Updated: 4/23/2020

Shoulder Prosthetic Joint Infection

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Introduction
  • Overview
    • Periprosthetic shoulder infection serves as the major cause for revision within the first 2 years after shoulder arthroplasty
      • treatment most commonly includes a 2-stage revision
  • Epidemiology
    • incidence
      • ~4% for primary TSA and RSA 
      • ~15% for revision TSA and RSA
    • demographics
      • males more likely to be colonized with Cutibacterium acnes (formerly known as Propionibacterium acnes) 
    • risk factors 
      • psotoperative hematoma
      • intra-articular steroid injection within 3 months of surgery 
      • smoking
      • young age
      • male gender
      • arthroplasty for trauma
      • revision surgery
  • Pathophysiology
    • pathobiology
      • micro-organisms most commonly isolated:
        • Staphylococcus aureus (most common)
        • Staphylococcus epidermidis
        • Cutibacterium acnes  
          • characteristics
            • gram-positive, facultative, aerotolerant, anaerobic rod that ferments lactose to propionic acid
            • concentrated in the axilla within the dermal sebaceous glands
            • forms biofilm within 18-90h (found on implant surface and on synovial tissue) >> planktonic 
              • explains why aspiration is only 17% sensitive
            • Mean duration of culture incubation between 7-21 days
  • Prophylaxis
    • antibiotic prophylaxis
      • administered within 30 minutes of incision
      • continued for 24 hours postoperatively
      • clindamycin for C. acnes
    • hair removal by electric clippers
    • preparation of the surgical site
Classification
  • Time of onset
    • acute infection
      • infection <3-6 weeks from surgery
        • CDC definition < 90 days from date of joint replacement
      • biology
        • usually confined to joint space
        • no invasion into prosthetic-bone interface
        • less likely for biofilm production
    • chronic infection
      • infection >3-6 weeks from surgery
        • CDC definition > 90 days from date of joint replacement
      • biology
        • biofilm created by all bacteria forms on implant within four weeks
          • composition
            • 15% cells and 85% polysaccharide layer (glycocalyx) 
              • glycocalyx allows biofilm to adhere to prosthesis and protect bacteria from host immune system
          • consequence
            • no method exists to safely remove biofilm and eradication is difficult
            • prosthetic explant indicated for infection >4 weeks due to biofilm production
          • infection has invaded prosthetic-bone interface
  • Source of infection
    • direct invasion
      • sinus tract into joint capsule or wound dehiscence
    • hematogenous infection
      • infection in a longstanding infection-free joint secondary to another infection (eg. dental work, infected gallbladder)
Presentation
  • History
    • may have had a systemic illness or skin penetration
  • Symptoms
    • common symptoms
      • persistent shoulder pain (most common)
      • persistent draining sinus (second most common)
      • systemic symptoms of infection (fevers, chills, night sweats)
      • stiffness
      • infection with C. acnes does not usually cause swelling, erythema, fever or purulent discharge
  • Physical exam
    • inspection
      • sinus tract to joint is diagnostic
    • motion
      • limited by pain and edema
Imaging
  • Radiographs
    • essential to exclude other causes
    • findings 
      • normal with early infection
      • osteopenia
      • periprosthetic lucencies
      • pseudosubluxation of the humeral head
      • effusion
      • endosteal scalloping
      • bony resorption
  • Bone scans
    • not routinely obtained as their efficacy has not been demonstrated
  • Ultrasound
    • findings
      • helpful to identify loculated fluid collections away from the glenohumeral joint
  • MRI
    • findings
      • helpful to identify loculated fluid collections away from the glenohumeral joint
  • Positron emission tomography (PET)
    • indication
      • useful adjunct in screening
    • sensitivity and specificity
      • 98% sensitivity and 98% specificity
Studies
  • Labs
    • serology 
      • WBC
        • physiology 
          • not specific or sensitive
          • may be normal in C. acnes infection
    • ESR and CRP 
      • have not demonstrated sufficient sensitivity or specificity to suggest PJI
      • CRP
        • physiology
          • peaks 2-3 days after surgery
          • returns to normal at 14-21 days
          • may be normal in C. acnes infection
      • ESR 
        •  physiology   
          •  peaks 5-7 days after surgery 
          • returns to normal 90 days (3 months)
          • may be normal in C. acnes 
    • alpha-defensin is investigational
  • Joint aspiration
    • no universal guidelines on when to aspirate
    • should be considered in all cases of deep infection
      • lab order request 
        • cell count and differential
          • WBC > 50,000 (500 cells/uL) 
        • crystals
          • presence does not exclude an infectious process
        • gram stain
          • may be negative in cases of infection
          • positive in approximately in 75% of cases
          • cultures and specificity  
            • synovial tissue cultures are the gold standard
            • positive in approximately 80% of cases
            • hold cultures for 14-28 days to isolate C. acnes
