Infections

Question 1

Which is the most common joint in which septic arthritis develops?

Answer 1

The knee

Question 2

What is the most common bacteria to cause septic arthritis?

Answer 2

Staphylococcus aureus

Question 3

What is a common cause in young adults who are sexually active?

Answer 3

Neisseria gonorrhoeae

Question 4

Which bacteria is likely to cause septic arthritis in prosthetic joints?

Answer 4

Staph epidermidis

Question 5

What bacteria can cause septic arthritis?

Answer 5

• Staphylococcus aureus
• Neisseria gonorrhoeae
• Staph epidermidis
• Lyme disease
• Haemophilus influenzae - used to be high in children but now vaccine for it
• Gram-NEGATIVE bacteria e.g. E.coli or Pseudomonas Aeruginosa in the elderly or very young or those who are systemically unwell/ IV drug user

Question 6

What are the risk factors for septic artheritis?

Answer 6

• Prosthetic joints
• Diabetes mellitus
• Immunosuppression e.g. HIV
• Pre existing joint disease e.g. RA (10x)
• Low socioeconomic status
• Age <15 and >55
• IVDU (Intravenous Drug user)
• Osteomyelitis
• Intra-articular injection
• Recent joint surgery

Question 7

What are the signs for septic arthritis?

Answer 7

• Red hot swollen joint, usually just one joint

- Tachy and feverish

Question 8

What are the symptoms in the early infection with septic arthritis?

Answer 8

Wound inflammation/discharge, joint effusion, loss of function and pain

Question 9

What are the symptoms in the late disease?

Answer 9

• Presents with pain or mechanical dysfunction

- Fluid accumulation leading to joint destruction

Question 10

What would you see in the FBC?

Answer 10

Raised WCC

Question 11

What will you see in the joint aspiration?

Answer 11

• Fluid will be purulent/opaque/thick/pussy due to the high WCC in it

Question 12

What should normal joint aspiration fluid look like?

Answer 12

Yellow and quite thin

Question 13

What would you see in the xray in septic arthritis?

Answer 13

Not much unless you can see loosening or bone loss around a previously well fixed implant

Question 14

What is the main differential for crystal arthritis and what test therefore distinguishes the two?

Answer 14

Crystal arthritis and joint aspiration will show the crystals if not infection

Question 15

What is the pharmacological treatment for septic arthritis?

Answer 15

IV antibiotics for 6-12 weeks

Question 16

What type of bacteria are you targeting in septic arthritis?

Answer 16

Gram negative cocci

Question 17

What antibiotic would you give in the majority of cases?

Answer 17

IV flucloxacillin (targets most gram negative)

Question 18

What antibiotic would you give if allergic to penicillin?

Answer 18

Erythromycin

Question 19

What antibiotic would you give for MRSA?

Answer 19

Vancomycin

Question 20

What surgical options could be used in septic arthritis?

Answer 20

• needle aspiration to decompress the joint

- arthroscopic lavage

Question 21

What is osteomyelitis defined as?

Answer 21

Infection of bone

Question 22

Does osteomyelitis usually affect a single bone or multiple sites?

Answer 22

A single bone

Question 23

How can you categorise osteomyelitis?

Answer 23

• Acute haematogenous
• Secondary to continuous local infection
• Direct inoculation from trauma or surgery

Question 24

What does chronic osteomyelitis mean?

Answer 24

Bone necrosis (months to years)

Question 25

What organisms are likely to cause osteomyelitis?

Answer 25

- Staph aureus - commonest cause - Pseudomonas - E coli - Streptococci

Question 26

What two routes can the bacteria spread via?

Answer 26

Direct or haematogenous

Question 27

What does haematogenous spread mean?

Answer 27

Spreads to the bones via the blood

Question 28

What bones are most likely to be affected by haematogenous spread in adults and in children?

Answer 28

- Children - long bones | - Adults - vertebrae

Question 29

What is the necrotic bone referred to as?

Answer 29

The sequestrum

Question 30

What is new bone formation called?

Answer 30

Involucrum

Question 31

What is process that leads to new bone formation in osteomyelitis?

Answer 31

1. Inflammatory exudate in the marrow 2. Increased intramedullary pressure 3. Extension of exudate into the bone cortex 4. Rupture through the periosteum 5. Interruption of periosteal blood supply 6. Leaves pieces of seperated dead bone 7. New bone forms here

Question 32

What are the risk factors for osteomyelitis?

Answer 32

- Diabetes mellitus - IV drug user - Immunosuppression

Question 33

How does osteomyelitis present?

Answer 33

- Non specific pain at the site of infection - Fever, malaise, fatigue - Local inflammation - Wound drainage - Reduced range of movement

Question 34

What would you see on the blood test in osteomyeltistis?

Answer 34

Raised ESR/CRP and WCC

Question 35

What is the gold standard investigation for osteomyelitis?

Answer 35

Bone biopsy with culture. Only 50% of cases will show on a blood culture

Question 36

What would you see on the xray in osteomyelitis?

Answer 36

``` - cbone density changes aren't apparent for 10-14 days - Shows haziness and loss of - Subperiosteal reaction - Sequestrum and involucrum can be seen in later infection ```

Question 37

Why is an MRI better then an xray?

Answer 37

- Shows inflammation better | - Shows changes 3-5 days as well as soft tissue involvement

Question 38

What is the non-pharmacological treatment for osteomyelitis?

Answer 38

Bed rest if its spinal

Question 39

What is the pharmacological treatment for osteomyelitis?

Answer 39

- Flucoxicillin or vancomycin for 6 weeks

Question 40

What would you use if the infection was caused by TB?

Answer 40

Triple therapy

Question 41

What surgical therapy can be done?

Answer 41

- Debridement | - Hardware replacement or removal