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Postoperative Infections of the SpineABCDFigure 3. Deep infection (A) was removed during debridement (B–D) in 49-year-old patient.in patients undergoing neurosurgical procedures, including spinal operations. Malis and Savitz have repeatedlyadvocated use of prophylactic antibiotics during neurosurgical cases.48-51 In a retrospective review, Horwitz andCurtin52 reported decreased rates of infection in patientsreceiving antibiotics compared with patients not receiving antibiotics before lumbar laminectomy.Barker53 reported a meta-analysis of 6 prospectiverandomized clinical trials of prophylactic antibiotictherapy during spine surgery. Although no individualtrial demonstrated a statistically significant effect ofprophylactic antibiotic therapy on infection rates, thepooled analysis showed an OR of 0.37 (P .001), indicating efficacy for antibiotic prophylaxis. One of thesestudies, by Rubinstein and colleagues,54 was the onlyrandomized clinical trial focused exclusively on spinalsurgery. The authors found a reduced rate of infectionafter “laminectomy or discectomy” in patients whoreceived a single dose of cefazolin (4.3%) versus placebo(12.7%). Although the difference was not statisticallysignificant, the study likely was not sufficiently powered,and significance likely would be reached with a largerstudy population.First- or second-generation cephalosporins (eg,cefazolin, cefuroxime) are the antibiotics of choice,as they provide adequate coverage of Gram-positiveorganisms, including S aureus and S epidermidis, 2 ofthe most common causative agents. Patients colonizedor infected with methicillin-resistant S aureus (MRSA)and patients with cephalosporin allergy should receivea combination of vancomycin and gentamycin. Theaddition of gentamycin not only increases bactericidalpotential but specifically provides penetration to thedisk, helping to prevent discitis.31 Patients who are atlow risk for MRSA and are scheduled for high-riskprocedures may benefit from MRSA screening in thepreoperative period.A single parenteral dose of antibiotics should begiven during induction of anesthesia, approximately 30minutes to 60 minutes before time of incision, to allowfor adequate tissue penetration. For prolonged surgicalE266 The American Journal of Orthopedics procedures, intraoperative doses of antibiotics (50% ofthe initial dose) should be administered at intervals 1to 2 times the half-life of the medication: every 4 hoursfor cephalosporins and every 8 hours for vancomycinand gentamycin. These antibiotics should be used judiciously, particularly in patients with renal impairment.Continuing prophylactic antibiotics for an extended period after surgery is not recommended. Takahashi and colleagues55 reported an inverse relationship with durationof postoperative antibiosis and infection incidence. Theirfindings also emphasize the importance of administeringantibiotics before, or at time of, anesthesia. Comparedwith patients who received perioperative antibiotics,patients who received antibiotics only after surgery hadthe highest rate of infection, even though they receivedantibiotics over the longest period (7 days). Althoughmany surgeons prefer to extend the duration of antibioticuse to “cover” wound drains or lines, this practice is notsupported by any class I or II evidence and increases therisk for secondary infections with antibiotic-resistantorganisms.The recommendations for antibiotic prophylaxis forprevention of discitis are less established. No prospective randomized clinical trials have evaluated the efficacy of prophylactic antibiotics in patients at risk fordeveloping discitis. The only requirement for antibioticchoice is in vitro coverage against staphylococci. Severalpharmacokinetic studies have suggested that β-lactamshave poor penetration into the disk space, whereas otherantibiotics (aminoglycosides, clindamycin) achieve therapeutic concentrations in the disk space.56-61 Surgeonsmay still use β-lactams based on their own positiveoutcomes but should administer such medications atmaximal dosages. They may also use antibiotics thathave been found to penetrate the disk space (gentamycin, clindamycin), despite the lack of clinical studiesadvocating their use.31Irrigation and Drainage SystemsDespite advances in aseptic technique and innovations inairflow systems, operating theater contamination of a surwww.amjorthopedics.com

J. E. Bible et alTable. Reported Risk Factors forPostoperative Spinal InfectionsSurgery relatedStaged procedureRevision procedureProlonged operative timeHigh volume of moving operating room personnelInstrumentationPosterior approachLumbar spineTumor resectionExcessive blood lossPatient relatedAdvanced age ( 60 y)Higher American Society of Anesthesiologists classObesity (higher body mass e glucose controlRheumatoid arthritisPrevious surgical infectionInfection at remote sitesPrevious spine surgeryAlcohol abuseSteroid therapyPoor nutritional statusAcute spine injury (trauma)Postoperative incontinenceComplete neurologic deficitProlonged preoperative hospitalizationgical wound remains a concern in all surgical procedures.In spine surgery, extensive and prolonged exposure ofthe posterior