Case Report: Osteoid Osteoma of the Acetabulum Treated With Arthroscopy-assisted Radiofrequency Ablation

Osteoid osteomas consist of a nidus surrounded by reactive sclerotic bone. The diagnosis typically is based on imaging and clinical presentation involving nocturnal pain. Removal of the lesion is essential and currently is performed mainly with image-guided, minimally invasive techniques. We describe a case involving an osteoid osteoma of the acetabular fossa, treated with arthroscopy-assisted radiofrequency ablation. A 47-year-old woman presented with a 9-month history of right groin pain and limited motion. The CT and MR images showed synovitis around the ligamentum teres and a nidus of the acetabular fossa, surrounded by sclerotic bone and protruding from the inner part of the lamina quadrilateral. Synovectomy and debridement of the ligamentum teres were performed, followed by radiofrequency ablation of the osteoid osteoma under direct arthroscopic observation of the hip, avoiding resection of the normal bone around the nidus and preserving the integrity of the quadrilateral lamina and cartilage. The patient had complete pain relief the next day with minimal morbidity and rapid functional restoration. At the 22-month clinical followup, the patient was asymptomatic, and the CT and MR images obtained 1 year after surgery showed no pathologic signs or synovitis. Our case was the fifth such case to be treated with hip arthroscopy and the first of these to our knowledge to be treated with the arthroscopy-assisted radiofrequency ablation technique. Arthroscopy-assisted radiofrequency ablation is a combined treatment technique that may be used for intraarticular lesions of the hip that otherwise would require a difficult approach and jeopardize damage to cartilage and bone and also treat concomitant synovitis.