RR&D Research Career Scientist Award Application

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Patients with amputated limbs are customarily offered socket-based systems, which are stabilized by friction contact between the socket and the soft tissues of the residual limb. Despite the leading-edge care provided to patients with amputations by the VA Healthcare System, many abandon their conventional socket-based systems. In a study of veterans with combat-associated unilateral upper-limb loss, 25% of veterans abandon their socket- based prosthetics, with rates highest among women. To improve function and quality of life for these patients, percutaneous osseointegrated (OI) docking systems are being developed worldwide. The concept of OI is based on the ability of living bone cells to attach to a titanium surface and has been used for decades to anchor common dental and orthopaedic devices to living bone. My research takes me outside this paradigm. I engineer percutaneous OI devices, which require a load-bearing metal post to be connected to the OI endoprosthesis, passing permanently through the skin to be connected to the distal exoprosthetic componentry outside of the body. To date, the FDA has not approved the broad use of percutaneous OI devices within the United States. Unfortunately, several OI devices have been experimentally placed into patients by other groups using either unauthorized copies of European designs or using unproven modifications of devices off-label. Without FDA approval, the broad commercial introduction of percutaneous OI technology is limited in all healthcare systems. The overarching goal of my research is to maximize the functional recovery and the quality of life of US Veterans with limb loss. To achieve this, we need to bring safe, FDA approved percutaneous OI devices to this deserving patient population. Since 2006, I have led the engineering efforts of a multidisciplinary team that uses a data-driven approach to engineer percutaneous OI devices for amputees. We have followed a strict scientific approach with the goal of achieving FDA approval for use throughout the United States. My pre-clinical work ranged from basic bench-top science to numerous animal model trials, investigating basic principles of not only skeletal fixation, but also infection prevention at the stoma created as the percutaneous post passes through the skin. With these pre- clinical findings, we designed and manufactured a series of transfemoral percutaneous OI devices, we established the initial surgical procedures, manufactured appropriate surgical instrumentation, tested the initial biomechanical stability, and established the static mechanics and fatigue properties of the device. This pre-clinical work culminated in approval of the first FDA directed Early Feasibility Study (EFS) of a percutaneous OI device in a population of 10 veterans with transfemoral amputations. Information obtained via the transfemoral EFS is now being used to transition to a multicenter pivotal clinical trial for FDA approval and wide-range clinical adoption. Since 2014, I have expanded my efforts to serve patients with transhumeral amputations because of their profound functional losses and difficulties using conventional exoprostheses. We are completing the preclinical development of this device, establishing the initial surgical procedures, manufacturing appropriate surgical instrumentation, testing the initial biomechanical stability, and completing the design history file for submission to the FDA for consideration to conduct a transhumeral EFS. While the Primary Aim is to perform an FDA guided EFS of a percutaneous OI docking system for patients with transhumeral amputations, establishing its initial safety, the Secondary Aim is to use a patient-centered approach to quantify the functional effectiveness of the OI device with targeted muscle re-innervation to control the exoprosthesis. Information obtained via the transhumeral EFS will be used to help to transition to a multicenter pivotal clinical trial for FDA approval and wide-range clinical adoption.