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Abstract

Purpose

Despite systemic antibiotics and topical vancomycin powder, deep surgical-site infections (SSIs) remain a devastating complication of major posterior spine surgery, driving morbidity, costs, and antimicrobial resistance. In this study, we aimed to compare deep surgical-site infection (SSI) incidence following major posterior spine surgery between patients receiving intraoperative hypochlorous acid (HOCl) lavage and a historical control group receiving intrawound vancomycin powder.

Methods

In this retrospective comparative study, 161 patients undergoing major posterior spinal surgery received ≥2L of topical HOCl lavage, while 88 historical controls received intra-wound vancomycin powder. The primary endpoint was deep SSI incidence within 12 months. Demographics, operative variables, and microbiological data were analyzed with rigorous statistical methods.

Results

Deep SSI rates were nearly identical: 3.1% (5/161) with HOCl versus 3.4% (3/88) with vancomycin (p = 0.999), with no HOCl-related adverse effects. Pathogen profiles (including MRSA, S. epidermidis, and E. coli) were comparable between groups, underscoring HOCl’s broad-spectrum efficacy.

Conclusion

HOCl lavage showed similar deep SSI rates to intrawound vancomycin powder in this retrospective cohort; prospective multicenter studies are warranted to validate these findings and define optimal protocols.

Keywords

spine surgery surgical site infection hypochlorous acid vancomycin wound irrigation infection prophylaxis

Introduction

Surgical site infections (SSIs) remain one of the most formidable challenges in spine surgery, particularly in instrumented fusion procedures, where they threaten implant retention, fusion success, and patient recovery. With reported infection rates ranging from 2% to 20% depending on patient risk factors, SSIs can lead to devastating sequelae—pseudarthrosis, osteomyelitis, implant failure, and even permanent neurological deficits while imposing a staggering burden on healthcare systems.^1–3 Despite standardized intravenous antibiotic prophylaxis, the rise of resistant pathogens demands innovative, non-antibiotic adjuncts to break this cycle.

Enter hypochlorous acid (HOCl) a potent, endogenous antimicrobial produced by neutrophils with rapid, broad-spectrum activity against biofilm-forming bacteria, including those plaguing spinal implants.⁴ While topical vancomycin powder has gained traction for SSI prevention, its long-term viability is clouded by emerging resistance concerns and cytotoxic risks.⁵ HOCl, in contrast, offers a physiologically harmonious alternative: it mimics the body’s innate immune response, eliminates pathogens without fostering resistance, and has demonstrated remarkable efficacy in chronic wound and biofilm-associated infections.

Yet, despite its promise, HOCl’s role as an intrawound irrigation agent in spine surgery remains underexplored. No prior study has directly compared HOCl lavage against vancomycin powder, the current adjunctive standard leaving a critical evidence gap. This investigation bridges that gap, rigorously evaluating HOCl’s potential to redefine infection prophylaxis in spine surgery. Given increasing attention to antimicrobial stewardship and resource use, evaluating non-antibiotic adjuncts is of interest; however, the present study focuses on clinical outcomes and safety rather than formal cost-effectiveness.

We hypothesized HOCl would be associated with comparable deep SSI rates; findings are intended to inform future prospective evaluation. By providing an initial head-to-head comparison, this study aims to generate preliminary evidence on the role of HOCl lavage in SSI prophylaxis after spine surgery and to inform the design of future prospective studies, with potential relevance to antimicrobial stewardship and value-based care.

Material and Methods

Study design and ethical approval

We conducted a single-center, retrospective cohort study following approval by the University Clinical Research Ethics Committee (ATADEK 2020-01/9; 9 January 2020). All procedures adhered to the Declaration of Helsinki, and written informed consent was obtained from every participant.

Patient selection and cohort definition

From January 2015 to December 2016, we identified 249 adult patients who underwent major posterior spinal instrumentation and fusion. Both interventions were used contemporaneously during the same calendar period; accordingly, the HOCl lavage and intrawound vancomycin powder groups represent parallel cohorts within a single study window, rather than temporally separated cohorts. The calendar period for both cohorts was January 2015–December 2016, which minimizes potential bias related to secular changes in perioperative practice. Importantly, all cases were managed by a dedicated surgical team following a standardized institutional perioperative protocol (including skin preparation, systemic antibiotic prophylaxis, drain policy, and follow-up schedule), thereby reducing variability unrelated to the intrawound prophylaxis strategy. To ensure cohort homogeneity, we excluded individuals with active surgical-site infection, anterior or minimally invasive/endoscopic approaches, decompression-only procedures, and microdiscectomies. Patients were stratified into two groups:

HOCl Group (n = 161): Received intraoperative gravity irrigation with ≥2 L of hypochlorous acid (HOCl), allowing a standardized 5 minute intra-wound contact time before closure.

