Real time MRI-guided excision and cryo-treatment of osteoid osteoma in os ischii--a case report

A 36-year-old electrician had not been able towork during the last 8 months due to intense painin his left buttock. Plain radiographs were normal,but scintigraphy, MRI and CT indicated an osteoidosteoma in the left tuber os ischii. The patient wasgiven spinal anesthesia, and placed in a 0.5T GESigna SP/i open MRI (General Electric, Milwau-kee, USA) (Figure 1). With the patient in decubi-tus position, a surface coil was attached and thenidus located. A biopsy needle was placed in thecenter of the lesion, using an optical tracking sys-tem integrated in the magnet gantry, for placementof the needle. A 4 mm cylinder was cored out andfixed in formaldehyde for histologic examinationwhich confirmed the diagnosis osteoid osteoma.Then a 3 mm cryo probe (Galil Medical, Haifa,Israel) was placed centrally in the lesion (Figure2). 4 cycles (1/2–2 min) with cooling to –180€°Cinterrupted by passive thawing were used. ControlMRI showed the defect after the biopsy. The pa-tient was pain-free one day after the operation,soon resumed full-time work, and had no symp-toms 1 year later.