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Terms in this set (73)
Contributors to bone infections
Invasive medical/surgical procedures
motor vehicle accidents
What is the most common cause of bone and joint infections?
and inflammation of bone marrow
--loosely used to mean infx in any part of bone
Who is at increased risk of osteomylitis?
Preschool children (50% of cases)
Sickle cell anemia pts
How does infection get to bones?
Direct implantation (trauma or surgery)
Hematogenous routes (nutrient arteries)
Contiguous (spread from nearby tissue)
Most common cause of heatogenous infxn in infants (<1yr)
Group B Strep: S. agalactiae
Most common cause of heatogenous infxn in children
Most common cause of heatogenous infxn in adults
Gram (-) rods
Osteomylitis associated with IV drug use
affects the cervical vertebrae especially
Osteomylitis associated with puncture wound in foot
Osteomylitis associated with pts with sickle cell dx
Osteomylitis associated with pts with prosthetic joints
Osteomylitis associated with animal bites or scratces
Why does salmonella have a higher incidence with sickle cell?
There is a deficiency of bactericidal activity against salmonella
The sickle cells tend to block the spleen and the small capillaries. This leads to ischemia and localization of salmonella
How does biofilm help bacteria cause osteomylitis?
the biofilm allows the bacteria to grow and concentrate in a safe bubble:
--the biofilm protects the bacteria from host leukocytes and even abx
Bacterial adherence depends upon what?
The biofilm is composed of what?
a glycocalyx biofilm
How do PMN's injure bone?
They try to contain the ifxn, but cannot
They release reactive oxygen species to try and kill the bacteria, but instead damage bones
How does inflammation play a role in osteomylitis?
The vascular response and bacterial toxins disrupt the local vascular supply
This limits the host response as abx and PMNs can't get to the infection
Creates an environment conducive for persistent bacterial growth
What is involucrum?
It is seen in pyogenous osteomylitis
it is a growth of new bone around the infxn of old bone
How does pus play a role in osteomylitis?
Pus accumulates as the PMN's fight off the infxn, but it builds up and spreads in to vascular channels
The increased pressure (due to pus) decreases blood flow
Eventually, the pressure builds and the cortex ruptures
Consequences of long-term osteomylitis?
Can become chronic,
leading to bone necrosis,
leading to sequestra
What are sequestra?
large, de-vascularized sections of bone
Acute osteomylitis develops...
days to weeks
Chronic osteomylitits develops...
may persist for years
Where do we see hematogenous osteomylitis?
In the children and elderly
(remember it travels along the arteries)
Where do we see contiguous osteomylitis?
from a nearby infxn, trauma, or surgery
Findings for acute osteomylitis
Can find bugs, PMNs, and congested vessels
can do a gram stain and see the actual bacteria
Findings for chronic osteomylitis
mostly mononuclear cells present (cleaning up debris)
Few organisms seen on staining (infnx is already deep and probably encapsulated)
granular tissue/fibrosis replaces bone
Why are kids so at risk for osteomylitis?
They enter through arteries to the metaphyseal capillaries
slow flow in the capillaries allows them to grow and set up shop
also escape due to endothelial gaps in the tips of vessels
There aren't any PMNs near the capillaries in the growth plate, so grow unrestricted
causes further obstruction and decreased lumen flow, further enhancing conditions for growth
bacteria adhere and proliferate to the cartilaginous matrix
Kids mainly get osteomylitis where?
In long bones:
(especially in the meaphyseal plate)
why is osteomylitis in neonates and infants so easy?
They have mainly cortical bone, which is comprised of woven bone. It is thin and porous, so it is easy to penetrate and spread
It leads to easy spread of infxn to the sub-periosteal region
no sequestra are found since there is no pressure-related necrosis
Why is there no pressure related necrosis in neonates and infants?
The bone is thin and easily ruptured, so pressure never builds high enough to tamponade the vessels
What is the result of infxn in neonates and infants?
The infxn easily spreads to the sub-periosteal region, eventually forming an abscess
stimulation of the periosteum leads to new bone growth (involucrum)
Where do we usually find osteomylitis in adults?
Why are long bones not usually involved in adults?
