Osteomyelitis — infection of bone — complicates a substantial share of diabetic foot ulcers and is one of the strongest drivers of lower-extremity amputation. It is also one of the hardest diagnoses in the diabetic foot to make with confidence, and one of the most inconsistently treated. Two questions dominate the clinical literature of the past decade: how do we know bone is actually infected, and once we know, how much antibiotic therapy is enough?
Making the Diagnosis: Bedside Findings, Imaging, and Bone
Diagnosis begins at the bedside. The probe-to-bone test — advancing a sterile blunt probe through the ulcer to detect hard, gritty bone — remains the most useful single clinical manoeuvre. A systematic review and meta-analysis by Lam and colleagues in Clinical Infectious Diseases pooled seven studies and found a sensitivity of 0.87 and specificity of 0.83. The authors emphasised that the test’s value depends heavily on pre-test probability: it reliably rules osteomyelitis in among high-risk patients (deep, chronic, or recurrent ulcers) and rules it out among low-risk patients, but performs less decisively in between.
Plain radiographs remain the appropriate first imaging study, though bone changes lag infection by roughly two to three weeks. MRI is more sensitive, but its added value in routine practice is debated. In a prospective Geneva cohort of 390 diabetic foot osteomyelitis episodes followed for a median of 2.9 years, Gariani and colleagues found that cases identified by MRI alone — without radiographic bone lesions — did not differ from radiograph-positive cases in antibiotic duration (28 versus 30 days), number of debridements, or recurrence rate (25% versus 28%). MRI cost roughly eight times more per study without altering management in that pathway.
Why Bone Sampling Matters
Bone biopsy for histopathology and culture remains the diagnostic reference standard, and it does more than confirm infection: it identifies the organism. Hockney and colleagues, writing in the Journal of Antimicrobial Chemotherapy, reviewed 152 patients with diabetic foot osteomyelitis and found that although bone or deep-tissue cultures were obtained in fewer than a third, those cultures changed antibiotic therapy in 87% of the patients who had them. Therapy was narrowed in 62% — important for reducing resistance and drug toxicity — while in 9% the empiric regimen had failed to cover the causative organism at all.
Bone sampling has limits. Elmarsafi and colleagues compared 70 matched pairs of bone histopathology and bone culture in patients with concurrent Charcot neuro-osteoarthropathy and found concordance of only 41%, with diagnostic accuracy near 50% for both methods. When Charcot changes are present, the usual reference standard becomes unreliable, and diagnosis should rest on the convergence of clinical, laboratory, and imaging findings.
How Long to Treat, and by Which Route
Historically, six weeks or more of antibiotic therapy was standard. That assumption has been directly tested. In a prospective randomised non-inferiority pilot trial published in Clinical Infectious Diseases, Gariani and colleagues randomised 93 patients with diabetic foot osteomyelitis, all of whom had undergone surgical debridement, to three or six weeks of systemic antibiotics. Remission occurred in 84% of the three-week arm versus 73% of the six-week arm, with a similar frequency of adverse events. The shorter course was statistically non-inferior. The trial was small and applies specifically to patients whose infected bone had been surgically removed, but it undercuts the reflex toward prolonged therapy.
Route of administration has undergone a similar re-examination. Kipp and colleagues reviewed 128 patients treated for residual osteomyelitis after diabetic foot amputation and found no significant difference in treatment success between oral and intravenous regimens, with a median time to healing of 3.17 months for oral versus 4.06 months for intravenous therapy. Highly bioavailable oral agents avoid the cost, line complications, and home-nursing burden of prolonged intravenous therapy.
Practice Has Not Kept Pace With Evidence
Uddin and colleagues reviewed 40 new cases of diabetic foot osteomyelitis across eight centres in England and Wales and documented substantial variation in antibiotic selection, single versus dual therapy, route, and duration — both between and within centres. Notably, 65% of patients were started on intravenous therapy, and 42.5% achieved quiescence with antibiotics alone without surgical intervention. Reviews of the 2023 IWGDF/IDSA guidance, which was informed by 149 studies, likewise stress that decisions about antibiotics versus surgery, agent, route, and duration require patient-specific reasoning within a multidisciplinary team rather than a fixed protocol.
Clinical Summary
The probe-to-bone test remains a high-yield bedside tool when interpreted against pre-test probability. Bone sampling, where feasible, meaningfully redirects antibiotic therapy and supports narrowing rather than escalation — except in the presence of Charcot changes, where its accuracy falls sharply. Following surgical debridement, three weeks of antibiotics appears non-inferior to six in randomised pilot data, and oral therapy appears comparable to intravenous therapy in appropriately selected patients. Real-world practice still varies widely from these findings, which is itself among the more actionable observations in the recent literature.
References
- Senneville É, Albalawi Z, van Asten SA, et al. IWGDF/IDSA Guidelines on the Diagnosis and Treatment of Diabetes-related Foot Infections (IWGDF/IDSA 2023). Diabetes/Metabolism Research and Reviews. 2023;40(3):e3687. doi:10.1002/dmrr.3687
- Lam K, van Asten SAV, Nguyen T, La Fontaine J, Lavery LA. 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
- Gariani K, Pham TT, Kressmann B, et al. Three Weeks Versus Six Weeks of Antibiotic Therapy for Diabetic Foot Osteomyelitis: A Prospective, Randomized, Noninferiority Pilot Trial. Clinical Infectious Diseases. 2021;73(7):e1539–e1545. doi:10.1093/cid/ciaa1758
- Hockney SM, Steker D, Bhasin A, Krueger KM, Williams J, Galvin S. Role of bone biopsy and deep tissue culture for antibiotic stewardship in diabetic foot osteomyelitis. Journal of Antimicrobial Chemotherapy. 2022;77(12):3482–3486. doi:10.1093/jac/dkac345
- Kipp JA, LeSavage LK, Evans JK, Denmeade TA, Blazek CD. Diabetic Osteomyelitis: Oral versus Intravenous Antibiotics at a Single Level 1 Academic Medical Trauma Center. Journal of Foot and Ankle Surgery. 2024;63(4):490–494. doi:10.1053/j.jfas.2024.03.003
- Gariani K, Lebowitz D, Kressmann B, Gariani J, Uçkay I. X-Ray Versus Magnetic Resonance Imaging in Diabetic Foot Osteomyelitis: A Clinical Comparison. Current Diabetes Reviews. 2021;17(3):373–377. doi:10.2174/1573399816999200729124134
- Elmarsafi T, Kumar A, Cooper PS, et al. Concordance Between Bone Pathology and Bone Culture for the Diagnosis of Osteomyelitis in the Presence of Charcot Neuro-Osteoarthropathy. Journal of Foot and Ankle Surgery. 2018;57(5):919–923. doi:10.1053/j.jfas.2018.03.016
- Uddin A, Russell DA, Game F, Santos D, Siddle HJ. Variation in Systemic Antibiotic Treatment for Diabetic Foot Osteomyelitis in England and Wales: A Multi-Centre Case Review. Journal of Clinical Medicine. 2024;13(11):3083. doi:10.3390/jcm13113083
- Nauriyal V, Byers K. Diabetic foot infections: Questions for an infectious disease consultant. Seminars in Vascular Surgery. 2025;38(1):85–93. doi:10.1053/j.semvascsurg.2025.01.009
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