16 y/o, Leg Pain after Activity

This was initially thought to be stress related and treated conservatively with rest.

Figures 1 and 2. (AP and Lat X-Rays) demonstrating dense sclerotic wavy periosteal reaction involving the posterior cortex of the proximal tibia.

Figure 3. (Coronal STIR bilateral legs) demonstrates marked posterior cortical thickening with prominent vascular grooves extending through cortex associated with marrow and adjacent soft tissue edema.

Figure 4. (Axial T1) demonstrates marked posterior cortical thickening with prominent vascular grooves extending through cortex associated with marrow and adjacent soft tissue edema.

Figure 5. (Sag STIR) demonstes marked posterior cortical thickening with prominent vascular grooves extending through cortex associated with marrow and adjacent soft tissue edema.

Figure 6. (Axial T2 Fat Sat) demonstrates marked posterior cortical thickening with prominent vascular grooves extending through cortex associated with marrow and adjacent soft tissue edema.

Figures 7-9. Lateral reconstruction of CT, axial CT, and coronal reconstruction demonstrating marked cortical thickening of posterior cortex of tibia with tubular lucencies extending through cortex (arrows).

Figures 10-11. Bone Scan (left = posterior view; right = anterior view) demonstrating single area of increased uptake involving proximal right tibia.

On clinical exam there was point tenderness to the proximal tibia.

An MRI was ordered for further work-up, which after reviewing, was then followed by a CT scan to evaluate for a potential osteoid osteoma nidus.

Linear vascular grooves are demonstrated in the cortex without radiation to a focal osteoid osteoma nidus.

The differential diagnosis at that time included chronic osteomyelitis, osteoid osteoma with a small nidus not detected on CT, unusual stress/insufficiency fracture possibly related to long term methotrexate use, or, less likely, sclerosing parosteal osteosarcoma.

A pediatric surgical oncologist was consulted and a needle biopsy was first performed, which was non-diagnostic.

Chronic nonbacterial osteomyelitis (CNO) is a sterile osteitis of unclear etiology.

Non-osseous organs can also be involved with inflammation, including the eyes, skin, gastrointestinal tract, and lungs.

CNO is diagnosed by exclusion after ruling out other potential causes such as malignancies such as sclerosing parosteal osteosarcoma or Ewing sarcoma.

Non-steroidal anti-inflammatory drugs (NSAIDs) have been recommended as a first-line therapy and seem to be safe and effective.