A Missed Case of Osteoid Osteoma of the Acetabulum Treated with a Novel Computed Tomography-Guided Technique – A Case Report

INTRODUCTION: Osteoid osteoma is a benign osteoblastic bone tumor that mostly arises from the long bones. The acetabulum is a rare site for osteoid osteoma. Moreover, juxta-articular location of the lesion can be associated with delayed diagnosis. We present a case of a juxta-articular osteoid osteoma of the acetabulum that was missed earlier. We also present a novel, easy, and cost-effective way to accurately localize and excise such a lesion, thereby avoiding failure and recurrence. CASE REPORT: A 15-year-old female presented with a history of insidious onset pain in the right hip for 18 months. Pain was diffuse over the hip. She had undergone a failed biopsy in another hospital. She visited us 1 month later with persistent pain. Examination revealed tenderness over the right anterior hip joint line with painful terminal hip flexion. Computed tomography (CT) suggested an osteoid osteoma of the superolateral acetabular rim. The patient was planned for CT-guided mini-open excision biopsy of the lesion. CT-guided localization of the lesion was performed under local anesthesia in the CT room, followed by open excision of the nidus in the operating room. Histopathology confirmed the diagnosis and a complete excision. At last follow-up at 1 year, the patient was asymptomatic and returned to normal function. CONCLUSION: Osteoid osteoma of the acetabulum is uncommon and the diagnosis is usually delayed. A high index of suspicion is needed to avoid a missed diagnosis and CT-guided approach can help in accurate excision. Our technique to localize and completely excise the lesion is novel, simple, and cost effective and can be easily replicated.