Bone and joint infections Flashcards
Septic arthritis is commonly [mono-articular / poly-articular]
The most common joint affected by septic arthritis is which joint? [1]
Septic arthritis is commonly mono-articular
Knee most common
When does non-pyogenic (cold) septic arthritis occur? [1]
Which pathogen causes this? [1]
Chronic infection; TB infection
Name an organism that cause septic arthritis for each organism type of bacteria
Gram positive cocci [1]
Gram positive bacilli [1]
Gram negative cocci: [1]
Gram negative bacilli [1]
Gram positive cocci: staphylococcus aureus
Gram positive bacilli: clostridium sp
Gram negative cocci: Neisseria gonorrhoea
Gram negative bacilli: Escherichia coli, pseudomonas aeruginosa, haemophilus influenza
Which populations suffer from septic arthritis the most? [2]
Explain why [1]
Young
Majority older population; undergoing more therapy for alternative diseases (RA; OA)
Describe pathogenesis of septic arthritis in children [1]
Describe pathogenesis of septic arthritis in adults [4]]
Children:
* hematogenous spread: infection elsewhere in the body goes into joint
Adult:
* hematogenous spread most common
* local soft tissue infection
* penetrating trauma
* diagnoistic or therapeutic procedures
What is the most common cause of septic athritis? [1]
Staphylococcus aureus : 90% of all cases
Biggest cause of mortality in septic arthritis is
Staphylococcus aureus
Streptococci spp.
Clostridium sp
Neisseria gonorrhoea
Escherichia coli
Biggest cause of mortality in septic arthritis is
Staphylococcus aureus
Biggest cause of mortality in septic arthritis is
Staphylococcus aureus
Streptococci spp.
Clostridium sp
Neisseria gonorrhoea
Escherichia coli
Biggest cause of mortality in septic arthritis is
Staphylococcus aureus
Septic arthritis
Which pathogen has reduced impact due to vaccination schemes [2]
Haemophilus influenza (paediatric before immunization)
Streptococcus
What are the age related differences in causative organism of septic arthritis?
What is the difference between children and adults regarding which joints are affected by septic arthritis?
Children: more spread out
* Knee most common
* Hip common
* Ankle
* Elbow
Adults:
* Mostly knee joint
* Other joints also affected though
Septic arthritis
What investigations would you conduct to diagnose? [5]
- Elevated ESR
- Children: neutrophilia
- Synovial fluid analysis: yellow & cloudy; lumpy & purelent
- Gram stain positive: due to Staphylococcus aureus being the most common
- Blood culture positive
How would a S. aureus infection appear in culture? [1]
Appears as grape like clusters, on trypticase soy agar plate produces yellow pigment: staphlyoxanthin
Describe how septic arthritis joint (synovial) fluid examination would present [4]
Turbid or purulent
Leukocytes >50,000/mm3, pred. neutrophils
Gram stain positive in one-third
< 25mg/dL glucose (much lower than serum)
How does mycobacterial infection cause radiological changes? [4]
Joint space narrowing
Effusion
Erosions
Cyst formation
Describe pathophysiology of reactive athritis [1]
What are the triad of symptoms? [3]
Post infection (e.g. STDs / salmonella) arthritis can occur couple of weeks later in one joint
Triad of symptoms: urethritis/cervicitis, conjunctivitis and arthritis
In which joints is reactive arthritis most common in? [2]
How does it differ from septic arhritis? [1]
knees, ankles and feet
completely sterile: no bacteria or virus, and normally clears up in a couple days.
