Diseases of the Musculoskeletal System - Bone and Joint Infections (52)

Question 1

Heterogenous disease

Answer 1

Many different pathogens, anatomical sites, and clinical ages

Question 2

Infection of bone

Answer 2

Osteomyelitis

Question 3

Is osteomyelitis easy to treat and diagnose?

Answer 3

No, surgery is often needed

Question 4

Pathogenesis

Answer 4

1. Haematogenous
2. Contiguous-focus
3. Direct inoculation

Question 5

Haematogenous

Answer 5

Bacteria in the blood seed bone

Question 6

Examples of haematogenous spread

Answer 6

Endocarditis, infection from canular (more common in infants and children)

Question 7

Contiguous-focus

Answer 7

Spread from adjacent area of infection

Question 8

Examples of contiguous-focus

Answer 8

Foot ulcers in a diabetic foot

Question 9

Direct inoculation

Answer 9

Trauma or surgery

Question 10

Mader classification

Answer 10

Stage 1, 2, 3, 4 (not progression)

Question 11

Stage 1

Answer 11

Medullary - confined to medulla, necrosis medullary contents/endosteal surface (haematogenous) caught early

Question 12

Stage 2

Answer 12

Superficial - necrosis limited to exposed surface - periosteum (contiguous)

Question 13

Stage 3

Answer 13

Localised - full thickness destruction of cortical elements, left as an island lacks blood supply - dies, can’t deliver antibiotics (trauma, stage 2/3 evolving)

Question 14

Stage 3 treatment

Answer 14

Surgery to get rid of infected bone, debriding bone of pus and antibiotics

Question 15

Stage 4

Answer 15

Diffuse - extensive major reconstruction required, unstable bone

Question 16

Clinical presentation

Answer 16

Pain, soft tissue swelling, erythema, warmth, localised tenderness, reduced movement of affected limb, systemic upset uncommon (fever, chills, night sweats, rigors)

Question 17

Type of pain

Answer 17

Nocturnal, localised, progressive

Question 18

Presentation varies with

Answer 18

Age, type of infecting organism and location of infection

Question 19

Example

Answer 19

Tibia, superficial, erythema - common in babies, young children

Question 20

Causative organisms

Answer 20

• Staph aureus (60%)
• Strep A/B
• Enterococci
• Gram negative bacilli
• Anaerobes
• M. TB, Brucella

Question 21

Examples of Gram negative bacilli

Answer 21

Salmonella, Klebsiella, Pseudomonas aeruginosa (premature baresi, IVDU, sick cell)

Question 22

Diagnoses

Answer 22

Culture and histology of bone (biopsy/needle aspirate)

Question 23

C-reactive protein

Answer 23

Usually raised

Question 24

Therapy

Answer 24

IV antimicrobials +/- surgery (avoid empirical)

Question 25

Antibiotics penetrate well in bone

Answer 25

Clindamycin (staph cocci/staph aureus), Ciprofloxacin, Vancomycin, B-lactams and Gentamicin

Question 26

Treatment for S.aureus OM

Answer 26

Flucloxacillin IV

Question 27

Septic (infective) arthritis

Answer 27

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

Question 28

Classification for direct infection

Answer 28

Native (natural) joint infection vs Prosthetic (artificial) joint infection (early/late)

Question 29

Native joint infection, how do pathogens enter?

Answer 29

Via blood (haematogenous) or trauma (surgery/injection)

Question 30

Native joint infection, how does it facilitate seeding

Answer 30

Synovial tissue highly vascular and lacks a basement membrane

Question 31

Native joint infection, what does cartilage erosion cause?

Answer 31

Joint space narrowing, impaired function

Question 32

Native joint infection, predisposing factors

Answer 32

Rheumatoid arthritis, trauma, IVDU, immunosuppressive disease

Question 33

Prosthetic joint infection, how do pathogens enter?

Answer 33

Via the blood (haetogenous) during surgery/wound infection

Question 34

What provides surface for bacterial attachment in prosthetic joint infection?

Answer 34

Joint prosthesis and cement

Question 35

How does infection occur in prosthetic joint?

Answer 35

Polymorph infiltration > tissue damage instability of the prosthesis

Question 36

Prosthetic joint infection, predisposing factors

Answer 36

Prior surgery at the site of the prosthesis, rheumatoid arthritis, corticosteroid therapy, diabetes mellitus, poor nutritional status, obesity and extremely advanced age

Question 37

Septic arthritis clinical presentation

Answer 37

Joint (pain, swelling, tenderness, redness and limitation of movement) Systemic (fever, chills, night sweats)

Question 38

Duration of septic arthritis clinical presentation

Answer 38

Variable, influenced by site of infection, joint type and causative organism

Question 39

Causative organisms of septic joints

Answer 39

Bacteria, fungi (Candida), Viruses (Parvovirus B19, Rubella virus, Mumps virus - self limiting)

Question 40

Native joint causative organisms

Answer 40

Staph aureus, Strep (A,B,C,G), gram neg bacilli, H.influenzae, N.gonorrhoeae, N.meningitidis, anaerobes, mycobacteria

Question 41

Prosthetic joint infection

Answer 41

Staph. aureus, coagulase negative staph, enterococci, strep (A,B,C,G), anaerobes (peptostreptococci, peptococci), enterococci, gram negative bacilli, coryne bacteria, propionibacteria, bacillus, mycobacteria

Question 42

Examine joint aspirate

Answer 42

WCC (>40,000), Differential WCC (>75%), gram stain (35-65% positive), crystal examination (gout can mimic infection), culture, PCR (slow growing organisms - M.TB)

Question 43

Therapy for native joint infection

Answer 43

- Removal of pus - joint drainage washout - Empirical IV antimicrobial - Directed IV antimicrobial - Duration 2-4 weeks

Question 44

Therapy for prosthetic joint infection

Answer 44

- Removal of implant/replacement of some of elements (wash out) - Empirical IV antimicrobial - Directed IV antimicrobial - Duration 6 weeks

Question 45

Antibiotics for PJI

Answer 45

Flucloxacillin plus rifampicin for S.aureus