Osteomyelitis — infection of the bone — is one of the most serious and limb-threatening complications in diabetic foot care. Among people with diabetes who develop a foot ulcer, bone infection occurs in approximately 12–20% of cases; the proportion rises to nearly half of all patients presenting with severe foot infections. Left unrecognized or inadequately treated, osteomyelitis is a leading driver of lower-extremity amputation in people with diabetes. A growing body of evidence is reshaping how clinicians diagnose and manage this condition, moving toward a more individualized, evidence-based approach.
Recognizing Osteomyelitis at the Bedside
Clinical assessment remains the essential first step. The probe-to-bone (PTB) test — in which a sterile metal probe is passed through a wound to determine whether bone can be directly contacted — is the most practical point-of-care diagnostic tool available. A systematic review by Lam and colleagues, published in Clinical Infectious Diseases (2016), pooled data from seven studies and found the PTB test has a pooled sensitivity of 0.87 and a specificity of 0.83. A positive result substantially raises the probability of osteomyelitis, particularly in patients with deep, non-healing ulcers.
Other clinical features that heighten suspicion include visible or palpable bone within the wound base, a “sausage toe” deformity from phalangeal involvement, ulcers larger than 2 cm² or deeper than 3 mm, and wounds that have persisted beyond one month despite adequate offloading and wound care. No single clinical finding is definitive on its own — the overall picture, including systemic signs of infection, must inform clinical judgment.
Imaging: MRI as the Reference Standard
Plain radiographs are typically obtained first but are insensitive to early osteomyelitis: cortical bone loss may not appear on X-ray until 30–50% of bone mineral has been destroyed. Magnetic resonance imaging (MRI) has emerged as the reference standard for imaging-based diagnosis. A systematic review and meta-analysis published in Diabetes Care (Lauri et al., 2017) compared MRI, white blood cell (WBC) scintigraphy, and fluorodeoxyglucose positron emission tomography (FDG-PET) across multiple studies. MRI demonstrated superior sensitivity for detecting osteomyelitis and simultaneously delineates soft-tissue involvement and vascular anatomy relevant to surgical planning.
Emerging techniques — including diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE) sequences — may further improve specificity and help resolve equivocal findings. For patients in whom MRI is contraindicated or unavailable, WBC scintigraphy and FDG-PET are validated alternatives with reasonable diagnostic accuracy.
Bone Biopsy and Microbiological Diagnosis
The definitive diagnosis of osteomyelitis requires histopathological confirmation and/or a positive bone culture. The 2023 joint guidelines of the International Working Group on the Diabetic Foot and the Infectious Diseases Society of America (IWGDF/IDSA 2023), authored by Senneville and colleagues and published in Diabetes/Metabolism Research and Reviews (2024), explicitly state that bone specimens — rather than superficial swabs or soft-tissue samples — should be used to identify the causative pathogen. Bone biopsy is far less susceptible to wound-surface contamination, which commonly yields misleading polymicrobial results from swab cultures.
Serum biomarkers — including erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and white blood cell count — provide supportive evidence. A 2024 meta-analysis by Ansert and colleagues in Wound Repair and Regeneration found elevated ESR to be the most reliable individual biomarker for diabetic foot osteomyelitis; however, no single marker is sufficient to confirm or exclude bone infection independently.
Treatment: Surgery, Antibiotics, or Both?
For decades, surgical resection of infected bone was regarded as necessary for cure. Contemporary evidence has qualified that view. The IWGDF/IDSA 2023 guidelines acknowledge that a conservative, non-surgical approach — prolonged systemic antibiotic therapy without bone resection — may be appropriate for a well-defined subset of patients: primarily those with forefoot osteomyelitis, without peripheral arterial disease, and without surgically uncontrollable infection. Cohort studies and meta-analyses have demonstrated comparable long-term remission rates between surgical and antibiotic-only strategies in this group, though randomized controlled trial data remain limited.
When surgery is indicated — typically for mid- or hindfoot involvement, progressive bone destruction, gangrene, or uncontrolled sepsis — prompt intervention is essential. The IWGDF/IDSA guidelines advise surgical decompression and drainage within 24 hours for wounds with purulent accumulations. Antibiotic therapy for confirmed diabetic foot osteomyelitis typically continues for four to six weeks, guided by bone culture and susceptibility results, with clinical reassessment at regular milestones.
Conclusion
Osteomyelitis in the diabetic foot is a clinically complex condition that demands an integrated diagnostic approach — combining bedside clinical assessment, appropriate imaging, and microbiologically guided tissue sampling. The 2023 IWGDF/IDSA guidelines provide the most current evidence-based framework for management, supporting individualized decision-making rather than a uniform surgical mandate. Early and accurate diagnosis, targeted antimicrobial therapy, and multidisciplinary care offer the best opportunity to eradicate infection, preserve the foot, and prevent limb loss.
References
- Senneville E, et al. IWGDF/IDSA guidelines on the diagnosis and treatment of diabetes-related foot infections (IWGDF/IDSA 2023). Diabetes/Metabolism Research and Reviews. 2024;40(3):e3687. doi:10.1002/dmrr.3687
- Lam K, van Asten SA, Nguyen T, et al. Diagnostic accuracy of probe to bone to detect osteomyelitis in the diabetic foot: a systematic review. Clinical Infectious Diseases. 2016;63(7):944–948. doi:10.1093/cid/ciw445
- Lauri C, Tamminga M, Glaudemans AWJM, et al. Detection of osteomyelitis in the diabetic foot by imaging techniques: a systematic review and meta-analysis comparing MRI, white blood cell scintigraphy, and FDG-PET. Diabetes Care. 2017;40(8):1111–1120. doi:10.2337/dc17-0532
- Ansert E, et al. Update of biomarkers to diagnose diabetic foot osteomyelitis: a meta-analysis and systematic review. Wound Repair and Regeneration. 2024. doi:10.1111/wrr.13174
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