Hydraulically controlled artificial urinary sphincters (AUSs) have been used in the treatment of stress incontinence for nearly 30 years. The Brantley-Scott AUS was first introduced in 1973 [1] and has evolved into the current AS-800 (American Medical Systems Inc, USA), which until recently was the only commercially available device of this kind. Many studies have reported a good, long-term clinical outcome of the AS-800 in various patient groups [2], [3], [4]. However, relatively high surgical revision rates up to 30% [5], [6], [7] have been reported. Revisions are the result of major complications including urethral erosion or atrophy (which may be attributed to high occlusion pressures), mechanical failures such as leaking connectors and infection leading invariably to removal of the whole or part of an implant.
To address these problems, we designed, patented [8] and developed a new AUS. The new device incorporates many characteristics in common with the AS-800 device; however, it also includes a number of innovative features, which aim to overcome some of the disadvantages of the AS-800. The principal design features of the new implant include the following:
•A self-sealing port in the pump assembly for in-situ pressure adjustment
•A stress relief mechanism providing low resting occlusion pressure and conditional occlusion of the urethra
•One-piece assembly to facilitate implantation and minimise mechanical failures
•Improved cuff design to reduce potential for creasing and fracture
•Patient-activated rapid cuff re-inflation facility
The components of the new AUS are a stress relief balloon, a pressure-regulating balloon, a urethral occlusion cuff and a pump assembly unit (Fig. 1A and B). The stress relief balloon is placed extraperitoneally and transmits transient intra-abdominal pressure changes to the urethral cuff to increase occlusion pressure during periods of stress (conditional occlusion). The pressure-regulating balloon is identical to the stress relief balloon but determines the operating pressure of the device. The regulating pressure is adjustable in the range 0–80cmH2O and can be altered by the injection or removal of fluid (on the basis of continence status) from the device in situ through the self-sealing port in the base of the pump assembly unit. A premoulded, adjustable circular urethral occlusion cuff minimises creasing and potential stress fractures, to reduce the possibility of leaking. The new device is manufactured as a single unit from medical-grade silicone rubber, sterilised with the use of gamma irradiation and supplied prefilled with sterile saline and ready for implantation.
  
This paper describes the results of the 12-month preliminary clinical investigation (PCI) of the AUS, implanted at one centre (University College London Hospitals) in a group of male patients with urodynamically proven stress incontinence secondary to prostatectomy and pelvic trauma.
2. Patients and methods
The new AUS has undergone extensive laboratory testing; a protocol for testing in patients was developed and approved by the UK Medicines and Healthcare products Regulatory Authority (MHRA) and local ethics committee for a PCI. The results of the PCI and the technical data formed the submission for CE approval, which has now been granted.
2.1. Patient selection
The investigation was designed as a single-centre study, open to patients over the age of 18 years with urodynamically proven stress incontinence. The main exclusion criteria for the investigation were detrusor overactivity, previous radiation of the pelvis, previous implantation with an AUS, urinary tract infection and postresidual urine volume in excess of 50ml. After obtaining informed consent, we recruited 11 male patients into the study, nine of whom (mean age, 66 years; range, 47–78) were found suitable to be implanted with the device and followed for a period of 12 months. Eight patients were incontinent after removal of the prostate and one after pelvic trauma. All patients had tried conservative treatment methods unsuccessfully, and three patients had undergone unsuccessful urethral-bulking procedures. All patients were relying on containment methods to manage their incontinence.
2.2. Assessment
All patients were assessed before implantation and at 3, 6 and 12 months post-implantation. This included, urinalysis, a cystometrogram, flow rate, urethral pressure profiles, and completion of a 7-day voiding and leakage diary before each visit.
2.2.1. Urinalysis and culture
A midstream urine sample was tested with the use of Multistix 8SG urine analysis dipsticks (Bayer plc, UK) and sent for culture if positive for leucocytes and nitrates, and treated accordingly.
2.2.2. Cystometry and flow rate
Standard urodynamic equipment (Lectromed 3000, Lectromed, UK) was used to perform bladder filling and voiding cystometry. The bladder was filled via a urethral catheter by using sterile saline at room temperature at a fill rate of 60ml/min. Detrusor pressure was measured by subtraction and detrusor activity monitored for signs of over-activity. At full bladder capacity (Vmax), filling was stopped, and patients were requested to initiate voiding; maximum flow rate (Qmax), volume voided ( ) and residual volume were calculated.
2.2.3. Voiding diary
Patients were required to complete a 7-day voiding and leakage diary before each visit. The diary included information on daily fluid intake ( ), volume voided ( ) and volume leaked ( ) either into pads or condom and leg bag. Patients were extensively educated on how to calculate leakage volume. Also, the total number of daily pads used was recorded when applicable. The diaries were analysed and a Continence Index calculated with the following formula and expressed as a percentage:
2.2.4. Urethral pressure profiles
Urethral pressure profilometry (UPP), with cuff inflated and deflated, was carried out at 3 months by using the Brown-Wickham technique.
