The pressure-regulating balloon is implanted in the subperitoneal prevesical space. It controls the pressure exerted by the occlusive cuff on the anal canal and is available in seven pressure ranges. The most commonly used are in the 91–100 and 101–110 cmH₂O ranges. The appropriate balloon is selected based on tissue thickness and integrity and the tightness of the cuff [3].

The cuff is implanted in the upper part of the anal canal. When inflated, the cuff occludes the anal canal by applying circumferential pressure. American Medical Systems provides 12 cuff sizes for the Acticon prosthesis, with cuff lengths ranging from 9.0 to 14.0 cm, and two cuff widths: narrow (2.0 cm) and standard (2.9 cm). A cuff sizer is used intraoperatively to select the appropriate cuff size for each patient.

The control pump is implanted in the subcutaneous tissues of the scrotum or labia majora. The control pump contains the resistor and valves needed to transfer fluid to and from the cuff. The hard upper part of the pump features a deactivation option so that the cuff can be deflated for a prolonged period of time. The soft lower part of this pump is squeezed repeatedly to transfer fluid within the device. A septum placed at the bottom of the soft part is designed to add fluid to the system without additional surgery. The control pump comes in one size that accommodates all cuff and balloon sizes.

The AAS functions semiautomatically. The cuff ensures anal closure automatically and continuously at pressures close to the physiological values of the anal resting pressure. Defecation is initiated by the patient. Activation of the pump forces fluid from the cuff into the balloon, deflating the cuff and allowing defecation. Subsequently, the cuff automatically reinflates slowly in 5–8 min to maintain continence until the next evacuation [4].

The first phase of the operation involves the placement of the perianal occlusive cuff. The cuff is placed using either one transverse anterior incision across the perineal body or two curvilinear incisions on either side of the anal canal. The single anterior incision is used for female patients with a scarred or thin perineal body. After the perianal tunnels have been created, a cuff sizer is pulled around the anal canal to measure the appropriate length and width of the cuff. The appropriate cuff length is one centimeter longer than the value measured using the sizer. Once the perianal cuff is put into place, the cuff tubing is tunneled subcutaneously to the abdominal incision. The rectus abdominis is split to provide access to the subperitoneal space lateral to the bladder. A pocket is created in this space to lodge the uninflated reservoir balloon. The balloon is then inflated with radiopaque fluid. A metal dilator is advanced into the subcutaneous tunnel from the lower abdominal incision to the scrotum or labia majora to create a place for the control pump, which is then positioned. The occlusive cuff and pressure-regulating balloon are connected to the pump. After verifying that the cycling is correct, the incisions are closed without drainage. The device is deactivated at the end of the procedure.

A transvaginal approach also has been proposed in women with a destroyed or severely scarred anterior perineum [5]. In such cases, a transverse incision is made on the posterior vaginal wall 2 cm above the introitus. The rectal wall and rectovaginal connective tissue are separated from the vaginal wall. The ischiorectal fossa is entered on either side, and a circumferential tunnel is created around the anal canal. Once the tunnel is created, a sizer is passed through the tunnel to choose the appropriate length of cuff. The other implantation steps are essentially the same as those described earlier.

Preoperative, perioperative, and postoperative management of patients is a critical requirement of the AAS treatment, especially to avoid early complications. In our experience, key elements of the technique include the following [5, 6]:

In terms of effectiveness, all studies have reported statistically significant reductions in mean fecal incontinence scores and improvements in quality of life after implantation of a functional AAS [2]. Patients who have successful implant procedures enjoy a 100% functional success rate [6, 8, 9]. Our most recent series studied 32 consecutive patients who received transvaginal implants and were followed up over 41 months; Cleveland Clinic severity continence scores of the 23 patients in whom the AAS remained functional (72%) decreased significantly from 18.4 at baseline to 6.8 at last follow-up [6]. All the patients with functional AAS were continent for solid stools, 82.6% were continent for liquid stools, and 47.8% were continent for gas.

There are, however, a number of methodological deficiencies in published studies [2]. First, results have not been analyzed on an intention-to-treat basis and, as such, misrepresent the effectiveness of the procedure. Second, most are case series. Only one randomized, controlled trial compared a group of 14 patients randomly assigned to an AAS group with a control group in a best supportive care program for fecal incontinence [7]. Although there was no significant change in continence in the control group at 6 months, there was a highly significant improvement in the AAS group, which saw a reduction in the Cleveland Clinic score from 19.1 to 4.8. Similar changes were observed in quality of life. Third, only limited data for long-term follow-up of a sufficient number of AAS sphincters are available. According to Parker et al. [8], once successfully established, AAS sphincters provide long-term improved continence and quality of life. However, long-term outcomes are less encouraging in other studies, with one reporting a median follow-up of approximately 6 years and no improvement in continence scores despite a functional AAS [10].

No mortalities have been reported after AAS implantation or explantation, but AAS implants are associated with a high level of morbidity. Two main problems after implantation have been identified: (1) the explantation rate and (2) constipation with fecal impaction.