Embedded device and charging module for supplying power to the embedded device

Abstract

An implantable device for monitoring the joint environment within a joint corresponding to a joint body, such as a bone or a prosthetic joint component. The implantable device comprises a sensor module configured to measure data indicative of at least one parameter of the joint environment within the joint corresponding to the joint body, a communication unit operatively coupled to the sensor module and configured to transmit the measured data to an external device, and a rechargeable battery configured to supply power to the sensor module and the communication unit. The sensor module, the power supply and the communication unit are housed within a capsule, the capsule is removably mounted within an opening of the joint body, and when the capsule is removably mounted within the opening of the joint body, the sensor module is configured to monitor at least one parameter of the joint environment within the joint.

Description

Technical Field

[0001] The present invention relates to an implantable device, and more particularly, but not limited thereto, to an implantable device comprising a sensor module for monitoring a joint environment such as an intra-articular joint environment.

Background Art

[0002] Knee osteoarthritis (OA) is a problem that commonly affects middle-aged and elderly people, and total knee replacement (also known as total knee arthroplasty, TKR) is often a treatment option for patients with severe OA and significant symptoms. Although generally successful, one in five TKR patients reports being "dissatisfied with the outcome" without an obvious cause. A significant proportion of these could have been avoided or detected earlier to improve the outcome. As with hip replacement, warnings about dangerous positions of the device can increase awareness and thus awareness of the risk of dislocation (about 3% of hip replacements) and / or implant malfunctions and loosening.

[0003] As life expectancy increases and the preference for an active lifestyle grows, knee replacement surgery is becoming increasingly common in younger and more active patients, and there is an increasing demand for a longer duration for the replaced joint. The lifespan of artificial joints is limited and malfunctions occur over time, requiring further surgery, which is technically difficult, costly, and has a less predictable outcome than the primary surgery. After undergoing TKR, patients are discharged from the hospital on average three days later in the UK and then receive physical therapy to optimize the function of the knee. Patients visit an orthopedic surgeon once every three months after surgery and then at various times based on the patient's progress. However, the information obtained from these visits is only a snapshot of the patient's recovery and does not evaluate the patient's progress in detail after surgery. It is difficult to accurately evaluate the patient's progress without detailed information about the patient's daily activities.

[0004] Instrumented implants remain underdeveloped because existing technologies are complex, expensive, and not practical. To date, instrumented implants require a laboratory / controlled environment and are bulkier than standard implants, with the drawback that additional bone and / or soft tissue must be removed to accommodate them.

[0005] In some cases, patients are provided with external tracking devices that can assist clinicians in monitoring the patient's progress. Since these can be cumbersome and may cause errors if not worn properly, patients need to be reminded to use the device throughout the day. Thus, the information obtained is variable and not always accurate.

[0006] The present invention seeks to address at least some of these problems. SUMMARY OF THE INVENTION

[0007] The present disclosure provides an implantable device for monitoring an intra-articular environment corresponding to an articular body, such as a bone or a prosthetic joint component. The implantable device includes a sensor module configured to measure data indicative of at least one parameter of the intra-articular environment corresponding to the articular body, a communication unit operably coupled to the sensor module and configured to transmit the measured data to an external device, and a rechargeable battery configured to supply power to the sensor module and the communication unit. The sensor module, the power source, and the communication unit are housed within a capsule, the capsule is removably mountable within an opening of the articular body, and when the capsule is removably mounted within the opening of the articular body, the sensor module is configured to monitor at least one parameter of the intra-articular environment.

[0008] This has the advantage that characteristics of the joint environment, such as mechanical, chemical or biological characteristics, can be monitored in real time. The term "joint environment" as used herein includes the prosthetic or natural surfaces commonly used to define a synovial joint, such as joint surfaces, as well as the synovial fluid itself. By way of example, this includes monitoring characteristics such as the mechanical wear of polymer inserts typically found in replaced knee and hip joints.

[0009] The sensor module may include one or more of a motion sensor, a temperature sensor, a force sensor, and a chemical sensor for measuring at least one parameter. The implanted device may include a non-volatile memory configured to store patient data. The implanted device may include a support frame for mounting the sensor module at a predetermined position within the capsule.

[0010] The sensor module may include a plurality of strain gauges configured to measure the force applied from the joint body to the capsule. The support frame may include a central region extending along the longitudinal axis of the capsule. The plurality of strain gauges may be at least partially disposed on either side of the central region. The strain gauges may be arranged in a staggered pattern.

[0011] The sensor module, the power source, and the communication unit may be embedded within the capsule. The capsule may be substantially solid. The capsule may include a formable material. Suitable formable materials include liquid materials and solid materials. Solid formable materials include, for example, powders that can be formed into the desired shape of the capsule using compression molding or pressure molding. When a liquid material such as PMMA or polyurethane is used, it can be cast or formed in a mold. A two-part resin is an example of a formable material.

[0012] The communication unit may be adapted to transmit measurement data in response to receiving user input. The communication unit may be configured to transmit measurement data to an external device outside the joint environment.

[0013] The capsule may be removably attachable to the joint body by press-fitting connection with the opening of the joint body. The capsule may be removably attachable to the joint body by a locking mechanism.

[0014] The implantable device may include an insert for use with prosthetic joint components. The capsule may be removably attached to the insert. The capsule may be attached to the insert by press-fitting connection. The capsule may be attached to the insert by a locking mechanism.

[0015] The insert may include a polymeric material. The insert may include a recess for receiving the capsule. The insert may include a non-loading region adjacent to the loading region. The recess may be formed in the non-loading region.

