ID: Bone and Joint Infection Flashcards
What are the three common causes (and the proportions) of osteomyelitis?
- Post-trauma or surgery.
- ~50% of cases.
- Haematogenous.
- ~20% of cases.
- From Ben Clark: This is more likely to be seen in hospital practice.
- Contiguous with another infection (i.e. diabetic foot infection).
- Reminder.
Which two locations are most likely to be affected in cases of children experiencing osteomyelitis?
- What makes these areas special?
Where does the infection seed in children?
Femur and tibia.
- Rich blood supply.
In the growing metaphysis (at the end of the long bone).
Name the two processes that must happen for haematogenous infection.
- Bacteria gets under the skin, through the mucous membrane and gets into the bloodstream, and travels throughout the body.
- Seeds somewhere in the skeleton.
What is the most common location for haematogenous seeding of an infection that will lead to osteomyelitis in adults?
Verterbal column.
Describe the pathogenesis of osteomyelitis (4 points).
- Invasive bacteria cause inflammatory reaction.
- Leukocytes release enzymes that lyse the bone.
- Oedema, vascular congestion, and small-vessel thrombosis.
- Impaired flow of both medullary and periosteal blood supply.
What are the two requirements for chronic osteomyelitis to be categorised as such?
- What can’t be done in chronic osteomyelitis, but can be done in acute?
- Sequestra.
- Necrotic bone formed within a diseased or injured bone.
- Involucrum.
- Layer of new bone growth surrounding the sequestrum.
This leads to bone sclerosis (hardening) and deformity.
- Treatment with antibiotics.
- Antibiotics won’t be able to get into the wound in high enough concentrations.
Label the following diagram.
Upper left: involucrum (newly formed bone).
Lower right: sequestrum (necrotic bone).
Match the following components with the arrows on the diagram.
- Bone cortex.
- Draining sinus tract.
- Sequestrum.
- Periosteum.
- Principal site of infection.
- Soft tissue.
- Marrow cavity.
- What is the most common cause of osteomyelitis in adults, infants and pre-schoolers?
- What are some other causative bacteria specific to:
- Infants?
- Pre-schoolers?
- Adults?
- Staphylococcus aureus.
ADULTS
- ß-haemolytic Streptococcus.
- Gram negatives.
PRE-SCHOOLERS
- Kingella kingae.
- H. influenzae.
INFANTS (picked up going through the birth canal).
- S. agalactiae.
- E. coli.
What are the two most common procedures/actions that can lead to haematogenous osteomyelitis?
- Brushing teeth. (0-26%)
- Chewing candy. (17-51%)
Fill in the table (3 per column) of causative agents in different groups.
Signs/symptoms of osteomyelitis?
- Classic inflammation signs.
- Redness.
- Swelling.
- Fever.
- Pain.
- What is a Brodie abscess?
- What role does the host’s immune system play?
- Signs/symptoms (compare with classical OM)
- Typically found where?
- Subacute osteomyelitis → may persist for years before becoming frank osteomyelitis.
- Host’s immune system controls it.
- Hole in the bone filled with pus and inflammatory infiltrates → contained.
- No classical features of OM → often misdiagnosed as a tumour.
- GRUMBLING PAIN FOR WEEKS.
- Leg > arm bones.
- Eg tibia.
- What are four raised inflammatory markers in Brodie abscess?
- What are three microbiological tests to run?
- CRP.
- White cell count.
- Procalcitonin.
- IL-6.
- Blood culture.
- Joint aspiration and culture.
- Bone biopsy.
What is a test that is better than blood cultures for OM?
Sample of the pus.
Are nuclear scans useful for osteomyelitis?
No
- Empiric therapy must treat what?
- IV or oral antibiotics first?
- Add ____ in treatment for kids to cover Haemophilus and Kingella.
- Typical treatment regime (timing):
- Kids
- Adults
- S aureus.
- IV.
- Cephalosporin.
- Kids: 3-7 days IV, 3 weeks total.
- Adults: 2-4 weeks IV, >6 weeks total.
- Three DDx for septic arthritis.
- Three causes.
- Reactive arthritis.
- Body’s responds to antigens.
- Rheumatoid arthritis.
- Crystal arthropathy.
- Haematogenous. (>70%)
- Post-procedure.
- Adjacent osteomyelitis.
Describe the pathogenesis of septic arthritis.
- Inflammation of the synovium due to bacterial infection (usually bacterial).
- No basement membrane → bacteria in synovial fluid.
- Synovial hyperplasia.
- Cytokine release.
- Signs/symptoms of septic arthritis.
- Investigations.
- Treatment.
- Sx
- Purulent inflammation.
- Usually one joint, commonly knee.
- Also wrist, ankle, hip.
- Classic inflammation signs/symptoms.
- Ix
- Blood cultures.
- Joint aspirate and culture.
- Tx
- Antibiotic therapy (identical to OM)
- Inflammation and destruction of joints may continue even in those with sterile joints despite effective antimicrobial therapy.
- Persistance of bacterial antigens within the joint.
- Joint drainage/washout.
- Antibiotic therapy (identical to OM)
Septic arthritis = increased risk of osteoarthritis later in life (cel assignment taught me this lol)
IVDU are at a higher risk of septic arthritis. What is a common presentation of this?
Painful collarbone.
PROSTHETIC JOINT INFECTION
- Conservative approach?
- When is it effective?
- Non-conservative approach?
- Stages?
- Which is better?
- Conservative approach
- Early on, or in acute phase.
- DAIR = debridement, antibiotics, implant retention.
- Antibiotics = high dose IV than oral for 3-6 months
- Non-conservative approach - prosthetic joint revision.
- One-stage: Remove and replace.
- Two-stage:
- Remove prosthesis.
- Cement spacer.
- New joint later.
- Minimum 6 weeks without joint.
- Antibiotic treatment during this time I guess? (this was a question last year)
- Two-stage = higher chance of definitive cure.
- Increased risk of anaesthesia and surgery.
Three classes of OM by Waldvogel classification system?
- Haematogenous.
- Secondary to contiguous infection.
- Chronic OM.
Four stages of Cierny-Mader classification.
- Medullary osteomyelitis.
- Superficial OM.
- Localised OM.
- Diffuse OM.
