Musculoskeletal

Osteomyelitis

Osteomyelitis is infection of bone acquired through the bloodstream, from adjacent tissue or by direct inoculation. It can progress to abscess, dead bone, sinus formation, vertebral neurological compromise or limb-threatening diabetic foot disease, so early cultures, imaging, specialist antibiotics and source control are central.

In a nutshell

Osteomyelitis is bone infection acquired haematogenously, by contiguous spread or by direct inoculation. Suspect it with focal bone pain, a chronic or deep diabetic foot wound, persistent spinal pain and fever, or an infected implant. Obtain blood and deep samples when safe, use MRI when initial imaging is non-diagnostic, give culture-directed antibiotics with microbiology advice and achieve source control for abscess, necrotic bone, infected hardware or ischaemic diabetic foot disease.

Classic presentation

A child with fever and focal long-bone pain, an adult with persistent back pain and fever, or a person with diabetes and a deep chronic foot ulcer. Remember that early X-rays and inflammatory markers can be normal.

Key points

The route is haematogenous, contiguous or direct inoculation; Staphylococcus aureus is common but treatment depends on site, severity and cultures.
MRI is usually the most useful early imaging test, but the clinical context and alternative diagnoses matter.
Obtain blood cultures and deep tissue, bone or aspirate samples before antibiotics when safe; do not let sampling delay treatment of sepsis or neurological compromise.
NICE diabetic-foot guidance says suspect osteomyelitis with a local, deep or chronic wound, and use MRI when the initial X-ray does not confirm it.
A superficial swab may reflect colonisation; use bone or deep debrided-wound sampling, with a deep swab only when an appropriate deeper sample cannot be obtained in a diabetic foot.
Narrow antibiotics with microbiology advice, review IV-to-oral suitability and course length, and follow BNF and local policy for agents and doses.
Abscess, sequestrum, infected prosthesis, spinal epidural infection, ischaemia and failure of treatment need urgent source-control or specialist escalation.

First-line investigation

Focused source and neurological assessment, blood cultures and inflammatory or safety blood tests, followed by site-appropriate radiographs and MRI when needed, with deep microbiology.

Management

Stabilise and recognise limb or life threats

Use ABCDE and urgent senior input for sepsis, shock, neurological deficit, spinal cord or cauda equina symptoms, limb ischaemia, gangrene or deep diabetic-foot infection.^5,6,7

Culture and image the suspected site

Obtain blood and deep tissue, bone or aspirate samples before treatment when safe; use radiographs first where appropriate and MRI when disease remains suspected or is deep or vertebral.^5,6,3

Start and narrow antimicrobial treatment

Use local microbiology and BNF guidance for empiric treatment, then narrow promptly to the culture and susceptibility results, reviewing IV-to-oral suitability, toxicity and duration.^5,7,3

Achieve source control

Drain abscesses, debride necrotic bone or soft tissue, address infected hardware, offload diabetic ulcers and restore perfusion through the appropriate multidisciplinary pathway.^1,5,6,4

Monitor response and prevent relapse

Review clinical response, wound, neurological function, cultures, inflammatory markers, organ function and antibiotic toxicity; investigate recurrence or non-response for inadequate source control or a resistant or atypical organism.^5,6,7

Exam traps

A normal early X-ray, CRP, ESR or probe-to-bone test does not exclude diabetic-foot osteomyelitis.
Persistent back pain with fever or neurological signs is not simple mechanical back pain; arrange urgent MRI and spinal or microbiology assessment.
Do not delay antibiotics in sepsis, shock or neurological compromise for a biopsy.
A superficial swab is not equivalent to a bone or deep tissue sample.
Antibiotics alone may fail when there is an abscess, sequestrum, infected hardware or poor perfusion.
Diabetic-foot infection with deep bone infection, ischaemia, gangrene or sepsis requires immediate acute referral and multidisciplinary foot-care involvement.

Illustrations

Brodie abscess on MRIA coronal STIR MRI of the distal tibia showing a focal Brodie abscess with surrounding bone-marrow oedema in subacute osteomyelitis. Confirm that the lesion is legible and diagnostically teachable in the separate image campaign.Jto410, Wikimedia Commons · CC-BY-SA-3.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.