Comparison of obstetric anal sphincter injuries in nulliparous women before and after introduction of the EPISCISSORS-60 at two hospitals in the United Kingdom

Introduction

The incidence of obstetric anal sphincter injuries (OASIS) in the UK is 6.1%¹ and has tripled between 2000 and 2012.² More importantly, OASIS are the most common risk factor for anal incontinence in women, which may affect up to 25% of women in the year following delivery.³ It has been shown that 30% of women are symptomatic for anal incontinence and urgency after 1 year.⁴

There are significant costs associated with OASIS. With 40,000 women affected per annum,⁵ the main cost is of course related to quality of life for the women involved. In financial terms, there are major cost implications for both primary and secondary repairs of OASIS. In addition, the National Health Service Litigation Authority (2012) in their report of 10 years of claims cite OASIS being the fourth largest cause for litigation in obstetrics.⁶

Research into the causes for OASIS has identified a number of risk factors. The Royal College of Obstetricians and Gynaecologists has listed the following risk factors for OASIS in its guideline for the management of third and fourth degree tears: Asian ethnicity, nulliparity, birth weight greater than 4 kg, shoulder dystocia, occipito-posterior position, prolonged second stage of labor, and instrumental delivery in which forceps carries a higher risk for OASIS than ventouse.⁷

Another factor not described in the Royal College of Obstetricians and Gynaecologists guideline but identified by a number of studies as a risk factor for OASIS is perineal body length (PBL).^8–10 Measured as the length from the posterior fourchette to the midpoint of the anal canal, Deering et al¹¹ found that patients with a PBL ≤25 mm had a significantly increased risk of having a delivery resulting in OASIS (40% versus 5.6%, P=0.004).

The ultimate aim of identifying risk factors is to reduce the incidence of OASIS. However, most risk factors are either not modifiable or have no alternative. For this reason, researchers have looked into other ways of reducing OASIS and the use of episiotomies has been one of the most prominent among these.

The role of episiotomy for prevention of OASIS is conflicting^12–14 and is currently not routinely recommended for all deliveries. However, Gurol-Urganci et al² looking at the Hospital Episode Statistics data for England over a 12-year period found that episiotomies were protective for OASIS. This effect was particularly present for instrumental deliveries but there was also a statistically significant OASIS reduction in primigravidas who had a normal vaginal delivery with an episiotomy.

A possible explanation for the conflicting evidence surrounding episiotomy may be related to operator technique. The type of episiotomy favored in England is a mediolateral episiotomy versus the midline episiotomy often used in the USA. It has long been known that mediolateral episiotomy has a significantly lower OASIS rate than midline episiotomies, 2% versus 12%–20%.^15,16 Unfortunately, there is a lack of definition of the ideal angle of a mediolateral episiotomy and it is usually determined by the operator’s intent. However, the angle of mediolateral episiotomy turns out to be of crucial importance. It is important to notice here that, due to the way the perineum expands, there is a difference between the angle at which the episiotomy is cut and the post-suturing angle. Evidence has shown that incidence of OASIS is 10% with a post-suturing angle of 25° and reduces by 50% for every 6° the post-suturing angle is away from the midline. With a suture angle of 45°, the overall incidence is reduced to 0.5%.¹⁷ However, if the post-suturing angle is more than 60°, there is no protective effect as the episiotomy will have failed to relieve pressure from the perineum.¹⁸ In its 2007 guideline for intrapartum care, the National Institute for Health and Care Excellence states operators should aim to achieve an episiotomy angle between 45° and 60° at time of cutting. However, a 45° episiotomy angle at time of cutting achieves a post-suturing angle of 22°–24°. To achieve a post-suturing angle of 43°, the episiotomy needs to be cut at 60°.¹⁹ In addition, Stedenfeldt et al¹⁸ found that episiotomies are more effective when the cut is started away from the midline from posterior fourchette to the anal margin. For each 4.5 mm the episiotomy is started away from this line, OASIS reduce by 56%.

