Septic Arthritis Flashcards

1
Q

Define septic arthritis and what is the most common joint affected

A

Infection of 1 or more joints caused by pathogenic inoculation of microbes

most common site of infection is the hip (75%)

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2
Q

What are the causes of septic arthritis

A

Infection can occur either by direct inoculation (punctured wound, infected skin lesion) or via haematogenous spread
Staphylococci or Streptococci (91%)
Sexually active: gonococcal
Older/immunocompromised: gram-negative
Penetrating trauma: anaerobic organisms
Immunocompromised/endemic areas: TB

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3
Q

What are the risk factors for septic arthritis

A

Underlying joint disease e.g. osteoarthritis, rheumatoid arthritis
Osteomyelitis (15% co-existent)
Prosthetic joint
Immunosuppression e.g. HIV, immunosuppressants
IVDU
Contiguous spread e.g. from cutaneous ulcers or skin infection
Exposure to ticks - travel to or residence in areas where Lyme disease is prevalent
Previous intra-articular corticosteroid injection, recent joint surgery, low SES

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4
Q

What is the epidemiology for septic arthritis

A

Most common <4 years old
Estimated prevalence in developed countries is 6 cases per 100,000 population per year, which increases 10-fold in those with underlying joint disease or with prosthetic joints
Often diagnosed late due to normal X-ray at presentation

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5
Q

What are the symptoms of septic arthritis

A

Joint pain and swelling + redness
- Hot, swollen, painful, restricted joint (monoarticular)
- Excruciating pain
- <2 weeks
- Most with septic arthritis of a weight-bearing joint will not be able to walk, and the joint is often held in a position that maximises joint space
Large joints: knee, hip, shoulder, ankle, elbow, wrist
Fever, chills, rigors

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6
Q

What are the differentials for septic arthritis

A

Transient synovitis
Rheumatoid arthritis
Haemarthrosis in haemophilia
Trauma
Osteomyelitis
Bursitis
Cellulitis
TB
Lyme disease

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7
Q

What are the signs of septic arthritis on examination

A

Ob: Pyrexia
Joint
- Painful, hot, swollen and immobile joint with overlying erythema
- Severe pain that prevents passive movement
- Reduced range of movement
- Pseudoparesis/pseudoparalysis - infants holding their joint still
- Joint held flexed, hip abducted, externally rotated
- Joint effusion
- Signs of aetiology e.g. small pustules near the joint for N. gonorrhoea

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8
Q

What are the investigations for septic arthritis

A

Regard a hot, swollen, acutely painful joint with restriction of movement as septic arthritis until proven otherwise.

Bloods: FBC, Blood culture, CRP/ESR, viral serology, LFTs
Other:
- Joint aspiration for cytology, culture, sensitivities: grossly purulent, polarising microscopy negative
- Plain joint radiograph: initially normal, may show widening oof joint space
USS: for guidance of aspiration

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9
Q

What is the management for septic arthritis

A

Hot, swollen, painful joint + fever → refer to emergency care
1. Admit
2. Aspirate for MC&S
3. Empirical antibiotics: consult microbiologist
4. Joint aspiration
5. Analgesia: paracetamol or NSAIDs
6. Monitor FBC, ESR, CRP, procalcitonin

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10
Q

What are the complications of septic arthritis

A

Osteomyelitis (infection spreads to surrounding bone)
Joint destruction

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11
Q

What is the prognosis for septic arthritis

A

Delayed or inadequate treatment may lead to irreversible joint destruction and subsequent disability
There is a single-joint estimated case fatality rate of 11%

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