System for measuring, monitoring and / or processing at least one physical parameter, smart orthopedic implant, and method for measuring, monitoring and / or processing at least one physical parameter

Abstract

A smart orthopedic implant for measuring at least one physical parameter related to the smart orthopedic implant comprises a capacitor electrically conducive connected to at least one primary coil forming a passive LC-resonant circuit. The capacitor electrodes are movable with respect to one another, and / or the at least one primary coil and a further primary coil are movable with respect to one another. A force acting on the at least one implant body causes a relative motion between the capacitor electrodes or between the primary coils, causing a change in the resonance frequency and / or coupling coefficient of the at least one electrical circuit.

Description

[0001] System for measuring, monitoring and / or processing at least one physical parameter, smart orthopedic implant, and method for measuring, monitoring and / or processing at least one physical parameter

[0002] Technical field of the invention

[0003] The present invention generally relates to the field of implants, preferably orthopedic implants. In particular, the present invention relates to a smart orthopedic implant for measuring at least one physical parameter related to the smart orthopedic implant and / or the tissue it is implanted into as well as a system to measure, monitor and / or process said at least one physical parameter and a method to measure, monitor and / or process said at least one physical parameter using the disclosed system.

[0004] Background of the invention

[0005] Orthopedic implants are widely used in the treatment of musculoskeletal disorders and injuries, providing support, stability, and functionality to damaged or degenerated joints and bones. These implants are designed to restore mobility, alleviate pain, and improve the quality of life for patients suffering from conditions such as osteoarthritis, fractures, disk prolapses or deformities. For the scope of this description and the following claims, the term patient may include any animal, preferably animals which are used in medical studies such as mice, rats, rabbits, pigs, sheep, goats, etc. and even more preferably humans.

[0006] Despite significant advancements in implant design and materials, the long-term success and functionality of orthopedic implants depend on various factors, including proper implant positioning, biomechanical loading, and patient-specific factors such as bone quality, osteointegration rate and healing response. Complications such as implant loosening, infection, and implant wear remain significant challenges in orthopedic surgery, leading to revision surgeries, decreased implant longevity, and increased healthcare costs.

[0007] The integration of smart sensors into orthopedic implants represents a promising approach to address these challenges and improve patient outcomes. Smart sensors, particularly those based on LC (inductance-capacitance) circuits, offer several advantages in orthopedic applications, such as:

[0008] • Operation-time Implant Position Monitoring: Smart sensors can provide the surgeon with the necessary information about the implant positioning during the operation, detecting possible misalignment as early as possible and thus helping to reduce the revision rates of surgeries.

[0009] • Early Detection of Implant Complications: Smart sensors integrated into orthopedic implants can provide real-time non-invasive monitoring of implant stability, biomechanical loading, and tissue response. By detecting changes in implant position, strain, or tissue characteristics, these sensors can alert healthcare providers to potential complications such as implant loosening, infection, or bone fracture at an early stage, allowing for timely intervention and prevention of further damage.

[0010] • Quantitative Assessment of Implant Performance: Smart sensors enable quantitative assessment of implant performance and functionality, providing objective data on factors such as implant stability, range of motion, and joint loading. This information can help healthcare providers optimize implant positioning, monitor osteointegration rate, customize rehabilitation protocols, and track patient progress over time.

[0011] • Personalized Treatment Planning: By collecting data on patient-specific biomechanics, activity levels, and tissue response, smart sensors facilitate personalized treatment planning tailored to each patient's unique needs and circumstances. This can lead to more precise implant selection, optimized surgical techniques, and individualized rehabilitation strategies, ultimately improving patient outcomes and satisfaction.

[0012] • Long-Term Monitoring and Follow-Up: Smart sensors allow for long-term monitoring of implant performance and patient outcomes, enabling continuous assessment of implant integrity, functionality, and patient satisfaction over time. This long-term data can aid in clinical decision-making, identify trends or patterns in implant performance, and guide revisions or adjustments as needed to ensure optimal long-term outcomes.

[0013] In summary, the integration of smart sensors into orthopedic implants offers significant potential to enhance the safety, reliability, and functionality of these implants, ultimately improving patient outcomes and quality of life. By providing real-time monitoring, quantitative assessment, personalized treatment planning, and long-term follow-up, smart sensors empower healthcare providers to deliver more effective and patient-specific care in the field of orthopedics.

[0014] So far, most known smart implants are not passive, i.e. they need an internal or external source of energy. In some cases they use a non-rechargeable battery, that has a limited period of life on the one hand, while on the other hand it is potentially hazardous due to the chemicals used in the battery. These two factors limit the use of such concepts, complicate the implant’s design and eventually increase the implantation costs.

[0015] An external energy source may be provided in form of inductive energy harvesting methods. Such solutions may either work only while the energy is being transmitted or may charge rechargeable batteries incorporated into an implant to ensure autonomous work at least for some time. Similar concepts are disclosed in the related patents for orthopedics. In EP2268218A2 the LC-sensors are intended to measure mutual displacement of moving parts of an implant using two assemblies positioned within the living being, wherein the first assembly comprises a passive resonant circuit, inductively coupled with an ex-vivo source of RF energy. The generated output signal is dependent on the distance between the first and the second assemblies.

[0016] The patent US9662066B2 discloses a method of sensing a stimulus in vivo and an implantable sensor comprising a passive resonator circuit with a characteristic resonant frequency designed as a pair of generally parallel spirally wound unconnected conductive coils with a spacing in between.

[0017] The patent W02020223207A2 utilized the same sensor design as in US9662066B2 but applied to an intramedullary nail system and to a bone fixation device allowing monitoring the forces imparted by the bone structure and healing status of the bone structure.

[0018] The patent US2014084943A1 suggests a system for sensing strain, comprising one or more mountable sensor assembly on a portion of the implant. The sensor assembly is based on a passive resonant LC- circuit and can follow the urged movement of a portion of the implant of between 10-12 to 10-4 m.

[0019] The patent US7900518B2 discloses the concept of a microfabricated implantable passive pressure sensor using variable capacitor for tracking the pressure variation.

[0020] The presently described invention makes use of one or more so- called LC-sensors, which allow for low-cost, fully passive measurement of various implant parameters. Such LC-sensors are based on simple LC- resonant circuits and need neither batteries nor energy harvesting. The further measurement, monitoring and processing of data is achieved through a system according to the invention, comprising, among other components, on external reader comprising a coil that is inductively coupled to the LC-sensor. Integration of one or more of such LC-sensors permits multipara metric measurements of the state of the implant and allows for achieving the above-mentioned advantages.

[0021] Summary of the invention

[0022] According to one aspect of the invention, there is provided a system for measuring, monitoring and / or processing at least one physical parameter related to a smart orthopedic implant and / or the tissue of a patient’s body said smart orthopedic implant is implanted into, comprising

[0023] • at least one smart orthopedic implant according to the present invention, and

[0024] • an external reader arrangeable outside of the patient’s body, comprising at least one secondary coil and a processing unit, connectable to the at least one secondary coil, wherein the external reader is enabled to measure at least one physical parameter of the at least one electrical circuit of the smart orthopedic implant through inductive coupling of the at least one secondary coil with at least one primary coil of the electrical circuit of a smart orthopedic implant, is provided to measure the impedance of the at least one secondary coil, and is enabled to process and / or store and / or transmit the results of said measurement as measurement data.

