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Locking Stitch (Running-Locked Suture)

The locking stitch is a modification of a continuous (running) suture in which the needle passes through the loop of the preceding stitch before advancing to the next bite, limiting how freely tension redistributes along the line. It is a traditional option for bleeding vaginal mucosa or a bleeding cervical laceration. It is not the default for every perineal or episiotomy repair.[1][3]

What Locking Does​

  • Limits tension redistribution. Compared with a plain running suture, each locked loop maintains more local tension; excessive tension can constrict tissue.[1]
  • Can help hemostasis. Local compression is why a locking stitch may be used for oozing vaginal mucosa or a bleeding cervical laceration, although it is not required for every repair.[2][3]
  • Has a traditional shortening rationale, not proven prevention. The older rationale for locking the vaginal mucosal layer was to prevent vaginal shortening. The Cochrane review states that good-quality evidence for that theory is lacking.[1]

When to Lock​

  • Bleeding vaginal mucosa during laceration repair. A traditional option when local hemostasis is needed; the vaginal-shortening rationale remains unproven.[1][2]
  • Bleeding vaginal and cervical lacerations. When a vulvar or vaginal laceration needs repair, ACOG recommends a running-locking or interrupted suture that incorporates the underlying tissue, with 2-0 chromic or polyglactin by expert opinion. For a cervical laceration, the first stitch is placed above the apex; subsequent interrupted or continuous locking sutures may incorporate the full cervical thickness outward through the raw edges. These technique choices are largely expert opinion, not comparative trial findings.[3]
  • Second-degree obstetric repair with mucosal bleeding. During running closure of the vaginal mucosa and underlying fascia, locking can be used if needed for hemostasis.[2]

When Not to Lock​

  • In second-degree obstetric repair, the perineal muscle is reapproximated with continuous nonlocking sutures. Well-apposed perineal skin may be left unsutured; if skin closure is chosen, avoid overtightened locked loops.[1][2][3]
  • In episiotomy or second-degree perineal repair, a continuous nonlocking suture is intended to distribute tension along the line as tissue swells.[1]

The Evidence Trend: Lock Selectively, Not by Default​

Although locking the vaginal mucosa is traditional, a Cochrane review included 16 trials (8,184 women enrolled); its meta-analysis of nine trials (4,231 women) found a lower risk of pain up to 10 days postpartum with continuous than interrupted perineal closure (all layers or perineal skin only; RR 0.76, 95% CI 0.66 to 0.88).[1] ACOG prefers continuous over interrupted suturing for second-degree lacerations (Level B).[3] Many trials changed the vaginal stitch and the muscle and skin closure together, so these findings do not isolate the effect of locking alone. In practice, locking is used selectively for hemostasis.

LockDon't lock
TissueOozing vaginal or cervical mucosaRoutine perineal muscle and skin closure
GoalLocal hemostasisAvoid excessive local tension and permit redistribution
Typical useSelected bleeding vaginal/cervical lacerationsContinuous non-locking second-degree repair when hemostasis permits

See Also​

References​

1. Kettle C, Dowswell T, Ismail KM. Continuous and interrupted suturing techniques for repair of episiotomy or second-degree tears. Cochrane Database Syst Rev. 2012;11:CD000947. doi:10.1002/14651858.CD000947.pub3

2. Arnold MJ, Sadler K, Leli K. Obstetric lacerations: prevention and repair. Am Fam Physician. 2021;103(12):745–752. PMID 34128615

3. Committee on Practice Bulletins—Obstetrics. ACOG Practice Bulletin No. 198: Prevention and management of obstetric lacerations at vaginal delivery. Obstet Gynecol. 2018;132(3):e87–e102. doi:10.1097/AOG.0000000000002841. Interim update; reaffirmed 2025.