Multiscale Sensing of Bone-Implant Loosening for Multifunctional Smart Bone Implants: Using Capacitive Technologies for Precision Controllability

Abstract

The world population growth and average life expectancy rise have increased the number of people suffering from non-communicable diseases, namely osteoarthritis, a disorder that causes a significant increase in the years lived with disability. Many people who suffer from osteoarthritis undergo replacement surgery. Despite the relatively high success rate, around 10% of patients require revision surgeries, mostly because existing implant technologies lack sensing devices capable of monitoring the bone–implant interface. Among the several monitoring methodologies already proposed as substitutes for traditional imaging methods, cosurface capacitive sensing systems hold the potential to monitor the bone–implant fixation states, a mandatory capability for long-term implant survival. A multifaceted study is offered here, which covers research on the following points: (1) the ability of a cosurface capacitor network to effectively monitor bone loosening in extended peri-implant regions and according to different stimulation frequencies; (2) the ability of these capacitive architectures to provide effective sensing in interfaces with hydroxyapatite-based layers; (3) the ability to control the operation of cosurface capacitive networks using extracorporeal informatic systems. In vitro tests were performed using a web-based network sensor composed of striped and interdigitated capacitive sensors. Hydroxyapatite-based layers have a minor effect on determining the fixation states; the effective operation of a sensor network-based solution communicating through a web server hosted on Raspberry Pi was shown. Previous studies highlight the inability of current bone–implant fixation monitoring methods to significantly reduce the number of revision surgeries, as well as promising results of capacitive sensing systems to monitor micro‑scale and macro‑scale bone–interface states. In this study, we found that extracorporeal informatic systems enable continuous patient monitoring using cosurface capacitive networks with or without hydroxyapatite-based layers. Findings presented here represent significant advancements toward the design of future multifunctional smart implants.

Multifunctional Smart Bone Implants: Fiction or Future?—A New Perspective

“…Indeed, higher sensibility is reported to detect small-scale debonding disorders, which is an important feature to identify early loosening states; nevertheless, different loosening states can also be detected ( Soares dos Santos et al (2021) ). Moreover, sensing can be provided by customized capacitive networks such that detection, controlled by extracorporeal informatic systems, can be extended over very small-scale implant surface areas up to the entire surface ( Peres et al (2022) ). Two other important advantages are supported by these capacitive sensing systems.…”

Towards Self-Adaptability of Instrumented Electromagnetic Energy Harvesters

“…The architecture and schematic diagram of the motion-driven electromagnetic energy harvester considered in this study is illustrated in Figure 1a-d. As shown in Figure 1a, it is composed by a hollowed cylindrical structure (12); two multi-layered coils (2) wound around a portion of the outer housing; and five hard magnetic elements, in which two (1a, 1c) are fixed to the end extremities of the container, and three (1b) are experiencing levitation (as they are positioned between the fixed ones). This is a non-complex architecture widely reported in the literature, which includes the fundamental elements of the transduction process, and it is also suitable for analyzing innovative optimization methodologies [5,6,14,26].…”

“…The coils are connected in series and electrically connected to a resistive load (Figure 1c). All magnets and coils are installed concentrically to the container body (12). One of the non-levitating magnets (1c) is fixed to the harvester lid (4), while the axial positioning of the other (1a) can autonomously be self-adapted inside the container by means of an open-loop processing system and according to the dynamics of the mechanical vibrational excitations.…”

“…The section increase in the inertial mass tip at extremity (42) allows the sensor (30) to acquire the dynamics of the inertial mass. The container (12) is positioned and firmly screwed (5,46) between two lids (4,48), which in turn are embedded in the supports (10,15); the entire instrumented harvester assembly is fixed with screws on the aluminium board (8). The actuation system is composed by a stepper motor (34), trapezoidal spindle screw (43), motor-spindle coupling (39), sliding nut (40), guiding shafts (44), tube (20), tube-nut fastener (17,18), tube-magnet coupling (49), sleeve bearings (25,47), supports (31, 36, 45), screws (32, 35, 37, 41), lock nuts (19) and studs (38).…”

“…In the past few years, energy generation from ambient mechanical sources has emerged as a promising methodology to inexhaustibly power both large-scale and small-scale electronic device systems [2][3][4].Regarding the scope of small-scale powering, a wide range of technologies require long-term operation, reduced performance losses, low maintenance and performance adaptability to external mechanical excitations [5]. These are emerging technologies aiming to develop high-performance autonomous remote sensors, multifunctional implantable biomedical devices, wearable devices, mobile applications, IoT and communication networks, among many others, in which the self-powering ability is recognized as critical [6][7][8][9][10][11][12].…”