[0025] In an embodiment, the external reader in addition comprises at least one sensor, the at least one sensor being configured to measure parameters, in particular motion parameters, body temperature, pH, blood pressure and / or 02 saturation of the patient’s body to which the external reader is arranged, wherein the external reader is enabled to process and / or store and / or transmit said parameters measured by the at least one sensor. A non-exhaustive list of sensors that can be used in this context comprises:

[0026] • MEMS motion sensors (accelerometer, gyroscope)

[0027] • Temperature sensors

[0028] • Galvanic skin response (GSR) sensors,

[0029] • pH sensors,

[0030] • photoplethysmography (PPG) sensors for blood oxygen saturation and heart rate monitoring,

[0031] • bioimpedance sensors for estimating blood pressure

[0032] • Lactate Biosensing for On-Body Sweat Analysis

[0033] • Electromyography (EMG) sensors to evaluate muscle activity and function

[0034] It is important to mention at this moment that the various elements of the external reader (i.e. the at least one secondary coil, the processing unit and / or the sensor) can be part of a single casing (or a single physical device) but that they can also be divided between two or even three different physical devices. Also, with respect to the functions of reading, measuring and interpreting data, they can be distributed between these various casings or physical devices, without departing from the spirit of the present invention. The at least one physical parameter of the at least one electrical circuit of the smart orthopedic implant measured by the external reader can in particular comprise the resonance frequency and / or the coupling coefficient and / or the Q-factor. Also, the at least one sensor can in particular by an accelerometer and / or gyroscope, more preferably a MEMS accelerometer and / or a MEMS gyroscope.

[0035] In particular, an external reader, comprising at least one secondary coil, is enabled to measure at least one physical parameter through inductive coupling of the at least one secondary coil with at least one primary coil of the at least one electrical circuit of the smart orthopedic implant. Said external reader may be arranged outside of a patient’s body, for example by fixing it to the patient’s skin using nonirritant adhesive tape or by integrating it into a belt or an elastic band, which belt or elastic band may be worn by the patient. In any way, the external reader needs to be arranged in close proximity to the at least one smart orthopedic implant, that is, close enough so that the at least one secondary coil and the at least one primary coil may be inductively coupled. Preferably, the longitudinal axis of the at least one secondary coil of the external reader and the axis of the at least one primary coil of the at least one electrical circuit of a smart orthopedic implant are oriented essentially parallel, even more preferably exactly parallel, to each other to achieve optimal inductive coupling conditions. Multiple coils may also be used to enhance coupling with the at least one primary coil.

[0036] Being inductively coupled, the at least one primary coil of the at least one electrical circuit and the at least one secondary coil of an external reader form a transformer model. The presence of the at least one primary coil within the reach of the at least one secondary coil changes the secondary coil’s impedance in the frequency range surrounding the electrical circuits resonance frequency. More specifically, it increases the real part of the impedance of the at least one secondary coil forming a local maximum on the resonance frequency. The increase of the real part of the impedance with the resonance frequency further depends on the Q-factor of the at least one electrical circuit. The more resistive losses occur in the at least one electrical circuit or surrounding tissues, the shallower is the increase of the real part of the impedance at the resonance frequency. The amplitude of the local maximum of the real part of the impedance is also dependent on the coupling coefficient between the at least one primary and the at least one secondary coil. In other words, if the coupling coefficient is constant, the local maximum goes down with smaller Q-factor. And the opposite is also true: with constant Q-factor, the local max goes also down reducing the coupling coefficient. Preferably, the processing unit analyses the distribution of the real part of the impedance within a frequency range covering the resonant frequency using data processing algorithms, and finds the frequency, where the graph reaches its local maximum, hence deduce the resonant frequency. Alternatively, or additionally, the resonant frequency can be also deduced as, for example, the point of zero crossing of the imaginary part of the impedance, or the point of zero crossing of the phase shift, or a point of a local maximum of the group delay or any other known method that use the impedance-frequency dependence to discover resonant frequencies.

[0037] The processing unit is connectable to the at least one secondary coil and is provided to measure the at least one secondary coils impedance, hence a change in said impedance as a result of the above-mentioned forces and / or environmental conditions is measurable by the processing unit and with known mechanical properties of the implant body, the forces acting upon it are derivable from said measurements. The processing unit is further enabled to process and / or store and / or transmit the results of said measurement as measurement data for which purpose the processing unit may comprise a suitable processor for controlling hardware and processes, software and / or memory for operation of the system and storage of the measurement data as well as a rechargeable battery to power these components. The measuring, monitoring and / or processing by the system may be turned off by either physically removing the external reader from the patient’s body or by suitable control means of the processing unit.

[0038] The processing unit may further record the time of measurement and include that in the processing and / or storage and / or transmitting of the measurement data so that a monitoring of the change of the measurement data over time is possible.

[0039] In an advantageous manner, the external reader is arrangeable enclosing a part of the patient’s body, preferably a limb. However, depending on the application, the external reader can also be arranged in a different manner. For example, for the spine cage, the external reader can preferably be attached to a belt that can be used to attach the external reader around of the torso of the patient. Of course, other possibilities also exist. The at least one secondary coil of the external reader is then integrated into a belt or a band, wherein the secondary coil’s windings lie along the belt or the band, which is arrangeable enclosing a part of the patient’s body. To provide ample flexibility of the belt or the band, the secondary coil’s windings may be arranged in a meandering fashion or in any other appropriate manner that allows for an extension of the windings.

[0040] To ensure optimal inductive coupling between the at least one primary coil of a smart orthopedic implant and the at least one secondary coil of the external reader, the at least one primary coil of the at least one electrical circuit of a smart orthopedic implant is preferably directed with its longitudinal axis parallel to the longitudinal axis of the band or the belt.

[0041] In an embodiment, the external reader comprises at least one sensor, preferably an accelerometer and / or gyroscope, more preferably a MEMS accelerometer and / or a MEMS gyroscope, configured to measure parameters of the patient to which the external reader is arranged to and wherein the processing unit is enabled to process and / or store and / or transmit said motion and / or physiological parameters. In doing so, further measurements regarding the movement and activity levels of a patient are obtainable and may be used to further analyse and evaluate the measurement data relating to the at least one smart orthopedic implant. In particular, the correlation between various data obtained from the at least one smart orthopedic implant and the at least one sensor can be determined and used to gain insights into important parameters relating to the patient’s body, activity or health.

[0042] In a preferred fashion, the measurement data and the motion parameters are relatable to each other so that the measured load acting onto a smart orthopedic implant may be related to the actual movement of the body part it is implanted into. For example, the shear force acting on a smart orthopedic implant, which is implanted into a joint, may be related to the actual bending of said joint or the compressive forces acting on a smart orthopedic implant, e.g. a smart spinal cage, a smart knee implant or a smart hip implant, may be related to the acceleration and / or speed of a patient during a walk or a run, or to the body position during daily activity or physical exercises. A physician or other healthcare provider may use said relatable data to monitor a patient’s activity and mobility during post-implantation treatment and may adjust the treatment procedure accordingly.

[0043] Preferably, a relation between the measurement data and the motion parameters may be used for training a machine learning algorithm. That is, a machine learning algorithm may be trained with data from a plurality of patients and the trained machine learning algorithm may then be used for evaluating and analysing the relation between measurement data and motion parameters of a further patient, find relevant patterns and may assist a physician or other healthcare provider in adjusting the treatment procedure for that further patient.

[0044] In another embodiment, the processing unit is connectable, preferably wirelessly connectable, to at least one external processing unit to further process and / or display and / or store the measurement data and / or the motion and / or physiological parameters. Said external processing unit may be a server and / or a personal device, for example a personal computer, smartphone, tablet, etc., of the patient and / or a healthcare provider. Any external processing unit may comprise dedicated software to process and / or display the measurement data and / or the motion and / or physiological parameters or it may use known software, for example data base software, note taking software, etc. for these purposes. In case of the external reader being connected to a server, multiple other external processing units may have access to the measurement data and / or motion and / or physiological parameters on said server in very well known manner, wherein storage of measurement data and / or motion and / or physiological parameters on the server or any other external processing unit may be anonymized to comply with data protection regulations. A healthcare provider is thus able to receive and subsequently evaluate measurement data and / or motion and / or physiological parameters remotely. Further, a healthcare provider may be able to communicate with the patient over the server or directly via a mobile application to inform the patient about results from evaluating the measurement data and / or motion parameters, changes in the treatment plan, etc.

