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
Clinical presentation of children with acute long-bone osteomyelitis?
chronic infection?
- Acute
- fever
- chills
- pain
- redness & sweling localized ofver the site of infection
- limping or inabiltiy to walk
- Chronic
- swelling
- pain
- erythema
- fever is less common
Clinical presentation of acute spinal osteomyelitis?
Chronic?
- Acute
- back pain
- affects lumbar spine > thoracic spine > cervical spine
- IV users: cervical vertebra
- local tenderness
- reduced mobility and or spasms nearby muscles
- fever may or maynot occur
- some have nerve compression
- weak limbs
- paralysis
- significant neurological dysfunction
- Chronic - symptoms over longer duration of time
- swelling
- pain
- erythema
- fever is less common
What are the most common sources of hematogenous infections?
In what percent of patients is the primary focus found?
- sources
- urinary tract
- skin & soft tissue
- infected intravascular devices
- infective endocarditis
- 50% patients primary focus is found
How is osteomyelitis diagnosed?
- Diagnosed
- lab data can be useful – but nonspecific
- peripheral WBC may be normal
- erythrocyte sedimentation rate (ESR) is elevated
- esp in acute
- C-reactive protein is elevated
- usually made radiologically
-
Plain radiology
- __requires 2-3 weeks to become positive (30-50% loss bone calcium required)
- in vertebral, may take 6-8 weeks
- reasonable first step – more useful for subacute/chronic cases
- poorly defined area of radiolucency, periosteal elevatin, areas of demineralization, loss shart bony margin, soft tissue swelling, late stage areas of increased calcification
- “moth eaten” appearance
- __requires 2-3 weeks to become positive (30-50% loss bone calcium required)
-
Plain radiology
- CT scan
- more sensitive than pian X-ray
- helpful to guide needl ebiopsy in vertebral osteomyelitis
- MRI
- detect early changes (3-5 days of dz onset)
- intraosseous and oft tissue abscesses, sone surrounding edema, joint effusions & joint involvement
- more expensive
- Gadolinium-based contrast improve diagnositic quality
- detect early changes (3-5 days of dz onset)
- lab data can be useful – but nonspecific
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
How do you diagnose the microbiology of osteomyelitis infections?
- during acute presntation, 2-3 blood samples should be obtained for culture
- blood cultures are positive in only some cases
- in adults, bone biopsies should be obtained for aerobin and anaerobic cultures
- gram stain & histopathologic evaluation
- with positive blood cultures, bone biopsy is not necessary
- in children, deep tissue samples of long bones are not obtained b/c the risk to damage the growth plate
Which groups of people are at risk for osteomyelitis to develop secodary to a contiguos infection?
Describe this general progression
- acute purulent frontal sinusitis spreadign to frontal bone (uncommon)
- dental root infectin or periodontal disease spreading to mandible (anaerobes)
- previous radiation that comprises the gingiva
- deep-seated pressure sores spreadign to underlyign bone, usually the sacrum (anaerobes)
- vascular insufficiency
- cellulitis of diabetic feet
- vascular insufficiency
- epidural abscess
- septic arthritis
- process
- infection & inflammation first destroy the periosteum or articular surface before it accesses the bone
- first cortex, then medullary cavity
- infection & inflammation first destroy the periosteum or articular surface before it accesses the bone
What is diabetic foot osteomyelitis & what are predisposing factors that can lead to this condition?
Clinical presentation?
Common etiological agents?
- infections usually begin w/ split in the skin or ulceration
- microorganisms multiply & the host tissues induce an inflammatory response
- infection can progress to deep tissues, joints & bones
- predisposing factors
- neuropathy (nerve dysfunction)
- person will not feel pain
- peripheral vascular disease leading to tissue hypoxia
- immunopathy (hyperglycemia impair leukocyte function)
- neuropathy (nerve dysfunction)
- Presentation
- typical signs inflammtion (erythea, edema, warmth, tenderness, pain or induration
- secondary signs: foul odor, non-purulent discharges, delayed wound healing
- Etiological agents (polymicrobial)
- S. aureus (most common)
- other gram (+) cocci (Streptococci, S. epidermidis)
- gram (-) rods (E. coli, Klebsiella pneumonia, Proteus mirabilis, P. aeruginosa) and anaerobes
What factors determine an infection develops from direct implantation in the bone?
What are the most frequent causes & etiological agents responsible for direct implantation osteomyelitis?
- Factors
- causative event
- extend of hemorrhage
- tissue fragmentation
- necrosis
- open bone fractures
- staphylococci and aerobic gram-negative bacilli
- swelling, fever, pain
- bone exposed durign surgery
- penetration of shrapnel or othopedic hardware
- staphylococci and aerobic gram-negative bacilli
Why are people with sickle cell more susceptible to osteomyelitis? What are the common etiological causes?
- sickle cell disease causes a chronic hemolytic anemia
- bacterial infections of bones & joints are common in children and adults with SCD due to reduced splenic function & impaired complement activity
- etiologicla agent
- Salmonella spp. (serovars Typhi and Paratyphi) is most common
- possibly due to occlusion of capillaries of bowel leading to patchy ischemic infarction & presence of salmonella and other bacteria in the bloodstream
- S. aureus
- gram negative enteric bacteria
- Salmonella spp. (serovars Typhi and Paratyphi) is most common
Whta is the most common spread of mycobacterial osteomyelitis (tuberculosis osteomyelitis)
Areas of the body most likely effected?
Symptoms?
Treatment?
- hematogeneous spread is more common
- most affect areas in order of prevalance
- spine
- hips
- knees
- Presentation
- insidious symptoms over a period of months to years
- low-grade fevers, weight loss, pain mild to severe, swelling, local warmth without erythema, muscle spasms and atrophy, limitation of range of motion, spine deformity, and soft tissue masses (due to cold abscess)
- insidious symptoms over a period of months to years
- Treatment
- combination multidrug therapy and surgery
Check this out
Check this out
Check this out
