2 The procedure
2.1.1 Osteoid osteomas are benign, bone-forming tumours that occur most frequently in the legs, especially in the femur and tibia.
2.1.2 Almost all patients have pain as a result of the tumour. Other symptoms include growth disturbances, bony deformity, scoliosis and, if located within a joint, swelling, synovitis, restricted movement and contracture. This condition may regress spontaneously, but the resolution of symptoms is unpredictable and may take months or years.
2.1.3 Standard treatment initially focuses on pain management using non-steroidal anti-inflammatory drugs. Patients who continue to have pain or who experience other tumour-related complications are offered surgical excision. Surgery requires a hospital stay of several days and the patient cannot undertake weight-bearing activity for a substantial period of time. Aggressive resection carries the risk of postoperative fracture, infection and haematoma.
2.1.4 In recent years several minimally invasive techniques using imaging, such as percutaneous resection and radiofrequency ablation, have been introduced in patients with osteoid osteoma in order to achieve removal or destruction of the tumour without the subsequent morbidity of standard surgical treatment.
2.2.1 In this procedure, the lesion is located using computed tomography (CT). Under general anaesthetic, an entry hole is created through the bone using a fine drill. A radiofrequency electrode probe is introduced into the centre of the osteoma and heated. The electrode is then removed and a CT scan is done later to assess the outcome of the procedure
2.3.1 Resolution of pain was the main outcome reported in the studies. In a case series of 97 consecutive patients with a mean follow up of 41 months, 76% (74/97) of patients reported a good response after one treatment session and 92% (89/97) reported a good response after one or two sessions. In the smaller studies, resolution of symptoms was reported by 82–95% of patients at final follow up. For more details, refer to the Sources of evidence section.
2.3.2 The Specialist Advisors considered that this was an established procedure with no concerns or uncertainties about its efficacy. One Advisor stated that the procedure was better than open surgery as there is less risk of recurrence.
2.4.1 Few complications were observed in the studies. Five out of 239 patients (2%) experienced complications, including three who experienced superficial burns. For more details, refer to the Sources of evidence section.
2.4.2 The Specialist Advisors noted transient pain as the most common complication of the procedure. Infection was also listed, but described as a rare adverse event. It was noted that if the tumour is in a difficult area, adjacent structures may be at risk from inappropriate positioning of the electrode, but Advisors commented that the procedure is still safer than surgery in similar situations.