Pathogenesis Of Bone Infection

Front 1

How can you tell infectious agents from tumors affecting the bone?

Back 1

serial radiographs
based on history, onset, location, number of lesions, species and age of patient

Front 2

Define osteomyelitis

Back 2

acute or chronic septic inflammation of the bone involving the compact and spongy bone

Front 3

Define epiphysitis

Back 3

inflammation of the epiphyseal region of the bone

Front 4

Define septic physitis

Back 4

hematogenous osteomyelitis of the growth plates of long bones

Front 5

What animals most commonly get septic physitis?

Back 5

foals and calves

Front 6

Define aseptic physitis

Back 6

metabolic disorder of the physes of immature horses
aka physeal dysplasia

Front 7

What causes aseptic physitis?

Back 7

rapid growth
high plane of nutrition
trauma

Front 8

What are the effects of aseptic physitis?

Back 8

angular limb deformities
self-limiting, terminates at physeal closure

Front 9

What is spndylitis?

Back 9

inflammation of the vertebrae

Front 10

What is diskospondylitis?

Back 10

inflammatory and proliferative bone lesion of the IV discs, endplates and spongiosa of the vertebral bodies

Front 11

What causes diskospondylitis?

Back 11

bacterial or fungal infection

Front 12

What animals are primarily affected by diskospondylitis?

Back 12

dogs

Front 13

Define osteophyte

Back 13

bony outgrowth from the surface of a bone

Front 14

Define enthesophyte

Back 14

type of osteophyte arising from an attachment of muscle/ ligament (enthesis)
covered by enthesis CCT

Front 15

define sequestrum

Back 15

fragment of infected, dead bone separated from viable bone tissue

Front 16

How are sequestra formed?

Back 16

granulation tissue formation with osteoclasts

Front 17

What disease commonly forms sequestra?

Back 17

chronic osteomyelitis

Front 18

define involucrum

Back 18

sclerotic wall of reactive bone
-attempts to isolate the infection by encircling a sequestrum

Front 19

define sinus tract and give the alternate name

Back 19

opening in the cortical surface of a bone allowing exudate and fragments of sequestrum to exit
aka cloaca

Front 20

What are the two patterns of osteomyelitis?

Back 20

hematogenous
implantation or mechanical introduction

Front 21

What animals have the highest incidence of hematogenous osteomyelitis?

Back 21

foals and calves

Front 22

Why do foals and calves have a high incidence of hematogenous osteomyelitis?

Back 22

raised in bacteria contaminated environments
depend on colostrum for protection

Front 23

What pattern of hematogenous osteomyelitis is seen in puppies and kittens?

Back 23

polyostotic

Front 24

What is a polyostotic pattern of disease?

Back 24

involvement of multiple long bones on metaphyseal side of the growth plate

Front 25

Why is there a polyostotic pattern of disease in puppies and kittens?

Back 25

no transphyseal blood vessels in immature small animals, so infective agents cannot cross to the epiphyseal side

Front 26

What pattern of hematogenous osteomyelitis is seen in foals and calves and why?

Back 26

mirror-image destruction on opposite sides of the physis
they have transphyseal blood vessels so infection can spread from metaphyseal side

Front 27

When do you see the "bone within a bone" radiographically?

Back 27

in young dogs the periosteum of the bone can dissect away due to inflammatory exudate
-entire bone shaft becomes a sequestrum!
-involucrum forms a cuff around the necrotic bone

Front 28

Why do microbes localize in the primary spongiosa and subchondral bone?

Back 28

dense vascular bed
end arterioles present
vascular loops trap particles
sinusoids sludge blood flow

Front 29

How is bone infection initiated?

Back 29

bacteria adhere to damaged endothelium
slime layer forms (better bacterial attachment)
biofilm is generated (better environment/protection for bacteria against immune system)
dead bone provides additional surface for bacterial expansion

Front 30

What is the purpose of currettage?

Back 30

disrupts biofilm so antibiotics are more effective

Front 31

What is the usual pattern of involvement for osteomyelitis caused by implantation?

Back 31

monostotic
-single point of entry for bacteria etc

Front 32

What are common portals of entry for implantation osteomyelitis?

Back 32

puncture wound
open fracture
orthopedic surgery
extension from surrounding soft tissue or joint

Front 33

What are the possible outcomes of an established focus of osteomyelitis?

Back 33

walling off of the agent (results in bone abscess)
diffuse spread (massive necrosis)
vascular invasion (spread to other organ systems)

Front 34

Formation of which things are a sign of attempts to contain an infection?

Back 34

sequestrum, involucrum, sinus tract

Front 35

What does acute supperative osteomyelitis look like histologically?

Back 35

purrulent inflammatory exudate
edema
congested marrow spaces
osteocytes pyknotic or missing
may contain hemorrhage

Front 36

What does chronic osteomyelitis look like histologically?

Back 36

macrophages, lymphocytes and plasma cells in exudate
destruction of dead/dying bone
reactive bone formation
disuse atrophy of viable elements
granulation tissue with osteoclasts
may have pockets of supperative exudate

Front 37

What is the end point of chronic osteomyelitis?

Back 37

replacement of original architecture with fibro-osseous tissue
walling off of damaged areas