spinal structures places these procedures atincreased risk for surgical site infection. Several surgeonsuse irrigation solutions and wound drainage systems in aneffort to minimize the risk for infection.In a randomized controlled trial, researchers compared the efficacy of prophylactic antibiotics versuswound irrigation with povidone-iodine in patients whounderwent lumbar disk surgery.62 Povidone-iodine irrigation had a statistically significant benefit in terms ofreduced incidence of postoperative surgical site infection. However, the study did not control for physicalcleansing of wounds. Saline lavage has been reported toreduce the number of colony-forming units in woundsby approximately 30%.63 Some authors have suggestedwounds are effectively decontaminated after irrigationwith dilute (40 ppm) aqueous elemental iodine.31 Theeffect that even this small amount of iodine has on tissues remains unclear. In vitro and animal studies havewell described the inhibitory effects of iodine on osteoblasts and fibroblasts, while a prospective study of 244cases found no significant difference in fusion rates andwound healing between iodine and saline irrigation.64-66Several authors have evaluated the efficacy of antibiotic-containing saline solutions in the prevention ofsurgical site infections. Malis48 reported on irrigationwith saline that contained streptomycin and use ofprophylactic IV vancomycin and gentamicin, and Savitzand colleagues63 described irrigation with polymyxinwww.amjorthopedics.comand bacitracin and prophylactic IV cefazolin. Both studies reported no postoperative infections, though the relative contribution of irrigation is difficult to ascertain, asboth studies used prophylactic IV antibiotics.The literature suggests that regular, frequent salineirrigation may have efficacy in preventing wound infection in spinal procedures, which require prolonged,extensive exposure. Surgeons may supplement irrigation solutions with iodine. Adding antibiotics to theirrigation solution, though common practice for manysurgeons, lacks extensive support in the literature.31However, preclinical animal studies have yielded promising results for reducing postoperative infections with useof intraoperative implantation with antibiotic microspheres or with injection of antibiotic directly into thetissue.36,67 In the only human study of prophylactic localantibiotics, adding vancomycin powder to standardsystemic prophylaxis in elective spine surgery reducedinfection rates from 2.6% to 0.2%.68Surgeons may place a closed-wound suction drain(Jackson-Pratt) in an effort to reduce the incidence ofhematoma or infection at the surgical site, though thispractice has minimal support in the literature. Payne andcolleagues69 reported that presence or absence of sucha drain did not affect the postoperative infection rate,or the incidence of hematoma in patients who underwent single-level laminectomy. Brown and Brookfield70reported on use of closed-wound suction after multileveldecompression, decompression and fusion with andwithout instrumentation, and reoperation decompression in the lumbar spine. In their randomized study,they reported no infections or epidural hematomas inpatients who did or did not receive drains. Althoughthese studies suggest it may be reasonable to minimizedrain use, the decision to use a closed-wound suctiondrain is at the surgeon’s discretion.Clinical PresentationIncreased pain and tenderness to palpation around thesurgical site are common clinical symptoms of a postoperative spinal infection. Although some discomfortfrom the incision and the muscle dissection is common,clinicians should become more concerned about infectionif the discomfort intensifies or returns after a discomfortfree period. Patients may present with systemic complaintsof fever, chills, or malaise, but not always. A retrospectivereview of 2391 spinal procedures found that fewer thanone-third of the patients with a postoperative woundinfection were febrile at presentation.14 Conversely, mostfevers that occur after spine surgery have no identifiableinfectious focus.71 Wound discharge and wound dehiscence, or erythema, were the most common presentingproblems, each occurring more than 90% of the time.14Although rare, neurologic deficits may be seen secondaryto direct compression of neural elements.It is important to consider that tight fascial closuresmay allow deep-seated infections to fester without anyDecember 2011 E267E265

