Patient: 7-year-old boy Presentation: 5-day history of right leg pain, fever (38.8°C), and refusal to weight-bear Relevant history: Previously well child, no recent trauma, no immunocompromise. Attends school swimming. Examination findings:
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| Hb | 118 g/L | 115-135 g/L | Normal |
| WCC | 18.5 ×10⁹/L | 5-13 ×10⁹/L | ↑ Leucocytosis |
| Neutrophils | 14.2 ×10⁹/L | 1.5-8.0 ×10⁹/L | ↑ Left shift |
| Platelets | 420 ×10⁹/L | 150-400 ×10⁹/L | ↑ Reactive thrombocytosis |
| CRP | 186 mg/L | <5 mg/L | ↑↑ Significantly elevated |
| ESR | 68 mm/hr | <10 mm/hr | ↑↑ Elevated |
| Blood cultures | Pending | Negative | Awaiting result |
| Procalcitonin | 2.4 ng/mL | <0.5 ng/mL | ↑ Suggests bacterial infection |
Image 1: AP and Lateral Radiograph of Right Tibia
Radiological features:
Image 2: MRI Right Tibia (T1, T2/STIR, Post-contrast)
MRI findings:
Describe the investigation findings
What is the differential diagnosis?
What further investigations and initial management would you request?
Given the subperiosteal abscess, how would you manage this patient surgically?
Blood cultures grow MRSA. After starting vancomycin, the child develops facial flushing and an erythematous rash. What is the diagnosis and management?
At 72 hours, the child has persistent fevers and CRP has risen to 280 mg/L. What are your concerns and actions?
This pattern suggests Acute Haematogenous Osteomyelitis:
Distinguish from Septic Arthritis:
Distinguish from Ewing Sarcoma:
Q: "What organism is most likely in a 2-year-old with osteomyelitis?"
Kingella kingae is increasingly recognised in children aged 6 months to 4 years. Standard cultures may miss it - requires prolonged incubation and specific culture techniques. Consider if blood cultures negative but clinical picture fits.
Q: "What are the complications of paediatric osteomyelitis?"
| Complication | Features |
|---|---|
| Chronic osteomyelitis | Sequestrum, involucrum, sinus formation |
| Growth disturbance | If physis involved - angular deformity, limb length discrepancy |
| Pathological fracture | Through weakened bone |
| Septic arthritis | Spread to adjacent joint (especially hip) |
| Sepsis/metastatic infection | Endocarditis, septic emboli |
Q: "When would you consider this child has chronic osteomyelitis?"
Chronic osteomyelitis is defined as symptoms persisting beyond 6 weeks or recurrence after treatment. Radiographic features include:
Q: "What are the Kocher criteria and when do you use them?"
Kocher criteria are used to distinguish septic arthritis from transient synovitis of the hip in children:
Probability of septic arthritis: 0 criteria = 0.2%, 4 criteria = 99.6%