Osteomyelitis Flashcards
Define osteomyelitis.
Osteomyelitis is an inflammatory condition of bone caused by an infecting organism, most commonly Staphylococcus aureus.
It usually involves a single bone but may rarely affect multiple sites. It may occur in the peripheral or axial skeleton
Which two patient groups should you most suspect osteomyelitis?
- Unwell child with a limp
- Immunocompromised patients
What are the risk factors for osteomyelitis?
- Previous osteomyelitis
- Penetrating injury
- IV drug use
- Diabetes
- HIV infection
- Recent surgery
- Distant or local infections
- SCD
- RhA
- CKD
- Immunocompromising conditions e.g. HIV or autoimmune disease
- Upper respiratory tract or varicella infection (in children)
What is the aetiology of osteomyelitis?
- haematogenous spread of infection
- direct inoculation of micro-organisms into bone
- or from a contiguous focus of infection
What are the common organisms causing osteomyelitis?
Staphylococcus aureus, streptococci, Enterobacteriaceae, and anaerobic bacteria but also depends on age group.
- Infants - Staph aureus/GBS
- <5yo - Staph aureus/Kingella kingae/GAS
- >5yo - Staph aureus/GAS
- Adults - Staph aureus/CNS/aerobes and anaerobes
- etc
How are degrees of osteomyelitis classified?
I to IV
I - medullary and endosteal from haem spread
II - superficial osteomyelitis from contiguous focus of infection
III - medullary and cortical, limited to circumference
IV - diffuse involvement
What are the clinical features of osteomyelitis?
- Limp/reluctance to weight bear - common in children
- Non-specific pain - may last for 1-3months
- Malaise and fatigue
- Local inflammation, tenderness, erythema or swelling
- Fever - usually low grade
- Wound drainage from sinus tracts
- Reduced range of movement
If vertebral osteomyelitis: local back pain associated with systemic symptoms and paravertebral muscle tenderness and spasm
What is a differential for local foot joint inflammation with erythema and swelling in a patient with diabetes?
Osteomyelitis or Charcot joint
What investigations would you do for osteomyelitis?
- FBC - WCC may be raised
- ESR and CRP - raised
- Blood cultures
- Plain XR of affected area
Other:
- Bone samples for culture- image-guided fine needle aspiration (FNA), or needle puncture
- Swabs
- Urine MC&S
- Probe to bone test - if the probe can reach bone then so can infectious bacteria
- MRI - most definitive and helpful imaging modality
- FDG-PET or bone scintigraphy - can show hot spots of infection
What is seen on XR in acute osteomyelitis?
Normal initially
Osteopenia 6-7 days after infection onset and evidence of bone destruction, cortical breaches, and periosteal reaction follow quickly
Involucra (thick sheath of periosteal new bone surrounding a sequestrum) and sequestra (piece of devascularised bone that becomes separated from main bone) sometimes seen
When does discitis become apparent on XR?
2-3 weeks into illness
What is seen on XR in vertebral osteomyelitis?
Localised rarefication (‘thinning’) of a single vertebral body, and then later, anterior bone destruction
What XR features are seen in chronic osteomyelitis?
Intramedullary scalloping, cavities, and cloacae may be seen, with a ‘fallen leaf’ sign (piece of ensodteal sequestrum detached and fallen into medullary canal - shown )
What is the management of osteomyelitis?
- Sepsis protocol and take cultures before starting abx
- Antibiotics - initially IV then switch to oral, total 6 weeks
- Analgesia
- Immobilise limb for comfort
- +/- DVT prevention
-
+/- Surgical debridement or drainage of abscess
- once dead bone or biofilm has been established, antibiotics alone will not cure the infection
NB: tuberculous osteomyelitis usually does not require surgical intervention
What is the management of chronic osteomyelitis?
Chronic = >3months or if there is dead bone or biofilm established
- Clinical staging (Cierny -Mader) and assessment for surgery
- Surgical debridement
- Antibiotics
