Purpose or Case Report: Acute osteomyelitis of the pelvis is an uncommon condition in pediatric patients, with involvement of the ischiopubic synchondrosis (IPS) being particularly rare and often presenting a diagnostic challenge. The bones surrounding the IPS are metaphyseal equivalents, akin to the metaphysis of long bones, which have a slower blood flow and are therefore more susceptible to acute hematogenous osteomyelitis. Additionally, prior to osseous fusion, the IPS appears lucent on radiographs, and fusion can occur asymmetrically across a broad age range. These characteristics complicate the radiographic assessment for IPS osteomyelitis. Patients typically present with unilateral groin or hip pain, restricted hip joint motion, limping, and difficulty bearing weight. Initial evaluations often involve plain radiographs, which may appear normal or show asymmetry at the IPS. The differential diagnosis includes stress reaction, osteomyelitis, post-traumatic osteolysis, or tumors. Laboratory tests, such as white blood cell count (WBC) and erythrocyte sedimentation rate (ESR), can help narrow the differential but may not yield a definitive diagnosis. MRI is the next best step for evaluating suspected osteomyelitis, although it is important to note that abnormal signal at the IPS can be present even in normal cases.

In this educational exhibit, we will: a) Review the factors that complicate the diagnosis of IPS osteomyelitis on plain radiographs, b) Illustrate the range of normal MRI appearances of the IPS, and c) Demonstrate the MRI findings of IPS osteomyelitis.
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