Bone and Joint Infections Flashcards
What is osteomyelitis?
infection of the bone
What type of pathogen usually causes osteomyelitis?
bacteria
What are the three sources of infection in osteomyelitis?
haematogenous, direct inoculation (surgery, fracture) and local invasion (pressure ulcer, periodontal disease, sinus disease)
Why is the metaphyseal epiphyseal junction the site where osteomyelitis begins?
because the looped capillaries at this site have slow blood flow which can trap the bacteria
Why is osteomyelitis protected from an immune response?
there is a poorly developed mononuclear phagocyte system, there is poor penetration of WBCs and diminished immune mediators
Why is further blood supply to the site of osteomyelitis limited?
because of the pressure from the pus
What causes pain in osteomyelitis?
when the infection spreads to the subperiosteal space and lifts the periosteum
What is the difference in osteomyelitis between children and adults?
children still have blood vessels that cross the growth plate so the infection can spread to the epiphyses and the joint
What is septic arthritis?
infection of the joint
What are the two most common pathogens of osteomyelitis?
staph aureus and strep pyogenes
What is a more likely pathogen of osteomyeletis after surgery or trauma?
coagulase negative staphylococci
What is a more likely pathogen of osteomyelitis in newborns and infants?
strep agalactiae (group B strep), Hib or gram negative bacteria
What is a more likely pathogen of osteomyeleitis post chicken pox?
strep pyogenes
What is a more likely pathogen of osteomyelitis after a sneaker penetration injury?
pseudomonas
What is a more likely pathogen of osteomyelitis in developing countries?
TB and Hib
What age group is most likely to have osteomyelitis?
children under 5
Which sex is more likely to have osteomyelitis?
boys
What are the clinical features of osteomyelitis?
fever, tenderness, pain, malaise, pseudoparalysis, swelling, decreased ROM, redness, heat
Which bones are most commonly affected by osteomyelitis?
long bones e.g. humerus, femur, tibia - because these are the fastest growing
What is the differential diagnosis of osteomyelitis?
septic arthritis, malignancy, cellulitis
How is osteomyelitis diagnosed?
clinical signs, X-ray, bone scan, MRI, blood culture, bone culture, pus aspirated from bone, elevated CRP and ESRq
How is x-ray used to diagnose osteomyelitis?
initially used to rule out fracture - after 2 weeks may be able to see periosteal lifting
Which is more sensitive - a bone scan or an MRI?
MRI
Which is more specific - a bone scan or an MRI?
bone scan
