Follow-Up
We phoned all the patients to ask about symptom recurrence, outside treatment, and satisfaction with RFA and to obtain informed consent to participate in our study. Only 1 of the 28 patients could not be reached and was lost to follow-up. Mean follow-up at time of study completion was 31.1 months (range, 5.2-55.8 months).
The 27 patients were asked a series of questions about their treatment: Have you had any recurrence of symptoms following treatment for your OO? Have you received treatment elsewhere? Were you satisfied with your treatment? Would you have the procedure again if you had a recurrence of symptoms?
Primary success was defined as complete pain relief after initial RFA with no evidence of recurrence at time of final follow-up, and secondary success was defined as presence of recurrent symptoms after initial RFA with complete pain relief after a second procedure with no evidence of recurrence.
Results
All RFAs were technically successful with adequate localization of the tumor nidus and subsequent probe placement within the lesion. There were no intraoperative or postoperative complications. All 28 patients were discharged home the day of procedure. Twenty-six patients (92.8%) experienced complete pain relief after primary RFA, had no evidence of recurrence at final follow-up, and denied symptom recurrence at time of study completion.
The other 2 patients reported symptom recurrence after the index treatment (1 proximal femur lesion, 1 distal femur lesion). One of these patients did well initially but had a recurrence about 2 months after the primary RFA; a second RFA provided complete resolution of pain with no evidence of recurrence at time of study completion. In the other patient’s case, intermittent pain persisted for 2 weeks after the primary RFA, and evidence of recurrence was documented 3 months after surgery; a second RFA was performed shortly thereafter, but the patient was subsequently lost to follow-up.
At time of study completion, all 27 patients who had been contacted by phone denied seeking additional treatment elsewhere and stated they would have the procedure again if their symptoms ever recurred.
Discussion
Osteoid osteoma is one of the most common benign tumors of bone. Over the past 2 decades, percutaneous RFA, in comparison with open excision, has emerged as a safe and effective treatment option with minimal patient morbidity.9-11 RFA traditionally has been performed by radiologists under CT guidance in the radiology suite. However, now orthopedic surgeons can obtain advanced intraoperative imaging beyond standard fluoroscopy. The Siemens Siremobil ISO-C3D fluoroscopic C-arm is an innovative intraoperative imaging device that functions as a standard fluoroscope but also generates 3-D reconstructions of surgical anatomy. The isocentric design and integrated motor unit allow the C-arm to move through a 190º arc while centering its beam directly on the area of interest. This data set is transferred to a computer workstation, where it is reformatted so that CT-quality images are generated in axial, sagittal, and coronal planes. This acquisition process takes only minutes, and the multiplanar images produced may be simultaneously displayed and manipulated on the screen in real time.
One concern about this technology is the amount of radiation exposure for patients, surgeons, and operating room staff. The device measures only radiation time, and the amount of exposure during that time depends on the volume and density of the radiated body. We did not calculate the amount of exposure for this study. Mean exposure time was between 20 and 40 seconds, reflecting the number of attempts required to localize the lesion and the surgeon’s experience with the technique. Although the potential for increased exposure is a valid concern, previous studies using this technology have demonstrated that a similar average exposure time is equivalent to that of standard CT, and that use of the device, over conventional techniques, potentially can lead to decreased overall radiation exposure.12,13
This series demonstrated that OO can be safely and effectively treated with intraoperative percutaneous RFA by an orthopedic oncologist. Our success rate is very similar to rates reported in the radiology literature. Studies are needed to confirm the efficacy of this novel technique in comparison with what has been reported in that literature. Given these promising preliminary results, and the relative ease of use and minimal learning curve associated with this technology, all orthopedic oncologists should be able to offer this treatment for OO. Furthermore, this technique allows orthopedic oncologists to provide appropriate definitive treatment and care directly, rather than by referring patients to radiologists.
In the treatment of OO, we reserve RFA for lesions involving the long and short bones of the upper and lower extremities, as well as selected flat bones, such as those in the pelvis. Although percutaneous RFA of spinal lesions has been reported in the literature, we think these represent a relative contraindication for this technique; image resolution, in our opinion, is not high enough to justify risking injury to the nerves in the spinal canal, lateral recesses, and neural foramina. In addition, given the radiation exposure, we recommend caution when using this technique for a pelvic or proximal femoral lesion in a woman of childbearing age.