Overview. Overview postoperative spine infections are a relativley common complication that has the potential to seriously compromise patient outcomes through increased morbidity increased mortality increase reoperation increased hospital stay increased treatment costs estimated to be $200,000 per patient worse overall long-term outcomes Epidemiology Incidence surgical site infection (SSI) general the most common hospital acquired infection that occurs in the early postoperative period spine surgical site infection (SSI) occurs in .7% to 16% depending on type of spine surgery, approach, use of instrumentation, and indication for surgery incidence of SSI in their series following orthopedic spinal operations is 2.0% incidence of some procedures lumbar micodiskectomy with prophylactic antibiotics has a reported 0.7% incidence of infection. use of an operating microscope for diskectomy doubles this rate to 1.4%. lumbar fusion risk of infection is higher with spinal fusion because of the presence of spinal instrumentation in elective surgical instrumented cases, the incidence of infection has been reported to be 2.8% to 6% fracture stabilization/trauma traumatic spine injury has an increased infection risk of up to 10% greater local tissue hypoxia, longer ICU stays, and greater soft tissue damage, catabolic state leading to protein malnutrition, and greater comorbities contribute to increased infection risk risk factors associated with trauma-related SSIs: multilevel spine surgery treatment delay >160 hours complete neurologic deficit severe congnitive impairment anterior vs. posterior posterior spine procedures have a statistically higher incidence of infection postoperatively compared with anterior instrumentation combined anterior/posterior cases do not carry a higher risk of infection than does posterior surgery alone average time to infection 14 months Risk factors medical patient age >70 years may be confounded by older patients having more comorbidities ASA score diabetes mellitus cardiovascular disease malignancy long term steroid use previous lumbar surgery chronic obstructive pulmonary disease immunologic competency prior infection preoperative hospitalization >1 week malnutrition prior radiation lifestyle obesity smoking nutritional status malnourished patients are 15x more likely to develop an infection ETOH intraoperative transfusions use of instrumentation multiple staged interventions amount of levels fused operative room traffic (large number of nurses) surgery lasting longer than 3 hours blood loss >1 L hospital stay duration of patient stay in the postanesthesia care unit prolonged preoperative hospital stay Etiology Pathophysiology pathophysiology instrumentation the use of instrumentation has an important role in the development of postoperative infections can cause local soft tissue irritation leading to inflammation and seroma formation that subsequently provides a fertile breeding ground for microorganisms to grow adherence of bacteria to the surface of implants is promoted by a polysaccharide biofilm called glycocalyx that acts as barrier against host defense mechanisms and antibiotics metallosis from micromotion of the instrumentation leads to granuloma formation and provides yet another medium for bacterial colonization microbiology staphylococcus aureus 73% most frequent microorganism found in spinal SSI is Staphylococcus aureus 5-18% can me methicillin resistant staphylococcus aureus (MRSA) staphylococcus epidermidis increasing frequency in postoperative infections enterococcus coli & enterococcus faecalis patients with incontinence / faecal contamination propio acnes (low virulence microorganisms) patients with compromised immune system could present with surgical wound infected by low virulence microorganisms late hardware infection gram-negative rods generally uncommon cause of SSI trauma patients severe neurologic injury those in an immunocompromised state (injury severity score >18) higher incidence seen with neuromuscular scoliosis patients (cerebral palsy, Duchenne's muscular dystrophy, etc.) higher risk of soiling wound due to poor bowel and bladder control compounded with lack of baseline mobility polymicrobial almost exclusivley a result of direct wound contamination during the post-operative period fecal or urinary contamination of the wound in neuromuscular patients Anatomy Muscles psoas muscle can be site of abscess extension from lumbar discitis presents with hip and thigh pain Ligament anteior longitudinal ligament Blood Supply segemental spinal arteries Classification Anatomic superficial superficial infection are limited only to the skin or subcutaneous tissues without fascial involvement deep deep infections involve the fascia and/or muscle unlikely to respond to the standard 6-week course of antiobiotics alone Chronologic early early, if they occur within 3 weeks of the procedure late more than 4 weeks later latent years after surgery Mechanism direct inoculation contamination