Surgical site infections following instrumented stabilization of the spine

In Vitro Bacterial Growth on Titanium Surfaces Treated with Nanosized Hydroxyapatite

Bacterial growth on implant surfaces poses a significant obstacle to the long-term success of dental and orthopedic implants. There is a need for implants that promote osseointegration while at the same time decreasing or preventing bacterial growth. In this study, the existing methods for the measurement of bacterial biofilms were adapted so that they were suitable for measuring the bacterial growth on implant surfaces. Two different strains of bacteria, Pseudomonas aeruginosa and Staphylococcus epidermidis, were used, and the in vitro effect of bacterial growth on titanium surfaces coated with an ultrathin (20-40 nm thick) layer of nanosized hydroxyapatite (nHA) was investigated. After 2 h of biofilm growth, there was a 33% reduction in both S. epidermidis and P. aeruginosa bacteria on nHA compared to Ti. For a more mature 24 h biofilm, there was a 46% reduction in S. epidermidis and a 43% reduction in P. aeruginosa on nHA compared to Ti. This shows that coating nHA onto implants could be of benefit in reducing implant-related infections.

Unexpected positive culture (UPC) in adults revision spine surgery: a systematic review and meta-analysis of incidence, risk factors, and management

BACKGROUND

Without clear signs of infection, spinal implant failure is attributed to mechanical overloads and aseptic loosening. However, how low-grade infections contribute to seemingly aseptic implant failure is unclear.

PURPOSE

The systematic review examined unexpected positive cultures (UPCs) in revision spine surgery regarding prevalence, isolated pathogens, risk factors, and strategies to reduce infection among asymptomatic patients undergoing revision spine surgery.

METHODS

We followed the PRISMA guidelines and searched four main databases (PubMed, EMBASE, SCOPUS, Web of Science) comprehensively until January 2023 for articles reporting UPC after presumed aseptic adult revision spine surgery. The UPC rates were pooled, and risk factors were compared with the culture-negative control group and represented as odds ratio (OR) or mean difference (MD).

RESULTS

Fifteen studies of 1057 individuals were included in two groups: culture-positive or UPCs (n = 317) and culture-negative or control (n = 740). The overall UPC prevalence was 33.2% (317/1057, range: 0 to 53%, 95% CI = 30.2%-36.4%), and Cutibacterium acnes (43.0%, 95% CI = 37.4%-48.8%), Coagulase-negative Staphylococci (CoNS), (39.5%, 95% CI = 33.2%-46.2%), and Staphylococcus species in general (49.5%, 95%CI = 43.7%-55.4%) were reported the most common isolated microbes. 16.1% of the UPCs were polymicrobial. Risk factors associated with UPC rates were female sex (OR = 2.62, 95%CI = 1.76-3.90, P < 0.001), screw loosening (OR = 4.43, 95%CI = 1.31-15.02, P = 0.02), number of operated levels (MD = 0.77, 95%CI = 0.33-1.22, P = 0.0007), and shorter time since index surgery (MD = - 8.57 months, 95%CI = - 14.76, -2.39, P = 0.02).

CONCLUSIONS

One-third of patients undergoing spine revision surgery revealed UPC in this study. Each UPC pathogen interpretation and antibiotic use decision should be interpreted case by case.

LEVEL OF EVIDENCE

IV.

A novel rodent model of chronic spinal implant-associated infection

BACKGROUND CONTEXT

Bacterial infection of spinal instrumentation is a significant challenge in spinal fusion surgery. Although the intraoperative local application of powdered vancomycin is common practice for mitigating infection, the antimicrobial effects of this route of administration are short-lived. Therefore, novel antibiotic-loaded bone grafts as well as a reliable animal model to permit the testing of such therapies are needed to improve the efficacy of infection reduction practices in spinal fusion surgery.

PURPOSE

This study aims to establish a clinically relevant rat model of spinal implant-associated infection to permit the evaluation of antimicrobial bone graft materials used in spinal fusion.

STUDY DESIGN

Rodent study of chronic spinal implant-associated infection.