2.3. Implantation
The new AUS was implanted as a one-piece, sterile device, prefilled to atmospheric pressure with sterile saline. Implantation was carried out under general anaesthesia in the lithotomy position with two incisions: one lower abdominal and one perineal. An indwelling catheter was placed in the urethra for guidance. The urethra was exposed through the perineal incision. A purpose-made disposable trocar was passed subcutaneously from the abdominal to the perineal incision and the cuff passed to the exposed urethral site. The adjustable cuff was positioned comfortably around the bulbar urethra so that it could be gently rotated and secured by a tape, glued with medical grade silicone adhesive and sutured in place for security. The stress relief balloon and regulating balloon were placed through the abdominal incision to sit extraperitoneally at the level of the bladder. The pump unit was then located in the scrotum.
At implantation, the device was left at atmospheric pressure until therapeutic pressurisation after recovery from surgery.
2.4. Device pressurisation
After the resolution of scrotal swelling and inflammation (approximately 2–4 weeks), patients were recalled to pressurise the AUS. The pressurisation procedure was carried out via the self-sealing port in the base of the pump under strict aseptic conditions. The concave base of the pump was palpated to locate the self-sealing port, which was interrogated percutaneously with a 23-G short needle. To increase the device pressure, we injected a known volume of sterile saline through the port to raise the pressure to a predetermined level. If necessary, additional fluid was added to optimise continence at a later date.
2.5. Data analysis
Statistical comparisons were made with a paired, two-tailed Student t test with a significance level of p<0.05 at the 95% confidence limit.
3. Results
3.1. Implantation
Nine male patients were implanted with the device, and implantation and recovery were uneventful. The procedure was simplified because of the one-piece nature of the device and took 30–40 minutes. Mean inpatient hospital stay was 4 days; all patients were discharged on demonstrating the ability to empty the bladder by either spontaneous voiding or intermittent catheterisation.
3.2. Device pressurisation
Device pressurisation was carried out 2–4 weeks after implantation. In three patients, it was decided that pressurisation was unnecessary, as sufficient fluid had been replaced at implantation to provide satisfactory continence (005, 007, 010). Two patients underwent a single-device pressurisation (004, 009), and three patients underwent additional device pressurisations to further improve continence (003, 006, 011). Patients were instructed on how to operate the pump to deflate the cuff and enable voiding.
3.3. Cystometry and flow rates
The implantation of the new AUS had no statistically significant effect on bladder capacity or flow rate. The mean (SD) pre-operative bladder capacity was 504.8 (143.6) ml; at 12 months, it was 545.8 (47.5). The mean pre-operative flow rate was 15.1 (7.4) ml/s; at 12 months, it was 22.2 (4.8) ml/s. None of the patients demonstrated bladder overactivity or any other adverse effect after AUS implantation.
3.4. Continence – voiding diaries
Eight of nine patients provided a satisfactory set of voiding diaries that could be analysed for each visit (patient 010 did not provide a complete set). The average volume intake ( ), volume voided ( ) and volume leaked ( ) over the seven-diary period were calculated for each patient (Table 1; Fig.2) and a Continence Index derived. At each follow-up visit, all patients showed a statistically significant decrease in leakage volume after implantation of the new AUS. At 12 months post-implantation, there was an 85% reduction in the mean leakage volume from 770.6 (±659.7) ml to 51.7 (±36.4) ml.
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Individual patient average daily leakage volumes (in ml) and Continence Index (%) calculated from 7-day voiding diaries
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Patient no.
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Reason
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Average daily leakage volume (ml)
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Pre-operative
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Pressurisation
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3-month
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6-month
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12-month
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Mean (SD)
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p value
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Mean (SD)
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p value
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Mean (SD)
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p value
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Mean (SD)
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p value
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Mean (SD)
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p value
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002
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TURP
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605 (202)
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333 (278)
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Patient removed from study
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003
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OP
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334 (159)
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151 (32)
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*
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100 (30)
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110 (65)
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**
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85 (7)
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**
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004
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TURP
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697 (149)
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224 (46)
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Patient removed from study
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005
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OP
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2228 (1068)
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0 (0)
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0 (0)
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***
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0 (0)
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***
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0 (0)
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***
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006
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OP
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678 (131)
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188 (31)
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***
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151 (19)
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***
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95 (26)
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***
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71 (42)
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***
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007
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OP
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1101 (546)
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–
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15 (5)
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***
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27 (11)
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***
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17 (6)
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***
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009
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OP
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85 (30)
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–
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40 (9)
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**
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38 (27)
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**
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47 (46)
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*
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010
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Trauma
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–
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–
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–
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–
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–
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011
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OP
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437 (136)
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137 (45)
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***
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228 (5)
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**
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261 (74)
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**
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87 (22)
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***
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Mean (SD)
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770 (659)
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207 (78)
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*
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89 (88)
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*
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88 (94)
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*
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51 (36)
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*
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Patient no.
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Reason
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Average Continence Index (%)
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Pre-operative
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Pressurisation
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3-month
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6-month
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12-month
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Pads
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Mean
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Pads
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Mean
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p value
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Pads
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Mean
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p value
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Pads
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Mean
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p value
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Pads
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Mean
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p value
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002
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TURP
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4
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63.3
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2
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72.8
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Patient removed from study
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003
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OP
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–
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86.1
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–
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94.4
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**
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–
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96.6
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**
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–
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95.6
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**
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–
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97.4
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**
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004
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TURP
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4
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46.2
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3
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85.4
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***
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Patient removed from study
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005
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OP
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–
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7.2
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–
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99.8
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***
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–
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100.0
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***
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–
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99.9
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