during surgery substantial amount of bacteria are needed at the operative site to cause SSI >105 organisms leads to infection within 30 days early posterative (outside-in) contamination drains seroma drainage creating outside-in contamination soiling of wounds late hematogentous contamination dental work foreign infection (UTI) Thalgott classification based on host factors and severity of infection host factors A - normal B - local or systemic disease (smoking, diabetes) C - immunocompromised anatomic factors 1 - single organism (deep or superficial) 2 - deep infection with multiple organisms require an average of 3 irrigation and debridements 3 - deep infection with multiple organisms and myonecrosis very difficult to manage and have poor outcomes Presentation History (optional) night sweats Symptoms wound drainage most common presentation increasing pain increase with time post-op pain should improve with time constitutional symptoms fever is the most common generalized finding with infection temperature >39°C is worrisome for a bacterial deep wound infection generalized sepsis generalized malaise lethargy confusion hypotension organ failure is an indication for emergent surgical débridement condition usually presents as generalized malaise, lethargy, and even confusion Physical exam wound wound erythema or discharge common with superficial infections wound may be clean with deep infections drainage persistent draining of a seroma will be clear copious or purulent discharge consistent with infection tenderness over surgical site Imaging Radiographs indications Plain radiographs of the spine are rarely useful for the diagnosis of early infection [8,9,16]. findings acute usually normal late & latent loss of disc height end plate erosion lucencies may be present around orthopedic hardware CT indications when concern for the fusion status and implant positioning views best seen on sagital and axial images findings computed tomography scan may show multiple lesions involving the end plates lytic lesions around the screws/implants presence of pseudoarthrosis MRI indications magnetic resonance imaging (MRI) is the most useful study to diagnose SSI [1,8-10,16] magnetic resonance imaging (MRI) is the most useful imaging study, but it must be interpreted with caution technique gadolinium enhancement improves the diagnostic accuracy of MRI and should be used whenever infection is suspected gadolinium enhancement increases the sensitivity of MRI 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 and ascending epidural collections on MRI scans are also diagnostic of infection sensitivity and specificity inflammatory response following surgery is similar to that seen with infection Bone scan rarely used WBC-labeled may be helpful for identifying and infectious focus indications: patient unable to tolerate MRI (e.g. pacemaker) Studies Serum Labs HgBA1C obtain preop for all diabetic patients should be < 7.0 WBC White blood cell count is an unreliable indicator of infection. ESR Erythrocyte sedimentation rate can remain elevated for up to 6 weeks after surgery rising levels after 4th postoperative day can be suggestive of an infection CRP C-reactive protein (CRP) levels normalize within 2 weeks peaks around post-op day 2 persistent high levels or 2nd peak is concerning for infection CRP is a more sensitive indicator of the presence of SSI CRP has been reported to be the most sensitive clinical laboratory marker in assessing the presence of infection and treatment response normalized CRP with improving ESR is suggestive of post-operative SSI resolution Albumin < 3.5 g/DL is concerning for malnutrition transferrin < 150 ug/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 introperative intraoperative tissue cultures remain the gold standard for identification of the causative organism in SSI cultures may be negative in latent infections culturing of removed hardware may yield offending organism due to bacteria "hiding" in the glycocalyx obtained prior to antibiotic adminstration Intraoperative biopsy samples gross anatomy histology/frozen sections immunostaining Differential Key differential (top 4) adjacent segment disease inadequate decompression postoperative seroma postoperative hematoma Treatment Nonoperative oral antibiotics and close observation indications only indicated for mild superficial infections Operative urgent surgical debridement, wound management +/- plastics, ID consult & targeted IV antibiotics indications vast majority of cases any infection that does not respond to antibiotics unacceptable spinal deformity neurologic deficits progression of infection on follow-up MRI studies indications for hardware removal loose hardware refractory infections latent infection and fusion obtained titianium implants are best for use in infection cases indications to retain hardware insufficient stability lack of solid fusion outcomes worse overall long term outcomes compared to index procedure without infection increased treatment