Overview postoperative spine infections are relatively common and have the potential to compromise patient outcomes through: increased morbidity increased reoperation rates increased length of hospital stay increased treatment costs estimated to be $200,000 per patient worse overall long-term outcomes increased mortality Epidemiology Incidence surgical site infection (SSI) most common hospital-acquired infection that occurs in the early postoperative period spine SSI occurs in 0.7-16% depending on the type of spine surgery, approach, instrumentation, and indication for surgery login to view 19 more bullets average time to infection 14 months Risk factors medical >70 y/o login to view 1 more bullet ASA score diabetes mellitus cardiovascular disease malignancy long-term steroid use previous lumbar surgery chronic obstructive pulmonary disease immunocompromised prior infection preoperative hospitalization >1 week malnutrition prior radiation lifestyle obesity smoking nutritional status login to view 1 more bullet ETOH intraoperative transfusions use of instrumentation staged interventions number of levels fused operating room traffic surgery lasting >3 hours blood loss >1 L hospital stay duration of patient stay in the postoperative anesthesia care unit prolonged preoperative hospital stay Etiology Pathophysiology instrumentation instrumentation has an important role in the development of postoperative infections can cause local soft tissue irritation, leading to inflammation and seroma formation that can provide a fertile breeding ground for microorganisms adherence of bacteria to the surface of implants is promoted by a polysaccharide biofilm (glycocalyx) that acts as a barrier against host defense mechanisms and antibiotics metallosis from micromotion of the instrumentation leads to granuloma formation and provides another medium for bacterial colonization microbiology Staphylococcus aureus login to view 3 more bullets Staphylococcus epidermidis login to view 1 more bullet Escherichia coli & Enterococcus faecalis login to view 1 more bullet Cutibacterium acnes (formerly Propionibacterium acnes, low virulence microorganisms) login to view 2 more bullets Gram-negative rods login to view 6 more bullets polymicrobial login to view 2 more bullets Anatomy Muscles psoas muscle can be site of abscess extension from lumbar discitis presents with hip and thigh pain Ligament anterior longitudinal ligament Blood supply segmental spinal arteries Classification Anatomic superficial limited only to the skin or subcutaneous tissues without fascial involvement deep involves the fascia and/or muscle login to view 1 more bullet Chronologic early occurs within 3 weeks of the procedure late occurs >4 weeks after the procedure latent years after the procedure Mechanism direct inoculation contamination during surgery login to view 1 more bullet leads to infection within 30 days early postoperative (outside-in) contamination drains seroma drainage creating outside-in contamination soiling of wounds late hematogenous contamination dental work UTI, bacteremia, etc. Thalgott classification based on host factors and severity of infection host factors login to view 3 more bullets anatomic factors login to view 5 more bullets Presentation History may report night sweats Symptoms wound drainage most common presentation increasing pain that increases over time postoperative pain should improve over time constitutional symptoms fever is the most common generalized finding login to view 1 more bullet sepsis malaise lethargy confusion hypotension organ failure is an indication for emergent surgical debridement Physical exam wound erythema or discharge is common with superficial infections may be clean with deep infections drainage login to view 2 more bullets tenderness Imaging Radiographs rarely useful for the diagnosis of early infection findings acute login to view 1 more bullet late and latent login to view 3 more bullets CT indications concern for fusion status and implant positioning views best seen on sagittal and axial images findings may show multiple lesions involving the endplates lytic lesions around the screws/implants presence of pseudarthrosis MRI indications most useful study to diagnose SSI login to view 1 more bullet technique gadolinium enhancement improves diagnostic accuracy and should be used when infection is suspected login to view 1 more bullet findings suggestive of infection rim enhancement of a large fluid collection is pathognomonic for infection ascending epidural collections evidence of bony destruction progressive marrow changes inflammatory response following surgery is similar to the response seen with infection Bone scan indications patients unable to undergo MRI (e.g. patients with a non-MRI-compatible pacemaker) rarely used WBC-labeled