Diabetic-foot osteomyelitis

Diabetic-foot osteomyelitis usually begins beneath an ulcer and therefore must be interpreted as one part of a limb system: infection, perfusion, neuropathy, pressure, deformity, metabolic health and self-care capacity. Ask when the ulcer started, whether it probes deeply, previous episodes and organisms, all antibiotic exposure, offloading, footwear and revascularisation. Establish glycaemic therapy, renal function, smoking, visual or manual barriers, social support and previous amputations. New malaise or glucose instability can be the earliest systemic signal.

Remove dressings and inspect both feet. Record ulcer site, dimensions, depth, undermining, exudate, odour, surrounding erythema, callus, necrosis and exposed tendon, joint or bone. After cleansing and debridement, gentle sterile probe-to-bone testing can alter probability but is not definitive. Map fluctuance and tendon-sheath spread. Compare warmth and architecture for Charcot change. Test monofilament or equivalent protective sensation and motor deformity, then document pulses, handheld Doppler signals, capillary refill and tissue loss rather than labelling perfusion from palpation alone.

Classify infection as mild, moderate or severe using systemic and anatomical findings. Severe infection includes systemic inflammatory response and needs hospital care, immediate sepsis assessment and intravenous treatment. Moderate infection extends more than two centimetres around the ulcer or reaches deeper structures such as abscess, bone, joint or fascia without systemic inflammatory response. This distinction drives urgency and route but does not substitute for judgement: renal failure, severe ischaemia, inability to offload or rapidly progressing necrosis can justify admission even without classic systemic criteria.

Obtain FBC, CRP, renal and liver profiles, glucose and ketones where indicated, and blood cultures in systemic illness. Normal markers cannot exclude a local chronic bone focus. Plain radiographs are first imaging and may show cortical erosion, periosteal reaction, sequestrum, gas, foreign body, deformity or Charcot fragmentation, but early disease can be occult. NICE advises MRI when osteomyelitis remains suspected but initial radiography does not confirm it. MRI maps marrow and collections; recent surgery and Charcot inflammation reduce specificity and require musculoskeletal radiology interpretation.

Microbiology quality determines whether narrowing is safe. Cleanse and debride before taking a deep tissue sample; do not rely on a superficial swab from colonised exudate. Percutaneous or operative bone culture with histology is most informative when imaging is equivocal, prior therapy has failed or prolonged treatment is contemplated. Plan any antibiotic-free interval with the multidisciplinary infection team and never impose it on sepsis or rapidly spreading infection. Send separately labelled samples from distinct sites at surgery, because different ulcers and compartments need not share an organism.

Source control includes drainage, removal of necrotic tissue and bone, pressure relief and perfusion. Urgent surgery is required for abscess, necrotising spread, wet gangrene, extensive non-viability or uncontrolled sepsis. Limited bone resection may preserve a functional foot when margins and mechanics are acceptable. Vascular and surgical teams coordinate the sequence of drainage and revascularisation according to sepsis and anatomy. Every plan includes effective offloading, wound care and footwear modification; continuing to load the same pressure point defeats antimicrobial success.

NICE antibiotic selection reflects severity, prior microbiology, allergy, renal function and local resistance. Give oral treatment first-line if the person can absorb it and severity does not require intravenous treatment. Severe infection receives intravenous therapy for at least 48 hours until stabilised, with review at 48 hours and oral switch where possible. For moderate or severe infection, options include flucloxacillin with or without gentamicin and/or metronidazole, or co-amoxiclav with or without gentamicin, but the exact combination depends on clinical and microbiological context.

NICE states that course length is a minimum of seven days and can extend to six weeks for osteomyelitis, using oral antibiotics for prolonged treatment. Duration is not automatically six weeks: complete resection of infected bone, residual margins, culture, perfusion and response change the decision. Review regularly rather than treating persistent colour alone. Follow ulcer dimensions, wound depth, systemic symptoms, CRP where useful, renal and liver safety, glucose, perfusion and adherence. Prevention requires daily inspection, rapid reporting, callus care, podiatry, offloading and surveillance of the contralateral foot.