Background

THE PROBLEM: More than 47,000 wrist fractures were reported during 2015 in Canada alone [1]. Actual numbers of fracture cases are expected to be higher due to incomplete reporting in some provinces. Current state-of-the-art treatment for distal radius fracture consists of surgical open reduction and internal fixation with plates and screws followed by immobilization for 6 weeks [2]. This is disruptive to the patient’s life and can threaten their independence [3].

Glass polyakenoate cements (GPCs) have been used for over forty years in dentistry and over twenty in ear, nose and throat surgery. They are candidate materials for percutaneous fracture fixation as they are injectable, chemically adhere to bone and can be formulated to have anti-bacterial and osteogenic properties [4–11]. The consortia are developing these materials for clinical use for which they need to be free of aluminium (Al), a component of all commercially available dental GPCs. Towler holds one patent on a strontium-containing, Al-free GPC for fracture fixation [12] and Towler and post-doctoral fellow (PDF) Alhalawani have a patent application around a second, tantalum-based composition currently at PCT [13].  These proprietary compositions have been the subject of a wealth of laboratory and biomechanical testing [14,15] including evaluation in animal models and their applicability for percutaneous fracture fixation in human cadaveric arms has been postulated [16].  Towler has also filed a provisional patent application around a disposable delivery device for storing, mixing and delivering the proprietary adhesives [17] and it is this device that forms the basis of the application. The objective of this I2I application is to optimize the patent-pending delivery device, principally for the novel bioadhesive, but potentially for applications in the coating, sealant and construction industries. 

North America remains the leading consumer of disposable syringes [18]. The global prefilled syringes market is estimated to reach $7B by 2023; a 50% increase over the 2016 market [19]. The alpha prototype device is designed by Towler and manufactured by Protodev Canada (Ottawa, ON). The kit (the adhesive and delivery device) is effectively a pre-filled syringe which can be stored in the clinic and offers both mixing and delivery of the adhesive to the surgical site through a cannula that can be attached to the nozzle in the end of the kit. The device has undergone filling, sterilization, mixing and delivery trials.  Operational outages have been identified around the devices’ robustness, unnecessary complexity, sterilisability and utility.

THE SOLUTION: The intent of this project is to re-design the patent-pending delivery device within both the parameters of the patent and with respect to freedom to operate (FTO, with respect to other patents) based upon the following activities:

Activity 1: Robustness: Sections of the device (the handles on the side and the top; Figure 2) failed during the delivery. Prototypes will be redesigned such that are able to withstand higher forces.

Activity 2: Complexity: The mixing chamber (Figure 1) is filled with ionomeric glass, and the centre cylinder B is filled with aqueous poly(acrylic acid). The current design, made of ten components, requires the entire delivery device to be disassembled to its constituent parts in order to insert the reagents.  In the event of problems in mixing the components, the device must be re-opened. 

Activity 3: Sterilizability: Irradiation of the delivery system using 25 KGy Gamma rays was performed on the prototype. Although the kit was successfully sterilized, the sections of the kit made from lighter coloured plastic exhibited discoloration as a result of chain scission [21].

Activity 4: Utility: An opportunity has been identified to expand the kit into other applications, both clinical (delivering larger adhesive volumes to the humerus or sternum) and industrial (the delivery of epoxies for metal coatings or as structural glues).  These applications will require a redesign of the device to ensure that it can store, mix and deliver larger amounts of these and, potentially, other adhesives.  Larger devices will be manufactured based on the final design from Activities 1-3. This device, with double the chamber size, will undergo mixing tests to determine the ability of the larger device to uniformly mix the increased volume of cement.