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Osteomyelitis (causative pathogens (hematogenous osteomyelitis (Staph…
Osteomyelitis
causative pathogens
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Contiguous spread
Also most commonly S aureus, but higher prevalence of polymicrobial infections than hematogenous
Can also involve streptococci, Staph epidermidis, E coli, Pseudomonas, and anaerobes
Associated with diabetes
Often polymicrobial, including gram-negative bacilli
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IV Drug users
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more commonly gram-negatives (Pseudomonas, klebsiella, enterobacter, serratia)
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Diagnosis
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ESR, C-reactive protein (most sensitive), and WBC (the only lab abnormalities) --> these are used for monitoring therapy
Culture to identify bacteria if osteomyelitis is suspected - important to determine which antimicrobial therapy to start
bone aspiration or bone biopsy to determine an accurate bacteriologic diagnosis and if there is an abscess present
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Pathophysiology
Direct Inoculation
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These infections most commonly occur after internal fixation of a hip fracture or femoral or tibial shaft fracture
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Contiguous
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common sites: femur, tibia, mandible
Chronic
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Common in foot infections of patients with diabetes if proper surgery is not performed to debride a wound
Hematogenous
bacteria are seeded within the metaphysis as the nutrient arteries of the long bones divide within the medullary canal of the bone into small arterioles
these end in hairpin turns near the growth plate and flow into veins of much wider diameter, that drain the medullary cavity
The infection is initiated within the bend of the arterioles where there is considerable slowing of blood flow in the hairpin capillary loops
This sludging of blood flow allows bacteria in the bloodstream to settle and initiate inflammatory response
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Children > 12-18 months
epiphyseal growth plate prevents the infection from spreading into the epiphysis and the adjacent joint space
Adults
Periosteum is tightly bound to the cortex which is thick
- This prevents the infections from expanding outside the intramedullary space
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Treatment
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empiric treatment
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kids >4 yrs
vancomycin 60 mg/kg/day IV, clindamycin 40 mg/kg/day or cefazolin 100-150 mg/kg/day IV
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IV drug abusers
vanc 15mg/kg every 12 hours plus ciprofloxacin 750 mg PO BID, ceftazidime or cefepime 2 g IV every 8 hor
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Duration of therapy
For children, some evidence suggests courses as short as 10 days if their CRP is normalized (but such a short course could be risk)
IDSA guidelines recommend 8 weeks for MRSA-associated osteo (esp with vertebral osteo) OR gram-negative infections
If signs/symptoms are not resolved, tx should be extended
For adults, usually 4-6 weeks
For vertebral osteomyelitis, minimum treatment course of 6 weeks due to lower blood flow in pts over 50
If hardware is retained following a prosthetic joint infection, 3-6 months
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Clinical Presentation
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Vertebral osteomyelitis
nonspecific symptoms (constant back pain, fever, or night sweats, and weight loss)
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