Antibiotic-loaded bone graft for reduction of surgical site infection in spinal fusion

Synthesis and evaluation of a novel vancomycin-infused, biomimetic bone graft using a rat model of spinal implant-associated infection

Background

Postoperative infection is a complication of spinal fusion surgery resulting in increased patient morbidity. Strategies including intraoperative application of powdered vancomycin have been proposed to reduce the incidence of infection; however, such antimicrobial effects are short-lived.

Methods

Instrumentation of the L4-L5 vertebrae was performed mimicking pedicle screw and rod fixation in 30 rats. Titanium instrumentation inoculated with either PBS or 1×105 CFU bioluminescent MRSA, along with biomimetic bone grafts infused with varying concentrations of vancomycin and 125 µg of rhBMP-2 (BioMim-rhBMP-2-VCM) were implanted prior to closure. Infection was quantified during the six-week postoperative period using bioluminescent imaging. Arthrodesis was evaluated using micro-CT.

Results

Infected animals receiving a bone graft infused with low-dose (0.18 mg/g) or high-dose vancomycin (0.89 mg/g) both exhibited significantly lower bioluminescent signal over the six-week postoperative period than control animals inoculated with MRSA and implanted with bone grafts lacking vancomycin (p=.019 and p=.007, respectively). Both low and high-dose vancomycin-infused grafts also resulted in a statistically significant reduction in average bioluminescence when compared to control animals (p=.027 and p=.047, respectively), independent of time. MicroCT analysis of animals from each group revealed pseudoarthrosis only in the control group, suggesting a correlation between infection and pseudoarthrosis. MRSA-inoculated control animals also had significantly less bone volume formation on micro-CT than the PBS-inoculated control cohort (p<.001), the MRSA+low-dose vancomycin-infused bone graft cohort (p<.001), and the MRSA+high-dose vancomycin-infused bone graft cohort (p<.001).

Conclusion

BioMim-rhBMP-2-VCM presents a novel tissue engineering approach to simultaneously promoting arthrodesis and antimicrobial prophylaxis in spinal fusion. Despite mixed evidence of potential osteotoxicity of vancomycin reported in literature, BioMim-rhBMP-2-VCM preserved arthrodesis and osteogenesis with increasing vancomycin loading doses due to the graft's osteoinductive composition.

Reduction of Instrumentation-Related Spine Surgical Site Infections After Optimization of Surgical Techniques. A Single Center Retrospective Analysis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Although surgical risk factors for developing spine surgical site infections (S-SSI) have been identified, the impact of such knowledge in its prevention has not been demonstrated.

METHODS

We evaluated in 500 patients undergoing spine surgery between 2011 and 2019 at Hospital 12 de Octubre the changes in S-SSI rates over time. Surgical variables independently related to S-SSI were analyzed by univariate and multivariate analysis using binary logistic regression models. A case-control sub-analysis (1:4), matched by the surgical variables identified in the overall cohort was also performed.

RESULTS

Twenty cases of S-SSI were identified (4%), with a significant decrease in the incidence rate across consecutive time periods (6.6% [2011-2014] vs .86% [2015-2019]; P-value <.0001)). Multivariate analysis identified arthrodesis involving sacral levels (odds ratio [OR]: 2.57; 95% confidence interval [95%CI]: 1.02-6.47; P-value = .044) and instrumentation over 4-8 vertebrae (OR: 2.82; 95%CI: 1.1-7.1; P-value = .027) as independent risk factors for S-SSI. The reduction in the incidence of S-SSI concurred temporally with a reduction in instrumentations involving 4-8 vertebrae (55% vs 21.8%; P-value <.0001) and sacral vertebrae (46.9% vs 24.6%; P-value <.0001) across both periods. The case-control analysis matched by these surgical variables failed to identify other factors independently related to the occurrence of S-SSI.

CONCLUSIONS

Spinal fusion of more than 4 levels and the inclusion of sacral levels were independently related to the risk of S-SSI. Optimization of surgical techniques by reducing these two types of instrumentation could significantly reduce S-SSI rates.

