summary Prosthetic joint infections are serious complications of hip and knee arthroplasty and a common cause for revision arthroplasty Diagnosis is multifaceted and includes elevated inflammatory markers, radiographic changes around the prosthesis, and aspiration results Treatment generally involves prolonged IV antibiotics and two-stage revision arthroplasty Epidemiology Incidence primary joint replacement 1-2% TKA vs. 0.3-1.3% THA revision joint replacement 5-6% TKA vs. 3-4% THA Risk factors preoperative active infection login to view 2 more bullets previous local surgery/prior local infection postoperative immune suppression login to view 10 more bullets inflammatory arthropathy login to view 3 more bullets lifestyle factors login to view 5 more bullets Etiology Pathophysiology most common bacterial organisms include Staphylococcus aureus Staphylococcus epidermidis coagulase-negative Staphylococcus (chronic infections) most common fungal pathogen Candida species (e.g. Candida albicans) Prophylaxis screening screen and optimize risk factors nasal mupirocin for decolonization of nasal MSSA/MRSA routine urine cultures NOT warranted preoperatively, unless history or symptoms of UTI stop DMARDs 4-6 weeks prior to surgery revision joint replacement login to view 1 more bullet patients with a reported allergy to cephalosporin or penicillin antibiotics should undergo preoperative allergy screening operatively preoperative skin cleansing with antiseptic wash systemic antibiotics login to view 6 more bullets operative room login to view 2 more bullets postoperatively antibiotic prophylaxis prior to dental work is dependent on host risk factors Classification Time of onset acute infection infection within 3-6 weeks of surgery login to view 1 more bullet biology login to view 3 more bullets S. aureus commonly associated with acute THA PJIs chronic infection infection more than 3-6 weeks from surgery login to view 1 more bullet biology login to view 10 more bullets Source of infection direct invasion sinus tract into joint capsule wound dehiscence hematogenous infection infection in a longstanding infection-free joint secondary to another infection (e.g. dental work, infected gallbladder) Presentation History may have history of the following: recent or active bacteremia multiple local surgeries skin/epithelial tissue penetration (e.g. IV drug use, colonoscopy, dental work, ulceration, wound complication) Symptoms persistent pain and stiffness at site of arthroplasty is associated with infection in >90% of patients acute onset with swelling, tenderness, and drainage chronic infections have pain and more subtle symptoms function deteriorates over time pain worsens over time Physical exam inspection sinus tract to the joint is a definite infection warmth, redness, or swelling low grade fever motion limited by pain and swelling Imaging Radiographs findings periosteal reaction scattered patches of osteolysis generalized bone resorption without implant wear transcortical sinus tracts implant loosening Bone scan modality Tc-99m (technetium) detects inflammation and In-111 (indium) detects leukocytes triple scan can differentiate infection from fracture or bone remodeling indications if infection is suspected but cannot be confirmed by aspiration or blood work sensitivity and specificity 99% sensitivity and 30-40% specificity Positron emission tomography (PET) indication may help to identify areas of high metabolic activity using fluorinated glucose sensitivity and specificity 98% sensitivity and 98% specificity diagnostic criteria 2018 criteria for prosthetic joint infections as defined by Parvizi and associates derived from 2011 MSIS; 98% sensitivity and 99.5% specificity for diagnosing PJI major criteria (diagnosis can be made when 1 major criteria exist) sinus tract communicating with prosthesis pathogen isolated by culture from 2 separate tissue/fluid samples from the affected joint minor criteria (preoperative diagnosis) the scores below are added together to determine: login to view 1 more bullet serum labs login to view 2 more bullets synovial fluid analysis login to view 6 more bullets inconclusive (inconclusive preoperative score (2-5) or dry aspiration) positive histology (>5 PMN/hpf in 5 hpf at x400 magnification (intraoperative frozen section of periprosthetic tissue)) - 3 points purulence in affected joint - 3 points single positive culture - 2 points preoperative score + intraoperative score combined login to view 1 more bullet Studies Labs blood panel WBC login to view 1 more bullet ESR and CRP CRP login to view 6 more bullets ESR login to view 6 more bullets serum interleukin-6 (IL-6, normal <10 pg/mL) physiology login to view 3 more bullets outcomes login to view 7 more bullets Joint aspiration indications