Septic arthritis + Compartment syndrome Flashcards
What is septic arthritis?
Septic arthritis describes an infection of a joint.
Which organisms cause septic arthritis?
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
Risk factors for septic arthritis
- 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
Which joints are affected in septic arthritis?
The knee is the most commonly affected joint in adults. Other joints less commonly affected include the hip, shoulder, wrist and elbow joints.
Clinical features of septic arthritis
Symptoms
- Difficulty weight bearing
- Fever
Signs
- Hot, tender, erythematous, swollen joint
- Very limited range of movement
Primary investigations for septic arthritis
- 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
What would you expect to see in the synovial fluid from a septic arthritis?
Colour: yellow and cloudy
WBC/ml: >50,000
Polymorphonuclear (PMN) cells: >50%
Culture: >50% positive
Crystals: None
Which criteria is used to diagnose septic arthritis in children?
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
Management of septic arthritis
Which antibiotics are used for:
Emperical therapy
Penicillin allergy
Suspected or confirmed MRSA
Gonococccal arthritis or gram-negative infection
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
Complications of septic arthritis
- Osteomyelitis (the spread of the infection from the joint to the surrounding bone)
- Permanent joint destruction
- Sepsis
Differential diagnoses of someone presenting with a single, painful, swollen joint:
- 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)
Define compartment syndrome
Compartment syndrome is a critical pressure increase within a confined compartmental space.
Which sites are affected by compartment syndrome?
Any fascial compartment an be affected. The most common sites are in the leg, thigh, forearm, foot, hand and buttock.
Causes of compartment syndrome
- High energy trauma
- Crush injures
- Fractures that cause vascular injury
- Iatrogenic vascular injury
- Tight casts or splints
- Deep vein thrombosis
- Post-reperfussion swelling
Pathophysiology of compartment syndrome
- 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
Clinical features of compartment syndrome
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
Investigations for compartment syndrome
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
Definitive treatment of compartment syndrome
Emergency open fasciotomy
Initial management of compartment syndrome, prior to definitive intervention, includes:
- 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
Complications of compartment syndrome
Monitor renal function closely due to potential effetes of rhabdomyolysis or reperfussion injury
