Bone and Joint Infections

Question 1

Osteomyelitis

Answer 1

Infection of the bone

Question 2

3 mechanisms of how bone infection may be brought about

Answer 2

Haematogenous- bacteria in the blood seed bone
Contiguous focus-spread from adjacent area of infection
Direct incoculation-trauma or surgery

Question 3

Stage 1 of osteomyelitis and likely cause

Answer 3

Medullary-necrosis of medullary contents- haematogenous

Question 4

Stage 2 of osteomyelitis

Answer 4

Superficial-necrosis limited to exposed surfaces

Question 5

Cause of stage 2 superficial osteomyelitis

Answer 5

Contiguous- Diabetic foot ulcer, pressure sores

Question 6

Complications of stage 3

Answer 6

Necrosis- no blood supply- can’t treat with antibiotics. Surgery required to cure

Question 7

Stage 3 osteomyelitis

Answer 7

Localised- full thickness cortical sequestation, stable before and after debridement

Question 8

Stage 4 osteomyelitis

Answer 8

Diffuse- extensive, unstable bone

Question 9

describe the pain with osteomyelitis

Answer 9

localised pain, not relieved with resting and progressive

Question 10

Clinical presentation of osteomyelitis

Answer 10

Pain
Soft tissue swelling
Erythema
Warmth
Localised tenderness
Reduced movement of affected limb
Systemic upset uncommon (fever, chills, night sweats)

Question 11

Most common causative organism of osteomyelitis (60%)

Answer 11

Staph A

Question 12

6 main causative organisms of osteomyelitis

Answer 12

Staph A
Stretococci
Enterococci
Gram -ve bacilli
Anaerobes
M. TB

Question 13

Gold standard diagnostic procedure for osteomyelitis

Answer 13

Cultures and histology of bone biopsy/needle aspirate

Question 14

Name 4 diagnostic tests for osteomyelitis

Answer 14

Gold standard
Blood cultures
Superficial swabs
C-reactive protein

Question 15

When would you give empirical antimicrobial therapy in osteomyelitis?

Answer 15

When signs of sepsis

Question 16

Which 5 antibiotics have acceptable penetrance in bone?

Answer 16

Clindamycin
Ciprofloxacin
Vancomycin
Beta-Lactam
Gentamicin

Question 17

What is the treatment of choice for Staph A. osteomyelitis

Answer 17

Flucloxacillin IV

Question 18

How are antibiotics usually administered in osteomyelitis?

Answer 18

IV

Question 19

Septic arthritis

Answer 19

Inflammatory reaction in joint space (arthritis) caused by infection, resulting from direct invasion of the joint

Question 20

2 classifications of septic arthritis

Answer 20

Native (natural) joint infection

Prosthetic (artificial) joint infection

Question 21

2 ways in which organisms enter the joint in native joint infection

Answer 21

Haematogenous or trauma

Question 22

How does synovial tissue facilitate ‘seeding’?

Answer 22

Highly vascular and lacks a basement membrane

Question 23

Predisposing factors for native joint infection

Answer 23

RA
Trauma
IVDU
Immunosuppressive disease

Question 24

Prognosis for native joint infection

Answer 24

Not fatal but severe lack of function if not treated

Question 25

How do organisms enter the joint in prosthetic joint infections?

Answer 25

Haematogenous | During surgery or following wound infection after surgery

Question 26

Why are prosthetic joints susceptible to infection?

Answer 26

Cement provides a surface for bacterial attachment

Question 27

How does infection affect the joint in prosthetic infection?

Answer 27

Polymorph infiltration results in tissue damage instability of the prosthesis

Question 28

How does infection affect the joint in native infection?

Answer 28

Cartilage erosion causes joint space narrowing/impaired function

Question 29

Predisposing factors to prosthetic joint infection

Answer 29

``` Prior surgery at site RB Corticosteroid therapy DM Poor nutritional status Obestiy Age ```

Question 30

Clincial presentation of septic arthritis

Answer 30

``` Pain Swelling Tenderness Redness Limitation of movement Systemic upset ```

Question 31

Causative organisms of septic arthritis

Answer 31

Bacteria Fungi e.g. candida Viruses e.g. parovirus B19, rubella, mumps (usually self limiting part of systemic illness)

Question 32

Name for group A streptococcus

Answer 32

Strep. pyogenes

Question 33

Causative organisms for native joint infections

Answer 33

``` Staph A Streptococci A, B, C, G Gram -ve bacilli Neisseria gonorrheoae Neisseria meningitidis ```

Question 34

Causative organisms for prosthetic joint infection

Answer 34

Staph A Coagulase -ve staphylocoi Enterococci Gram -ve bacilli

Question 35

What do you look for in an examination of joint aspirate?

Answer 35

``` High total WBCs Lots of polymorphs Gram stain- not particularly reliable Crystal examination- gout can mimic infection Culture PCR e.g. M.TB ```

Question 36

Therapy for native joint infection

Answer 36

Removal of purulent material -joint drainage/washout Empirical followed by directed antimicrobial therapy (after microbiological samples have been taken) 2-4 weeks treatment

Question 37

Difference in therapy for prosthetic joint infection, compared to native

Answer 37

Removal of implant/replacement of some elements if unstable

Question 38

2 stage revision procedure

Answer 38

Take out implant and replace with cement and antimicrobials before replacing

Question 39

Treatment for Staph A in prosthetic joint infection

Answer 39

Flucoxacillin with rifampicin (Staph A. easily becomes resistant to rifampicin, so must always be used in combination for Staph A)

Question 40

Duration of treatment for prosthetic joint infection

Answer 40

6 weeks, IV to oral switch