Osteomyelitis Flashcards
What is osteomyelitis?
under what conditions can it occur?
what is the major etiological cause?
progressive infection of the bone includign one or multiple parts
It can occur under direct trauma or large bacterial inoculum; more common in males than females
etiological agent: Staphylococcus aureus
What is the difference between acute and chronic osteomyelitis?
- acute
- clinical symptoms from day to weeks from the onset of illness (usually 2 weeks)
- infection occurring before the development of necrotic bone (sequestrum or sequestra)
- chronic
- clinical symptoms from several weeks, months and even years. Course is more indolent. Presence of sequestra
What is hematogenous osteomyelitis?
continuous osteomyelitis?
direct inoculation?
-
hematogeneous osteomyelitis
- bacteremic (blood) seeding from a distant site of infection. Only in half of patients the source is found
- most frequently occurs in children (long bones)
- __femur > tibia > humerus
- adults
- most comonly affects vertebrae
-
contiguous osteomyelitis
- spread to the bone from surrounding tissue and joints
- people with pressure ulcers or underlying diabetes
- spread to the bone from surrounding tissue and joints
-
direct inoculation
- because of trauma or surgery
- open fractures, bone reconstructive surgery, placing orthopedic hardware
- most frequent cause of adult long-bone osteomyelitis
- because of trauma or surgery
Predisposing factors for osteomyelitis?
- diabetes melitus & peripheral vascular disease
- open fractures
- bacteremia
- endocarditis
- intravenous drug use
- sickle cell disease
- chronic steroid use
- immunosuppression
- AIDS
- chronic joint disease
- presence prosthetic orthopedic device
What is the most common etiological cause of hematogeous in infants, children, and adults?
How many organisms are usually found per infection?
usually one organism
- infants (<1 year)
- S. aureus, group B streprococci (Streprococcus agalactiae), Escheria coli
-
Children (1-16 years)
- S. aureus, S. epidermidis, Streptococcus pyogenes (group A), gram negative rods (Pseudomonas aerguinosa, E. coli), Kingella kingae (children youner than 4, Haemophilus influenza type B: reduced incidence due to vaccination
- Kingella kingae: pharynx, gram negative short bacillus, fastidious – cultured chocolate or blood agar
-
Adults
- S. aureus, S. epidermidis, GNR, Mycobacterium tuberculosis
- MRSA is increasing isolated from patients
What is the most common etiological cause of contiguous osteomyolitis?
How many organisms are usually found per infection?
usually polymicrobial
- microbiology depends on primary site of infection
- S. aureus, S. epidermidis, GNR, anaerobes (Prevotella spp., Bacteriodes spp.)
What is the most common etiological cause of osteomyolitis for the following special cases?
- Sickle Cell disease
- IV drug users
- Animal bite/screatches
- patients with prosthetic joints
- puncture to foot while wearing sneakers
- patietns with genitourinary tract infections
- Sickle Cell disease
- Salmonella spp., S. aureus; usually long bones followed by the vertebrae
- IV drug users
- S. aureus, Pseudomonas aerugiinosa, usually cervical vertebrae
- Animal bite/screatches
- Pasteurella multocida
- patients with prosthetic joints
- P. aeruginosa, S. aureus
- puncture to foot while wearing sneakers
- P. aeruginosa, S. aureus
- patients with genitourinary tract infections
- E. coli, Klebsiella spp.
What species of fungi are capable of causing osteomyelitis?
- Histoplasma capsultatum
- Blastomyces dermatidis
- Coccidoides immitis
- Aspergillus spp. (indwelling intravenous catheters, IV drug useres, immunocompromised patients)
- Candida spp. (indwelling intravenous catheters, IV drug users; immunosuppressed patients)
clinical presentation and outcome varies according to specific pathogen, location of the infection, and host factors
What species of helminths and viruses are capable of causing osteomyelitis?
- helminths
- echinococcus granulosus, formation of hydatid cysts
- viruses
- osteomyelitis is an uncommon clinical problem
Why is S. aureus a common causative agent of osteomyelitis?
- present in nose & respiratory tract in 1/3 of people
- surface proteins that mediate adherence to host’s components
- collagen, fibronectin, laminin, and elastin
- enzymes that degrade host’s components (hyaluronidase, proteases) & toxins such as hemolysins
- biofilms
- can invade osteoblasts & survive in a metabilically incactive state
Describe hematogeneous spread in children
- Usually first occurs in the metaphysis b/c vascular characteristics
- children are susceptile due to abundance of blood vessels w/ leaky endothelium that end in capillary loops
- blood flow is slow here
- Bacteria multiplication triggers an inflammatory response
- formation of puss
- cytokines promote clot formation –> leading to ischemia & necrosis
- Exudate under pressure is forced into bony cortex where it can lift or rupture through the periosteum
- subperiostel abscess can develop
Why is osteomyelitis so dangerous in young infants?
- in young infants <1 yr, the disease can result in permanent growth impairments & higher incidence of septic arthritis
- the infection can extend frommetaphysis to the epiphysis– & destruction of epiphyseal cartilage & secondary ossification center
- with age, metaphyseal cortex is thicker & periosteum is dense helping to contain the infection
- delay in treatment can lead to chronic infection & formation of sequestra (piece of necrotic bone separated from normal bone)
- stripping of the periosteum stimulates new bone formation (involucrum) beneath the periosteum *& surrounding sequestrum
Where can the infection spread from the metaphyseal space during osteomyelitis in children?
- epiphysis, joint space, subperiosteal space, soft tissue & shaft of the bone
Describe hematogeneous spread in adults
- adults rarely develop osteomyelitisin in the long bone b/c at maturity, the cartilage in the growth plate is replaced by bone & blood flow ceases
- if it happens, its b/c trauma or surgery
- vertebra become more vascular with age
- vertebral arteries bifurcate & supply two adjacent vertebral bodies
- usually affects 2 vertebral bodies & intervertebral disc
- disc space narrows
- formation of epidural abscess
- if not treated, progressive destruction of bone & disc
- can become a chronic infection
How does osteomyelitis develop chronicity?
Risk factors?
Consequences/Symptoms of chronic infection?
- acute infection fails to resolve & persists as a chronic infection
- Risk factors
- delay in diagnosis
- extensive bone necrosis
- abbreviated antibiotic therapy
- inadequate surgial debriement
- weekend host defenses
- organisms may ramain viable in necrotic tissue inaccessible to immune response & antibiotics
- acute flare-ups are usually spontaneous – may occur after years of dormancy
- sinus tract may drain purulent material
- increases in pain
- inflammatory markers
- more serious
- pathologic fracture
- endocardidis
- sepsis
- malignancy
What features of osteomyelitis are indicated by the white arrows?
What imaging modality is being used?
- Plain radiograph
- fragmentation of the distal interphalngeal joint
- arrowheads outline expected location of medial margin of proximal phalyngeal bone
- multifocal areas of cortical destruction & ill-defined lytic ares found through distal first metatarsal & both first toe phalanges
What features of osteomyelitis are indicated by the white arrows?
- can see destruction in adjacent vertebral bodies & intevening disc
- anterior portion of bodies are most severely affected
Check this out
Check this out
Check this out
