Discussion
In our previous study, we published a nomogram for the preoperative
prediction of surgical treatment efficacy for CSD. We referred to
Glavind’s studies that defined the class A healing group as having a TRM
no less than 5.8 mm after vaginal repair13. Only 167
patients were included in the training cohort. Due to the limited number
of cases, previous research only identified risk factors for failure to
achieve class A healing17. Our study has improved the
shortcomings and built the prediction model system.
Our research shows the timing of C-sections, the menstrual cycle, and
the length, width, depth, and thickness of the lower uterine segment of
the CSD can predict whether CSD repair surgery can achieve optimal
healing. The results are similar to Liu’s research, which shows that the
number of C-sections, a trial of labor (elective or urgent C-sections),
C-section interval, and uterine position were independent risk factors
for CSD18. Interestingly, we find that elective
C-section surgery is a risk factor for CSD, but they respond better to
repair surgery when CSD occurs. We think that the reason for this may be
the trial process of myometrial stretching and contraction is a
protective factor for wound healing; however, there may be potential
biological mechanisms that lead to suboptimal healing in patients who
develop CSD after the trial process such that conditions are not
conducive to healing of the incision when the CSD is repaired.
We also find that when the menstrual cycle is greater than 26 days,
optimal healing is more easily achieved after surgery. This means that
patients with long menstrual cycles (>26 days) have better
surgical outcomes, which is consistent with our previous finding that
oral contraceptives or GnRHa can improve menstrual conditions. We think
GnRHa can prolong the menstrual cycle or reduce the menstrual volume to
a certain extent, so patients with a long menstrual cycle can heal
relatively well after surgery. It is possible that chronic inflammation
caused by menstrual stimulation can hurt wound healing. Additionally,
our results show that a CSD width of greater than 13.8 mm will influence
surgical efficacy, particularly the improvement of postoperative
menstruation. Previous case studies found that CSD repair with a CSD
width ≥18.85 mm had a poor prognosis15, which was
consistent with the index in our prediction model.
On the other hand, we find that not all patients sought to achieve
optimal healing by treatment. Some patients may only expect to improve
menstrual conditions, while others will expect to increase the TRM to
reduce the risk of pregnancy but do not care much about PAUB. Therefore,
we also discuss the factors that can improve menstruation or increase
TRM merely. The results show that the posterior uterus or TRM ≥2.79 mm
is the independent correlation factor for TRM improvement. However, CSD
width ≤13.27 mm or the thickness of the lower uterine segment ≤22.67 mm
preoperatively can predict PAUB symptom improvement.
Many studies have confirmed that the presence of a CSD might increase
the risk of subsequent cesarean scar pregnancy. One study showed that
repair surgery both reduced the incidence of cesarean scar pregnancy and
increased the number of live deliveries19. This
finding reflects complete correction of the CSD by suturing, which
strengthens the uterine wall and promotes either complete or partial
healing of the uterine scar after surgery. Therefore, for patients with
subsequent pregnancy requirements, the recommendation is to evaluate
whether optimal healing can be achieved or whether TRM can be improved
after surgery by a prediction model.
We hope to use the prediction model to enable more appropriate treatment
options for patients with CSD. We recommend vaginal repair surgery as
the first choice when the score is ≥ 16.5 because this approach is less
damage, lower cost, and a shorter hospital stay. When the score is less
than 16.5 suggests that the patient will have difficulty achieving
optimal healing through vaginal repair. In this case, when the patient
has no desire for a subsequent pregnancy, hysteroscopic resection
surgery can be recommended. Hysteroscopic resection is considered the
least invasive among the possible operations; however, hysteroscopy may
have the potential risk for decreased resistance of the residual
myometrial tissue at the level of the repair and may lead to uterine
rupture during subsequent pregnancy20-22. Therefore,
hysteroscopic surgery is not recommended for patients with pregnancy
intentions. Additionally, the TRM should not be less than 3 mm, given
the anticipated risk of perforation or bladder
injuries23-24. For patients with a score<16.5 without
pregnancy requirements, younger patients can be recommended to use oral
contraceptives or an intrauterine device (IUD). The levonorgestrel
intrauterine system may have a role in the safe and effective management
of PAUB in patients with CSD. The study shows that after 1 year of
treatment, 22 patients (78.6%) reported an improvement in symptoms with
the levonorgestrel intrauterine system. The mean duration of
menstruation is 18 and 5 days before and after treatment,
respectively25. This is a good choice for patients who
just want to improve their menstruation.
If the score is less than 16.5 and the preoperative residual muscle
layer is less than 2.16 mm, but the patient has a strong desire to
become pregnant, she should be fully informed of the possibility of a
poor outcome before surgery. If the patient has a history of multiple
operations and abdominal adhesions are considered preoperatively, pelvic
adhesion decomposition can be performed by a single-port laparoscope
that can be released to restore the normal anatomical structure, and
then vaginal surgery can be performed to avoid excessive anterior or
posterior flexion of the uterus, which may be helpful to improve
postoperative recovery. Adding oral contraceptives or GnRHa to prolong
menstruation after surgery may also help to improve the prognosis. We
have demonstrated the effectiveness of GnRHa in another study, and the
article has been submitted (data unpublished, under review).
Our study is the first prediction model performed in China to assess the
surgical efficacy of CSD. The major strength of our study is determining
which patients with CSD should be repaired or other treatment options
according to the score. Several limitations should be considered when
interpreting the results of this study. First, this is a retrospective
study, which has inherent biases. Second, this study comes from a single
institution, and the nature of the database is a strength. Although
consistency in surgical techniques is ensured, there are limitations in
patient selection. Third, alternative treatment options and their
effectiveness should be further validated. In addition, our study
requires an external validation cohort to make the results more
convincing, and the inclusion of such information is planned in our
future studies.