[0045] In a further embodiment, the processing unit is connectable, preferably wirelessly connectable, to multiple external processing units at once to further process and / or display and / or store the measurement data and / or the motion parameters on multiple external processing units in parallel. This allows a simultaneous connection of multiple external processing units to the external reader so that, for example, a healthcare provider may view and evaluate measurement data and / or motion parameters on a first external processing unit while the patient views said measurement data and / or motion parameters on a second external processing unit and a third external processing unit stores said measurement data and / or motion parameters. In further advantageous manner, the external reader comprises the processing unit to form a single-unit external reader device, enabled to measure at least one physical parameter, preferably the resonance frequency and / or the coupling coefficient and / or the Q- factor of the at least one electrical circuit of the smart orthopedic implant, through inductive coupling of the at least one secondary coil with at least one primary coil of the electrical circuit of a smart orthopedic implant and to measure the at least one secondary coils impedance and enabled to process and / or store and / or transmit the results of said measurement as measurement data. This single-unit design ensures maximal comfort for the patient as only one device needs to be arranged outside of the patient’s body.

[0046] In a preferred embodiment, the external reader is enabled to obtain measurement data from a plurality of smart orthopedic implants at once. To achieve this, each smart orthopedic implant within the plurality of smart orthopedic implants is configurable to have a different individual resonance frequency which individual resonance frequency lies within a given range, which is detectable with the at least one secondary coil of the external reader. This way, a plurality of smart orthopedic implants may be implanted in proximity to each other, for example to replace corresponding surfaces of a joint, for example the tibia plateau and the femur condyles of the knee joint or the acetabulum and the femoral head of the hip joint, but only one external reader needs to be arranged outside the patient’s body to obtain the measurement values from said plurality of smart orthopedic implants, hence adding to the comfortability of the system for the patient and potentially increasing patient compliance.

[0047] According to another aspect, the invention relates to a smart orthopedic implant for measuring at least one physical parameter related to the smart orthopedic implant and / or the tissue it is implanted into, comprising • at least one implant body, provided to be implanted into hard or soft tissue of a patient’s body, and

[0048] • at least one electrical circuit, comprising at least one capacitor electrically connected to at least one primary coil, which electrical circuit forms part of the at least one implant body and which at least one capacitor comprises at least one first capacitor electrode and one second capacitor electrode, which capacitor electrodes are arranged essentially parallel to one another in a distance along a transversal axis, characterized in that the capacitor electrodes of the at least one capacitor are movable with respect to one another and / or the at least one primary coil and a further primary coil are movable with respect to one another, and that a force acting on the at least one implant body causes a relative motion between at least two of the first capacitor electrode, the second capacitor electrode and additional capacitor electrodes and / or between the at least one primary coil and the further primary coil, causing a change in the resonance frequency and / or coupling coefficient of the at least one electrical circuit.

[0049] The capacitor may be provided as a plate capacitor, a cylindrical capacitor, a rolled capacitor, or any other form of capacitor. The electrodes may preferably be provided in the form of even or curved capacitor plates, or cylindrical electrodes. The at least one capacitor comprises at least a first capacitor electrode and a second capacitor electrode, which capacitor electrodes are arranged essentially parallel to one another in a distance along a transversal axis. Of course, the capacitor electrodes do not necessarily need to be completely parallel, a certain inclination angle between them is also possible. Also, different other types of elements can have different, not necessarily a parallel, setup. Said transversal axis is essentially orthogonal to the capacitor electrodes and hence, if viewed in the direction of that transversal axis, the first and second capacitor electrodes overlap each other at least partially. Preferably the first capacitor electrode and the second capacitor electrode are equal in size and, in which case the maximum capacity is reachable when the capacitor electrodes overlap each other totally, i.e. the overlapping area is equal to the area of those surfaces of the capacitor electrodes that face each other. The windings of a coil, in particular the at least one primary coil, extend essentially along a longitudinal axis, which longitudinal axis may or may not be parallel to the transversal axis of the capacitor electrodes.

[0050] The at least one electrical circuit is a passive LC-resonant circuit, wherein the at least one capacitor and the least one primary coil, being electrically connected to each other, define an electric oscillator with a specific resonance frequency and form a transformer model as previously explained. That resonance frequency is dependant of the capacity of the at least one capacitor and the inductance of the at least one coil and hence changes whenever either one or both, the capacity of the at least one capacitor or the inductance of the at least one coil change. The dampening of said LC- resonant circuit is described by the so-called Q-factor, which depends on the combined capacity, inductivity and resistance of the electrical circuit. By selecting capacity, inductivity and resistance, the resonance frequency, coupling coefficient and Q-factor are configurable. Such a passive LC-resonant circuit does need neither a dedicated energy source, e.g. a battery, nor energy harvesting nor any maintenance during use. A passive LC- resonant circuit can be manufactured cost-efficiently and may furthermore be designed in a compact and small manner, which facilitates the integration of the at least one electrical circuit into the at least one implant body.

[0051] The at least one implant body is provided to be implanted into hard or soft tissue of a patient’s body and is subsequently subject to forces and environmental conditions due to its position in the body, which may include but are not limited to pressure, compressive forces, tensile forces, shear forces or torsion forces acting onto the implant body as well as temperature and / or pH. Preferably, the implant body is implanted into hard tissue a foot, a knee, a shoulder, or a hip or implanted into or as a replacement for soft tissue such as an intervertebral disc. Further preferably, the smart orthopedic implant forms part of a spinal cage, a knee endoprosthesis, a shoulder endoprosthesis, or a hip endoprosthesis, even more preferably the smart orthopedic implant is a spinal cage. In particular, the forces to which the implant body is subjected may cause a certain deformation, for example elongation, compression, twist, or etc. of the implant body. Said deformation may cause the individual components, in particular the capacitor electrodes and / or the first primary coil, which are movable with respect to each other, of the at least one electrical circuit, which forms part of the at least one implant body, to move relative to each other and thus cause a change in the resonance frequency and / or coupling coefficient of the at least one electrical circuit. With advancing integration of the implant body in the tissue, e.g. osseointegration into hard tissue as part of fusion process, the mechanical properties of the implant body may change. Subsequently, the deformation of the implant body when subjected to a force and the relative motion of the individual components of the at least one electrical circuit resulting from said deformation may change. Such a change in the implant body’s mechanical properties with integration of the implant body in the tissue may for example be achieved through openings or pores in the implant body, in which the tissue may grow into. Such opening or pores may be manufactured using additive manufacturing methods. Preferably, the implant body’s material is non-conductive and non-magnetic to exclude losses due to hysteresis and eddy currents driven by inductive coupling.

[0052] Immediately after implantation of the implant body into a tissue or, preferably, between bodies of hard tissue, e.g. vertebras, a significant amount of a load acting on the tissue and the implant body will be supported by the implant body alone. However, upon advancing integration of the implant body in the tissuenew tissue, e.g. osseous tissue, will eventually grow into and / or around the implant body. In the course of a normal integration process, preferably an osseointegration process, with advancing integration of the implant body in the tissue, a larger portion of the load acting on the tissue and the implant body will be redistributed to the newly grown tissue and the implant body will subsequently be subjected to a lesser portion of the load and thus, with advancing integration of the implant body in the tissue, the absolute deformation of the implant body at a given force may decrease. When the integration process, for example the osseointegration process (so- called fusion), comes to an end, which generally is an objective of a surgical procedure, most of the load is distributed to the newly generated tissue, while much less load is distributed to the implant body compared to a phase immediately after implantation. This allows for using the measurement data generated by the smart orthopedic implant to indicate the current fusion progress of a patient in the following or similar way: the amplitude of the force change precepted by the smart orthopedic implant during the patient’s normal daily activity according to a rehabilitation protocol in the phase immediately after implantation is supposed to be much larger than in a phase towards the end of the integration process. Eventually, the analysis of the force variation, measured with the smart orthopedic implant, using the said principle, will allow for monitoring of the state of the recovery, identifying fusion or non-fusion, making predictions on the recovery, indicating overloads, adapting the rehabilitation protocol etc.

