Septic arthritis + Compartment syndrome Flashcards

1
Q

What is septic arthritis?

A

Septic arthritis describes an infection of a joint.

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2
Q

Which organisms cause septic arthritis?

A

Up to 90% of cases are caused by staphylococci or streptococci

  • Staphylococcus aureus - most common cause in all age group
  • Staphylococcus epidermidis - prosthetic joints
  • Streptococcus pyogenes -children under 5 years old
  • Neisseria gonorrhoeae - young, sexually active adults
  • Pseudomonas aeruginosa - immunosupressed, elderly and IV drug abuse
  • Escherichia coli - immunosupressed, elderly, and IV drug abuse
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3
Q

Risk factors for septic arthritis

A
  • Underlying joint disease: 10 fold increased risk; conditions such as rheumatoid arthritis, osteoarthritis and gout
  • Intravenous drug use: transfer of pathogenic organisms into the blood stream
  • Immunocompromised: elderly, diabetes, HIV
  • Prosthetic joint
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4
Q

Which joints are affected in septic arthritis?

A

The knee is the most commonly affected joint in adults. Other joints less commonly affected include the hip, shoulder, wrist and elbow joints.

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5
Q

Clinical features of septic arthritis

A

Symptoms

  • Difficulty weight bearing
  • Fever

Signs

  • Hot, tender, erythematous, swollen joint
  • Very limited range of movement
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6
Q

Primary investigations for septic arthritis

A
  • Joint aspiration (arthrocentesis): definitive investigation ideally prior to commencing antibiotics; synovial fluid should be sent to the lab for microscopy and culture
  • Blood cultures: should be performed on all patients before commencing antibiotics
  • FBC: leukocytosis
  • CRP and ESR: elevated due to inflammation and used for monitoring response to treatment
  • Plain X-ray: not diagnostic but recommended as a baseline investigation to assess underlying joint disease. Early septic arthritis may show eveidence of a joint effusion
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7
Q

What would you expect to see in the synovial fluid from a septic arthritis?

A

Colour: yellow and cloudy

WBC/ml: >50,000

Polymorphonuclear (PMN) cells: >50%

Culture: >50% positive

Crystals: None

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8
Q

Which criteria is used to diagnose septic arthritis in children?

A

Kocher criteria

A score of 2 suggests a 40% probability and a score of 3 suggests a 93% probability.

  • Non-weight bearing
  • Temp >38.5
  • ESR >40mm/hr
  • WCC >12 x 109/L
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9
Q

Management of septic arthritis

Which antibiotics are used for:

Emperical therapy

Penicillin allergy

Suspected or confirmed MRSA

Gonococccal arthritis or gram-negative infection

A

Antibiotics as well as joint aspiration to dryness as often as required.

2 weeks of intravenous antibiotics followed by 4 weeks of oral.

Emperical therapy: flucloxacillin is first line

Penicilin allergy: clindamycin

Suspected or confirmed MRSA: vancomycin

Gonococcal arthritis or gram negative infection: cefotaxime or ceftriaxome

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10
Q

Complications of septic arthritis

A
  • Osteomyelitis (the spread of the infection from the joint to the surrounding bone)
  • Permanent joint destruction
  • Sepsis
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11
Q

Differential diagnoses of someone presenting with a single, painful, swollen joint:

A
  • Septic arthritis
  • Flare of osteoarthritis
  • Haemarthrosis
  • Crystal arthropathies (gout and pseudogout)
  • Rheumatoid arthritis (and other inflammatory arthropathies)
  • Reactive arthritis
  • Lyme disease (infection with Borrelia burgdoferi)
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12
Q

Define compartment syndrome

A

Compartment syndrome is a critical pressure increase within a confined compartmental space.

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13
Q

Which sites are affected by compartment syndrome?

A

Any fascial compartment an be affected. The most common sites are in the leg, thigh, forearm, foot, hand and buttock.

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14
Q

Causes of compartment syndrome

A
  • High energy trauma
  • Crush injures
  • Fractures that cause vascular injury
  • Iatrogenic vascular injury
  • Tight casts or splints
  • Deep vein thrombosis
  • Post-reperfussion swelling
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15
Q

Pathophysiology of compartment syndrome

A
  • Fascial compartments are closed and cannot be distended; any fluid deposited within them will cause an increase in the intra-compartmental pressure

As pressure increases:

  • Veins will be compressed, increasing hydrostatic pressure within them, causing fluid to move down its gradient out of the veins, increasing intra-compartmental pressure further
  • Traversing nerves are compressed; creating a sensory +/- motor deficit in the distal distribution
  • Intracompartmental pressure reaches the diastolic blood pressure, arterial inflow will be compromised, leading to ischaemia
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16
Q

Clinical features of compartment syndrome

A

Symptoms tend to present within hours, although it can develop up to 48 hours post insult.

  • Severe pain, disproportionate to the injury, which is not readily improved with initial measures
  • Pain is made worse by passively stretching the muscles within the affected compartment
  • Parasthesia distally is a common feature
  • The affected compartment may feel tense compared to the contralateral side , but generally will not be swollen
  • If the disease progressed and the compartment syndrome is missed, the features of acute arterial insufficiency will subsequently develop:
    • Pain (disproportionate to the injury)
    • Pallor (or mottled which becomes non-blanching)
    • Perishingly cold
    • Paralysis
    • Pulselessness
17
Q

Investigations for compartment syndrome

A

Diagnosis is essentially clinical

Where there is clinical uncertainty: an intra-compartmental pressure monitor may be used

A creatinine kinase (CK) level may aid diagnosis , if elevated or trending upwards

18
Q

Definitive treatment of compartment syndrome

A

Emergency open fasciotomy

19
Q

Initial management of compartment syndrome, prior to definitive intervention, includes:

A
  • Keep the limb at a neutral level with the patient (do not elevate or lower)
  • Improve oxygen delivery with high flow oxygen
  • Augment blood pressure with bolus of intravenous crystalloid fluids
  • Remove all dressings/splints/casts down to the skin
  • Treat symptomatically with opioid analgesia
20
Q

Complications of compartment syndrome

A

Monitor renal function closely due to potential effetes of rhabdomyolysis or reperfussion injury