Bone & Joint infection Flashcards
What is osteomyelitis?
Inflammation of bone tissue as a result of infection
Who gets osteomyelitis?
Older people generally
What are the risk factors of osteomyelitis?
Type II diabetes
Peripheral vascular disease
Pre-existing bone/joint problem
- arthritis
- prostheses
Immunodeficiency
Bacteraemia
Osteomyelitis is rare.
True or false?
True
Name the ways an infection can be introduced into the bone?
- Direct Inoculation
- Contiguous spread (local)
- Haematogenous spread
How does direct inoculation cause osteomyelitis?
Infection gets in when the bone is damaged
Needs to be a hole in the bone for the infection to get in
Infection goes in and establishes itself inside the bone
Usually a result of trauma or surgery
How does contiguous spread cause osteomyelitis?
Infection spreads from adjacent soft tissues and joints
Often it begins as a cellulitis and spreads to the bone
How does haematogenous spread cause osteomyelitis?
Bacteria reach the bone by traveling through the blood stream from another site in the body
What features of a bacteria make it more able to infect bone?
Microbial surface components that adhere to bone matrix molecules like:
- collagen
- fibronectin
- fibrinogen
Which bacteria is often responsible for osteomyelitis?
Staph. aureus
Streptococcus species
Enterobacter species
Which bacteria is associated with osteomyelitis in children?
Haemophilus influenzae
Which species of bacteria is associated with osteomyelitis in the immunosuppressed and IV drug users?
Pseudomonas species
Osteomyelitis can be acute or chronic.
What would you see looking down a microscope at a biopsy of bone affected by acute osteomyelitis?
Inflammatory cells
Oedema
Vascular congestion
Small vessel thrombosis
Osteomyelitis can be acute or chronic.
What would you see looking down a microscope at a biopsy of bone affected by chronic osteomyelitis?
Necrotic bone: sequestra
New bone formation: involucrum
Neutrophil exudates
Lymphocytes and histiocytes
Clinical features of osteomyelitis?
Local:
- dull pain
- tenderness
- warmth
- erythema
- swelling
Systemic:
- fever
- rigors
- sweats
- malaise
What would you see in a case of chronic osteomyelitis?
Hardened, woody skin
Erythema
Swelling
Deep, large ulcers that fail to heal
Non-healing fractures
Sinus formation
Where in the body does osteomyelitis most often occur?
Hip
Vertebrae
Pelvis
Investigation of osteomyelitis?
Blood:
- raised WBC count
- raised ESR/CRP
- blood cultures
Imaging:
- X-rays normal initially, new bone is formed soon however which is visible
- shows up marrow oedema + inflammation
Bone biopsy:
- 2 specimens
- microbiology test on them
- look under microscope to see inflammation + necrosis
Management of osteomyelitis?
Analgesia
Support for the limb, splint
Antibiotics
Drainage of abscess if there is one
Removal of dead bone
Amputation of very severe
How do you choose which antibiotics to treat osteomyelitis with?
Which ones are appropriate for the microbe
Which one can penetrate bone and soft tissue best
What is TB osteomyelitis?
It is an extra-pulmonary manifestation of TB
Where does TB osteomyelitis mostly affect?
It often affects vertebrae
What is sequestrum?
Dead bone
What is involucrum?
Periosteal new bone which forms around the sequestrum (dead bone)
