Diagnostic Criteria for Chronic Osteomyelitis
Chronic osteomyelitis is diagnosed based on a combination of clinical, radiological, and microbiological findings, with bone biopsy and culture remaining the gold standard for definitive diagnosis. 1
Clinical Criteria
- Persistent bone pain and swelling
- Draining sinus tract (a hallmark sign of chronic infection)
- History of prior trauma, surgery, or inadequate treatment of acute infection
- Symptoms lasting >6 weeks (differentiating from acute osteomyelitis)
- Nocturnal pain of moderate intensity
- Fever (present in up to 45% of patients)
Radiological Criteria
Plain Radiographs
- Initial imaging modality, though sensitivity is low (54%) in early disease 1
- Characteristic findings:
- Bone sclerosis
- Areas of bone destruction
- Periosteal reaction
- Sequestrum (dead bone fragment)
- Involucrum (new bone formation)
- Cortical thickening
Advanced Imaging
MRI is the gold standard with >90% sensitivity and specificity 1
- Decreased T1-weighted bone marrow signal
- Increased signal on fluid-sensitive sequences
- Soft tissue and marrow edema
- Delineation of extent of disease
CT findings 2
- Periosteal reaction
- Trabecular coarsening
- Bone fragmentation
- Cortical erosions
- Fistulae
- Superior for detecting sequestrum
Nuclear Medicine Studies
Laboratory Criteria
- Elevated inflammatory markers:
- C-reactive protein (CRP)
- Erythrocyte sedimentation rate (ESR >27 mm/h)
- Procalcitonin
- Blood cultures (positive in hematogenous spread)
Microbiological Criteria
Diagnostic Algorithm
- Initial evaluation with plain radiographs
- Laboratory tests (CRP, ESR, blood cultures)
- MRI if diagnosis remains uncertain after initial tests
- Bone biopsy and culture for definitive diagnosis
Common Pitfalls
- Relying solely on radiographs for early diagnosis (changes may not appear until 3-6 weeks)
- Using swab cultures instead of bone/tissue specimens (higher contamination risk)
- Prior antibiotic use leading to false-negative cultures
- Misinterpreting bone scan results in patients with recent trauma or surgery
Treatment Approach
- Appropriate bone sampling for culture
- Targeted antibiotic therapy based on culture results
- Surgical debridement in chronic cases
- Extended antibiotic course (typically several weeks)
Despite appropriate treatment, chronic osteomyelitis has a high recurrence rate, requiring vigilant follow-up and sometimes repeated interventions 4.