Hypothesis / aims of study
Urethral bulking therapy is minimally invasive and well tolerated with few side effects, but clinical benefits are less than with sling and benefit is less durable with bulking. In the hands of some experts, results are much better suggesting that surgical technique and experience are important. Advances in bulking products have failed to demonstrate improved clinical outcomes in large multi-center studies. (1) NeuBulk proposes that improved targeting and delivery of bulking agents might yield significant advances. To this end, NeuBulk presents a novel device designed to simplify surgical technique, shorten the procedure time, and contribute to more consistent clinical outcomes.
Study design, materials and methods
Targeted interviews were conducted with 16 practitioners - urologists [7] and urogynecologists [9] - with 10-36 years of experience. Interviews revealed four main features contributing to expert satisfaction with urethral bulking devices:
• Simplicity and ease of use.
• Endoscopic guidance.
• Needle position support.
• Patient comfort.
Analysis of the technical challenges of expert bulking revealed problems with access and exposure, poor visibility, difficulty with needle passage and depth, and inconsistent contouring of cushions. With visible agents there is also evidence of unwanted escape of bulking agent from the needle puncture sites in the urethral lining, not only during the injection procedure but also over time. Anatomical urethral length is another recognized variable. (2) Unique to our method, core device components include an easy-to-use measure to gauge urethral length and allows the delivery device to be calibrated to conform with specific patient urethral anatomy , correcting for human variation.
Results
The initial goal was to design, develop and assess the feasibility of core device components with benchtop testing. Revisions and developments have progressed through porcine bladder models and fresh cadaver clinical simulations, which better emulate expected clinical use. In practice, we propose introduction of a single use, hand assisted video endoscopic targeting and delivery device to address some of the inherent technical challenges with urethral bulking. The core elements include:
1. The urethral measure is used to determine the urethral length. It has a slidable lockable fixture and graduated scale. The measured length is used to calibrate the matching slidable lockable fixture of the delivery device such that the fixed needle stop will limit the needle tip excursion to prevent puncture at the bladder neck.
2. The delivery device includes a slidable lockable needle guide and graduated scale. Three equally spaced arms are deployed by passage of the cystoscope 0 degree lens and function to triangulate and support the urethra holding the tissues steady in place to control surgical access and exposure. The device arms prepare the surgical field without the need for fluid flow and define three distinct target zones between the arms for bulking agent delivery. The fixed needle stop controls excursion of the needle tip towards the bladder neck, and needle guide channels control the depth of injection in the submucosa. Endoscopic view provides the surgeon with a clear view for control in shaping the contours of the cushions under direct vision. In addition, deployed arms form pressure gradients that constrain the flow of injected bulking agent to create distinct lozenge shaped cushions spaced midway between the arms. The needle track is longer and parallel to the line of the urethra avoiding puncture of the urethral lining and providing a more effective barrier to unwanted escape of bulking agent.
3. Injection needle of specific length such that the fixed needle stop will allow forward progress of the needle tip towards but not beyond the bladder neck to prevent penetration.
Interpretation of results
Simplifying the task of bulking, NeuBulk’s novel device provides excellent access and exposure and offers to standardize surgical performance towards expert technical delivery every time without puncturing the urethral lining.