MSK Infx

Question 1

adult –> osteomyelitis –> 2 MC route of spread?

Answer 1

• contiguous spread

- direct inoculation

Question 2

peds –> osteomyelitis –> MC route of spread?

Answer 2

hematogenous

Question 3

adult –> osteomyelitis –> MC org?

Answer 3

polymicrobial

Question 4

peds –> osteomyelitis –> MC org?

Answer 4

S. aureus

Question 5

what is sequestrum?

Answer 5

piece of necrotic bone –> sequestered from viable bone by granulation tissue –> can chronically harbor org –> nidus of recurrent infx

Question 6

what is involucrum?

Answer 6

living bone –> surround necrotic bone

Question 7

what is cloaca?

Answer 7

opening in involucrum

Question 8

what is sinus tract?

Answer 8

opening from infx to skin

Question 9

what is Brodie abscess?

Answer 9

subacute osteomyelitis –> central lucency –> peripheral sclerosis

Question 10

Brodie abscess –> ddx? (1)

Answer 10

osteoid osteoma

Question 11

peds –> hematogenous osteomyelitis –> MC location: epi/meta/dia-physis?

Answer 11

metaphysis

Question 12

<1yo infant –> osteomyelitis –> metaphysis –> can extend to where?

Answer 12

epiphysis

Question 13

chronic sinus tract –> complication?

Answer 13

squamous cell CA

Question 14

what is sclerosing osteomyelitis (osteomyelitis of Garre)?

Answer 14

uncommon form of chronic osteomyelitis –> bone sclerosis & thicken

Question 15

sickle cell osteomyelitis –> MC org? MC location: epi/meta/dia?

Answer 15

Salmonella –> diaphysis

Question 16

sickle cell –> Salmonella osteomyelitis in diaphysis –> ddx? (1)

Answer 16

bone infarct

Question 17

TB –> MC MSK infx?

Answer 17

Pott dz (TB discitis-osteomyelitis)

Question 18

adult –> discitis-osteomyelitis –> 3 causes?

Answer 18

• hematogenous spread
• spine surg
• GU infx –> epidural venous Batson plexus

Question 19

when can XR detect osteomyelitis changes?

Answer 19

10-14 days

Question 20

when can bone scan detect osteomyelitis changes?

Answer 20

24-48hr

Question 21

osteomyelitis –> bone scan?

Answer 21

positive on all 3 phases (flow, blood pool, delayed)

Question 22

cellulitis –> bone scan?

Answer 22

positive –> flow & blood pool

neg –> delayed

Question 23

osteomyelitis –> NM study with high sens & spec? finding?

Answer 23

WBC & sulfur colloid scintigraphy:

• WBC scan –> inc uptake
• sulfur colloid –> dec activity

Question 24

WBC scan –> NOT sens for which type of osteomyelitis?

Answer 24

spinal

Question 25

WBC scan –> 2 options of radiopharmaceutical?

Answer 25

• Indium-111-WBC

- Tc-99m-HMPAO-WBC

Question 26

differentiate: WBC scan –> Indium-111-WBC vs Tc-99m-HMPAO-WBC –> cons?

Answer 26

Indium-111-WBC:

• higher rad dose
• take 24h
• more image noise

Tc-99m-HMPAO-WBC:
- dissociate –> GU excretion

Question 27

when can MRI detect osteomyelitis changes?

Answer 27

3-5days

Question 28

osteomyelitis –> MRI findings?

• marrow
• cortex

Answer 28

• marrow –> edema + exudate –> T1 dark/T2 bright
• cortex –> inc signal –> infectious involve
• sequestrum –> nonenhancing bone

Question 29

septic arthritis –> gold standard for dx?

Answer 29

jt aspiration

Question 30

septic arthritis –> natural progression of dz?

Answer 30

rapid jt destruct –> ankylosis

Question 31

IVDA –> septic arthritis –> MC location? (2)

Answer 31

• SI

- acromioclavicular

Question 32

peds –> septic arthritis –> MC location? why?

Answer 32

hip

prox femoral metaphysis –> osteomyelitis –> contiguous spread