Joint aspiration — branching viva

Opening question

This 3-year-old febrile child refuses to walk and holds the right hip flexed and abducted, with a raised C-reactive protein and a hip effusion on ultrasound. Score the risk of septic arthritis, and tell me what the score dictates about your next step. [1]

Branch 1 — preparing for and performing the aspiration

You have decided to aspirate. Tell me how you prepare the child, what relative contraindications you must exclude before draping, and why this hip is aspirated under ultrasound rather than on landmarks alone. [3] [4]

Branch 2 — interpreting the fluid, including a low cell count

The aspirate returns a turbid fluid with a white cell count of 40,000 per microlitre and a negative Gram stain. How do you interpret this, and does it exclude septic arthritis? Defend your reasoning, including the role of Kingella kingae. [3] [4]

Branch 3 — the haemophilic child with a swollen knee

Now picture instead a 6-year-old with severe haemophilia and a swollen knee after a fall, afebrile and well, whom a colleague wants to aspirate to exclude sepsis. What is the right first step, and under what circumstances would an aspiration be justified at all? [4]

Closing — complications and aftercare

The original child's fluid confirms septic arthritis. What are the common and the serious complications of the aspiration itself, how are they prevented, and what aftercare and disposition do you arrange? [3]