Smart Plate Sensor

Abstract

1. A patient monitoring system comprising: a bone plate configured for attachment to a bone; a plurality of sensors on the bone plate, the plurality of sensors configured to measure parameters and transmit data signals communicating measured parameter values, the transmitted data signals from the plurality of sensors being time division multiplexed; and an external wireless reader, the external wireless reader including an antenna, a processor, and a wireless communication radio, the external wireless reader configured to transmit modulated RF signals and receive the time division multiplexed transmitted data signals from the plurality of sensors.

Description

[Technical field]

[0001] Various exemplary embodiments disclosed herein generally relate to smart plate sensors that include simultaneous readout from multiple sensors. Additionally, smart place sensors can be used for inflammation and infection detection. Smart plates may also have the ability to align sensors with a reader for the sensor, and may be able to read sensors adjacent to the metal plate. [Background technology]

[0002] A conventional bone fixation system includes a bone plate having threaded holes for receiving fixation members, such as screws, configured to attach to an underlying bone that includes at least a pair of bone segments separated by a bone gap. The bone gap may be a defect caused by a traumatic event, an osteotomy, or may be the result of debridement of a joint of two separate bones to be joined in an arthrodesis. Thus, the bone plate may be secured to the bone on either side of the bone gap via bone screws to promote union of the bone segments (e.g., healing of a fracture or ossification of a joint). The bone fixation system may further include temporary Kirschner wires (K-wires) that are temporarily inserted into the apertures of the bone fixation plate and the underlying bone segment to determine the appropriate length, rotation, and alignment of the bone segments prior to permanent plate fixation. Once the bone fixation plate is properly positioned, permanent bone screws may be inserted into one or more bone screw holes on either side of the bone gap and secured to the underlying bone. Summary of the Invention [Means for solving the problem]

[0003] A summary of various exemplary embodiments is presented below. In the following summary, some simplifications and omissions may be made in order to highlight and introduce some aspects of various exemplary embodiments, and are not intended to limit the scope of the present invention. Detailed descriptions of exemplary embodiments adequate to enable those skilled in the art to make and use the concepts of the present invention follow in each subsequent section.

[0004] Various embodiments relate to a patient monitoring system including a bone plate configured for attachment to a bone, a plurality of sensors on the bone plate, the plurality of sensors configured to measure parameters and transmit data signals communicating measured parameter values, the transmitted data signals from the plurality of sensors being time division multiplexed, and an external wireless reader including an antenna, a processor, and a wireless communication radio, the external wireless reader configured to transmit modulated RF signals and receive the time division multiplexed transmitted data signals from the plurality of sensors.

[0005] Various embodiments are described in which the sensors harvest energy from a modulated RF signal to power the sensors.

[0006] Various embodiments are described in which the modulated RF signal has periodic on-times and off-times, and the sensors are configured to measure a parameter when a falling edge of the on-time of the modulated RF signal is detected.

[0007] Various embodiments are described in which the modulated RF signal has periodic on and off times, and the sensors are configured to transmit a data signal when a rising edge of the on time of the modulated RF signal is detected.

[0008] Various embodiments are described in which the sensors measure one of load, temperature, and position.

[0009] Various embodiments are described in which the plurality of sensors further includes an antenna, a controller configured to control the sensor, and a modulator configured to produce a data signal.

[0010] Various embodiments are described in which the sensors further include a rectifier configured to rectify the modulated RF signal and an energy storage device configured to store energy from the rectifier.

[0011] Various embodiments are described in which the multiple sensors measure voltages based on the received modulated RF signals and transmit the measured voltage values ​​to an external wireless reader, and the external wireless reader is configured to receive the measured voltage values ​​from the multiple sensors, compare the received voltage values ​​to a sensor voltage profile, and generate instructions related to moving the external wireless reader to improve alignment between the multiple sensors and the external wireless reader, and generate instructions related to moving the external wireless reader to improve alignment between the multiple sensors and the external wireless reader.

[0012] Various embodiments are described in which the external wireless reader is configured to display instructions on a display regarding moving the external wireless reader.

[0013] Various embodiments are described in which the sensors are configured to measure temperature and the reader is configured to detect the presence of inflammation or infection based on the temperature measurements.

[0014] Various embodiments are described in which the plurality of sensors includes a resonator circuit configured to capture power from a modulated RF signal, and parameters of the resonator circuit are based on a distance between the plurality of sensors and a bone plate to achieve a desired resonant frequency associated with wireless power transfer.

[0015] Various embodiments are described in which the distance between the sensors and the bone plate is set by an electrically insulating layer between the sensors and the bone plate.

