This is an early feasibility study designed to provide preliminary evidence for the safety and effectiveness of the Magnetic Bead Tracking System for the control of a one degree-of-freedom (DoF) ankle-foot prosthesis at the transtibial amputation level on up to N=5 study subjects. Each subject will serve as their own control in a repeated measures ('within subjects') design. During experimentation, each subject will have prosthetic gait performance measured while using the Magnetic Bead Tracking System compared to an intrinsic robotic controller.
The Magnetic Bead Tracking System consists of pairs of magnetic beads, and a set of magnetic field sensors that are intended to measure and track the length of muscles and the speed at which they move in real-time. The system uses multiple pairs of implanted magnetic beads to track tissue strains via an array of externally worn magnetic field sensors, which senses the relative locations of the implanted magnetic beads. When implanted in muscle in the residual limb of an amputee, the muscle length signal is used as an indicator of human intent and is conveyed to a robotic prosthesis, providing heightened, natural, reflexive control of prosthetic limbs in subjects with transtibial amputation. Specifically, in the proposed study, the system will be used with a computer controlled, powered ankle prosthesis to provide sensory position, speed, and force data to increase the accuracy of neuromuscular control models and allow for intuitive, simultaneous position and torque control of the prosthesis.
Safety of the Magnetic Bead Tracking System will be evaluated throughout the study by assessing the adverse event type, incidence, timing, severity, treatment, outcome, and relationship to the device. Adverse events with clinical signs or symptoms will be collected when volunteered by subjects and/or observed by Investigators. Serious Adverse Events will be reported on a per event and per subject basis up to 6 months. At each study visit, the subject will be asked to report any issues, and will have a comprehensive examination of the affected limb performed by study physicians and/or trained staff.
Due to the small number of subjects, this study will be treated as a case study. For each case, information, such as demographic and subject information, adherence to the study protocol, safety, and performance data will be collected and described. At the end of the study, each case will be evaluated, and a determination will be made, as to whether (1) any unanticipated adverse device effects and/or revisions/removals of the device occurred, and (2) the study objective was met for that particular case.
For each case, variables will be summarized qualitatively by visit and (where applicable) by difference from pre-op assessment and post-op assessments. This assessment will be performed separately for each case. In addition, a quantitative measurement of preferred walking speed will serve as a primary variable for the evaluation of system performance in AIM 1, and the time to traverse an obstacle course will serve as a primary variable for AIM 2.
