Magnetic bead tracking to control a bionic ankle for below-knee (transtibial) amputees

A Feasibility Study Evaluating the Magnetic Bead Tracking System and Its Safety and Effectiveness When Used With a Bionic External Prosthesis to Improve Prosthetic Controllability for Persons With Transtibial Amputation

This trial will test whether implanted magnetic beads and external sensors can help people with transtibial (below-knee) amputations control a powered ankle prosthesis more naturally.

Quick facts

• Phase: Early Phase 1
• Study type: Interventional
• Enrollment: 3 (estimated)
• Ages: 22 Years to 65 Years
• Sex: All
• Sponsor: MuscleMetrix, LLC (Industry-sponsored)
• Drugs / interventions: chemotherapy
• Locations: 1 site (Boston, Massachusetts)
• Trial ID: NCT07195461 on ClinicalTrials.gov

What this trial studies

This is an early feasibility study in up to five participants to gather preliminary safety and effectiveness data on the Magnetic Bead Tracking System used with a powered ankle prosthesis. The system uses pairs of magnetic beads implanted in residual limb muscles and an array of external magnetic sensors to measure muscle length and speed as a proxy for movement intent. Each participant serves as their own control in a repeated-measures design that compares gait performance using the magnetic tracking system versus an intrinsic robotic controller. Study procedures include surgical implantation, prosthetic gait testing, and follow-up visits at Brigham and Women's Hospital.

Who should consider this trial

Good fit: Adults aged 22–65 with unilateral or bilateral transtibial amputation (or planned transtibial amputation after exhausting limb-salvage options), who can ambulate at a K3 functional level or higher and are medically cleared for implantation.

Not a fit: Patients who are non-ambulatory, have poor residual muscle function, active infection or other surgical contraindications, or who do not want implanted devices or intensive on-site testing are unlikely to benefit from this intervention.

Why it matters

Potential benefit: If successful, it could enable more intuitive, reflexive control of powered ankle prostheses and improve walking accuracy and comfort for some transtibial amputees.

How similar studies have performed: The implanted magnetic bead tracking approach is novel and supported mainly by early preclinical and pilot human work rather than large-scale proven success to date.

Eligibility criteria

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.

Where this trial is running

Boston, Massachusetts

• Brigham and Women's Hospital — Boston, Massachusetts, United States (Recruiting)

Study contacts

• Principal investigator: Matthew J. Carty, M.D. — Brigham and Women's Hospital
• Study coordinator: Deborah Grayeski, JD

Conditions Transtibial Amputee; Transtibial Amputation; transtibial; amputation; amputee; magnet; prosthesis