Osteomyelitis (MSK) Flashcards
Define osteomyelitis.
Inflammatory condition of bone caused by an infective organism
What organisms commonly cause osteomyelitis?
- most commonly Staphylococcus aureus
- Salmonella species more common in sudden cardiac arrest patients
- infants: Group B Streptococci, E. coli, Candida albicans
- children: GAS, Streptococcus pneumoniae, H. influenzae, Pseudomonas, Kingella kingae
What are the two classifications of osteomyelitis?
- haematogenous osteomyelitis - results from bacteraemia and usually monomicrobial –> most common in children
- non-haematogenous osteomyelitis - results from contagious spread of infection from adjacent soft tissues to the bone, or from direct injury/trauma to the bone and usually polymicrobial –> most common in adults
What are some risk factors for haematogenous osteomyelitis? (4)
- sickle cell anaemia
- IV drug use
- immunosuppression
- infective endocarditis
What are some risk factors for non-haematogenous osteomyelitis? (3)
- diabetic foot ulcers/pressure sores
- DM
- peripheral arterial disease
How many bones does osteomyelitis usually involve?
A single bone
What is the basic pathophysiology of osteomyelitis?
Bacteria –> bloodstream –> bone (affects periosteum –> bursts –> abscess)
Later: cytokines induce bone resorption –> replacement with fibrous tissue –> new bone formation around necrotic one (involucrum - chronic)
What happens in acute osteomyelitis?
- immune system destroys all invading bacteria
- if viable bone then osteoclasts + osteoblasts begin to repair damage
What happens in chronic osteomyelitis?
- affected bone becomes necrotic + separates from healthy bone (sequestrum)
- osteoblasts may form new bone that wraps the sequestrum in place (involucrum)
What are the clinical features of osteomyelitis? (5)
- limp or reluctance to weight bear - common in children
- non-specific pain at site of infection
- malaise, fatigue, fever, chills
- inflammation, tenderness, erythema, swelling
- Hx preceding skin lesion, sore throat, trauma, operation
What might we see on examination of osteomyelitis? (8)
- localised erythema
- tenderness or spasm
- swelling
- warmth
- painful/limited movement of affected limb
- seropurulent discharge from wound/ulcer
- reduced sensation in diabetic foot
- previous scars, flaps or fractures
How might native vertebral osteomyelitis present?
Local back pain with systemic symptoms
When should you suspect acute osteomyelitis?
Unwell child with a limp OR in an immunocompromised patient
When should you suspect chronic osteomyelitis?
Adults with history of open fracture, previous orthopaedic surgery or discharging sinus
When should you suspect native vertebral osteomyelitis?
Patient with new back pain and systemic symptoms
What are some risk factors for osteomyelitis? (7)
- penetrating injury
- IVDU, haemodialysis (contaminated needles)
- diabetes (–> foot ulcers)
- HIV / immunocompromised
- recent surgery e.g. dental extraction of infected tooth
- distant or local infection e.g. cellulitis, RTI, Varicella
- SCA, RA, CKD
What are the first-line investigations for osteomyelitis? (4)
- FBC - high WCC
- ESR & CRP - elevated
- blood culture - before Abx
- plain XR of affected area
What does XR show in osteomyelitis?
- periosteal thickening, osteopenia, soft tissue swelling, intramedullary scalloping, cavities
- ‘fallen leaf sign’ - when a piece of endosteal sequestrum has detached and fallen into medullary canal
- acute - may initially be normal, osteopenia appears after 6-7 days
What is the most definitive imaging modality for osteomyelitis?
Bone MRI
What are the gold standard tests for osteomyelitis?
Bone sample + bone biopsy (balance invasiveness of test with need for accurate aetiological diagnosis)
What investigations are needed before starting Abx in osteomyelitis? (2)
- blood culture
- bone biopsy (if indicated)
What are some differential diagnoses for osteomyelitis? (9)
- septic arthritis (can co-exist)
- juvenile idiopathic arthritis
- transient synovitis (2-12y, moderate hip pain and limp)
- reactive arthritis
- slipped capital femoral epiphysis
- Legg-Calve-Perthe’s disease
- cellulitis
- necrotising fasciitis
- metastatic bone cancer
What is the management for osteomyelitis?
Abx therapy for 2-4 weeks - flucloxacillin (IV) + supportive care
Clindamycin if penicillin allergic
Cefazolin/cefuroxime/flucloxacillin if child
Vancomycin if MRSA
When do we do surgery for osteomyelitis?
- peripheral osteomyelitis - if limb deteriorates and dead bone is established
- vertebral osteomyelitis - progressive neurological deficits, deformity + spinal instability despite antimicrobial Rx
What do we do in chronic osteomyelitis?
Refer to specialist team, staging and assessment
What are some complications of osteomyelitis? (7)
- drug reactions
- infection recurrence
- fracture
- infection spread –> joints, skin, muscle, blood vessels
- neurological impairment secondary to abscess or bony collapse
- amputation
- growth disturbance in children
Describe the prognosis of osteomyelitis if diagnosed promptly and treated adequately.
For most patients with acute osteomyelitis, they will recover with no long-term complications
