Video 1 (Scan the QR code to view): Traditional stitching technique

▲The video demonstrates a common traditional suturing technique, which includes the endometrium. After suturing, the endometrium is visible externally.

The uterine wall is divided into endometrial layer, muscle layer and serosal layer from the inside to the outside, of which the junction between the endometrium and the muscle layer (endometrial-muscle layer junction) has no protective submucosal layer and has a special anatomical structure. In order to pursue rapid hemostasis, traditional "full-thickness sutures" (also known as "large block sutures") use blunt separation followed by full-thickness locking sutures, which inevitably involve the endometrium (decidual during pregnancy) into the muscle tissue.

Due to the significant difference in the tissue characteristics of the endometrium and the muscle layer, the endometrium is brittle and tender, the healing ability is weak, while the muscle layer is tough and rich in blood supply. Clinical data show that the average depth of scar diverticula after traditional suturing is 4.9mm, the thickness of the residual muscle layer is only 3.8mm, the risk of uterine rupture is 4 times higher than that of the normal population (OR=3.95), and the incidence of placenta accreta is also significantly increased. In addition, scar diverticulum can also cause prolonged menstruation and irregular bleeding due to the accumulation of menstrual blood, which seriously affects the quality of life of patients.

Figure 1: Pathological status of the uterus after traditional suturing shows niche shadow

Figure 2: Multi-view image of hysteroacoustic contrast of cesarean section scar defect

Figure 3: Anatomy of the uterine wall

The core principle of "suture-free endometrium" suturing technology is "anatomical reduction and homologous healing", that is, accurately identify the three-layer structure of the uterine wall, only perform layered suturing of muscle tissue, deliberately avoid the endometrium, and avoid mixed healing of different characteristic tissues, so as to optimize the quality of incision healing.

The operation requires first separating the vesicloperitoneal reversal (bladder flap) to fully expose the lower part of the uterus and ensure that the incision is chosen in the lower part of the uterus (avoiding the dilated cervical canal) to reduce the risk of endocervical involvement. The layers can be quickly distinguished by the color, texture and bleeding characteristics of the tissue: the muscle layer is reddish-brown, the texture is uniform and tough, the bleeding is abundant and bleeding; The endometrium is pinkish-white or reddish, crisp and tender, and only a small amount of blood oozing on the surface; There is a distinct color and texture transition zone at the junction of the two, which is a key marker for identification.

2. Layered suturing operation process

At present, the specific steps of double-layer suturing technology commonly used in clinical practice are as follows:

The first layer (deep muscle layer suture): starting from the corner of the incision, continuous locking suture is adopted, and the needle penetration depth reaches 1/2 of the thickness of the muscle layer, accurately passing through the endometrial and muscle layer junction area, but not penetrating the endometrial layer, and the needle distance is controlled at 3-5mm to ensure that the edge of the muscle layer is tightly aligned and avoid leaving dead space. At the heart of this layer is aligning the deep muscle layers, setting the stage for incision healing.

The second layer (superficial muscle layer + serous layer suture): starting from the opposite angle of the incision, continuous hem suturing is also used, and the remaining 1/2 muscle layer and serous layer are sutured, and the first layer of sutures is completely covered and wrapped, further strengthening the incision tension and reducing postoperative blood leakage.

Peritoneal closure: Finally, the bladder uterine peritoneum is continuously sutured with fast-absorbing barbed sutures to cover the incision surface, reduce the direct contact between the muscle layer and the abdominal organs, and reduce the risk of abdominal adhesions and bladder displacement.

Some studies have also confirmed that the "slit-free intima technology" with non-locking suturing on both layers can also achieve good results, which can be selected according to the operator's operating habits, but the core principle is always to avoid the endometrium and ensure accurate alignment of the muscle layer.

3. Key technical considerations

During suturing, it is necessary to maintain "sharp separation" to avoid blurring of tissue levels caused by blunt separation, and to ensure that the boundary between the endometrium and the muscle layer can be clearly identified.

