I just realized that since the outset of this series, we have talked about cervical cerclage but we have not explained what that is for the general reader. A cerclage is a ‘stitch’ placed around the cervix in a fashion that will, hopefully, prevent progressive cervical change and/or ballooning of the membranes through the cervical canal. There are various types of cerclages, but the three with which I have had the most experience can be found in our literature by the names Shirodkar cerclage, McDonald cerclage, and abdominal cerclage.
When I trained, we were almost exclusively taught to perform a Shirodkar cerclage (Antiseptic 1955;52:299). This procedure is done by dissecting the vaginal mucosa and bladder off the cervix anteriorally, and if necessary, opening the cul-de-sac (dissecting the vaginal mucosa off the cervix) posteriorally and then placing the suture as high as possible around the cervix tunneling through the cervical stroma. The cerclage is usually begun at the 12:00 o’clock position and then placed circumferentially with as few exit points as possible until the starting point is reached and the suture is tied. The vaginal mucosa is then reapproximated to cover the cerclage.
The procedure was first described by Shirodkar using absorbable catgut suture, but this was soon replaced with Mersilene tape – the ‘permanent’ material still most often used for this procedure today. The advantage of the Shirodkar cerclage is that one can place the suture almost as high (if not as high) as the internal cervical os. However, the disadvantages are that it is a more challenging procedure (especially with obese, primigravida patients or those with advanced cervical changes), often requiring more time in the operating room, with greater risk for hemorrhage, and perhaps infection, using a material that is sometimes more difficult to pass through the cervical tissue, and certainly more difficult to remove. Indeed, many patients with successful pregnancies and ‘good’ Shirodkars simply have a cesarean section performed for delivery and leave the original suture in place for a subsequent pregnancy. It is not a very practical procedure for ‘emergent’ or ‘rescue’ procedures when the membranes are deep in the cervical canal or ballooning past the external cervical os.
From my perspective, I mention the Shirodkar almost for historical purposes since most of the cerclages I have performed over the past 20-odd years have been McDonald cerclages. This procedure was described by McDonald (J Obstet Gynaecol Br Empire 1957;64:356) a few years after Shirodkar. It does not involve dissection of the vaginal mucosa off the cervix and is simply a ‘purse string’ suture placed around the cervix in 4 to 6 ‘bites’. Again, when I was first taught this procedure, I used Mersilene tape, but soon learned that the disadvantages, for the reasons noted above, made this suture material especially impractical when a ‘rescue’ procedure was necessary – something I was being called upon to perform more often in my consulting role in Maternal-Fetal Medicine. Indeed, despite taking great care, I remember iatrogenically rupturing membranes several times during ‘rescue’ procedures simply as the result of the difficulty of tightening the mersilene tape around the cervix after the cerclage had been placed. As the result of these experiences, I switched to #5 Ethibond and have used this successfully for more than 20 years as will be described in our next post.
The primary advantages of the McDonald procedure are that it can be performed quite rapidly, with minimal risk for blood loss or infection, and can be more easily removed to permit a vaginal delivery. The disadvantages are that it usually cannot be placed as high on the cervix as a Shirodkar, and many clinicians shy away from adequate placement for fear of damaging the bladder or rectum. Indeed, in my experience, the greatest reasons for failure of McDonald cerclages are threefold: they are not placed highly enough, deeply enough, or tied tightly enough to prevent cervical change and downward displacement of the membranes….