Strategies to improve bioactive and antibacterial properties of polyetheretherketone (PEEK) for use as orthopedic implants

Polyetheretherketone (PEEK) has gradually become the mainstream material for preparing orthopedic implants due to its similar elastic modulus to human bone, high strength, excellent wear resistance, radiolucency, and biocompatibility. Since the 1990s, PEEK has increasingly been used in orthopedics. Yet, the widespread application of PEEK is limited by its bio-inertness, hydrophobicity, and susceptibility to microbial infections. Further enhancing the osteogenic properties of PEEK-based implants remains a difficult task. This article reviews some modification methods of PEEK in the last five years, including surface modification of PEEK or incorporating materials into the PEEK matrix. For surface modification, PEEK can be modified by chemical treatment, physical treatment, or surface coating with bioactive substances. For PEEK composite material, adding bioactive filler into PEEK through the melting blending method or 3D printing technology can increase the biological activity of PEEK. In addition, some modification methods such as sulfonation treatment of PEEK or grafting antibacterial substances on PEEK can enhance the antibacterial performance of PEEK. These strategies aim to improve the bioactive and antibacterial properties of the modified PEEK. The researchers believe that these modifications could provide valuable guidance on the future design of PEEK orthopedic implants.

Role of Animal Models to Advance Research of Bacterial Osteomyelitis

Osteomyelitis is an inflammatory bone disease typically caused by infectious microorganisms, often bacteria, which causes progressive bone destruction and loss. The most common bacteria associated with chronic osteomyelitis is Staphylococcus aureus. The incidence of osteomyelitis in the United States is estimated to be upwards of 50,000 cases annually and places a significant burden upon the healthcare system. There are three general categories of osteomyelitis: hematogenous; secondary to spread from a contiguous focus of infection, often from trauma or implanted medical devices and materials; and secondary to vascular disease, often a result of diabetic foot ulcers. Independent of the route of infection, osteomyelitis is often challenging to diagnose and treat, and the effect on the patient's quality of life is significant. Therapy for osteomyelitis varies based on category and clinical variables in each case. Therapeutic strategies are typically reliant upon protracted antimicrobial therapy and surgical interventions. Therapy is most successful when intensive and initiated early, although infection may recur months to years later. Also, treatment is accompanied by risks such as systemic toxicity, selection for antimicrobial drug resistance from prolonged antimicrobial use, and loss of form or function of the affected area due to radical surgical debridement or implant removal. The challenges of diagnosis and successful treatment, as well as the negative impacts on patient's quality of life, exemplify the need for improved strategies to combat bacterial osteomyelitis. There are many in vitro and in vivo investigations aimed toward better understanding of the pathophysiology of bacterial osteomyelitis, as well as improved diagnostic and therapeutic strategies. Here, we review the role of animal models utilized for the study of bacterial osteomyelitis and their critically important role in understanding and improving the management of bacterial osteomyelitis.

Negative pharmacological effect on spine fusion: A narrative review of the literature of evidence-based treatment

Spine fusion surgery is commonly performed for diverse indications, the most frequent one being degenerative spine diseases. Despite the growing importance of this surgery, there is limited evidence concerning the effects of drugs on the process of spine fusion and healing. While asymptomatic sometimes, nonunion of the spine can have tremendous repercussions on the patients' quality of life and the healthcare system rendering it an "expensive complication". This literature review identifies the role of some perioperative drugs in spine fusion and reveals their potential role in pseudarthrosis of the spine. This review also benefits spine surgeons looking for current evidence-based practices. We reviewed the data related to nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, vancomycin, bisphosphonates, proton pump inhibitors (PPIs), pregabalin, and opioids. From the available experimental and clinical studies, we conclude that bisphosphonates might positively influence the process of spine fusion, while steroids and vancomycin have shown variable effects, and the remaining medications likely disturb healing and union of the spine. We recommend spine surgeons be cautious about the drugs they resort to in the critical perioperative period until further clinical studies prove which drugs are safe to be used.

Disinfection protocol for human musculoskeletal allografts in tissue banking using hydrogen peroxide 30

