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Musculoskeletal > Infection > Flashcards

Infection Flashcards

1
Q

Name 4 local factors that increase susceptibility to infection of bones and joints

A 
Trauma
Articular steroid injection
Large wound area and depth
Poor perfusion
Distal anatomical location
Necrotic tissue
Foreign body
Chronic bone or joint disease
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2
Q

Name 4 systemic factors that increase susceptibility to infection of bones and joints

A 
Age: children and elderly
Malnutrition
General illness
Anaemia
Diabetes mellitus
Sickle-cell anaemia*
Alcohol excess
Rheumatoid disease
Immunosuppression
IVDU
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3
Q

Describe the features of acute pyogenic infection

A

Formation of pus often localised in an abscess
Abscess may extend infection along tissue directly, or spread via lymphatics (lymphangitis and lymphadenopathy) or blood (bacteraemia and septicaemia).

Systemic reaction due to enzymes and toxins.

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4
Q

Describe the features of chronic infection

A

May occur after acute infection
Less acute systemic effects, but may be more debilitating
Lymphadenopathy, splenomegaly, and tissue wasting

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5
Q

Outline the treatment principles of bone and joint infections

A 
Analgesia and supportive measures
Rest the affected part
Initiate antibiotics
Drainage of pus and debridement of necrotic tissue
Stabilise bone if fractured
Maintain soft tissue and skin cover
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6
Q

What is typically the causative organism of acute osteomyelitis?

A

Staph aureus
Less often: Strep pyogenes, Strep pneumoniae, or H. influenzae (children)

If sickle-cell: Salmonella typhi

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7
Q

Which patient group is most affected by acute osteomyelitis?

A

Children over age of 4 years

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8
Q

What is the most common location of acute osteomyelitis in children?

A

Metaphysis of long bones
Most often at the proximal or distal end of the femur, or the proximal end of the tibia

N.B. in infants, acute osteomyelitis can also reach the epiphysis due to presence of anastomoses.

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9
Q

Describe the pathological changes of acute osteomyelitis

A
  1. Acute inflammation: intense pain, obstructed blood flow
  2. Suppuration: subperiosteal abscess formation
    - may spread along shaft and re-enter bone, or spread to soft tissues
    - infants: may spread to epiphysis and joint
  3. Necrosis: usually seen by 1 week
    - stasis, periosteal stripping, thrombosis
    - bone fragments can act as foreign bodies
  4. New bone formation: involucrum encases infection
    - if infection persists ➔ chronic osteomyelitis
  5. Resolution
    - requires infection to be controlled and intraosseous pressure to be release at an early stage
    - may result in overall thickening of bone
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10
Q

Describe the clinical features of acute osteomyelitis in children

A

Severe pain: limb held still
Systemic: fever, malaise, irritability, lethargy
Tenderness over involved bone
Decreased range of motion in adjacent joints

Later: red, swollen, warm ➔ pus formation (suppuration)

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11
Q

Describe the clinical features of acute osteomyelitis in infants and neonates

A

Infants and neonates may present with misleadingly mild symptoms: failure to thrive, drowsy, irritable
May have metaphyseal tenderness and resistance to joint movements
Always look at other sites, as multi infection is not uncommon.

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12
Q

Name 2 aspects of the history that would increase suspicion of acute osteomyelitis in neonates

A

Birth difficulties

Umbilical artery catheterisation

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13
Q

Name and explain 2 consequences of acute osteomyelitis in infants within 1st year of life

A

Growth retardation and deformity

Metaphysis-epiphysis anastomoses present in 1st year of life, allow haematogenous spread to epiphysis.

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14
Q

Where is the commonest location of acute osteomyelitis in adults? What clinical features would suggest this?

A

Spine

Suspicious features: back pain and a mild fever

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15
Q

How is acute osteomyelitis confirmed?

A

Fine needle aspiration and culture

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16
Q

How is acute osteomyelitis investigated?

A 
Aspirate pus from subperiosteal abscess or joint*
Culture for cells and organisms
Raised WBC and ESR
MRI*: 90-100% sensitivity
X-ray: normal for first 2 weeks
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17
Q

Explain the treatment of acute osteomyelitis

A

Blood and aspirate samples sent for culture
Supportive: bed rest, splint, analgesia

Prompt antibiotics if pus found on aspiration
Empirical antibiotics: Flucloxacillin or clindamycin
Continue antibiotics for 4-6 weeks
Children should initially receive 2 weeks of IV antibiotics

Abscess drainage
Surgical debringement

Outpatient follow-up*: crucial to check for recurrence

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18
Q

State 3 complications of acute osteomyelitis

A

Spread: septic arthritic or metastatic osteomyelitis
Pathological fractures
Growth disturbance/deformity if epiphysis involved
Persistent infection ➔ chronic osteomyelitis

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19
Q

Describe the clinical features of subacute osteomyelitis

A

Common in distal femur, and proximal and distal tibia

Pain near one of larger joints for several weeks

20
Q

What classic radiographic sign is indicative of subacute osteomyelitis?

A

Brodie abscess: small oval cavity surrounded by sclerotic bone

Most be explored as can be mistaken for osteoid osteoma or bone tumour if large

21
Q

What is the commonest causative organism of post-traumatic osteomyelitis?

A

Staph aureus

Others: E. coli, Proteus mirabilis, Pseudomonas aeruginosa

22
Q

Describe the clinical features of post-traumatic osteomyelitis

A

Fever
Pain and swelling over fracture site
May have purulent discharge

23
Q

What are the common causes of chronic osteomyelitis?

