A 3-Year-Old with Fever, Refusal to Walk and a Limp
A 3-year-old boy is brought to clinic by his mother with 2 days of fever and refusal to walk. He has been irritable and off his food. There is no history of trauma, no rash, and no recent travel. He is fully immunized including Hib and pneumococcal conjugate vaccines. On examination: temperature 38.9 °C, HR 130/min, RR 28/min, BP 95/55 mmHg. He lies still with the right hip flexed, externally rotated and abducted. There is tenderness over the right hip anteriorly and pain at the extremes of passive movement in all directions. There is no swelling of the knee. He weighs 15 kg. The clinic has no ultrasound or laboratory facilities on site; the nearest hospital with pediatric orthopedics is 45 minutes away. The mother asks whether she can give paracetamol and bring him back tomorrow if he is no better.
1. What is your differential and why is the leading diagnosis a surgical emergency?
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Leading diagnosis: septic arthritis of the right hip.
The posture - hip flexed, abducted and externally rotated, with refusal to bear weight and pain at the extremes of all passive movements - is the classic 'irritable hip' position of an effusion under tension. Fever and tachycardia support infection.
Differential:
- Transient synovitis - usually afebrile or low-grade fever, able to bear weight, less toxic; commonest in 3–8 years after a viral illness.
- Septic arthritis - the diagnosis to exclude; destructive within days.
- Osteomyelitis of the proximal femur or pelvis.
- Perthes disease - usually older, insidious, no fever.
- Slipped capital femoral epiphysis - usually older, obese, chronic.
- Juvenile idiopathic arthritis, reactive arthritis, trauma, psoas abscess.
Why it is an emergency: the hip joint is a closed space; pus under pressure rapidly destroys the articular cartilage and can cause avascular necrosis of the femoral head, permanent deformity and chronic disability. Untreated, it can also progress to systemic sepsis. The window for good outcome is measured in hours to a day, not days.
Key point: in a febrile child who will not bear weight, septic arthritis must be excluded before transient synovitis is diagnosed. Kocher's criteria (fever >38.5 °C, non-weight-bearing, ESR >40, WBC >12) raise the probability, but no score replaces aspiration when suspicion is high.
2. The mother asks to go home with paracetamol and return tomorrow. How do you respond, and what is your immediate plan given the 45-minute transfer?
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Decline clearly and explain why - this is not a 'wait and see' situation.
- Explain that the hip may be infected, that infection can destroy the joint within a day, and that delay risks permanent limp and disability. Use plain language and check understanding; document the discussion.
- Do not give paracetamol and discharge. Analgesia may mask deterioration, and the child is tachycardic and febrile with a presumed deep infection.
- Immediate plan: arrange urgent transfer by ambulance to the hospital with pediatric orthopedics. Give a first dose of IV antibiotics only after blood cultures are taken if this does not delay transfer - ideally cultures and joint aspiration precede antibiotics, but do not let logistics delay transfer unduly.
- Before transfer: IV access, blood cultures, FBC, CRP, blood glucose, and analgesia. Keep him nil by mouth in case he needs anesthesia for aspiration or washout.
- At the receiving hospital: ultrasound to confirm effusion and guide aspiration; joint fluid for Gram stain, culture and cell count; urgent surgical washout if septic arthritis is confirmed; IV antibiotics for several weeks.
Judgement: the safe answer is transfer, not reassurance. If the mother refuses, escalate - involve a senior clinician and document the capacity/consent discussion; in a 3-year-old, the child's best interests govern.