Obstetric anal sphincter injuries (OASIs) are the most severe form of perineal trauma, associated with significant maternal morbidity, including perineal pain, sexual dysfunction, anal and urinary incontinence (1). OASIS are divided into two groups: third degree laceration, defined as IIIa if less than 50% of external anal sphincter (EAS) is involved, IIIb if more than 50% is involved, and IIIc if both EAS and internal anal sphincter (IAS) are torn. A fourth degree laceration is defined if the perineum injury involves EAS, IAS and the anal epithelium or rectal mucosa (2). Treatment of OASIS requires a correct diagnosis and immediate surgical reparation, that must be performed by trained surgeons. 
Only two methods are recognized for EAS repairing, end-to-end (approximation) and overlap repair (3). In end-to-end method, the torn ends of the EAS are approximated and sutured (3). In the overlap method, the torn ends of the EAS are brough together and sutured by overlapping one end of the muscle over the other in a double breasted fashion (3).
The available data showed that compared with immediate primary end-to -end repair of obstetric OASIS, immediate primary overlap appears to be associated with a reduced risk of faecal urgency and anal incontinence at 12 months (3).

A 30 year old woman P0 at 41 weeks of pregnancy was admitted to our Teaching Hospital for programmed labour induction due to gestational diabetes in insuline and metformine therapy. 
Induction was performed with endovaginal prostaglandins. 
A 3720 grams male newborn, Apgar score 7 at minute 1 and 9 at minute 5 was delivered in epidural anesthesia. Total blood loss was 100 mL. At afterbirth conclusion, a complete EAS (IIIB) vaginoperineal laceration with complete disruption of the external anal sphincter was found.
After signing informed consent for reparation and operation’s video recording, the patient underwent to surgical reparation.

An accurate pelvic exam with rectal exploration confirmed IIIb OASIS with exclusion of any IAS or anal/rectal mucosa laceration. The reparation began with EAS overlapping transversal suture technique using multiple PDS 3/0 stitches.
Perineal muscle-fascial plan and centrus tendineous were reconstructed using multiple Vicryl 2/0 stitches. Vaginal mucosa, subcutaneous tissue and skin were sutured with running suture Vicryl 2/0 from the apex to the external anal skin. At the end rectal exploration showed no signs of anal laxity. Postpartum course was regular with standard systemic antibiotic and laxative therapy. No fever, hematoma, urinary or anal incontinence episode occurred. The patient was regularly discharged at 72 hours from childbirth. No early or intermediate complication occurred.
Postpartum valuation 40 days after delivery was regular, without anal incontinence.

Given the high morbidity caused by OASIS, an immediate recognition is mandatory. Midwives and gynecologists must be trained to identify and classify those kind of lacerations. 
We present this teaching video made in our Teaching Hospital like a tutorial, with the intent to show and teach to our residents and colleagues a very simple technique for EAS injuries recognition and reparation. We believe that simplification of teaching through representation in video clip can benefit the training of young gynecologists and patient satisfaction.

Roper J. Review of available national guidelines for obstetric anal sphincter injury. Int Urogynecol J. 2020 Nov.
Harvey MA. Obstetrical Anal Sphincter Injuries (OASIS): Prevention, Recognition, and Repair. J Obstet Gynaecol Can. 2015 Dec.
Fernando RJ, Sultan AH. Methods of repair for obstetric anal sphincter injury. Cochrane Database Syst Rev. 2013 Dec