[0016] Further various embodiments relate to a method for monitoring a bone plate having multiple sensors, the method including: measuring a parameter by the multiple sensors; transmitting by the multiple sensors data signals communicating measured parameter values, where the transmitted data signals from the multiple sensors are time division multiplexed; transmitting by a reader a modulated RF signal; and receiving by the reader the time division multiplexed transmitted data signals from the multiple sensors.

[0017] Various embodiments are described that further include harvesting energy from the modulated RF signal from the multiple sensors to power the multiple sensors.

[0018] Various embodiments are described in which the modulated RF signal has periodic on and off times, and further including measuring a parameter with a plurality of sensors when a falling edge of the on time of the modulated RF signal is detected.

[0019] Various embodiments are described in which the modulated RF signal has periodic on and off times, and further including transmitting, by the plurality of sensors, a data signal when a rising edge of the on time of the modulated RF signal is detected.

[0020] Various embodiments are described in which the sensors measure one of load, temperature, and position.

[0021] Various embodiments are described further including measuring voltages based on the modulated RF signals received by the multiple sensors; transmitting the measured voltage values ​​by the multiple sensors to an external wireless reader; receiving the measured voltage values ​​from the multiple sensors by the reader; comparing the received voltage values ​​to a sensor voltage profile by the reader; and generating instructions by the reader to move the external wireless reader to improve alignment between the multiple sensors and the external wireless reader.

[0022] Various embodiments are described that further include displaying, by the reader, instructions on a display regarding moving the external wireless reader.

[0023] Various embodiments are described further including measuring temperature with a plurality of sensors and detecting the presence of inflammation or infection based on the temperature measurements with a reader. [Brief description of the drawings]

[0024] For a better understanding of various exemplary embodiments, reference is made to the following drawings. [Figure 1] FIG. 1 is a schematic diagram of a system for monitoring fracture healing. [Diagram 2] FIG. 1 is a schematic diagram of an implantable smart fixation device for surgically repairing fractured bones. [Diagram 3] FIG. 1 is a schematic side perspective view of an external wireless reader for wirelessly interfacing with an implantable smart fixation device. [Figure 4] FIG. 1 is a schematic diagram of a portable computing device in wireless communication with an implantable smart fixation device via an external antenna. [Diagram 5] 5 is a schematic diagram of a progression of user interface display screens that may be displayed to a patient via a portable computing device such as shown in FIGS. 3 and 4 during a measurement. FIG. [Figure 6]A reader that reads data from n sensors is shown. [Figure 7] A reader and sensor as shown in FIG. 6 are shown together with a block diagram of the sensor. [Figure 8] 1 shows the RF signal sent by the reader to interrogate the sensor and the timing of the sensor's data return to the reader. [Figure 9] 1 shows how to align a reader with a sensor. [Figure 10] The sensor is shown at a distance D from the bone plate.

[0025] For ease of understanding, the same reference numbers are used to denote components having substantially the same or similar structures and / or substantially the same or similar functions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The present description and drawings exemplify the principles of the present invention. Thus, it should be understood that those skilled in the art can devise various configurations that embody the principles of the present invention and are encompassed within the scope of the present invention, although not explicitly described or presented herein. Furthermore, all examples shown herein are expressly intended primarily for educational purposes to aid the reader in understanding the principles of the present invention and the concepts contributed by the inventor(s) to advance the present technology, and should be construed as not being limited to such specifically shown examples and conditions. Additionally, the term "or" as used herein refers to a non-exclusive logical or (i.e., and / or) unless otherwise indicated (e.g., "or otherwise" or "or alternatively"). Also, the various embodiments described herein are not necessarily mutually exclusive, since some embodiments can be combined with one or more other embodiments to form new embodiments.

[0027] Referring to the drawings, in which like reference numbers are used to identify similar or identical components in the various views, FIG. 1 illustrates generally a system 10 for remotely monitoring the healing / ossification of a fracture or other bone joint that is internally fixed with a bone plate 12 and a plurality of permanent fixation members, such as bone screws 14 (better shown in FIG. 2). Generally, the system 10 includes a data server 20 and / or a cloud computing system 22 that operates to receive patient data 24 from one or more patient monitoring systems 26 via a wireless communication network 28. The data server 20 / cloud computing system 22 may store the received patient data 24 in an associated non-volatile memory / database 30 and may visually present this data to a medical professional 32 via a hosted physician interface 34. The patient monitoring system 26 may be configured to periodically monitor the amount of load carried by the bone plate 12 spanning the fracture throughout the duration of the healing process. This load measurement may be normalized to the load carried by the bone plate 12 away from the fracture and may be periodically transmitted from the patient monitoring system 26 to the data server 20 where it may be aggregated with other patient data 24 to highlight trends in fracture healing.

