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)
What is the epiphysis?
The head of a long bone
What is the diaphysis?
The shaft of a long bone
What is the metaphysis?
The bit between the epiphysis and the diaphysis
What is the official name for joint infection?
Septic arthritis
Why does septic arthritis need to be treated quickly?
It can destroy a joint in 24 hours
Very destructive and quickly developing disease
Which type of joints are affected in septic arthritis?
Synovial
Who gets septic arthritis?
More often in children, young adults and the elderly (above age 80)
What are the risk factors of septic arthritis?
Bacteraemia
Pre-existing joint disease:
- RA
- OA
Diabetes
Immunosuppression
Recent joint surgery
Prosthetic joints
IV drug abuse
Which bacteria are the most common cause of septic arthritis?
Staph aureus
Which pathogens are common causes of septic arthritis in the immunocompromised?
Gram negative bacteria
Mycobacterium
Fungi
What is gonococcal arthritis?
Septic arthritis caused by a disseminated gonococcal infection
Clinical features of gonococcal arthritis?
Polyarthritis
Tenosynovitis
Fever
Maculopapular rash:
- common in peripheries
Clinical features of septic arthritis?
Acute development
Inflammation of joint:
- pain
- red
- swollen
- hot
- children may not use joint
Fever
Septic arthritis is most commonly polyarthritis.
True or false?
False
90% of the time it is mono-arthritic
Investigation of septic arthritis?
Blood:
- ESR + CRP raised
- WBC raised
X-ray:
- normal initially, joint damage will show later
USS: may show any effusion
Aspirate joint:
- culture aspirate
- look for crystals to rule out gout
What is the most important thing to do when you suspect someone may have septic arthritis?
Aspirate the joint
Collect the fluid
Send it off for analysis, culturing
Management of septic arthritis?
Aspiration
Antibiotics chosen after aspirate has been cultured
Long course: 6 weeks minimum
Analgesia
Promptly refer for joint washout, repeated aspiration until no further effusion
Figure out how the infection got in and amend it
If joint is too damaged consider replacement, debridement, amputation
What does debridement mean?
Removal of dead or damaged tissue
