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MSK + Rheumatology > Infective Arthritis - Septic arthritis + Osteomyelitis > Flashcards

Infective Arthritis - Septic arthritis + Osteomyelitis Flashcards

1
Q

What is septic arthritis?

A

Infection of the joint

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2
Q

Give 3 causes of septic arthritis.

A
  1. Staphylococcus aureus.
  2. Streptococci.
  3. Neisseria gonorrhoea.
  4. Gram-NEGATIVE bacteria e.g. E.coli or Pseudomonas Aeruginosa in the elderly or very young or those who are systemically unwell/ IV drug user

Consider the clinical context of the patient!

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3
Q

What is the most common cause of septic arthritis?

A

Staphylococcus aureus from pneumonia or a skin infection

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4
Q

Pseudomonas septic arthritis is usually seen in who?

A
  1. Elderly
  2. Immunocompromised
  3. IVDU
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5
Q

What bacteria is often associated with prosthetics in septic arthritis?

A

Staph epidermis

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6
Q

If a young patient came in with a single acutely swollen joint, what should you always think of first?

A

TOM TIP:
In a young patient presenting with a single acutely swollen joint always think of gonococcus septic arthritis until proven otherwise.

Gonorrhoea infection is common and delaying treatment puts the joint in danger.

In your exams, it might say the gram stain revealed a “gram-negative diplococcus”.
The patient may have urinary or genital symptoms to trick you into thinking of reactive arthritis, but remember that it is important to exclude gonococcal septic arthritis first as this is the more serious condition.

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7
Q

Give 5 risk factors for septic arthritis.

A
  1. Pre-existing joint disease - especially RA (chronically inflamed joints are at more risk of infection than normal joints)
  2. Diabetes melllitus
  3. Immunosuppression e.g. HIV
  4. Chronic renal failure
  5. Recent joint surgery
  6. Prosthetic joints - prosthetic joint infection (see below)
  7. IV drug abuse (IVDU)
  8. Age > 80 YO and infants
  9. Recent intra-articular steroid injection
  10. Direct/penetrating trauma
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8
Q

Give 4 symptoms of septic arthritis.

A
  1. Painful.
  2. Red.
  3. Swollen.
  4. Hot.
  5. Fever.
  6. Limited range of movement - immobile joint (can affect >1 joint)
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9
Q

What joints are most commonly affected by septic arthritis?

A
  1. Knee
  2. Hip
  3. Shoulder
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10
Q

Investigations for septic arthritis.

A
  1. URGENT JOINT ASPIRATION (arthrocentesis):
    - For M,C&S test (microscopy, culture & sensitivity)
    * Send fluid for urgent Gram-staining and blood culture
  • Fluid will be purulent/opaque/thick/pussy due to high WCC in it
  • Note: NORMAL FLUID is clear yellow and quite thin I.E. not very viscous
  • ALWAYS ASPIRATE BEFORE ANTIBIOTICS GIVEN!!
  1. Polarised light microscopy for crystals
    - To exclude gout / pseudogout
  2. Bloods:
    - ESR, CRP and WCC raised
    - Note: CRP may not always be raised
  3. X-ray:
    * No value in septic arthritis
    * Loosening or bone loss around a previously well fixed implant will suggest infection
  4. Skin wound swabs, sputum and throat swab or urine if gonoccal infection possibility
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11
Q

Describe the treatment for septic arthritis.

A
  1. Aspirate joint
  2. Empirical Antibiotics - general ones depending on gram stain
    - e.g. IV flucloxacillin + rifampicin for most gram-negatives (E.coli)
    = often 1st line
    - e.g. Vancomycin + rifampicin for penicillin allergy, MRSA or prosthetic joint
  3. Pathogen-directed Antibiotics - guided by aspirate cultures
    * IV antibiotics given for 2 weeks
    * Monitor progress by looking at ESR + CRP
  4. Analgesia - NSAIDs e.g. Ibuprofen
  5. Rest/physiotherapy
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12
Q

Before your cultures come back, what antibiotic would you prescribe to treat septic arthritis?

If it came back as MRSA +ve, what would you give?

A

Flucloxacillin.

Vancomycin for MRSA.

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13
Q

3 typical antibiotics for septic arthritis?

A

Flucloxacillin
Clindamycin
Ciprofloxacin
Vancomycin

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14
Q

Give 4 differential diagnoses for septic arthritis.

A
  1. Gout
    - Fluid shows urate crystals that are negatively birefringent of polarised light
  2. Pseudogout
    - Fluid shows calcium pyrophosphate crystals that are rod-shaped intracellular crystals positively birefringent of polarised light
  3. Reactive arthritis
    - Typically triggered by urethritis or gastroenteritis and associated with conjunctivitis
  4. Haemarthrosis
    - Bleeding into the joint
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15
Q

EXAM QUESTION:
Which of the following is now a rare cause for joint infection in INFANTS, due to the standard childhood immunisation schedule in the UK?

  1. Staphylococcus Aureus
  2. Group A (Beta-haemolytic)
  3. Varicella Zoster
  4. Rubella
  5. Haemophilus Influenzae
A

Answer:
5. Haemophilus Influenzae

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16
Q

How does gonococcal arthritis present?

A

Fever, arthritis, tendonitis
Multiple joints
Maculopapular pustular rash on palms + soles

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17
Q

How would an infected prosthetic joint present?

A

Chronic low grade
Pain ever since it was done
Staph aureus/enterococci
Low ESR = CRP
Normal WCC
Diagnosis - joint aspirate
Treatment - Arthropathy (remove and replace)

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18
Q

Define osteomyelitis.

