Does the Type of Metal Instrumentation Affect the Risk of Surgical Site Infection in Pediatric Scoliosis Surgery?

Incidental dural tears during pediatric posterior spinal fusions

PURPOSE

To characterize the frequency of incidental dural tears in pediatric spine surgery, their treatment, complications, and results of long-term follow-up.

METHODS

A retrospective review of all pediatric patients who underwent a posterior spinal fusion (PSF) between 2004-2019 at a tertiary children's hospital was conducted. Electronic medical records were reviewed for patient demographics, intra-operative data, presence of an incidental dural tear, repair method, and patient outcomes.

RESULTS

3043 PSFs were reviewed, with 99 dural tears identified in 94 patients (3.3% overall incidence). Mean follow-up was 35.7 months (range 0.1-142.5). When the cause of the dural tear was specified, 69% occurred during exposure, 5% during pedicle screw placement, 4% during osteotomy, 2% during removal of implants, and 2% during intra-thecal injection of morphine. The rate of dural tears during primary PSF was significantly lower than during revision PSF procedures (2.6% vs. 6.2%, p < 0.05). 86.9% of dural tears were repaired and/or sealed intraoperatively, while 13.1% had spontaneous resolution. Postoperative headaches developed in 13.1% of patients and resolved at a mean of 7.6 days. There was no difference in the incidence of headaches in patients that were ordered bedrest vs. no bedrest (p > 0.99). Postoperative infections occurred in 9.5% of patients and 24.1% patients were identified to have undergone a revision surgery.

CONCLUSIONS

Incidence of intra-operative dural tears in pediatric spine surgery is 3.3%. Although complications associated with the dural tear occur, most resolve over time and there were no long-term sequelae in patients with 2 years of follow up.

LEVEL OF EVIDENCE

Level IV.

Impact of implant metal type and vancomycin prophylaxis on postoperative spine infection: an in-vivo study

PURPOSE

To evaluate the effectiveness of vancomycin prophylaxis on spinal implant metal types.

METHODS

42 rabbits underwent posterior, single-level instrumentation at L5-L6 with stainless steel (n = 18), cobalt chrome (n = 12), or titanium (n = 12) wire. All implants were inoculated with 1 × 106 colony forming units (CFU) of methicillin-resistant S. Aureus (MRSA). In the intrawound vancomycin subgroup (n = 18, 6 from each metal type), 40 mg of vancomycin powder was placed in the wound. In the IV vancomycin subgroup (n = 6, all stainless steel), 15 mg/kg of IV vancomycin was given preoperatively. Local soft tissue and implants were harvested 1-week postoperatively and separately cultured.

RESULTS

Intrawound vancomycin significantly reduced the rate of soft tissue infection (44.4% vs 100%) and implant infection (27.8% vs 100%) (p < 0.001). Within the intrawound vancomycin subgroup, cobalt chrome implants were associated with higher median soft tissue MRSA growth (130 CFU) than stainless steel (0 CFU) or titanium (0 CFU) (p = 0.02). Cobalt chrome implants were also more likely to develop soft tissue MRSA infection (83.3%) as compared to stainless steel (16.7%) or titanium (33.3%) (p = 0.04). Median soft tissue MRSA growth among stainless steel implants without prophylaxis, with IV vancomycin, and with vancomycin powder was 1.18 × 107, 195, and 0 CFU, respectively. The rate of soft tissue MRSA infection without prophylaxis, with IV vancomycin, and with vancomycin powder was 100, 66.7, and 16.7%, respectively (p = 0.015).

CONCLUSION

Intrawound vancomycin is more effective than IV vancomycin and effectively reduces the risk of infection, but is less effective in cobalt chrome implants due to residual soft tissue infection.

Late spinal infections are more common after pediatric than after adult spinal deformity surgery

PURPOSE

To compare the incidence, timing, and microbiologic factors associated with late spinal infection (onset ≥ 6 months after index operation) in pediatric versus adult spinal deformity patients who underwent instrumented posterior spinal fusion (PSF).

