Cesarean section is the most frequent obstetrical surgery worldwide, with markedly increasing rates along the last several decades. The rising proportion of cesarean delivery is considered to have resulted from increased average age, obesity, development in obstetrical technology such as electronic fetal heart rate monitoring, and maternal request [1, 2]. In this regard, competent surgical technology regarding speed, safety, and efficacy is essential in operating cesarean section. Various new devices including scrub agents, retractors, and suturing products have been developed to support the necessary techniques and minimize maternal morbidity and mortality [3].

As one of the innovative materials, bidirectional knotless barbed suture has barbs aligned in a helical pattern, which are cut into a monofilament suture at approximately 1 mm intervals and progress in opposite directions from the small central part that is unbarbed. This suture reduces suture and operative time by eliminating the duty of tying knots, evenly distributes tension along the incision line, and provides possibility of improved cosmesis [4]. In recent years, numerous studies proved safety and efficacy of barbed sutures in gynecologic surgeries [5, 6, 7, 8] while there was little study about their usage in open surgeries [4, 9] and one metaanalysis showed insufficient safety measures in surgical fields [10]. However, some of recent trials demonstrated competence of knotless barbed suture in cesarean section as a reasonable alternative to conventional sutures, reducing closure time of uterine incision [11, 12]. But these studies did not evaluate cesarean section (CS) scars by postpartum ultrasound which is clinically useful method to determine CS scar integrity.

Transvaginal ultrasound is highly accurate in detecting CS scar integrity and dehiscence. CS scar dehiscence and myometrial thining are associated with uterine rupture, placenta previa, abrnormally adherent placenta, cesarean scar pregnancy, and abnormal uterine bleeding in non-pregnant patients [13, 14]. Labor precede CS and multiple cesarean deliveries are predisposing factors for dehiscence [14]. Assessment of CS scar status is becoming essential for clinical assessment of future pregnancy planning, gynecologic symptoms and possible surgical treatment for dehiscence [15, 16].

The purpose of this study was to estimate the efficacy and safety of bidirectional knotless barbed suture for closure of myometrium in cesarean section, comparing with conventional suture.

We retrospectively reviewed the medical records of all the women who underwent CS at Korea University Ansan Hospital between August 2018 and December 2019. This study was approved by institutional review board of Korea University Ansan Hospital, which included a waiver for the obtainment of informed consent (2020AS0047). The study was conducted in accordance with the Declaration of Helsinki. CS was performed by one expert obstetrician who has $>$10 years’ experience in high pregnancy unit. CS procedures were performed as follows. The abdomen was opened by a Pfannenstiel incision, the lower uterine segment was transversely incised with the scalpel followed by blunt expansion with fingers and this incision was repaired with two layers of a continuous suture, either bidirectional knotless barbed suture or conventional suture with polyglactin. For polyglactin suturing, two layers were in a running unlocked manner with knotting on both ends. Decidua was not involved when myometrium was approximated. All patients received prophylactic intravenous cefazolin (2 g) once. Intravenous oxytocin after extraction of placenta was routinely used in our group. Additional uterotonic agents such as prostaglandin and/or methylergonovine were used when postpartum bleeding was diagnosed. Women who underwent vertical cesarean section, hysterectomy and pelvic arterial embolization following a cesarean section and underwent bilateral tubal ligation and women with chorioamnionitis and/or other infection were excluded from the study.

We recorded demographic characteristics of the patients including age, body mass index (BMI), parity, abortion, and smoking status. Obstetric outcomes were assessed; CS indications, multiple pregnancies, pregnancy induced hypertension (preeclampsia (PE), eclampsia, superimposed PE on chronic hypertension (HTN), and gestational HTN), diabetes, preterm birth, conception by assisted reproductive technology, birthweight and gender of baby. Surgical outcomes were determined by uterine closure time, total operation time, estimated blood loss, hemoglobin difference between preoperative result and result on third postoperative day, transfusion, puerperal infection and postpartum bleeding. Total operation time was defined as the time from the skin incision to the end of skin closure. Uterine closure time and total operation time were recorded by fully experienced nurse in the operating room.

The patients were followed up at 6 to 8 weeks postpartum. Expert physicians performed a two dimensional transvaginal ultrasound scan using 4–9 MHz Samsung Medison UGEO H60 (Samsung, Seoul, Korea) or 5–8 MHz GE Voluson E8 (Austria GmbH & Co OG, Austria).

The angle between the longitudinal axis of the uterus and the cervix determines the position of uterus. Retroversion is defined when the uterine long axis is located posteriorly relative to the cervical long axis. Residual myometrial thickness or CS scar thickness is defined in a sagittal section as the shortest length between the endometrium and the uterine serosa at the level of the CS scar (Fig. 1). The percentages of the myometrial thickness at the CS scar depth to the thickness of the adjacent normal myometrium in the sagittal plane represent the degree of thinning [17].

Fig. 1.

Sonographic myometrial thickness evaluation at cesarean section scar. (A) Residual myometrial thickness. (B) Adjacent normal myometrial thickness.

The Shapiro Wilk method was used to assess the normality of the data. Comparisons between two groups were performed using student t-test or Mann-Whitney rank sum tests as appropriate. Categorical values were compared with $\chi {}^2$ or Fisher exact test. All continuous data with normal distribution were reported as either mean and standard deviation and data with non-normal distribution were presented as median. Statistical analysis was performed using SPSS 20 (SPSS, Inc, Chicago, IL, USA). We considered a p value 0.05 to indicate statistical significance.

Knotless barbed suture in CS yielded significantly reduced uterine closure time compared to conventional method. There were no increased rate of perioperative complications including operative time, estimated blood loss, and other complications such as infection and postpartum hemorrhage with knotless barbed suture. It is notable that this is the first study to show no difference in residual myometrial scar thickness postoperatively using knotless barbed suture. The current study highlights that the use of knotless barbed suture is the reasonable alternative to conventional suture. However, longterm complications such as abnormal uterine bleeding and subsequent pregnancy outcome should be evaluated to conclude safety measures of knotless barbed suture in CS.

JYH—Data collection, manuscript writing. HYK, HSB—Project development, manuscript writing. GJC—Data curation, methodology. KHA—Data management, manuscript review. SCH—Data analysis, manuscript review. MJO—Data collection, manuscript review. HJK—Project development, manuscript writing and review.

This study was approved by institutional review board of Korea University Ansan Hospital (2020AS0047). Informed consents were unable to be obtained due to retrospective nature of this study.

We would like to express our gratitude to all those who helped us during the writing of this manuscript. Thanks to all the peer reviewers for their opinions and suggestions.

This research received no external funding.

The authors declare no conflict of interest.