Intraoperative localization of an osteoid osteoma using a gamma probe

Osteoid osteoma is a benign but painful bone-forming tumour which can be cured by complete surgical excision of the nidus. Since osteoid osteomas may be situated in a location of difficult accessibility, exact intraoperative localization is needed to remove the tumour completely without unnecessary sacrifice of surrounding bone. The purpose of the our study was to examine the applicability of gamma probe in the intraoperative localization of osteoid osteoma.26 patients who had a presumptive diagnosis of osteoid osteoma and were submitted to surgical treatment were included in this study. 16 patients were males and 10 were females with ages ranging from 6-45 (mean 19.6) years. Patients were each injected intravenously with the appropriate dose (15-20 mCi for adults and a lower, adapted dose for children) of Tc99m-MDP 3 to 4 hours before operation. Bone scan was obtained immediately prior to operation. İntraoperatively, before the skin incision is made, the prob is passed over the area for approximate localization. After the bone was exposed, counts rates in the lesion and adjacent normal bone, after excising the lesion, counts of the cavity were established. The cavity was widened until it?s counts approximated to the level of the counts of the adjacent normal bone. The clinical outcome was determined by postoperative pain relief. Histopathology studies were directed to identifying nidus in samples.The preoperative scintigram revealed a hot spot in every patient in a location correlating well with the lesion on CT. İntraoperatively the lesion could be localised by the gamma probe in every patient. The background radioactivity from adjacent normal bone was 221.330±91.93 while the lesion was 897.110±208.088 counts (p<0.001). Lesion/ normal mean ratio was 4/1. After the resection, we found a mean decrease of the count rate at the tumour site of %62 (%30-%90) and radioactivity from cavity was 338.111±153.647 while the lesion was 897.110±208.088 counts (p<0.001).21 patients were confirmed to be osteoid osteoma on pathological examination. Postoperatively, all patients were relieved their symptoms but except one. The mean follow- up was 18 months (range 8-25) and one recurrence was encountered. Except the osteosarchoma, the other bone lesions included 2 infection, 2 enchondroma were successfully localized and excised during surgery using gamma probe.Finally, the preoperative injection of Tc99m-MDP and intraoperative localization by the use of gamma probe is a simple and safe technique which helps to locate the osteoid osteoma nidus at operation. Thus the removal of bone can be guided, allowing limited but complete surgical resection of the tumour.