Bioelectronic multifunctional bone implants: recent trends

Abstract

The concept of Instrumented Smart Implant emerged as a leading research topic that aims to revolutionize the field of orthopaedic implantology. These implants have been designed incorporating biophysical therapeutic actuation, bone-implant interface sensing, implant-clinician communication and self-powering ability. The ultimate goal is to implement revist interface, controlled by clinicians/surgeons without troubling the quotidian activities of patients. Developing such high-performance technologies is of utmost importance, as bone replacements are among the most performed surgeries worldwide and implant failure rates can still exceed 10%. In this review paper, an overview to the major breakthroughs carried out in the scope of multifunctional smart bone implants is provided. One can conclude that many challenges must be overcome to successfully develop them as revision-free implants, but their many strengths highlight a huge potential to effectively establish a new generation of high-sophisticated biodevices.

Keywords: Bioelectonic implants; Biointegration; Implant technology; Instrumented medical device; Smart implants.

Fig. 1

a Architecture used to design non-instrumented active implants. b-e Instrumented passive implants (Graichen et al. , ; Heinlein et al. ; Westerho et al. 2009): hip (b), knee (c), shoulder (d) and spine (e) technologies. f Operations of instrumented passive implants

Fig. 2

a Operations of instrumented smart active implants (Peres et al. ; Sousa et al. 2021); b Master-slave distributed architecture of multifunctional smart implants (Peres et al. 2022a); c Co-surface capacitive stimulators incorporated within smart implants; d Single stripped and interdigitated electrode patterns, as well as a network stimulation design (l: electrode length; w: stripe width; g: gap between stripes) (Peres et al. ; Soares dos Santos et al. 2016b)

Fig. 3

a Sensing technology by extracorporeal mechanical excitation and intracorporeal mechanical transduction (Cachão et al. 2020) (1 - human tissue; 2 - extracorporeal coil to power the embedded electronics through magnetic induction; 3 - extracorporeal mechanical excitation; 4 - intracorporeal coil used to power the embedded electronics; 5 - intracorporeal monitoring system; 6 - extracorporeal coil to acquire data from the sensor through magnetic induction); b Sensing technology by extracorporeal magnetic induction and extracorporeal mechanical transduction (Cachão et al. 2020) (1 - extracorporeal coil providing movement to the oscillator; 2 - human tissue; 3 - oscillator inside the instrumented implant; 4 - extracorporeal accelerometer that measures vibrations from the oscillator’s impact; 5 - implant); c Instrumented fixation plate embedding a capacitive sensing system to monitor the bone healing process (Cachão et al. ; d) Co-surface capacitive sensing to monitor bone-implant interface states (1 - electrodes; 2 - eletric power source; 3 - bone structures; $\theta$ - angle inclination of electrodes; $\mathbf{E}$ - electric field) (Cachão et al. 2021)

Fig. 4

Comparative analysis to the performance of non-instrumented passive implants (nIPI), non-instrumented active implants (nIAI), instrumented passive implants (IPI) and instrumented active implants (IAI)