Wound, bone and joint infections

Question 1

What is the aetiology of surgical site infections?

Answer 1

Wound contamination

Question 2

List 4 organisms that cause surgical site infections

Answer 2

Staph aureus
E coli
Pseudomonas
Haemolytic strep

Question 3

What is the empirical treatment for surgical site infections?

Answer 3

Fluclozacillin

Question 4

Describe the aetiology of septic arthritis

Answer 4

Abnormal joint (eg RA) or immunosuppression and bacteraemia (eg in IVDU, diabetes)

Question 5

Which 2 organisms most commonly cause septic arthritis?

Answer 5

Staph aureus (46%)
Streptococci (22%)

Question 6

Which type of organisms are less commonly responsible for septic arthritis?

Answer 6

Various gram -ves eg Ecoli

Question 7

Briefly describe the pathophysiology of septic arthritis

Answer 7

Bug adheres to synovial membranes and proliferates in fluid

Question 8

How does septic arthritis present?

Answer 8

Fever

Red hot swollen joint (50% knee - unable to weight bear)

Question 9

What exactly causes damage to the joint in septic arthritis?

Answer 9

Host inflammatory response

Question 10

How is septic arthritis diagnosed? (Ix)

Answer 10

Blood culture before abx
Joint aspirate (>50,000 cells/mm^3)
Inflammatory markers
Imaging shows effusion

Question 11

What is the treatment for septic arthritis?

Answer 11

IV cephalosporin or flucloxacillin
Vancomycin if MRSA present
Drain joint

Question 12

Describe the aetiology of osteomyelitis

Answer 12

Infection introduced to bone either via bloodstream or injury exposing the bone
Local or haematogenous spread
May begin as Brodie abscess (subacute), progressing to frank osteomyelitis much later (years)

Question 13

What is the most common causative organism for osteomyelitis?

Answer 13

Staph aureus

Question 14

How does osteomyelitis present?

Answer 14

Pain
Fever
Localised swelling

Question 15

What are the appropriate investigations when diagnosing osteomyelitis?

Answer 15

MRI

Bone biopsy for culture/histology

Question 16

What is the treatment for osteomyelitis?

Answer 16

Long term IV antibiotics (PICC line often required)
Debridement - to remove sequestra and infected bone
Amputation may be necessary in extreme cases

Question 17

Describe the aetiology of prosthetic joint infection

Answer 17

Begins as either a local wound infection or a systemic bacteraemia (eg from a UTI)

Question 18

Which groups of organisms are commonly implicated in prosthetic joint infections?

Answer 18

Staph

Gram -ves (eg Enterobateriaceae)

Question 19

How do prosthetic joint infections present?

Answer 19

Pain
Failure of joint
Discharging sinus tract over the joint (ie unhealed scar)
Pt complains joint “was never right”

Question 20

How is a prosthetic joint infection diagnosed?

Answer 20

"Loosening" visible on radiology
Inflammatory markers (CRP>13.5 for knee, >5 for hip)
WCC in aspirate (>17,000/μl for knee, >4200/μl for any other joint)

Question 21

What is the treatment for a prosthetic joint infection?

Answer 21

Replace the joint - single/two stage revision

Use antibiotic-impregnated cement