[0016] The insert may include an articular surface configured to engage a corresponding articular surface of a second joint body or an implant body. The loading region may be part of the articular surface.

[0017] The insert may include a substantially planar structure defining a normal axis. The recess may extend through the insert at an acute angle to the normal axis.

[0018] The insert may include a second articular surface spaced apart from the first articular surface. The second articular surface may be configured to engage a corresponding second articular surface of a second joint body or an implant body defining the joint environment. The non-loading region may be disposed between the first articular surface and the second articular surface.

[0019] The insert may include a hemispherical portion. The recess may be formed on the lower surface of the insert.

[0020] The insert may be adapted for use with any of a replacement ankle joint, a replacement knee joint, a replacement hip joint, a replacement wrist joint, a replacement elbow joint, or a replacement shoulder joint.

[0021] The implantable device may include a receiving circuit configured to wirelessly receive power from a charging module outside the intra-articular environment to charge a rechargeable battery.

[0022] A charging module for supplying power to the implantable device is also provided, where the communication unit includes a Bluetooth® low energy module configured to transmit measurement data in a data packet including the measurement data and the device's location identification parameters. The charging module includes a receiving unit configured to receive the data packet, a charging coil configured to generate a magnetic field for wirelessly transferring power to the rechargeable battery of the implantable device, and a controller operably coupled to the charging coil and the receiving unit, the controller being configured to operate the charging coil by a first transmission method, the controller being configured to adapt the first transmission method based on the location identification parameters to provide a second transmission method, and the controller being configured to operate the charging coil by the second transmission method.

[0023] The charging coil may be embedded within a fabric layer. The charging module may include a plurality of charging coils. A first coil of the plurality of charging coils may be disposed in a first plane. A second charging coil of the plurality of charging coils may be disposed in a second plane. The first plane may be substantially perpendicular to the second plane.

[0024] A method for wirelessly powering an embedded device including a Bluetooth low energy communication unit using a charging module is also provided, where the charging module is configured to supply power to the embedded device by a first transmission method using one or more charging coils, and the method includes receiving a data packet including location parameter of the embedded device, the data packet being received by the charging module from the Bluetooth low energy communication unit of the embedded device, adapting the first transmission method to a second transmission method based on the location parameter, and operating the charging module by the second transmission method to induce charge in the embedded device.

[0025] The method may include determining performance parameters of the induced charge. The method may include adapting the second transmission method to a third transmission method based on the performance parameters. The method may include operating the charging module by the third transmission method.

[0026] A method for using an embedded device for monitoring a joint environment is also provided. Optionally, the embedded device monitors one or more mechanical characteristics of the joint environment, such as an insert. In some cases, the embedded device monitors the joint environment between a first surgical procedure and a second surgical procedure.

[0027] A method including removing an implanted embedded device from a joint environment is also provided. In some cases, removing the embedded device includes removing an insert on which the embedded device is mounted. The method may include implanting the embedded device within the joint environment. In some cases, a previously removed embedded device is implanted into the joint environment. In some cases, a new embedded device is implanted into the joint environment.

[0028] Embodiments of the present invention are further described below with reference to the accompanying drawings.

Brief Description of the Drawings

[0029]

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DETAILED DESCRIPTION OF THE INVENTION

[0030] Referring to FIGS. 1 to 3, an implantable device 10 is provided for monitoring the joint environment within a joint such as the knee joint. The illustrated implantable device 10 includes four strain gauges 25A to 25D, a triaxial accelerometer, and a temperature sensor for measuring forces, movements, and temperatures within the knee joint. A communication unit, such as a Bluetooth® module, is also provided to enable two-way communication with an external device, such as a patient's smartphone, to transmit measurement data to the external device and, optionally, to receive software updates from the patient's smartphone or a further external device. The electrical components of the implantable device 10 are preferably encapsulated in a capsule 15 to seal the electrical components from the joint environment. By encapsulating the electrical components in this way, the implantable device 10 can be removably mounted directly, for example press-fitted, into the tibia / femur opening or, as part of the tibial insert 50, into a prosthetic component, such as within a tibial tray, when the implant is used in a total knee replacement. While press-fitting is preferred, a locking mechanism may be used additionally or alternatively to press-fitting for mounting the implantable device 10 into the tibial insert 50. The locking mechanism may include any one of one or more resiliently deformable elements, such as one or more pegs, cantilever clips, screws, or pins. In one example, the capsule 15 includes a threaded portion for engaging corresponding threads in the insert 50 and / or the joint body.

[0031] The implantable device 10 can be removably attached to alternative prosthetic components such as the acetabular cup of a replacement hip joint implant. Since implantable devices of the same design can be used with different prosthetic components, there is an advantage in simplifying the manufacturing process of instrumentation devices for monitoring the joint environment. The joint environment will be apparent to include, but not be limited to, the synovial capsule and the fluid contained therein, as well as the surfaces that define the joint capsule, such as natural or artificial joint surfaces. Monitoring the joint environment involves monitoring one or more characteristics of the joint environment using corresponding sensors as described below. By way of example, chemical, mechanical, and biological characteristics of the joint environment are described, but it will be apparent that other characteristics can also be measured with appropriate sensors. By way of example, monitoring the wear of the tibial insert 50 is an example of a mechanical characteristic that the implantable device 10 can monitor.

[0032] The capsule 15 enclosing the implantable sensor 10 includes a notch 17 at one end having a cross-section corresponding to the notch 56 (see FIG. 4C) present in the tibial insert 50. However, it will be apparent that the notch 17 is not essential and depends on the position of the implantable device 10 in the tibial insert 50. When the implantable device 10 is implanted in a prosthetic component of a joint other than the bone or knee (e.g., hip, ankle, shoulder, or elbow), it will be apparent that the notch 17 may be replaced with other suitable surface features corresponding to the joint in question or may be completely omitted. The capsule 15 is omitted from FIGS. 3 and 4 for clarity.