METHODS

Instrumentation anchored in and spanning the vertebral bodies of L4 and L5 was inoculated with bioluminescent methicillin-resistant Staphylococcus aureus bacteria (MRSA). Infection was monitored using an in vivo imaging system (IVIS) for 8 weeks. Spines were harvested and evaluated histologically, and colony-forming units (CFUs) were quantified in harvested implants and spinal tissue.

RESULTS

Postsurgical analysis of bacterial infection in vivo demonstrated stratification between MRSA and phosphate-buffered saline (PBS) control groups during the first 4 weeks of the 8-week infection period, indicating the successful establishment of acute infection. Over the 8-week chronic infection period, groups inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU demonstrated significantly higher bioluminescence than groups inoculated with PBS control (p = 0.009 and p = 0.041 respectively). Histological examination at 8 weeks postimplantation revealed the presence of abscesses localized to implant placement in all MRSA inoculation groups, with the most pervasive abscess formation in samples inoculated with 1 × 105 MRSA CFU and 1 × 106 MRSA CFU. Quantification of CFU plated from harvested spinal tissue at 8 weeks post-implantation revealed the 1 × 105 MRSA CFU inoculation group as the only group with a significantly greater average CFU count compared to PBS control (p = 0.017). Further, CFU quantification from harvested spinal tissue was greater than CFU quantification from harvested implants across all inoculation groups.

CONCLUSION

Our model demonstrated that the inoculation dosage of 1 × 105 MRSA CFU exhibited the most robust chronic infection within instrumented vertebral bodies. This dosage had the greatest difference in bioluminescence signal from control (p < 0.01), the lowest mortality (0% compared to 50% for samples inoculated with 1 × 106 MRSA CFU), and a significantly higher amount of CFUs from harvested spine samples than CFUs from control harvested spine samples. Further, histological analysis confirmed the reliability of this novel rodent model of implanted-associated infection to establish infection and biofilm formation of MRSA for all inoculation groups.

CLINICAL SIGNIFICANCE

This model is intended to simulate the infection of instrumentation used in spinal fusion surgeries concerning implant locality and material. This model may evaluate potential antimicrobial and osteogenic biomaterials and investigate the relationship between implant-associated infection and failed fusion.

Surgical Site Infections after Spinal Surgery in a Tropical Area: A Prospective Monocentric Observational Study

To date, no study has described the microbiological profile of surgical site infections (SSIs) after spine surgery in a tropical environment. The main objective of this study is to describe the microbiology and the risk factors of SSI after spinal surgery in a tropical climate. Our hypothesis is that the microbiology of SSIs in tropical areas is different to what is mainly described in temperate countries. As a consequence, the recommendation for antibiotic prophylaxis administered in the operative room, which mainly relays on the literature, might not be adequate in such countries. We included 323 consecutive patients who underwent a spinal intervention between 2017 and 2019, with a 2-year minimum follow-up. Objective ISO criteria were established in accordance with the criteria accepted by the Center of Disease Control in Atlanta. The identification of risk factors for SSI was carried out by uni- and multivariate analysis with a significance threshold of P < 0.05. The incidence of SSI was 7.7%. A total of 54.8% were in favor of a predominantly digestive origin of germs with an average of 1.68 bacteria found by ISO. Inadequate antibiotic prophylaxis was found in 54.8%. Age and body mass index were found to be independent risk factors for SSI. We report here an unusual microbiological profile of SSI with a predominance of gram-negative bacteria and a low proportion of Staphylococcus aureus and Staphylococcus epidermidis.

Management and outcome of spinal implant-associated surgical site infections in patients with posterior instrumentation: analysis of 176 cases

PURPOSE

The management of implant-associated surgical site infections (SSI) in patients with posterior instrumentation is challenging. Evidence regarding the most appropriate treatment and the need for removal of implants is equivocal. We sought to evaluate the management and outcome of such patients at our institution.

METHODS

We searched our prospectively documented databases for eligible patients with posterior spinal instrumentation, excluding the cervical spine (January 2008-June 2018). Patient files were reviewed, demographic data and treatment details were recorded. Patient-reported outcome (PRO) was assessed with the Core Outcome Measures Index (COMI) preoperatively and postoperatively at 3 and 12 months.