METHODS

We retrospectively queried our institutional database for pediatric (aged ≤ 21 years) and adult patients who underwent instrumented PSF from 2000 to 2015. Inclusion criteria were > 12-month follow-up, spinal arthrodesis spanning 4 or more levels, and idiopathic or degenerative spinal deformity. We included 1260 patients (755 pediatric, 505 adult). Incidence, timing, and microbiologic and operative parameters of late spinal infections were compared using chi-squared and Fisher exact tests. Alpha = 0.05.

RESULTS

Late spinal infection occurred in 28 (3.7%) pediatric and 2 (0.39%) adult patients (p = 0.009). Mean onset of infection was 4.2 years (range 0.7-12) in pediatric patients and 4.0 years (range 0.7-7.3) in adults (p = 0.93). Pediatric patients underwent arthrodesis spanning more levels (mean ± standard deviation, 10 ± 2.0) compared with adults (8.4 ± 3.3) (p < 0.001). Adults experienced greater intraoperative blood loss (2085 ± 1491 mL) compared with pediatric patients (796 ± 452 mL) (p < 0.001). Culture samples yielded positive growth in 11 pediatric and 2 adult cases. Propionibacterium and coagulase-negative staphylococci were the most commonly detected microorganisms in both cohorts.

CONCLUSION

Late spinal infections were significantly more common in pediatric patients than in adults after instrumented PSF for spinal deformity. Skin and indolent microorganisms were the primary identifiable causative bacteria in both cohorts.

LEVEL OF EVIDENCE

III.

Surgical Site Infection Following Neuromuscular Posterior Spinal Fusion Fell 72% After Adopting the 2013 Best Practice Guidelines

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The purpose of this study is to investigate the incidence of surgical site infection in neuromuscular scoliosis (NMS) patients at a tertiary children's hospital before and after the implementation of strategies mentioned in the 2013 Best Practice Guideline.

SUMMARY OF BACKGROUND DATA

Patients with NMS are at high risk for surgical site infection following spine surgery. In 2013, a Best Practice Guideline for surgical site infection prevention in high-risk pediatric spine surgery patients reported strategies to decrease incidence. To date, no studies have looked at the efficacy of these strategies.

METHODS

A retrospective review of surgical site infection in NMS patients was performed. NMS patients undergoing primary posterior spinal fusion from January 2008 to December 2012 (Group 1) and January 2014 to December 2018 (Group 2) were included, with 2013 excluded as a transition year. The primary outcome was incidence of surgical site infection within 1 year of surgery, as defined by the Centers for Disease Control and National Healthcare Safety Network. All patients had at least 1 year of documented follow-up.

RESULTS

One hundred ninety eight patients were included, 62 in Group 1 and 136 in Group 2. Age, BMI, sex, fusion to pelvis, preoperative Cobb angle, incontinence, drain use, blood loss, surgical time, and other perioperative values were similar (P > 0.05). Deep surgical site infection occurred in 10 (16.1%) patients in Group 1 and six (4.4%) patients in Group 2 (P = 0.005). Thirteen (59.1%) identified organisms were gram-negative, with 11 (84.6%) isolated from Group 1 (P = 0.047). Polymicrobial infections accounted for six (37.5%) infections overall.

CONCLUSION

The incidence of surgical site infection in NMS patients decreased significantly (16.1% vs. 4.4%) after the implementation of the strategies mentioned in the 2013 Best Practice Guideline. Further studies are required to continue to decrease the incidence in this high-risk population.Level of Evidence: 3.

Cobalt-Chromium Alloy Has Superior Antibacterial Effect Than Titanium Alloy: In Vitro and In Vivo Studies

STUDY DESIGN

In vitro and in vivo laboratory studies.

