Bone and Joint Infections

Question 1

• What is discitis?

* If infectious, what pathogen usually causes discitis?

Answer 1

Infection of inflammation in the intervertebral discs

S. aureus

Question 2

• Why is infectious discitis difficult to manage?

Answer 2

You cant drill a hole and remove the bit of infected bone because the vertebral column would collapse. Instead, you need a long course of intensive antibiotics.

Question 3

• Why don’t old bones heal as well as a young person’s bones?

Answer 3

They’re less vascular

Question 4

• Why are bugs so resistant when they find their way to a prosthesis (e.g. plate/screws)?

Answer 4

They form a biofilm, so can evade the immune system and antibiotics.

Question 5

• How can diabetes lead to osteomyelitis?

Answer 5

1. Diabetics have sensory neuropathy in their feet, creating an ulcer
2. This ulcer can grow and cause contiguous osteomyelitis of the foot bones
3. The foot is relatively avascular so there is decreased local immunity

Question 6

• If you look at an ulcer and see bone, what can you assume?

Answer 6

That there is osteomyelitis (95% chance)

Question 7

• What X-ray sign do you see in chronic osteomyelitis?

What is a sequestrum?

• What is an involucrum?

Answer 7

1. Periosteal elevation (see image)
2. Lytic areas (due to the sequestrum)
3. Sclerotic areas (due to the involucrum)

The bit of dead bone resulting from osteomyelitis. The chronic inflammation associated with osteomyelitis causes necrosis of the bone

New bits of bone try and form to heal up the sequestrum, forming an involucrum

Question 8

• Most common pathogen for osteomyelitis in children and adults?

Answer 8

Staph aureus

Question 9

• Most common pathogen for osteomyelitis in newborns?

Answer 9

Group B streptococcus (from the vagina)

Question 10

• What is the usual pathogen for septic arthritis?

* What is the treatment?

Answer 10

Staphylococcus aureus

? Emergency surgical drainage and washout

Question 11

• What is Reiter’s syndrome?

Answer 11

A classic triad of symptoms that you can get following an STI or enteric infection. It includes:

1. Arthritis (so this is a reactive arthritis)
2. Urethritis
3. Conjunctivitis

cant see cant wee cant climb a tree!

Question 12

• What % of prosthetic joints get infected?
• What is the usual causative pathogen?
• How is it diagnosed?

Answer 12

0.5-2%

o Coagulase negative staphylococci (50%)
o Staphylococcus aureus (22%)

Joint aspirate microscopy and culture