48.osteomyelitis

Question 1

2 methods of causing osteomyelitis

Answer 1

1. hematogenous (metaphyseal region)2. contagious from surrounding soft tissues3. direct inoculation/posttraumatic (MOST COMMON)

Question 2

2 reasons why metaphyseal bone is prone to hematogenous spread of infection

Answer 2

1. sluggish blood supply (end arteriole loops)2. discontinuous capillaries (capillaries with gaps and incomplete basement membranes)allow easier passage of bacTbacteremia–>bacT translocation and embolize through the endothelial gaps –> lodge in bone in area inaccessible for host immune response.

Question 3

what artery supplies the inner two thirds of the bone cortex and and medullary cavity ?

Answer 3

nutrient artery—ascending and descending branches

Question 4

what is a major predisposing factor in the development of osteomyelitis

Answer 4

bone ischemia that can happen from inflammation, necrosis and resorption

Question 5

less aggressive vs more aggressive bone lesion with osteomyelitits

Answer 5

less aggressive–pushes periosteum away slowly–results in thickening of bonemore aggressive–lamellated appearance (onion like) wherein the bone is laid down in layers. Causes periosteum to be rapidly pushed away and leads to the development of calcified streaks perpendicular to the bone

Question 6

T/Fdogs and cats lack a transphyseal blood supply at birth

Answer 6

TRUEdogs and cats lack a transphyseal blood supply at birththus concurrent joint infections are uncommon

Question 7

60% of organisms isolated from bacterial osteomyelitits are…..

Answer 7

staph intermedius

Question 8

parts of sequestrum

Answer 8

1. sequestrum is central necrotic area of 2. surrounded by involucrum which is new bone/reactive bone (separated by radiolucent zone)3. opening in the involucrum through which material may escape is the cloaca (can form draining tracts)

Question 9

define biofilm

Answer 9

microbial derived sessile community in which bacteria are attached to a substrate or each other and embed themselves in a matrix and exhibit an altered phenotype

Question 10

4 stages of biofilm formation

Answer 10

1. reversible attachment2. irreversible attachment3 growth and differentiation4. dissemination or detachment

Question 11

T/ F microorganisms involved in a biofilm always adhere is the biomaterial/implant surface

Answer 11

FALSEmicroorganisms adhere to the conditioning film (adsorbed molecules from local tissues ontop of biomaterial); rarely to they adhere to the biomaterial itself

Question 12

how does a reversible adhesion in biofilm formation eventually become irreversible

Answer 12

made irreversible by the production of bacterially produced exopolysaccharides (GLYCOCALYX)this helps/assists cells to firmly attach

Question 13

T/FBacteria can reproduce inside a glycocalyx

Answer 13

TRUE

Question 14

three components of a biofilm

Answer 14

1. microorganism2. glycocalyx3. host biomaterial surface/conditioning film

Question 15

advantages of sessile microorganisms in a biofilm

Answer 15

1. ECM collects/concentrates nutrients2. evades host immune function3. resistance to Ab penetration

Question 16

3 ways that biofilm protects against Ab

Answer 16

1. filter/barrier to decrease penetration or perfusion of the AB2. bacT in bioiflm are sessile and quiescent and some drugs need actively reproducing/growing bacteria to kill3. harsh environment of biofilm (decr O2, dec pH, incr CO@) renders Ab less effective

Question 17

T/Ffracture instability will perpetuate the persistence of infection

Answer 17

True

Question 18

T/FAs opposed to hematogenous osteomyelitis, posttraumatic osteomyelitis is rarely a systemic disease

Answer 18

TRUEhematogenous osteomyelitis—SYSTEMICALLY illpost traumatic osteomyeltitis–local infection

Question 19

general considerations for treatment of osteomyelitis

Answer 19

1. culture (implants, necrotic bone) **aerobic, anaerobic2. additional fluid cultures if needed3. debride (remove implants, boney sequestra)4. establish drainage5. maintain stability/rigid fixation6. graft if needed7. +/- antibiotic impregnanted beads8. consider delayed closure9. Tx IV ab 5-7 days before PO drugs based on sensitivity

Question 20

length of duration of Ab impregnanted PMMA beads

Answer 20

usually minimum 4 weeks

Question 21

one vs two stage revision of a implant arthroplasty osteomyelitis

Answer 21

2 stage revision eradication 90%1 stage revision eradication 80%