OBJECTIVE

This study aimed to compare bacterial survival on titanium alloy (Ti) and cobalt-chromium alloy (CC) using in vitro and in vivo experiments.

SUMMARY OF BACKGROUND DATA

Spinal implants are frequently manufactured from Ti and CC. These foreign materials are thought to be susceptible to biofilm formation that contributes to the development of surgical site infections. Certain metals (i.e., silver, cobalt) are known to have antibacterial properties.

METHODS

In the in vitro study, discs made of Ti or CC were incubated with one of two common bacteria: Staphylococcus aureus (S. aureus) and Propionibacterium acnes (P. acnes). After incubation, discs were assessed to determine the number of viable bacterial cells. In the in vivo study, the discs that were made of CC or Ti were implanted into the subcutaneous layer of BALB/c mice. After skin closure, a suspension including either S. aureus or P. acnes was directly inoculated on the implanted discs. The discs were retrieved and analyzed to determine the number of viable bacteria at 0.5, 1, and 3 days after inoculation.

RESULTS

The number of viable S. aureus cultured from the CC discs was 0.9 ± 0.2 × 103 CFU/disc, which was significantly lower than the cultured Ti discs (114.8 ± 18.3 × 103 CFU/disc). Moreover, a significantly lower mean number of P. acnes were cultured with CC (1.9 ± 1.2 × 103 CFU/disc) compared with the Ti (180.0 ± 72.1 × 103 CFU/disc). The in vivo infection model testing against S. aureus or P. acnes showed a significantly lower number of viable S. aureus or P. acnes on CC discs than Ti discs. The result was seen at all measured time points.

CONCLUSION

CC suppressed S. aureus and P. acnes proliferation compared with Ti in vitro and in an in vivo infection model.Level of Evidence: N/A.

Late spinal infections following posterior spinal fusion in pediatric deformities: treatment using single-stage titanium implant exchange

PURPOSE

Late infection following posterior spinal fusion (PSF) for deformity is a leading cause of revision. The purpose of this study is to evaluate clinical and radiographic outcomes following a single-stage debridement and exchange of spinal implants with titanium in adolescent patients with late-onset infections following PSF METHODS: A retrospective review of prospectively collected data of adolescent patients with spinal deformity, who were surgically treated with PSF was collected. Patients were included for the study if they developed late arising infection (> 1 year after index posterior fusion for the deformity) from 2006-2019. Treatment consisted of irrigation, debridement, implant exchange with titanium screws and rods, and antibiotics. Parameters evaluated include radiographic Cobb angles, operative data, and clinical data, all at minimum 2-year follow-up.

RESULTS

31 patients (29 with AIS and 2 with Scheuermann's kyphosis) developed late spinal infections. Mean age was 11.4 ± 2.3 years, 84% female, mean time from index surgery was 52.5 months. 25 had all stainless steel implants and 6 had cobalt chrome during the index procedure. Positive cultures were obtained in 5 patients (2 Staphylococcus Aureus, 1 Staphylococcus epidermidis, 1 Peptostreptococcus, 1 Pseudomonas aeruginosa) with cultures followed till 7 days post-operatively. At 2-years following the exchange, there was no change in coronal and sagittal alignment. Three (9%) patients developed subsequent infection necessitating implant removal.

CONCLUSION

A single-stage procedure consisting of implant removal, irrigation, and debridement, and replacement with all titanium implants is an effective treatment strategy in patients developing late wound infection following PSF with regards to maintenance of curve correction and minimizing recurrent infections.

Is Propionibacterium acnes becoming the most common bacteria in delayed infections following adolescent idiopathic scoliosis surgery?

STUDY DESIGN

Retrospective review of hospital charts.

OBJECTIVE

(1) To determine the microbiological profile of patients with surgical site infections following posterior spinal fusion surgery (PSF) for Adolescent Idiopathic scoliosis (AIS). (2) To study the treatment outcome of patients with surgical site infections (SSI) following surgery for AIS. (3) To identify the key differences in presentation and management of acute and delayed SSI following AIS surgery. There has been increasing evidence of the role of P. acnes in deep surgical site infections. Literature related to this is abundant in relation to shoulder arthroplasty; however, it is sparse in relation to spine surgery.

