E: Septic Arthritis + Osteomyelitis Flashcards
What is septic arthritis
Infection of a joint
How does bacterial contamination of a joint occur
- Haematogenously
- Direct contamination
How can infection from the blood stream occur
- From a distant site (eg. abscess)
- Or, disseminated infection (eg. gonorrhoea)
How does direct contamination occur
- Trauma
- Iatrogenic (eg. arthroscopy)
What is the most common cause of septic arthritis
Staphylococcus aureus
What may cause septic arthritis in sexually active patients
N. Gonorrhoea
What are 5 risk factors for septic arthritis
- Old age
- Diabetes
- Immunocompromised
- Prosthetic joints
- IVDU
- Chronic skin infection
Explain the clinical presentation of septic arthritis
- Fever
- Reduced range of movement
- Pain
How will a joint appear in septic arthritis
Erythematous, swollen joint
What blood tests may be performed in septic arthritis
FBC
ESR
CRP
What is gold-standard investigation of septic arthritis
Joint aspiration
What is joint fluid aspirate obtained for
- Culture
- Cell count
- Gram stain
- Glucose
- Crystal analysis
How will joint aspirate fluid appear in septic arthritis
Cloudy (due to being purulent)
What WCC is diagnostic for septic arthritis
> 50,000 in native joints.
Often >1,100 in prosthetic joints
How will glucose appear in joint aspirate in septic arthritis
<60% of serum glucose
What imaging is recommended for septic arthritis
Lateral and AP x-rays
What is the Kocher criteria used for
Differentiate septic arthritis as a cause of hip pain in children (often compared to transient synovitis of the hip)
How is septic arthritis managed
IV Vancomycin (30mg/kg/day) for 2W, then switch to Vancomycin PO for 4W. And joint aspiration.
If an individual is allergic to vancomycin, what should be used
Clindamycin or cephalosporin
What are 4 factors that may indicate gram-negative septic arthritis
Old age
Recurrent UTI
Recent abdominal surgery
What is used to manage gram-negative septic arthritis
IV Ceftriaxone 2g/24h and joint aspiration
what is osteitis
infection of the bone
what is osteomyelitis
infection of the bone marrow
in which age group does haematogenous ostemyelitis tend to occur
children and adolescents.
50% of cases occur in under 5y
in which age group does vertebral osteomyelitis tend to occur
adults
what is haematogenous osteomyelitis
haematogenous spread of a disseminated pathogen
what is the most common cause of haematogenous osteomyelitis
s.aureus
what are 4 exogenous causes of osteomyelitis
- Trauma
- Iatrogenic
- Secondary infection from diabetic foot ulcer
- Contigous spread from adjacent tissue
what are 3 local risk factors for osteomyelitis
- Open fracture
- Soft tissue damage
- Poor perfusion
what are 3 systemic factors for osteomyelitis
- Immunocompromised
- Systemic disease
- IVDU
how long does it take for acute osteomyelitis to occur
sudden onset over hours-days
how long does it take for chronic osteomyelitis to occur
onset over months-years
how will acute osteomyelitis present
- Pain at infection site
- Joint is tender, erythematous, warm, swollen
- May be fever, malaise
in infants what is the most common site of osteomyelitis
Metaphysis of long bone
in children, what is the most common site of osteomyelitis
Metaphysis of long bone
in adults, what is the most common site of osteomyelitis
Vertebrae
what is chronic osteomyelitis and how will it present
occurs following previous episode of osteomyelitis and may persist for months
what pathogen commonly causes osteomyelitis
s. aureus
what organism tends to cause osteomyelitis in diabetic patients with foot ulcers
s. epidermis
what organism may cause osteomyelitis in patients with prosthesis
s. epidermis. Although due to prevalence s.aureus more commonly causes osteomyelitis in patients with prosthetics
what organism may cause osteomyelitis in IVDU
pseudomonas auerginosa
what organism may cause osteomyelitis in plantar puncture wound (particularly if rubber footwear is worn)
pseudomonas auerginosa
what organism may cause osteomyelitis in sickle cell patients
salmonella
what organism may cause osteomyelitis in patients with recurrent UTI
enterobacteria
what investigations are ordered in osteomyelitis
FBC CRP ESR Blood culture X-ray MRI
what is the problem with WBC for identifying osteomyelitis
only raised in 1/3 of patients
What does ESR show
if ESR decreases following treatment it is a good prognostic indicator
What is the most sensitive test in osteomyelitis
CRP (97% raised in osteomyelitis)
What may positive blood cultures indicate
Disseminated haemotegenous infection. Although is often negative in osteomyelitis
What is the problem with x-ray for acute osteomyelitis
It takes 2W for evidence of infection to present on x-rays
what is the gold standard for identifying osteomyelitis
MRI
what sign is seen on MRI in osteomyelitis
penumbra sign
what is the penumbra sign
a dark abscess in the centre with hyper intense thin ring of white sclerosis around the outside
what is used as a confirmatory test for osteomyelitis
bone biopsy
why is a bone biopsy performed
to look at histology, be able to perform gram stain and culture
what is the management of osteomyelitis
IV Flucloxacillin for 6W
what should patients with osteomyelitis also be considered for and why
Surgical debridement. If patients have necrotic tissue or a biofilm it will not heal without debridement
what scoring system is used to predict prognosis in osteomyelitis
Cierney-Mader Classification
what are 4 complications of osteomyelitis
- Sepsis
- Amputation
- Marjolin’s Ulcer (malignant transformation)
- Chronic osteomyelitis
what typically causes chronic osteomyelitis and what is a risk factor for this
- Presence of SCC
- RF: presence of a chronic draining sinus
