Implantable Systems for Stress Urinary Incontinence KENANA M. AL ADEM, 1 SARAH S. BAWAZIR, 1 WALEED A. HASSEN, 2,3 AHSAN H. KHANDOKER, 1 KINDA KHALAF, 1 TIM MCGLOUGHLIN, 1 and CESARE STEFANINI 1 1 Department of Biomedical Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, UAE; 2 Cleveland Clinic Lerner College of Medicine of Case Western University, Cleveland, OH, USA; and 3 Urology, Surgical Subspecialties Institute, Cleveland Clinic, Abu Dhabi, UAE (Received 10 April 2017; accepted 29 September 2017) Associate Editor Peter E. McHugh oversaw the review of this article. Abstract—Stress urinary incontinence (SUI), the involuntary urine leakage due to failure of the urethral closure mecha- nism, is a global health challenge with substantial human suffering and socioeconomic costs. Approximately 167 mil- lion male and female patients are predicted to suffer from SUI in 2018, worldwide. A wide range of surgical interven- tions are available for the treatment of SUI. Severe cases, however, usually require the implantation of artificial urinary sphincter devices. This review comparatively presents and analyzes the working principles, as well as the challenges, associated with the current implantable SUI systems in clinical use. These include slings, urethral bulking agents, artificial urinary sphincters, and adjustable continence de- vices. It further reports on recent research progress and state- of-the-art in the field of SUI implants, including an original approach proposed by the authors with a pressure feedback sensory mechanism. The new emerging field of artificial muscle devices, including electroactive polymers, provides a promising innovative solution for replacing the weakened urethral sphincter in SUI patients. Keywords—Artificial urinary sphincter, Sling, Urethral bulk- ing agent, Feedback mechanism, Artificial muscle, Bionic sphincter design. ABBREVIATIONS AUS Artificial urinary sphincter BAMS Bone anchored male sling DEA Dielectric elastomer actuator EAP Electro-active polymers ICS International Continence Society ISD Intrinsic sphincter deficiency SMA Shape memory alloy SIS Single incision sling SUI Stress urinary incontinence TOT Transobturator tape TVT Tension-free vaginal tape UBA Urethral bulking agent UI Urinary incontinence INTRODUCTION The International Continence Society (ICS) defines stress urinary incontinence (SUI) as the involuntary loss of urine during physical exertion, coughing or sneezing. 96 SUI is a major age-related health challenge that affects the quality of life (QoL) of a large number of female and male sufferers, worldwide. 25,75 Patients with SUI may suffer from sexual dysfunction, social isolation, sports and exercise withdrawal and major depression. 93 SUI has considerable economic impact both on individuals and healthcare systems. Diagnostic and treatment costs of UI as well as indirect costs such as income loss were estimated to reach to $19.5 billion in the United States. 43 Irwin et al. estimated SUI to be the most common type of UI globally due to its high prevalence in wo- men. Approximately 127 million women and 10 mil- lion men experienced SUI in 2008. 167 million patients worldwide are predicted to suffer from SUI by 2018. 46 The urinary continence mechanism requires intact central and peripheral nervous systems, adequate activity of the urethral sphincter and pelvic floor musculature as well as normal anatomy of the lower urinary tract system. The failure of any of these com- ponents can lead to inadequate resistance of the ure- thra during times of elevated intra-abdominal pressure resulting in SUI. 54,110 SUI can be categorized as due to Address correspondence to Cesare Stefanini, Department of Biomedical Engineering, Khalifa University of Science and Tech- nology, P.O. Box 127788, Abu Dhabi, UAE. Electronic mail: cesare. stefanini@kustar.ac.ae Annals of Biomedical Engineering (© 2017) DOI: 10.1007/s10439-017-1939-9 © 2017 Biomedical Engineering Society