The investigation is an early feasibility study in up to 5 subjects, in which the primary objective is to capture preliminary safety and effectiveness information on the Magnetic Bead Tracking system.
Male or Female age 22-65 at the time of surgery.
The patient must already have an existing unilateral or bilateral transtibial amputation requiring revision or a medical condition requiring performance of a unilateral or bilateral transtibial amputation.
If the patient does not already have an amputation, the patient must have undergone independent consultation with a lower extremity surgical specialist to ensure they have exhausted all limb salvage options prior to undergoing amputation, as well as a psychiatric evaluation to ensure appropriate capacity and volition, and a pain medicine evaluation to ensure that all pain control options outside of amputation have been addressed.
The patient must have the ability to ambulate at variable cadence (an expected lower extremity prosthesis functional level of K3 or above, as determined by a trained and certified prosthetist and confirmed by study investigators, through use of a patient history and physical examination).
Patients with any active skin disease in the subject limb.
Patients with severe comorbidity, atypical skeletal anatomy, or poor general physical/mental health that, in the opinion of the Investigator, will not allow the patients to be a good study candidate (i.e., other disease processes, mental capacity, substance abuse, shortened life. expectancy, vulnerable patient population, etc.).
Patients with the following concurrent diseases: active infection or dormant bacteria, metabolic bone disease and/or metastatic lesions in the residual tibia.
Patients weighing over 285 lbs. with the prosthesis, at time of screening.
Single group
Magnetic Bead Tracking System
DeviceThe Magnetic Beads will be implanted in a subject during either an already required revision of an existing unilateral or bilateral transtibial amputation or during the performance of a unilateral or bilateral transtibial amputation.
Walking Speed
The preferred and fastest walking speeds across level-ground and uneven walking surfaces will be measured as the primary study variables for AIM 1. To make these measurements, the time duration will be measured for each study subject to walk at steady state speed overground across 10m walkways at their preferred and fastest walking speeds. Subjects will receive standardized instructions encouraging them to either walk at their comfortable walking speed, or at their maximum walking speed, across each level-ground andan uneven 10m walkway. The investigators expect that the preferred and maximum speeds will be higher when employing the magnetomicrometry (MM) prosthetic controller compared to the commercial intrinsic controller, in support of the H1 hypothesis.
Obstacle course speed
The time to traverse an obstacle course will be evaluated to test obstacle avoidance, changes in walking direction, slope/stair variations, and speed transients, testing the ability of each controller to deliver rapid gait maneuvers while subjects walk across the unstructured environment. The investigators expect that the time to complete the obstacle course will be lower when employing the MM controller compared to the commercial intrinsic controller, further supporting the H1 hypothesis.
Walking Distance
The Six Minute Walk Test (6MWT) across a level-ground surface will be evaluated, or the maximum distance a person can walk in a six-minute period. Using an indoor track, the total distance each subject can walk throughout a six-minute interval will be measured for each controller (magnetomicrometry (MM) vs. Intrinsic). The investigators expect that the 6MWT will be higher when employing the MM prosthetic controller compared to the commercial intrinsic controller, further supporting the H1 hypothesis.
Gait Symmetry
Asymmetry between the double-support time preceding intact limb (tdspi) and preceding prosthetic limb (tdsip) transitions will be measured on level ground and slopes (instrumented treadmill), and for stair ascent and descent. The investigators expect that a composite measure of Gait Symmetry will demonstrate the best performance when the powered ankle-foot prosthesis is controlled using the MM controller, further supporting the H1 hypothesis.
Biologic Realism
Prosthetic and unaffected leg ankle net-work, wA , will be measured as defined in \[2\] on level ground and slopes (instrumented treadmill), and for stair ascent and descent. The investigators expect that the net-work measures when employing the MM controller will more closely match that of the contralateral intact ankle than compared to the commercial intrinsic controller, further confirming the H1 hypothesis.
Musculoskeletal Stress
Bilateral knee moments will be measured as defined in on level ground and slopes (instrumented treadmill). The investigators expect the contralateral knee adduction moment measure of musculoskeletal stress to be lowered when employing the MM controller as compared with the intrinsic controller, further supporting the H1 hypothesis.
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