[0033] Since the implantable device 10 is mounted within the tibial insert 50 of a total knee arthroplasty, this enables data measured by the implantable device 10 to be transmitted to an external device such as a patient's or surgeon's mobile phone, allowing for continuous monitoring of the knee joint after surgery. This, in turn, allows for more appropriate monitoring of postoperative recovery and compliance with prescribed physical therapy practices, helping to address two major problem areas of primary arthroplasty: 1) rehabilitation, and 2) diagnosis of implant malfunctions. Thus, the present disclosure provides an implantable device that aids in the early diagnosis of infection, instability, or loosening in asepsis, the three major reasons for malfunctions, resulting in a significant benefit to the patient and reducing the diagnostic cost burden associated with multiple expensive tests performed before making a decision to revise the implant. A further advantage of the present implantable device 10 is that it can be introduced into an existing polymer insert design of standard thickness, without additional bone loss, for this improved monitoring. Additionally, the implantable device 10 can be used as a temporary device for two-stage revision of an infected implant to monitor markers of infection prior to the second-stage procedure.

[0034] By enabling the patient to access their own data, the patient can obtain quantifiable feedback regarding their progress and become more self - sufficient in promoting and monitoring their recovery. The implant device 10 also provides advantages to the surgeon, who can continuously monitor the joint environment compared to snapshots in time, and intervene in a timely manner when the data indicates that there are problems occurring within the joint, such as restrictions in the range of motion, excessive wear of the tibial insert 50 preceding mechanical failures of the replacement joint, joint infections, or loosening of the implant. This reduces the need for hospital visits, enables significant cost savings, potentially allows for early detection of major complications, and enables timely interventions that are often less invasive, less expensive, and lead to better outcomes than those that would have been necessary if the intervention had been delayed due to a late diagnosis. Since the implant device 10 does not wear out, even if it is necessary to replace the prosthetic joint components and / or the tibial insert 50, the patient can simply have the implant device 10 removed from the old / worn - out parts (such as the polymeric tibial insert 50) and installed into the replacement parts, and thus can retain the same implant device 10 throughout their life. In some cases, it may be desirable to replace the implant device 10 with a new implant device when the tibial insert 50 is replaced. This is particularly true when there is a high risk of infection when reusing the original implant device 10. When a new implant device is used, it may be the same as the original implant device, or it may be an improved or revised implant device with different electrical components.

[0035] The implanted device 10 provides advantages at different times. Intra-operative advantages include the ability to measure data to improve force distribution, joint balance, recording of range of motion, selection of optimal bearing size and joint alignment. In the short term (0 - 6 weeks), shorter hospital stays, active patient involvement, early identification of poor progress, and input of targeted physical therapy can be provided based on the measured data. In the medium term (6 weeks - 5 years), for example, remote follow-up in response to patient-led follow-up requests, follow-up based on changes in activity level / type, and detection of other failure modes such as infection, instability, implant loosening, things that increase stress are possible. In the long term (>5 years), the implanted device 10 enables better planning of revision surgery as it can store both the components and surgical details as well as the associated radiographs in the implanted device 10 itself without the need to access patient records typically stored at the hospital where the surgery was initially performed. Also, diagnostic monitoring of the implanted device is possible, for example, to detect excessive wear of the tibial insert 50, implant loosening, infection and perform remote clinical follow-up.

[0036] In the examples shown in FIGS. 1 and 2, the capsule 15 is provided as a two-component polymethyl methacrylate (PMMA) resin, and the electrical components are embedded in the resin. However, it is clear that this was not essential, and the electrical components can be encapsulated as described using other compositions or arrangements of the capsule 15. Also, it is clear that one or more of the force, temperature, or motion sensing components were not essential, and depending on the specific requirements of the implantable device 10, one or more of these may be omitted. Also, in some cases, it is clear that additional sensors, such as an electrochemical sensor for measuring the chemical properties of the joint environment, may be included in the implantable device 10. Examples of electrochemical sensors include pH sensors and glucose sensors that can be connected to input / output pins that are also suitable for connecting to strain gauges 25A-25D. If a chemical sensor is included, the capsule 15 may include one or more channels that allow the drainage of intra-articular joint fluid into the capsule 15 to reach the chemical sensor. Although a two-component resin is described, it is clear that this is only one example of a moldable material suitable for forming the capsule 15.

[0037] The capsule 15 defines an internal volume in which the electrical components are located. The internal volume may be partially or wholly solid. If the capsule 15 is completely solid (i.e., there is no hollow portion within the internal volume), a direct load path is provided between the insert 50 and the strain gauges 25A - 25D, and the strain gauges 25A - 25D can be attached to the support frame 20 as shown in FIGS. 1A and 1B. When a hollow capsule 15 is used, the strain gauges 25A - 25D are preferably attached to the inner surface of the capsule 15 to detect the load applied to the capsule 15. The capsule 15 is shown to have a substantially cylindrical shape, although it is clear that this is not essential. The cylindrical shape corresponds to the round holes such as those provided in the tibial insert shown, but if the implant device 10 is to be mounted within a recess having a non - circular cross - section, the capsule 15 may have a cross - section corresponding to the recess. This may be the case when the implant device 10 is to be mounted on a hip joint insert 650 (see also FIGS. 17 and 18) designed to be mounted on the acetabular component 615 to form an artificial acetabular cup.