There are changes in vascular anatomy-
no more epiphyseal plates
no vessels to supply them
What is a tell-tale sign of osteomylitis in adults?
The infxn has spread from the disk in to the disc space and adjacent vertebral body
What if we see inflammation on a scan but the disk is not involved?
Then it is most likely some type of metastisis
Where is osteomylitis most commonly found in the spine?
How do we rule out a metastatic bone lesion?
We look to see if it involves two adjacent vertebral bodies and the disk
How do UTIs cause osteomylitis?
The Batson veins are valveless and connect the deep pelvic veins and the thoracic veins.
It creates a route for bacteria to travel
What are the Batson veins?
A series of valve-less veins that connect the pelvic and thoracic veins
they drain the inferior bladder and prostate and connect to the internal vertebral plexus
How does osteomylitis manifest in kids?
It's usually in long bones and acute
-soft tissue swelling
-difficulty bearing weight
If there is erythema/swelling over an osteomylitis infxn in kids, what do we expect?
That there is an extension of pus through the cortex
How do we differentiate between ostemylitis and septic arthritis?
Osteomylitis will not have any joint pain, whether active or passive
What is an insidious onset?
When a disease starts of slowly, often asymptomatically at first, then suddenly becomes symptomatic
How does osteomylitis present in adults?
Usually in the vertebrae
-low grade fever
-slowly worsening back pain
-pain increases over 2-3 mos
-pain is unrelieved by analgesics
-might see neurological fedicits
Neurological deficits are signs of _________ with osteomylitis.
Vertebral body collapse
What kind of bacterial infxn is seen with a closed fx?
Usually a single microbe is involved
What kind of bacteria is involved with an open wound fx?
Commonly polymicrobial as many pathogens are airborne
Process for infxn with a bone fx
The pt fxs bone, which is then immobilized
the bacteria begins to grow and set up while the limb is sequestered
pt regains mobility and pain reappears
wound can become erythematous with a possible disharge
Purulent sinusitis spreads to...
the frontal bone
Dental root infxn can lead to...
Why are diabetics at risk for osteomylitis?
They have inadequate vascularization and neruopathy
starts with an ulcer than burrows to the bone
Microbiology of diabetic sichemic osteomyelitis
S aureus is most likely
-mixed gram negatives
Dx for diabetic ischemic osteomyelitis
probe the ulcer and culture
imaging is useful to show extent of damage, but not for dx
Dx osteomyelitis in children
Rely upon blood cultures and empiric therapy
avoid culturing the metaphysial plate
Dx of osteomyelitis in adults
Gold standard- blood culture
Normal WBCs due to chronic nature
Deep tissue sample preferred if biopsy is done
If debriding a wound, take a sample
Peaks in 3-5days
Declines 1-2weeks after initiation of therapy
great indicator of effective treatment, most long-term
Peaks in 2d
Declines within 6hrs after initiation of therapy
early indicator of effectiveness
X-ray dx of osteomyelitis
50% of Ca loss must occur for changes to be noted
lucent lytic area is an early radiographic find
Especially useful in spine, pelvis, sterum
can guide needle biopsy
Dx soft tissue infxn via 3-stage:
Arterial and venous are positive
Negative on bone uptake
Dx of skeletal infxn via 3-stage
all 3 phases (arterial, venus, bone) are positive
includes the delayed 2-4hr phase
What can cause a non-specific positive 3rd phase in 3-stage scntigraphy?
Dx with MRI
great at detecing marrow abnormalities
best at vertebral
Tuberculosis vertebal osteomyelitis
Issue arises from host natural defense, bacteria produce no toxins
Distinguishing feature of TB osteomylitis
a relatively well-preserved inter-vertebral disk
Osteomylitis Rx in adults
Adequate tissue sample for culture
Specific ABX regimen for 4-6weeks
Consider surgery if abx fails or neurologic signs present
Osteomylitis therapy in children
Sample, if possible
begin EMPIRIC therapy
Rx for diabetic osteomylitis
Appropriate abx for 2-6weeks
consider revascularization before amputation
.... may need to amputate
Evaluation of clinical Rx
CRP/ESR levels and symptomatic improvement are the best indicators
How do we define "cured" for osteomyelitis?
resolution of signs and symptoms for >1yr
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