[0028] Continuing to refer to FIG. 1, the data server 20 may be implemented as one or more high-speed server computers or mainframe computing devices capable of handling bulk data processing and data visualization tasks. Meanwhile, the cloud computing system 22 may operate as middleware for Internet of Things (IoT), Web of Things (WoT), and / or machine-to-machine (M2M) services to connect a combination of heterogeneous electronic devices with a service-oriented architecture (SOA) over a data network. As an example, the cloud computing system 22 may be implemented as a middleware node to dynamically onboard heterogeneous devices, multiplex data from each of these devices, and provide different capabilities for routing the data through reconfigurable processing logic for processing and transmission to one or more destination applications. The wireless communication network 28 may be any available type of network, including a combination of a public distributed computing network (e.g., the Internet) and a secure private network (e.g., a local area network, a wide area network, a virtual private network). It may also include wireless and wired transmission systems (e.g., satellites, cellular networks, terrestrial networks, etc.) Most, if not all, data transaction functions may be performed, for example, over a wireless network, such as, for example, a wireless local area network (WLAN) or a cellular data network operating according to a 4G, 5G, LTE, LPWAN, LTE-M, CAT-M1, or NB-IoT protocol.

[0029] 1, the patient monitoring system 26 generally includes an implantable smart fixation device 40 and an external (external) wireless reader 42 for interfacing with the smart fixation device 40. The external wireless reader 42 is configured to wirelessly receive data from the smart fixation device 40 through the patient's skin, for example, via a radio frequency (RF) data communication means such as RFID or NFC. In at least some embodiments, the external wireless reader 42 may be further configured to wirelessly provide power to the smart fixation device 40, which may enable the fixation device 40 not to require an internal battery to operate.

[0030] With reference to FIG. 2, an implantable smart fixation device 40 may include a rigid bone plate 12 configured to span and be secured to opposing sides of a fracture 50 using a plurality of permanent fixation members, such as bone screws 14. The position of the bone plate relative to the fragments will vary depending on the location of the fracture, the geometry of the bone plate, and the particular bone being repaired. The bone plate 12 may be formed from any suitable implantable material, such as, but not limited to, a metal (e.g., titanium alloy) or a polymer, such as polyether ether ketone (PEEK). Although the present disclosure generally discusses the use of remote monitoring technology in connection with bone plate type fixation devices, the technology may also be utilized with other rigid fixation members, such as implantable rods, pedicle screws, intervertebral implants, and the like.

[0031] The smart fixation device 40 may generally include at least one primary load sensor 52 operative to sense the load borne by the plate 12 at the fracture 50. As the fracture heals / ossifies, the amount of load borne by the plate 12 at the fracture 50 should decrease (i.e., the load-bearing capacity of the healing bone increases accordingly). In many embodiments, the smart fixation device may further include at least one reference load sensor 54 operative to sense the load borne by the plate 12 at a location spaced away from the fracture. The reference load sensor 54 may generally serve as a baseline for the amount of load borne by the plate 12 adjacent to healthy or unfractured bone.

[0032] In one configuration, each load sensor 52, 54 may include one or more strain gauges 60 having electrical properties that change in an established manner depending on the amount of strain the gauge / plate is subjected to at that location. Examples of suitable strain gauges include resistive strain gauges, capacitive strain gauges, piezoelectric materials, electroactive polymer materials, etc. Each strain gauge 60 may be held in firm, rigid contact with the plate 12 such that the gauge experiences any bending or deflection of the plate. As is well established, strain and load are directly proportional, and therefore measuring strain is one way of monitoring the load carried by the plate.

[0033] 2, the smart fixture device 40 further includes a communication circuit 62 electrically coupled to each strain gauge 60 and an antenna 64 in communication with the communication circuit 62. The communication circuit 62 is configured to receive measurements from the strain gauges 60 and provide the measurements to the antenna 64 in a form suitable for wireless transmission. The communication circuit 62 may include a wireless transmitter or transponder that receives measurements from the strain gauges 60 and prepares the measurements for wireless transmission. For example, the communication circuit 62 may include processing components such as (but not limited to) one or more of: (i) a memory configured to store the measurements; (ii) a digital-to-analog converter configured to convert the measurements to an analog format; (iii) a radio frequency (RF) modulator configured to modulate the measurements; (iv) an error correction encoder configured to encode the measurements; and other processing consistent with the wireless technology employed by the system.

