Patients with symptomatic Cesarean Scar Defect (CSD) who are expected to undergo hysteroscopic surgery will be randomly divided into the traditional hysteroscopic "channelization" treatment group and the hysteroscopic "360 °" Surgery group of cesarean diverticulum, and the improvement of postoperative clinical symptoms of the two groups will be compared. To evaluate the effectiveness of the two surgical methods.

The purpose of this study was to evaluate the improvement of symptoms of women with symptomatic cesarean diverticulum through a high-quality randomized controlled study, in order to provide high-level evidence-based medical evidence for clinical treatment.

1. Study Design：This is a prospective, randomized controlled trial.

2. Study population 120 patients diagnosed with Cesarean Scar Defect (CSD) will be prospectively recruited. Before the surgery all patients will undergo preoperative evaluations, including a detailed history of the menstrual pattern,any previous History of cesarean section, and reproductive history, as well as trans-vaginal ultrasonography and Three-dimensional SIS Ultrasound.

3. Randomization:

   Randomization was performed electronically using SPSS statistical software version 26.0 (SPSS, Inc., Chicago, IL,USA) by the investigator.120 recruited patients will be randomized to one of the two treatment groups by computer-generated numbers: the control group("channelization" group) and the experimental group("360°" group).

4. Surgical technique:

   Hysteroscopic surgery will be performed in a standardized manner.The procedure will be performed under general anesthesia. Ultrasonographic guidance will be routinely used.

   The interference of "360°" group (the experimental group) including 60 CSD patients ,With the vaginoscopic approach, the isthmocele was localized; a high-frequency 90°angled circular loop electrode and pure cutting current of 100 W were used to resect the fibrotic tissue of the proximal (step 1) and distal (step 2) part of the niche. The investigators performed resection not only of the fibrotic tissue underneath the niche but also of the inflamed tissue placed around the niche and on the opposite site (the so-called channel-like 360° endocervical ablation). A high-frequency angled ball electrode was used to obtain focused coagulation of all residual inflamed tissue still present on the niche surface and on the cervical canal walls (step 3); the aim of this step is to facilitate the re-epithelialization of the cervical canal walls by the paraphysiological endocervical epithelium. The procedure was ended by controlling any bleeding of the endocervical vessels by reducing the inflow and pressure of the distending medium and by focused electrocauterization with a ball electrode (step 4).while the interference of "channelization" group (the control group) , With the vaginoscopic approach, the isthmocele was localized; a high-frequency 90°angled circular loop electrode and pure cutting current of 100 W were used to resect the fibrotic tissue of the proximal perform intrauterine adhesiolysis with bipolar electric needle electrode, part of the scar tissue removed by electronic loop when it is necessary.A angled ball electrode was used to obtain focused coagulation of proliferating blood vessels, inflammatory tissue, and ectopic endometrium in the diverticulum.In both arms, the endometrium tissue was removed and sent to pathology, followed by immunohistochemical CD138 examination

5. Postoperative treatments All subjects will be treated with oral antibiotics for 3 days. Three-dimensional SIS Ultrasound will be carried out 3 months after the surgery.

6. Follow up:

   Follow-up styles: the doctor's outpatient review, patients fill in questionnaires,telephone, WeChat and so on.

   Follow-up time:3 months and 6 months after the operation. Follow-up contents: the data measured by 3D-SIS,At the same time, the endometrium was taken again for immunohistochemical CD138 examination. Assessed the improvement of symptoms, including the improvement of prolonged menstrual period, the improvement of heavy menstruation, and the patient's postoperative satisfaction.

7. Consent： All subjects will be given a detailed explanation of the study and sufficient time to consider their participation. A written consent form will be signed by the patient and retained in the records.

Inclusion Criteria:

• Patients with surgical adaptation: changes in menstruation after cesarean section (prolonged menstrual period)
• No surgical contraindications;
• Age 18-45 years old;
• The thickness of residual muscle layer measured by ultrasound is greater than or equal to 2.5mm;
• Patients with symptoms that have not improved significantly for more than 1 month after oral short-acting contraceptive cycle treatment or who strongly require surgery;
• Understand and agree to the research plan.

Exclusion Criteria:

• Patients with other diseases that may cause abnormal uterine bleeding (including endometrial polyps, endometrial hyperplasia, submucosal myoma, etc.) indicated by two-dimensional ultrasound
• There are contraindications of surgery: such as severe internal and surgical complications, pregnancy, reproductive tract infection, malignant tumor;