METHODS

We conducted a retrospective review of all patients treated for AIS during a 5-year period (2010-2014) at our institution, with a minimum of 2-year follow-up after the index surgery. Patients with a postoperative infection following their index surgery were included. Charts of AIS patients with post-op infections were reviewed for details of the index surgery, time to presentation of the infection, presenting signs/symptoms, microbiology details, details of surgical and antibiotic treatment, and outcomes.

RESULTS

Nine (2.8%) post-op infections were identified out of 315 cases for AIS during this period. Seven (2.2%) involved P. acnes. Two (0.6%) involved MSSA. The average time for cultures to show growth was 6.1 days (range 5-8 days) in P. acnes group and 2-3 days in MSSA group. Patients with P. acnes infections were treated with implant removal, debridement and antibiotics. All patients achieved solid fusion except two patients from the P. acnes group had pseudoarthrosis and had to undergo revision fusion.

CONCLUSION

Propionibacterium acnes was the single most common bacteria isolated from delayed surgical site infection following PSF in AIS patients. Optimal treatment consists of debridement, implant removal and antibiotics. These patients have high incidence of pseudoarthrosis.

LEVEL OF EVIDENCE

Level IV.

Antibiotic prophylaxis in high-risk pediatric spine surgery: Is cefazolin enough?

STUDY DESIGN

Retrospective study.

OBJECTIVE

To describe pathogens found in SSI during pediatric-instrumented spine surgery, and to assess the relationship between pathogens and the etiology of the spinal deformity. Surgical site infection (SSI) after pediatric spine fusion is a well-known complication with incidence rates between 0.5 and 42%, associated with the patient underlying disorder. Pathogens involved in SSI seem to be related to patient characteristics, such as the etiology of the spinal deformity. GNB (gram-negative bacilli) are more frequent in neuropathic, muscular, and syndromic conditions. High-risk pediatric patients with a spine deformity undergoing instrumented surgery might benefit from receiving perioperative intravenous prophylaxis for GNB.

METHODS

We conducted a retrospective study at our tertiary-care pediatric hospital from January 2010 to January 2017. We reviewed records of all episodes of SSI that occurred in the first 12 months postoperatively. All patients who underwent instrumented spine surgery were included in this study.

RESULTS

We assessed 1410 pediatric-instrumented spine surgeries; we identified 68 patients with deep SSIs, overall rate of 4.8%. Mean age at instrumented spine surgery was 12 years and 9 months. Time elapsed between instrumented surgery and debridement surgery was 28.8 days. Cultures were positive in 48 and negative in 20. Of the 48 positive culture results, 41 (72%) were GNB, 12 (21%) gram-positive cocci (GPC), three (5%) gram-positive anaerobic cocci (GPAC), and one (2%) coagulase-negative staphylococci (CoNS). Of the 68 patients with primary SSIs, 46 were considered to have a high risk of infection, which reported GNB in 81%, GPC in 15%, GPAC in 2%, and CoNS in 2%.

CONCLUSION

Cefazolin prophylaxis covers GPC and CoNS, but GNB with unreliable effectiveness. Gram-negative pathogens are increasingly reported in SSIs in high-risk patients. Adding prophylaxis for GNB in high-risk patients should be taken into account when considering spine surgery.

LEVEL OF EVIDENCE

IV.

Analysis of growth and biofilm formation of bacterial pathogens on frequently used spinal implant materials

STUDY DESIGN

A microscopy-based investigation of the permissive factors leading towards bacterial adherence on commonly utilized spinal implants.

