56 Bone and joint infections

Question 1

What are the three types of bone infection pathogenesis?

Answer 1

Haematogenous.
Contiguous focus (spread from adjacent area).
Direct inoculation.

Question 2

What are the four classifications of osteomyelitis?

Answer 2

I. Medullary (haematogenous).
II. Superficial (contiguous).
III. Localised: full thickness, stable.
IV. Diffuse: unstable bone.

Question 3

How does osteomyelitis present? (2 + 4).

Answer 3

Pain.
Reduced movement of affected limb.
(Soft tissue swelling, erythema, warmth, tenderness).

Question 4

Which organisms cause osteomyelitis? (7).

Answer 4

Staphylococcus aureus (60%)
Streptococci.
Enterococci.
Gram -ve bacilli.
Anaerobes.
Mycobacterium tuberculosis, Brucella (indolent spinal).

Question 5

Who gets gram -ve bacilli osteomyelitis? (3).

Organisms? (3).

Answer 5

Premature babies, IVDU’s, sickle cell.

Salmonella, Klebsiella, Pseudomonas aeruginosa.

Question 6

How is osteomyelitis diagnosed?

Answer 6

Gold standard: cultures + histology of bone biopsy.

Blood cultures +ve in 50%.

Question 7

What is C-reactive protein used for in osteomyelitis?

Answer 7

Monitor therapy response.

Limited diagnostic value.

Question 8

In general, how is osteomyelitis treated?

Answer 8

IV antimicrobials ± surgery.

Avoid empirical therapy.

Question 9

Which antimicrobials achieve acceptable levels in bone? (5)

Answer 9

Clindamycin.
Ciprofloxacin.
Vancomycin.
ß-lactams.
Gentamicin.

Question 10

What is the agent of choice for staph aureus osteomyelitis?

Answer 10

Flucloxacillin.

Question 11

Define septic arthritis:

Answer 11

Inflammatory reaction in a joint space caused by infection.

Question 12

What is the pathogenesis of a native joint infection?

Answer 12

Entrance via blood or trauma.

Synovial tissue is highly vascular and lacks basement membrane -> seeding.

Question 13

What are the predisposing factors to a native joint infection? (4).

Answer 13

Immunosuppressive disease.
Intravenous drug use.
Trauma.
Rheumatoid arthritis.

Question 14

What is the pathogenesis of a prosthetic joint infection? (3).

Answer 14

Prosthesis/cement provides base for infection.

Phagocytosis difficulty due to biofilm. Macrophages secreting enzymes causes joint instability.

Question 15

What are the predisposing factors to a prosthetic joint infection? (7).

Answer 15

Prior surgery.
RA.
Corticosteroid therapy.
Diabetes mellitus.
Poor nutrition.
Obesity.
Advanced age.

Question 16

How does septic arthritis present? (4 + 3).

Answer 16

Joint: pain, swelling, tenderness, redness, limited movement.
Fever, chills, night sweats.

Question 17

Which viruses can cause septic arthritis (3) and when?

Answer 17

Parvovirus B19, Rubella, Mumps.

As part of systemic illness.

Question 18

Which organisms cause septic arthritis? (5).

Answer 18

Staph aureus.
Streptococci.
Gram -ve bacilli.
Anaerobes: peptostreptococci, peptococci.
Mycobacteria.

Question 19

Which organisms specifically cause native septic arthritis? (3).

Answer 19

Haemophilus influenzae.
Neisseria gonorrhoea.
Neisseria meningitidis.

Question 20

Which organisms specifically cause prosthetic joint infection? (through contamination from skin) (5)

Answer 20

Coagulase negative staphylococci.
Enterococci.
Corynebacteria.
Propionibacteria.
Bacillus spp.

Question 21

Which test is used to exclude gout as a differential with septic joint infection?

Answer 21

Crystal examination.

Question 22

How is septic arthritis diagnosed? (4).

Answer 22

Joint aspirate exam:
Raised WCC > 75% polymorphs.
Gram stain.
Culture.
? PCR.

Question 23

How is native joint infection treated? (2).

Answer 23

Joint drainage/washout.

Empirical then directed IV antimicrobial therapy for 2-4weeks.

Question 24

How is prosthetic joint infection treated?

Answer 24

Removal or replacement of prosthesis.

Empirical then directed IV antimicrobial therapy for 6 weeks.

Question 25

Which antimicrobials are used for a prosthetic joint infection with S.aureus?

Answer 25

Flucloxacillin plus rifampicin.

Question 26

Which antimicrobials are used for a prosthetic joint infection with coagulase negative staphylococci?

Answer 26

Vancomycin IV plus rifampicin.