Participants
This study followed the International Conference on Harmonisation of Good Clinical Practice guidelines and the Declaration of Helsinki (2008).With the approval of the Ethics Committee of the Third Xiangya Hospital of Central South University (No. 23863) to waive the requirement for signed informed consent, a retrospective medical record analysis was conducted on patients with ZAP who were hospitalized in the Department of Pain at The Third Xiangya Hospital, Central South University, from October 2019 to October 2023. Inclusion criteria were as follows: age over 18 years, meeting the diagnostic criteria for ZAP, lesions affecting the cervical, thoracic, or lumbar segments, inability to control pain with conventional treatments, and undergoing either SCS treatment or a combination of SCS and PRF treatment. Exclusion criteria included: insufficient medical records (lack of baseline data or follow-up records at 6 months post-treatment), experiencing other significant medical conditions during the follow-up period, and receiving other interventional therapies during the follow-up period.
Patients who received only SCS treatment were defined as the SCS group, while those who received both SCS and PRF treatments were classified as the SCS+PRF group. According to the course of the disease, acute pain was defined as pain occurring within 1 month, pain persisting for more than 3 months was considered as PHN, and subacute pain was defined as lasting between 1 to 3 months[1].
Surgery
Spinal cord stimulation
The surgical procedure for SCS has been detailed previously[22]. Briefly, the target spinal segment for electrode implantation was determined based on the affected pain area, and the electrode position was confirmed by intraoperative fluoroscopy. The patient was placed in a prone position, and after local anesthesia, an epidural puncture was performed with a 14G Tuohy needle. The core was removed once the needle entered the epidural space, and an 8-contact lead (3873; Medtronic, Minneapolis, MN, USA) was inserted through the cannula. The lead was advanced under fluoroscopic anteroposterior view, and a sensory test was conducted to ensure that the electrical stimulation covered the patient's pain area. Patients were asked to remain in bed for 2 days to avoid potential lead migration. Those with lead displacement and dislocation were excluded from the study. The stimulation frequency was set to 50 Hz, and the pulse width was 500 μs. The electrical stimulation voltage was adjusted according to the degree of pain. Stimulation leads were removed within 2 weeks after surgery to prevent infection.
DRG PRF
PRF treatment was performed about one week after SCS. As described[23], for DRG PRF, the patient was placed prone on the operating table with a comfortable pillow under their chest. The needle was guided into the thoracic paraspinal space using B-scan ultrasound (Fujifilm Sonosite, Bothell, WA, USA). The needle tip was fine-tuned based on the ultrasound probe scan to the target segment. X-ray imaging confirmed that the needle tip was directly below the lateral border of the pedicle in the anteroposterior view and in the superior quadrant dorsal to the foramina in the lateral view (Fig 1). The internal needle was replaced by a pulsed radiofrequency electrode, connected to a standard clinical specification radiofrequency generator (Beiqi, R-2000BA1, Beijing, China). The position of the needle tip was controlled by sensory and motor nerve stimulation before proceeding. DRG PRF treatment was set at 2 Hz (20 ms pulse width) three times for 240 s. Impedance was maintained at less than 300Ω throughout the procedure.
Clinical outcomes and follow-up
The primary data analyzed included changes in the intensity of patients' pain, evaluated using the Visual Analog Scale (VAS), which ranges from 0 ("no pain") to 10 ("the worst pain imaginable"). Preoperative information included age, gender, duration of disease, and baseline VAS score upon admission. Postoperative data included VAS scores at discharge, VAS scores 6 months after surgery, whether patients in the acute and subacute phases progressed to PHN, and the occurrence of treatment-related complications (including pneumothorax, bleeding, infection, nerve injury, and electrode displacement). During postoperative follow-up, a reduction in VAS score of 50% or more compared to the baseline score upon admission was defined as a responder[13].
Statistical analysis
Prism 9.0 software (GraphPad, San Diego, CA, USA) was used for statistical analysis. Continuous variables were expressed as mean ± standard deviation. Two-way analysis of variance with repeated measures and post-hoc multiple pairwise comparison using Sidak's test was employed to assess changes in pain scores between the two groups over time. Differences in response rates were compared using χ2 tests (including possible χ2-corrected tests and Fisher's exact test). A P value of less than 0.05 was considered statistically significant.