Vancomycin Group (n = 88): Historical controls treated with 1 g of topical intrawound vancomycin powder prior to wound closure.

Perioperative protocol

All surgeries were performed by a single senior spine surgeon under general anesthesia with the patient in the prone position. Preoperative skin preparation comprised 10% povidone–iodine, and standard sterile draping was applied. Intravenous cefazolin (2 g) was administered within 60 min before incision, followed by 1 g every 6 h for 24 h postoperatively. After definitive instrumentation and meticulous hemostasis, HOCl irrigation was performed. HOCl was used as a commercially prepared, ready-to-use solution. The solution concentration was 0.020% HOCl with pH-4,5 (manufacturer specifications). A minimum of 2 L was delivered via gravity irrigation with a standardized 5-min wound-bed contact time prior to closure, as described above. The antimicrobial rationale is based on HOCl’s rapid oxidative activity (mimicking the innate neutrophil oxidative burst) with broad-spectrum efficacy against planktonic and biofilm-associated organisms.

In the control cohort, 1 g sterile vancomycin powder was applied topically to the surgical wound immediately prior to fascial closure. The powder was distributed evenly across the deep wound bed (paraspinal musculature and decorticated bony surfaces) while avoiding direct placement on exposed dura/neural elements.

In both groups, subfascial drains were placed and removed aseptically within 24 h, independent of output volume.

Outcome assessment and follow-up

The primary endpoint was the incidence of deep surgical-site infection (SSI) as defined by Centers for Disease Control and Prevention criteria. Patients underwent standardized clinical evaluations and laboratory monitoring for a minimum of 12 months postoperatively to capture both early and late‐onset infections.

Data collection and statistical analysis

We recorded patient demographics (age, sex, ASA physical status), surgical indications (degenerative, deformity, trauma, tumor), and surgical parameters (number of fusion levels, operative duration, estimated blood loss, length of stay). Continuous variables are presented as mean ± SD or median (range) and compared using independent two-sample t-tests. Categorical variables are expressed as counts and percentages and analyzed with Pearson’s chi-square, Fisher’s exact, or Fisher–Freeman–Halton tests as appropriate. All analyses were performed in SPSS v30 (IBM Corp., Armonk, NY), with two-tailed p < 0.05 denoting statistical significance. This retrospective study was not planned as a non-inferiority trial, and no non-inferiority margin (Δ) was prespecified. We report between-group comparisons using Fisher’s exact test and provide the absolute risk difference with 95% CI as an effect estimate.

Methodological innovations

First Direct Comparison: This investigation represents the inaugural head-to-head evaluation of intrawound HOCl lavage versus topical vancomycin powder in major posterior spine surgery.

Standardized Protocol: We defined a reproducible irrigation regimen (≥2 L HOCl; 5 min contact) to facilitate immediate clinical translation.

Extended Surveillance: A 12-months follow-up period enhances detection of late-presenting SSIs, surpassing the shorter monitoring intervals of prior studies.

Results

The cohort comprised 249 patients (HOCl n = 161; vancomycin n = 88), whose baseline characteristics were statistically equivalent (Table 1). Mean ages were 49.95 ± 22.57 years (HOCl) versus 50.77 ± 22.47 years (control; p = 0.784), and gender distribution (41.0% male vs 45.5%; p = 0.496), ASA scores (54.0% vs 47.7% ASA I–II; p = 0.720), diagnostic categories (degenerative 56.5% vs 60.2%; p = 0.971), and fusion levels (<3 levels in 19.4% vs 21.6%; p = 0.692) demonstrated no intergroup differences.

Table 1.

Comparison between the treatment and control groups.

