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LOCO 2 > Bone and Joint Infection > Flashcards

Bone and Joint Infection Flashcards

1
Q

Septic arthritis is a common…?

How many people per 100,000 does it affect in the UK?

A

Destructive athroplasty

8 per 100,000

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2
Q

How does septic arthritis usually develop?

A

Follows haematogenous spread

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3
Q

Acute septic arthritis is usually…?

A

Pyogenic

Chronic is usually non-pyogenic

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4
Q

What are the signs/symptoms of acute septic arthritis?

A

Mild in 60-80% of cases
Temperature >39 degrees in 1/3 of cases
Limited joint movement
Synovial effusion

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5
Q

Is septic arthritis usually mono-articular or poly-articular?

A

Mono-articular (90%)

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6
Q

What age groups is septic arthritis more common in?

A

Over 65 years (45%)

Also those very young, i.e. extremes of age

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7
Q

Is septic arthritis more common in males or females?

A

Males

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8
Q

Why is septic arthritis increasing so much in adults?

A

More joint replacements –> iatrogenic infections

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9
Q

What are the routes by which bacteria may reach the joint? (5)

A
  1. Hematogenous route
  2. Dissemination from osteomyelitis
  3. Spread from adjacent soft tissues
  4. Diagnostic or therapeutic measures (e..g injections)
  5. Penetrating damage or trauma
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10
Q

What are some causative organisms for septic arthritis - gram positive cocci? (2)

A 
Staphylococcus aureus (most common)
Streptococci - Pyogenes, Pneumoniae, Group B (e.g. in young children who haven’t had vaccines yet)
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11
Q

What are some causative organisms for septic arthritis - gram positive bacilli? (1)

A

Clostridium sp

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12
Q

What are some causative organisms for septic arthritis - gram negative cocci? (1)

A

Neisseria gonorrhea

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13
Q

What are some causative organisms for septic arthritis - gram negative bacilli? (4)

A 
E. coli
Pseudomonas aeruginoa
Eikenella corrodens (human bites)
Haemophilus influenza (paediatric before immunization)
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14
Q

Which is the most common causative organism for every age group apart from the 16-50?
What is the most common for 16-50s?

A

Staph aureus

Gonococcus

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15
Q

What are the predisposing factors for septic arthritis?

A

Pre-existing arthritis
Trauma/previous damage to the joint
Other disease e.g. affects blood supply to joint
Untreated systemic infection

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16
Q

Why do sickle cell, vascular insufficiency and diabetes predispose to septic arthritis?

A

Sluggish blood supply to bone and joints, bacteria isn’t flushed out and gets lodged.

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17
Q

Which joint is most commonly affected?

A

Knee

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18
Q

What other joints are also commonly affected?

A

Hip, ankle, elbow

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19
Q

What joints are infrequently affected?

A

Wrist, shoulder, fingers

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20
Q

What is seen on the lab results for septic arthritis?

A

Elevated ESR (or CRP)
Neutrophilia (esp. in children)
Positive blood culture in one to two thirds
Purulent synovial fluid

21
Q

Synovial fluid - what is seen in SA?

A

Clumps of WBCs (mainly neutrophils, some macrophages)
Low glucose (<25mg/dL)
Gram stain positive in one-third (staph aureus)

22
Q

What is seen on the radiology of SA?

A

Soft tissue swelling
Joint capsule distension
Destructive changes IF late (>2 weeks) - erosion of articular surface

23
Q

What is seen on radiology of mycobacterial infection? (4)

A

joint space narrowing
effusion
erosions
cyst formation

24
Q

What is seen on SA MRI?

A

Increased synovial effusion (increased signal)
Spread of bacteria into soft tissues
Bone marrow oedema – whiter signal, bacteria and effusions within bone itself

25
Q

What are the differential diagnoses and how can they be ruled out?

A

Acute rheumatoid arthritis - symmetrical, infection is usually monoarticular
Gout - more likely in toe, infection more likely in knee
Chondrocalcinosis/pseudogout - x-ray

26
Q

How is septic arthritis treated?

A

Drain synovial fluid and wash out joint with saline

Antibiotics IV 3-4 weeks (depends on Gram stain)

27
Q

Reactive/Reiter’s arthritis is reactive/post-infectious and a sterile inflammatory process.
It is commoner in presence of…?

A

HLA-B27

28
Q

Reactive arthritis occurs following an incidence of…? (2)

A

STI (chlamydia trachomatis)

Enteritis (salmonella, campylobacter etc)

29
Q

Reactive arthritis usually has extra-articular symptoms - what are these?

A

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

30
Q

What is the pathogenesis of osteomyelitis?

A

Haematogenous spread or contiguous spread from an infected focus

31
Q

Acute hematogenous osteomyelitis occurs primarily in…?

A

Children

32
Q

Direct trauma and contiguous focus osteomyelitis is more common in…?

A

Young adults

33
Q

Spinal osteomyelitis is more common in…?

A

Adults over 45

34
Q

What are the predisposing factors of osteomyelitis? (2)

A

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)

35
Q

How common in osteomyelitis in neonates and children?

A

1: 1,000 neonates
1: 5,000 children

36
Q

What are the clinical features of osteomyelitis?

A

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

37
Q

Haematogenous and contiguous spread osteomyelitis can progress to…?

A

Chronic osteomyelitis, causing local bone loss and persistent drainage through sinus.

38
Q

What are rare complications of chronic osteomyelitis?

A

Squamous cell carcinoma and amyloidosis

39
Q

What investigations are done for osteomyelitis?

A

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)

40
Q

How is osteomyelitis managed?

A

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)

41
Q

Give some examples of antibiotics used for osteomyelitis.

A 
Vancomycin cement beads
Clindamycin (oral and foam)
Flucloxacillin (gram positive)
Piperacillin (broad spectrum, IV, IM only)
Ciprofloxacin	(broad spectrum)
42
Q

Prosthetic bone and joint infection occurs in…?

A

Osseous tissue adjacent to prosthesis e.g. bone cement interface, bone contiguous with prosthesis (cementless devices)

43
Q

Prosthetic bone and joint infection results from…? (3)

A

Local inoculation at surgery
Post-op spread from wound sepsis
Haematogenous spread

44
Q

What are the risk factors for prosthetic bone and joint infection? (7)

A 
prior surgery at site of prosthesis
rheumatoid arthritis
corticosteroid therapy
diabetes mellitus
obesity
malnutrition
old age
45
Q

How can prosthetic bone and joint infection be prevented?

A

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

46
Q

Prosthetic bone and joint infection usually has a _____ onset with ______ joint pain and occasionally ______ development.

A

gradual
progressive
sinus

47
Q

How many % of people with prosthetic bone and joint infections have changes on x-rays?
What are these changes? (5)

A 
50%
lucencies at bone-cement interface
changes in component position
cement fractures
periostial reactions
gas in joint
48
Q

What else can be seen in prosthetic bone and joint infections investigations?

A

Radio-isotope scans
Elevated ESR, neutrophil count
Culture of biopsy/joint fluid

49
Q

How are prosthetic bone and joint infections treated?

A
  1. Retain/replace prosthesis - best success (90%) if you remove the prosthesis, give antibiotics for 6 weeks and then re-implant the prosthesis
  2. Resection arthroplasty
  3. Suppressive long-term antibiotics

LOCO 2 (28 decks)

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