[0034] In one example, the communication circuit 62 may be configured as a passive radio-frequency identification (RFID) transponder. Alternatively, the communication circuit 62 may be configured using any other wireless communication technology suitable for communicating through the skin, such as (but not limited to) battery-assisted passive RFID, active RFID, Bluetooth, and Wi-Fi. The communication circuit 62 may further include a unique identifier (ID) that may be used to distinguish each load sensor from other sensors. In one embodiment, the unique ID may be an ID of an RFID tag. The antenna 64 is configured to convert an electrical signal corresponding to the measurement from the communication circuit 62 into radio waves and wirelessly transmit the measurement through the patient's skin to an external wireless reader 42 located outside the patient's body.

[0035] As further shown in FIG. 2, the smart fixturing device 40 can include a power supply device 66 configured to provide power to the strain gauges 60 and the communication circuitry 62. In at least some embodiments, the power supply device 66 can include an energy harvesting device configured to harvest energy from a suitable energy source separate from the smart fixturing device 40. For example, the energy source can be radio waves communicated from the external wireless reader 42. Alternatively, the power supply device 66 can harvest energy from the patient's body itself or from another external source, such as a source outside the patient's body. More broadly, the energy source can include (but is not limited to) sensed kinetic energy, electric fields, magnetic fields, and the like. However, in a preferred embodiment, the power supply device 40 does not include a typical electrochemical battery.

[0036] In one configuration, each load sensor 52, 54 may have its own dedicated communication circuitry 62, antenna 64, and / or power device 66 (i.e., as an integrated package) that is local to the respective load sensor. In this configuration, the primary load sensor 52 may transmit a first wireless signal indicative of the amount of strain monitored by the primary load sensor 52 (i.e., a primary strain value), while the reference load sensor 54 may simultaneously transmit a second wireless signal indicative of the amount of strain monitored by the reference load sensor 54 (i.e., a reference strain value). In other embodiments, the smart stationary device 40 may have a common communication circuitry 62, antenna 64, and / or power device 66 that may be shared throughout the device 40 (i.e., each load sensor 52, 54 is in electrical communication with the shared communication circuitry 62, antenna 64, and / or power device 66). Further embodiments and disclosure of the smart fastening device 40 are provided in U.S. Patent Application Publication No. 2019 / 0038214, the entirety of which is incorporated by reference herein for all purposes.

[0037] As mentioned above, the external wireless reader 42 is configured to wirelessly receive data from the smart fixation device 40 through the patient's skin. To facilitate these communications, the external wireless reader 42 generally includes one or more antennas 70, such as a radio frequency identification (RFID) antenna that communicates with a portable computing device 72, as generally shown in FIG. 3. The antenna 70 may be configured to be attached directly to an external surface of the patient's body or clothing. This attachment may be facilitated by the use of one or more straps 73, harnesses, braces, adhesive patches, elastic sleeves, cuffs, and the like. In one particular embodiment, the antenna 70 may be provided within a flexible fabric carrier 74, which may be particularly suited to contour to the user's body. The antenna 70 may generally include a looped coil having a length adapted to extend parallel to the bone plate 12 and a width adapted to extend circumferentially across and / or around the bone plate 12. The length may control the amount of plate with which the antenna can communicate, while the width may affect the depth of tissue at which the antenna receives a reliable signal. In one configuration, the length of the antenna 70 is longer than the distance between the primary load sensor 52 and the reference load sensor 54. In another configuration, the length of the antenna 70 is at least 10% longer than the distance between the primary load sensor 52 and the reference load sensor 54. In one embodiment, the antenna 70 may have a length of about 20 cm to about 50 cm, or about 25 cm to about 40 cm. Similarly, the antenna 70 may have a width of about 12 cm to about 20 cm, or about 14 cm to about 17 cm.

[0038] As shown in FIG. 4, the portable computing device 72 may include short-range communication circuitry 76 and / or power transmission circuitry 78 in communication with the antenna 70. The short-range communication circuitry 76 may be operative to receive digital information from the smart stationary device 40 via the antenna 70. In some embodiments, the short-range communication circuitry 76 may include a digital receiver or transceiver, such as an RFID transceiver or a Near Field Communications (NFC) transceiver. In one configuration, the antenna 70 may operatively communicate with each load sensor 52, 54 simultaneously, for example, by using different data transmission frequencies or by using different digital identifiers provided with the strain data. The power transmission circuitry 78 may include an inductive charging circuit operative to provide an electromagnetic force (i.e., an alternating magnetic field) via the antenna 70 to inductively power the smart stationary device 40.

