Case 1: Shoulder the burden
A 13 year old presents with right shoulder and left chest pain in the setting of fever. The exam is significant for tenderness of the right shoulder and upper arm. The initial X-rays are negative. The patient subsequently underwent an MRI.
The patient subsequently went to OR for I&D and was MRSA positive.
Osteomyelitis in children is usually due to hematogenous seeding, usually in the metaphysis in children due to the risk blood supply. However in <18months it may be epiphyseal. Staph aureus is the the most common etiology in children, but Group B Strep may be seen in neonates.
Imaging from an ED standpoint should start with plain films. Remember, these may be negative, especially early on. Xray findings are seen at least 7-10 days in, and include osteopenia, periosteal reaction, or soft tissue effusion. High suspicion of osteomyelitis means admission with possible MRI if no improvement. CT has very little utility.
Unfortunately, this patient returned 3 days after discharge with increased pain and swelling. There was no fever, inflammatory markers were improving. An ultrasound of the right upper extremity was obtained.
This ultrasound shows a post-operative seroma. Remember, it is always important with ultrasound to obtain images of the opposite, healthy extremity when imaging as well as looking for a periosteal reaction.
Case 2: Limping along
Our second case is a 19 month old with limp and tenderness to the right hip for 3 days, with fever on the day of presentation to 100.4. Notable lab results include:
- CRP 1.5 ESR 43
- WBC 11.1 48% segs
Hip Xrays were obtained and were normal. Upon follow up at Orthopedics 5 days later symptoms had improved. The ultimate diagnosis was Transient Synovitis.
Transient Synovitis is sterile inflammation of the synovium, most common in 4-8 year old males, most commonly in the hip. In the ED, start with an AP, Lateral and Frog Log Hip Xray, which would evaluate for bony injury, avascular necrosis, SCFE. In transient synovitis, Xray will almost always be normal. Proceed to US if high clinical suspicion for TS. However, remember if fluid present, US does not indicate if septic. MRI is reserved for the most complicated cases
Kocher’s clinical criteria for septic arthritis
- Fever > 38.5C
- Non-weight bearing on affected side
- ESR > 40 mm/hr
- WBC >12k
Our toddler returned to ED 3 days later for refusing to sit up. He was noted to have a normal hip exam with refusal to ambulate and lower back tenderness. Notable labs at this visit include:
- CRP <0.4. ESR 53
- CBC stable
The hip ultrasound was normal, and the lumbar spine X-Rays were negative. Remember, when ordering a hip ultrasound the technique (and order) for effusion versus hip dysphasia are separate.
He was admitted and received a Bone Scan on the first day of admission which showed increased uptake in the L5/S1 disc space, highly suggestive of discitis/osteomyelitis.
He then underwent a CT scan of the spine.