PIEZOKNEE
Intelligent orthopedic implants offer exciting prospects, particularly for improving post-surgical follow-up. Today, however, the technologies available for their power supply are not suited to powering the all-metal prostheses used in orthopedics. The Piezoknee project aims to exploit a wireless power transmission solution based on acoustic waves (APT: Acoustic Power Transmission) to power an intelligent knee implant (SOI: Smart Orthopedic Implant) capable of transmitting physiological information (temperature, pH, mechanical stress) to help prevent any complications.
Project background
Orthopedic prostheses account for a significant proportion of implants fitted each year, mainly total knee replacements (TKRs). Over the past decade, the number of TKRs has doubled in OECD countries, and could quadruple by 2030. This expansion is essentially due to an ageing population, increasing obesity, but above all to indications from younger patients with less advanced osteoarthritis. However, early intervention can lead to complications that often require repeat surgery. These repeat operations are more costly, and require more rigorous medical follow-up: a SOI equipped with APT communication would enable this patient follow-up.
Project objective and relevance
A model of the knee joint will be developed using new statistical modeling methods incorporating acoustic parameters. In addition, permissible input power levels will be studied to limit physical mechanisms (thermal, cavitations) and remain below the values set by standards and used by commercial ultrasound equipment. This model and input data will then be used to design and optimize the acoustic power transmission system, using both analytical and finite element multi-physics modeling, integrating the piezoelectric transducers into the implant. We are targeting a power received in the implant of between 1 mW and 10 mW, while complying with medical standards and using commercial ultrasound probes on the transmitter side. The prototypes will be assembled and tested first on five knee phantoms developed as part of the project, and then on three cadaveric specimens in the anatomy laboratory at the CHRU in Brest. Proofs of concept (PoCs) will then feed into a new generation of intelligent orthopedic implants incorporating sensors, which will be more robust and reliable, facilitating industrialization and ultimately enabling better clinical management.
Approach
Managed by LaTIM, WP1 (see Figure 1) provides the knee model integrating anatomical (T1.1) and acoustic (T1.2) data to design the system. TIMA will study the requirements in terms of power limits, frequencies and exposure times, correlating system requirements with current medical standards. At the same time, preliminary tests will be carried out using commercially available acoustic transducer probes, which is essential to reassure clinicians and reach out to industry. It will be pertinent to exploit all the material possibilities of existing medical devices (while respecting emission standards), while sizing a dedicated and specific acoustic receiver on the implant side. Thanks to its experience in modeling multi-physical systems, the CEA will manage WP2. In conjunction with TIMA, CEA will propose the design and modeling of the receiver(s). CEA will propose intermediate prototypes and experiments (T2.1), based on "simple" geometries and using the first elements of WP1 (initial version of the 3D model, input power limits according to standards, etc.). These intermediate prototypes will be characterized to refine the models and verify the order of magnitude of the power received on simple geometries.
Figure 1: proposed methodology and links between tasks and partners
Expected results
The final prototype, i.e. an optimized APT solution integrated into a knee prosthesis, will be optimized and manufactured by CEA, making full use of the final version of the 3D acoustic knee model supplied by LaTIM (T1.1) and following TIMA recommendations (T1.2). Both versions ("simple" and final geometries) will be tested on 5 cadaver specimens (T3.1 and T3.2 of WP3) in the anatomy laboratory of LaTIM's PLATIMED platform, in close collaboration with orthopedic surgeons. Quantities such as overall conversion efficiency and transmitted electrical powers will be measured for different input conditions (input powers, frequencies, transmitter placement on the knee, etc.). Validation will compare the performance of the APT with that of the well-known inductive coupling developed as part of the Followknee project, under the same measurement conditions. A factor of 10 is expected in transmitted power or power density in a similar volume, while significantly improving mechanical robustness and sealing feasibility. This would make it possible to increase the functionality of the implanted system (i.e. more sensors in a similar volume) or reduce the size of the receiving part to facilitate miniaturization or morphological customization of the implant.
Academic and industrial partners from France and abroad
PiezoKnee represents a decisive step towards a new generation of SOI. Complementing each other, the consortium partners propose to combine multiparametric statistical modeling of anatomical data (LaTIM) and multiphysics modeling for acoustic power transfer (CEA), constrained by standard limitations in terms of power, frequency and exposure time (TIMA). The overall scientific ambition of PiezoKnee is to validate a new design method in the field of acoustic power transmission for orthopedic implants. A close link between input data (anatomical models, material properties and maximum input powers) and modeling tasks will also enable the placement, shape and number of receivers inside the knee implant to be optimized.
Next steps
The aim of SOI is to limit the number of reworks. In this way, they initiate a virtuous circle: a better understanding of biomechanics and pathophysiological phenomena in vivo thanks to the data provided by integrated sensors, with the aim of further improving implants and surgical techniques for greater clinical benefit. APT technology is a response to the growing need for electrical power, which limits the market introduction and integration of SOI into clinical routine, which remains a challenge.
Label
Minalogic competitiveness cluster