Key points

Introduction

Surgical site infection (SSI) after pediatric spinal deformity surgery is a complication that results in substantial morbidity and cost. The 2015 updated Centers for Disease Control and Prevention’s (CDC) guidelines defines a superficial SSI as infection involving skin or subcutaneous tissue of the incision within 30 days of surgery, whereas a deep SSI involves deeper soft tissue structures within 90 days of surgery, in association with clinical signs or symptoms of infection, purulent drainage, positive cultures, or abscess formation.

In a 2009 retrospective case series, Hedequist and colleagues found that the mean number of hospital days related to an SSI was 29 (range 6–171 days) and hospitalization cost $157,537 (range $26,877–$961,722). Prolonged courses of intravenous (IV) antibiotics and multiple surgeries for debridement, implant removal, and revision impose tremendous burden to patients, families, physicians, hospitals, and payers. The in-hospital costs pale in comparison with the personal and societal costs, including missed school, lost parental days of work, and psychological stresses to the involved patients and families.

Given the high morbidity and cost incurred with this complication, SSI after pediatric spinal surgery is a major topic of research. This review focuses on recent advancements in the identification of risk factors, prevention strategies, diagnosis, and treatment of surgical SSIs in pediatric spine patients.

Introduction

Surgical site infection (SSI) after pediatric spinal deformity surgery is a complication that results in substantial morbidity and cost. The 2015 updated Centers for Disease Control and Prevention’s (CDC) guidelines defines a superficial SSI as infection involving skin or subcutaneous tissue of the incision within 30 days of surgery, whereas a deep SSI involves deeper soft tissue structures within 90 days of surgery, in association with clinical signs or symptoms of infection, purulent drainage, positive cultures, or abscess formation.

In a 2009 retrospective case series, Hedequist and colleagues found that the mean number of hospital days related to an SSI was 29 (range 6–171 days) and hospitalization cost $157,537 (range $26,877–$961,722). Prolonged courses of intravenous (IV) antibiotics and multiple surgeries for debridement, implant removal, and revision impose tremendous burden to patients, families, physicians, hospitals, and payers. The in-hospital costs pale in comparison with the personal and societal costs, including missed school, lost parental days of work, and psychological stresses to the involved patients and families.

Given the high morbidity and cost incurred with this complication, SSI after pediatric spinal surgery is a major topic of research. This review focuses on recent advancements in the identification of risk factors, prevention strategies, diagnosis, and treatment of surgical SSIs in pediatric spine patients.

Incidence

Despite modern advances in infection-preventative strategies, the postoperative SSI incidence has remained substantial, with an overall rate of 2.2% to 8.5% in series that combine deep and superficial SSIs from all patients with scoliosis. Previous literature demonstrates that patients with neuromuscular scoliosis (NMS) are at higher risk than patients with adolescent idiopathic scoliosis (AIS) for SSI, with a 0.5% to 2.7% rate in patients with AIS versus 5.3% to 14.0% in the NMS population. A retrospective review of 20,424 pediatric patients with scoliosis in the Scoliosis Research Society database supported these trends; the overall infection rate was 2.6%, with a 5.5% rate in patients with NMS versus 1.4% in idiopathic patients.

Risk factors

In recent years, an important focus of pediatric spinal SSI research has concentrated on defining risk factors for infection in order to clarify targets for preventative strategies. Glotzbecker and colleagues performed a systematic review of risk factors for pediatric spine SSI and rated studies as grade A evidence (good), grade B (fair), or grade C (poor). Although there is a lack of high-quality evidence in the literature, several level II to IV studies revealed the risk factors as listed in Box 1 .

Subramanyam and colleagues also completed a systematic review of risk factors for SSI in a pooled population of pediatric patients with spinal deformity and found the following 5 factors statistically predictive of SSI:

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  Inappropriate antibiotic use (wrong drug, only clindamycin, incorrect dose or timing, and/or continuation beyond 24 hours after surgery)

  
  
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  Neuromuscular scoliosis

  
  
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  Instrumentation

  
  
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  Increased length of hospitalization

  
  
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  Residual postoperative curve (considered to be a marker of surgical invasiveness or length of procedure)

Speculation as to the reason for a higher risk in patients with NMS includes a higher rate of urinary and fecal incontinence leading to wound contamination, excessive tension on the wound from body habitus, and poor preoperative nutritional status.

