Title: Development and prototyping of improved surgical devices for management of anal fistula
Funder: Department of Health and Social Care

Abstract: The project plan derives from a partnership of expert users (colorectal surgeons) and design-engineers (Renfrew Group International). A milestone driven plan will comprise several well-defined stages which will take the product from concept drawings through to handover to high volume production. Stage 1: Diagnosis Observational analysis of current surgical procedures and instruments by team visits to theatres at the Royal London and St Marks' Hospitals. The team will be familiarised with the current problem, initial proposed solutions (as herein contained) and main anatomical and anthropometric data; refinement of the brief on this basis will follow. Further detailed searches of existing IP will be performed and reported and a strategy to avoid infringement agreed. Suppliers of currently used equipment will be contacted if necessary. The defined problem, considering other procedures and instruments, methods for construction of the proposed concept and solutions will be brainstormed at Rocket studios, Leicester to enhance concepts through detail engineering and innovative design. A lateral thinking session involving key team members will allow interaction to consider options and extract maximum collaborative creativity. Visualisation by hand sketches will be followed by simple CAD models (RGi team of industrial designers with in house engineering and moulding). Milestone I: On completion of the stage we will have reviewed, revised and refined the brief (if necessary) and agreed the project plan in detail. We will have brainstormed a variety of solutions and recorded these for stage 2 direction. The output of Stage 1 will be concept CAD or hand sketches to incorporate these points. Stage 2: Concept design and engineering Development of one concept using (ProE) CAD and physical models; liaison with toolmakers, material suppliers, compliance agents, manufacturing agents, moulders etc. Development will include consideration for anthropometric data, ergonomics in use, manufacture and disposal. The design principles and concept aims agreed in stage 1 will be maintained where production and practical requirements allow. Samples will be obtained of materials and LED assemblies. Milestone II: On completion of stage 2, we will have agreed the final configuration of the preferred arrangement and created CAD data for prototypes. Stage 3: Concept prototyping and lab tests From CAD data, functioning prototypes (at least 2 iterations) will be created to demonstrate the mechanical properties of the devices including tube forms, snap off LED and seton insertion. Milestone III: CAD refinement. Stage 4: Detail design engineering Incorporating feedback from samples produced stage 3, products will be optimised for production with best quality/cost balance; drawings will be produced for IP protection. Early liaison with partner manufacturing company will tune design to suit manufacturing tolerances and to support regulatory approval. Milestone IV: Preparation of data for in house injection mould tooling. Stage 5: Prototyping &ndash; low volume manufacture Design of injection mould and extrusion tooling, CNC machining of low volume tooling (Aluminium) and manufacture of small quantities in real polymer. Liaison with production moulding company to ensure efficient translation to volume manufacture. Sterilisation of prototypes with Gamma or Electron Beam Radiation. Milestone V: Sample batch sizes of 10 at a time. Stage 6: User feedback on low volume prototype Batches of the prototype will be provided to a panel of approximately 10 colorectal surgeons within Enteric clinical network (see NIHR infrastructure section). Milestone VI: Feedback provided on a minimum of 20 patients undergoing fistula surgery with the new probes Stage 7: Pre production design Further design/engineering development and prototype manufacture based on stage 6 feedback; full DFMA of components and assembly and injection mould tool development. Liaison with manufacturing partners. Milestone VII: Supply of complete manufacturing data.

Lay abstract: An anal fistula is an abnormal connection between the lining on the inside of the anal canal (back passage) and the skin near the anus. Most anal fistulae are caused by an abscess (a collection of pus) just outside the anal canal which then drains away onto the skin on its own or by an operation. A fistula happens when the track, made by the pus on the way to the surface of the skin, stays open. This leads to problems such as pain, persistent discharge and ultimately damage to the anal sphincter muscles. Nearly all treatments for anal fistula involve surgery. Numerous operations exist to try and cure the fistula but these usually require division of some of the anal sphincter muscle with a subsequent risk of incontinence. Thus high fistulae (denoting those which cross a lot of muscle) cannot be safely cured and instead symptoms may be controlled by insertion of a special stitch called a seton which runs through the cleaned fistula track and allows chronic but controlled drainage preventing further damage from infection and abscess formation. The current methods to place a seton at operation use a variety of metal sterilised probes that are broadly unchanged since the 1920s. These are still effective in most circumstances but occasionally pose difficulties for the surgeon, particularly in high fistulae. Thus there is considerable room for improvement. The current proposal aims to develop new disposable probes with several special features to aid safe insertion and struggle-free placement of the seton. The proposed work will scope the design and materials required for these probes as well as performing early trials on suitable patients with anal fistula. If successful, UK manufactured probes will be progressed to market within a 3 year timeframe.

Research activity codes: 5.3 MEDICAL DEVICES
Health categories: ORAL AND GASTROINTESTINAL