Musculoskeletal allografts are used in reconstructive procedures, however, the risk of contamination with potential pathogens is possible, and safe transplantation requires multiple processing considerations. Hydrogen peroxide (H₂O₂) has commonly been used in bone washing because it can remove donor cells and eliminate antigens, pathogens, or cytotoxic agents from the matrix. The aim of this study was to evaluate the quantitative activity of H₂O₂ in a model of bone contamination with a high bacterial load to define the bioburden reduction. Twelve bone disc models were artificially contaminated with Staphylococcus aureus. The bones were treated with a washing process composed by antibiotics, 30% hydrogen peroxide, and 70% alcohol. Tryptic Soy Agar plates were directly inoculated with 100µL of each step of the washing process and colonies were counted in CFU/mL. Scanning electron microscopy was used for bone structural analysis before and after the washing process. After antibiotics, there was a drop of less than 1 log for cancellous bone and almost 1 log for cortical bone. However, after H₂O₂, there as a drop of 3 logs for cortical (p = 0.007), and 2 logs for cancellous bone (p = 0.063). The use of alcohol did not change the bioburden following H₂O₂ in cancellous and cortical bone. Despite the important drop of bacterial load, H₂O₂ was not enough to completely eradicate bacterial with this model of bioburden. H₂O₂ is useful in decontamination, but antibiotics have little activity, and alcohol is useless. The process is useful in decontamination up to 3 logs of bioburden.

Preclinical models of vertebral osteomyelitis and associated infections: Current models and recommendations for study design

Spine-related infections, such as vertebral osteomyelitis, discitis, or spondylitis, are rare diseases that mostly affect adults, and are usually of hematogenous origin. The incidence of this condition has gradually risen in recent years because of increases in spine-related surgery and hospital-acquired infections, an aging population, and intravenous (IV) drug use. Spine infections are most commonly caused by Staphylococcus aureus, while other systemic infections such as tuberculosis and brucellosis can also cause spondylitis. Various animal models of vertebral osteomyelitis and associated infections have been investigated in mouse, rat, chicken, rabbit, dog, and sheep models by hematogenous and direct inoculation in surgery, each with their strengths and limitations. This review is the first of its kind to concisely analyze the various existing animal models used to reproduce clinically relevant models of infection. Spine-related infection models must address the unique anatomy of the spine, the avascular nature of its structures and tissues and the consequences of tissue destruction such as spinal cord compression. Further investigation is necessary to elucidate the specific mechanisms of host-microbe response to inform antimicrobial therapy and administration techniques in a technically demanding body cavity. Small-animal models are not suitable for large instrumentation, and difficult IV access thwarts antibiotic administration. In contrast, large-animal models can be implanted with clinically relevant instrumentation and are resilient to repeat procedures to study postoperative infection. A canine model of infection offers a unique opportunity to design and investigate antimicrobial treatments through recruitment a rich population of canine patients, presenting with a natural disease that is suitable for randomized trials.

The inhibitory effects of vancomycin on rat bone marrow-derived mesenchymal stem cell differentiation

OBJECTIVE

The use of intrawound vancomycin powder in spine surgery has been shown to decrease the rate of surgical site infections; however, the optimal dose is unknown. High-dose vancomycin inhibits osteoblast proliferation in vitro and may decrease the rate of solid arthrodesis. Bone marrow-derived mesenchymal stem cells (BMSCs) are multipotent cells that are a source of osteogenesis in spine fusions. The purpose of this study was to determine the effects of vancomycin on rat BMSC viability and differentiation in vitro.

METHODS

BMSCs were isolated from the femurs of immature female rats, cultured, and then split into two equal groups; half were treated to stimulate osteoblastic differentiation and half were not. Osteogenesis was stimulated by the addition of 50 µg/mL l-ascorbic acid, 10 mM β-glycerol phosphate, and 0.1 µM dexamethasone. Vancomycin was added to cell culture medium at concentrations of 0, 0.04, 0.4, or 4 mg/mL. Early differentiation was determined by alkaline phosphatase activity (4 days posttreatment) and late differentiation by alizarin red staining for mineralization (9 days posttreatment). Cell viability was determined at both the early and late time points by measurement of formazan colorimetric product.

RESULTS

Viability within the first 4 days decreased with high-dose vancomycin treatment, with cells receiving 4 mg/mL vancomycin having 40%-60% viability compared to the control. A gradual decrease in alizarin red staining and nodule formation was observed with increasing vancomycin doses. In the presence of the osteogenic factors, vancomycin did not have deleterious effects on alkaline phosphatase activity, whereas a trend toward reduced activity was seen in the absence of osteogenic factors when compared to osteogenically treated cells.

CONCLUSIONS

Vancomycin reduced BMSC viability and impaired late osteogenic differentiation with high-dose treatment. Therefore, the inhibitory effects of high-dose vancomycin on spinal fusion may result from both reduced BMSC viability and some impairment of osteogenic differentiation.