Characteristic	Control group (vancomycin +)	Treatment group (HOCL lavage+)	p
Total no. of patients	88	161
Age (yr)	50.77 ± 22.47	49.95 ± 22.57	0.784^a
Sex
Male	40 (45.5%)	66 (41.0%)	0.496^b
Female	48 (54.5%)	95 (59.0%)
American Society of Anesthesiologists physical status classification
I	42 (47.7%)	87 (54.0%)	0.720c
II	27 (30.7%)	45 (28.0%)
III	17 (19.3%)	27 (16.8%)
IV	2 (2.3%)	2 (1.2%)
Diagnosis
Deformity	9 (10.2%)	19 (11.8%)	0.971^b
Degenerative	53 (60.2%)	91 (56.5%)
Trauma	8 (9.1%)	17 (10.6%)
Tumor	11 (12.5%)	19 (11.8%)
Others	7 (8.0%)	15 (9.3%)
Instrumentation
Yes	143 (97.9%)	143 (88.8%)	0.002^b
No	3 (2.1%)	18 (11.2%)
Vertebral fusion
<3	19 (21.6%)	26 (19.4%)	0.692^b
≥3	69 (78.4%)	108 (80.6%)
No. of vertebral fusion	4 (0–18)	4 (0-7)
Surgery duration (min)	330 (120–600)	300 (90-600)
Blood loss (mL)	400 (50–6000)	400 (0-6000)
Hospitalization period (day)	4 (1–18)	3 (0-38)

n (%); Mean ± SD; Median (Min-Max).

^aTwo independent samples t-test.

^bPearson’s Chi-square test.

^cFisher-Freeman-Halton test.

Deep SSI rates were similar in the HOCl and vancomycin groups (3.1% vs 3.4%; Fisher’s exact p = 0.999). The absolute risk difference (HOCl − vancomycin) was −0.3% with a 95% CI that suggests any true difference is small; however, this analysis is descriptive/exploratory and should not be interpreted as formal non-inferiority (Table 2). Thus, even under a stringent harm threshold, HOCl irrigation appears clinically similar to vancomycin powder for infection prevention.

Table 2.

Deep surgical site infections after spine surgery in the treatment and control groups.

Enfection	Control group (vancomycin +)		Treatment group (HOCL lavage +)		Total		p
Enfection	n	%	n	%	n	%	p
No	85	96.6	156	96.9	241	96.8	0.999^a
Yes	3	3.4	5	3.1	8	3.2
Total	88	100.0	161	100.0	249	100.0

^aFisher’s Exact test.

Pathogen profiles differed: HOCl‐irrigated wounds yielded Staphylococcus epidermidis (n = 3), MRSA (n = 1), and Escherichia coli (n = 1), whereas the vancomycin cohort cultured E. coli (n = 2) and P. aeruginosa (n = 1). All SSIs were successfully managed with prompt surgical debridement and IV antibiotics; two cases in the HOCl arm required adjunctive vacuum-assisted closure (Table 3).

Table 3.

Patients with deep surgical site infection and their treatments.

Group	Age	Sex	Diagnosis	# of fusion levels	ASA status	Surgery duration (min)	Blood loss (mL)	Site	Culture	Treatment
1.Control	79	F	Degenerative	7	I	300	600	Deep	Escherichia coli	Debridement, IV antibiotics
2.Control	74	F	Degenerative	8	I	450	600	Deep	Pseudomonas aeruginosa	Debridement, IV antibiotics, VAC
3.Control	35	F	Others	10	I	450	1500	Deep	Escherichia coli	Debridement, IV antibiotics
4.Treatment	68	M	Degenerative	8	II	300	500	Deep	Methicillin	Debridement, IV antibiotics, VAC
									Rresistant
									Staphylococcus aureus (MRSA)
5.Treatment	69	M	Degenerative	10	I	350	600	Deep	Staphylococcus epidermidis	Debridement, IV antibiotics
6.Treatment	74	F	Degenerative	8	I	400	450	Deep	Staphylococcus epidermidis	Debridement, IV antibiotics
7.Treatment	50	F	Degenerative	8	I	300	450	Deep	Staphylococcus epidermidis	Debridement IV antibiotics
8.Treatment	73	M	Degenerative	7	I	350	400	Deep	Escherichia coli	Debridement IV antibiotics

ASA status, American Society of Anesthesiologists physical status classification; F, female; IV, intravenous; VAC, vacuum-assisted closure.

Safety and feasibility

No HOCl-related adverse events such as wound erythema, delayed healing, or systemic effects occurred (0/161). Mean additional irrigation time was 10 minutes, with no impact on total operative duration.

Discussion

Surgical site infections (SSIs) after spine surgery, especially in patients undergoing instrumentation and multilevel fusion, continue to pose a serious clinical and economic burden. Consistent with the literature, our findings confirm that Staphylococcus species chiefly Staphylococcus epidermidis, followed by MRSA and Escherichia coli remain the predominant pathogens in postoperative spinal SSIs.^1–3,5 In this study, deep SSI incidence in the HOCl irrigation group was 3.1%, virtually identical to the 3.4% observed in the historical vancomycin cohort (p = 0.999),⁵ demonstrating that HOCl irrigation achieves similar prophylaxis in real-world practice. Balanced baseline characteristics and identical perioperative protocols eliminate major confounders, affirming the validity of our findings.