costs Techniques Oral antibiotics and close observation technique keflex, bactrim, clindamycin or augmentin choice depends on pathogen of cocern keflex - MSSA keflex 500 mg TID vs. 250 mg QID bactrim - MRSA clindamycin - PCN allergic augmentin - anaerobes local wound care daily dressing changes betadine ointment to surgical wound with dressing changes Urgent surgical debridement, wound management +/- plastics, ID consult & targeted IV antibiotics treatment goals: eradicate infection obtain wound healing maintain mechanical integrity of instumented fixation maintain viability of the bone graft approach uilize prior incision remove necrotic edges of wound should approach down to hardware to avoid disecting into dura extensive scar tissue around dural sac can make determination of dural sac difficult debridement debride tissue in layered fashion pulse lavage with NS +/- antibiotics instrumentation removal remove loose hardware reinstrumentation / extension of instrumentation restore stability of spine upsize existing screws extend proximally if needed consider anterior procedure wound management: multiple debridement if needed remove all devitalized muscle tissue remove all loose bone graft negative pressure wound management dressings and closed suction irrigation systems is becoming more popular in the clinical management of infected wounds to support the wound healing process muscles flaps and local rotational flaps for large soft tissue defects wound closure non-braided suture tension-free closure may require paraspinal muscles flaps with plastic consults may use SPY which helps determine vacularity of wound antibiotic beads drains multiple drains (superficial and deep) wound vac targeted IV antibiotics obtain culture if possible and treat with targeted agents treatment depends on the culture results but generally infections with anaerobes as polymicrobial to be treated with broad spectrum antibiotics, such as vancomycin or metronidazole, administered i.v., for 6 weeks usually require 6 weeks of IV antibiotics obtain PICC line monitor CRP / ESR serial MRI usually not indicated prolonged IV antibiotic therapy can delay hardware removal long enough to allow a solid fusion to occur Complications Wound Complication Pseudoarthrosis Neurologic deficits / paralysis Sepsis End Orgain Failure Death Worse overall outcomes Prognosis Has the potential to seriously compromise patient outcomes Prevention Preoperative (prior to surgical admission) decrease changeable risk factors lifestyle weight loss smoking cessation abstinence from EtOH and drugs medical glucose control address other sites of infection UTI Nasal swaps povidone-iodine swabs for all patients or for MRSA carriers Intraoperative skin preparation (non sterile) shaving clippers preferred over razor isopropyl alcohol surgical prep room sterility proper sterile technique minimize room traffic prepping and draping preoperative antibiotics indications administered within 1 hour of skin incision significantly decrease the incidence of postoperative spinal wound infections some studies suggest may only decrease the severity of the infection should be given before incision and repeated when the operation exceeds 4 hours antibiotic selection no PCN allergy a first-generation cephalosporin (cefazolin most common) is the most commonly used prophylactic antibiotic usually 2g Q8hrs for the first 24 hours 3g Q8hr for obese patients (>100 kg of BMI >35kg/m^2) PCN allergy vancomycin or clindamycin are given to patients who are allergic to cephalosporins vancomycin dosing 1000 mg Q12hrs infusion needs to start >1hr from incision to allow for sufficient tissue levels of antibiotic clindamycin dosing 900 mg Q8hrs patients at risk for MRSA should be treated with prophylactic vancomycin length and complexity of surgery decrease invasiveness of surgery (area of surgical bed) decrease time of surgery decrease blood loss wound antibiotics antibiotic irrigation (holy water) mix with normal saline vancomycin powder The use of powdered vancomycin locally administered during surgery has been associated with reduced SSI rates high local tissue concentrations for several several days post-op vancomycin powder has been linked to increased gram-negative organism infections if they do occur betadine soaks 0.3% betadine soak for 2 minutes frequent release of retractors during procedure at least every 2 hours reduces amount of tissue necrosis at the end of the procedure debridement of necrotic tissue at the end of the procedure muscle tissue that was retracted may become necrotic from pressure necrosis hemostasis seroma and hematoma can subsequently get infected drains evacuates any postoperative hematoma or seroma some studies have not found a difference in SSI with the use of drains the routine use of drains is not recommended after single-level procedures by NASS vacuum-assisted closure dressings/wound vac Postoperative postoperative antibiotics continued postoperatively for no longer than 24 hours