[0053] The at least one electrical circuit forms part of the at least one implant body. Preferably, the at least one electrical circuit is provided on an exterior surface of the at least one implant body or it is integrated into the at least one implant body. Providing the at least one electrical circuit on an exterior surface of the at least one implant body enables an easier and more cost-efficient assembly of the smart orthopedic implant compared to a smart orthopedic implant with the at least one electrical circuit being integrated into the at least one implant body. Preferably, when integrated into the at least one implant body, the at least one electrical circuit does not come into contact with the hard or soft tissue the implant body is implanted into. Preferably, the at least one electrical circuit may be provided on an exterior surface of the at least one implant body or may be integrated into the at least one implant body depending on the actual implant type, e.g. spinal cage, knee endoprosthesis, shoulder endoprosthesis, hip endoprosthesis, etc., or even for the some implant type but depending on a patient’s needs, for example due to allergies, immunodeficiencies, and so on.

[0054] In preferred manner, the at least one first capacitor electrode and the at least one second capacitor electrode are movable with respect to each other in a way that the distance along an axis between the at least one first capacitor electrode and the at least one second capacitor electrode changes and / or in a way that the overlapping area of the at least one first capacitor electrode and the at least one second capacitor electrode changes and / or in a way that the inclination angle between the at least one first capacitor electrode and the at least one second capacitor electrode changes, and in that the change of the distance between the at least one first and at least one second capacitor electrode and / or the change of the overlapping area and / or the change of the inclination angle causes a change in the resonance frequency of the at least one electrical circuit.

[0055] In particular tensile and / or compressive forces lead to a compression or elongation of the at least one implant body, which may increase or decrease the distance between the at least one first capacitor electrode and the at least one second capacitor electrode, thus changing the capacity of the capacitor and subsequently the resonance frequency of the at least one electrical circuit. Shear forces and / or torsion forces acting on the at least one implant body, however, may lead to a relative motion of the at least one first capacitor electrode with respect to the at least one second capacitor electrode in a direction essentially parallel to the surfaces of the capacitor electrodes that face each other, which may change the overlapping area of the at least one first and the at least one second capacitor electrodes, thus also causing a change in the resonance frequency of the at least one electrical circuit.

[0056] In a preferred embodiment, the smart orthopedic implant comprises at least two electrical circuits with at least one capacitor and at least one coil each, wherein the capacitor electrodes of the capacitors of at least one electrical circuit are essentially orthogonal to the capacitor electrodes of the capacitors of at least one other electrical circuit. In this way, individual components of a force acting obliquely with respect to either of the capacitor electrodes may be measured, wherein the individual components of said force act along the axes of the capacitors of the at least two electrical circuits. The capacitor electrodes of at least one electrical circuit may also be oriented in any angle with respect to the capacitor electrodes of the capacitors of at least one other electrical circuit and the individual components of a force acting along the axis of either of the capacitors of the at least two electrical circuits may be derived from the measured at least one physical parameter of the at least two electrical circuits. Of course, in a different embodiment, the capacitor electrodes of the at least one capacitor of at least one electrical circuit can be essentially parallel to the capacitor electrodes of the at least one capacitor of at least one other electrical circuit.

[0057] In equally preferred manner, the smart orthopedic implant comprises at least one electrical circuit with at least one first primary coil and at least one second primary coil, which first and second primary coils are movable with respect to each other, and in that this relative movement of the first primary coil and the second primary coil with respect to each other causes a change in the coupling coefficient of the at least one electrical circuit. Since the coupling coefficient depends on the distance between the first primary coil and the second primary coil and on their relative orientation, measuring of the coupling coefficient allows to observe a change in distance between the first primary coil and the second primary coil while in constant relative orientation or a change in their relative orientation while the distance between the first primary coil and the second primary coil remains constant. In parallel, the at least one capacitor of the at least one electrical circuit may allow to measure a deformation of the implant body as described above so that with a single electrical circuit, multiple parameters are measurable at once. According to another embodiment, the implant body comprises multiple layers, wherein the at least one first capacitor electrode and the at least one second capacitor electrode are arrangeable in different layers and / or wherein the windings of the at least one primary coil are arrangeable in different layers.

[0058] In advantageous manner, the windings of the at least one primary coil are essentially circumferential to the at least one first capacitor electrode and / or the at least one second capacitor electrode which increase the coupling, that is, the area which is enclosed by the coil windings and thus improves the inductive coupling of the at least one primary coil with a second primary coil and / or a secondary coil. However, any metallic object within the coupling area may adversely affect the inductive coupling, so it may as well be beneficial to arrange the at least one first capacitor electrode and the at least one second capacitor electrode outside of the coupling area of the at least one primary coil.

[0059] In another embodiment, the at least one electrical circuit of the smart orthopedic implant comprises at least one electrical component whose electrical properties, preferably its resistance and / or conductivity and / or inductivity, vary according to conditions, preferably temperature and / or pH, to which said electrical component is subjected to, and which variation in the electrical properties of the at least one electrical component causes a change in the resonance frequency and / or the coupling coefficient and / or the Q-factor of the at least one electrical circuit. Electrical components whose electrical properties vary according to conditions to which said electrical component is subjected to may include, for example, resistive temperature sensing elements, capacitive pH sensing elements or impedance-based pH sensing elements. Since in particular the Q-factor depends on the combined capacity, inductivity and resistance of the at least one electrical circuit, integration of such an electrical component allows for observing said conditions, for example temperature and / or pH, by measuring a change in the Q-factor. In yet another embodiment, the electrical circuit comprises at least a first electrical sub-circuit with at least one primary coil, at least a first capacitor electrode and a second capacitor electrode and it comprises a second electrical sub-circuit with at least one primary coil, at least a first capacitor electrode and a second capacitor electrode and the first capacitor electrode of the first electrical sub-circuit and the first capacitor electrode of the second electrical sub-circuit form a first capacitor and the second capacitor electrode of the first electrical subcircuit and the second capacitor electrode of the second electrical subcircuit form a second capacitor, and the capacitor electrodes are movable with respect to one another, and a force acting on the at least one implant body causes a relative motion between at least two of the capacitor electrodes and / or between the primary coils, causing a change in the resonance frequency of the electrical circuit. The electrical circuit may further comprise one or more additional electrical sub-circuits and / or the first, second or additional electrical sub-circuits may comprise additional capacitors electrodes and / or primary coils, wherein a relative motion between a capacitor electrode of the first, second or an additional electrical sub-circuit and a capacitor electrode of any other of the first, second or additional sub-circuit or a relative motion between a primary coil of the first, second or additional electrical sub-circuit and a primary coil of any other of the first, second or another additional sub-circuit also cause a change in the resonance frequency of the electrical circuit.

