Bone and Joint Infections

Question 1

What is osteomyelitis?

Answer 1

infection of the bone

Question 2

What type of pathogen usually causes osteomyelitis?

Answer 2

bacteria

Question 3

What are the three sources of infection in osteomyelitis?

Answer 3

haematogenous, direct inoculation (surgery, fracture) and local invasion (pressure ulcer, periodontal disease, sinus disease)

Question 4

Why is the metaphyseal epiphyseal junction the site where osteomyelitis begins?

Answer 4

because the looped capillaries at this site have slow blood flow which can trap the bacteria

Question 5

Why is osteomyelitis protected from an immune response?

Answer 5

there is a poorly developed mononuclear phagocyte system, there is poor penetration of WBCs and diminished immune mediators

Question 6

Why is further blood supply to the site of osteomyelitis limited?

Answer 6

because of the pressure from the pus

Question 7

What causes pain in osteomyelitis?

Answer 7

when the infection spreads to the subperiosteal space and lifts the periosteum

Question 8

What is the difference in osteomyelitis between children and adults?

Answer 8

children still have blood vessels that cross the growth plate so the infection can spread to the epiphyses and the joint

Question 9

What is septic arthritis?

Answer 9

infection of the joint

Question 10

What are the two most common pathogens of osteomyelitis?

Answer 10

staph aureus and strep pyogenes

Question 11

What is a more likely pathogen of osteomyeletis after surgery or trauma?

Answer 11

coagulase negative staphylococci

Question 12

What is a more likely pathogen of osteomyelitis in newborns and infants?

Answer 12

strep agalactiae (group B strep), Hib or gram negative bacteria

Question 13

What is a more likely pathogen of osteomyeleitis post chicken pox?

Answer 13

strep pyogenes

Question 14

What is a more likely pathogen of osteomyelitis after a sneaker penetration injury?

Answer 14

pseudomonas

Question 15

What is a more likely pathogen of osteomyelitis in developing countries?

Answer 15

TB and Hib

Question 16

What age group is most likely to have osteomyelitis?

Answer 16

children under 5

Question 17

Which sex is more likely to have osteomyelitis?

Answer 17

boys

Question 18

What are the clinical features of osteomyelitis?

Answer 18

fever, tenderness, pain, malaise, pseudoparalysis, swelling, decreased ROM, redness, heat

Question 19

Which bones are most commonly affected by osteomyelitis?

Answer 19

long bones e.g. humerus, femur, tibia - because these are the fastest growing

Question 20

What is the differential diagnosis of osteomyelitis?

Answer 20

septic arthritis, malignancy, cellulitis

Question 21

How is osteomyelitis diagnosed?

Answer 21

clinical signs, X-ray, bone scan, MRI, blood culture, bone culture, pus aspirated from bone, elevated CRP and ESRq

Question 22

How is x-ray used to diagnose osteomyelitis?

Answer 22

initially used to rule out fracture - after 2 weeks may be able to see periosteal lifting

Question 23

Which is more sensitive - a bone scan or an MRI?

Answer 23

MRI

Question 24

Which is more specific - a bone scan or an MRI?

Answer 24

bone scan

Question 25

What is the treatment of osteomyelitis?

Answer 25

flucloxacillin to treat the gram positive causes

Question 26

What is the treatment of osteomyelitis in newborns or unimmunised?

Answer 26

flucloxacillin and cefotaxime

Question 27

What is the treatment of osteomyelitis caused by MRSA?

Answer 27

vancomycin