Advanced POP involves all three compartments of the vaginal wall. In order to achieve optimal anatomical correction, establishing apex support is essential. However, in cases of apical suspension to the sacrospinous ligament (SSLF), there is a large incidence of anterior compartment recurrence. Therefore, preventive reconstruction and support of the anterior compartment are necessary.
     Calistar-S is a single-incision mesh kit that is similar in concept to the SSLF. It has two anterior attachment arms and two posterior ones, aimed at the internal obturator muscle and the sacrospinous ligament (SSL), respectively. The mesh is attached via the tissue anchoring system (TAS). So far, there is limited data regarding the efficacy and safety profile of this kit.
     In 2019, the Food and Drug Administration (FDA) banned US sales of pelvic mesh owing to concerns about a lack of long-term follow-up data on their effectiveness and safety outcomes. Nevertheless, in some other part of world, including Taiwan, the use of vaginal mesh is acceptable for selected patients.
The aims of this study were to evaluate the objective and subjective outcomes of POP treatment using the Calistar-S system. The secondary objectives were to evaluate quality of life (QOL) and lower urinary tract symptoms (LUTS) outcomes, in particular de-novo or persistent USI, as well as surgical complications.

This is a descriptive retrospective study, performed in a tertiary referral center, which was approved by the Institutional Board Review. The patients with symptomatic advanced POP (POP-Q stage ≥ III who underwent Calistar-S system between June 2018 and August 2022 were reviewed. Patients with previous radical pelvic surgeries or prior mesh installment for prolapse, or those who were medically unfit for surgery, were excluded. Patients with medical comorbidities were addressed preoperatively by anesthetists and physicians, including a requirement of glycated hemoglobin of 6.9% and below for the preceding 3 months.
 
Pre-operative evaluation:
     All the participants had preoperative clinical assessments according to institutional protocol. It included a detailed medical history, a physical and pelvic exam, a cough stress test, a 1-hour pad test, a 3-day voiding diary, and multichannel urodynamic testing. For quality-of-life evaluation, validated UDI-6, IIQ-7, POPDI-6, and PISQ-12 questionnaires were completed at baseline and at 6 and 12 months post-operatively. All the conditions were defined according to the standards of the IUGA/ICS. SUI was based on the clinical symptoms, which were confirmed by a cough stress test and a multichannel urodynamic evaluation with the prolapse reduced. USI was defined as involuntary leakage of urine during increased intraabdominal pressure in the absence of detrusor contraction on filling cystometry. Occult SUI was considered for patients with urine leakage that appeared after the prolapse was reduced during urodynamic evaluation without symptomatic SUI.
     All patients had thorough counseling regarding treatment options, uterine preservation versus concomitant hysterectomy, and potential benefits versus risks. Patients who demonstrated USI during their preoperative workup were consulted and underwent concomitant mid-urethral sling (MUS) after signing informed consent.

Operative Procedure
     All surgical procedures were performed in the following orders: vaginal hysterectomy (if indicated), administration of the Calistar-S system, posterior colporrhaphy, and trans-obturator MUS (if needed). The Calistar-S procedure followed the manufacturer recommendations with modification was made to minimize the risk of developing cystocele: 1-0 Vicryl stitches were applied on the Distal tip of the mesh through the bladder/vaginal mucosa under the bladder neck. 
Cystoscopy was routinely performed after the procedure. As a prophylactic, 500 mg of Cefazolin was given intravenously during the 60 minutes prior to the initial cut and then continued every 6 hours for 24 hours post-operatively. Foley's catheter was in place for 24 hours. 
     Patients were discharged once they were able to void comfortably, and the sonographically post-void residual urine (PVRU) volume was consistently below 150 ml. The patients were also taught to use clean, intermittent self-catheterization if their PVRU volume was persistently above 150 ml for more than 5 days.
Patients were scheduled for outpatient follow-up visits at 1 week, 1, 3, 6, 12 months, and annually post-operatively. 

Outcomes
     The primary outcome was the objective cure rate, defined as anatomical correction of anterior, posterior, and apical prolapse of POP-Q ≤ Stage 1. Subjective primary outcome was defined as the patient’s feedback to questions 2 and 3 of POPDI-6. Secondary outcomes as assessed by validated questionnaires at 12 months and annually postoperatively. Also evaluated were the presence of lower urinary tract symptoms (LUTS), in particular the presence of de novo and persistent SUI, and surgical complications.

108 patients had surgery, 7 patients were excluded because of incomplete data, and 101 patients were included. Baseline demographic characteristics are shown in Table 1. Intra-operative details are also displayed in Table 1. 
     One case of intra-operative bladder injury was encoutered and it was repaired immediately. Folly catheter was left for 3 days. The follow-up revealed a satisfying recovery.
     The mean follow-up duration was 18.7 ± 5.0 months. One patient presented with asymptomatic mesh exposure at 2 months post-operatively. The exposed mesh was trimmed without complications, and follow-up was uneventful.
     The objective cure rate after 1 year showed complete anatomical correction for the apical and anterior compartments (100%) and 96% successful repair at the posterior compartment. Major improvement was seen in all anatomical points, according to the POP-Q score. The subjective cure rate was high (92.1%) at the end of the follow-up period. All validated QOL questionnaires scores at pre- and 1-year post-surgery showed significant improvement. (Table 2)
     As urodynamic parameters Table 2, there was significant improvement in Qmax and Dmax. Cystometric capacity, MUCP, and FUL were decreased significantly. BOO was resolved in all cases but one. And four patients had their mixed urinary incontinence resolved after the surgery.
     Out of the 42 cases with occult or overt USI who underwent MUS procedure, 38 (90.5%) remained asymptomatic after 1 year. In contrast, three patients with overt pre-operative USI who chose conservative treatment had persistent USI. One patient with an occult pre-operative USI who refused to undergo concurrent MUS had her USI resolved. Ten cases of de-novo SUI were recorded, which corresponds to 18.2% of the total cohort.

To the best of our knowledge, the present study is the first of its kind to focus on the surgical management of patients with symptomatic advanced POP with the modified Calistar-S system using validated questionnaires and urodynamics and has demonstrated good 1-year objective and subjective outcomes. The mesh exposure rate was low (1%). Another beneficial effect of pelvic floor reconstructive surgery is restoring normal anatomy and resolving bladder outlet obstruction (BOO). Cases that chose to undergo MUS procedures, only 4 (9.5%) had persistent USI. Three patients with pre-operative overt USI remained symptomatic after 1 year, supporting the benefit of concurrent MUS surgery. 
     18.2% of the asymptomatic population has de novo SUI developed psot-operatively. Paravesical space dissection during the surgical procedure might result in de novo or persistent SUI.

In conclusion, the Calistar-S system is a safe and efficient method for treating POP. In a 1-year follow-up period, we observed a good anatomical outcome and subjective relief with a modest complication rate. LUTS have also been positively affected by the high success rate. Additional studies are needed to establish the long-term efficacy of this system.