• Overview
    • wound and hardware infection can be a critical development in determining patient outcome
  • Epidemiology
    • incidence
      • up to16% infection rate following traumatic fracture
    • risk factors
      • host immunocompetency
      • extremes of age
      • diabetes
      • obesity
      • alcohol or tobacco abuse
      • steroid use
      • malnutrition
      • medications
      • previous radiation
      • vascular insufficiency
  • Pathophysiology
    • mechanisms
      • seeding
        • disruption of soft tissue envelope, blood vessels, and periosteum allow bacteria to avoid host defenses
        • direct seeding of implant and/or anatomical structure
        • hematogenous seeding
      • biofilm formation
        • dependent on exopolysaccharide glycocalyx
  • History
    • history of trauma must be detailed
      • extent of soft tissue injury
      • extent of bony injury
      • previous or current hardware
      • previous or current surgery at the same site
      • history of previous skin or deep infections
  • Symptoms
    • pain at previous fracture site
      • may indicate infected non-union
    • fevers, chills, and night sweats may be present
  • Physical exam
    • inspection
      • erythema, drainage, or purulence
      • tenderness
    • motion
      • gross motion at fracture site is suggestive of non-union
  • Radiographs
    • recommended views
      • biplanar images of afflicted area
      • 45 degree orthogonal views can also be obtained to evaluate for union
    • findings
      • acute infection
        • radiographs may be normal
      • sub-acute and chronic infections
        • peri-implant lucency can be seen
        • involucrum
          • reactive bone surrounding active infection
        • sequestrum
          • retained nidus of infected necrotic bone
  • CT
    • indications
      • pre-operative planning
  • MRI
    • indications
      • useful adjunct for diagnosis and delineating extent of disease
      • to assess soft-tissue masses and fluid collections
    • sensitivity and specificity
      • 98% sensitive
      • 78% specific
  • WBC-labeled scans
    • can help determine infection from other similar appearing etiologies
  • Labs
    • WBC
      • may be normal in chronic or indolent infections
    • erythrocyte sedimentation rate
      • may remain elevated for months following initial injury or surgery in absence of infection
    • C-reactive protein
      • most predictive for postoperative infection in the first week after fracture fixation 
      • should decrease from a plateau after postoperative day 2 (after fixation of fractures)
        • will increase further or fail to decrease if a hematoma or infection is present
  • Cultures
    • in-office cultures swabs or aspirations of wounds or sinus tracts are unreliable
    • intraoperative deep cultures are most reliable method of isolated causative organisms
      • multiple specimens from varying locations should be obtained
  • Nonoperative
    • chronic suppression with antibiotics
      • indications
        • risk of surgical treatment outweighs the benefit to the host
          • immunosuppressed, elderly, etc.
        • presence of an infected but incompletely healed fracture following internal fixation
      • technique
        • ESR and CRP levels used to assess adequacy of treatment
      • outcomes
        • 32% rate of chronic infected nonunion persisting or worsening despite suppression
  • Operative
    • surgical debridement
      • indications
        • any active infection
      • technique
        • hardware should be maintained if stability at risk with removal
        • low-pressure irrigation with normal saline may be superior to other methods of irrigation
        • thorough identification and debridement of infection key to success
        • deep bony specimens should be obtained for culture as well as biopsy
      • outcomes
        • 71% success seen with debridement and antibiotics for early acute postoperative infection 
          • Risk factors for failure include intramedullary nail and open fracture

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Questions (3)

(OBQ13.5) Which of the following processes relies on an exopolysaccharide glycocalyx? Review Topic


Osteoclast differentiation




Biofilm creation




Metastatic bone disease




Endochondral bone formation




Intramembranous bone formation



Select Answer to see Preferred Response


Exopolysaccharide glycocalyx allows bacteria to adhere to orthopaedic implants and elude antimicrobial therapies through the creation of biofilms.

Biofilms are defined as a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface. Biofilm production usually occurs within 4 weeks, and is extraordinarily hard to eradicate with antibiotic therapy alone. In the setting of a chronic infection of an orthopaedic implant (>4 weeks), explantation of the implant followed by antimicrobial therapy is the most reliable method of curing the infection.

Nguyen et al. reviewed 21 patients who underwent revision arthroplasty with negative intraoperative cultures. After standard cultures were obtained (all negative), the implants underwent an ultrasound protocol to theoretically disrupt the biofilm. 1 of the 21 implants grew coag-negative Staph after the bath.

Fux et al. reviewed biofilms with respect to orthopaedic and non-orthopaedic conditions. They discussed how aspirations are often falsely negative possibly because the microorganisms persist only within a biofilm on the synovia but not in planktonic form.

Illustration A and the video provided show the process of biofilm formation.

Incorrect Answers:
Answer 1: Osteoclast differentiation relies on the RANK-RANKL signaling pathway.
Answer 3: Osteolytic bone lesions are also caused by the RANK-RANKL pathway.
Answer 4: Endochondral bone formation occurs when osteoblasts lay down bone on a cartilaginous framework. Exopolysaccharide glycocalyx does not play a role in this.
Answer 5: Intramembranous bone formation does not involve exopolysaccharide glycocalyx.


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Question COMMENTS (1)

(OBQ05.133) After open reduction and internal fixation of long bone fractures, at what time period should C-reactive protein start to decrease? Review Topic


24 hours




48 hours




96 hours




7 days




12 days



Select Answer to see Preferred Response


C-reactive protein (CRP) should peak by 48 hours after surgical fixation of bony orthopedic injuries, and decrease thereafter. This is important to recognize, as an increasing CRP after 48 hours is predictive for postoperative infection, and is more predictive in the first postoperative week than local erythema, persistent serous drainage, and increasing serial ESR.

The first referenced study by Waleczek et al noted that CRP was the earliest sign of developing infection and that clinical diagnosis, ultrasound, and WBC counts all lagged significantly behind CRP as a diagnostic tool. They report that latency to the clinical diagnosis based on clinical signs, ultrasound, WBC in blood and wound drainage was up to 14 days, while there was no patient with CRP increasing after day 2 without an infection.

The second referenced article by de Zwart et al noted an increased sensitivity and specificity of CRP as compared to ESR in the scenario of a clinically suspected infection. They advocate for determination of two CRP-levels with a short interval to screen for a clinically suspected infection.

Furthermore, Mok et al found that CRP showed an exponential decrease with a half-life of 2.6 days in postoperative spine patients. They found that CRP is a reliable test in the early postoperative period compared with ESR.

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(OBQ04.122) Which of the following is the most sensitive parameter to detect the increased inflammatory response seen with both postoperative infection and the use of instrumentation in spinal surgery? Review Topic


Patient temperature




WBC count




Erythrocyte sedimentation rate




C-reactive protein




Rheumatoid Factor



Select Answer to see Preferred Response


The most sensitive parameter to detect inflammation elicited by implants and infection is the C-reactive protein (CRP).

CRP is an acute phase reactant that increases sharply immediately after surgery within 6 hours after tissue damage. CRP then peaks 2-3 days later and returns to normal levels 5-21 days after the inciting event. In contrast, ESR reaches its peak on days 4-11, then remains elevated for a prolonged period of time.

Takahashi et al performed a Level 3 study of patients who had undergone spinal surgery with and without instrumentation, with a primary outcome of infection. They concluded that renewed elevation of C-reactive protein, white blood cell count, and body temperature after postoperative days 4 to 7 may be a key indicator of postoperative infection.

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