Single level posterolateral lumbar fusion in a New Zealand White rabbit (Oryctolagus cuniculus) model: Surgical anatomy, operative technique, autograft fusion rates, and perioperative care

INTRODUCTION

The posterolateral lumbar fusion (PLF) New Zealand White (NZW) (Oryctolagus cuniculus) rabbit model is a long-standing surgical technique for the preclinical evaluation of materials for spinal fusion. A detailed understanding of lumbar spine anatomy and perioperative care requirements of rabbits is imperative for correct execution of the model both scientifically and ethically. This study describes the preoperative procedures and surgical techniques used in single level PLF in a NZW rabbit model as it pertains to the animal husbandry, lumbar spine anatomy, anesthesia, surgical approach, and perioperative care of rabbits in a research setting.

MATERIALS AND METHODS

We describe the surgical technique and perioperative patient care for single level PLF in a NZW rabbit model. Medical records from a single research facility were retrospectively reviewed for adult NZW rabbits that underwent single level PLF (L4-L5) between January 2016 and December 2019. The number of lumbar vertebrae per rabbit, fusion rates at 12 weeks using iliac crest autograft and complications are reported. Skeletal maturity was confirmed by preoperative fluoroscopic and radiographic documented closure of hindlimb physes.

RESULTS

The PLF rabbit surgical model and perioperative patient care is described. PLF was performed in 868 adult female entire NZW rabbits. The majority of rabbits had seven lumbar vertebrae (620/868; 71.4%), followed by six (221/868; 25.5%), and eight (27/868; 3.1%). Fusion rates at 12 weeks for PLF using iliac crest autograft as assessed by manual palpation and radiographic assessment was 76.9% and 70.0%, respectively. Postoperative complications included occasional partial autograft site wound dehiscence due to self-trauma.

CONCLUSIONS

For PLF rabbit models, a detailed understanding of the surgical technique, rabbit lumbar anatomy including number of lumbar vertebrae, and dietary and husbandry requirements of rabbits, is essential for execution of the model and animal welfare.

Demineralized bone matrix paste formulated with biomimetic PLGA microcarriers for the vancomycin hydrochloride controlled delivery: Release profile, citotoxicity and efficacy against S. aureus

Infection and resulting bone defects caused by Staphylococcus aureus is one of the major issues in orthopaedic surgeries. Vancomycin hydrochloride (VaH) is largely used to manage these events. Here, a human derived bone paste supplemented with biopolymer microcarriers for VaH sustained delivery to merge osteoinductive and antimicrobial actions is described. In detail, different emulsion formulations were tested to fabricate micro-carriers of poly-lactic-co-glycolic acid (PLGA) and hydroxyapatite (HA) by a proprietary technology (named Supercritical Emulsion Extraction). These carriers (mean size 827 ± 68 μm; loading 47 mg_VaH/g_PLGA) were assembled with human demineralized bone matrix (DBM) to obtain an antimicrobial bone paste system (250 mg/0.5 cm³ w/v, carrier/DBM). Release profiles in PBS indicated a daily drug average release of about 4 µg/mL over two weeks. This concentration was close to the minimum inhibitory concentration and able to effectively inhibit the S. aureus growth in our experimental sets. Carriers cytotoxicity tests showed absence of adverse effects on cell viability at the concentrations used for paste assembly. This approach points toward the potential of the DBM-carrier-antibiotic system in hampering the bacterial growth with accurately controlled antibiotic release and opens perspectives on functional bone paste with PLGA carriers for the controlled release of bioactive molecules.

Spinal Fusion Surgery and Local Antibiotic Administration: A Systematic Review on Key Points From Preclinical and Clinical Data

STUDY DESIGN

Systematic review.

OBJECTIVE

The present review of clinical and preclinical in vivo studies focused on the local antibiotic administration for surgical site infection (SSI) in spinal fusion procedures and identifying new approaches or research direction able to release antibiotics in the infected environment.

SUMMARY OF BACKGROUND DATA

SSI is a severe complication of spinal fusion procedures that represents a challenging issue for orthopedic surgeons. SSIs can range from 0.7% to 2.3% without instrumentation up to 6.7% with the use of instrumentation with significant implications in health care costs and patient management.

METHOD

A systematic search was carried out by two independent researchers according to the PRISMA statement in three databases (www.pubmed.com, www.scopus.com and www.webofknowledge.com) to identify preclinical in vivo and clinical reports in the last 10 years. Additionally, to evaluate ongoing clinical trials, three of the major clinical registry websites were also checked (www.clinicaltrials.gov, www.who.int/ictrp, https://www.clinicaltrialsregister.eu).