[0060] The first and second electrical sub-circuits are electrically isolated from each other by a dielectric layer between the first capacitor electrode of the first electrical sub-circuit and the first capacitor electrode of the second sub-circuit and between the second capacitor electrode of the first electrical sub-circuit and the second capacitor electrode of the second sub-circuit. Preferably, said dielectric layer is a compressible dielectric layer. Even more preferably, said dielectric layer has a thickness in a range of 5 m to 2 mm. Preferably, the magnetic fields of the at least one primary coil of the first electrical sub-circuit and of the at least one primary coil of the second electrical sub-circuit are aligned with each other in such a way that they form a common magnetic field. Even more preferably, the effective inductance of said common magnetic field is at least equal to the sum of the individual inductances of the primary coils themselves. Insufficient alignment of the magnetic fields of the at least one primary coil of the first electrical sub-circuit and of the at least one primary coil of the second electrical sub-circuit may cause a reduction of the effective inductance of the common magnetic field, which increases the resonance frequency of the electrical circuit and thus may impair the functionality of the smart orthopedic implant.

[0061] The first and second electrical sub-circuits may be manufactured using known production processes, such as a standard flex PCB process. The first and second electrical sub-circuits may preferably be manufactured in one production process or in separate production processes, i.e. the first electrical sub-circuit may be manufactured in a first production process and the second electrical sub-circuit may be manufactured in a second production process and the first and second electrical sub-circuits are arranged with a dielectric layer between them. The electrical circuit may thus be manufactured in a simple and cost-efficient manner as no complex assembly techniques for electrically connecting the first and second electrical sub-circuits are required. The inductance and capacity of the first and second electrical sub-circuits are customizable and may be adapted to particular implant types. The electrical circuit may then be arranged on or in an implant body to form a smart orthopedic implant, preferably attached to the outer surface of an implant body or inserted into a slot provided in an implant body.

[0062] For an easy assembly of a smart orthopedic implant, an implant body may comprise a first part and a second part and, in a first step, the first electrical sub-circuit may be arranged on said first part and the second electrical sub-circuit may be arranged on said second part. The first and second parts of the implant body may then, in a second step, be assembled with a dielectric layer between them to form the smart orthopedic implant. Alternatively, the first and second electrical sub-circuits may, in a first step, be arranged with a dielectric layer between and, in a second step, the first part of the implant body may be arranged at the first electrical sub-circuit and the second part of the implant body may be arranged at the second electrical sub-circuit to form the smart orthopedic implant. Further alternatively, the first and second electrical sub-circuits may, in a first step, be arranged with a dielectric layer between and, in a second step, an implant body may be manufacturing using a moulding process, such as injection moulding, and the electrical circuit forms part of the implant body during the moulding process.

[0063] In a further preferable embodiment, the at least one primary coil is elastically deformable and a force acting on the at least one implant body causes an elastic deformation of the at least one primary coil, causing a change in the resonance frequency and / or coupling coefficient of the at least one electrical circuit.

[0064] The at least one primary coil comprises windings, which extend in a longitudinal direction. A force acting on the at least one implant body may act along that longitudinal direction, perpendicular to it or oblique to it.

[0065] An elastic deformation of the at least one primary coil may result in a relative displacement between the windings of the at least one primary coil, for example it may result in a change in distance between windings of the at least one primary coil in the longitudinal direction and / or it may result in a shift of windings relative to each other perpendicular to the longitudinal direction.

[0066] In a further aspect, the invention also relates to a method for measuring, monitoring and / or processing at least one physical parameter related to a smart orthopedic implant according to this invention and / or the tissue said smart orthopedic implant is implanted into using a system according to the invention.

[0067] Brief description of the drawings

[0068] For a more complete understanding of the invention and the advantages thereof, exemplary embodiments of the invention are explained in the following description with reference to the accompanying figures, in which the same reference characters designate the same parts and in which:

[0069] Figure 1 shows an electrical circuit according to the invention subject to a compressive force along the transversal axis,

[0070] Figure 2 shows an electrical circuit according to the invention subject to a shear force perpendicular to the transversal axis,

[0071] Figure 3 shows an electrical circuit according to the invention subject to a torsion force about the transversal axis,

[0072] Figure 4A illustrates a primary coil and a secondary coil with a first distance between them,

[0073] Figure 4B illustrates a primary coil and a secondary coil with a second distance between them,

[0074] Figure 4C illustrates a primary coil and a secondary coil with their longitudinal axes being concentric,

[0075] Figure 4D illustrates a primary coil and a secondary coil, wherein the primary coil is rotated with respect to the secondary coil by a first angle, Figure 4E illustrates a primary coil and a secondary coil, wherein the primary coil is rotated with respect to the secondary coil by a second angle,

[0076] Figure 5 shows a cross-section of a smart orthopedic implant with four electrical circuits according to an embodiment of the invention,

[0077] Figure 6A illustrates a first way of arranging an external reader according to one embodiment of the invention,

[0078] Figure 6B illustrates a second way of arranging an external reader according to an embodiment of the invention,

[0079] Figure 7 shows a cross-section of a knee joint with two smart orthopedic implants according to an embodiment of the invention,

[0080] Figure 8 shows a cross-section of a foot with a system according to an embodiment of the invention,

[0081] Figure 9 shows a cross-section of a hip joint with a system according to an embodiment of the invention,

[0082] Figure 10A illustrates a spine segment with a smart orthopedic implant according to an embodiment of the invention,

[0083] Figure 1 OB illustrates an exploded view of a smart orthopedic implant according to an embodiment of the invention,

[0084] Figure 1 1 A illustrates an electrical circuit with a first and a second electrical sub-circuit according to an embodiment of the invention, Figure 1 1 B illustrates a cross-section of an electrical circuit with a first and a second electrical sub-circuit according to an embodiment of the invention, and

[0085] Figure 12 illustrates a spine and torso with a system according to an embodiment of the invention.

[0086] Detailed description of the illustrated embodiments

[0087] Figure 1 illustrates a basic version of an electrical circuit 12 comprising a capacitor 13 electrically conducive connected to a primary coil 14 which electrical circuit 12 is part of a smart orthopedic implant according to an embodiment of the invention (not shown). The first capacitor electrode 13a and the second capacitor electrode 13b are arranged essentially parallel to one another in a distance along the transversal axis 15, wherein that distance decreases when the smart orthopedic implant is subjected to a compressive force acting parallel or along the transversal axis 15. Vice versa, when the smart orthopedic implant is subjected to a tensile force acting parallel or along the transversal axis 15, the distance between the first capacitor electrode 13a and the second capacitor electrode 13b increase. Subsequently, the resonance frequency of the electrical circuit 12 changes.

[0088] Figure 2 shows another basic version of an electrical circuit 12 comprising a capacitor 13 electrically conducive connected to a primary coil 14 which electrical circuit 12 is part of a smart orthopedic implant according to an embodiment of the invention (not shown). In the present example, the first capacitor electrode 13a and the second capacitor electrode 13b are equal in size and overlap each other completely in their unloaded state (not shown). When the implant body is subjected to a shear force perpendicular to the transversal axis 15 as shown in figure 2, the first capacitor electrode 13a and the second capacitor electrode 13b move relative to each other and the overlapping area is reduced, thus reducing the capacity of the capacitor 13 and changing the resonance frequency of the electrical circuit 12.

[0089] As is shown in Figure 3, a torsion force acting on the smart orthopedic implant (not shown) may lead to a relative torsion between the first capacitor electrode 13a and the second capacitor electrode 13b which relative torsion decreases the overlapping area 16 and thus the capacity of the capacitor 13.

[0090] Figures 4A and 4B schematically depict the functionality of the invention according to an embodiment, wherein a primary coil 14 and a secondary coil 22 are inductively coupled to each other and the coupling coefficient depends on the distance between the primary coil 14 with a first longitudinal axis 18 and the secondary coil 22 with a second longitudinal axis 28, which first longitudinal axis 18 and second longitudinal axis 28 are coaxial to each other and which primary coil 14 is part of an electrical circuit (not shown) and which secondary coil 22 forms part of an external reader 21 . In a first position as shown in figure 4A, said coupling coefficient takes on a first value whereas upon in a second position, which is shown in figure 4B, and wherein the distance between the primary coil 14 and the secondary coil 22 in that second position is larger than in the first position, the coupling coefficient takes on a second value, which second value is smaller than the first value.

