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YEAR 1 MED > Infection of bones and joints > Flashcards

Infection of bones and joints Flashcards

1
Q

Osteomyelitis vs septic arthritis?

A
  • Osteomyelitis = infection in bone
  • Septic arthritis = infection in a joint
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2
Q

What are the 2 ways in which a bone can become infected?

A
  • Direct inoculation (exogenous)
  • Blood-borne bacteria (haematogenous)
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3
Q

Which type of way for a bone to become infected is more common in children and which is more common in adults?

A
  • Children: haematogenous spread of bacteria more common
  • Adults: exogenous more likely (most commonly due to infection post-surgery or after a penetrating injury)
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4
Q

What is the overall most common infecting organism of a bone or joint?

A
  • Staphylococcus aureus
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5
Q

What is the management for post-trauma osteomyelitis?

A
  • Urgent surgical debridement and washout (with saline solution) to remove contaminated material and dead bone
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6
Q

What is post-surgery osteomyelitis?

A
  • Procedures involving implants (joint prostheses, plates, screws) come with risk of infection
  • Due to the lack of blood supply to these implants, eradication is difficult without surgery
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7
Q

What can be done to reduce the risk of post-surgery osteomyelitis?

A
  • aseptic technique
  • antibiotic prophylaxis
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8
Q

Describe the pathogenesis of acute haematogenous osteomyelitis.

A

1.Bacteraemia that settles in the metaphysis of a long bone
2.Inflammation and pus formation within the bone
3.Pus escapes through the haversian canals to form a subperiosteal abscess
4.Pus is now present on both sides of the bone, causing this part of the bone to die
5.Dead bone, called sequestrum, harbours infection
6.New periosteum forms around the sequestrum as the body tries to fight the infection

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9
Q

Where is blood supply to the bone from?

A
  • the endosteum and periosteum
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10
Q

Sequence of events in osteomyelitis…

A
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11
Q

What is sequestrum?

A
  • a piece of dead bone tissue formed within a diseased or injured bone, typically in chronic osteomyelitis
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12
Q

What are the clinical features of acute osteomyelitis?

A
  • pain, fever, loss of function, more common in tibia and femur
  • tender to palpate, erythematous, swollen
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13
Q

What investigations should be done for suspected osteomyelitis?

A
  • Clinical history useful
  • Bloods: WCC/ESR/CRP raised
  • X-ray: initially normal, but after 10 days features of lysis and sequestrum may be seen as a sclerotic area (Brodie abscess may be seen)
  • Isotope bone scan: shows increased uptake
  • MRI
  • (Blood cultures should be taken before antibiotics given as antibiotics affect results)
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14
Q

Brodie abscess…

A
  • Late x-rays of osteomyelitis may show a Brodie abscess in the metaphysis of long bones
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15
Q

What is the conservative management for osteomyelitis?

A
  • analgesia, splintage, antibiotics
  • (flucloxacillin is usually first-line for Staph.A)
  • antibiotics given IV for 6 weeks, course of oral antibiotics after if needed
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16
Q

What is MRSA?

A
  • Meticillin-Resistant Staphylococcus aureus
  • (vancomycin or teicoplanin usually given)
17
Q

What are the 2 main complications in osteomyelitis (one is children only, growth plate…)?

A
  • if the physis is damaged, leading to growth disturbance and deformity
  • if the infection spreads to the joint, causing septic arthritis
18
Q

In young sexually active adults, what is the most common infecting organism causing infection within the bone/joint?

A
  • Neisseria gonorrhoea (gonococcus)
19
Q

What is the pathology of haematogenous septic arthritis?

A
  • the bacterium settles in the synovium, which may be inflamed due to trauma or disease
  • proliferation of bacteria causes an inflammatory response by the host with numerous leukocytes migrating into the joint
  • the variety of enzymes and breakdown products produced damages the delicate articular cartilage very quickly (within hours) and, if left unchecked, permanent damage will occur
20
Q

Normal knee VS septic knee (early) VS septic knee (later)…

A
21
Q

What are the clinical features of septic arthritis?

A
  • acutely hot swollen joint, fever, systemically unwell, non weight-bearing (usually knee/hip)
22
Q

What investigations should be done for suspected septic arhritis?

A
  • Joint aspiration: fluid sent for urgent gram stain, culture, and examination for crystals
  • Bloods: WCC/CRP/ESR elevated
  • (X-ray: normal until very late stages where joint destruction seen)
23
Q

What is the management for septic arthritis?

A
  • IV antibiotics (according to local guidelines)
  • joint washout in theatre
  • physio after for rehab
24
Q

What are the main complications of septic arthritis?

A
  • Seeding of infection can occur to the spine or other organs
  • Joint destruction with long-term arthritis or even ankylosis (bony fusion across the joint)
  • Avascular necrosis (particularly in the hip)
25
Q

What is TB (tuberculosis) due to and how does MSK TB result?

A
  • TB is due to Mycobacterium tuberculosis infection
  • MSK TB results when primary TB (lung) becomes widespread or when later reactivation or reinfection occurs (immunocompromised patients)
  • most common extra-pulmonary TB is Pott’s disease (TB of the spine)
26
Q

What are the clinical features of Tuberculosis?

A
  • TB presents with gradual symptoms of pain and may be initially diagnosed as OA or inflammatory arthritis
  • systemically unwell (malaise, weight loss)
27
Q

What are the 2 most common tests for TB exposure?

A
  • Mantoux and Heaf tests: skin hypersensitivity tests
  • (for confirmation, large samples of bone or synovial fluid are required, which need to be cultured (Löwenstein-Jensen medium) for a prolonged period (6 weeks))
28
Q

What test should be done if mycobacterial infection is suspected?

A
  • If mycobacterial infection is suspected, samples should be submitted to a Ziehl-Neelsen stain to look for acid/alcohol-fast bacilli
29
Q

What would x-ray images show in a patient with TB?

A
  • variable amounts of joint destruction with periarticular osteopenia
30
Q

What is the management for TB?

A
  • Commonly used drugs: rifampicin, isoniazid, and ethambutol
  • (spinal abscess may need drainage with stabilisation of spine)
31
Q

What are some risk factors for osteomyelitis?

A
  • diabetes
  • peripheral vascular disease
  • immunosuppression

YEAR 1 MED (49 decks)

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