RESULTS

A total of 170 patients underwent 210 revisions for 176 SSIs. Two-thirds presented within four weeks (105/176, 59.7%, median 22.5d, 7d-11.1y). The most common pathogens were Staphylococcus aureus (n = 79/210, 37.6%) and Staphylococcus epidermidis (n = 56/210, 26.7%). Debridement and implant retention was performed in 135/210 (64.3%) revisions and partial replacement in 62/210 (29.5%). In 28/176 SSI (15.9%), persistent infection required multiple revisions (≤ 4). Surgery was followed by intravenous and oral antimicrobial treatment (10-12w). In 139/176 SSIs (79%) with ≥ 1y follow-up, infection was cured in 115/139 (82.7%); relapse occurred in 9 (relapse rate: 5.1%). Two patients (1.4%) died. COMI decreased significantly (8.2 ± 1.5 vs. 4.8 ± 2.9, p < 0.0001) over 12 months. 72.7% of patients were (very) satisfied with their care.

CONCLUSION

Patients with SSI after posterior (thoraco-)lumbo(-sacral) instrumentation can be successfully treated in most cases with surgical and specific antibiotic treatment. An interdisciplinary approach is recommended. Loose implants should be replaced. In some cases, multiple revisions may be necessary. Patient outcomes were satisfactory.

A rat model of polymicrobial infection in full-thickness excision wounds

AIM

A reproducible animal model is required to study the pathophysiology of wound infections and for development of effective therapeutic interventions. The objective of this study was to produce an infected skin wound model utilizing the cecal microbiota in non-immunocompromised rats.

MATERIALS AND METHODS

An excision wound was created on the dorsal surface of rats and inoculated with different concentration of cecal slurry (CS). Wound progression was investigated macroscopically by wound scoring and imaging. The rats were sacrificed on day 6 and microbial load, myeloperoxidase activity, histopathology, and scanning electron microscopy (SEM) were performed in wound tissue.

RESULTS

Inoculation of CS into excision wounds caused significantly (p < 0.05) delayed wound healing in comparison to non-infected wounds as revealed by slow wound closure (9.1 to 12.83%). A significant (p < 0.05) difference in wound score was observed between the infected and non-infected wounds. A significantly (p < 0.05) high microbial load (~10 ⁹ CFU/gm) was observed in infected wound which was supported by the presence of intensive bacterial colonization with sparse development of amorphous material on wound tissue during SEM analysis. A maximum increase of 1.76-fold in myeloperoxidase activity was observed in the infected wounds in comparison to non-infected wounds. Histopathology revealed increased amount of cellular infiltration, hematoma formation, and presence of bacterial aggregates in deep tissues.

CONCLUSION

The study reports a reproducible and relevant clinical model of wound infection where cecal microbiota was used as a source of infection. This model can provide a suitable platform for evaluation of new therapeutic interventions.

Low-Grade Infection and Implant Failure Following Spinal Instrumentation: A Prospective Comparative Study

BACKGROUND

Spinal instrumentation can be associated with complications, including implant loosening. Hitherto, implant loosening has mainly been attributed to mechanical overload.

OBJECTIVE

To examine the role of low-grade infections as the cause of implant failure in suspected aseptic implant loosening following spinal instrumentation.

METHODS

A prospective single center observational study was performed. All patients who had revision surgery following spinal instrumentation between August 2015 and February 2018 were screened. Patients with revision surgery due to screw loosening on the computed tomograhy scan constituted the study group. Patients in which the screws where not loosened but removal was performed for other reasons formed the comparison group. Intraoperative swabs were taken and sonication was performed with the explanted material. Results of microbiological cultivation were analyzed.

RESULTS

A total of 59 patients were included in the study group and 34 in the comparison group. In the study group in 42.4% of the cultures a bacterium was detected, while in the comparison group only in 17.6%. 84%, and 83.3% of these germs were detected by sonication in the study and comparison group, respectively. The rate of positive cultures was significantly higher in the study group compared to the comparison group (P = .001). The most frequent bacterium cultivated in both groups was Propionibacterium acnes, followed by Staphylococcus species.