[0038] The hip joint insert 650 includes a recess 625 for receiving the implant device 610, and the implant device 610 may be arranged as described herein with respect to the implant device 10. The implant device 610 may be different from the implant device 10 in the capsule configuration, and the capsule configuration may be shaped to correspond to the recess 625 of the non-circular polymer hip joint insert 650. Thereby, the load applied to the acetabular cup can be transmitted to the capsule as described above with respect to the tibial insert 50. The implant device 610 may be housed within the hip joint insert 650 or may be partially received by the hip joint insert 650. When the implant device 610 is partially received within the hip joint insert 650, the recess 625 may be formed on a surface 612 configured to abut the acetabular component 615 such that the implant device 610 is at least partially disposed between the acetabular component 615 and the hip joint insert 650. By positioning the recess 625 within the hip joint insert 650, the implant device 610 can be positioned within a similar unloaded region of the acetabular cup. This can be achieved by positioning the recess on the inferior aspect of the hip joint insert 650. By way of example, the inferior aspect is considered to be any part of the hip joint insert 650 that is below a transverse plane 620 that intersects the radial center of the hip joint insert 650 when considered in the anatomical position.

[0039] In addition to the sensors described herein, the implantable device 10 preferably includes on-board non-volatile memory for storing measurement data and patient data. By storing patient information related to surgical procedures, such as surgical records, X-rays, implant details, and pre-operative symptoms recorded using verified means, the patient can carry the information, and this information is available to all medical professionals without the need to request all relevant information from the center where the original treatment was performed. By loading and storing patient data in the implantable device 10, the patient can control who they share the data with and when, rather than relying on a central database that may not always be accessible when needed. For example, the patient may have an electronic device, such as a mobile phone, that communicates with the implantable device 10. An application on the mobile phone allows the patient to view and share the data stored on the implantable device 10.

[0040] Referring to FIGS. 1A, 1B and 4A to 4C, the embedded device 10 includes a support frame 20 (see FIG. 4A) arranged to accurately position electrical components and sensors at predetermined positions on the embedded device 10. The support frame 20 is preferably 3D printed to enable further custom production, for example, based on the specific electrical components required and the form of the joint in which the embedded device 10 is embedded. The support frame 20 includes a first portion 22 for supporting a printed circuit board on which electrical components are mounted, and a second portion 24 arranged to position the first portion 22, and thus the electrical components, at a predetermined position within the capsule 15. The first portion 22 positions the electrical components at a predetermined longitudinal position within the capsule 15. The second portion positions the electrical components at a predetermined radial position within the capsule 15. The support frame 20 is designed to place the electrical components at the center of the capsule 15. Both sides of the support frame 20 can support the electrical components. A further advantage of embedding the electrical components is that the relative positions between the embedded components remain fixed, thus improving the consistency and reproducibility of the manufactured embedded device 10. One advantage of this is that any calibration parameters of the electrical components, such as strain gauges 25A to 25D, are applicable to different devices and each embedded device 10 does not need to be calibrated during the manufacturing process.

[0041] For example, a printed circuit board can be mounted on one side of the support frame 20, and strain gauges 25A - 25D can be mounted on the opposite side of the support frame 20. Referring to FIG. 1, the first portion 22 has a central region extending along the longitudinal axis 61 of the capsule 15. Since the strain gauges 25A - 25D are mounted in an alternating arrangement, each strain gauge 25A - 25D intersects the longitudinal axis 61 extending through the center of the capsule 15, for example, when viewed from the perspective shown in FIG. 4C, so as to at least partially overlap the central region of the printed circuit board. In some cases, the strain gauges 25A - 25D may be further spaced apart from the longitudinal axis 61 (i.e., the strain gauges 25A - 25D are spaced apart from the longitudinal axis 61 by a perpendicular distance to the longitudinal axis 61) such that one or more of the strain gauges 25A - 25D do not intersect the longitudinal axis 61. This arrangement provides the ability to measure strains applied at different positions along the capsule 15 and can be used to determine the anterior - posterior and medial - lateral loads applied to the tibial insert 50, as will be described below. As shown in FIG. 4A, the capsule 15 has a circular cross - section, and the second portion 24 circumscribes the cross - section of the capsule 15. However, it is clear that this is not essential, and other arrangements of the second portion 24 and other cross - sectional shapes of the capsule 15 can be used. In the illustrated example, the first portion 22 forms a substantially flat surface that extends along the longitudinal axis of the capsule 15 and can fix the printed circuit board and the strain gauges 25A - 25D. The first portion 22 is connected to the second portion 24 at the end of the first portion 22. The strain gauges 25A - 25D are shown mounted centrally within the capsule 15, spanning the longitudinal axis 61 and a second axis perpendicular to the longitudinal axis 61 and distributed within the plane 58, but it is clear that this is not essential, and other arrangements of the strain gauges distributed along two perpendicular axes (i.e., a staggered arrangement) can be used to determine the center of the pressure of the force applied to the capsule 15 by interpolating the measured strain data.

[0042] The tibial insert 50 is also provided with a recess 52 for receiving the implant device. The recess 52 has a cross-section that provides an interference fit between the implant device 10 and the tibial insert 50. In the illustrated embodiment, the recess 52 is a blind hole, although it is clear that this is not essential and the recess may have a non-circular cross-section. The tibial insert 50 has a planar surface 53 that abuts against a corresponding surface on the tibial component in use. The planar surface 53 may define a planar surface 58 and a normal axis 60 to the planar surface 58. In the example shown, the planar surface 58 is substantially parallel to the coronal plane and the normal axis 60 is substantially parallel to the vertical axis of the insert. The recess 52 is shown as extending from the posterior side of the tibial insert 50 towards the center of the tibial insert 50. As shown, the recess 52 extends in a direction substantially perpendicular to the normal axis 60. In the example shown, this is in the anterior direction, although it is clear that this is not essential. The tibial insert 50 preferably comprises a polymeric material, such as polyethylene. While the tibial insert 50 is shown, it will be apparent that inserts for use with prosthetic components for other joints are also suitable for use with the present implant device 10. In some cases, the implant device 10 may be attached to the prosthetic component without an insert.

