Unusual Presentation of Spinal Osteoid Osteoma: A Case Report

Osteoid osteoma (OO) is a benign osteogenic tumor that most commonly affects long bones, accounting for 2-3% of primary bone tumors. Spinal involvement is relatively rare, representing 6-20% of cases, with the lumbar spine being the most frequently affected region. Typical spinal OO presents with painful scoliosis and nocturnal pain relieved by non-steroidal anti-inflammatory drugs (NSAIDs). However, atypical presentations may occur when lesions are located adjacent to neural structures, leading to radicular symptoms and poor NSAID response. This case report describes an unusual presentation of OO in the L4 superior articular process, manifesting with back and leg pain, minimal NSAID responsiveness, and nerve root irritation.

A 17-year-old male presented with a 6-month history of back and leg pain, fluctuating between 3/10 and 7/10 in severity, with associated numbness in the L3 dermatome. Examination revealed painful paraspinal palpation and a positive straight leg raise on the right side, without motor weakness or reflex abnormalities. Magnetic resonance imaging demonstrated non-specific inflammatory changes, whereas computed tomography (CT) confirmed a 9 × 9 mm nidus in the right superior articular process of L4. Given the lesion's proximity to neural structures, radiofrequency ablation was deemed unsafe, and surgical excision was performed. The patient underwent open resection of the nidus with preservation of the inferior facet joint. Immediate post-operative resolution of leg pain was noted, and at 3-month follow-up, the patient reported complete resolution of both back and leg pain, with no recurrence of symptoms.

This case highlights an atypical presentation of spinal OO, characterized by radicular symptoms and poor NSAID response due to nerve root inflammation. It underscores the importance of considering OO in the differential diagnosis of adolescent back and leg pain, even in the absence of classic features. CT imaging remains essential for definitive diagnosis, and surgical excision provides safe and effective treatment when minimally invasive options are contraindicated by lesion proximity to neural structures.