Renewal of Functional Expectations of Transhumeral Percutaneous Osseointegration Patients

About This Grant

For decades, orthopaedic endoprostheses have been manufactured using traditional machining techniques. Specifically, the stem of the endoprostheses would be fabricated using mills and/or lathes, then the osseointegrated (OI) region would be added onto the stem using small metal beads, then sintered for strength. Recently, additive manufacturing, also known as 3-dimensional (3D) printing, has been introduced to provide affordable devices for limited markets. Instead of the traditional multi-step machining process, both the endoprosthetic stem and the OI region are designed to be manufactured in one continuous process, saving valuable resources. While there are FDA-related issues to address before 3D-printed devices become commonplace in the US healthcare system, many short-term implanted medical devices like orthopaedic fixation plates, screws, pins and wires, and even some long-term dental devices like dental fillings, crowns, and dentures are now 3D-printed. However, 3D-printing of many devices, including percutaneous OI endoprosthesis, is not yet widely accepted by the FDA because of the lack of data verifying that the device designed meets the engineering requirements, and validating that the device produced meets the need for which it was designed. Because of this, 3D-printing manufacturers are apprehensive to put their devices directly into humans. Fortunately, our research team has a well-developed sheep forelimb amputation model which has been directly used for this application and has been accepted previously by the FDA as a valid, preclinical model. In this proposed study, we plan to replicate the existing human Percutaneous Osseointegrated Docking Systems (PODS) endoprostheses to develop a 3D-printed version for use in sheep, which we will call sPODS, an acronym for Sheep PODS. The sPODS will be manufactured not only using a 3D-printing process, but also using a traditional machining process to act as a baseline for direct comparison. Both the 3D-printed and the traditionally machined sPODS will have the same external geometry (length, diameters, tapers, etc.), with the only difference being the method used to create the device. Once manufactured, the 3D-printed and the traditionally machined sPODS will be verified through benchtop testing, measuring the amount of bone loss during implantation, the contact area between the bone and the endoprostheses, and the fixation strength post-implantation. This will verify that the device manufactured meets the specified engineering requirements. Next, production quality 3D- printed and traditionally machined sPODS will be surgically implanted into our amputated sheep metacarpal model and validated against our published historical sheep data, confirming that the device produced meets the need for which it was designed. This research project with the following Specific Aims: Specific Aim 1: To quantify the surface, material, and mechanical properties of the 3D-printed sPODS and the traditionally machined sPODS, then to measure and compare the initial tensile and torsional stabilities of devices implanted into sheep carcass metatarsals. Specific Aim 2: To validate that the bone morphology and the tensile and torsional stability of the 3D-printed sPODS are not inferior to traditionally machined sPODS following 6-months in situ in a sheep amputated metacarpal model. Prior to implementing PODS clinically, this study is essential to confirm that device design aligns with engineering and material requirements. Ultimately, these efforts will immediately contribute to enhancing functional independence and quality of life of the Veterans with transhumeral amputations but will also serve as guidance for all teams designing and testing 3D-printed percutaneous OI devices at any anatomic site.