[0091] From figures 4C, 4D and 4E the dependency of the coupling coefficient on the relative orientation of the primary coil 14 with respect to the secondary coil 22 can be seen. In a first orientation (Figure 4C), wherein the longitudinal axis 18 of the primary coil 14 and the longitudinal axis 28 of the secondary coil 22 are essentially coaxial to each other, the coupling coefficient takes on its maximum value. When the primary coil 14 is moved to a second position (Figure 4D), wherein the longitudinal axis 18 of the primary coil 14 and the longitudinal axis 28 of the secondary coil 22 enclose an angle between 0° and 90°, the coupling coefficient decreases. In the third position (Figure 4E), wherein the longitudinal axis 18 of the primary coil 14 and the longitudinal axis 28 of the secondary coil 22 enclose an angle of 90°, the coupling coefficient becomes zero. Continuing the rotation of the primary coil 14 relative to the secondary coil 22, the coupling coefficient increases again until it again reaches its maximum value when the longitudinal axis 18 of the primary coil 14 and the longitudinal axis 28 of the secondary coil 22 are essentially coaxial to each other again.

[0092] In figure 5, a schematic cross-section of a smart orthopedic implant 10 with a total of four electrical circuits 12, 12’, 12”, 12” ’ is depicted. The individual electrical circuits 12, 12’, 12”, 12’ ” facilitate measurement of forces acting on individual areas of said smart orthopedic implant 10. By configuring the electrical circuits 12, 12’, 12”, 12’ ” to have individual resonance frequencies as described earlier, changes in resonance frequency, coupling coefficient and / or Q-factor are receivable using a single external reader according to the invention, however due to the individual configurations, the received values are relatable to the individual electrical circuits 12, 12’, 12”, 12’ ” and thus further analysis of the loading of said smart orthopedic implant 10 is possible.

[0093] From figure 6A and 6B, ways of arranging a secondary coil 22 of an external reader (not shown) can be seen. Figure 6A shows the secondary coil 22 being attached to a band 24, which band may be worn around a part of a patient’s body, and which secondary coil 22 has a longitudinal axis 29 which is essentially perpendicular to the longitudinal axis 33 of said part of a patient’s body and hence the longitudinal axis 29 would also be perpendicular to the skin of said part of a patient’s body (not shown). In figure 6B it can be seen that the secondary coil 22 is integrated into the band 24 so that the longitudinal axis 29 of the secondary coil 22 and the longitudinal axis 33 of the part of a patient’s body are coaxial.

[0094] Figure 7 illustrates a cross-section of a total knee prosthesis with a system (20) according to an embodiment of the invention, comprising two smart orthopedic implants 10, 10’, an external reader 21 and a processing unit (not shown). The external reader 21 comprises a secondary coil 22, which is integrated into a band 24 with the secondary coil’s 22 windings lying along the band and which band 24 is arranged enclosing the upper leg 6a of a patient. Upon flexion of the knee joint, the first smart orthopedic implant 10, which is arranged to the femur 2a, is tilted by an angle a relative to the tibia 2b and thus relative to the second smart orthopedic implant 10’ and the external reader 21 , hence, causing a measurable change in the coupling coefficient between the primary coil 14 of the first smart orthopedic implant 10 and the secondary coil 22 of the external reader 21 . Independent from or in addition to said bending, the knee joint may be subjected to compressive or tensile forces parallel to the transversal axis 15’, which may increase or decrease the distance between the capacitor electrodes of the capacitor 13 of the first smart orthopedic implant 10 and / or the distance between the capacitor electrodes of the capacitor 13’ of the second smart orthopedic implant 10’, thus causing a measurable change in the resonance frequency of the electrical circuit (not shown) of the first smart orthopedic implant 10 and / or the electrical circuit (not shown) of the second smart orthopedic implant 10’ . Also, the illustrated knee joint may be subjected to shear forces perpendicular to the transversal axis 15’ or to torsion forces about the transversal axis 15’, which may cause a change in the overlapping area of the capacitor electrodes of the capacitor 13 of the first smart orthopedic implant 10 and / or the overlapping area of the capacitor electrodes of the capacitor 13’ of the second smart orthopedic implant 10’ , thus causing a measurable change in the resonance frequency of the electrical circuit of the first smart orthopedic implant 10 and / or the electrical circuit of the second smart orthopedic implant 10’.

[0095] In figure 8 a system 20 comprising a smart orthopedic implant 10 and an external reader 21 and a processing unit (not shown) according to an embodiment of the invention implanted into a foot of a patient is shown. As illustrated, the smart orthopedic implant 10 is implanted into a bone, with a distal part 4b of the bone and a proximal part 4a of the bone being in contact with the smart orthopedic implant 10. Compression and / or tension parallel to the transversal axis 15 may increase or decrease the distance between the capacitor electrodes 13a, 13b and thus cause a measurable change in the resonance frequency of the electrical circuit (not shown) of the smart orthopedic implant 10. However, the smart orthopedic implant 10 as shown also comprises a first primary coil 14a and a second primary coil 14b and the implant body 1 1 is designed in a wedge-like shape so that compression and / or tension parallel to the transversal axis 15 may also change the relative orientation of the first primary coil 14a and the second primary coil 14b with respect to the secondary coil 22, thus causing a measurable change in the coupling coefficient between the primary coils 14a, 14b and the secondary coil 22 of the external reader 21 . The secondary coil 22 of the external reader 21 encloses the foot of the patient and may be integrated into a band, a sock or a shoe.

[0096] Figure 9 shows another embodiment of the system 20 according to the invention comprising a first and a second smart orthopedic implant 10, 10’ forming part of a total hip prosthesis, an external reader 21 being arranged to the thigh 5 of a patient and a processing unit (not shown). The first smart orthopedic implant 10, comprising multiple electrical circuits 12, 12”, 12” ’, is implanted into the acetabulum 3a of a patient and the second smart orthopedic implant 10’, comprising an electrical circuit 12’, forms part of the femoral part 7 of the total hip prosthesis and is implanted into the femur (not shown) of a patient. In particular the capacitor of the second smart orthopedic implant 10’ is arranged with its capacitor electrodes parallel to the transversal axis 15’ and enables the system 20 to measure compressive forces acting perpendicular to the transversal axis 15’ in the already described fashion.

[0097] Spherical motion of the femur relative to the acetabulum 3a causes a change in the relative orientation of the primary coil 14’ of the second smart orthopedic implant 10’ with respect to the primary coils 14, 14”, 14’ ” of the first smart orthopedic implant 10 thus causing a measurable change in the coupling coefficient between the primary coil 14’ and the primary coils 14, 14” and 14”’ and thus a change in the impedance of the secondary coil 22. The electrical circuits 12, 12” and 12’” have different resonance frequencies and, depending on the relative orientation of the primary coils 14, 14” and 14’ ” with respect to the primary coil 14’, one of these resonance frequencies is detectable as a dominant resonant frequency. That is, in the example as shown in figure 9 with the primary coils 14’ and 14 aligned along the transversal axis 15’, the resonance frequency of the electrical circuit 12 will be detectable as a dominant resonant frequency.

