# Juxta-Articular Osteoid Osteoma With Inflammatory Femoroacetabular Impingement: A Case Report

## TL;DR

A 15-year-old girl's hip pain was caused by a rare juxta-articular osteoid osteoma that mimicked inflammatory femoroacetabular impingement, which was resolved after surgery.

## Contribution

First reported case of juxta-articular osteoid osteoma causing inflammatory FAI, highlighting diagnostic challenges.

## Key findings

- Computed tomography identified a bone translucency with internal calcification at the femoral neck, suggesting a nidus.
- Surgical resection of the osteoid osteoma led to rapid resolution of the patient's pain.
- The case highlights the importance of distinguishing between inflammation and FAI as sources of hip pain.

## Abstract

Inflammatory femoroacetabular impingement (FAI) is a cam lesion caused by inflammation and is characterized by a distinct bone deformity. To date, no reports have described bone deformities resulting from juxta-articular osteoid osteomas that resemble those seen in inflammatory FAI. We report a case of a 15-year-old girl who presented with right hip pain, hip arthritis, and a cam deformity at the femoral head-neck junction. Computed tomography revealed a bone translucency with internal calcification, suggestive of a nidus, at the medial cortex of the right femoral neck. Based on these findings, we diagnosed inflammatory FAI caused by juxta-articular osteoid osteoma. Following resection, her pain resolved rapidly. This is a rare reported case of juxta-articular osteoid osteoma causing inflammatory FAI. Understanding the characteristics of inflammatory FAI can aid in distinguishing between inflammation and FAI as the source of pain.