Osteomyelitis profoma Flashcards
What is osteomyelitis?
Inflammation of bone or bone marrow, usually due to infection.
Difficult to treat as it can remain dormant for many years.
Epidemiology of osteomyelitis
Now uncommon due to awareness of bacterial spread & prevention.
Incidence higher in men than women (M: F of 3:1).
Incidence increases w/ age.
Aetiology of osteomyelitis
Common causes of osteomyelitis:
- Trauma- common in children
- Infection drug use
- surgery- presence of foreign bodies e.g. artifical hip or screw
- immunocompromised
- ischaemia
Can be caused by direct inoculation (exogenous) e.g abscess, burn, puncture wound, trauma.
- or blood-borne bacteria (haematogenous) e.g. IV misuse.
Common infecting organisms:
^often polymicrobial.
- Staphylococcus aureus - present in over 50% of patients.
- Streptococci (A& )
- Gram negative enteric organisms i.e. enterobacter
- Anaerobic bacteria.
- Salmonella species - common in sickle cell anaemia.
Common infecting organisms in immunocompromised patients (e.g. AIDs):
1. Fungi
2. Mycobacteria
^ They cause haematogenous osteomyelitis.
Posttrauma osteomyelitis
- Open fracture - broken skin means direct access of bacteria to broken surfaces
- Caused by high-energy injuries that result in large dirty wounds
- Treatment = surgical debridement and lavage (of contaminated material and dead bone)
- Delayed treatment = osteomyelitis and infected nonunion fracture
Postsurgery osteomyelitis
- Caused by foreign bodies (joint prostheses, plates and screws) which can harbour infection
- Preventative treatment = aseptic techniques and using antibiotics as prophylaxis
- if infection occurs, implants must be removed
Acute haematogenous osteomyelitis
- Usually seen in children
- May be spontaneous or precipitated by trauma
NOTE: view notes for diagram
Risk factors for osteomyelitis in adults?
- Older age
- Debilitation
- Haemodialysis
- Sickle cell disease
- Injection drug use
Pathophysiology of osteomyelitis: main routes of infection
- Haematogenous osteomyelitis
- Results from bacteraemia (bacteria in blood).
- Monomicrobial
- Most common form in children
- Vertebral osteomyelitis is the most common haematogenous osteomyelitis in adults.
- Risk factors include - sickle cell anaemia, IV drug use, immunosuppression (due to meds or HIV) & infective endocarditis.
- Bacteria settles in metaphysis of long bone.
- Inflammation & pus formation w/in bone.
- Pus escapes through haversian canals to form a subperiosteal abscess.
- This can enter the synovium causing septic arthritis
- Pus surrounding both sides of bone —> bone death (sequestrum).
- This sequestrum harbours infection.
- Involcrum = periosteal new bone forming aorund sequestrum as the body tries to fight infection.
—> must be excised at surgery to prevent chronic osteomyelitis
- Non-haematogenous osteomyelitis
- Spread from adjacent infected tissue or opened bones causes about 80% of osteomyelitis.
- Often polymicrobial.
- Common in adults
- Risk factors include - diabetic foot ulcers, pressure sores, diabetes & peripheral arterial disease.
Presentation of osteomyelitis (including which bones commonly affected in children vs adult)
- Tender
- Red & swollen.
- Limp & reluctance to weight-bear - common in children.
- Loss of function in affected bone
- Non-specific pain
- Low grade fever for 1 - 3 months duration
- Common in tibia & femur - & other long bones.
- Lack of energy & feel irritable.
- warm joint
In neonates, infants & elderly
- nonspecific general symptoms like malaise.
- Chronic (can be quiescent) = swollen, thickened, woody skin, chronic discharging sinus.
Commonly infected bones:
- Children = metaphyses of tibia, femur or humerus.
- Gram positive infections are most common in children.
- Adults = haematogenously spread osteomyelitis usually affects vertebrae.
Investigations for osteomyelitis: blood tests
increased WCC, ESR & CRP
Osteomyelitis may be present in someone in diabetes despite normal inflammatory markers.
Microbiology specimens: blood cultures (before antibiotics)!
Investigations for osteomyelitis: radiological
MRI - detect early osteomyelitis. Shows bone marrow oedema.
X ray:
- Brodie abscess
- May see osteopenia
X-ray in acute osteomyelitis:
- Intra-osseus absess
- Sub-periosteal abscess
- Peripheral sclerosis
- Periosteal reaction - thicking of periosteum, including codman’s triangle.
- Focal bony lysis, including cortical loss (after 10. days)
X-ray in chronic osteomyelitis:
- Sequestrum- a piece of necrotic bone detached from the healthy tissue.
- Involucrum - new bone formation around a sequestrum - for chronic or untreated cases.
- Cloacae - an opening in the involucrum which allows drainage of purulent & necrotic material out of dead bone.
NOTE: view x-ray on notes!
Management for Osteomyelitis: Pharmacological
- Take blood cultures before starting antibiotics.
- Flucloxacillin - IV for 6 weeks (for Staphylococcus aureus).
- Clindamycin if penicillin allergic.
- Analgesia
- Splints - immoblise the limb for comfort.
- Antibiotic resistant osteomyelitis e.g. MRSA require vancomycin.
- Monitor & manage co-morbidities e.g. diabetes
Management for osteomyelitis: surgical
- Abscess drainage
- Sequestrum surgically removed
- Chronic cases - extensive surgery for infected bone & implants.
- Patients not fit for surgery - treat flare-ups & suppress infection with antibiotics.
Prognosis for osteomyeltis
- Acute = good outcome, full recovery
- Chronic (following surgery or trauma) = surgical procedures required & possible amputation.
- Amputation requires careful assessment w/ MRI & counselling.
