In 1972, an artificial urinary sphincter (AUS) was developed for severe cases of stress urinary incontinence (1). Since 1983, the AMS800TM, manufactured by the American Medical System (Minnesota, US), has been used for AUS implantation (2). In Japan, the AUS has been available since 2012. However, in some cases, the AUS is removed due to infection, and replacement surgery is required. In 2015, the Mayo Clinic (Minnesota, US) reported large-scale long-term use results in 1082 men who underwent AUS implantation between 1983 and 2011 (3). The median age of the patients was 71 years, the median follow-up period was 49 months, and the device non-replacement rates were 90% at 1 year, 74% at 5 years, 57% at 10 years, and 41% at 15 years. However, only few studies on the postoperative course of patients who underwent AUS implantation have been conducted. Therefore, in this study, we investigated the changes in the number of pads used over time and the results of long-term device use in patients who underwent AUS implantation at our hospital.

We included patients who underwent AUS implantation for stress urinary incontinence, between January 1, 2012 and December 31, 2022. We extracted the following items from the patients’ medical records: age, sex, causes of stress urinary incontinence, comorbidities, date of surgery, date of last follow-up, preoperative video-urodynamics, number of pads before and after surgery, and rate of non-modification of AUS devices. We investigated the risk factors for the modification of the AUS device (removal, reimplantation, replacement, and control pump repositioning). Statistical analysis was performed using the log rank test and Cox proportional hazards model.

In total, 77 cases were included in the study, and the median follow-up period was 24 (5–57 IQR) months. The median age of the patients at the time of initial AUS implantation was 72 years (67.3–76.0 IQR), and the number of preoperative pads was 6.3 ± 3.0. The median operation time was 124 (105–141 IQR) min, and the size of the urethral cuff used was 4.0 cm in 27 cases, 4.5 cm in 40 cases, 5.0 cm in 5 cases, and 5.5 cm in 2 cases. The causes of stress urinary incontinence were open radical prostatectomy in 44 patients (57.1%), robot-assisted radical prostatectomy in 29 patients (37.6%), transurethral resection of the prostate in one patient, radiotherapy for prostate cancer in one patient, spina bifida in one patient, and spinal cord injury in one patient. The mean number of pads/day after surgery was 0.5 ± 0.6 at 1 year, 0.7 ± 1.0 at 2 years, 0.9 ± 1.2 at 3 years, 0.9 ± 1.4 at 4 years, 0.8 ± 1.6 at 5 years, 0.3 ± 0.5 at 6 years, 0.4 ± 0.5 at 7 years, 0.4 ± 0.5 at 8 years, and 0.3 ± 0.6 at 9 years (Figure 1A). The continence rates, defined as maintaining continence with one pad per day or less, were 94.4% at 1 year, 85.7% at 2 years, 76.3% at 3 years, 80.1% at 4 years, 85.7% at 5 years, and 100% at 6–10 years (Figure 1B). The modification-free rates of the AUS equipment were 88.0% at 1 year, 84.3% at 2 years, 76.8% at 3 years, 71.1% at 4 years, 58.2% at 5 years, 58.2% at 6 years, and 45.3% at 7–10 years (Figure 1C). After AUS implantation, the device was removed in seven cases (9.1%), reimplanted in one case (5.2%), and replaced in 11 cases (14.3%). The position of the control pump was adjusted in three cases (3.9 %). The causes of AUS removal were infection in four patients, urethral injury in two, and self-movement malfunction in one. There were six cases of urethral injury, three of which were found at the time of initial implantation, and three of these were found postoperatively. In the 11 patients who underwent AUS replacement, the median number of days from initial implantation to replacement was 1127 (1001–1603.5 IQR). The urethral size at the time of initial implantation and at the time of replacement was 4 cm (4–4 IQR) and 3.5 cm (3.5–3.5 IQR), respectively, and it was smaller at the time of replacement in all cases. In addition, the analysis of the factors affecting AUS replacement surgery revealed significant differences in both univariate and multivariate factors of urethral stricture and detrusor overactivity (Figure 2).

Urinary continence was maintained after the AUS pump was activated; however, the rate of urinary continence decreased approximately 3 years after the operation. This coincides with the timing of the AUS replacement surgery. In cases where the AUS was replaced, the urethral diameter was smaller at the time of replacement than at the time of initial implantation, possibly because of size mismatch with the cuff due to urethral atrophy. Based on the results of multivariate analysis, it is necessary to consider that patients with urethral stricture and detrusor overactivity may be at an increased risk for future replacement surgery. Urethral stricture was defined as inability to insert a 14 Fr. urethral catheter at the time of AUS implantation surgery or a transurethral incision prior to this surgery. Most of the urethral strictures in this study were vesicourethral anastomotic strictures after radical prostatectomy. This suggests that vesicourethral anastomotic stricture may lead to urethral atrophy. Urethral injury was observed in six cases, five of which occurred in up to the fourth case of each surgeon. Thus, surgeons should proceed with caution in the first four cases of AUS implantation.

We summarized the details of AUS implantation at our hospital. Although urinary continence was maintained to some extent, some patients required device revision. The urethral diameter was reduced in cases requiring AUS replacement. AUS replacement should be considered in patients with preoperative urethral stricture or detrusor overactivity.

J Urol. 167: 1125-1129, 1974
Eur Urol. 63: 681-689, 2013
Urology. 86: 602-607, 2015

Continence 7S1 (2023) 100978
DOI: 10.1016/j.cont.2023.100978