Paediatric Septic Arthritis

You are the orthopaedic CT1. The paediatric ST5 calls you from the children’s assessment unit to see a 4-year old child who has presented with acute onset right knee pain, limping and fever. How would you proceed?

Example answer introduction
With these presenting symptoms my main concern is a possible septic arthritis. I would perform an initial assessment and stabilisation of the child according to the APLS protocol. I would then take a focused history and examine the child. I would inform the orthopaedic registrar once I had implemented my initial management plan. My differential diagnoses include transient synovitis, osteomyelitis or malignancy. 

Initial Assessment and Simultaneous Resuscitation:

​On arrival, manage the patient using the A to E approach according to the Advanced Paediatric Life Support algorithm.

  • Airway

  • Breathing - O2 saturations, work of breathing - intercostal recession, use of accessory muscles - if any concerns give oxygen

  • Circulation - pulse, blood pressure, central and peripheral capillary refill time, urine output - consider catheterisation, IV access and bloods as above. 

    • Fluid bolus - Paediatrics give 20ml/kg of crystalloid solution (not dextrose)

  • Disability - AVPU, pupillary response, blood glucose

  • Exposure - look for signs of shock, evidence of meningism e.g. rash, nuchal rigidity GCS, pupils, BM, temperature

​​

During the acute phase state remember to provide constant reassessment. 

I would ensure initial investigations have been taken including; FBC, U&E, blood and urine cultures, CRP and ESR.

Once I had confirmed the patient is stable I would take a focused history.

Focused history
  • Allergies

  • Medications 

  • Past medical history including previous surgery 

  • Last meal

  • Events leading up to this point (and risk factors for the suspected septic arthritis):

    • Recent joint trauma

    • Open skin wound

    • Immunosuppression drugs/conditions

    • Recent joint surgery

Examination
A full paediatric examination needs to be taken. Specifically as specialty input one must assess the following:
  • Gait – limping

  • Pain on internal rotation and abduction of the hip

  • Muscle atrophy

  • Leg length discrepancy

Example questions to progress the station
Q1 - After your examination, you think this patient has a septic arthritis of the left hip and he is having referred pain to the knee. How would you proceed? 
Initial management
  • Analgesia according to WHO pain ladder
  • Ensure bloods including inflammatory markers CRP and ESR, blood cultures
  • X-rays – Hip and knee
  • Ultrasound hip
  • Keep nil by mouth
  • Escalate to Orthopaedic Registrar urgently – to perform aspiration of the joint
  • Empirical IV antibiotics to be started only after joint aspiration
  • Keep patient and any relatives informed
  • Document, document, document!!!
Further investigations
Kocher criteria is a screening tool to differentiate septic arthritis from transient synovitis in children with a painful hip. Children are scored from 1-4 based on symptoms. 1 point is scored for each of; non-weight bearing on affected side, temperature >38.5, ESR>40, WCC >12. Scoring ≥3 signifies a greater than 90% chance of septic arthritis. Not included in the original Kocher description but also clinically useful, is a CRP >20 is suggestive of septic arthritis. 
Escalation
Septic arthritis is an orthopaedic emergency. Missed or late diagnosis can lead to systemic sepsis, growth plate destruction and avascular necrosis of the femoral head.
 
The orthopaedic registrar should be informed immediately to review and perform joint aspiration for full blood count, glucose, Gram stain, and culture. ​​
Useful Resources

Differentiating between septic arthritis and transient synovitis of the hip in children

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