[0043] Figure 4C shows the articular surfaces 54A, 54B of the tibial insert 50. Since the articular surfaces 54A, 54B have a cross-sectional shape corresponding to the femoral condyles (either a natural femur or a replacement implant), the replacement knee joint has a range of motion as close as possible to that of a natural knee joint. Since the femoral component 5 contacts the tibial insert 50 at the articular surfaces 54A, 54B, the articular surfaces 54A, 54B can be regarded as the load regions 62 of the tibial insert 50 (see FIGS. 5A, 5B, and 7A to 7C). The two articular surfaces 54A, 54B are spaced apart from each other, and a non-load region 64 is provided in the space between the articular surfaces 54A and 54B. In the example of the tibial insert 50, the non-load region 64 corresponds to a location where the femoral component 5 does not contact the tibial insert 50 during normal use. Also, since the tibial insert 50 is a continuous part of the material, some deformation occurs within the non-load region 64, but it will also be apparent that these loads are much smaller than the loads applied to the load regions 62 during normal activities of daily life.

[0044] FIGS. 6A to 6H show finite element analyses of exemplary loading scenarios compliant with ISO 14243-1:2009 and ASTM F3141-17a. These correspond to walking (FIG. 6A), walking with a 100 kg load (FIG. 6B), walking downstairs (FIG. 6C), walking upstairs (FIG. 6D), performing a pivot turn (FIG. 6E), performing a crossover turn (FIG. 6F), standing up from and sitting on a chair (FIG. 6G), and jogging (FIG. 6H). As is apparent from the computational model, there is some strain in the intercondylar notch (non-load region 64), but these are much smaller than the loads applied to the articular surfaces 54A, 54B (load regions 62). However, these are detectable values that can be monitored using strain gauges 25A to 25D or alternative force sensors, such as capacitive sensors. Thereby, while sufficient support material 66 is required under the load regions 62, it is possible to remove the material in the non-load region 64, for example, to provide the recess 52 for the implanted device 10, without significantly affecting the performance of the tibial insert 50. Therefore, it is advantageous to provide a recess in the non-load region 64.

[0045] By incorporating the recess 52 into the non - loading region 64, the incorporation into the insert has a minimal adverse impact on the function of the insert and the overall replacement joint, so it is quite easy to obtain regulatory approval for the implantable device 10. By providing the implantable device 10 that can be used modularly as described herein, the manufacturing process is significantly simplified. The implantable device 10 is a stand - alone device that can be manufactured in a controlled setting independently of the prosthetic joint components into which the implantable device 10 will ultimately be installed. Similarly, the existing manufacturing process of the prosthetic joint components requires only minimal modification to function with this implantable device. For example, introducing a recess into the tibial insert 50 can be achieved by several processes, such as drilling holes in the existing tibial insert 50 or 3D printing an insert with a recess incorporated into the original manufacturing design file.

[0046] The implantable device 10 also has advantages regarding obtaining regulatory approval. Since the implantable device can be manufactured independently of the prosthetic joint components, as the implantable device 10 is updated or modified, only the implantable device 10, rather than the entire replacement joint, needs to be re - evaluated.

[0047] As described above, referring to FIG. 6, introducing the recess 52 into the non - loading region 64 of the tibial insert 50 has little impact on the performance of the tibial insert 50. By modifying the existing already - approved design in this way, it can be considered when evaluating the modified tibial insert 50 regarding the evaluation of the existing device, so the approval process is also rationalized.

[0048] Furthermore, by encapsulating the electrical components, even if mechanical or electrical defects occur in the implant device 10, it is possible to remove the tibial insert, or the components encapsulated separately from the tibial insert 50, in which case the tibial insert 50 can remain attached to the tibial tray (in the case of the knee joint). Thus, advantageously, the modular components 10, 50 are easier to remove / replace than a complete tibial joint component fixed to the bone, so only a minimally invasive surgery is required to retrieve the implant device 10. The implant device 10 of FIG. 1 has a maximum diameter of 10 mm and a length of 25 mm. However, it is clear that smaller dimensions (e.g., 8 mm diameter) are desirable if possible within the constraints of the available electrical components. As a further safety measure, the recess 52, and thus the capsule 15, may be arranged to provide a minimum distance (e.g., 5 mm) from the articular surfaces 54A, 54B.

[0049] When the implant device 10 of FIG. 1 is implanted, it is possible to measure the 3D orientation with respect to gravity, the range of motion of the joint, the walking pattern, the magnitude of the force applied to the load area 62 and the center of pressure, separate the medial-lateral load from the anterior-posterior load, and the joint temperature.

[0050] Figures 7A through 7C show exemplary data from a polymeric portion representing alternative tibial inserts loaded in different scenarios. The Y-axis shows voltage in mV, where line "A" corresponds to the strain on the right side of the tibial insert 50 and line "B" corresponds to the strain on the left side of the tibial insert 50. FIG. 7A shows the sensor output when a load is applied by the femoral component 5 to the anterior area of the tibial insert 50 (left image in FIG. 7A). FIG. 7B shows the sensor output when a load is applied by the femoral component 5 to the central area of the same tibial insert 50 (left image in FIG. 7B). FIG. 7C shows the sensor output when a load is applied by the femoral component to the posterior area of the tibial insert 50 (left image in FIG. 7C). As can be seen in the different voltage outputs (right images in FIGS. 7A through 7C), it is possible to determine where the load is being applied to the tibial insert 50 using the implant device 10.

