Review Question - QID 4620

Based on the clinical findings and figures shown, the patient has developed a septic arthritis of the left hip. As the patient has 3 out of the 4 Kocher criteria, he has a 93% chance of having a septic hip. The next best step in management would be to take the patient to the operating room for an emergent irrigation and debridement of the affected hip.

Septic arthritis in the pediatric population often occurs in the first few years of life, with 50% of cases occurring in those less than 2 years of age. Patients may present with a toxic appearance. The likelihood of a patient having a septic hip can be ascertained with use of the Kocher criteria (WBC > 12, ESR > 40, T > 38.5 and an inability to bear weight on the affected hip). Patients meeting all four criteria have a 99% chance of having a septic hip, whereas those meeting just one of the criteria have a 3% chance of having a septic hip. Rapid breakdown of the hyaline articular cartilage occurs via enzymes (matrix metalloproteinases & hyaluronidase) produced by the bacteria. This may be mitigated with an emergent surgical irrigation and debridement.

Rutz et al. review septic arthritis of the pediatric hip. Diagnosis in infants may be difficult because this subset of patient do not always develop fevers. They recommend arthroscopic irrigation and debridement for those patients with an acute presentation and no evidence of osseous complications on radiographs. For those with a subacute presentation or radiographically visible complications of the femoral head, an open arthrotomy should be completed.

Pillai et al. studied the appearance of the pediatric acetabulum on ultrasound in comparison with plain radiographs. They suggest that a static ultrasound evaluation can be an effective method of screening for developmental hip dysplasia.

Figure A shows a patient with a hip effusion, holding the extremity in an flexed, abducted and externally rotated position. Figure B shows an ultrasound demonstrative of a joint effusion. The region of capsular distention can be seen anterior to the femoral neck.

Incorrect Answers
Answer 1: Observation is not indicated in this clinical scenario.
Answer 2: The hip ultrasound shown demonstrates an effusion; repeating the ultrasound will not change management.
Answer 3: Obtaining an MRI may be useful if the ultrasound were negative. It would help evaluate the extremity for evidence of osteomyelitis
Answer 4: As the patient is not septic, intraoperative cultures should be obtained prior to the administration of antibiotics.