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Flashcards in L 71 Osteomyelitis Deck (12):

What is osteomyelitis?

Progressive infection of bone
Results in inflammatory destruction, followed by new bone formation
3 Categories:
1) Secondary to a contiguous focus of infection
2) Secondary to a contiguous infection assoc with vascular insufficiency-diabetes
3) Hematogenous spread of infection, primarily long bones of kids, spine of adults, flat bones of adults often IV drug related


Gram (+) bac causing osteomyelitis

*S. aureus-all ages
Coagulase-neg staph
-Staph epidermidis
Staph saprophyticus
GBS Strep agalactiae-neonates
Strep pneumonia-older infants, children, adults


Gram (-) bac causing osteomyelitis

Salmonella-sickle cell
Serratia marcescens-IV drugs
E coli-neonates
Pseudomonas aeruginosa-iv drug or punctures
Kingella kingae-aerobic, coccobacillus, usually in pairs, shown up because we are now able to culture it, normal microbiota, colonizes posterior pharynx, RTX toxin, Type IV pili adhesin responsible for twitching motility


Staph aureus virulence factors

MSCRAMMS: microbial surface components-clumping factor, FnBP A&B binds to fibronectin, binds natural and unnatural materials like metal implants in body
Staph can be taken up by cells such as osteoblasts and be hidden from the immune system and cause chronic osteomyelitis
Protein A: binds Fc portion of antibodies and prevents opsonization
Enterotoxins-SEA and SEB


Staph biofilm makeup and purpose

Made of eDNA, polysaccharides, proteins
Creates thick layer that antibodies and antimicrobials have hard time penetrating


Pathogenesis of hematogenous esteomyelitis

Blood origin of the bacteria
As the blood vessels enter the diaphysis of the bone they split and run to the metaphysis where they loop and the blood slows down. At this point, the bacteria escape the bone and establish abscesses.
Inflammatory exudates increase intramedullary pressure and eventually ruptures the periosteum, periosteal blood interrupted leading to necrosis.
Leads to dead bone fragments-sequestrum
New bone called involucrum


Acute osteomyelitis

Infection of bone prior to development of sequestra
Slow development with osteomyelitis, faster with fractures or prostheses
Gradual onset of symptoms over days
Dull pain over the site
HEET, fevers, rigors
May present as septic arthritis: spreading of infection from metaphysis into the joint capsule knee, hip, shoulder


Chronic osteomyelitis

After development of sequestra
Formation of an involucrum
Local bone loss
Sinus tracts
Pain, erythema, edema
Sometimes assoc with draining sinus tract

Deep or extensive ulcers on feet that fail to heal after several weeks of appropriate care, especially over bony prominence, diabetic patients


Hematogenous vs contiguous osteomyelitis

Hematogenous is monomicrobic
Contiguous can be either poly or monomicrobic


How to differentiate between osteomyelitis and bone tumor on radiograph

Osteomyelitis has a penumbra sign=a distinct border around the abscess that is high in signal intensity on radiograph


Osteomyelitis diagnosis

Symptoms, bone biopsy
Radiographic abnormalities followed by biopsy taken from the bone and not the superficial lesions
Response to empiric therapy


Osteomyelitis treatment

Debridement of necrotic therapy
Antimicrobial therapy parentally
Continue until debrided bone is covered by vascularized soft tissue
Negative Pressure Wound Therapy