A

Refers to inflammation in a bone and bone marrow, usually caused by bacterial infection (secondary to infection).

  • Osteon-myelo-itis = bone-marrow-inflammation
  • Infection localised to bone
19
Q

Describe the epidemiology of osteomyelitis.

A
  • Increasing incidence of chronic OM.
  • Bimodal age distribution.
20
Q

What can cause osteomyelitis.

A
  1. S.aureus!
  2. Coagulase negative staphylococci e.g. s.epidermidis.
  3. Aerobic gram negative bacilli.
  4. Mycobacterium TB.
21
Q

What bacteria is particularly associated with osteomyelitis in sickle cell?

A

Salmonella

22
Q

Give 3 risk factors for osteomyelitis.

A

Inflammatory arthritis
Sickle cell
IVDU
Immunocompromised
Diabetes
Prosthesis
Trauma

23
Q

Name 2 predisposing conditions for osteomyelitis.

A
  1. Diabetes.
  2. PVD.
24
Q

Pathophysiology of osteomyelitis: describe the 3 ways in which the pathogen can get into bone.

A
  1. Easy: inoculation of infection into the bone e.g. trauma/open wound.
  2. Quite easy: contiguous spread of infection to bone from adjacent tissues.
  3. Difficult: hematogenous seeding e.g. due to cannula infection.
25
Q

What bones are likely to be affected by hematogenous seeding in adults?

A

Vertebrae.

26
Q

What bones are likely to be affected by hematogenous seeding in children?

A

Long bones.

27
Q

Why do vertebrae tend to be affected by hematogenous seeding in adults?

A

With age, the vertebrae become more vascular meaning bacterial seeding is more likely.

28
Q

Why do long bones tend to be affected by hematogenous seeding in children?

A

In children the metaphysis of long bones has a high blood flow and BM are absent meaning bacteria can move from the blood to bone.

29
Q

Name a group of people who are at risk of hematogenous osteomyelitis.

A

IVDU and other groups at risk from bacteraemia.

30
Q

Give 4 host factors that affect the pathogenesis of osteomyelitis.

A
  1. Behavioural e.g. risk of trauma.
  2. Vascular supply e.g. arterial disease.
  3. Pre-existing bone/joint problems e.g. RA.
  4. Immune deficiency.
31
Q

Acute osteomyelitis: what changes to bone might you see histologically?

A
  1. Inflammatory cells.
  2. Oedema.
  3. Vascular congestion.
32
Q

Chronic osteomyelitis: what changes to bone might you see histologically?

A
  1. Necrotic bone - ‘sequestra’.
  2. New bone formation.
  3. Neutrophil exudates.
33
Q

Why does chronic osteomyelitis lead to sequestra and new bone formation?

A

Inflammatory exudate ruptures periosteum -> blood supply impaired -> necrosis -> sequestra -> new bone forms.

34
Q

Give 5 signs of osteomyelitis.

A
  1. Fever.
  2. Rigors.
  3. Sweats.
  4. Malaise.
  5. Tenderness.
  6. Warmth.
  7. Swelling.
  8. Erythema.
35
Q

Give a sign specific to chronic osteomyelitis.

A

Sinus formation.

36
Q

What investigations might you do on someone who you suspect may have osteomyelitis?

A
  1. Bloods: raised inflammatory markers and WCC.
  2. Plain radiographs and MRI.
  3. Bone biopsy.
  4. Blood cultures.
37
Q

What is the differential diagnosis for osteomyelitis?

A
  1. Key one - CHARCOT JOINT - damage due to sensory nerves affected by diabetes
  2. Cellulitis.
  3. Avascular necrosis.
  4. Gout.
38
Q

How would you investigate osteomyelitis?

A
  • Imaging:
    1. Plain X-ray may show osteopenia
    2. MRI may show marrow oedema from 3-5 days (sign of osteomyelitis) - done after X-ray
    3. Bone scans are also helpful
  1. Blood:
    * Blood culture to determine aetiology
    * ESR & CRP raised
    * Acute - raised WCC
    * Chronic osteomyelitis - can have normal WCC
  2. Bone biopsy & culture to determine aetiology
39
Q

What X-ray changes would you see in osteomyelitis?

A
  1. Cortical erosion
  2. Periosteal reaction
  3. Lucency
  4. Sclerosis
  5. Sequestrae, involcrums
40
Q

What is the gold standard investigation for osteomyelitis?

A

Open bone biopsy - for culture and histology

41
Q

Describe the usual treatment for osteomyelitis.

A
  1. Immobilisation
  2. Antimicrobial therapy:
    - Tailored to culture + sensitivity findings
  • IV TEICOPLANIN - side effects; rash, pruritus, GI upset
  • IV FLUCLOXACILLIN
  • ORAL FUSIDIC ACID

= Stop treatment guided by ESR/CRP monitoring

  1. Surgical debridement and removal of dead bone (sequestrum)
42
Q

Give the side effects of Teicoplanin.

A

Side effects:
1. Rash
2. Pruritus
3. GI upset

43
Q

Give one reason why osteomyelitis is difficult to treat.

A

The antibiotics struggle to penetrate bone and bone has a poor blood supply.

44
Q

Give 4 ways in which TB osteomyelitis is different to other osteomyelitis.

A
  1. Slower onset.
  2. Epidemiology is different.
  3. Biopsy is essential - caseating granuloma.
  4. Longer treatment.

MSK + Rheumatology (22 decks)

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