23. Bone and joint infections (Robson) Flashcards

1
Q

What is septic arthritis?

A

Inflammation to a joint caused by bacterial infection

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2
Q

Is septic arthritis typically mono or poly articular in nature?

A

Monoarticular - 90% of cases

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3
Q

Who does septic arthritis tend to occur in?

A

Tends to occur at either end of the age bracket - very young or very old
Poorer immune surveillance (older) or lack of immunisation (younger)

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4
Q

How does the presentation of acute and chronic septic arthritis differ?

A

Acute - usually be a mild fever i.e. pyrogenic

Chronic - this is a cold inflammation - no fever or signs of being unwell

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5
Q

Why can septic arthritis commonly occur at a growth plate?

A

Due to the tortuous course of the arteries here - can lead to a lodging of bacteria

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6
Q

What is the cause of septic arthritis?

A

Usually follows a haematogenous spread of e.g. infection from elsewhere

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7
Q

In what age group is septic arthritis most common and why?

A

Most common over the age of 50, especially over the age of 60 - these people are undergoing more procedures on their joints -greater risk of bacteria entering the joint

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8
Q

What are the five different ways that bacteria can enter the joint to form septic arthritis?

A
Haematogenous route - blood
Dissemination from osteomyelitits (bone)
Spread from adjacent soft tissues
Penetrating damage or trauma 
Diagnostic or therapeutic measures
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9
Q

What are the three most common gram positive organisms causing septic arthritis?

A

Staphylococcus aureus

Streptococci pyogenes
Streptococci pneumoniae

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10
Q

What is the most common gram negative organism causing septic arthritis?

A

Neisseria gonorrhoea

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11
Q

In which age group is neisseria gonorrhoea the most common organism for septic arthritis?

A

In the sexually active age group - 16-50year olds

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12
Q

What is the most common joint affected by septic arthritis and why?

A

Knee

Very big joint - high blood supply

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13
Q

Which joints can potentially be infected by septic arthritis?

A

ANY JOINT

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14
Q

How will the synovial fluid appear in septic arthritis?

A

Lumpy
Slightly cloudy
Slightly red
Presence of bacteria and neutrophils

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15
Q

What is the glucose level in someone with septic arthritis and why?

A

Glucose level will be reduced - the bacteria are using up the glucose for proliferation

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16
Q

Why is radiology not useful in the early stages of septic arthritis?

A

The infection is inside the joint - hidden initially as the calcification appears normal

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17
Q

When will radiological changes start to appear from septic arthritis?

A

After about two weeks

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18
Q

What might be seen radiologically in septic arthritis? x6

A
Soft tissue swelling
Joint capsule distension 
Joint space narrowing
Effusion
Erosion
Cyst formation
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19
Q

What can be seen on an MRI for septic arthritis?

A

Increased signal will signify increased synovial effusion

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20
Q

How is septic arthritis treated?

A

Drainage and washout of the joint to remove as much bacteria as possible
(NB. do not put anything else back in - the articular capsule will reproduce the synovial fluid)

Antibiotics - start with broad spectrum and then specific

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21
Q

Why is there swelling in septic arthritis?

A

Synovial effusion

22
Q

Other than the knee, what are the common joints affected by septic arthritis?

A

Hip, ankle, elbow

23
Q

What are the differential diagnoses for septic arthritis and how do you rule these out?

A

Acute RA - polyarticular so if presenting as monoarticular then not this
Gout - usually in the big toe
Pseudogout - looking for presence of chondrocalcinosis (calcification of the cartilage)

24
Q

What is reactive arthritits?

A

The joint is reacting to the presence of bacteria in the body - not necessarily in the joint itself

This is a sterile inflammatory process

25
Q

What genetic predisposition is associated with reactive arthritis?

A

HLA-B27

26
Q

What is Pott’s disease?

A

Form of TB outside of the lungs and in the vertebral joints i.e. the IV discs - bacteria lodged in the IV discs and bodies

27
Q

Which regions of the vertebrae are typically affected by Pott’s disease?

A

Lower thoracic and upper lumbar

28
Q

What is osteomyelitis?

A

Infection and inflammation of the bone

29
Q

What are the three main routes by which osteomyelitis can occur?

A

Haematogenous spread from an infection elsewhere in the body
Contiguous spread from another infected focus
Direct trauma

30
Q

Which route of osteomyelitis is more common in children?

A

Haematogenous spread

31
Q

Which route of osteomyelitis is more common in young adults?

A

Direct trauma

32
Q

How can osteomyelitis disrupt growth?

A

If the infection, once having entered the joint, spreads across the whole of the growth plate

33
Q

What are the predisposing factors for the development of osteomyelitis?

A

Impaired immune surveillance e.g. malnutrition, extremes of age
Impaired local vascular supply e.g. diabetes, venous stasis, sickle cell

34
Q

What is a Brodie’s abscess and why does this occur?

A

Walling off of localised bacteria in bone by formation of fibrous tissue and granulation tissue

35
Q

Why does a Brodie’s abscess occur?

A

The bone attempts to wall off and hide the bacteria from the rest of the bone so that the infection cannot spread

36
Q

When does a Brodie’s abscess typically occur?

A

In later stages of osteomyelitis

37
Q

How can a Brodie’s abscess be recognised on an x-ray?

A

There is a sclerotic ring around it

38
Q

How can you differentiate between a subchondral cyst and a Brodie’s abscess on an x-ray?

A

Subchondral cyst - at the EDGE of the bone margin

Brodie’s abscess - within the bone

39
Q

What is the main complication of chronic osteomyelitis?

A

Local bone loss and resulting damage to the soft tissues

40
Q

What is the relation of a squamous cell carcinoma to osteomyelitis?

A

Chronic, untreated osteomyelitis - can (rarely) result in the development of squamous cell carcinoma

41
Q

What is the main investigation used for osteomyelitis?

A

Bone biopsy - see if you can find the bacteria

42
Q

Why is a blood culture not useful for diagnosis of osteomyelitis?

A

The pathogen may not have gotten out of the bloodstream

43
Q

How is acute osteomyelitis treated?

A

Same as septic arthritis - washout and provision of antibiotics

44
Q

How is chronic osteomyelitis treated?

A

Surgical debridement to remove dead bone
Reconstruct the bone e.g. allograft or autograft
Antibiotics

45
Q

How long should antibiotics be provided for when treating osteomyelitis?

A

For 4-6 weeks

46
Q

What will be seen in the histology of a Brodie’s abscess?

A

Presence of neutrophils, macrophages and the bacteria

47
Q

ESR in septic arthritis is?

A

Raised

48
Q

Synovial fluid of septic arthritis described as? x2

A

Turbid

Purulent

49
Q

Two factors commonly predisposing to reactive arthritis are?

A

STI - chlamydia

Enteritis - salmonella

50
Q

Three presentations of osteomyelitis?

A

Abrupt fever - more common in children
Decreased limb movement
Local non-specific pain

51
Q

Two signs of osteomyelitis?

A

Elevated neutrophil count

Elevated ESR

52
Q

Two rare complications of osteomyelitis?

A

Squamous cell carcinoma

Amyloidosis