Postoperative Infections of the Spineobvious superficial manifestations. As a result, treating physicians must not dismiss this diagnosis simplybecause an incision does not exhibit any drainage,erythema, or other clinical signs of a superficial infection. Unfortunately, after surgery, there is often a delay(mean, 15 days; range, 5-80 days) for a wound infectionto declare itself, so any clinical evidence of a spinalinfection warrants close monitoring or even presumptivemanagement.14Diagnostic StudiesLaboratory StudiesGiven the inconsistency in presenting signs and symptomsof postoperative spinal infections, laboratory studies maybe extremely helpful in establishing the diagnosis. Whiteblood cell counts may be elevated or within the normalrange in cases of spinal infections. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level areboth sensitive markers of infection, with CRP thought tobe more specific.40 These laboratory indicators are normally elevated after spinal procedures. ESR, on average,peaks 5 days after surgery and takes a slow, increasingcourse before normalizing.72 It often remains elevatedlonger than 21 days to 42 days after surgery. Along withtaking a more predictable course, CRP increases morerapidly, peaking 2 days to 3 days after surgery, and normalizes sooner, within 5 days to 14 days.73 Thus, theselaboratory studies must be interpreted in light of the normal alterations known to accompany any type of surgicalintervention. In any patient with a potentially infectedwound, obtaining a baseline laboratory profile may provide additional information supporting this diagnosis.As these values would be expected to gradually return tonormal in an unaffected individual over time, an upwardtrend or second rise should raise the level of suspicion foran untreated spinal infection.ImagingPlain radiographs of the operated spinal segments shouldbe considered in any patient returning with symptomssuggestive of postoperative infection in order to rule outunderlying abnormalities that might alternatively accountfor the clinical presentation. These abnormalities includeearly implant loosening, abnormal soft-tissue swelling,and retained foreign body. Other, more subtle radiographic findings are disk space narrowing and blurring ofadjacent endplates after only 2 weeks of infection.74 Thisoccurs as proteolytic enzyme-producing pathogens, suchas S aureus, spread into the disk and adjacent-vertebraendplates.75In the absence of radiographic findings, cross-sectional imaging, such as computed tomography (CT)and magnetic resonance imaging (MRI), may be indicated. CT provides excellent visualization of possiblebony involvement but is inferior to MRI in evaluatinginfection in its early stages.76 MRI becomes especially E268E266 TheThe AmericanAmerican JournalJournal ofof OrthopedicsOrthopedics helpful in assessing the spinal canal, including epiduralabscesses (Figure 1). The T1-weighted signal of epiduralfat and connective tissue is commonly decreased, whileT2-weighted images are hyperintense. T1-gadoliniumsequences can illustrate the peripheral enhancement ofan epidural mass.77,78 For discitis, decreased bony signalon T1-weighted images and increased bony signal onT2-weighted images can be seen. In addition, there canbe gadolinium enhancement of vertebral endplates anddisk space, with sensitivity and specificity over 90%.79-82Even with these advanced imaging modalities, thediagnosis of a wound infection can be difficult to confirm, as deep perispinal fluid collections may not be ableto be differentiated from normal postoperative changes.After surgery, there is some increased T2-weighted signaland contrast uptake at the surgical site, and some nonspecific peripheral contrast enhancement may also beseen. Artifact from instrumentation can further complicate visualization of the surrounding structures. Thereis an interesting new radiographic finding with use ofbone morphogenetic protein 2 (BMP-2), a very powerful inflammatory agent that can cause osteolysis of thevertebral body, which is usually self-resolving (Figure2). BMP-2 can appear as discitis or osteomyelitis of thevertebral body on imaging studies.83 It can be differentiated from true infection in that infectious indices areoften normal.CulturesIsolation of the infectious organism is paramount foraccurate and appropriate management of the infection.Superficial wound cultures are usually not necessary andare of limited use in the postoperative patient populationbecause they are at significant risk for contamination.Blood cultures should always be drawn when a systemicinfection is suspected. If the etiology remains unclear orimprovement is not seen, a needle biopsy of the affectedarea may be a reasonable option to access deep fluidloculations that cannot be differentiated from postoperative hematomas. Intraoperative cultures demonstrate thehighest sensitivity and specificity for confirming presenceof an active wound infection and identifying the pathogeninvolved. For this reason, in cases of operative intervention, a comprehensive set of wound cultures should beobtained at time of surgery.ManagementMedical management of a suspected superficial postoperative spinal infection may be considered in the absence ofa palpable abscess or fluid collection on imaging studies.84It cannot be emphasized enough that management of anywound infection with antibiotics alone requires extremevigilance on the part of the treating clinician in orderto rule out any disease progression or involvement ofdeeper tissues. Response to medical management may bemonitored by assessing the superficial appearance of theincision and by following ESR, CRP, and other laborawww.amjorthopedics.comwww.amjorthopedics.com

