Monitoring Orthopedic Implants Using Active Telemetry

Schuylenbergh, Van; Puers, Robert; Rodes,; Burny,; Donkerwolcke,; Moulart,

doi:10.1109/iembs.1992.592944

Cited by 3 publications

(2 citation statements)

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“…Treatment of complicated bone fractures continues to be a challenge for modern medicine [1]. In fact, approximately 10% of all bone fractures will not heal properly [2].…”

Section: Introductionmentioning

confidence: 99%

Bio-implantable passive on-chip RF-MEMS strain sensing resonators for orthopaedic applications

Melik

Perkgöz

Ünal

et al. 2008

J. Micromech. Microeng.

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One out of ten bone fractures does not heal properly due to improper load distribution and strain profiles during the healing process. To provide implantable tools for the assessment of bone fractures, we have designed novel, bio-implantable, passive, on-chip, RF-MEMS strain sensors that rely on the resonance frequency shift with mechanical deformation. For this purpose, we modeled, fabricated and experimentally characterized two on-chip sensors with high quality factors for in vivo implantation. One of the sensors has an area of ∼0.12 mm 2 with a quality factor of ∼60 and the other has an area of ∼0.07 mm 2 with a quality factor of ∼70. To monitor the mechanical deformation by measuring the change in the resonance frequencies with the applied load, we employed a controllable, point load applying experimental setup designed and constructed for in vitro characterization. In the case of the sensor with the larger area, when we apply a load of 3920 N, we obtain a frequency shift of ∼330 MHz and a quality factor of ∼76. For the smaller sensor, the frequency shift and the quality factor are increased to 360 MHz and 95, respectively. These data demonstrate that our sensor chips have the capacity to withstand relatively high physiologic loads, and that the concomitant and very large resonant frequency shift with the applied load is achieved while maintaining a high signal quality factor. These experiments demonstrate that these novel sensors have the capacity for producing high sensitivity strain readout, even when the total device area is considerably small. Also, we have demonstrated that our bio-implantable, passive sensors deliver a telemetric, real-time readout of the strain on a chip. Placing two more resonators on the sides of the sensor to serve as transmitter and receiver antennas, we achieved to transfer contactless power and read out loads in the absence of direct wiring to the sensor. With this model, where telemetric measurements become simpler due to the fact that all sensor system is built on the same chip, we obtain a frequency shift of ∼190 MHz with an increase in the quality factor from ∼38 to ∼46 when a load of 3920 N is applied. Therefore, as a first proof of concept, we have demonstrated the feasibility of our on-chip strain sensors for monitoring the mechanical deformation using telemetry-based systems.

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“…Treatment of complicated bone fractures continues to be a challenge for modern medicine [1]. In fact, approximately 10% of all bone fractures will not heal properly [2].…”

Section: Introductionmentioning

confidence: 99%

Bio-implantable passive on-chip RF-MEMS strain sensing resonators for orthopaedic applications

Melik

Perkgöz

Ünal

et al. 2008

J. Micromech. Microeng.

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“…Today a variety of medical implants such as bone plates, total joint replacements, nails and screws are available. The design of such medical implants is twofold: on the one hand, fixation devices have to be strong enough to bear the load and protect the fracture site; on the other hand, they have to provide certain flexibility in order to stimulate and accelerate the formation of bone tissue, and to prevent bone resorption due to stress shielding [3][4][5]. As a result, implant design presents a need for balancing between mechanical stability and sufficient elasticity, and significant effort is put into the modeling and simulation of the mechanical 0960-1317/10/085005+14$30.00 behavior of implants under load combined with laboratory in vitro experiments.…”

Section: Introductionmentioning

confidence: 99%

Wireless implantable passive strain sensor: design, fabrication and characterization

Umbrecht

Wägli

Dechand

et al. 2010

J. Micromech. Microeng.

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This work presents a new passive sensor concept for monitoring the deformation of orthopedic implants. The novel sensing principle of the WIPSS (wireless implantable passive strain sensor) is based on a hydro-mechanical amplification effect. The WIPSS is entirely made from biocompatible PMMA and consists of a microchannel attached to a reservoir, which is filled with an incompressible fluid. As the reservoir is exposed to strain, its volume changes and consequently the fill level inside the microchannel varies. The wireless detection of the microchannel's strain-dependent fill level is based on ultrasound. The WIPSS' sensing principle is proved by finite-element simulations and the reservoir's design is optimized toward maximum volume change, in order to achieve high sensitivity. A fabrication process for WIPSS sensor devices entirely made from PMMA is presented. The obtained measurement results confirmed the sensor's functionality and showed very good agreement with the obtained results of the conducted FE simulations regarding the sensor's sensitivity. A strain resolution of 1.7 ± 0.2 × 10 −5 was achieved. Further, the determination of the cross-sensitivity to temperature and strains applied out of the sensing direction is presented. The response to dynamic inputs (0.1-5 Hz) has been measured and showed decreasing sensor output with increasing frequency. Test structures of the sensor device allow the application of a signal bandwidth up to 1 Hz. Therefore, the proposed sensor concept of the WIPSS presents a promising new sensor system for static in vivo strain monitoring of orthopedic implants. In combination with the developed ultrasound-based read-out method, this new sensor system offers the potential of wireless sensor read-out with medical ultrasound scanners, which are commercially available.

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Corrosion Behaviour of Metal/Ceramic Interfaces in Physiological Solutions

Rocha

Ferreira²,

Monteiro

2002

KEM

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In this work the in vitro degradation behaviour of the metal/ceramic interface formed between c.p. titanium and a fluorosilicate machinable glass-ceramic joined by brazing alloys of the Ag-Cu-Ti system is studied in a simulated physiological solution. In the past, the degradation behaviour of the metal/ceramic interface (altogether, the metallic and the ceramic component plus the metal/ceramic interface), was investigated by means of standard electrochemical techniques [1][2][3]. In this work, standard samples, which are representative, in terms of chemical composition, of the most important layers present at the metal/ceramic interface, were prepared in an arc-melting furnace, which allows melting to be performed under a protective atmosphere (Ar). Electrochemical techniques and standard immersion tests were used to investigate the degradation behaviour of each individual layer existing at the metal/ceramic interface. The self-passivating behaviour of the interface, which was observed both in vitro and in vivo in previous works, can be better understood on the basis of the present results. The degradation behaviour of the individual layers is correlated with the overall corrosion behaviour of the metal/ceramic interface. Results suggest that Ag and Cu have an important role regarding corrosion behaviour: while Ag contributes to the passivation of the interface, the Cu-rich layer of the metal/ceramic interface seems to be responsible for the major part of the Cu ions released to the physiological solution.

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Monitoring Orthopedic Implants Using Active Telemetry

Cited by 3 publications

References 0 publications

Bio-implantable passive on-chip RF-MEMS strain sensing resonators for orthopaedic applications

Bio-implantable passive on-chip RF-MEMS strain sensing resonators for orthopaedic applications

Wireless implantable passive strain sensor: design, fabrication and characterization

Corrosion Behaviour of Metal/Ceramic Interfaces in Physiological Solutions

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