CONCLUSION

For patients with screw loosening a high level of suspicion for a low-grade infection should be raised. Cultures should be performed from the sonication fluid of the explanted devices in all patients with symptomatic screw loosening.

Deep Surgical-Site Infection Following Thoracolumbar Instrumented Spinal Surgery: The Experience of 25 Years

BACKGROUND

Deep surgical-site infection following thoracolumbar instrumented spinal surgery (DSITIS) is a major complication in spine surgery and its impact on long-term morbidity and mortality is yet to be determined. This article describes the characteristics and evolution of DSITIS in our center over a period of 25 years.

METHODS

This single-center, retrospective cohort study included patients diagnosed with DSITIS between January 1992 and December 2016 and with a minimum follow-up after infection diagnosis of 1 year. The Infectious Diseases Society of America criteria and/or Centers for Disease Control and Prevention criteria were used to define DSITIS. Patient data (epidemiological and health status), surgical data, infection characteristics and presentation, isolated microorganisms, required surgical debridements, implant removal, and major complications linked to infection were evaluated.

RESULTS

A total of 174 patients (106 females) were included in the analysis. Mean follow-up after infection diagnosis was 40 months (56 patients with over 5 years follow-up). Adolescent idiopathic scoliosis, adult deformity, and degenerative lumbar stenosis were the most frequent etiologies for primary surgery. Presentation of infection was considered early (0-3 months since first surgery) in 59.2% of the cases, delayed (3-24 months) in 11.5%, and late (more than 24 months) in 29.3%. All patients were treated by surgical debridement. More than 1 surgical debridement was necessary in 20.7% of cases. Implants were removed in 46.6% of the patients (72.83% in the first surgical debridement). Most frequently isolated microorganisms were Staphylococcus spp, Enterobacteriaceae, and Cutibacterium acnes. Major complications appeared in 14.3% of the patients, and over 80% of them required major surgeries to resolve those complications.

CONCLUSIONS

Late DSITIS is more frequent than previously reported. In DSITIS culprits, Staphylococcus spp, Enterobacteriaceae, and Cutibacterium acnes predominate. DSITIS produce a high rate of major complications that usually require major surgery for treatment.

LEVEL OF EVIDENCE

3.

Investigation of Risk Factors for Pain Chronification in Patients Suffering from Infections of the Spine

Background: Spinal infections represent a therapeutic challenge. The often protracted course of the disease is accompanied by pain, which can lead to a chronic pain experience even after the infectious disease has been treated successfully. The aim of this study was to investigate possible risk factors of pain chronification. Methods: In a prospective study, 14 patients with spinal infections were examined at admission (T1), at discharge from inpatient therapy (T2), and three to eight months postoperatively (T3) byquestionnaires on risk factors for pain chronification and by quantitative sensory testing (QST). Results: In-patient treatment lasted on average 45.3 days (±33.13). The patients complained of pain for 3.43 months (±2.77) prior to inpatient treatment. The visual analogue scale (VAS) for pain (0–10) and the Oswestry Disability Index detected significant improvement in the course of the study. However, patients also reported catastrophic thinking, as well as fear of movement and (re)-injury. Conclusion: In summary, our results demonstrate that patients with spinal infections did not suffer from pain chronification, but might benefit from an interdisciplinary therapeutic approach, which emphasizes promoting active pain-coping strategies, as well as addressing fear of movement and catastrophic thinking.

