Overlapping sphincteroplasty is the procedure of choice for fecal incontinence caused by a disrupted anal sphincter. Most authorities believe that an overlapping technique is superior to an end-to-end repair, although there are few direct comparisons in the literature. The rationale for the overlapping technique is that a more secure repair can be accomplished by placing sutures through the scarred connective tissue rather than the sphincter muscle. Sutures should be less likely to tear through or pull out of connective tissue than muscle. Therefore, the key component of the overlapping technique is preservation of the scarred ends of the ruptured EAS for suture placement.
The initial step involves wide mobilization of the ruptured EAS without excision of the scarred ends of the sphincter. This is accomplished through an inverted semilunar perineal incision or a transverse incision near the posterior vaginal fourchette with inferiolateral extension. The latter incision facilitates repair in patients with damage to the rectovaginal septum attachment to the perineal body. Patients with EAS defects have either a band of intervening fibrous scar tissue between the viable muscular ends of sphincter or a complete separation with scar tissue present only on the ruptured ends of the sphincter. In the presence of complete separation of scar tissue, perineal body reconstruction usually is indicated at the time of repair to restore normal anatomy. A Pena muscle stimulator aids in identification of the distal ends of the EAS and differentiates viable muscle tissue from scar tissue. The stimulator can be used to outline the sphincter before incision as well as during the dissection. It is important to apprise the anesthesiologist of the stimulator usage so that paralytic agents are avoided.
Excessive lateral dissection of the EAS past the 3 and 9 o’clock positions should be avoided as this is where the inferior rectal branches of the pudendal nerve innervate the EAS. Moderate bleeding often is encountered during this dissection, and the use of needlepoint electrocautery can maximize hemostasis. Controversy exists regarding the need to separate the EAS and IAS before repair. Identification of the intersphincteric groove facilitates dissection of the EAS. Dissection in this plane is relatively simple and avoids damage to either sphincter. Defects in the IAS can be more difficult to visualize because this muscle is intimately associated with the rectal mucosa. Examination with a finger in the anal canal is often helpful.
The reconstruction begins with repair of an existing IAS defect using a 3-0 delayed absorbable monofilament suture. Next, the EAS defect is repaired with the primary goal of overlapping at least 2 to 3 cm to ensure adequate bulk of sphincter muscle encircling the anal canal. The EAS is overlapped using three to four mattress sutures of 2-0 delayed absorbable monofilament suture through the distal scar tissue. Once the sutures are tied, there should be resistance palpable with placement of a finger in the anal canal. Copious irrigation is performed throughout the procedure. Following sphincter repair, a perineal body reconstruction and rectocele repair should be undertaken, if indicated, to maximize the normal continence mechanism. Finally, the perineal skin is closed with interrupted absorbable monofilament sutures. Closure frequently requires modification of the initial incision because of changes in the perineal architecture that result from the repair. The most common approach is an inverted Y-shaped closure of the incision (Fig. 28.4).
Figure 28.4 Overlapping sphincteroplasty procedure. A: Inverted semilunar perineal incision with the distal ends of the external sphincter outlined using the Penamuscle stimulator.
B: The external sphincter has been dissected, the scar divided in the midline, and the internal sphincter repaired. C: The external sphincter is overlapped using three mattress sutures of 2–0 delayed absorbable monofilament suture through the distal scar tissue. D: The sutures are tied.