ICL 8.11: Bone and Joint Infection Flashcards
(47 cards)
what is osteomyelitis?
an infection of the bone and bone marrow
infection of bone leads to destruction and new bone formation** –> you’ll form a scar that will look abnormal and you’ll see it in an x-ray
mostly bacterial, rarely fungal (candida)
leading cause of amputations in US
what are the types of osteomyelitis?
- adult vs. pediatric
- acute vs. chronic
- contiguous vs. hematogenous
what are the parts of a bone during osteomyelitis?
there’s normal bone and in the middle there’s dead bone called sequestrum
there’s new bone formation trying to happen around the dead bone and also a sinus tract for the fluid from the dead bone to drain
why does osteomyelitis cause amputations so often?
the sequestrum CANNOT be penetrated by IV or antibiotics so this is why amputations are so common; you have to cut the limb off to get rid of the dead bone
what is hematogenous osteomyelitis?
contiguous osteomyelitis occurs when the microorganisms are introduced into bone through the blood –> usually due to injection drug use
in children you see it in long bones (metaphysis most commonly)
with adults, you see it in vertebrae
what is contiguous osteomyelitis?
contiguous osteomyelitis occurs when the microorganisms are introduced into bone by trauma, nosocomial contamination following surgical procedure and extension from adjacent soft tissue infection
young individuals = trauma, surgery
older = decubitus ulcers, infected total joint arthroplasties
diabetic foot and vascular insufficiency related
what are the clinical manifestations of acute osteomyelitis?
dull pain, gradual onset over days
probably won’t see too many changes in x-rays; changes in bone will be more subtle
easier to treat
what are the clinical manifestations of chronic osteomyelitis?
pain + sinus tract
harder to treat
when should you suspect osteomyelitis?
- probe to bone = when you see an opening, you should probe the wound to see if you can feel the bone and if you can you should suspect osteomyelitis
- chronic deep ulcers should raise suspicion of osteo
- erythrocyte sedimentation rate of over 70 mm/h (not specific; not diagnostic)
- abnormal x-ray result
what things would rule out osteomyelitis?
- negative MRI result - but remember, the first 2 weeks you might not see any changes so this isn’t 100%
- WBC and platelets can be normal; sometimes bone infection aren’t accompanied by soft tissue infection so you won’t have any systemic symptoms like fever
what do you do if a patient with osteomyelitis can’t have an MRI?
ex. if someone has a pacemaker
nuclear medicine studies can instead be helpful = technetium bone spa, indium or technetium tagged WBC scans
these are very sensitive but not very specific
what does the x-ray of someone with osteomyelitis look like?
like a bulge in the bone = callous formation
you might possibly see a black area in the middle of the bone too which would be the sequestrum! (dead bone)
35 year old with no medical problems suffer accidental gunshot would to the left tibia. fracture is comminuted and requires multiple surgical interventions, fasciotomy for compartment syndrome, external fixation, eventually skin graft. 4 weeks after discharge the patient present with drainage from surgical site and a fistulous tract that can be probed down to bone. he is not febrile, WBC is normal, CRP and ESR are normal. what would you do next?
hold antibiotics, debried the area and obtain a bone biopsy, start antibiotics postop
don’t start with broad spectrum antibiotics unless they have systemic symptoms
how do you know which bacteria are causing an osteomyelitis infection?
you need a BONE biopsy!!
superficial (ulcer/sinus tract) cultures are not reliable –> the exception is if Staph aureus grown from a sinus tract, it correlates well with presence of Staph in bone
no antibiotics before culture UNLESS patient has systemic symptoms
what bacteria often causes contiguous osteomyelitis?
many times polymicrobial
- diabetic foot = S. aureus, Group B strep, Pseudomonas
- postoperative/trauma = S aureus, coagulase negative staph
what bacteria often causes hematogenous osteomyelitis?
almost always monomicrobial
staphylococci or enteric gram negatives and pseudomonas
which bacteria often causes osteomyelitis in sickle cell patients?
still staph aureus but also a lot of salmonella!
like if salmonella is causing osteomyelitis, it’s probably in a sickle cell patient
which bacteria more rarely cause osteomyelitis?
- brucella
2. bartonella henselae
what should you be worried about if a diabetic has necrosis of the foot
probably have coronary heart disease too if they have ischemia of the foot
antibiotics will NOT take care of this; amputation is probably the only solution
what are the complications involved with a diabetic foot?
- vascular compromise is common
- high glycemias impair healing and infection makes diabetes difficult to control – vicious cycle
- small wounds can become huge problems rapidly
- infections are polymicrobial
- debridement is frequently needed
which bacteria should you target with a diabetic foot ulcer?
target Staph aureus, Group B strep and pseudomonas
what is a charcot foot?
neuropathic arthropathy
it’s a condition causing weakening of the bones in the foot that can occur in people who have significant nerve damage (neuropathy); the bones are weakened enough to fracture, and with continued walking, the foot eventually changes shape = you lose the arch of your foot and the feet look like hobbit feet
fractures in the foot due to weight bearing that eventually protrude from the foot and cause wounds that look like ulcers
acute charcot foot fractures can be hard to differentiate from cellulitis and osteomyelitis because there’s a lot of swelling and maybe even fevers that could look e like cellulitis
what is hematogenous vertebral osteomyelitis?
corkscrew anatomy of vessels feeding adult vertebral bone have turbulent flow which can lead to bacterial infections
fracture /trauma can predispose patients to vertebral osteomyelitis (abnormal architecture)
usually involves 2 adjacent end plates and the disc in between
lumbar > thoracic > cervical
what is contiguous vertebral osteomyelitis?
more commonly due to an external cause like from a decubitus ulcer, polymicrobial and restricted to cortical bone
whenever the tissue doesn’t heal well, you have higher chance of bacteria infecting it and eventually getting to the bone too and causing osteomyelitis
rarelyyy internal source like from the aorta, esophagus, bowel