[0051] FIG. 8 shows exemplary force data measured by the implantable device of FIG. 3 when worn on an intact tibial tray. The Y-axis shows voltage in mV, where the lines "A", "B", "C" and "D" correspond to the outputs from each of the four strain gauges 25A-25D of the implantable device 10. Note in FIG. 8 that all of the signals from the strain gauges 25A-25D are negative when a load is applied. However, when the tibial tray is damaged, the output from the force sensors will be different even if the same load conditions are applied to the insert. As shown in FIG. 9, the output signals from the four strain gauges 25A-25D that make up the force sensor are significantly different from the output signals of FIG. 8. Specifically, the polarities of some of the strain gauge outputs (particularly outputs "A" and "B" in FIG. 9) are reversed and become positive when a load is applied to the tibial insert. It is clear that this is merely exemplary and in some cases the output signal may change in a different manner due to a damaged tibial tray, for example, it may vary significantly from past values regardless of whether there is a change in the polarity of the signal.

[0052] FIG. 10 shows exemplary kinematic data measured by the implantable device of FIG. 3 when worn on a tibial tray. The lines "A", "B" and "C" represent the three axes of rotation of the accelerometer of the implantable device 10, and the Y-axis shows the output acceleration relative to gravity. As shown by line A, the implantable device 10 can reliably measure knee flexion. Further tests have shown that the implantable device 10 can also reliably measure joint kinematics during walking, running, descending stairs, ascending stairs, turning and jumping.

[0053] In contrast to an articular body (a bone or a tibial tray in the illustrated example), the ability to monitor the intra-articular environment of a prosthetic joint is important for a clinician to be able to anticipate implant malfunctions. Data measured by an implantable device can better support clinical decision-making because the data provided by the implantable device 10 is a richer dataset for the clinician. For example, any combination of a change in temperature (e.g., a temperature increase relative to historical data), joint forces (e.g., a change in the polarity and / or magnitude of the force measurements described above), movement (e.g., an increase in vibration can indicate loosening of the implant) may indicate an implant malfunction. It will be apparent that implant malfunctions can result from excessive wear, implant loosening and / or malfunction of the tibial insert 50 due to infection or instability. These malfunction modes have associated parameters that can be monitored as described herein.

[0054] In some cases, the implantable device may be configured to output an alert to an external device to warn the surgeon of a change in a measured parameter. The implantable device 10 may include an on-board processor configured to monitor the measured data for anomalies and output an alert. The processor may store a history of the sensor data and use it as a criterion for determining that the current parameter is outside the expected range.

[0055] The implanted device 10 also includes a rechargeable battery, for example having a capacity of 25 mAh, for supplying power to the electrical components, and a circuit for charging the rechargeable battery. Referring to FIGS. 11 and 12, the rechargeable battery can be wirelessly charged using a charging module 100. The charging module 100 includes two coils 105A, 105B arranged perpendicular to each other. A support frame 110 is provided as that on which the coils 105A, 105B are mounted. The frame can also be connected to a power supply "P", such as a main power supply voltage, for supplying power to the charging module 100. In the illustrated example, the support frame 110 is rigid and holds the coils 105A, 105B in the desired vertical (orthogonal) arrangement. This arrangement has been found to be particularly effective in inducing charge in the circuit of the implanted device when the implanted device is implanted in the body. As shown in FIG. 12, this charging module 100 can induce charge in the circuit when arranged outside the knee joint. Line "A" represents the charging voltage in mV, and line "B" represents the battery voltage in mV. Tests have shown that the charging module 100 can charge the rechargeable battery at a distance of 60 mm through the soft tissue around the human knee joint. The implanted device 10 includes an induction coil that can be regarded as a receiving coil. The charging module 100 includes an induction coil that can be regarded as a transmitting coil. However, it will be apparent that the rigid support frame 110 is not essential, and the coils 105A, 105B may be, for example, integrally mounted within a sleeve or support appliance that the patient 1 can wear over the implanted device 10 (see FIGS. 13 and 14). The sleeve may be configured as clothing to be worn over the joint, or may be integrated into a flexible fabric that can be worn over the joint as described below.

[0056] Figures 13 and 14 show alternative charging modules. In Figure 13, the charging module 200 includes a fabric layer 210 in which a plurality of charging coils 205A - 205D are embedded. The charging coils 205A - 205D may be configured to function in the same manner as described above with respect to coils 105A, 105B. Thus, when a patient 1 with the implantable device 10 lies on top of the fabric 210 in the form of, for example, a blanket or a bottom sheet laid under a standard bed sheet, the coils 205A - 205D within the fabric layer 210 can be activated, so that the implantable device 10 can be charged during an overnight sleep. In Figure 14, the charging module 100 is configured as a wearable knee brace 300 that includes a fabric layer 310 with a plurality of charging coils 305 embedded therein. For example, the charging module can include coils 305 on both sides of the knee brace 300 (only one coil 305 is shown on the side of the knee in Figure 14). Thus, a patient can perform daily activities while the implantable device 10 is charging. It will be apparent that the implantable device 10 may transmit data when the charging module supplies power to the implantable device 10.