scan may be helpful for identifying an infectious focus Studies Serum labs hbA1c obtain preoperatively for all diabetic patients should be <7.0 WBC unreliable indicator of infection ESR can remain elevated for up to 6 weeks after surgery rising levels after the fourth postoperative day can be suggestive of infection CRP levels normalize within 2 weeks peaks around postoperative day 2 login to view 1 more bullet more sensitive indicator of the presence of SSI has been reported to be the most sensitive clinical laboratory marker in assessing the presence of infection and treatment response login to view 1 more bullet albumin <3.5 g/dL is concerning for malnutrition transferrin <150 μg/dL is concerning for malnutrition Cultures superficial skin cultures superficial cultures, whether from the skin or drainage, do not reliably assist with identification of the causative organism aspiration intraoperative intraoperative tissue cultures remain the gold standard for identification of the causative organism in cases of SSI login to view 7 more bullets Differential Key differential (top 4) adjacent segment disease inadequate decompression postoperative seroma postoperative hematoma Treatment Nonoperative oral antibiotics and close observation indications login to view 1 more bullet Operative urgent surgical debridement, wound management +/- plastic surgery consult, ID consult, and targeted IV antibiotics indications login to view 5 more bullets indications for hardware removal login to view 3 more bullets indications to retain hardware login to view 2 more bullets titanium implants are best for infection cases outcomes login to view 2 more bullets Techniques Oral antibiotics and close observation technique keflex, bactrim, clindamycin, or augmentin login to view 6 more bullets local wound care login to view 2 more bullets Urgent surgical debridement, wound management +/- plastic surgery consult, ID consult, and targeted IV antibiotics treatment goals eradicate infection wound healing maintain mechanical integrity of instrumented fixation maintain viability of the bone graft approach utilize prior incision remove necrotic wound edges dissection should proceed down to the hardware to avoid violating the dura login to view 1 more bullet debridement debride in layered fashion pulse lavage with normal saline +/- antibiotics remove loose hardware reinstrumentation / extension of instrumentation restore spine stability login to view 3 more bullets wound management multiple debridements if needed login to view 1 more bullet remove all loose bone graft negative-pressure wound therapy (NPWT) dressings and closed suction irrigation systems are becoming increasingly popular to support the wound healing process muscle and local rotational flaps for large soft tissue defects wound closure non-braided suture tension-free closure login to view 2 more bullets antibiotic beads drains multiple drains (superficial and deep) NPWT targeted IV antibiotics obtain cultures and treat with targeted agents login to view 2 more bullets usually requires 6 weeks of IV antibiotics PICC line monitor ESR/CRP serial MRIs are usually not indicated prolonged IV antibiotic therapy can delay hardware removal long enough to allow solid fusion to occur Complications Wound complications Pseudarthrosis Neurologic deficits/paralysis Sepsis End organ failure Death Worse overall outcomes Prognosis Can seriously compromise patient outcomes Prevention Preoperative decrease modifiable risk factors lifestyle login to view 3 more bullets medical login to view 5 more bullets Intraoperative skin preparation shaving (clippers preferred over razor) isopropyl alcohol surgical prep room sterility sterile technique minimize room traffic preoperative antibiotics significantly decrease postoperative spinal wound infections login to view 1 more bullet administered within 1 hour of skin incision login to view 1 more bullet antibiotic selection login to view 10 more bullets length and complexity of surgery decrease invasiveness of surgery (area of surgical bed) decrease surgical time decrease blood loss wound antibiotics antibiotic irrigation (holy water) login to view 1 more bullet vancomycin powder login to view 3 more bullets betadine soaks 0.3% betadine soaks for 2 minutes frequent release of retractors during the procedure at least every 2 hours reduces tissue necrosis debridement of necrotic tissue retracted muscle tissue may succumb to pressure necrosis hemostasis seromas and hematomas can subsequently get infected drains evacuate postoperative hematomas or seromas some studies have not found a difference in SSI with drain usage NASS does not recommend routine drain usage after single-level procedures vacuum-assisted closure Postoperative antibiotics should only be continued for 24 hours postoperatively