J. E. Bible et altory studies. Furthermore, it is imperative that the treatingclinician ensures adequate nutritional supplementation inall patients with a suspected spinal infection.The mainstay of managing postoperative spinal infections is open irrigation and debridement. If there is sufficient clinical suspicion for a wound infection, this surgical intervention should be performed immediately, ona presumptive basis, and should not be delayed for confirmatory laboratory or imaging studies. The debridement itself should be extensive, including exposure ofsuperficial tissues and exposure beyond the fascial layer.Removal of all necrotic and devitalized tissue, both insuperficial layers and deeper muscle layers, is imperative. Strategies for managing any instrumentation andresidual bone graft present in the operative field remainsa matter of some controversy. Many surgeons leavespinal instrumentation in place, as the stability affordedby internal fixation not only is essential for proper management of the underlying spinal pathology but alsofacilitates fusion and resultant eradication of any infection. However, implant removal is preferable in cases ofclearly loosened instrumentation or delayed infectionwith solid fusion. In addition, instrumentation removalmay be considered when infection does not resolve aftermultiple debridements11 (Figure 3). In grossly infectedwounds, cement beads impregnated with tobramycin orvancomycin, and placed on a suture or wire can be usedto obtain much higher doses of local antibiotics withoutsystemic side effects. These beads are typically left infor approximately 3 days and then removed with repeatdebridement.85 Loose bone graft in the surgical site isusually removed, whereas any material that adheres tothe surrounding bony structures is often left in place.Many surgeons, having completed irrigation anddebridement, close the wound primarily over drains.Before closure, the skin edges should be clean andviable. Emphasis should be placed on obtaining a tight,layered closure to minimize dead space. Alternatively,a grossly infected wound may be left open for serialirrigation and debridement, until there is no evidenceof contamination and cultures are negative, at whichpoint delayed wound closure may be performed. Morerecently, various suction/irrigation and vacuum-assistedclosure (VAC) systems have been described; these systems may be of potential use in managing these infections.11,22,86-88 Spine wounds that do not heal, despiteadequate infection irradication and nutritional status,may require flap coverage.89Broad-spectrum antibiotics are typically initiatedafter surgery. The regimen may be tailored to the resultsof the intraoperative wound cultures. Antibiotic therapyis routinely continued for at least 6 weeks, and anysubsequent changes in medical management are basedon the clinical response and laboratory profile of eachpatient.Management of postoperative discitis often beginsconservatively. Most patients with a suspected diagnosiswww.amjorthopedics.comof discitis respond favorably to spinal immobilization withorthosis in conjunction with organism-specific antibiotics.If discitis is suspected on the basis of laboratory studiesor imaging findings, blood cultures should be obtainedin an effort to identify a pathogen and guide antibiotictherapy.90 If repeated blood cultures are negative, and ifthe suspicion for discitis remains high, CT-guided needlebiopsy should be considered as a guide to antibiotic treatment. If neither measure identifies a pathogen, broadspectrum antibiotics should be used.91 The duration ofantibiotic therapy varies, but a commonly administeredcourse consists of 6 weeks of IV therapy, followed by6 weeks of oral antibiotics. White blood cell, ESR,and CRP values should be used to monitor the clinicalresponse of the patient, particularly a patient with negative blood cultures.If there is clinical evidence that the infection is worsening, or if symptoms do not resolve after 6 weeks ofantibiotic treatment, open surgical intervention shouldbe considered. Surgical debridement usually involvesremoval of the disk and aggressive anterior debridement of necrotic tissue and bone. Reconstruction consists of anterior autograft fusion without instrumentation and posterior stabilization with instrumentation.Reconstruction has been described using a structuralautograft, allograft, or titanium cage with or withoutanterior plate fixation, and posterior stabilization withinstrumentation.92-94 In addition, BMP-2 has shownpromise in assisting with fusion in infection cases.95,96However, whether this is because of the inflammatorynature of BMP-2 or the decreased time to fusion is notclear. Minimally invasive techniques, such as percutaneous disk biopsy and debridement with possible fusion,have been described.97,98 These procedures have beenassociated with favorable outcomes, though they areassociated with vascular complications in the thoracicspine and are technically more difficult.97,98ConclusionsAlthough postoperative spinal infections are relativelyuncommon, a surgeon should maintain a high level ofsuspicion for their occurrence and should be vigilant toreduce their incidence. Risk factors such as diabetes andmalnutrition

Vanderbilt Orthopaedic Institute, Vanderbilt University School of Medicine. Address correspondence to: Jesse E. Bible, MD, MHS, Vanderbilt Orthopaedic Institute, Vanderbilt University School of Medicine, Medical Center East, South Tower, Suite 4200, Nashville, TN 3723