Management When Osseous Infection Cannot Be Excluded
When bone infection cannot be definitively excluded, obtain MRI imaging immediately, and if MRI is positive or unavailable, proceed to bone biopsy for histopathology and culture to guide definitive antibiotic therapy. 1
Diagnostic Algorithm
Initial Imaging Strategy
Obtain plain radiographs first in all cases where bone infection is suspected, as this establishes baseline osseous anatomy and may reveal characteristic changes of osteomyelitis (cortical erosion, periosteal reaction, mixed lucency and sclerosis). 1
If plain radiographs are negative or equivocal, proceed immediately to MRI, which is the most accurate imaging modality for diagnosing osteomyelitis with high sensitivity and specificity. 1
A negative MRI effectively rules out osteomyelitis, defined as maintained intramedullary fat signal intensity and intact cortical signal integrity, allowing you to avoid bone biopsy and focus on soft tissue infection treatment. 1
When MRI Shows Positive or Equivocal Findings
If MRI demonstrates findings consistent with osteomyelitis (low T1 signal, high fluid-sensitive signal), the next step depends on whether an ulcer or sinus tract is present. 1
With an associated ulcer or sinus tract, obtain deep tissue cultures from the debrided wound base via curettage or biopsy—avoid superficial swabs as they yield contaminating organisms rather than true pathogens. 1, 2, 3
Without an ulcer or sinus tract, proceed to percutaneous image-guided bone biopsy under fluoroscopic or CT guidance to obtain specimens for both culture and histopathology. 1
The Gold Standard for Diagnosis
Definitive diagnosis requires both histopathology showing inflammatory cells and osteonecrosis PLUS positive bone cultures from aseptically obtained specimens. 1
A probable diagnosis is acceptable when you have positive results on a combination of tests: probe-to-bone test (in high-risk patients), elevated inflammatory markers (especially ESR), and positive imaging findings. 1
Empirical Treatment While Awaiting Confirmation
When to Start Antibiotics Before Definitive Diagnosis
In systemically ill patients with suspected osteomyelitis, initiate empirical broad-spectrum antibiotics immediately while pursuing diagnostic workup—do not delay treatment for culture results in severe cases. 4
For empirical coverage, use vancomycin combined with either a broad-spectrum cephalosporin (ceftriaxone, ceftazidime, or cefepime) or ciprofloxacin, which provides susceptibility rates of 93-96% for common osteomyelitis pathogens. 4
If the patient is clinically stable without systemic toxicity, withhold antibiotics for 2-4 days before obtaining bone cultures to maximize microbiological yield. 1
Critical Timing Considerations
For fracture-related infections manifesting within 3 weeks of fixation, debridement with implant retention (DAIR) achieves success rates >90%, but this drops to 51-67% if performed more than 10 weeks post-fixation due to biofilm maturation. 1
Treat soft tissue infection for 2 weeks first if initial radiographs are negative, then repeat plain films 2-4 weeks later if suspicion persists—this allows time for radiographic changes to develop. 1
Surgical Management Principles
When Surgery Is Required
Surgical debridement is the cornerstone of treatment for confirmed or highly suspected chronic osteomyelitis, as antibiotics alone cannot eradicate infection in the presence of necrotic bone and mature biofilm. 1, 5
Obtain intraoperative bone specimens during debridement for both histopathology and culture—send at least 2-3 specimens if possible, with one for culture and another for histological analysis. 1
For stage IV pressure injuries with suspected pelvic osteomyelitis, antibiotic therapy is only recommended post-operatively if the patient undergoes both adequate debridement AND flap reconstruction—medical therapy alone yields poor outcomes. 1
Implant Management in Fracture-Related Infection
Fracture stability is crucial for both bone consolidation and infection eradication, so the decision to retain or remove hardware depends on: stability of the construct, ability to perform adequate debridement, time interval since fixation, and soft tissue viability. 1
Intramedullary nails have higher DAIR failure rates than plate osteosynthesis because the intramedullary canal cannot be adequately debrided with the implant in place. 1
Antibiotic Duration After Surgical Intervention
Following adequate debridement and flap reconstruction, treat with antibiotics for 4-6 weeks, though shorter courses (2-4 weeks) may be appropriate for infections limited to cortical bone. 1, 5
Without surgical debridement of infected bone, antibiotic treatment must be prolonged for at least 4-6 weeks and often serves only as suppressive therapy rather than curative treatment. 5
Common Pitfalls to Avoid
Never rely on soft tissue or sinus tract cultures to guide antibiotic selection for osteomyelitis—these specimens do not accurately reflect bone culture results and frequently yield colonizing organisms. 1
Do not use wound swabs from undebrided ulcers, as they are contaminated with colonizing organisms rather than true pathogens causing bone infection. 2, 3
Avoid delaying bone biopsy in uncertain cases, especially when the infection has failed to respond to initial empirical therapy or when determining antibiotic susceptibilities is crucial for treatment planning. 1
Do not assume all exposed bone represents osteomyelitis—in stage IV pressure injuries, only 17-58% actually have bone infection, with many showing only pressure-related changes like fibrosis and reactive bone formation. 1