What is the difference between Shirodkar (cervical cerclage procedure) and modified Shirodkar (cervical cerclage procedure) in preventing preterm birth?

Shirodkar vs Modified Shirodkar Cerclage: Technical and Clinical Differences

Direct Answer

The modified Shirodkar cerclage is a simplified technical variation of the classic Shirodkar technique that maintains high cervical placement while being easier to perform, though current evidence shows no significant clinical superiority of either technique in preventing preterm birth.

Technical Distinctions

Classic Shirodkar Cerclage

• Involves dissection of the bladder anteriorly and rectum posteriorly to place the suture at the cervico-isthmic junction 1
• The suture is placed higher on the cervix (closer to the internal os) with the knot typically buried beneath the vaginal mucosa 1
• Requires more extensive surgical dissection and technical skill 2
• Generally requires cesarean delivery for removal, though vaginal delivery is possible in some cases 3

Modified Shirodkar Cerclage

• Simplified technique that maintains high cervical placement without extensive bladder and rectal dissection 2
• Aims to achieve "cervical high" suture placement while remaining technically easier than the classic Shirodkar 2
• The modification reduces surgical complexity while attempting to preserve the theoretical advantages of higher suture placement 2

Clinical Outcomes: Shirodkar vs McDonald (Context for Understanding Modified Technique)

Efficacy Data

• The Shirodkar technique demonstrates statistically significant reduction in preterm birth before 37 weeks compared to McDonald (RR 0.91,95% CI 0.85-0.98) 4
• Shirodkar shows significant reductions in preterm birth rates at 35,34, and 32 weeks, along with reduced PPROM rates and increased birthweight 4
• However, this significance disappears when studies with serious risk of bias are removed from analysis 4
• No difference exists between techniques for preterm birth <28 weeks, neonatal mortality, chorioamnionitis, cervical laceration, or cesarean section rates 4

Modified Shirodkar Specific Outcomes

• In a comparative study, simplified Shirodkar showed no advantage over McDonald technique (7.1% vs 25.0% delivery before 35 weeks, p=0.17) 2
• For rescue cerclage with prolapsed membranes, modified Shirodkar showed longer cerclage-to-birth interval (83.8 vs 63.7 days) and later gestational age at delivery (33 vs 31 weeks), but differences were not statistically significant 5
• Live birth rates were similar between modified Shirodkar and McDonald in rescue situations (85% vs 63%, p=0.09) 5

Clinical Indications for Shirodkar Techniques

When to Consider Classic or Modified Shirodkar

• Prior cerclage failure with McDonald technique (63.6% of Shirodkar cases had history of failed emergency or prophylactic cerclage) 3
• Very short cervix where correct stitch placement with McDonald is technically difficult 3
• History of multiple mid-trimester losses (74.5% of Shirodkar patients had this history) 3
• Cervical anatomic abnormalities including history of conization (9% of cases) or uterine malformation (7.3% of cases) 3

Success Rates

• Shirodkar cerclage achieves >90% success rate in preventing delivery before 24 weeks, even in high-risk populations 3
• Median gestational age at delivery is 38 weeks with 70.3% vaginal delivery rate 3
• Overall neonatal survival reaches 90.6% with Shirodkar technique 3

Important Caveats

Evidence Quality Limitations

• The overall quality of comparative studies is low, with 16 of 17 studies being retrospective cohorts and only one randomized controlled trial 4
• The simplified Shirodkar technique specifically lacks robust prospective data demonstrating superiority 2
• Most evidence comes from single-center retrospective studies with small sample sizes 3, 2, 5

Practical Considerations

• The theoretical advantage of higher suture placement with Shirodkar techniques has not been definitively proven in well-designed trials 2
• Surgical complexity must be weighed against potential benefits, particularly when modified techniques show similar outcomes to simpler McDonald cerclage 2, 5
• The choice between techniques should consider surgeon experience and technical factors specific to each patient's cervical anatomy 1

Management After Cerclage Placement

• If PPROM occurs after cerclage placement, either removal or retention is reasonable through shared decision-making, as retention shows no significant pregnancy prolongation (45.8% vs 56.2% had 1-week prolongation, p=0.58) 6, 7