BackgroundThe aim of this study was to document the optimal spacing of two cannulae to form continuous strip lesions and maximal surface area by using water-cooled bipolar radiofrequency technology.MethodsTwo water-cooled needle probes (15 cm length, 18-gauge probe with 6 mm electrode tip) were placed in a parallel position 10, 20, 24, 26, and 28 mm apart and submerged in egg white. Temperatures of the probes were raised from 35℃ to 90℃ and the progress of lesion formation was photographed every 1 minute with the increase of the tip temperature. Approximately 30 photographs were taken. The resultant surface areas of the lesions were measured with the digital image program.ResultsContinuous strip lesions were formed when the cannulae were spaced 24 mm or less apart; monopolar lesions around each cannula resulted if they were spaced more than 26 mm apart. Maximal surface areas through the formation of continuous strip lesion were 221 mm2, 375 mm2, and 476 mm2 in 10, 20, and 24 mm, respectively. Summations of maximal surface area of each monopolar lesions were 394 mm2 and 103 mm2 in 26 and 28 mm, respectively.ConclusionsWater-cooled bipolar Radiofrequency technology creates continuous "strip" lesions proportional in size to the distance between the probes till the distance between cannulae is 24 mm or less. Spacing the cannulae 24 mm apart and treating about 80℃ for 24 minutes maximizes the surface area of the lesion.

Background: Owing to the anatomical difference between the far lateral herniation of the lumbar disc (FHLD) and the intraspinal herniation of lumbar disc (iHLD), the outcome of transforaminal epidural steroid injections (TFESI) in patients with FHLD seems to be different from that in patients with iHLD. However, few studies have evaluated the efficacy of TFESI in FHLD. Objective: To evaluate and compare the efficacy of TFESI in FHLD and iHLD patients. Study Design: A retrospective design. Methods: There were 15 and 70 patients in the FHLD and iHLD groups, respectively. Patients received a fluoroscopically guided TFESI. Failure rates of TFESI were recorded, and questionnaires, including a visual analog scale (VAS) for leg pain and Oswestry Disability Index (ODI) were administered before the initial injection, at 2 weeks, 6 weeks, and 12 weeks after the injections. Results: There was no failure for TFESI in the iHLD group, while 9 patients had to undergo alternative blocks in the FHLD group due to lancinating leg pain when the needle was advanced for TFESI. In the iHLD group, there was a statistically significant improvement in the VAS and ODI score 12 weeks after injection. Considering only successful cases of the FHLD group, significant improvement in the VAS and ODI score was also demonstrated in the FHLD group 12 weeks after injection. Moreover, there was no statistically significant difference of the VAS and ODI between the both groups. Limitations: A relatively small numbers of cases were included in the FHLD group. Conclusion: The current study suggests that an alternative needle placement technique for TFESI appears to be necessary for FHLD patients. Key words: Far lateral herniation of lumbar disc, intraspinal herniation of lumbar disc, transforaminal epidural steroid injection, safe triangle, herniated lumbar disc, visual analog pain scale, Oswestry disability index, radiculopathy