A

Following open fracture or operation

Less common nowadays after acute osteomyelitis

24
Q

Name 2 typically causative organisms of chronic osteomyelitis

A 
Staph aureus
E. coli
Strep pyogenes
Proteus mirabilis: soil
Pseudomonas aeruginosa
Strep epidermidis: surgical implants
25
Q

Describe the clinical features of chronic osteomyelitis

A

Recurrent pain, redness, and tenderness at affected site

Healed and discharging sinus

26
Q

What x-ray features are seen with chronic osteomyelitis?

A

Bone rarefaction (thinning) surrounded by dense sclerosis and cortical thickening

27
Q

Outline the treatment options for chronic osteomyelitis

A

If seldom relapses: conservative management
-Rest, dressing, and antibiotics for 4-6 weeks

Drainage of any acute abscess

Refractory or frequent relapses: surgery

  • excision of infected/devitalised bone
  • Ilizarov method after bone transport ➔ bone union
28
Q

What is the usual causative organism of septic arthritis?

A

Staph aureus

Children aged 1-4: H. influenzae if not vaccinated

29
Q

Explain the pathology of septic arthritis

A

Joint invaded by:

  • a penetrating wound
  • eruption of adjacent bone abscess
  • distal haematogenous spread
30
Q

Describe the clinical features of septic arthritis in children

A

Acute severe pain and swelling of single joint
-Commonly hip (children)
-Unable to weight bear
Tachycardia
Swinging fever
Red, swollen, tender joint: often flexed
Restricted movement due to pain and spasm

31
Q

Describe the clinical features of septic arthritis in infants

A

Emphasis on septicaemia rather than joint pain
Irritable and refuses to feed
Rapid pulse +/- fever
Local warm, tender joints: resistant to movement
Examine umbilical cord and IV access sites

32
Q

Describe the clinical features of septic arthritis in adults

A 
Acute severe pain and swelling of single joint
-Commonly knee (adults)
-Unable to weight bear
Tachycardia
Mild fever
Red, swollen, tender joint: often flexed
Restricted movement due to pain and spasm
Unable to weight bear
33
Q

How does the presentation of septic arthritis differ in adults with rheumatoid arthritis?

A

Patients with rheumatoid arthritis, especially on corticosteroids, may develop a ‘silent’ joint infection.

Suspect septic arthritis if unexplained deterioration in patient’s general condition.

34
Q

What x-ray changes are seen with septic arthritis?

A

First 2 weeks of bacterial arthritis:
Soft-tissue swelling
Widening of joint space
Periarticular osteoporosis

Later: joint space narrowing and signs of bone destruction

35
Q

How is a diagnosis of septic arthritis confirmed?

A

Joint aspiration and culture*
Blood culture positive in 50%
WBC, CRP, and ESR are suggestive

36
Q

Name 3 differentials of septic arthritis

A

Osteomyelitis near joint: may be indistinguishable, safest to assume both osteomyelitis and septic arthritis present

Acute haemarthrosis (trauma or haemophilia): blood on joint aspiration

Transient synovitis: clinical features less acute

Gout/CPPD: presence of urate or pyrophosphate crystals

37
Q

Name 2 complications of septic arthritis

A 
Dislocation
Avascular necrosis
Epiphyseal destruction ➔ pseudoarthrosis
Growth disturbance/deformity
Ankylosis: stiffening and immobility due to fusion
38
Q

What is the treatment for septic arthritis

A 
Joint aspiration and examination
Antibiotics STAT: flucloxacillin 4-6 weeks
Joint rested and splinted
-if hip: abducted and 30 degrees flexed
Drainage and wash-out of joint

Encourage movement afterwards if cartilage intact
Otherwise, immobilise joint in optimum position whilst ankylosis occurs

39
Q

What percentage of TB patients present with skeletal involvement?

A

5%

40
Q

Which patient groups are most commonly affected by skeletal TB?

A

Endemic: pulmonary TB in children and young adults

Non-endemic: chronic disease, or immunosuppressed

41
Q

Explain the pathology of skeletal TB

A

Infection reaches the skeleton by haematogenous seeding from lungs or intestine.
Chronic inflammation ➔ caseating granuloma
Cold abscess
Chronic sinus, may have secondary pyogenic infection

42
Q

Describe the progression of vertebral TB

A

Vertebral TB usually begins in the anterior part of the vertebral body near the intervertebral disc.

Later invasion into intervertebral disc, with subsequent collapse forwards ➔ sharp angulation of spine (gibbus deformity)

43
Q

Describe the progression of joint TB

A

Joint TB may start in synovium or nearby metaphysis. If untreated, it will destroy the articular cartilage and cause fibrous ankylosis.

44
Q

Describe the clinical features of skeletal TB

A

Tuberculosis arthritis (1%): affects spine (50%), hip or knee (30%). Fever, night sweats, weight loss.

Pott’s disease (TB spondylitis): Back pain, lower limb weakness, kyphosis. Fever, night sweats, weight loss.

45
Q

How is skeletal TB treated?

A

Anti-tubercular drugs:
2 months: Rifampicin, Isoniazid (+pyridoxine), Pyrazinamide, Ethambutol
Additional 4 months: Rifampicin, Isoniazid (+pyridoxine)

Dose is weight-dependent

46
Q

What monitoring is required whilst on anti-tubercular treatment?

A

LFTs: ‘R.I.P.’ all can cause hepatitis

Visual acuity: ‘E.’ can cause optic neuritis

Musculoskeletal (17 decks)

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