Which type of MRI imaging would be best for septic arthritis? [1]
Why? [1]
MRI T2: fluid appears white - easier to see inflammation
Describe radiological changes seen in septic athritis patients? [4]
May see soft tissue swelling
Joint capsule distension
Destructive changes seen after at least 2 weeks
* Erosion of articular surface
* Associated soft tissue swelling
Where does TB primarily spread to? [1]
Most commonly goes to thoracic top lumbar regions
Describe how TB can spread from spine to elsewhere in the body [4]
Can spread into surrounding tissues like psoas major –> iliacus -> sacrioilac joint / & or hip joint –> femoral side of knee
Why does acute blood born osteomyelitis affect children? [2]
Have a very rich blood supply to the bones, especially the metaphyseal ends of the long bones as this is where the growth plate is
The capillary loops near the metaphysis have slow flow/sluggish flow due to a rich blood supply here, meaning they are more at risk for bacterial invasion of the bone from the blood here
Describe how osteomyelitis causes abscesses to grow
- Bacteria enters the bone, it commonly lodges just below the epiphyseal growth plate
- Bone produces new bone around the bacterial infection to try and wall off and contain the bacteria in one location, however it walls it off yet this cannot be accessed by antibiotics as it is walled off.
- Can cause bone to die
Common consequences of osetomeylitis? [2]
Rare consequences of osetomeylitis? [2]
Common:
* Local bone loss
* Persistent drainage through sinuses
Rare
* Squamous cell carcinoma
* Amyloidosis
Risk factors for osteomyelitis? [6]
Age
Malnutrition
Impairment of local vascular blood supply:
* Diabetes mellitus
* Venous stasis
* Radiation fibrosis (radiation therapy damaging blood vessels)
* Sickle cell disease (due to crisis)
Describe how you diagnose osteomyelitis [4]
How does it appear on ultrasound? [2]
(same as SA)
Local non-specific pain
Elevated neutrophil count (< 50% of cases)
Elevated ESR
Ultrasound:
* Cortical thinning
* Inflamation
* Periosteal lifiting: abscess lifting it off
What is this sign of osteomyelitis called? [1]
Brodie’s abscess
Lytic lesion oval in shape, surrounded by thick dense reactive sclerosis that fades into surrounding bone.
Lucent tortuous channel extending from growth plate prior to physeal closure
How do you treat chronic osteomyelitis? [5]
Puncture drainage if abscessed
Surgical debridement
Reconstruct bone (allograft/ autograft)
Antibiotics (4-6wks, at least 2 IV):
* Vancomyocin cement beads
* Flucoxallin (gram +ve)
* Clindamycin
* Piperacillin
* Ciprofloxacilin
Describe this radiological sign of chronic osteomyelitis? [1]
Abscess
How do you investigate for chronic osteomyelitis? [3]
MRI:
* Bone scintigraphy if MRI not available or suspicion of multifocal osteomyelitis - radiation that shows reactive bone
- Bone biopsy
- Blood samples
- Radiography
Describe treatment of chronic osteomyeltis [5]
Puncture drainage if abscess identified
Reconstruct bone (allograft or autograft)
Surgical debridement to remove dead bone
Antibiotics for 4-6 weeks (at least 2wks IV):
* vancomycin cement beads: dissolve and give steady supply of vancomycin
Bone graft (& muscle graft)
Which antibiotics would you give for chronic osteomyelitis [1]
Vancomycin cement beads
How does prosthetic bone and joint infection present? [2]
Hot, swollen, down the line of the knee replacement.
It is usually gradual onset with progressive joint pain and occasionally sinus development (in which pus can drain out via scars from surgery, etc).
The gradual onset is usually due to the antibiotic in bone cement can hinder growth but not completely destroy them
Why does joint infection occur when giving prosthetic bone / joint replacements occur? [2]
Where does it occur? [2]
Occurs in osseous tissue adjacent to prosthesis:
* bone cement interface
* bone contiguous with prosthesis (cementless devices)
Results from:
* local inoculation at surgery or post-op spread from wound sepsis
* haematogenous spread
Management of infections that have occurred from joint replacement infections? [2]
Removal of prosthesis, antibiotics for 6wks, re-implantation of new prosthesis 4 weeks after removal - 90%+ success
Long term suppressive antibiotics
What is sequestrum in chronic osteomyelitis? [1]
What is Involucrum in chronic osteomyelitis? [1]
Sequestrum: fragment of necrosed bone that has become separated from surrounding tissue
Involucrum: covering or sheath that contains a sequestrum of bone
