Pulsed radiofrequency treatment was performed aseptically. The subject was laid in the supine position under fluoroscopic control using a C-arm (Arcadis Orbic, Siemens, Germany). A 22-gauge cannula SMK Pole needle 54 mm long with a 4 mm active tip (Cotop International BV, Amsterdam, Netherland) was placed around the dorsal root ganglion that lie within the intervertebral foramen. The cannula was inserted over the caudal and posterior parts of the intervertebral foramen and its tip was placed at the border between the center and one third of the caudal part from the posterior neural foramen. The catheter needle was then inserted and positioned as near as possible to the dorsal root ganglion with the aid of a radiofrequency generator RFG-1A (Cosman Medical Inc., MA, USA), and a sensory stimulation test was performed. When abnormal sensation or pain was observed with a stimulation of less than 0.3 V, the catheter needle was considered to be placed near the dorsal root ganglion. When sensory stimulation was not achieved, the catheter needle was inserted more deeply into the intervertebral foramen until the subject complained of a dull pain; however, the needle was not inserted beyond the lateral half of the articular mass seen on an anteroposterior view. The radiofrequency generator was set so that the temperature of the catheter needle tip would not exceed 42℃ and a radiofrequency magnetic field was applied at 45 V for 120 seconds (Fig. 2).

A visual analog scale (VAS) was used to measure the intensity of the subjects' pain and the neck disability index (NDI) was used to evaluate the functions affected by this pain. These measurements were obtained prior to treatment and one and three months after treatment. The NDI consisted of 10 items - the intensity of pain, personal management (bathing and putting on clothes), raising objects, reading books, headache, concentration, working, driving, sleeping, and leisure activities. The score for each item was zero to five points and the total score ranged from zero to 50 points. An NDI score was calculated from the total of the scores for each item. A high NDI score indicated a more severe functional disability related to the cervical abnormality. In this study, the severity of functional disabilities due to pain was represented by a percentage (%) (disability in percent=(total score)/50×100). A successful treatment was defined as a reduction in pain of 50 percent or more compared with the VAS score prior to the treatment. Three months after pulsed radiofrequency treatment was performed, the subjects' degree of satisfaction with the treatment was recorded as "excellent," "good," "fair," or "poor." "Excellent" meant that the subject's level of satisfaction with treatment results was equal to his or her expectation. "Good" meant that although the subject's level of satisfaction was not up to his or her expectation, the subject was willing to receive treatment in case of another attack of pain. "Fair" meant that although the treatment was not ineffective, the subject was unwilling to opt for this treatment in case of another attack of pain. "Poor" meant that this treatment effect was similar to or worse than prior treatment effects. A third party who was blinded to the patients' conditions and treatment history evaluated questionnaires on pain and degree of satisfaction with treatment.19 SPSS 18.0 software was used for statistical analysis. Repeated measures of one factor analysis was employed to compare differences between time points through a contrast test to determine clinical progression. Significance was reached if the p-value was less than 0.05.