TREATMENT OF OSTEOID OSTEOMA BY CT GUIDED DRILL RESECTION - A REPORT OF 27 CASES

Purpose of the study Osteoid osteoma is a benign tumor requiring excis ion due to pain, usually severe and invalidating. Surgical << en bloc >> resection is not always easy. Complete resection of the nidus is re quired to prevent recurrence while at the same time a limited resectio n should also be used to avoid a pathological fracture or a growth pla te injury in children. In order to achieve these 2 goals, we have deve loped an alternative method: CT guided drill resection. This method is reported with special reference to its technical aspects. Material an d methods Twenty seven patients (16 children and 11 young adults) were treated during a seven year period (June 87 through June 94) and obse rved clinically and radiologically with an average two-year follow-up (range one to three years). Osteoid osteoma was localized mainly in th e lower limb : Femoral neck (or head) 10 cases, 3 in the acetabulum; F emoral shaft: 6 cases; Tibial shaft: 4 cases. Diagnosis was based on c linical features and imaging: radioisotope bone scan and computed tomo graphy in all cases - angiography in 3 patients to assess the diagnosi s more accurately. The procedure was performed under general anesthesi a (a short hospitalization is needed). The nidus was first localized b y Computed Tomography, then approached and resected through a small pe rcutaneous incision. A special device has been manufactured in order t o remove a bone cylinder containing the nidus. It was thus possible to perform histological studies of the specimen and confirm the diagnosi s. Histological confirmation was possible in 50 per cent of the cases. No complication (except a case of transient extensor hallucis palsy) was observed in this series, 24 patients healed completely; pain disap peared immediately, and the control CT scan returned to normal after a one-year follow-up. In 3 patients, because of a technical error, the nidus was not totally removed. These patients underwent a second proce dure, which was effective. Discussion This method is a good alternativ e to the direct surgical approach because of its technical advantages: precision in nidus localization and minimal bone resection; consequen tly, one should underline the practical benefits for the patient short hospitalization, immediate full weight bearing, quick return to socio -economic activities. Furthermore, some localizations of the nidus whi ch are difficult to reach (for instance the acetabulum) represent a go od indication for the method. Accurate pre-operative diagnosis has now become possible with recent advances in imaging techniques but still remains << uncertain >>. The resection of the specimen allows confirma tion of the diagnosis is most of cases. This procedure should ideally be performed by a team (orthopedic surgeon and a radiologist) : collab oration instead of competition is in fact the best way to progress in this field of << interventionnal radiology >>.