Bone and Joint Infection Flashcards
Septic arthritis is a common…?
How many people per 100,000 does it affect in the UK?
Destructive athroplasty
8 per 100,000
How does septic arthritis usually develop?
Follows haematogenous spread
Acute septic arthritis is usually…?
Pyogenic
Chronic is usually non-pyogenic
What are the signs/symptoms of acute septic arthritis?
Mild in 60-80% of cases
Temperature >39 degrees in 1/3 of cases
Limited joint movement
Synovial effusion
Is septic arthritis usually mono-articular or poly-articular?
Mono-articular (90%)
What age groups is septic arthritis more common in?
Over 65 years (45%)
Also those very young, i.e. extremes of age
Is septic arthritis more common in males or females?
Males
Why is septic arthritis increasing so much in adults?
More joint replacements –> iatrogenic infections
What are the routes by which bacteria may reach the joint? (5)
- Hematogenous route
- Dissemination from osteomyelitis
- Spread from adjacent soft tissues
- Diagnostic or therapeutic measures (e..g injections)
- Penetrating damage or trauma
What are some causative organisms for septic arthritis - gram positive cocci? (2)
Staphylococcus aureus (most common) Streptococci - Pyogenes, Pneumoniae, Group B (e.g. in young children who haven’t had vaccines yet)
What are some causative organisms for septic arthritis - gram positive bacilli? (1)
Clostridium sp
What are some causative organisms for septic arthritis - gram negative cocci? (1)
Neisseria gonorrhea
What are some causative organisms for septic arthritis - gram negative bacilli? (4)
E. coli Pseudomonas aeruginoa Eikenella corrodens (human bites) Haemophilus influenza (paediatric before immunization)
Which is the most common causative organism for every age group apart from the 16-50?
What is the most common for 16-50s?
Staph aureus
Gonococcus
What are the predisposing factors for septic arthritis?
Pre-existing arthritis
Trauma/previous damage to the joint
Other disease e.g. affects blood supply to joint
Untreated systemic infection
Why do sickle cell, vascular insufficiency and diabetes predispose to septic arthritis?
Sluggish blood supply to bone and joints, bacteria isn’t flushed out and gets lodged.
Which joint is most commonly affected?
Knee
What other joints are also commonly affected?
Hip, ankle, elbow
What joints are infrequently affected?
Wrist, shoulder, fingers
What is seen on the lab results for septic arthritis?
Elevated ESR (or CRP)
Neutrophilia (esp. in children)
Positive blood culture in one to two thirds
Purulent synovial fluid
Synovial fluid - what is seen in SA?
Clumps of WBCs (mainly neutrophils, some macrophages)
Low glucose (<25mg/dL)
Gram stain positive in one-third (staph aureus)
What is seen on the radiology of SA?
Soft tissue swelling
Joint capsule distension
Destructive changes IF late (>2 weeks) - erosion of articular surface
What is seen on radiology of mycobacterial infection? (4)
joint space narrowing
effusion
erosions
cyst formation
What is seen on SA MRI?
Increased synovial effusion (increased signal)
Spread of bacteria into soft tissues
Bone marrow oedema – whiter signal, bacteria and effusions within bone itself
What are the differential diagnoses and how can they be ruled out?
Acute rheumatoid arthritis - symmetrical, infection is usually monoarticular
Gout - more likely in toe, infection more likely in knee
Chondrocalcinosis/pseudogout - x-ray
How is septic arthritis treated?
Drain synovial fluid and wash out joint with saline
Antibiotics IV 3-4 weeks (depends on Gram stain)
Reactive/Reiter’s arthritis is reactive/post-infectious and a sterile inflammatory process.
It is commoner in presence of…?
HLA-B27
Reactive arthritis occurs following an incidence of…? (2)
STI (chlamydia trachomatis)
Enteritis (salmonella, campylobacter etc)
Reactive arthritis usually has extra-articular symptoms - what are these?
Eye inflammation, lower back pain, scaly skin patches on genitalia, flaky skin patches on sole, sausage toes, diarrhoea, swelling in knee, heel or ball of foot
What is the pathogenesis of osteomyelitis?
Haematogenous spread or contiguous spread from an infected focus
Acute hematogenous osteomyelitis occurs primarily in…?
Children
Direct trauma and contiguous focus osteomyelitis is more common in…?
Young adults
Spinal osteomyelitis is more common in…?
Adults over 45
What are the predisposing factors of osteomyelitis? (2)
Impairment of immune surveillance, e.g.
malnutrition, extremes of age
Impairment of local vascular supply, e.g. diabetes mellitus (30-40% of patients), venous stasis, radiation fibrosis, sickle cell disease (0.36% of patients)
How common in osteomyelitis in neonates and children?
1: 1,000 neonates
1: 5,000 children
What are the clinical features of osteomyelitis?
Hematogenous long bone – abrupt onset of high fever (only 50% in children; less in adults)
Decreased limb movement, adjacent joint effusion (infants)
Hematogenous vertebral and chronic – insidious onset, vague complaints over 1 to 3 months
Local non-specific pain
Elevated neutrophil count (<50% of cases)
Elevated ESR
Haematogenous and contiguous spread osteomyelitis can progress to…?
Chronic osteomyelitis, causing local bone loss and persistent drainage through sinus.
What are rare complications of chronic osteomyelitis?
Squamous cell carcinoma and amyloidosis
What investigations are done for osteomyelitis?
Bone biopsy
Blood cultures (sinus tract culture NOT reliable)
Neutrophil count, ESR - monitoring response to treatment
Radiography (changes lag infective course by 2 weeks)
Isotope scan (shows active bone formation)
How is osteomyelitis managed?
Surgical debridement to remove dead bone (sequestrum)
Reconstruct bone (allograft or autograft)
New bone shell involucrum
Antibiotics for 4-6 weeks (at least 2wks IV)
Give some examples of antibiotics used for osteomyelitis.
Vancomycin cement beads Clindamycin (oral and foam) Flucloxacillin (gram positive) Piperacillin (broad spectrum, IV, IM only) Ciprofloxacin (broad spectrum)
Prosthetic bone and joint infection occurs in…?
Osseous tissue adjacent to prosthesis e.g. bone cement interface, bone contiguous with prosthesis (cementless devices)
Prosthetic bone and joint infection results from…? (3)
Local inoculation at surgery
Post-op spread from wound sepsis
Haematogenous spread
What are the risk factors for prosthetic bone and joint infection? (7)
prior surgery at site of prosthesis rheumatoid arthritis corticosteroid therapy diabetes mellitus obesity malnutrition old age
How can prosthetic bone and joint infection be prevented?
Before elective surgery, eliminate infected foci (e.g. bad teeth)
Use peri-operative antibiotics
Use laminar flow theatre ventilation
Surgical team wear exhaust ventilated body suits
Prophylaxis for subsequent interventions
Prosthetic bone and joint infection usually has a _____ onset with ______ joint pain and occasionally ______ development.
gradual
progressive
sinus
How many % of people with prosthetic bone and joint infections have changes on x-rays?
What are these changes? (5)
50% lucencies at bone-cement interface changes in component position cement fractures periostial reactions gas in joint
What else can be seen in prosthetic bone and joint infections investigations?
Radio-isotope scans
Elevated ESR, neutrophil count
Culture of biopsy/joint fluid
How are prosthetic bone and joint infections treated?
- Retain/replace prosthesis - best success (90%) if you remove the prosthesis, give antibiotics for 6 weeks and then re-implant the prosthesis
- Resection arthroplasty
- Suppressive long-term antibiotics