[0098] For an intervertebral smart orthopedic implant 10 as shown in figure 10A (a so-called cage or artificial intervertebral disk) the parameters of major interest are the compression and / or shear forces and osseointegration rate. The intervertebral smart orthopedic implant 10 is located between vertebrates 8a, 8b and its transversal axis 15 is essentially coaxial with the longitudinal axis of the spine in the area of the vertebrates 8a, 8b. A compression of the spine may lead to a compressive force acting along or parallel to the transversal axis 15 thus reducing the distance between the capacitor electrodes of the capacitor 13 and causing a measurable change in the resonance frequency of the electrical circuit (not shown) of the smart orthopedic implant 10. Likewise, shear forces acting perpendicular to the transversal axis 15 cause a change in the overlapping area of the capacitor electrodes of the capacitor 13 and thus cause a measurable change in the resonance frequency of the electrical circuit (not shown) of the smart orthopedic implant 10. Such an intervertebral smart orthopedic implant 10 may comprise multiple electrical circuits as explained along with figure 5.

[0099] Figure 10B further shows an exploded view of another intervertebral smart orthopedic implant 10’ comprising an implant body 1 1 ’ with a first part I la’ and a second part 1 1 b’.

[0100] A first electrical circuit 12a and a second electrical circuit 12b are arranged between the first and second parts I l a’, 1 1 b’ and the first and second parts I l a’, 1 1 b’ may be joined with the electrical circuits 12a, 12b in between by inserting pins 94 of the first part I l a’ into corresponding openings 95 of the second part 1 1 b’.

[0101] The first part I l a’ has recesses 96a and the second part 1 1 b’ has matching recesses 96b and the first and second electrical circuits 12a, 12b have matching recesses 96c. The recesses 96a, 96b, 96c provide space for tissue ingrowth and / or to be filled with a bone graft during implantation of the intervertebral smart orthopedic implant 10’. The first part 1 la’ further comprises notches 97 on an exterior surface for, upon implantation, providing a mechanical interlock between the first part and subsequent tissue (not shown) . The second part 1 1 b’ also comprises such notches (not shown) an exterior surface.

[0102] The first and second electrical circuits 12a, 12b are arranged in a plane mirrored fashion through a sagittal plane of the intervertebral smart orthopedic implant 10’. This mirrored arrangement enables, in particular, an improved measurement of eccentric compression forces acting on the intervertebral smart orthopedic implant 10’, i.e. forces acting of the intervertebral smart orthopedic implant 10’ upon bending of the spine it is implanted into or upon an imbalanced loading of the spine. A physiotherapist or another medical practitioner may adjust a rehabilitation protocol based on a measurement of such eccentric compression forces.

[0103] An electrical circuit 12 as shown in figure 1 1 A comprises a first electrical sub-circuit 101 and a second electrical sub-circuit 102. The first electrical sub-circuit 101 comprises a primary coil 1 14, a first capacitor electrode 1 13a and a second capacitor electrode 1 13b and the second electrical sub-circuit 102 comprises a primary coil 1 14’, a first capacitor electrode 1 13a’ and a second capacitor electrode 1 13b’.

[0104] A first dielectric layer (not shown) is arranged between the first capacitor electrodes 1 13a, 1 13a’ and a second dielectric layer (not shown) is arranged between the second capacitor electrodes 1 13b, 1 13b’. Thus, the first capacitor electrode 1 13a of the first electrical subcircuit 101 and the first capacitor electrode 1 13a’ of the second electrical sub-circuit 102 form a first capacitor 1 13 and the second capacitor electrode 1 13b of the first electrical sub-circuit 101 and the second capacitor electrode 1 13b’ of the second electrical sub-circuit 102 form a second capacitor 1 13’. The first and second dielectric layers may however also be a single continuous dielectric layer.

[0105] The distance between the capacitor electrodes 1 13a and 1 13a’ or the distance between the capacitor electrodes 1 13b and 1 13b’ decreases upon a compressive force acting in a direction essentially perpendicular to the capacitor electrodes. Accordingly, said distances increases upon a tensile force acting in a direction essentially perpendicular to the capacitor electrodes. Any change of either or both of these distances results in a change of the resonance frequency of the electrical circuit 12.

[0106] Figure 1 1 B shows the electrical circuit 12 of figure 1 1 A in a cross-section.

[0107] A compressible dielectric 1 15, comprising a first dielectric layer 1 15a and a second dielectric layer 1 15b, is arranged between the first and second capacitors 1 13, 1 13’. The first and second capacitor electrodes 1 13a, 1 13b of the first electrical sub-circuit 101 are arranged with a distance between them, which distance forms a first gap 1 17. The first and second capacitor electrodes 1 13a’, 1 13b’ of the second electrical sub-circuit 102 are also arranged with a distance between them, which distance forms a second gap 1 17.

[0108] In the present example, the first and second electrical subcircuits 101 , 102 are identical in shape and composition and are arranged at opposing sides of the compressible dielectric 1 15. It is however also possible to provide first and second electrical sub-circuits of different shape and / or composition. Figure 12 illustrates a patient’s torso 51 and a section of a spine 52 with the intervertebral smart orthopedic implant 10 located between the vertebrates 8a, 8b as already shown in and explained with reference to figure 10.

[0109] Figure 12 further illustrates an external reader 21 which is attached to a band 24’, which band 24’ is arranged, i.e. worn, around the torso 51 of a patient. The external reader 21 on the band 24’ is worn in close proximity to the smart orthopedic implant 10 for facilitating an inductive coupling of the at least one secondary coil (not shown in figure 12) with the at least one primary coil (not shown in figure 12) of the smart orthopedic implant 10.

[0110] The external reader 21 further comprises a sensor provided as an accelerometer (not shown) for measuring an acceleration of the external reader 21 in any spatial direction, which, when the external reader is arranged at the torso 51 , corresponds to the respective acceleration of the torso 51 , i.e. of the patient. The processing unit and the accelerometer are arranged in a single casing 53 of the external reader 21 . The at least one secondary coil is arranged in the band 24’ as explained with reference to figure 6B already, however, the at least one secondary coil may alternatively also be arranged in or at the casing 53.

[0111] The acceleration measured by the accelerometer is relatable to, for example, the compression of the spine 52 as measured through the smart orthopedic implant 10, and a physician or other healthcare provider may use the relation of said data to monitor the patient’s activity and mobility during post-implantation treatment and may adjust a treatment procedure accordingly.

[0112] Should the patient require a further smart orthopedic implant (not shown) arranged, for example, between the vertebra 8a and a further vertebra 8c, the external reader 21 is enabled to obtain measurement data from the smart orthopedic implant 10 and the further smart orthopedic implant at once.

Claims

34Claims1 . A smart orthopedic implant ( 10) for measuring at least one physical parameter related to the smart orthopedic implant (10) and / or the tissue of a patient’s body it is implanted into comprising• at least one implant body (1 1 ), provided to be implanted into hard or soft tissue of a patient’s body, and• at least one electrical circuit (12), comprising at least one capacitor (13) electrically conducive connected to at least one primary coil (14), which electrical circuit (12) forms part of the at least one implant body (1 1 ) and which at least one capacitor (13) comprises at least one first capacitor electrode ( 13a) and at least one second capacitor electrode (13b), which capacitor electrodes (13a, 13b) are arranged essentially parallel to one another in a distance along a transversal axis (15), characterized in that the at least one electrical circuit (12) is a passive LC-resonant circuit, and the capacitor electrodes ( 13a, 13b) of the at least one capacitor ( 13) are movable with respect to one another and / or the at least one primary coil (14) and a further primary coil are movable with respect to one another, and that a force acting on the at least one implant body (1 1 ) causes a relative motion between at least two of the at least one first capacitor electrode (13a), the at least one second capacitor electrode (13b) and additional capacitor electrodes and / or between the at least one primary coil (14) and the further primary coil, causing a change in the resonance frequency and / or coupling coefficient of the at least one electrical circuit (12).

