Spinal Fusion Implant with Embedded Biomechanically Powered Sensor

PROJECT SUMMARY
The objective of this Phase I SBIR is to develop a spinal fusion implant with embedded biomechanically
powered sensor. Evoke Medical’s core technology is to create human-powered implantable devices that utilize
piezoelectric materials to generate load-induced power. That power can then be used for various purposes:
electrical stimulation of bone growth and/or load-sensing to track fusion progression. Through our current Phase
II project, a fully integrated piezoelectric transforaminal lumbar interbody fusion (TLIF) implant was developed
with embedded power generator and miniaturized circuitry for signal conditioning. In this TLIF implant, lower
impedance piezoelectric materials were used to generate power for mechanically synced direct current (DC)
electrical stimulation delivered to an electrode on the implant surface for the purposes of enhancing bone growth.
No batteries are used in any Evoke Medical implant as all energy is biomechanically induced by human motion.
Our preliminary work has also shown that a piezoelectric interbody implant can act as a sensor and distinguish
between different applied physiological loads that correlate to fusion progression.
In other industries, piezoelectric materials are often used as load sensors. In situ, mechanical loads applied to
the piezoelectric device generate proportional electrical voltages that can be translated back to quantify the
applied load on the device. Evoke Medical will use this inherent ability of piezoelectric materials to characterize
the change in load environment within the disc space, and subsequently provide objective data to the clinician
and patient to inform post-operative outcomes and treatment decisions. In spinal fusion, the load on the implant
is highest when the device is first implanted and there is no bony fusion mass around and throughout the implant.
As fusion progresses, the load on the implant is reduced according to the fusion grade achieved due to the
increased surface area and stiffness of the growing bone structure. In this proposal, we will prove that a
custom piezogenerator embedded in a spinal fusion implant with the associated circuit hardware and
data acquisition software can collect, store, and wirelessly transmit changes in load within the interbody
space. These changes can then be related back to fusion progression and other post-operative outcomes.
Evoke Medical has already developed cost-effective manufacturing methods and demonstration of safety and
efficacy of the stimulating aspect of the piezoelectric TLIF that is moving forward in the commercialization
process through a DeNovo regulatory strategy. In these verification tests, we have also proven that we can
successfully harvest patient motion and convert that to usable power under physiological loading conditions. By
developing the load sensing aspect of the TLIF implant now, Evoke Medical will be able to jumpstart our
capabilities to provide patients with biofeedback on how their implant is helping them. It will give surgeons the
ability to quantify healing progress without the multitude of expensive CT scans or potentially biased patient
reported outcome measures. This will allow the physician to make informed postoperative treatment decisions
that could greatly improve the chances of fusion success. Commercialization of this remote load sensing data
tool for spinal fusion patient care is disruptive, will help to reduce healthcare costs, and simultaneously enhance
patient care, particularly in rural or remote areas or in times of limited access to healthcare providers (e.g. during
COVID-19).
In this Phase 1 project, we will first establish that utilizing a textured piezogenerator embedded in a TLIF implant
will power the necessary components in a prototype load sensing circuit. The functionality of integrating the
developed sensor circuit with a data acquisition framework will be verified through a large range of applied
physiologic load conditions. Proving that the Evoke piezoelectric TLIF can accurately sense and output
physiologic load data, differentiating between varying loads expected in fusion progression, will de-risk the
integration of sensing and bone stimulating capabilities.
The results of this work will set the stage for Phase II funding to integrate and miniaturize the sensing and
stimulating circuits to create an integrated, dual mode stimulating and sensing spinal fusion implant. As part of
this phase II work, additional in vivo validation ovine studies will be completed to justify moving forward with
commercialization. Following, additional funding will be raised to complete the necessary verification and validation
testing along with early clinical trials required for expanded regulatory claims around addition of the sensing
capability of the TLIF implant. The thoracolumbar spine interbody market is over $1.4B/year with a compound
annual growth rate of 2.9%. The proposed device is hypothesized to increase success of healing and decrease
time to heal, as well as give patients and healthcare providers quantitative outcome measures without expensive
CT scans or biased patient self-reporting. This would decrease overall cost of care and human suffering, as
earlier, data driven post-operative decisions could be made, preventing a failed fusion and additional revision
surgeries.