# Intra-Articular Osteoid Osteoma of the Trapezoid Bone: A Rare Presentation Mimicking Wrist Synovitis

## TL;DR

A rare case of osteoid osteoma in the trapezoid bone was misdiagnosed as wrist synovitis before correct diagnosis and successful surgery.

## Contribution

Highlights the diagnostic challenges of intraarticular osteoid osteoma in atypical locations like the trapezoid bone.

## Key findings

- Standard imaging misdiagnosed the condition as synovitis.
- CT scan and histopathology confirmed the osteoid osteoma diagnosis.
- Surgical excision resolved all clinical symptoms.

## Abstract

Osteoid osteomas predominantly occur in the cortices of long bones, with the femur and tibia being the most commonly affected sites. However, they can occasionally present in atypical locations, such as the carpus, which can lead to diagnostic confusion with other conditions. This case report details an intraarticular osteoid osteoma in the trapezoid bone. Initial evaluations, including standard radiographs, joint ultrasound, and wrist MRI performed twice, initially pointed toward a diagnosis of wrist synovitis. This case underscores the diagnostic challenges posed by atypical presentations of osteoid osteomas. Given the edema present in the carpal bones alongside the synovitis, we performed a hand CT scan, which raised doubts about the appearance of the nidus and histopathological examination confirmed the diagnosis. Clinical symptoms, including pain and functional limitations, were completely resolved following surgical excision.