lecture 6 - bone & joint infections

Question 1

What is osteomyletis?

Answer 1

Inflammatory process of bone, secondary to infection

Question 2

Is osteomyletis a primary or secondary infection?

Answer 2

secondary

Question 3

What are the 3 classification of osteomyelitis, based on duration?

Answer 3

acute, sub-acute, chronic

Question 4

What are the 2 routes of infection in osteomyelitis?

Answer 4

haematogenous (from the blood), exogenous (from outside of the bone)

Question 5

What is haematogenous osteomyelitis?

Answer 5

secondary bone infection arising from blood borne bacteria from another source of infection

Question 6

What are the 2 key host responses to osteomyelitis?

Answer 6

pyogenic/purulence (pus production), granulomatus (granuloma formation)

Question 7

What is the most common route of infection for osteomyelitis in children?

Answer 7

Haematogenous

Question 8

Is haematogenous osteomyelitis generally polymicrobial or monomicrobial?

Answer 8

Monomicrobial

Question 9

Why do children usually develop the haematogenous form of osteomyelitis?

Answer 9

They have vascular stasis (slow moving, convoluted vessels) at their growth plates which allows bacteria to more readily enter the bone

Question 10

What are the 2 causes of exogenous osteomyelitis?

Answer 10

direct inoculation of the bone, contiguous (spread from local infection)

Question 11

How does direct exogenous osteomyelitis usually arise?

Answer 11

trauma (compound fracture), surgery

Question 12

What disease increases the risk of contiguous exogenous osteomyelitis, and why?

Answer 12

Diabetes - poor circulation in the feet can lead to infection that spreads to the bone

Question 13

Is exogenous osteomyelitis generally polymicrobial or monomicrobial?

Answer 13

polymicrobial

Question 14

What is the key bacteria that most commonly causes osteomyelitis across all age groups?

Answer 14

Staphylococcus aureus

Question 15

What are the risk factors for developing osteomyelitis?

Answer 15

immunosupression (diabetes, steroids, cancer, asplenia), age (children & elderly), peripheral vascular disease (smoking, diabetes), injecting drug uses, chronic joint disease, recent surgery/trauma

Question 16

Where does osteomyelitis typically develop in children?

Answer 16

metaphysis/growth plates of long bones

Question 17

What is the clinical presentation of osteomyelitis in children?

Answer 17

severe pain, oedema, erythema, pseudoparalysis, fever, nausea, vomiting

Question 18

What are the potential complications of osteomyelitis?

Answer 18

septic arthritis, dvt (deep vein thrombosis), sepsis, metastatic infection, recurrent osteomyelitis, altered bone growth, fracture

Question 19

What condition can be caused by the spreading of osteomyelitis to the joints?

Answer 19

septic arthritis

Question 20

What are the consequences of inflammation in osteomyelitis?

Answer 20

increased pressure diminishes blood supply leading to ischaema & necrosis, osteolysis (bone destruction)

Question 21

What is the term for breakdown in bone structure?

Answer 21

osteolysis

Question 22

What can occur in osteomyelitis when pus formation causes pressure and eruption to the skin?

Answer 22

sinus formation

Question 23

What are the pathological features of chronic osteomyelitis?

Answer 23

sinus, sequestrum, involucrum

Question 24

What is a sequestrum in osteomyelitis?

Answer 24

Focus of devitalised/dead bone, caused by necrosis

Question 25

What is an involucrum in osteomyelitis?

Answer 25

Formation of healthy bone over a sequestrum (area of dead bone)

Question 26

What are the 6 key diagnostic tools for diagnosing osteomyelitis?

Answer 26

1.) aspiration of pus for gram stain/culture 2.) bone biopsy 3.) blood culture (for haematognenous osteomyelitis) 4.) blood count for leukocytosis, raised CRP 5.) imaging (CT, X-ray, MRI) 6.) bone scans

Question 27

What class of osteomyelitis can often be detected with blood cultures?

Answer 27

haematogenous osteomyelitis

Question 28

What are the features of a blood count with osteomyelitis?

Answer 28

Leukocytosis (particularly high neutrophil count), raised CRP

Question 29

What imaging technique is best for early detection of osteomyelitis?

Answer 29

Bone scan - scintigraphy (also MRI)

Question 30

What is the initial treatment for osteomyelitis?

Answer 30

IV empiric broad-spectrum antibiotics

Question 31

What is the most common antibiotic first prescribed for osteomyelitis?

Answer 31

Flucloxacillin - because most infections caused by Staph aureus infections

Question 32

Why must antibiotic treatment change from empiric once the cause is known?

Answer 32

Changing to narrow spectrum antibiotics avoids drug resistance

Question 33

What is the surgical treatment for osteomyelitis?

Answer 33

debridement - removal of damaged/infected tissue, amputation

Question 34

What is a Brodie’s Abcess?

Answer 34

Localised region of osteomyelitis forming an abscess

Question 35

Are Brodie’s abscess acute, sub-acute or chronic?

Answer 35

Sub-acute or chronic - may persist for years until symptoms develop

Question 36

What is the treatment for sub-acute osteomyelitis, such as Brodie’s Abscess?

Answer 36

long course antimicrobials, surgical debridement

Question 37

Is chronic osteomyelitis typically monomicrobial or polymicrobial?

Answer 37

Polymicrobial

Question 38

What is septic arthritis?

Answer 38

pathogenic invasion of a joint causing arthritis

Question 39

What is septic arthritis characterised by?

Answer 39

colonisation of synovial fluid, inflammation, joint effusion (swelling), synovial membrane erosion

Question 40

What bacteria most commonly causes acute septic arthritis?

Answer 40

staph. aureus

Question 41

What bacteria is the most common cause of acute septic arthritis in young sexually active people?

Answer 41

Neisseria gonorrrhoeae

Question 42

What pathogens typically cause chronic septic arthritis?

Answer 42

HIV, rubella, TB, syphilis, fungi (candida)

Question 43

What bacteria typically causes early onset (<3 months post-op) septic arthritis following joint surgery/replacement?

Answer 43

staph. aureus

Question 44

What mechanism of infection occurs in s. epidermidis septic arthritis following joint surgeries?

Answer 44

biofilms

Question 45

What are the risk factors for developing septic arthritis?

Answer 45

damaged joints, joint replacement surgery, injecting drug use, immunosupression, age

Question 46

What are the clinical symptoms of septic arthritis?

Answer 46

inflammation/swelling (joint effusion), arthralgia (joint pain)

Question 47

What are the routes of entry for pathogens causing septic arthritis?

Answer 47

direct innoculation (surgery, trauma, injection), infection of adjacent tissues (e.g. osteomyelitis), haemotogenous spread (in blood)

Question 48

What are the complications of septic arthritis?

Answer 48

sepsis, osteomyelitis, joint destruction

Question 49

What are the treatments for septic arthritis?

Answer 49

IV empirical antibiotics, aspiration/drainage, debridement

Question 50

What is reactive arthritis?

Answer 50

Autoimmune disease in joints following an infection such as STI or gastroenteritis

Question 51

What STI typically causes reactive arthritis?

Answer 51

Chlamydia

Question 52

What triad of symptoms are typically present in reactive arthritis?

Answer 52

urethritis/cervicitis of UGT, uveitis/conjunctivitis of eyes, arthritis of large joints/sacroilieum

Question 53

What is the treatment for reactive arthritis?

Answer 53

anti-inflammatory/immunsuppressant drugs if unresolved