[0057] The charging module 100 includes a controller 115 configured to adapt the transmission method in which the coils 105A, 105B operate in order to improve charging performance. Although the embodiment of Figure 11 is referenced, it is apparent that the following method is more widely applicable to charging modules including those shown in Figures 13 and 14. The charging module 100 may also preferably include a power source or be powered by a main power supply.

[0058] FIG. 15 shows an exemplary method 400 for charging the implantable device 10. When the implantable device 10 transmits data 405 to an external device, this data is typically in the form of a data packet that includes location-specific parameters corresponding to the type of communication module used to transmit the data packet. If the communication module is a Bluetooth Low Energy module, the data packet can include data indicating the strength of the Bluetooth® signal used to transmit the data packet. The external device can then use this information to determine 410 the distance between the external device that receives the data packet and the implantable device 10, for example, by calculating the received signal strength indicator (RSSI) of the data packet. Since the range of the Bluetooth signal is up to 100 m at most under optimal conditions and the RSSI accuracy is about 2 - 4 m, this is sufficient to detect 415 when the patient is near the charging module, such as the blanket 200, and activate 420 one or more transmission coils 205A - 205D to charge the implantable device 10. In one example, the controller may activate all the charging coils of the blanket 200 when it is detected that the implantable device 10 is in proximity to the blanket 200. The position of the blanket 200 may be determined using steps 405 and 410 that determine its position relative to the external device. As will be explained below, it is not essential to activate all the charging coils.

[0059] In the case of the blanket 200, since a number of coils 205A to 205D may be distributed throughout the fabric 210, in order to perform a more robust charging process with optimized power demand, location parameters are used to operate one or more of the charging coils 205A to 205D closest to the implant device 10, and only the charging coils 205A to 205D selected according to the location of the patient 1 on the blanket 300 may be operated. In some cases, a Bluetooth (registered trademark) detector located around the room where the charging module is located can transmit and return location information to the implant device 10. Accordingly, the implant device 10 is provided with its position relative to the charging module 200. Since the implant device 10 can directly monitor the speed at which it is being charged, information related to charging performance, such as the charging speed of the rechargeable battery, is combined with the position of the implant device 10 relative to the charging module 300 to identify the position of the implant device 10 with higher accuracy than possible by other methods using only the accuracy of Bluetooth RSSI. Subsequently, the transmission method used to operate the charging coils 205A to 205D can be adjusted accordingly to improve the coupling efficiency between the charging coils 205A to 205D and the implant device 10.

[0060] FIG. 16 shows a second exemplary method 500 of charging the implantable device 10. For example, according to the first transmission scheme 505, each of the charging coils 205A-205D is activated sequentially. The charging rate of the implantable device 10 can be associated 510 with when each of the charging coils 205A-205D is operating. By comparing 515 the different charging rates obtained during the first transmission scheme 505, the charging coil that induces the peak charging rate is identified 520. The position of the charging coil associated with this peak charging rate, for example, charging coil 205C in FIG. 13, thus provides a more accurate position of the implantable device 10 (as compared to relying only on RSSI) since it is reasonable to infer that the implantable device 10 is closest to charging coil 205C. The controller 15 can then adapt the first transmission scheme such that only charging coil 205C operates according to the second transmission scheme 525. This results in power-efficient charging since the remaining coils 205A, 205B, 205D do not operate. However, it will be apparent that one or more additional coils (e.g., 205B and 205D) are operated in the second transmission scheme in consideration of patient movement. For example, charging coils adjacent (e.g., radially adjacent) to the charging coil identified as having the peak charging rate can also be operated.

[0061] This method 500 may be performed at multiple times to ensure that one or more charging coils closest to the implantable device 10 operate at night even if the patient moves at night. This may be done according to a predetermined time interval or in response to the charging rate falling below a predetermined threshold. Methods 400 and 500 may be combined in various ways. For example, in step 420, instead of activating all the charging coils, the controller 115 may sequentially activate the charging coils in step 505 without performing step 420. Alternatively or additionally, after all of the charging coils 205A-205D have been activated in step 420, the controller 115 may perform the steps of method 500 to operate the charging coils 205A-205D as a third transmission schedule in step 525.

[0062] As an example, the transmission method used to operate the charging coils 205A to 205D can be adapted by simply turning different charging coils on or off according to the position and / or proximity of the embedded device 10 with respect to the charging coils 205A to 205D. As shown in FIG. 11 or FIG. 14, when the charging coils are arranged perpendicular to each other, the charging coils can operate in opposite phases to improve the charging performance. The phase of the charging coil can be adapted to any of the charging modules described herein, but it will be apparent that other parameters may be adapted to optimize the charging performance and increase the charging range. These include any combination of the frequency, amplitude, and polarity of the charging coil signal.

[0063] The capsule can be made of not only polymer materials but also metals. The capsule can be a hollow capsule made of metal or polymer. The capsule can have not only a hemispherical surface but also a flat surface. The capsule can have various shapes including, but not limited to, tablet, bullet, and cylindrical shapes.

[0064] Throughout the description and claims of this specification, the words "comprise" and "contain" and their variations mean "including but not limited to", and they are not intended (nor do they exclude) to exclude other parts, additives, components, integers or steps. Throughout the description and claims of this specification, unless the context otherwise requires, the singular form includes the plural form. In particular, when an indefinite article is used, this specification should be understood as considering both the singular and the plural, unless the context otherwise requires.

[0065] It should be understood that any feature, integer, characteristic, or group described in connection with a particular aspect, embodiment, or example of the invention is applicable to any other aspect, embodiment, or example described herein, unless there are compatibility issues. All features disclosed herein (including the accompanying claims, abstract, and drawings) and / or all steps of any method or process so disclosed may be combined in any combination, except combinations in which at least some of such features and / or steps are mutually exclusive. The invention is not limited to the details of any of the foregoing embodiments. The invention extends to any novel or novel combination of features disclosed herein (including the accompanying claims, abstract, and drawings), or novel or novel combination of steps of any method or process so disclosed.

