Osteomyelitis Flashcards
What is osteomyelitis?
Progressive infection of the bone [or bone marrow] and surrounding soft tissue often caused by pyogenic bacteria
What are the different types of bone infection?
- Acute
- Chronic
- Specific (eg TB)
- Or non-specific (most common)
Who does acute osteomyelitis commonly affect? And RF?
- Mostly children (different ages)
- Boys > girls
- History of trauma (minor)
- Other disease
- Diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell
How does acute osteomyelitis spread?
- haematogenous: children and elderly
- local: from contiguous site of infection
- trauma (open fracture)
- bone surgery (ORIF)
- joint replacement
- secondary to vascular insufficiency
What are some of the sources of infection in acute osteomyelitis?
- In infants: infected umbilical cord
- In children: boils, tonsilitis, skin abrasions
- In adults: UTI, arterial line
What are the most common infection organisms in acute osteomyelitis?
Staph aureus
Which long bones are affected by acute osteomyelitis?
Effects long bones at the metaphysis:
- Distal femur
- Proximal tibia
- Proximal Humerus
Which joints are affected by acute osteomyelitis?
Effects joints with intra-articular metaphysis:
- Hip
- Elbow
What are 8 steps of pathogenesis of acute osteomyelitis?
- Starts at metaphysis
- Vascular stasis (venous congestion and arterial thrombosis)
- Acute inflammation - increased pressure
- Suppuration
- Release of pressure
- Necrosis of bone (sequestrum)
- New bone formation (involucrum)
- Resolution (or not)
What are clinical features of acute osteomyelitis in infant?
- Aysmptomatic or very ill
- Failure to thrive
- Drowsy/irritable
- Metaphyseal tenderness and swelling
What are clinical features of acute osteomyelitis in children?
- Severe pain
- Reluctancy to move; not weight bearing
- May have swinging pyrexia and tachycardia
- Malaise
What are clinical features of acute osteomyelitis in adults?
- Primary OM seen commonly in thoracolumbar spine
- Backache
- History of UTI
- Elderly, DM, immunocompromised
- Secondary OM is far more common: often after open fracture or surgery
What do we do to diagnose acute osteomyelitis?
- History and examination
- FBC and diff WBC
- ESR, CRP
- Blood cultures x3 (at peak of temp. 60% will be positive)
- U&Es
DDx for acute osteomyelitis?
- Acute septic arthritis
- Acute inflammatory arthritis
- Trauma (fracture, dislocation, etc.)
- Transient synovitis (“irritable hip”)
- Soft tissue infection
- Cellulitis
- Necrosing fasciitis
- Erysipelas
What investigations do we run for acute osteomyelitis?
- X-ray (normal in the first 10-14 days)
- Ultrasound
- Aspiration
- Isotope Bone Scan (Tc-99, Gallium-67)
- Labelled white cell scan (Indium-111)
- MRI
What can be seen on radiographs as acute osteomyelitis progresses?
- Early radiograph: minimal changes
- 10-20 days early periosteal changes
- medullary changes - lytic areas
- late osteonecrosis - sequestrum
- late periosteal new bone - involucrum
What is the Tx for acute osteomyelitis?
supportive treatment for pain and dehydration
- general care and analgesia
rest and splintage
antibiotics
- route (IV/oral switch – 7-10 days?)
- duration (4-6 wks – depends on response, ESR)
- choice - empirical (Fluclox + BenzylPen) while waiting
Why will antibiotics sometimes fail as treatment for acute osteomyelitis?
- Drug resistance
- Bacterial persistance
- Poor host defences
- Poor drug absorption
- MRSA etc….
When is surgery indicated for acute osteomyelitis?
Once there is dead bone or biofilm established antibs alone cannot cure and thorough surgical debridment is required.
- Aspiration of pus for diagnosis & culture
- Abscess drainage
- Timing, drainage, lavage
Complications of acute osteomyelitis?
- Septicaemia, death
- Metastatic infection
- Pathological fracture
- Septic arthritis
What causes chronic osteomyelitis?
- May follow on from acute osteomyelitis
- May start de novo: following an operation, following open fracture, immunosuppresed, DM, elderly
- Repeated breakdown of healed wounds
What is the causative organism for chronic osteomyelitis?
Mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus
What are the 4 steps for pathogenesis of chronic osteomyelitis?
- Cavities
- Dead bone (retained sequestra)
- Involucrum
- Histological picture is one of chronic inflammation
What are the complications of chronic osteomyelitis?
- Chronically discharging sinus + flare-ups
- Ongoing infection
- Pathological fracture
What are some of the Tx options for chronic osteomyelitis?
- long-term antibiotics
- Eradicate bone infection surgically
- Treat soft tissue problems
