Osteoid osteoma and osteoblastoma of the pelvis.

Benign osteoblastic tumors of the pelvis are rarely encountered in orthopedic practice. In most of the cases they involve the acetabular area, as was the case in nine of 14 cases of osteoid osteoma and osteoblastoma presented in this study. Especially with small tumors, such as osteoid osteomas, such a rare occurrence together with difficulties in the interpretation of roentgenograms can lead to mistakes and delays in diagnosis. To reduce these risks, a high grade of clinical suspicion and the use of tomograms or computed tomography (CT) scan and isotope bone scan are required. CT scan is an invaluable tool also for planning the surgical treatment in cases in which the tumor involves the acetabulum. Whereas an intracapsular excision is an adequate treatment for pelvic osteoid osteoma, pelvic osteoblastoma due to its size may need more aggressive surgery, even leading in some cases to a partial pelvic resection. The risk of recurrence is higher for osteoblastoma than for osteoid osteoma, as well as the rate of complications.