Clinical presentation and diagnosis of acute postoperative spinal implant infection (PSII)

Acute postoperative infections after surgical interventions on the spinal column are associated with prolonged treatment duration, poor patient outcomes, and a high socioeconomic burden. In the field of joint replacement, guidelines have been established with recommendations for the diagnosis and treatment of such complications, but in spinal surgery there are no definitions permitting distinction between early and late infections and no specific instructions for their management. Various factors increase the risk of acute postoperative infection, including blood transfusions, leakage of cerebrospinal fluid, urinary tract infection, injury of the dura mater, an American Society of Anesthesiologists (ASA) score >2, obesity, diabetes mellitus, and surgical revision. We suggest defining all infections occurring within the first 4 weeks after spinal surgery as early infections. The symptoms are pain at rest, on motion, and/or pressure pain, abnormal warmth, local erythema, circumscribed swelling of the wound, and newly occurring secretion. Together with laboratory parameters such as C-reactive protein (CRP) and leukocytes, a central role is played by imaging in the form of magnetic resonance imaging (MRI), although diagnosis can be hampered by the presence of postoperative fluid collections such as edema or hematoma or by artifacts from an implant. Once an infection has been confirmed, immediate wound revision with debridement and rinsing (sodium hypochlorite) is essential. Intraoperatively it may prove advantageous to use jet lavage and administer vancomycin. We recommend leaving the implant in place in cases of acute postoperative infection. Patients who are not conditional for surgery can first receive antibiotic suppression treatment before surgery at a later date. In such cases initial computed tomography (CT)-guided aspiration or drain insertion can take place.

Reducing Surgical Site Infection in Pediatric Scoliosis Surgery: A Multidisciplinary Improvement Program and Prospective 4-Year Audit

STUDY DESIGN

Single-center prospective cohort.

OBJECTIVES

To evaluate a multidisciplinary led, structured protocol for reducing surgical site infections (SSIs) in pediatric scoliosis surgery.

METHODS

Following a spike to 8.6% in local annual infection rate, a multidisciplinary team was convened to identify interventions. The team consisted of spinal surgeons, infectious diseases consultants, physiotherapists, specialist nurses, and theatre managers. A protocol was initiated, including preoperative skin decontamination; standardized operative site prepreparation; betadine-soaked swabs sutured to wound edges; blood loss minimization; 3 L0.9% saline pulsed-lavage; defined protocol of glove changes; antibiotic regime of preoperative gentamicin, intraoperative subfascial vancomycin powder, 48-hour cefuroxime; and intraoperative normothermia. A 4-year audit was initiated of all patients aged ≤18 years undergoing corrective spinal deformity surgery. Institutional board review was not required.

RESULTS

Between January 1, 2014 and January 1, 2018, 414 operations were performed on 355 patients: male:female = 1:2.2, mean age 13.7 years (range 2.5-17.9), 233 idiopathic (mean operated vertebral levels 12), 122 neuromuscular (mean operated vertebral levels 14), 66 growing rod procedures, 41 multistage procedures. The mean number of operated vertebral levels both overall and in infected cases was 13 (range 2-17). Nine SSIs occurred in 8 patients at 3 months (4 neuromuscular), resulting in an overall SSI per operation of 2.2%.

CONCLUSION

A multidisciplinary approach with standardized measures significantly reduced SSIs in the unit's pediatric scoliosis surgery.

[Infections after reconstructive spinal interventions : How do I deal with them?]

BASICS

Postoperative surgical site infections of the spine have been described in up to 20% of patients and can result in serious consequences for the patient and substantial treatment costs. Typical bacteria often arise from skin or fecal flora. Various risk factors for infection have been described, including obesity, diabetes, high ASA scores, as well as intraoperative factors such as heavy blood loss, dural tears, or several revision procedures. Consequently, the prophylaxis with pre- and postoperative risk minimization is of particular importance.

TREATMENT

When an infection has developed, it is important to carry out early operative revision involving tissue debridement, lavage and acquiring microbiological samples for culture. If the infection presents early, the instrumentation can often be retained. Adjuvant measures such as negative pressure wound treatment may improve the outcome. In late-onset infections, due to the biofilm production on the instrument surface or in cases of implant loosening, one should attempt to remove the instrumentation, and in cases of instability replace it. This article deals with the current literature on the subject and provides an overview of the data with regard to peri- and postoperative infections.

