Interpretation
Passing through decidua during suturing was deliberately avoided in all operations performed in the context of this study. A previous study by Roberge et al. (2011) found that the locking closure technique which passes through the decidua produced better results in terms of tissue combination and healing.11 However, niche development was still possible. Additionally, it is not always possible to completely avoid crossing the decidua during such operations. It was thus emphasized that including the decidua in measurements less than 5mm was acceptable, while crossing the decidua with full thickness leads to fusion and may increase niche development.4,13
A previous randomized controlled trial compared three different uterine closure techniques (locked single-layer including the decidua, double-layer with locked first layer including the decidua, and double-layer with unlocked first layer excluding the decidua) in terms of RMT; while no differences were found between the single- and double-layer closure techniques with locked first layers, double-layer closures without locking resulted in thicker RMT when compared to locked single-layer closures.14 These findings supported a hypothesis suggested by Jelsema et al. (1993) in which the locking suture technique was thought to develop ischemic necrosis in tissues due to increased pressure.15 However, many surgeons prefer sutures with locking because they provide good hemostasis. Participants in this study who received double-layer closures also received first-layer locking. For that reason, there were no specific findings about locking effects. While more pronounced niches were observed in participants with double-layer closures, these differences were not statistically significant. This may be caused by the combination of second-layer closures with first-layer locking may have increased tissue stress and disrupted vascularization, the idea that this was caused by differences in technique cannot currently be proven.
On the other hand, the 3-plane niche measurements revealed that participants who received double-layer closures had significantly higher niche widths. However, it is difficult to measure niche width in the transverse plane in retrovert uteri. As no other published study has compared transverse plane measurements in this regard, this finding cannot be thoroughly discussed.
The current literature shows that SIS is a more reliable method of assessing cesarean delivery scar defects than TV USG.16,17 In this study, the rates of niche determination were 21% in TV USG and 41% in SIS. This makes it clear that SIS provides more accurate results. While the PMB rate was 32.1% in cases where isthmocele was detected, the rate was 5.2% among those without. Further, a previous broad-scoped study revealed more noticeable PMB complaints among patients in whom isthmocele was determined at least six months after CD when compared to others.18 The lower than expected PMB rates found in this study may be because some patients (60; 26.7%) had not yet begun to menstruate. As such, more accurate results can be produced by assessing patients for PMB as much as one year after the procedure.
While a previous study that randomly divided patients into three groups (single-layer closure of the uterus without locking, single-layer closure with locking, and double-layer closure) found no significant intergroup differences in terms of niche development and RMT, a trend was found in which thicker RMT was produced via double-layer closures; however, as opposed to the 2mm depths considered in this study, niche presence was accepted at 1mm and deeper, while participants with multiple pregnancies and repeat CDs were included and all niche assessments were conducted via TV USG.9
A previous study by Tekiner et al. (2018) found no significant differences between single- and double-layer uterine closures based on niche assessments at the third postoperative month.19However, their study was limited in that the double-layer group had higher rates of emergency CD, in which there is a tendency for niches to develop at an increased rate.19 As emergency cases were similarly distributed between groups in this study, it may be seen that similar results were produced.
While Di Spiezio Sardo et al. (2017) compared single- and double-layer uterine closures between participants of nine randomized controlled trials and found no intergroup differences in terms of isthmocele, RMT was thinner among single-layer closure patients. However, different uterine closure techniques were used between studies, which also implemented different niche definitions and measurement methods. For that reason, overall results were of the low-moderate evidentiary level. This study also found no significant intergroup differences in terms of RMT.10
A multi-centric study with a protocol that was published in 2019 divided a total of 2,290 patients into single- and double-layer closure groups. Symptoms were then assessed at the third month via TV USG/SIS, while surveys were conducted to provide long-term data. Here, single-layer closures were made without locking and without regards to crossing the decidua, while double-layer closures were made by passing through the endometrium, without locking in the first layer, and continuously without locking in the second layer. Preliminary results show that niche presence was significantly lower among participants with single-layer closures (79.4% vs 83%), but no differences were found in terms of PMB.20 Although the differences were not statistically significant, this study found similar niche rates among the single-layer closure group (37.7% vs %45.7%; p=0.22). However, this issue must be clarified through future prospective studies that include greater numbers of participants.