Preventative strategies

Despite increased awareness of risk factors for SSI, there is a void in the literature of high quality evidence for infection prevention strategies. Glotzbecker and colleagues performed a survey in 2013 among Pediatric Orthopedic Society of North America/Scoliosis Research Society (POSNA/SRS) members and found significant variability in the current practices of spinal deformity surgeons. It was postulated that this variability results from lack of good evidence and may reflect suboptimal care. Glotzbecker and colleagues’s systematic review found insufficient evidence to recommend numerous preventative tactics, highlighting the need for high-quality research.

The best attempt thus far to fill this void is the 2013 seminal article in which Vitale and colleagues developed a best practice guideline (BPG) for SSI prevention in high-risk pediatric spine patients. Given the lack of high-quality literature, the BPG relies heavily on the expert opinion of experienced pediatric spine surgeons and pediatric infectious disease specialists. Agreement of greater than 80% of the panel constituted consensus for 14 prevention strategies. These guidelines are listed in Box 2 . No consensus (<80% agreement) was reached on preoperative methicillin-resistant Staphylococcus aureus (MRSA) screening, chlorhexidine skin prep, titanium versus cobalt chrome implants, saline versus dilute povidone-iodine irrigation, pulse lavage, gentamicin in bone graft, and postoperative subcutaneous drains, thereby highlighting targets for additional research.

The important question is whether combined strategies, when placed into a care plan, will successfully reduce SSI risk. Vitale and colleagues surveyed all sites involved in the creation of the BPG; after 1 year of implementation at their respective institutions, the rates of adherence to the guidelines were high and infection rates for high-risk spine patients remained stable or decreased almost universally.

Ryan and colleagues described a standardized multidisciplinary infection-prevention protocol at a large children’s hospital that led to an absolute risk reduction of 3.6% after implementation. Another large academic center’s infection-prevention protocol decreased infection rates from 7.8% to 4.5% overall and from 12.9% to 6.5% in high-risk pediatric patients. Although these numbers did not reach statistical significance, the results were clinically meaningful with a relative risk reduction approaching 50%, demonstrating the effectiveness of these multidisciplinary infection-prevention protocols.

Although implementing systemic changes has the laudable end goal to reduce SSIs, careful long-term assessment of these systems needs to occur in order to guarantee that the positive reductions in infections represent true sustainable changes rather than simply an example of the Hawthorne effect. Determining which strategies are most effective at reducing SSI rate should continue to be a major focus of research in future years.

Antibiotic prophylaxis

Despite widespread antibiotic availability and improved knowledge of causative organisms of SSI in pediatric spine patients, there remains considerable variability in hospital protocol for antibiotic prophylaxis. Traditional first-line therapy is prophylaxis against gram-positive bacteria with a first-generation cephalosporin, such as cefazolin. The recommended prophylactic dosing of cefazolin has recently increased from 20 mg/kg to a higher dose of 30 mg/kg for pediatric patients. The use of clindamycin alone is no longer considered adequate, as literature shows it is an independent risk factor associated with SSI.

Although no study has systematically examined the benefits of broad-spectrum antimicrobials (such as aminoglycosides or third/fourth-generation cephalosporins), grade B evidence in Glotzbecker and colleagues’s systemic review showed that gram-negative organisms more frequently cause infections in patients with NMS. This finding prompted consensus on using preoperative prophylaxis against gram-negative pathogens, in addition to cefazolin, in Vitale and colleagues’s BPG for high-risk patients. This recommendation will represent a substantial change in practice, given that only 32% of 37 US children’s hospitals and only 47.1% of surveyed POSNA/SRS members used gram-negative antimicrobials in patients with NMS before the BPG.

Additional grade B evidence has revealed that inappropriate timing, dosage, or redosing also increases SSI risk. This finding prompted recommendation for monitoring adherence to perioperative antimicrobial regimens in Vitale and colleagues’s BPG. As Khoshbin and colleagues found that compliance with antibiotic prophylaxis significantly reduced the SSI rate in pediatric surgery by 30%, improving the compliance rate in spine surgery should clearly be a focus at all institutions to reduce the SSI rate.