Changes of Biomarkers before and after Antibiotic Treatment in Spinal Infection

Objective

The laboratory biomarkers used to diagnose spinal infection include white blood cell (WBC) counts, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Recently, procalcitonin (PCT) has been used as a biomarker to distinguish between bacterial infection and non-bacterial infection. We aimed to compare the changes of conventional biomarker and PCT in patients with spinal infection before and after antibiotic treatment.

Methods

ESR, CRP, WBC counts, and PCT were measured in 29 patients diagnosed with pyogenic spinal infection at our hospital between May 2016 and December 2018 prior to antibiotic administration. After antibiotic administration, the values were followed up for 4 weeks at 1-week intervals.

Results

A total of 29 patients were enrolled, with a mean age of 67.8 years, consisting of 16 men and 13 women. Twenty-five patients had lumbar infections, and 2 each had cervical and thoracic infections. The mean ESR, CRP, PCT, and WBCs decreased at week 4 of antibiotic treatment compared to their baseline values. CRP and WBCs were significantly decreased after 4 weeks of treatment compared to before treatment. The mean ESR and PCT was not statistically significant compared to pretreatment and after antibiotic treatment (p-value>0.05).

Conclusion

Among several biomarker, CRP and WBCs are biomarkers that can aid early evaluation of the effects of antibiotic treatment in pyogenic spondylitis. Although PCT did not have statistical significance, it can be used as a biomarker that reflects the effect of antibiotic and severity of infection.

Deep surgical site infection following thoracolumbar instrumented spinal surgery. Ten years of experience

OBJECTIVE

To describe the characteristics and evolution of deep surgical site infection following thoracolumbar instrumented spinal surgery (DSITIS) in our centre over a period of ten years.

MATERIAL AND METHOD

Descriptive retrospective study. Patient data (epidemiological/health status), surgical data, infection characteristics/presentation, isolated microorganisms, required surgical debridements, implant removal and major complications linked to infection were evaluated.

RESULTS

We included 110 patients (80 females). Median follow-up after infection diagnosis was 3.6years. Adolescent idiopathic scoliosis, adult deformity and degenerative lumbar stenosis were the most frequent aetiologies. Sixty-two percent of the patients had at least one clinical feature that made them prone to infection. Infection presentation was early (0-3months from first surgery) in 60.4% of the cases, delayed (3-24months) in 11.7%, and late (more than 24months) in 27%. All patients were treated by surgical debridement. Twenty-five percent needed more than one surgical debridement. Implants were removed in 46% of the patients (71% in the first surgical debridement). The most frequent isolated microorganisms were coagulasa-negative Staphylococcus, Propionibacterium acnes and Enterococcus. Major complications appeared in 15% of the patients, and 88% of them required major surgeries.

CONCLUSIONS

Late DSITIS is more frequent than previously reported. Skin microorganisms predominate among the DSITIS culprits. DSIITS produce a high rate of major complications that usually require major surgery for treatment.

Wearing long sleeves while prepping a patient in the operating room decreases airborne contaminants

BACKGROUND

The use of long sleeves by nonscrubbed personnel in the operating room has been called into question. We hypothesized that wearing long sleeves and gloves, compared with having bare arms without gloves, while applying the skin preparation solution would decrease particulate and microbial contamination.

METHODS

A mock patient skin prep was performed in 3 different operating rooms. A long-sleeved gown and gloves, or bare arms, were used to perform the procedure. Particle counters were used to assess airborne particulate contamination, and active and passive microbial assessment was achieved through air samplers and settle plate analysis. Data were compared with Student's t-test or Mann-Whitney U, and P < .05 was considered to be significant.

RESULTS

Operating room B demonstrated decreased 5.0- µm particle sizes with the use of sleeves, while operating rooms A and C showed decreased total microbes only with the use of sleeves. Despite there being no difference in the average number of total microbes for all operating rooms assessed, the use of sleeves specifically appeared to decrease the shed of Micrococcus.

CONCLUSION

The use of long sleeves and gloves while applying the skin preparation solution decreased particulate and microbial shedding in several of the operating rooms tested. Although long sleeves may not be necessary for all operating room personnel, they may decrease airborne contamination while the skin prep is applied, which may lead to decreased surgical site infections.