Bone and joint infection Flashcards
In what ages is septic arthritis usually seen
Extremes of age- older than 65 or the very young
Is it ususally mono-articular or poly-articular
Mono
How does septic arthritis usually present
- Red
- Swelling
- Inflammation
- Fever
What bacteria usually give a ‘cold inflammatory process’
Microplasma such as TB
Slow growing
Why does septic arthritis happen more in elderly
More likely to have osteoarthritis- more injections/ procedures
How do the majority of infections get to the joint capsule in septic arthritis
Via the blood supply
What organism most commonly leads to septic arthritis
Staph aureus
Name some other common organisms which can lead to bone/ joint infection
Streptococci pneumoniae/ group B. pyogenes
How do the microorganisms lead to bone/ joint infections
Activation of macrophages/ T/ B cells lead to damage of the joint
3 potential causes of bone/ joint infections
Previous damage to joint
Untreated systemic infection
Conditions that affects blood supply to the joint
What is the most commonly affected joint in septic arthritis
Knee
What joints are infrequently affected by septic arthritis
Wrist, shoulder, fingers
Describe the lab findings for somebody with septic arthritis
- Elevated ESR
- Neutrophilia (esp in children)
How will synovial fluid appear in bone/ joint infection
Turbid/ purulent
Gram stain positive
Low glucose level
Leukocytes
In what % of septic arthritis cases are blood culture positive
1/3
Describe the radiological findings of somebody with septic arthritis
- Initially not useful- may see some soft tissue swelling
- Joint capsule distension depending on
- Erosition of articular cartilage and soft tissue swelling
When do you see destructive changes radiologically in somebody with septic arthitis
After 2 weeks
What do you see radiologically in myobacterial infection?
4
Joint space narrowing
Effusion
Erosion
Cyst formation
Differential diagnoses for septic arthritis
Acute rheumatoid arthritis
Gout/ pseudogout
Chondrocalcinosis
How do you treat septic arthritis
Drainage
Broad spectrum antibiotics asap and then modify depending on gram stain
How long will septic arthritis patients be on IV antibiotics for
3-4 weeks
When does reactive arthritis occur
Post infection
How do osteomyeltitis usually spread
Haemotagenous spread
What usually causes osteomyelitis in adults
Trauma (open fracture)
What are the consequences of osteomyelitis
Abcess on the metaphyseal side of the growth plate
Makes bone around the abcess to try and keep it from the healthy tissue
What are the 2 general predisposing factors for osteomyelitis
Impairment of immune surveillance
Impairment of local vascular supply
What impairments of the immune surveillance can lead to osteomyelitis
Malnutrition
Extremes of age
What impairments of vascular supply can lead to osteomyelitis
Diabetes
Venous statis
Radiation fibrosis
Sickle cell disease
Describe the clinical features of osteomyelitits
Hametogenous long bone Abrupt onset of fever Decreased limb movement Local non specific pain Elevated neutrophil and ESR
What is the result of chronic osteomyelitits
Local bone loss and persistent draingage through the sinus
How do you investigate chronic osteomyelitis
Bone biopsy
Blood cultures
Neutrophil count
ESR
How is osteomyelitis managed surgically
Debirdement to remove teh seqeustrum ( dead bone)
Reconstruct the bone
How long must a person be on antibiotics for chronic osteomyelitis
4-6 weeks
What is involcrum
The new bone that has been remodelled
How does prosthetic bone and joint infection occur
- Occurs in the osteous tissue adjacent to prosthesis at the bone/ cement interface
- Results from local inoculation at surgery or post-op spread from wound sepsis