The depth of needle insertion and withdrawal should be accurately controlled to avoid poor alignment caused by too shallow, or too deep penetration of the endometrium;

For patients with thin lower uterine segments, appropriate adjustment of needle spacing and suture tension should be adjusted to avoid excessive traction leading to muscle ischemia and necrosis.

Video 2 (scan the code to watch): "No seam inner film" suturing technology

▲The video shows the "suture-free intima suture" suturing technology used in a repeated cesarean section. The video demonstrates the external state of the uterus and the hierarchical structure of the uterine wall. The needle is inserted at an angle during suturing, penetrating the entire layer of the muscle layer and avoiding the endometrium.

A number of high-quality clinical studies have confirmed the significant advantages of "suture-free intima membrane" suturing technology, providing solid evidence for its clinical application:

A team from New York University in the United States followed up 727 cesarean section patients using the "suture-free endometrium" technique for 30 years, and the results showed that none of the patients had uterine rupture or required hysterectomy due to placenta accreta; Among the 506 patients with re-pregnancy, the incidence of placenta previa was only 3.1%, which was significantly lower than that of the traditional suturing group (12.5%). Even after more than 2 cesarean sections, the depth of the scar diverticulum was still controlled within 2.4mm, and the thickness of the residual muscle layer was ≥7mm, which was far better than the traditional suturing effect. All subsequent pregnancies (836 times in total) did not have abnormal placenta accreta at the scar site, which fully reflected the advantages of this technology in reducing high-risk pregnancy complications.

2. Results of randomized controlled trials (RCTs).

An RCT study of 274 patients showed that the incidence of scar diverticula in the "suture-free intima group" group was only 15.4% at 6 months after surgery, compared with 29.6% in the traditional full-thickness suture group (P=0.03). Another RCT compared the three suturing methods and found that the average postoperative residual muscle layer thickness of the "suture-free intima membrane" technique group was 6.1 mm, which was significantly thicker than that of the traditional single-layer suture group (P<0.001), and the residual muscle layer thickness was a key indicator for predicting the risk of long-term uterine rupture.

3. Meta-analysis corroboration

The latest meta-analysis published in June 2025 combined data from 6 studies (including 4 RCTs) with a total of 491 patients and confirmed that the risk of scarring diverticula was reduced by 47% (RR=0.53, 95% CI 0.34-0.82) and the incidence of abnormal vaginal bleeding by 58% during cesarean section. Some subgroup analyses showed that the risk reduction effect of this technique was more significant in people with multiple cesarean sections (some studies reported RR as low as 0.33), but the core conclusion was still based on the results of pooled analysis.

In addition, studies on high-risk groups of multiple cesarean sections have found that endometrial involvement and suturing increase the risk of clinically significant scar diverticula by 5.6-11 times, and the "suture-free endometrium" technology can still effectively control the occurrence and development of scar diverticula even in patients with multiple cesarean sections.

The "suture-free endometrium" suturing technology is more suitable for elective cesarean section (such as abnormal fetal position, scar uterus re-cesarean section, etc.) and cesarean section in the early stage of labor, when the lower part of the uterus has not been overstretched and thinned, and the boundary between the endometrium and the muscle layer is clear, which is convenient for accurate identification and layered suturing, and can maximize the technical advantages.

2. Limitations and precautions

There are also certain limitations to the application of this technique: in the case of emergency cesarean section (such as fetal distress, uterine rupture) or cesarean section in the second stage of labor, the lower part of the uterus is overstretched and thinned, or the anatomical layer is blurred due to uterine twisting and incision tearing, making it difficult to accurately identify the boundary between the endometrium and the muscle layer. In addition, this technology requires high anatomical cognition and suturing skills of the surgeon, and needs to be carried out after systematic training to avoid poor incision healing due to improper operation.

At present, most studies use absorbable polylactic acid sutures, and more research is needed to further verify the effect of different suture materials on the effect of this technology. At the same time, future studies should also pay attention to subjective outcome indicators such as postoperative pain and quality of life of patients to provide a more comprehensive basis for technical optimization.