RESULTS

After screening, a total of 43 articles were considered eligible for the review: 36 clinical studies and seven preclinical studies. In addition, six clinical trials were selected from the clinical registry websites.

CONCLUSION

The results reported that the topical vancomycin application seem to represent a strategy to reduce SSI incidence in spine surgery. However, the use of local vancomycin as a preventive approach for SSIs in spine surgery is mostly based on retrospective studies with low levels of evidence and moderate/severe risk of bias that do not allow to draw a clear conclusion. This review also underlines that several key points concerning the local use of antibiotics in spinal fusion still remains to be defined to allow this field to make a leap forward that would lead to the identification of specific approaches to counteract the onset of SSIs.

LEVEL OF EVIDENCE

4.

A Three-Dimensional Printed Polycaprolactone Scaffold Combined with Co-Axially Electrospun Vancomycin/Ceftazidime/Bone Morphological Protein-2 Sheath-Core Nanofibers for the Repair of Segmental Bone Defects During the Masquelet Procedure

Introduction

Masquelet proposed a new solution for the healing of segmental bone defects, thus minimizing the disadvantages associated with traditional bone grafting. However, a major factor leading to the failure of this technique pertains to be the residual infection. Accordingly, we developed an antibiotic- and osteo-inductive agent-loaded composite scaffold to solve this problem.

Methods

A mesh-like polycaprolactone scaffold was prepared using a lab-exploited solution-type three-dimensional printer, and hybrid sheath-core structured poly(lactic-co-glycolic-acid) nanofibers were fabricated using co-axial electrospinning technology. Vancomycin, ceftazidime, and bone morphological protein (BMP)-2 were employed. The in vitro and in vivo (rabbit fracture model) release patterns of applied agents from the composite scaffold were investigated.

Results

The results revealed that the drug-eluting composite scaffold enabled the sustainable release of the medications for at least 30 days in vitro. Animal tests demonstrated that a high concentration of medications was maintained. Abundant growth factors were induced within the bioactive membrane stimulated by the applied scaffold. Finally, satisfactory bone healing potential was observed on radiological examination and biomechanical evaluation.

Discussion

The developed composite scaffold may facilitate bone healing by inducing bioactive membrane formation and yielding high concentrations of antibiotics and BMP-2 during the Masquelet procedure.

Evidence-Based Recommendations for Local Antimicrobial Strategies and Dead Space Management in Fracture-Related Infection

Fracture-related infection (FRI) remains a challenging complication that imposes a heavy burden on orthopaedic trauma patients. The surgical management eradicates the local infectious focus and if necessary facilitates bone healing. Treatment success is associated with debridement of all dead and poorly vascularized tissue. However, debridement is often associated with the formation of a dead space, which provides an ideal environment for bacteria and is a potential site for recurrent infection. Dead space management is therefore of critical importance. For this reason, the use of locally delivered antimicrobials has gained attention not only for local antimicrobial activity but also for dead space management. Local antimicrobial therapy has been widely studied in periprosthetic joint infection, without addressing the specific problems of FRI. Furthermore, the literature presents a wide array of methods and guidelines with respect to the use of local antimicrobials. The present review describes the scientific evidence related to dead space management with a focus on the currently available local antimicrobial strategies in the management of FRI. LEVEL OF EVIDENCE:: Therapeutic Level V. See Instructions for Authors for a complete description of levels of evidence.

Which type of bone releases the most vancomycin? Comparison of spongious bone, cortical powder and cortico-spongious bone