OBJECTIVE

The adherence and subsequent colonization and biofilm formation of bacteria on orthopaedic implants represents one of the most serious problems facing orthopaedic surgeons. Once a biofilm is formed, surgeons may have to resort to implant removal, a strategy that may cause substantial patient morbidity and lead to additional cost to the healthcare system. This problem has been further compounded by the rise of antibiotic-resistant strains of bacterial pathogens. In this study, two commonly encountered bacterial pathogens in surgical site infections (SSI) were characterized for adherence pattern, density, and propagation on five commonly used spinal implant materials via scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results show that bacterial adherence is largely dependent on the microtopographical features observed on the surface of the materials tested.

METHODS

Five commonly utilized spinal implant materials were inoculated with two of the most common nosocomial pathogens and visualized via scanning electron microscopy and confocal laser scanning microscopy.

RESULTS

Analysis of 90 spinal implant pieces showed that even though no material showed the ability to prevent adherence of both pathogens tested, the presence of surface imperfections and rougher microtopography was found to harbor the most bacterial presence.

CONCLUSION

Our data suggests that implants materials with uniform surface and minimal imperfections may reduce the ability of bacterial to adhere to implants.

LEVEL OF EVIDENCE

Level I evidence: "Investigation of a diagnostic test".

Posterior Correction Techniques for Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis represents a complex, three-dimensional deformity of the spine. Posterior spinal fusion is commonly performed in severe cases to avoid the long-term adverse sequelae associated with progressive spinal deformity. The goals of spinal fusion include halting the progression of deformity, optimizing spinal balance, and minimizing complications. Recent advances in short-segment spinal fixation have allowed for improved three-dimensional deformity correction. Preoperative planning and assessment of spinal flexibility is essential for successful deformity correction and optimization of long-term outcomes. Judicious use of releases and/or spinal osteotomies may allow for increased mobility of the spine but are associated with increased surgical time, blood loss, and risk of complications. Appreciation of implant design and material properties is critical for safe application of correction techniques. Although multiple reduction techniques have been described, no single technique is optimal for every patient.

[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.

Perioperative complications and risk factors in neuromuscular scoliosis surgery

OBJECTIVE High rates of perioperative complications are associated with deformity correction in neuromuscular scoliosis. The current study aimed to evaluate complications associated with surgical correction of neuromuscular scoliosis and to characterize potential risk factors. METHODS Data were retrospectively collected from a single-center cohort of 102 consecutive patients who underwent spinal fusions for neuromuscular scoliosis between January 2008 and December 2016 and who had a minimum of 6 months of follow-up. A subgroup analysis was performed on data from patients who had at least 2 years of follow-up. Univariate and multivariate regression analyses, as well as binary correlational models and Student t-tests, were employed for further statistical analysis. RESULTS The present cohort had 53 boys and 49 girls with a mean age at surgery of 14.0 years (± 2.7 SD, range 7.5-19.5 years). The most prevalent diagnoses were cerebral palsy (26.5%), spinal cord injury (24.5%), and neurofibromatosis (10.8%). Analysis reflected an overall perioperative complication rate of 27% (37 complications in 27 patients), 81.1% of which constituted major complications (n = 30) compared to a rate of 18.9% for minor complications (n = 7). Complications were predicted by nonambulatory status (p = 0.037), increased intraoperative blood loss (p = 0.012), increased intraoperative time (p = 0.046), greater pelvic obliquity at follow-up (p = 0.028), and greater magnitude of sagittal profile at follow-up (p = 0.048). Pulmonary comorbidity (p = 0.001), previous operations (p = 0.013), history of seizures (p = 0.046), diagnosis of myelomeningocele (p = 0.046), increase in weight postoperatively (p < 0.005), and increased lumbar lordosis at follow-up (p = 0.015) were identified as risk factors for perioperative infection. CONCLUSIONS These results suggest that in neuromuscular scoliosis, patients with preexisting pulmonary compromise and greater intraoperative blood loss have the greatest risk of experiencing a major perioperative complication following surgical deformity correction.