Performance of a Piezoelectric Energy Harvesting System for an Energy-Autonomous Instrumented Total Hip Replacement: Experimental and Numerical Evaluation

Abstract

Instrumented implants can improve the clinical outcome of total hip replacements (THRs). To overcome the drawbacks of external energy supply and batteries, energy harvesting is a promising approach to power energy-autonomous implants. Therefore, we recently presented a new piezoelectric-based energy harvesting concept for THRs. In this study, the performance of the proposed energy harvesting system was numerically and experimentally investigated. First, we numerically reproduced our previous results for the physiologically based loading situation in a simplified setup. Thereafter, this configuration was experimentally realised by the implantation of a functional model of the energy harvesting concept into an artificial bone segment. Additionally, the piezoelectric element alone was investigated to analyse the predictive power of the numerical model. We measured the generated voltage for a load profile for walking and calculated the power output. The maximum power for the directly loaded piezoelectric element and the functional model were 28.6 and 10.2 µW, respectively. Numerically, 72.7 µW was calculated. The curve progressions were qualitatively in good accordance with the numerical data. The deviations were explained by sensitivity analysis and model simplifications, e.g., material data or lower acting force levels by malalignment and differences between virtual and experimental implantation. The findings verify the feasibility of the proposed energy harvesting concept and form the basis for design optimisations with increased power output.

Monitoring of Hip Joint Forces and Physical Activity after Total Hip Replacement by an Integrated Piezoelectric Element

“…The experimental test rig from Lange et al [33] was used for the measurements. The THR stem (Exeter V40, size 37.5 mm N • 3, Stryker, Howmedica Osteonics Corp., Mahwah, NJ, USA) with an integrated piezoelectric element (PICMA ® actuator, stacked configuration of two elements, outer diameter 5 mm, inner diameter 2.5 mm, height 5 mm, capacity 220 nF) from PI Ceramic GmbH (Lederhose, Germany) was cemented into an artificial femur bone (4th generation, large left, composite bone, solid foam core, Sawbones Europe AB, Malmö, Sweden) and fixed in a specimen holder with embedding resin (Figure 1).…”

“…KG., Munich, Germany) with a sampling rate between 1800 Hz (stance) and 10.3 kHz (jogging). More detailed information on the circuit diagram is described in Lange et al [33].…”

“…Previously, Lange et al [33,34] developed a THR with a self-sufficient energy supply. For this purpose, a piezoelectric element was integrated into a hip stem in such a way that the electrical output is as high as possible while at the same time ensuring mechanical safety.…”

Bioelectronic multifunctional bone implants: recent trends

“…These are low elecric current sources with appropriate behavior to power capacitive sensing/actuation, but with severe limitations concerning other sensing systems (e.g. the inductive ones) and processing systems, even if stacked multilayer piezoelectric elements are integrated (Lange et al 2020 , 2021a , b ). Triboelectric generators are widely researched to power both large-scale and small-scale devices (Vidal et al 2021 ).…”

Evaluation of Bone Consolidation in External Fixation with an Electromechanical System

“…As radiographic evaluation shows some limitations, several authors are trying to develop methods of healing assessment that can give information about the progression of the mechanical properties of the fracture repair tissue. For example, using implants with sensing capabilities [9,10] or instrumented implants can improve the clinical outcome of total hip replacements [11,12]. These innovative implants can be implementable, provide therapeutic benefits, and have diagnostic capabilities.…”