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.

MRI Shoulder: Subperiosteal abscess with associated osteomyelitis

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.

CT: Discitis/Osteomyelitis at the L5/S1 disc space, with small extrusion of cortical bone, and linear lucent tract extending across the L5 vertebral body much may be contiguouswith the osseous fragment

In children with discitis-osteomyelitis the disc space more likely to be infected than the vertebral body, because there is a rich blood supply to the disc, with then progression to osteomyelitis of the vertebral body from direct extension. Lumbar spine more common, Staph aureus is most common organism.

Evaluation in the ED should include an Xray, but unreliable. If there are findings, may be subtle disc height loss or osteopenia of the vertebral body. MRI is the best study. Unless there are neurologic deficits, can admit and perform the following day.

Evaluating a Limp: What does the American College of Radiology (ACR) recommend as the initial imaging modality?

Per the ACR Appropriateness Criteria:

If traumatic mechanism: XR should be primary imaging modality
If no trauma and no signs of infection: XR should be primary imaging modality, and if negative consider US Hip
If no trauma, possible signs of infection: US should be primary imaging modality, and if negative consider XR; If both are negative and still concerned for SA, MRI is the next imaging modality of choice

Case 3: This humerus injury is no laughing matter

This patient is a five day old with decreased use of right arm. The vitals are normal, and there is noted to not be movement of the right arm with moro reflex. Xray of the humerus and clavicle are normal. The newborn returned 48 hours later with decreased passive range of motion of the right elbow and pain with elbow movement.

The X-Ray demonstrates a comminuted fracture of the distal humerus with small fragments. AP view shows that the proximal radius and ulna are more medially positioned, which is concerning for transphyseal fracture with displacement of the non-ossified fragment.

In a transphyseal fracture the distal humerus shows physeal separation. The mechanism is birth trauma or fall on an outstretched hand if older. Non-accidental trauma should be in the differential. Recognition of this fracture is important because delay in treatment can lead to deformity.

Case 4: Cartwheels should not be attempted by the uncoordinated

The final case in this edition of The Reading Room is an 11 year old with pain in the left ankle after doing a cartwheel.

X-Ray with concern for a Tillaux fracture.

A CT was then obtained. CTs are useful in complex ankle fractures because they can give much better definition of three-dimensional fracture planes.

The Juvenile Tillaux Fracture is a Salter Harris III of the anterolateral distal tibia epiphysis caused by avulsion of the anterior inferiortibiofibular ligament. Mechanism of injury is supination and external rotation. Tillaux fracture typically occur in children nearing skeletal maturity (12-14 years old).