Hence, for an episiotomy to be effective, the angle and starting point are of critical importance. In view of this evidence, the recently published Royal College of Obstetricians and Gynaecologists Green Top Guideline 29 unequivocally recommends a 60° angled episiotomy at the time of cutting. The current method used by most clinicians is “eyeballing”. However, Andrews et al²⁰ found that 0% midwives and 22% of doctors cut a truly mediolateral episiotomy between 40° and 60°. The inability to estimate angles accurately has been demonstrated in model situations as well with only 12%–15% clinicians cutting an episiotomy at the recommended angle.^21,22

To avoid human error in estimating the angle required for mediolateral episiotomies, a team led by Professor Robert Freeman developed EPISCISSORS-60™ (Medinvent Ltd, Romsey, UK): episiotomy scissors especially designed to attain a post-suturing angle between 40° and 60° and achieve post-suture episiotomy 4.5 mm away from the midline. This patented product has a guide-limb that points toward the anus in the vertical plane and the scissors maintain a constant angle of 60° and 4.5 mm starting point away from the midline. In an initial trial of 17 women, Freeman et al¹⁹ demonstrated that the scissors consistently achieved a 43° post-suturing angle. Two subsequent studies have confirmed the efficacy of EPISCISSORS-60^® in achieving these post-delivery suture angles.^23,24

As part of a wider strategy to reduce OASIS, EPISCISSORS-60^® were introduced to clinical practice through a structured practical training program. This training program provides all midwives and doctors with a specific set of knowledge and skills to reduce OASIS. It includes teaching of the evidence based theoretical framework, practical teaching of measuring PBL, and training to cut true mediolateral episiotomies on a model using EPISCISSORS-60^®. The decision when to perform an episiotomy lies with the operator. Two hospitals in the UK applied for an innovation fund grant to introduce and evaluate the effect of EPISCISSORS-60^® on the incidence of OASIS through this program. Both hospitals are acute general hospitals with Hinchingbrooke Hospital in Cambridgeshire supporting 2,300 deliveries per annum and Poole hospital in Dorset just under 5,000. In the initial phase of this program, we focused on collecting and analyzing the data with regard to primigravidas as this is the group most at risk.

In this paper, we present our results with regard to PBL, uptake of episiotomy, post-suturing angles, and effect on OASIS based on our initial evaluation after 4 months of usage.

Methods

The Strategy for Using Practical aids for Prevention of OASIS, Recording episiotomies and clinician Training (SUPPORT©) program of all doctors and midwives at two sites commenced in December 2014. In January 2015, training of all medical staff had been completed and training of midwives continued until May 2015. Data were collected between January and May 2015. As part of the training program, whenever an episiotomy was deemed clinically indicated, EPISCISSORS-60^® would be used. All episiotomies performed by trained operators in nulliparous women were included. The indication for episiotomy was left to the operators’ judgment. All deliveries were recorded onto the hospital record system immediately after the delivery. In addition, as part of the data collection, a standardized form was used for all deliveries on which the following would be recorded immediately after delivery: previous obstetric history, mode of delivery, first stage PBL, use of episiotomy, post-suturing episiotomy angle as measured from the midline, hands-on or hands-off delivery, occurrence of OASIS and which grade, type of operator, and feedback on EPISCISSORS-60^® on a scale from 1 to 5 (very poor to very good). EPISCISSORS-60^® were used for all deliveries and data with regard to use of episiotomy and OASIS were collected through the hospitals’ general data collection system and this database was used for the assessment of effect on OASIS. The results were compared with previous results obtained for the year 2014 from the hospitals’ database. This program was registered as a service evaluation and quality improvement process and approved by the audit and R&D department. Hence, no ethics approval was needed.

Results

Data were available for 197 nulliparous vaginal deliveries in Hinchingbrooke Hospital of which 137 were spontaneous vaginal deliveries (SVDs) and 60 operative vaginal deliveries (OVDs) and 641 nulliparous vaginal deliveries in Poole Hospital of which 452 were SVDs and 189 were OVDs (Table 1). Data collection forms were completed for 100 nulliparous vaginal deliveries and these formed the basis for our PBL measurements, post-episiotomy suturing angles, and user feedback.