Bone Infections Flashcards
What is the most common infecting agent in acute osteomyelitis?
Staph aureus
haemophilus in children
Strep
How does acute osteomyelitis occur?
Most post-traumatic/ open fracture
In children or immunosuppressed by haematogenous spread
On x-ray what does acute osteomyelitis look like?
Dying necrotic inflammatory tissue
What should you do if there is pus?
Let it out!
What is the term used to describe the mass that often grows in chronic osteomyelitis?
Involucrum
How does septic arthritis occur?
innoculation
metaphyseal spread
Direct haematogenous spread
Describe the clinical picture of a joint with septic arthritis?
Severely painful, red, hot, swollen and tender joints with limited movement
What are the most common infecting organisms in septic arthritis?
- Staph aureus #1
- Streptococci
- Coagulase negative strep – prosthetic joint
- Neisseria gonorrheae – sexually active
- Haemophilus influenzae – preschool – uncommon as HIB vaccine
What Ix are required in suspected septic arthritis?
History and examination
Joint aspiration M,C and S
Blood culture if pyrexial- organisms may spill into blood causing bacteraemia
Exclude crystal arthropathy
What AB are given for septic arthritis?
Flucloxacillin IV high dose and adjust when organisms are confirmed
If <5yo add cefriaxone to cover H. influenzae
What bugs are involved in chronic osteomyelitis?
often slow growing – Mycobacterium TB, Pseudomonas aeruginosa, salmonella, brucella and coliforms (E.coli)
What AB should be given for cellulitis?
Cover staph and strep
Flucloxacillin and benzylpenicillin
What kinds of surgery can be used for an infected arthroplasty?
Two stage revision 80-90% control of infection
One stage revision (rarely done) 70-80%
List some prophylactic measures that can be used to decrease the risk of an arthroplasty becoming infected during surgery.
Laminar flow 24 hours antibiotics starting with induction Antibiotics in cement Good hand washing Good surgical technique
How do prosthetic joints become infected?
Early – within a month – with haematoma/ wound sepsis
Late – after one month – contamination at time of operation
LIst some risk factors for an arthroplasty becoming infected.
Rheumatoid arthritis
obesity
diabetes
malnutrition
If the arthroplasty is infected with staph epidermidis, which antibiotic should be given?
Vancomycin initially
What actually is osteomyelitis?
Inflammation of bone and medullary acvity, usually located in long bones.
What antibiotic is given initially in osteomyelitis?
High dose flucloxacillin
What is necrotizing fasciitis?
Uncommon severe infection of the subcutaneous soft tissue – spreads through fascial planes - medical emergency
What are the two types of necrotizinf fasciitis?
Type 1 - anaerobes plus multiple other bacteria “synergistic gangrene”
Type 2 - “flesh eating bacteria”
What is the immediate treatment for necrotizing fasciitis?
Surgical debridement and Penicillin (Vanco if pen allergic) and Clindamycin
What organism causes gas gangrene?
Clostridium perfringens
How do the spores of C. perfringens cause gas gangrene?
Get into tissue by dirt getting in to open wound - normally trauma
What is the pathogenic process involved in gas gangrene?
myonecrosis – accumulation of gas bubbles in subcutaneous spaces gas gangrene
What Tx is required for gas gangrene?
Urgent debridement
High dose Penicillin +/- Metronidazole +/- hyperbaric O2
What organism causes tetanus?
Clostridium tetani
What is the pathogenic process involved in tetanus?
C. tetani produces a neurotoxin –> spastic paralysis (lock jaw)
What Tx is required for tetanus?
Surgical debridement #1
Antitoxin
Supportive measures – respiratory intubation and ventilation
Antibiotics – Penicillin and Metronidazole
Booster vaccination (toxoid)
What is PVL producing staph aureus?
Toxin that destroys white blood cells
What Tx is required for an infection caused by PVL producing staph aureus?
Flucloxacillin, clindamycin, linezolid, depending on sensitivities
