Bone And Joint Infections Flashcards
What are the causes of the rise in bone and joint infections?
Aging populations Epidemics of obesity/diabetes Invasive medical/surgical procedures High speed motor vehicle accidents Physical and aggressive sports
What is the most common cause of bone and joint infections?
Staphylococcus aureus
What is osteomyelitis?
Inflammation of the marrow bone
Loosely used to refer to infection in any part of the bone
Involves periosteum, cortical bone, medullary cavity
What is the epidemiology of osteomyelitis?
Most often in preschool children (refuse to stand on one leg)
Twice more likely to occur in males than females
Occur with foot puncture at a much higher in diabetics
What are the routes of entry of osteomyelitis?
Contiguous- spread from nearby soft tissue infection
Direct implantation- trauma/surgery
Hematogenous route via nutrient arteries
What are the causes of osteomyelitis in infants less than 1 year?
Staphylococcus aureus
Streptococcus agalactiae (group B strep)
E.Coli (inhalation during child birth)
What are the causes of osteomyelitis in children?
Staphylococcus aureus
Streptococcus pyogenes (Group A)
Haemophilus influenzae
What are the causes of osteomyelitis in adults?
Staphylococcus aureus
Staphylococcus epidermis
Mycobacterium tuberculosis
Gram negative rods
What are the causes of osteomyelitis in IV drug user?
Pseudomonas aeruginosa
Staphylococcus aureus
Mostly affect cervical vertebra compare to lumbar vertebra in other cases
What is the pathogenesis of osteomyelitis?
Microbes seed bones
Infection occurred if microbe adhere to bone or implant
Adherence depends one bone fibrinogen, laminin, collagen and bacterial adhesins
Bacteria produce a glycocalyx biofilm after adherence
Biofilms prevent bacterial killing by host and antibiotics
PMN release reactive oxygen intermediates, toxins and enzymes that damage bones
What are the types of osteomyelitis?
Acute- develops over days to weeks
Chronic- over weeks, months and may persist for years
Hematogenous-primarily in children and elderly
Contiguous- from a nearby infection, trauma, surgery
What are the characteristics of acute osteomyelitis?
Bugs
PMNs
Congested and thrombosed blood vessels
Less than 6 weeks
What are the characteristics of chronic osteomyelitis?
Presence of necrotic bone and mostly mononuclear cells
Few organisms to be seen on staining
Granulation/fibrosis replaces bone resorbed by osteoclasts
What are the characteristics of osteomyelitis in children?
Usually hematogenous and involves a single bone
Usually involves long bone
Bugs enter via enter artery to metaphyseal capillary loops
Sharp turns at distal metaphysis slows blood flow
Abrupt onset, fever, soft tissue swelling
If only osteomyelitis no pain on active or passive motion of the joints
What are the characteristics of osteomyelitis in neonates and infants?
Thin cortical bone composed primarily of woven bone
Stimulation of periosteum leads to new bone growth (involucrum)
What are the characteristics of hematogenous osteomyelitis in adults?
Rarely involves long bone due to changes in vascular anatomy
More common in persons older than 45 years
Source isn’t always evident
Most common in vertebrae
Involvement of adjacent vertebral bodies and intervening disc rules out metastatic bone lesion
Lack of valve provides a route for the spread of infection
What are the characteristics of vertebral osteomyelitis?
Usually in elderly
Low grade fever and progressive worsening of back pain
Usually unrelieved by analgesics
Wha are the characteristics of osteomyelitis after bone fractures?
Close fracture- one bug
Open fracture- often polymicrobial
As patient begins to bear weight pain reappears
What are the characteristics of diabetic foot osteomyelitis?
Poor vascularity and neuropathy
Starts with an ulcer (lower extremities)
No pain.inflammation due to vascularization
Fever in usually absent
How to diagnose osteomyelitis ?
In Children-avoid biopsy may damage the growth plate, rely on blood cultures and empiric therapy
In adults- blood culture is the gold standard, deep tissue sample is preferred
Elevated ESR and CRP levels are non specific
ESR peaks in 3-5 days, declines 1-2 week after therapy
CRP peaks in 2 days declines in day 6th after therapy
What is the therapy for osteomyelitis ?
Adequate tissue sample for culture
Specific antimicrobial regimen (4-6 weeks)
Empiric therapy is usually started in children
In diabetics- amputation or debridement may be required
What is septic arthritis?
Arthritis that results from infection of one or more joints by a microorganism usually bacterial
Most commonly caused by S.aureus and Neisseria gonorrhea
Acute- involves a single joint and destructive to articular cartilages
examine inflamed joints promptly for infectious arthritis
What is the epidemiology of septic arthritis?
More common in children than adults
High incidence in age group younger than 15 and older than 55
In infants- usually involves hip
In children- most commonly affects knee
IV drugs users- sternoclavicular and sacroiliac joints
What are the routes of bacterial entry?
Hematogenous route Dissemination from osteomyelitis From adjacent soft tissue infection Diagnostic/therapeutic measures Penetrating injuries