Claims

1. An implantable device for monitoring the joint environment within a joint corresponding to a joint body, such as a bone or a prosthetic joint component, comprising: a sensor module configured to measure data indicative of at least one parameter of the joint environment within the joint corresponding to the joint body; a communication unit operably coupled to the sensor module and configured to transmit the measured data to an external device; a rechargeable battery configured to supply power to the sensor module and the communication unit; wherein the sensor module, the power source and the communication unit are housed within a capsule; the capsule is removably mountable within an opening of the joint body; and when the capsule is removably mounted within the opening of the joint body, the sensor module is configured to monitor the at least one parameter of the joint environment within the joint.

2. The implantable device according to claim 1, wherein the sensor module includes one or more of a motion sensor, a temperature sensor, a force sensor, and a chemical sensor for measuring the at least one parameter.

3. The implantable device according to claim 1 or 2, further comprising a non-volatile memory configured to store patient data.

4. The implantable device according to any one of claims 1 to 3, further comprising a support frame for mounting the sensor module at a predetermined position within the capsule.

5. The implantable device according to any one of claims 1 to 4, wherein the sensor module includes a plurality of strain gauges configured to measure a force applied from the joint body to the capsule.

6. The implantable device according to claims 4 and 5, wherein the support frame includes a central region extending along the longitudinal axis of the capsule, and the plurality of strain gauges are at least partially disposed on both sides of the central region.

7. The implantable device according to any one of claims 1 to 6, wherein the sensor module, the power source and the communication unit are embedded within the capsule.

8. The implantable device according to any one of claims 1 to 7, wherein the communication unit is adapted to transmit measurement data in response to receiving a user input.

9. The implant device according to any one of claims 1 to 8, wherein the capsule is removably attachable to the joint body by press-fitting connection with the opening of the joint body.

10. The implant device according to any one of claims 1 to 9, further comprising an insert for use with a prosthetic joint component, wherein the capsule is removably attached to the insert.

11. The implant device according to claim 10, wherein the capsule is attached to the insert by press-fitting connection.

12. The implant device according to claim 10 or 11, wherein the insert comprises a polymeric material.

13. The implant device according to any one of claims 10 to 12, wherein the insert comprises a recess for receiving the capsule.

14. The implant device according to any one of claims 10 to 13, wherein the insert comprises a non-loading region adjacent to a loading region, and the recess is formed in the non-loading region.

15. The implant device according to any one of claims 10 to 14, wherein the insert comprises an articular surface configured to engage a corresponding articular surface of a second joint body or an implant body, and the loading region is a part of the articular surface.

16. The implant device according to claim 15, wherein the insert comprises a second articular surface spaced apart from the first articular surface, the second articular surface being configured to engage a corresponding second articular surface of the second joint body or the implant body that defines the joint environment, and the non-loading region is disposed between the first articular surface and the second articular surface.

17. The implant device according to any one of claims 10 to 16, wherein the insert comprises a substantially planar structure defining a normal axis, and the recess extends through the insert at an acute angle with respect to the normal axis.

18. The implant device according to any one of claims 10 to 14, wherein the insert comprises a hemispherical portion, and the recess is formed on the lower surface of the insert.

19. The implant device according to any one of claims 10 to 18, wherein the insert is adapted for use with any of a replacement ankle joint, a replacement knee joint, a replacement hip joint, a replacement wrist joint, a replacement elbow joint, or a replacement shoulder joint.

20. The implanted device according to any one of claims 1 to 19, further comprising a receiving circuit configured to wirelessly receive power from a charging module outside the joint internal environment and charge the rechargeable battery.

21. A charging module for supplying power to the implanted device according to any one of claims 1 to 20, wherein the communication unit includes a Bluetooth (registered trademark) low energy module configured to transmit the measurement data in a data packet including the measurement data and the position identification parameters of the device, and the charging module a receiving unit configured to receive the data packet, a charging coil configured to generate a magnetic field for wirelessly transferring power to the rechargeable battery of the implanted device, and a controller operably coupled to the charging coil and the receiving unit and comprising, the controller is configured to operate the charging coil by a first transmission method, the controller is configured to adapt the first transmission method to provide a second transmission method based on the position identification parameters, the controller is configured to operate the charging coil by the second transmission method, a charging module.

22. The charging module according to claim 21, wherein the charging coil is embedded in a cloth layer.

23. The charging module according to claim 21 or 21, further comprising a plurality of charging coils, wherein a first coil of the plurality of charging coils is disposed in a first plane, a second charging coil of the plurality of charging coils is disposed in a second plane, and the first plane is substantially perpendicular to the second plane.

24. A method of wirelessly supplying power to an implanted device including a Bluetooth (registered trademark) low energy communication unit using a charging module, wherein the charging module is configured to supply power to the implanted device by a first transmission method using one or more charging coils, and the method includes receiving a data packet including the position identification parameters of the implanted device, the data packet being received by the charging module from the Bluetooth low energy communication unit of the implanted device, Adapting the first transmission method to a second transmission method based on the position specific parameter; Operating the charging module by the second transmission method to induce charge in the embedded device; A method comprising the steps of. **Claim 25** Determining a performance parameter of the induced charge; Adapting the second transmission method to a third transmission method based on the performance parameter; The method according to claim 24, further comprising operating the charging module by the third transmission method.

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