Prophylaxis demands not only efficacy but also safety and operational simplicity. While standard IV antibiotic regimens are indispensable, rising antimicrobial resistance underscores the need for adjunctive, non-antibiotic antiseptics with proven biofilm activity.⁶ Antiseptic wound irrigation prior to skin closure has repeatedly reduced postoperative infection rates, a principle reinforced by our data.⁷ Przybyl et al. highlighted clinical advantages of 0.08% HOCl over conventional antiseptics, including superior tolerability,⁸ and Armstrong et al. confirmed that HOCl matches or exceeds other agents in antimicrobial potency without cytotoxicity, with robust evidence in diabetic foot and septic wound care.⁹

HOCl’s unique strengths derive from its endogenous origin: generated by neutrophil myeloperoxidase, it exerts broad-spectrum oxidizing action against biofilm-forming bacteria, spores, fungi, and enveloped viruses within seconds.^10,11 Kramer et al. demonstrated that HOCl not only outperforms polyhexanide/betaine in biofilm eradication but also acts more rapidly than povidone-iodine, octenidine, and polyhexanide.¹¹ Crucially, no HOCl-related adverse events were observed among our 161 patients, corroborating extensive reports of its non-cytotoxic safety across surgical and chronic wound settings.^8,9,11

Beyond antimicrobial efficacy and safety, HOCl irrigation delivers decisive practical and economic benefits. A simple gravity-fed lavage for 10 minutes integrates seamlessly into standard surgical workflows, avoiding the dosing, storage, and resistance concerns linked to topical vancomycin powder.^5,12 Cost analyses demonstrate HOCl’s marked affordability and accessibility, even in resource-limited settings, thereby supporting antimicrobial stewardship and reducing overall healthcare expenditures.^13,14 Although HOCl solutions may have practical advantages related to availability and handling, the present study did not include a formal cost analysis; therefore, any economic implications should be interpreted cautiously. Future prospective studies should incorporate standardized cost components (product cost, operating-room time, downstream resource use) to determine cost-effectiveness.

Our study’s robust design, one of the largest single-center retrospective comparisons with a well-matched historical control and comprehensive 12-months follow-up ensures reliable, generalizable results. Equivalent baseline demographics, ASA scores, fusion levels, operative parameters, and postoperative care effectively eliminate major confounders, reinforcing the validity of our conclusions. Although retrospective bias and culture-based detection limits remain, our standardized protocols and cohort size substantially mitigate these concerns, paving the way for future prospective, randomized trials to refine HOCl dosing and timing. Second, we did not perform a formal cost or cost-effectiveness analysis; thus, economic comparisons between HOCl and vancomycin powder cannot be concluded from these data.

Conclusion

In this retrospective cohort, HOCl lavage was associated with deep SSI rates similar to those observed with intrawound vancomycin powder. Given the study design, these results should be considered hypothesis-generating and require confirmation in prospective, ideally randomized, multicenter trials.

Footnotes

ORCID iD

Vugar Nabi

Ethical considerations

The study was conducted in compliance with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of Acibadem Mehmet Ali Aydinlar University (Ethics No. ATADEK 2020-01/9; 9 January 2020).

Consent to participate

All patients were preoperatively informed about the nature and scope of the surgical procedure, and written informed consent was obtained. The surgical consent form included a dedicated section allowing the anonymized use of patient data for academic research purposes, which was explicitly reviewed and approved by the aforementioned ethics committee.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The datasets generated and/or analyzed during the current study are available from the corresponding author by reasonable request.*

Appendix

References

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Hypochlorous acid lavage versus intrawound vancomycin powder for prevention of deep surgical-site infection after major posterior spine surgery: A retrospective case series with a historical control group

Abstract

Purpose

Methods

Results

Conclusion

Keywords

Introduction

Material and Methods

Study design and ethical approval

Patient selection and cohort definition

Perioperative protocol

Outcome assessment and follow-up

Data collection and statistical analysis

Methodological innovations

Results

Safety and feasibility

Discussion

Conclusion

Footnotes

ORCID iD

Ethical considerations

Consent to participate

Funding

Declaration of conflicting interests

Data Availability Statement

Appendix

References