osteomyelitis Flashcards
what is osteomyelitis?
An infection of bone
most cases are acute and bacterial in origin
where is osteomyelitis most commonly found in adults?
the vertebrae
what are the common causative organisms of osteomyelitis?
S. aureus (most common)
Streptococci,
Enterobacteur spp.,
H. Influnzae,
P. aeruginosa (especially in intravenous drug users),
Salmonella spp. (especially in patients with sickle cell disease)
how does an organism enter the body to cause osteomyelitis?
haematogenous spread
direct inoculation e.g open fracture/ penetrating injury
direct spread from nearby infection
what is the pathophysiology of osteomyelitis?
bacteria enters bone tissue and express adhesins to bid to host tissue proteins
produce polysaccharide extracellular matrix so pathogens can propagate, spread and seed further in the tissue
what is a sequestrum?
in chronic cases of osteomyelitis, infection can lead to devascularisation of affected bone = necrosis and resorption of surrounding bone.
This leads to a floating piece of dead bone, termed a sequestrum
this acts like a reservoir for infection and isn’t penetrated by antibiotics, as its avascular
what is an involucrum?
An involucrum can also form, following the sequestrum formation, whereby the region becomes encased in a thick sheath of periosteal new bone.
what are the risk factors for osteomyelitis?
- DM
- immunosuppresion
- alcohol excess
- IV drug use
what are the clinical features of osteomyelitis?
- severe, constant pain in affected region
- low grade pyrexia
- tender site
- overlying swelling and erythema
- unable to weight bear
- examine for potential sources of infection e.g needle tracks, cellulitis areas, wounds or stigmata of concurrent infection
NB: in patients with diabetic foot, pain may be absent due to peripheral neuropathy
what are the differentials for osteomyelitis?
septic arthiritis
traumatic injuries
primary/ secondary bone tumours
what is potts disease?
an infection of the vertebral body and intervertebral disc by Mycobacterium tuberculosis.
Patients will present with back pain +/- neurological features, with associated low grade fever and non-specific infective symptoms.
will usually start in the intervertebral disk
what investigations are done into osteomyelitis?
- routine bloods
- blood cultures
- plain film radiographs, however they have poor accuracy for osteomyelitis.
- definitive diagnosis is via MRI
- gold standard is culture from bone biopsy at dibridement
what are the potential radiographic features of osteomyelitis?
- osteopaenia
- periosteal thickening
- endosteal scalloping
- focal cortical bone loss
how is osteomyelitis managed?
- long term IV antibiotics (>4 weeks)
- if patient deteriorates or limb deteriorates/evidence of progressive bone destruction, may need surgery to prevent chronic osteomyelitis. This involves curettage of the area.
what are the complications of osteomyelitis?
- sepsis if managed poorly
- children may develop growth disturbance as a result of premature physeal closure
- amputation is rarely needed
- recurrence of infection, often with premature cessation of antibiotics
- chronic osteomyelitis in the immunocompromised/ under treated patients or with virulent/ resistant organisms