Bone infections can be challenging to treat and can lead to several surgeries and relapses. When a graft is needed, cavitary bone loss can be grafted with cancellous or cortical bone. Both can be used for grafting. However, the antibiotic releasing capacity of these grafts has not been compared. Which type of bone is best at releasing the most antibiotic has not been well established. The aim of this study was to determine which type of bone is best for antibiotic release when the bone is suffused with antibiotics by the surgeon. The hypothesis is that there would be a difference between the type of bone tested due to different release capacities of cortical and cancellous bone. This was an experimental study. Cortical spongy bone in chips, Spongy bone in chips and demineralized cortical bone powder were compared. For each type of bone, 5 samples were tested. Processed and decontaminated grafts were freeze-dried to be kept at room temperature. The primary endpoint was the amount of vancomycin released by the graft as it affects the concentration of antibiotic around the graft in clinical practice. The procedure for the study consisted of full graft immersion in a vancomycin solution. Then, the liquid was removed with aspiration. In order to measure the quantity of antibiotic released, the bone was put into distilled water in agitation in a heated rocker at 37 °C. After 30 min of soaking, 1 mL of the liquid was removed. The same extraction process was also carried out after 60 min soaking, 2 h, 3 h, 24 h, and 48 h. No differences were found between each type of bone relative to the concentration of vancomycin released at each time of the assessment. There was a significant difference in the weight of the bone with a higher weight for the cortical powder (1.793 g) versus cortical spongy bone and spongy bone (1.154 g and 1.013 g) with a p value < 0.0001. A significant difference was seen in the weight of the bone with vancomycin after the aspiration of the liquid with 3.026 g for cortical powder, 2.140 g and 2.049 g for the cortical spongy bone and the spongy bone with a p value < 0.0001. In daily clinical practice, one can use cancellous bone, cortico-cancellous bone or cortical powder in order to add vancomycin to a bone graft. Our results show the release kinetics of the soaked allografts. With a maximum of 14 mg/mL in the first minutes and a rapid decrease it shows a pattern comparable to antibiotic loaded bone cement. The method used appears favourable for prophylactic use, protecting the graft against contamination at implantation, but is not sufficient for treating chronic bone infection. LEVEL OF EVIDENCE: V.

Impact of Gentamicin-Loaded Bone Graft on Defect Healing in a Sheep Model

Infections of bone are severe complications, and an optimization of grafting material with antimicrobial drugs might be useful for prevention and treatment. This study aimed to investigate the influence of gentamicin-loaded bone graft on the healing of bone defects in a sheep model. Metaphyseal and diaphyseal drill hole defects (diameter: 6 mm, depth: 15 mm) were filled with graft or gentamicin-loaded graft (50 mg/g graft) or were left untreated. Analysis of regeneration after three and nine weeks, micro-computed tomography (μCT), and histology revealed a significant increase in bone formation in the drill hole defects, which began at the edges of the holes and grew over time into the defect center. The amount of graft decreased over time due to active resorption by osteoclasts, while osteoblasts formed new bone. No difference between the groups was seen after three weeks. After nine weeks, significantly less mineralized tissue was formed in the gentamicin-loaded graft group. Signs of inflammatory reactions were seen in all three groups. Even though the applied gentamicin concentration was based on the concentration of gentamicin mixed with cement, the healing process was impaired. When using local gentamicin, a dose-dependent, compromising effect on bone healing should be considered.

Reduction in surgical site infection with suprafascial intrawound application of vancomycin powder in instrumented posterior spinal fusion: a retrospective case-control study

OBJECTIVE Recent studies have demonstrated the efficacy of subfascial intrawound application of vancomycin powder in spine surgery in reducing the rate of surgical site infections (SSIs). However, to date no study has evaluated the efficacy and safety of suprafascial application of vancomycin powder in spine surgery. The purpose of this study was to quantify the rate of SSIs after open instrumented posterior spinal fusion with and without application of suprafascial vancomycin powder and to evaluate the rate of vancomycin powder-related local adverse effects. METHODS The authors conducted a single-center retrospective case-control study of adult patients undergoing open instrumented posterior fusion of the cervical, thoracic, or lumbar spine performed by a single surgeon from January 2010 through December 2016. In March 2013, routine application of 1 g of suprafascial vancomycin powder was started for all cases in addition to standard systemic antibiotic prophylaxis. Baseline demographics and operative data as well as the SSI rates were compared between the study groups. The incidence of vancomycin powder-related adverse effects was analyzed. RESULTS A total of 515 patients (268 in the untreated group and 247 in the treated group) were included in the study. The mean age was significantly higher in the treated group than in the untreated group (58.4 vs 54.4 years, p < 0.01). Operative variables were similar between the study groups. Patients receiving vancomycin powder had a significantly lower infection rate (5.6% in the untreated group vs 0% in the treated group, p < 0.001). No vancomycin powder-related adverse effects were identified in the treated group. CONCLUSIONS Routine application of suprafascial intrawound vancomycin powder in addition to systemic antibiotic prophylaxis is an easy-to-use, safe, and effective strategy for preventing SSIs after instrumented posterior spinal fusion. Suprafascial application of vancomycin powder could be a valuable alternative to previously reported subfascial distribution, minimizing the risk of local adverse drug reactions.