            • cultures should be on aerobic, anaerobic, and broth media
            • at least 4 specimens should be obtained at surgery
            • fungal cultures held for 4 weeks
            • mycobacterial cultures held for 8 weeks
Treatment
  • Nonoperative
    • antibiotic suppression
      • indications
        • severely ill patients
        • those unwilling to undergo surgery
        • guided by culture results
        • consultation with infectious disease
      • antibiotic  
        • Penicillin is the antibiotic of choice for treatment of C.acnes 
      • outcomes 
        • failure rates of 60-75% 
  • Operative
    • irrigation and debridement with component retention
      • inidications
        • acute infections (<4 weeks)
    • single-stage revision
      • indications
        • uncommonly performed
        • identified low virulence organism with good antibiotic sensitivity
        • healthy patient and soft tissue
      • advantages
        • reduced hospital stay
        • reduced cost
        • reduced period of antibiotic administration
    • 2-stage implant exchange
      • indications
        • gold standard
        • medically fit for multiple procedures
        • unknown micro-organism
        • requires adequate bone stock
        • requires microbial eradication prior to second stage
    • resection arthroplasty
      • indications
        • medically complex patients
        • frail patients who are poor surgical candidates
        • insufficient bone stock
        • recalcitrant infection
      • outcomes
        • poor functional results, but pain relief in over 50% of cases
    • arthrodesis
      • indications
        • rarely performed as bone stock is often compromised
    • amputation 
      • indications
        • rarely performed and reserved for life-threatening infection
Techniques
  • Antibiotic suppression 
    • antibiotic 
      • Aspiration cultures may direct antibiotic 
      • Penicillin is most common for C. acnes
    • complication
      • inadequate clearance of organism
  • Irrigation and debridement and component retention
    • approach
      • delto-pectoral approach
    • instrumentation
      • mobile parts of the prosthesis may be exchanged especially in RSA (glenosphere, polyethylene liner and tray)
    • complications 
      • inadequate clearance of organism
    • outcomes
      • 50% failure rate
  • Single-stage revision
    • approach
      • delto-pectoral approach
    • debridement
      • debride all infected soft tissue and bone
    • instrumentation 
      • remove infected prosthesis and implant a new one 
      • consider replacement with RSA for re-implantation as soft tissue debridement may sacrifice rotator cuff
    • complications 
      • inadequate clearance of organism
    • outcomes
      • variable, as high as 90% success in some series
  • 2-stage implant exchange
    • approach
      • delto-pectoral approach
    • debridement
      • debride all infected soft tissues and bone
    • instrumentation
      • removal of implants and implantation of an antibiotic-impregnated cement spacer
        • permits local antibiotic delivery and induces formation of a pseudocapsule that can be mobilized with the cuff
        • benefits
          • maintains soft-tissue tension
          • decreases pain
          • improves functional status
          • allows patient to perform physical therapy
        • technique
          • mix antibiotics with PMMA and form cement by hand or with mold
          • humeral stem may be fabricated from Steinmann pin and chest tube
    • complications
      • recurrent infection
    • outcomes
      • some remain satisfied and elect to leave the spacer
      • variable 60%-90% success rate
  • Resection arthroplasty
    • approach
      • delto-pectoral
    • debridement
      • debride all infected soft tissue and bone
      • preservation of tuberosities is predictive for better results
    • instrumentation
      • all instrumentation is removed
    • complications
      • poor functional outcome likely
      • antero-superior subluxation of humerus if tuberosities and cuff removed
    • outcomes 
      • functional results are poor
      • pain relief is achieved in more than 50%
  • Arthrodesis 
    • approach
      • S-shaped incision beginning over the scapular spine, traversing anterior over the acromion, and extending down the anterolateral aspect of the arm
    • debridement
      • resect rotator cuff
      • bicep tenodesis
      • decorticate glenoid, humeral head, and undersurface of acromion
    • instrumentation
      • a 10-hole 4.5mm pelvic reconstruction plate is commonly used with a goal of 30-30-30
        • 30 degrees of abduction
        • 30 degrees of forward flexion
        • 30 degrees of internal rotation
      • compression screws placed across the glenohumeral joint
    • complication
      • infection
      • nonunion
      • malposition
      • prominant hardware
      • humeral shaft fracture
    • outcomes
      • improvement in pain with fusion
  • Amputation
    • approach
      • dependent on the level of amputation or shoulder disarticulation
    • debridement
      • removal of soft tissue and bone to desired level of resection
    • instrumentation
      • removal of all implants
    • complication
      • infection
      • neruomas
Complications
  • Failure to eradicate infection
  • Humerus or glenoid fracture
  • Poor bone stock
 

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