Feasibility Study Evaluating the Safety and Effectiveness of Magnetic Bead Tracking System When Used With a Bionic External Prosthesis

Inclusion Criteria:

* 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).
* The patient must have adequate soft tissue bulk and muscle mass present in the operative limb to support appropriate wound healing.
* The patient must demonstrate volitional activation of the muscles into which magnet placement is intended.
* In the opinion of the investigator, the patient must likely be able to tolerate the pressure of a prosthetic socket during ambulation post-operatively.
* In the opinion of the investigator, the patient must have absence of any physical limitations, addictive diseases or underlying medical conditions that may preclude the patient from being a good study candidate.
* The patient must have willingness, ability and commitment to participate in baseline and follow-up evaluations for the full length of the study.
* The patient must have willingness and ability to provide informed consent to participate in the study.

Exclusion Criteria:

* 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.
* Patients for whom skeletal growth is not complete. Completed skeletal growth is defined through the finding of generally closed epiphyseal zones on X-ray.
* Patients with advanced atrophic muscle and/or compromised soft tissue coverage in the operative limb.
* Patients with evidence of or a documented history of severe peripheral vascular disease, diabetes mellitus (type I or type II), skin diseases, neuropathy or neuropathic disease and severe phantom pain, or osteoporosis, such that, in the opinion of the investigator, will not allow the patient to be a good study candidate.
* Patient with a history of systemically administered corticosteroids, immune-suppressive therapy or chemotherapy drugs within six (6) months of implant surgery.
* Patients with a known need of future MRIs.
* Patients currently involved in another clinical study where that participation may conflict or interfere with the treatment, follow-up or results of this clinical study.
* Active smokers will be excluded from candidacy; those patients willing to undergo tobacco cessation will need to be completely abstinent from tobacco use for at least 6 weeks preoperatively.
* Women who are pregnant, lactating or planning a pregnancy during the first twelve (12) months of the post-surgical follow-up.
* Patient having an allergy to any component of the device.
* Patients with concurrent illness, disability or geographical residence that would hamper attendance at required study visits.