Micro Final Flashcards
(29 cards)
what is osteomyelitis?
inflammation of bone, literally
though we usually mean infection of bone due to bacteria most often
key features of osteomyelitis?
inflammatory destruction of bone, new bone formed
risk factors for osteomyelitis?
trauma, diabetes, decubitus ulcers, IV drug use, surgery
what are the three ways infection can get into the bone?
spread from current infection into bone, direct innoculation, hematogenously
what locations do hematogenous spread happen in kids and adults?
kids - long bones
adults - vertebral bodies
significance of transphyseal vessel?
it closes at 18mo, so epiphysis normally protected in all but children - so kids can get in epiphysis, adults usually dont
classical hematogenous spread?
infection enters thru nutrient artery and seed metaphysis, cuases necrosis and abscess formation - this can spread to epiphysis and joint space in kids
how does the necrosis spread?
extends within the bone and then out thru compact bone where it raises periosteum from cortex
what is the necrosis and new bone formation called?
sequestrum, involcrum
how do you get the sequestrum?
the inflammatory pressure compresses the capillaries within haversian canals, so you get necrosis of bone
cut off for antibiotics vs. surgery?
if have bone necrosis, likely need surgery, if no necrosis, could potentially just use antibiotics
clinical presentation of osteomyelitis?
chills, fevers, sweats, lethargy, malaise, point tenderness, swelling and redness of tissue over bone, draining sinus
number one organism to cause it?
staphylococcus aureus
why does staph aureus do osteomyelitis so well?
has collagen adhesion protein
created a biofilm which inhibits clearance by immune system and penetration of antibiotics
what is the preferred method of imaging for osteomyelitis?
MRI (90%sens,80% spec) preferred
X-Ray (50% sens, 70% specific)
what is the problem with imaging for this?
if have trauma in addition, it will be very difficult to discriminate between trauma and infection
what are some diagnostic tools, are they good?
probe to bone, blood culture…not very good
definitive diagnosis? bone biopsy and culture in OR
when should you start antibiotics?
hold off as long as you can until you know the organism - until after biopsy
what parts of the body usually only need antibiotics?
vertebral bodies and terminal digits
why are joint infections hard to treat?
no blood supply there, hard to get antibiotics there
how do joints get infected?
hematogenous seeding
sometimes by penetrating trauma or complication of joint infection with corticosteroids
risk factors for joint infection?
other joint diseases, prosthetic joints, IV drug use, alcoholism, diabetes, cutaneous ulcer, immune suppression
clinical presentation?
chills, fever, swollen, red, painful joint, decreased joint mobility
***important: leukocytosis common (unlike in bone)
common joints to be affected?
knee, hip, ankle, elbow, wrist, shoulder
