Study design and participants
In January 2016, the First Affiliated Hospital of Zhejiang University School of Medicine (tertiary hospital) introduced the Medtronic neuromodulation technique for clinical use. This was a case series of patients who met the diagnosis of neurogenic bladder and received SNM between January 2016 and April 2019. The study was approved by the ethics committee of the First Affiliated Hospital of Zhejiang University School of Medicine. The participants provided a signed informed consent form.
The inclusion criteria were: 1) diagnosis of neurogenic bladder by urodynamic imaging examination [1]; and 2) willing to participate in this study.
Perioperative management
The participants were encouraged to perform pelvic floor muscle training exercises before surgery through continuous contraction of the pelvic floor muscles (anus levator movement) for 2-6 s, followed by relaxation and rest for 2-s, repeated 10-15 times, 3-8 times every day.
Detailed steps of SNM
The prone position was taken, and the lower abdomen and the calves were elevated to ensure that the toes were suspended. The body surface was marked with bilateral S3 sacral nerve holes, and the needlepoint was about 2 cm above the marked point. The puncture needle pointed to the tail at a 60-degree angle and was pushed into the S3 sacral nerve hole perpendicular to the sacrum surface under x-ray radiography. The temporary stimulator was connected. The tested pulse width was 150-300 µs (conventional pulse width was 210 µs), the frequency was 9-40 Hz (the initial setting was 14 Hz), and the voltage was 0.5-5 V (ideally no more than 2 V). The motor (plantar flexion of the big toe) and sensory responses (rectal tractive feeling, extending forward to the scrotum or labia) of the S3 sacral nerve of the patient were tested. In case of no response at S3, S4 was used. When a response was achieved, Agnail-like permanent electrodes were implanted, and the motor and sensory responses of each contact point were tested. A 3-cm incision above and outside the ipsilateral hip of the electrode was made for the tail of the barbed electrode. The percutaneous extension wire was connected, and placed into a subcutaneous tunnel and tested again.
The stimulator was turned on 24 h after surgery. The time for experiencing stimulation was 1-2 weeks. According to the results of the intraoperative test, four sets of parameters were set: 0- 3+, 1- 3+, 2- 0+, and 3- 0+. Each group of parameters was observed for at least 3 days.
If the patient's symptoms improved significantly, implantation of the sacral nerve stimulator was performed. The original hip incision was opened, and the percutaneous extension wire opposite to the incision was removed. The electrode was connected to the sacral nerve stimulator through an extension wire and implanted into a free subcutaneous space. The impedance was tested, and the incision was closed. The cycle mode was selected: 20 s on, 8 s off (SoftStart 4 s). The control variable method was used during program control, i.e., only one parameter was adjusted at a time. The goal for program control after the second implantation was optimal symptom improvement. The stimulation parameters were optimized as much as possible to extend the battery life. The peri- and postinterventional complications were classified according to the Clavien-Dindo classification [14].
Postoperative guidance
During phase I SNM, the participants were asked to cooperate with the professionals to set specific points according to the response of the intraoperative test the next day after surgery, that was, to set the contact combination (four combinations: 0 negative and 3 positives, 1 negative and 3 positives, 2 negatives and 0 positive, 3 negatives and 0 positive) and to adjust the voltage, pulse width, and frequency to achieve the optimal stimulation.
For phase II SNM, on the first day after surgery, the participants underwent voltage regulation, replacement group, switch stimulator, and how to recognize the numbers and symbols on the remote control. The participants continued their urination diary and were followed 3-6 times. The postoperative-related data (urinary diary, personal emotion, urodynamic monitoring, etc.) and collection of data directly related to the treatment are the accuracy of ultimate success or failure [15]. The treatment and follow-up plan was timely adjusted with the evolution of the participants' condition. Each follow-up included a physical examination, a urinary diary, program-controlled stimulation parameter detection and/or adjustment, X-ray of the sacrococcygeal region, and X-ray in the lateral position.
The possible complications related to surgery included pain in electrode and stimulator sites, electrode displacement, injury, and infection [16].
Data collection
The evaluation of the participants' quality of life and urination diary (bladder symptom tracking form) included urine leaks, if urine pads need to be changed, urgent urination (0-5 points), urinary catheterization, and urinary output.
Evaluation of the participants' expected ideal and expected values
The participants' expected values were analyzed. The effect depended to a large extent on the participants' expectations and compliance with the treatment. An effect >50% was considered effective [17].
Statistical analysis
SPSS 22 (IBM, Armonk, NY, USA) was used to process the data. Continuous data were tested for normal distribution using the Kolmogorov-Smirnov test, were presented using means ± standard deviation, and were tested using the paired t-test. P<0.05 was considered statistically significant.