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Locking Stitch (Running-Locked Suture)

The locking stitch is a modification of a continuous (running) suture in which the needle is passed through the loop of the preceding stitch before advancing to the next bite, cinching each loop down so that the suture line becomes a series of individually secured loops rather than a freely sliding thread. In reconstructive and urogynecologic surgery it is the workhorse closure for vascular mucosa where hemostasis matters — most classically the vaginal mucosal layer of a perineal/episiotomy repair and the closure of bleeding vaginal and cervical lacerations.[1][3]

What Locking Does​

  • Fixes tension at each bite. In a plain running suture, tension is shared along the whole thread — if one segment loosens, the entire line can slacken. Locking anchors each loop independently, so tension (and approximation) is held at every individual stitch.[1]
  • Improves hemostasis. The locked loop compresses tissue more firmly at each point, which is why it suits oozing vascular mucosa (vagina, cervix).[2][3]
  • Resists shortening/bunching of tubular structures. A free running suture can cinch and shorten a tubular closure; the traditional rationale for locking the vaginal mucosal layer is specifically to prevent shortening of the vagina.[1]

When to Lock​

  • Vaginal mucosa during perineal/episiotomy or laceration repair — the classic indication (prevents vaginal shortening; controls mucosal ooze). Note the modern caveat below.[1][3]
  • Bleeding vaginal and cervical lacerations — ACOG recommends a running-locking suture; for cervical lacerations, locking sutures run from above the apex outward through the full thickness of the cervix.[3]
  • Any mucosal closure where hemostasis is the priority — locking "can be used if needed for hemostasis," but is not mandatory for every mucosal closure.[2]

When Not to Lock​

  • Perineal muscle and skin layers — locked stitches are easy to over-tighten, restricting the distribution of post-op tissue edema and increasing pain.[1]
  • When edema is anticipated — a non-locking continuous suture lets tension redistribute as tissues swell, reducing strangulation of the wound edges.[1][4]

The Evidence Trend: Lock Selectively, Not by Default​

Although locking the vaginal mucosa is the traditional teaching, current evidence favors a continuous non-locking technique for the overall repair. A Cochrane review and ACOG find continuous non-locking closure of all layers (vagina, muscle, skin) associated with less postpartum pain and less analgesic use than the locking/interrupted approach.[1][3][4] The practical synthesis: lock for hemostasis, not by habit.

LockDon't lock
TissueVascular mucosa (vagina, cervix)Muscle, skin; anything that will swell
GoalHemostasis; prevent tubular shorteningPain minimization; let edema redistribute
Typical useBleeding vaginal/cervical laceration; vaginal-mucosa layer when oozingPerineal muscle and skin layers; overall perineal repair

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.

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

4. Kettle C, Dowswell T, Ismail KM. Absorbable suture materials for primary repair of episiotomy and second degree tears. Cochrane Database Syst Rev. 2010;(6):CD000006. doi:10.1002/14651858.CD000006.pub2