# A COMPLIANT ANKLE ENDOPROSTHESIS TO TREAT ANKLE-HINDFOOT PATHOLOGY

> **NIH NIH R43** · FLEX ORTHOPAEDICS, INC. · 2024 · $299,996

## Abstract

PROJECT SUMMARY
The ankle and hindfoot are made up of complex interlocking bones and joints that work together to enable
movement of the foot. Unfortunately, these bones and joints can become severely damaged as a result of
disease or injury, leading to devastating pain and disability. Patients facing severe ankle-hindfoot damage have
limited treatment options: they can either amputate the leg below the knee, or pursue a salvage operation called
ankle-hindfoot arthrodesis (“fusion”), which involves using orthopaedic nails and screws to connect the bones in
the foot so that the joints no longer move. Unfortunately, about 30% of ankle-hindfoot fusions fail, requiring the
limb to be amputated anyway. Even for the estimated 70% of ankle-hindfoot fusions that are “successful”, the
functional outcomes are so severely restrictive that patients may eventually choose to have an amputation,
because a prosthetic leg would provide more function than their fused joints. In short, current treatment options
are so limited that patients and clinicians often choose to amputate the injured leg, even when the muscles, skin,
and other bones of the foot are still viable.
In this work, we aim to fundamentally reinvent the care paradigm for traumatic injury or disease of the ankle and
hindfoot by advancing a novel Compliant Ankle Endoprosthesis with the potential to restore function and alleviate
pain, without requiring fusion or amputation. By preventing limb loss and eliminating the need for ankle-hindfoot
fusion, our goal is to alleviate suffering and restore much more functional capacity than is currently possible.
Our product restores joint motion via deformation of flexible elements, rather than rubbing or sliding of bearing
surfaces. The device originated in one of the applicants’ engineering lab at UCLA. Feasibility of this product has
already been demonstrated in the applicant’s lab in simulation, on the benchtop, and in a large animal model. In
this work, we will conduct the late-stage pre-clinical studies required for regulatory approval of this device, prior
to clinical testing. Specifically, we intend to show that i) acute failure of the implant happens only under super-
physiologic loads and in a way that does not endanger the surrounding tissues, and ii) the implant has the
durability necessary to support human gait for decades inside the body. We will conduct this research over 12
months, and the data we obtain will be used in an FDA Investigational Device Exemption application to support
an early feasibility study, and in the NIH SBIR Phase II application. Major milestones to be achieved with this
grant include direct experimental validation of short- and long-term mechanical survivability of the Compliant
Ankle Endoprosthesis, in preparation for clinical testing.

## Key facts

- **NIH application ID:** 10923285
- **Project number:** 1R43AR084406-01
- **Recipient organization:** FLEX ORTHOPAEDICS, INC.
- **Principal Investigator:** Brandon Peterson
- **Activity code:** R43 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $299,996
- **Award type:** 1
- **Project period:** 2024-07-15 → 2027-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10923285

## Citation

> US National Institutes of Health, RePORTER application 10923285, A COMPLIANT ANKLE ENDOPROSTHESIS TO TREAT ANKLE-HINDFOOT PATHOLOGY (1R43AR084406-01). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10923285. Licensed CC0.

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