# Atypical Intra-articular Osteoid Osteoma Mimicking Slipped Capital Femoral Epiphysis: A Rare Diagnostic and Therapeutic Challenge in a Pediatric Patient

## TL;DR

A 10-year-old boy with hip pain was initially thought to have a common condition but was later diagnosed with a rare bone tumor, highlighting the importance of advanced imaging for accurate diagnosis.

## Contribution

This case highlights the diagnostic challenge of differentiating osteoid osteoma from SCFE in pediatric patients using advanced imaging.

## Key findings

- A lytic lesion in the femoral neck was identified as osteoid osteoma, not SCFE, through advanced imaging.
- CT-guided radiofrequency ablation with cryotherapy and NSAID infusion provided rapid pain relief and recovery.
- MRI and CT are essential for distinguishing between SCFE and osteoid osteoma when radiographs are unclear.

## Abstract

This case report describes a complex diagnostic challenge in a 10-year-old male presenting with persistent and progressively worsening hip pain. The initial clinical suspicion centered on slipped capital femoral epiphysis (SCFE), a common orthopedic condition in adolescents often associated with obesity and characterized by displacement of the femoral head at the growth plate. Standard radiographs suggested potential epiphyseal abnormalities, raising concerns for SCFE. However, subsequent advanced imaging revealed a 1 cm lytic lesion in the femoral neck with surrounding sclerosis, a classic radiologic feature of osteoid osteoma, thereby confirming the diagnosis.

The patient underwent successful treatment with CT-guided radiofrequency ablation (RFA) with adjunctive perilesional cryotherapy and intraoperative nonsteroidal anti-inflammatory drug (NSAID) infusion, resulting in rapid pain relief and expedited recovery. This case underscores the diagnostic overlap between SCFE and osteoid osteoma, as both conditions can manifest with hip pain and restricted range of motion in pediatric patients. It emphasizes the critical role of advanced imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT), in distinguishing between these two entities, particularly when initial radiographs are inconclusive.