Despite the growing emergence of mini-invasive surgical treatments for urinary incontinence (i.e., urethral slings, injections of bulking agents, adjustable continence therapies, and stem cell therapies), the AMS 800® artificial urinary sphincter (AUS) (American Medical Systems, Minnetonka, MN, USA) has remained the ‘gold standard’ treatment for stress urinary incontinence in men and women over the last 40 years. Despite the favourable outcome and satisfaction rates after its implantation, this device continues to be associated with the risk of local complications (i.e., atrophy, erosion and infection) or mechanical failure. Thus, regular revisions and/or explantations are mandatory in at least 30% of AUS devices. New and more sophisticated AUS devices have recently been developed to improve function, occlusive efficiency, and biocompatibility relative to its current design.
In a recent article, Chung et al.  provided a review of new and/or innovative AUS devices.
The FlowSecure AUS (FlowSecureTM, RBM-Med) was designed in 1991 with early functional outcomes reported in 2006. It has the main advantage of instantly increasing the pressure delivered to the urethra, only during stress increases in intra-abdominal pressure. When deactivated, the cuff returns to the initial low pressure level, never exceeding 40 cmH2O, thus minimising the risk of urethral atrophy and/or erosion. As indicated by Chung et al. , despite encouraging preliminary results with the FlowSecureTM, more recent data have shown high mechanical failure and infection rates, as well as risk of pump assembly perforation in short- to intermediate-term follow-up.
The Periurethral Constrictor (Silimed, Rio de Janeiro, Brazil) was released in 1996. It is simple to use and of low cost. However, there are only a few published studies with controversial outcomes for the device in a post-prostatectomy urinary incontinence setting . The routine use of this device is debatable.
The Tape Mechanical Occlusive Device (GT Urological LLC, Minneapolis, MN, USA) is a non-hydraulic one-piece device that is manually controlled by the patient through its on/off buttons . It has been implanted in dogs to assess its function, occlusive efficiency, and biocompatibility and in human male cadavers to assess its occlusive efficiency and sizing, with encouraging results. Prospective clinical studies are awaited.
Two additional devices have been developed in France. The ZSI 375 (Zephyr Surgical Implants, France) was released in 2005 (http://zephyr-si.com/zephyr/index.php?lg=en.) and has not yet been approved by the French Health Authority Agency (http://www.has-sante.fr/portail/jcms/c_896387/zsi-375-cnedimts-du-24-novembre-2009-2254) despite publication of recent data. No strong basic (bench and animal) and/or clinical data are available, and the use of this device should be done under a prospective controlled study before extensive use. Indeed, only a few preliminary monocentric retrospective observational studies have been reported. There are no favourable comparisons with the AMS 800®, and as opposed to the two following devices, the Versatile Automated Device and electromechanical device, it has not followed, at least through published papers, the usual process of validation.
Chung et al.  have not mentioned the Versatile Automated Device recently designed by another French team , designed to obtain a lower exerted pressure on the urethral tissues and improve continence efficiency according to the patient's activity. In fact, this device includes a sensor, which automatically detects circumstances involving high bladder pressure and adapts the occlusive pressure accordingly. The device was evaluated using isolated goat urethra and, then, in vivo with encouraging preliminary results. Research studies (bench and animal) are still running and awaited.
An electromechanical device has also been developed by Valerio et al.  and recently tested in animals. Its principle is an electromechanical induction of alternating compression of successive segments of the urethra by a series of cuffs activated by artificial muscles. This ovine study showed that this device could provide continence. This new electronic-controlled sequential alternating compression mechanism avoided damage to urethral vascularity for at least 3 months after implantation. After this positive early step, long-term studies are needed before clinical application can be considered. Table 1 shows the innovative principles of each former model of the AUS.
|Device||More compact than the AMS 800®||Improved control of pressure during stress||Improved detection of the administered pressure||Adjustable||Key remaining questions|
|FlowSecure™||No||Yes||No||Yes||Pump perforation at pressurisation|
|Periurethral Constrictor||Yes||No||Yes||Yes||Controversial results on continence|
|Tape Mechanical Occlusive Device||Yes||No||No||No but simplicity of use with its on/off button||?|
|ZSI 375||Yes||No||No||Yes||No multicentre prospective controlled study|
|Versatile Automated Device||Yes||Yes||Yes||Yes||?|
In conclusion, in an era where AUS use is increasing, a new and more sophisticated device is probably needed. Whatever the use, in men or women, the AUS aims to mimic continence/voiding phases as close as possible to normal conditions. Nobody knows what the future holds for hydraulic and mechanical devices. The above-mentioned devices suggest that further studies are required to assess the safety and efficacy of these new generation AUS devices, in comparison with the so-called ‘gold standard’ AMS 800®. The developmental steps for these devices must include bench and animal studies, as well as feasibility studies in humans to control for safety and surgical efficiency. Figure 1 provides the main steps of development of medical devices. After a feasibility study to check the proof of concept, any clinical use must be preceded by multicentre controlled studies. All of these studies have to be done under ethical committee approval. The recent USA Food and Drug Administration (FDA) warning (http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/ImplantsandProsthetics/UroGynSurgicalMesh/ucm262299.htm) about prolapse meshes in women should warn all clinical research teams about the absolute need for careful evaluation for all new implantable human devices.