352. A smart orthopedic implant (10) according to claim 1 , characterized in that the at least one first capacitor electrode (13a) and the at least one second capacitor electrode (13b) are movable with respect to each other in a way, that the distance along a transversal axis (15) between the at least one first capacitor electrode (13a) and the at least one second capacitor electrode ( 13b) changes and / or in a way, that the overlapping area (16) of the at least one first capacitor electrode ( 13a) and the at least one second capacitor electrode ( 13b) changes, and / or in a way that the inclination angle between the at least one first capacitor electrode ( 13a) and the at least one second capacitor electrode ( 13b) changes, and in that the change of the distance between the at least one first and at least one second capacitor electrode ( 13a, 13b) and / or the change of the overlapping area ( 16) and / or the change of the inclination angle causes a change in the resonance frequency of the at least one electrical circuit (12).

3. A smart orthopedic implant (10) according to claim 1 or 2, characterized in that it comprises at least two electrical circuits (12, 12’) with at least one capacitor (13, 13’) and at least one primary coil (14, 14’) each, wherein the capacitor electrodes (13a, 13b) of the at least one capacitor (13) of at least one electrical circuit (12) are essentially orthogonal to the capacitor electrodes (13a’, 13b’) of the at least one capacitor (13’) of at least one other electrical circuit (12’).

4. A smart orthopedic implant (10) according to claim 1 or 2, characterized in that it comprises at least two electrical circuits (12, 12’) with at least one capacitor (13, 13’) and at least one primary coil (14, 14’) each, wherein the capacitor electrodes (13a, 13b) of the at least one capacitor (13) of at least one electrical circuit ( 12) are essentially parallel to the capacitor electrodes (13a’, 13b’) of the at least one capacitor (13’) of at least one other electrical circuit (12’).

5. A smart orthopedic implant (10) according to one of the claims 1 , 2 or 4 , characterized in that the electrical circuit (12) comprises at least a first electrical sub-circuit (101 ) with at least one primary coil(1 14), at least a first capacitor electrode (1 13a) and a second capacitor electrode (1 13b) and it comprises a second electrical sub-circuit (102) with at least one primary coil (1 14’), at least a first capacitor electrode (1 13a’) and a second capacitor electrode (1 13b’), and wherein the first capacitor electrode ( 1 13a) of the first electrical sub-circuit (101 ) and the first capacitor electrode (1 13a’) of the second electrical sub-circuit (102) form a first capacitor (1 13) and the second capacitor electrode (1 13b) of the first electrical sub-circuit (101 ) and the second capacitor electrode (1 13b’) of the second electrical sub-circuit (102) form a second capacitor (1 13’), and wherein the capacitor electrodes (1 13a, 1 13b, 1 13a’, 1 13b’) are movable with respect to one another, and wherein a force acting on the at least one implant body (1 1 ) causes a relative motion between at least two of the capacitor electrodes (1 13a, 1 13b, 1 13a’, 1 13b’) and / or between the primary coils (1 14, 1 14’), causing a change in the resonance frequency of the electrical circuit (12).

6. A smart orthopedic implant (10) according to any one of the preceding claims, characterized in that it comprises at least one electrical circuit (12) with at least one first primary coil (14) and one second primary coil (14’), which first and second primary coils (14, 14’) are movable with respect to each other, and in that this relative movement of the first primary coil (14) and the second primary coil (14’) with respect to each other causes a change in the coupling coefficient of the at least one electrical circuit (12).

7. A smart orthopedic implant ( 10) according to any of the preceding claims, characterized in that the implant body (1 1 ) comprises multiple layers, wherein the at least one first capacitor electrode (13a) and the at least one second capacitor electrode (13b) are arrangeable in different layers and / or wherein the windings of the at least one primary coil (14) are arrangeable in different layers.

8. A smart orthopedic implant (10) according to any one of the preceding claims, characterized in that the windings of the at least one primary coil (14) are essentially circumferential to the at least one firstcapacitor electrode ( 13a) and / or the at least one second capacitor electrode (13b).

9. A smart orthopedic implant (10) according to any one of the preceding claims, characterized in that the at least one electrical circuit (12) comprises at least one electrical component (17) whose electrical properties, preferably its resistance and / or conductivity and / or inductivity, vary according to conditions, preferably temperature and / or pH, to which said electrical component (17) is subjected to, and which variation in the electrical properties of the at least one electrical component (17) causes a change in the resonance frequency and / or the coupling coefficient and / or the Q-factor of the at least one electrical circuit (12).

10. A smart orthopedic implant ( 10) according to any one of the preceding claims, characterized in that the at least one primary coil (14) is elastically deformable and a force acting on the at least one implant body (1 1 ) causes an elastic deformation of the at least one primary coil (14), causing a change in the resonance frequency and / or coupling coefficient of the at least one electrical circuit (12).1 1 . A system (20) for measuring, monitoring and / or processing at least one physical parameter related to a smart orthopedic implant and / or the tissue of a patient’s body said smart orthopedic implant is implanted into, comprising• at least one smart orthopedic implant (10) according to any of the claims 1 to 10, and• an external reader (21 ) arrangeable outside of the patient’s body, comprising at least one secondary coil (22) and a processing unit (23), connectable to the at least one secondary coil (22), wherein the external reader (21 )38 is enabled to measure at least one physical parameter of the at least one electrical circuit (12) of the smart orthopedic implant ( 10) through inductive coupling of the at least one secondary coil (22) with at least one primary coil (14) of the electrical circuit (12) of a smart orthopedic implant (10), is provided to measure the impedance of the at least one secondary coil (22), and is enabled to process and / or store and / or transmit the results of said measurement as measurement data.

12. A system (20) according to claim 1 1 , characterized in that the external reader (21 ) in addition comprises at least one sensor (24), the at least one sensor (24) being configured to measure parameters, in particular motion parameters, body temperature, PH, blood pressure and / or 02 saturation of the patient’s body to which the external reader (21 ) is arranged, wherein the external reader (21 ) is enabled to process and / or store and / or transmit said parameters measured by the at least one sensor (24).

13. A system (20) according to claim 1 1 or claim 12, characterized in that the at least one physical parameter of the at least one electrical circuit (12) of the smart orthopedic implant ( 10) measured by the external reader (21 ) comprises the resonance frequency and / or the coupling coefficient and / or the Q-factor.

14. A system (20) according to any one of the claims 1 1 to 13, characterized in that the least one sensor (24) is an accelerometer and / or gyroscope, more preferably a MEMS accelerometer and / or a MEMS gyroscope.

15. A system (20) according to any one of the claims 1 1 to 14, characterized in that the external reader is arrangeable enclosing a part of the patient’s body, preferably a limb.3916. A system (20) according to any one of the claims 1 1 to 15, characterized in that the measurement data and the motion parameters are relatable to each other.

17. A system (20) according to any one of the claims 1 1 to 16, characterized in that the processing unit (23) is connectable, preferably wirelessly connectable, to at least one external processing unit (30) to further process and / or display and / or store the measurement data and / or the motion parameters.

18. A system (20) according to claim 17, characterized in that the external processing unit (30) is a mobile phone, smartwatch, gaming console, tablet, desktop computer or a similar device.

19. A system (20) according to claim 17 or claim 18, characterized in that the processing unit (23) is connectable, preferably wirelessly connectable, to multiple external processing units at once to further process and / or display and / or store the measurement data and / or the motion parameters on multiple external processing units in parallel.

20. A system (20) according to any one of the claims 1 1 to 19, characterized in that the secondary coil (22) and / or the processing unit (23) and / or the sensor (24) are arranged in at least two different casings.21 . A system (20) according to any one of the claims 1 1 to 20, characterized in that an external reader (21 ) is enabled to obtain measurement data from a plurality of smart orthopedic implants at once.

22. A method for measuring, monitoring and / or processing at least one physical parameter using the system according to any one of the claims 1 1 to 21 , wherein the at least one physical parameter is related to the smart implant according to any one of the claims 1 to 10 and / or the tissue said smart implant is implanted into.

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