in spine surgery? A randomized controlled trial

BACKGROUND CONTEXT

Surgical site infections (SSIs) are a significant complication in spine surgery, particularly in instrumented procedures, leading to increased morbidity and healthcare costs. Despite standard preoperative disinfection protocols, bacterial contamination remains prevalent. Strategies such as intraoperative antiseptic irrigation have been explored to mitigate contamination, yet the comparative efficacy of different antiseptic solutions remains unclear.

PURPOSE

This study aimed to evaluate the effectiveness of intraoperative antiseptic solution soaking with normal saline (NS), povidone-iodine (PVP-I), and chlorhexidine gluconate (CHG) in reducing bacterial contamination in lumbar instrumented fusion surgery.

STUDY DESIGN/SETTING

A single-center, single-blinded, randomized controlled trial was conducted at a tertiary medical center in Taiwan.

PATIENT SAMPLE

A total of 105 patients undergoing posterior lumbar interbody fusion surgery were enrolled and randomly assigned to three groups: NS (n=35), PVP-I (n=35), or CHG (n=35). Patients with prior lumbar procedures, known allergies to antiseptics, previous spinal infections, trauma, or tumors were excluded.

OUTCOME MEASURES

The primary outcome was the reduction in bacterial contamination, assessed via intraoperative cultures from three sites-superficial tissues, deep tissues, and implant surfaces-before and after antiseptic irrigation. Secondary outcomes included the incidence of postoperative SSIs and clinical complications over a 6-month follow-up period.

METHODS

Patients were randomized into three groups, each receiving a 3-minute soak with the assigned antiseptic solution before wound closure, followed by normal saline irrigation. Swab samples were collected pre- and postirrigation for bacterial culture and 16S rRNA PCR analysis. Statistical analysis was performed using logistic regression and Bonferroni correction for multiple comparisons.

RESULTS

Among 105 patients, preirrigation bacterial culture positivity rates were 49.5% in superficial tissues, 31.4% in deep tissues, and 32.4% on implants. Postirrigation, NS showed no significant bacterial reduction, while PVP-I reduced superficial contamination (55.0%, p=.015) but no significant effect in deeper tissues and implants. CHG showed the greatest bacterial reduction, significantly outperforming NS (OR: 0.06, 95% CI: 0.01-0.54, p=.011) and PVP-I (OR: 0.06, 95% CI: 0.01-0.56, p=.012) on implant surfaces. Despite these differences in culture rate, SSI rates remained low and comparable among groups (p=.72), with no reported antiseptic-related complications.

CONCLUSION

This study confirms that bacterial contamination remains high despite standard preoperative disinfection in lumbar fusion surgery. Among the tested antiseptic solutions, CHG demonstrated superior efficacy in reducing bacterial residues, particularly on implant surfaces. These findings support CHG as a promising antiseptic for intraoperative irrigation in spine surgery. Further multi-center studies are needed to validate its impact on reducing SSIs and improving long-term outcomes.

LEVEL OF EVIDENCE

Level II.

State-of-the-Art Review: Diagnosis and Management of Spinal Implant Infections

Spinal implant infections are a serious complications of instrumented spinal fusion surgeries, carrying high morbidity and complex management challenges. Early postoperative infections may manifest with wound-healing issues, back pain, and fevers. Magnetic resonance imaging (MRI) is the preferred imaging modality, but can be limited by metal artifacts. For cases with stable implants, surgical debridement with implant retention combined with at least 12 weeks of antibiotics is currently considered appropriate treatment. Staphylococcal infections are ideally treated with biofilm-active antibiotics. Suppressive antibiotic therapy can be considered when surgical debridement has been delayed or is incomplete, and for those who are poor surgical candidates for another surgery. Chronic infections may present insidiously with implant failure or pseudarthrosis; implant removal or revision is generally pursued. As current guidance is heavily based on the periprosthetic joint infection literature and low-level studies on spinal implant infections, further research on optimizing diagnostic and treatment approaches is needed.

Cutibacterium acnes in spine surgery: pathophysiology, diagnosis, and treatment

Cutibacterium acnes (C. acnes) previously named Propionibacterium acnes (P. acnes) has been increasingly recognized by spine surgeons as a cause of indolent postsurgical spinal infection. Patients infected with C. acnes may present with pseudarthrosis or nonspecific back pain. Currently, microbiological tissue cultures remain the gold standard in diagnosing C. acnes infection. Ongoing research into using genetic sequencing as a diagnostic method shows promising results and may be another future way of diagnosis. Optimized prophylaxis involves the use of targeted antibiotics, longer duration of antibiotic prophylaxis, antibacterial-coated spinal implants, and evidence-based sterile surgical techniques all of which decrease contamination. Antibiotics and implant replacement remain the mainstay of treatment, with longer durations of antibiotics proving to be more efficacious. Local guidelines must consider the surge of antimicrobial resistance worldwide when treating C. acnes.