whenever there is a strong suspicion, diagnostic confirmation lab order request cell count and differential crystals Gram stain cultures and specificity outcomes cell count and differential login to view 6 more bullets Gram stain login to view 3 more bullets repeat aspiration login to view 2 more bullets other tests alpha-defensin immunoassay test login to view 3 more bullets leukocyte esterase colorimetric strip test Perioperative analysis microbiology definitive diagnosis can be made if the same organism is obtained by repeat aspirations or at least 3 of 5 periprosthetic specimens obtained at surgery login to view 3 more bullets histology intraoperative frozen section login to view 4 more bullets Treatment Nonoperative chronic suppressive antibiotic therapy indications login to view 3 more bullets outcomes login to view 2 more bullets Operative Debridement, Antibiotics, and Implant Retention (DAIR) indications login to view 2 more bullets techniques login to view 1 more bullet outcomes login to view 4 more bullets one-stage replacement arthroplasty indications login to view 3 more bullets technique login to view 1 more bullet advantages login to view 2 more bullets disadvantages login to view 1 more bullet outcomes login to view 1 more bullet two-stage replacement arthroplasty indications login to view 9 more bullets techniques (see section below) login to view 1 more bullet outcomes login to view 4 more bullets resection arthroplasty indications login to view 5 more bullets disadvantages login to view 1 more bullet technique login to view 1 more bullet outcomes login to view 2 more bullets arthrodesis indications login to view 2 more bullets outcomes login to view 1 more bullet amputation indications login to view 2 more bullets technique login to view 1 more bullet Techniques Surgical debridement and polyethylene exchange debridement modular parts should be removed to remove fibrin layer between plastic and metal parts (acts as a nidus of infection) polyethylene exchange be sure component available Two-stage replacement arthroplasty prosthetic explant surgical debridement must debride bone-implant interface and soft tissues antibiotic spacer and IV antibiotics advantages of spacers login to view 1 more bullet disadvantages of spacers login to view 3 more bullets static or dynamic (articulating) spacers can be used advantages of static spacers login to view 3 more bullets advantages of articulating spacers login to view 5 more bullets spacer antibiotics login to view 4 more bullets IV antibiotics login to view 12 more bullets reimplantation send tissue specimens for culture and frozen section pathology implant only if all preoperative and intraoperative measures are acceptable if intraoperative frozen section demonstrates acute inflammation, debride the wound, reapply cement spacer, and return later use antibiotic-impregnated cement when using cement Local Antibiotics Properties active against the organism can be incorporated into delivery vehicle (PMMA) thermo stable (will not denature during exothermic polymerization reaction) Choices aminoglycosides (gentamicin, tobramycin) effective against gram-negative bacilli synergistic against gram-positive cocci (Staphylococcus, Enterococcus) low risk of systemic toxicity Vancomycin effective against gram-positive cocci excellent elution properties Doses low dose = 2 g antibiotics:40 g of cement commercial antibiotic cement is low dose login to view 6 more bullets associated with lower infection rate high dose ≥3.6 g antibiotics:40 g of cement highest doses without systemic toxicity login to view 2 more bullets practical dose vancomycin is 1 g per vial, tobramycin is 1.2 g per vial use 3 g vancomycin and/or 3.6 g tobramycin in 40 g cement login to view 1 more bullet Elution properties rapid release in initial 24 h followed by rapid decline in release rate combination dosing (both tobramycin + vancomycin) increases release rate of antibiotics (more than if each were used alone) low levels at 5 weeks experimental models do NOT show difference in elution/concentrations in conventional wound closure vs negative-pressure wound therapy (NPWT) Mixing vacuum mixing removes air bubbles enhances mechanical properties may increase/decrease antibiotic elution rates hand mixing may lead to uneven distribution of antibiotics within cement and inconsistent release sequence of ingredients adding vancomycin powder after cement powder + liquid monomer mixed for 30 s results in greater elution Newer techniques vancomycin powder directly into wounds (mostly in spine literature) antibiotic cement coated IM nails local antibiotics bonded to implant surface Complications Failure to eradicate infection poorer prognosis for two-stage revision for methicillin-resistant organisms