[0039] Continuing to refer to FIG. 4, the portable computing device 72 (see FIG. 3) may further include a processor 80, a wireless communication radio 82, and a user interface 84. The wireless communication radio 82 may be operable to communicate with and over the wireless communication network 28 and may include a BLUETOOTH or BLUETOOTH low energy chipset, an ultrawideband (UWB), a Wi-Fi radio operable to digitally communicate using an IEEE 802.11 communication protocol, or a cellular radio operable to communicate according to a 4G, 5G, LTE, LPWAN, LTE-M, CAT-M1, NB-IoT protocol, or the like. In some embodiments, the portable computing device 72 may further include a subscriber identity module (SIM) card to facilitate communication over the cellular network.

[0040] Processor 80 may be embodied as one or more digital computers, data processing devices, and / or digital signal processors (DSPs) that may have one or more microcontrollers or central processing units (CPUs), read only memory (ROM), random access memory (RAM), electrically-erasable programmable read only memory (EEPROM), high speed clocks, analog-to-digital (A / D) circuitry, digital-to-analog (D / A) circuitry, input / output (I / O) circuitry, and / or signal conditioning and buffering electronics. Processor 80 is configured to execute or perform one or more electronic functions through the execution of software or firmware code stored in non-volatile memory accessible by processor 80. For example, the processor 80 may be capable of executing code to read one or more strain values ​​from the smart stationary device 40, code to select an average or filtered representative strain value, code to communicate with a user via a user interface 84, and / or code to communicate over the wireless communications network 28 via a wireless communications radio 82. The user interface (84) may include one or more microcontrollers or central processing units (CPUs), data processors, and / or digital signal processors (DSPs), read only memory (ROM), random access memory (RAM), electrically erasable programmable read only memory (EEPROM), high speed clocks, analog-to-digital (A / D) circuitry, digital-to-analog (D / A) circuitry, input / output (I / O) circuitry, and / or signal conditioning and buffering electronics.

[0041] The portable computing device 72 may communicate with the antenna 70 using either a wired or wireless communication link. In one configuration as generally shown in FIG. 3, the portable computing device 72 may be electrically coupled to the antenna 70 through the use of a wired tether (not shown). Such a design may have the advantage of providing a self-contained diagnostic device that relies only on a single power source. More specifically, in the absence of a wired tether, the antenna 70 would require a first power source to enable / power communication with both the sensor and the portable computing device 72, while the portable computing device 72 would require a second power source. Coupling the two elements reduces the need for consumers to maintain sufficient battery levels on two separate devices, while also reducing the complexity and overall size of the device. The wired tether also allows the portable computing device 72 to be held in a convenient and accessible position during data acquisition without requiring a tense posture to view a screen that may otherwise be out of the patient's field of view. In one configuration, the antenna portion of the device may further include a holster or other anchoring mechanism for attaching and anchoring the portable computing device 72 when not in use.

[0042] In another embodiment, the portable computing device 72 may wirelessly communicate with a smart phone or tablet using an appropriate wireless protocol.

[0043] As further shown in Figure 4, the user interface 84 may include a visual display 88, such as an LCD or OLED display, and one or more input devices 90, such as buttons or a touch screen digitizer. As generally shown in Figure 5, the display 88 may operate to provide one or more visual cues to the patient, such as indicating the start of a reading (92), verifying sensor alignment (94), directing the positioning and occurrence of a reference measurement (96), directing the positioning and occurrence of a load bearing measurement (98), and / or uploading the measurement data to a data server / cloud via wireless communication network 28 (100). The display 88 may include other sensors, such as load sensors, accelerometers, temperature sensors, or any other sensors that measure values ​​of interest.

[0044] As mentioned above, a bone plate may have multiple sensors that can be read by a single reader. FIG. 6 shows a reader reading data from n sensors. The reader 142 transmits an RF amplitude modulated signal 160 that powers the sensors 150, 152, 154. Although amplitude modulation is described, other types of modulation may be used, including but not limited to frequency modulation, pulse width modulation, phase modulation, load modulation, phase shift keying modulation, frequency shift keying, amplitude shift keying, quadrature amplitude modulation, and the like. While the sensors described above were primary load sensors, the sensors 150, 152, 154 may be one or more of load sensors, accelerometers, temperature sensors, or any other sensors that measure a value of interest. Data from multiple sensors 150, 152, 154 may need to be read simultaneously, so the sensors 150, 152, 154 need to communicate with the reader 142 without interference. FIG. 7 shows the reader and sensors shown in FIG. 6 along with a block diagram of the sensors. The sensor may include an antenna 264, a rectifier 244, an energy storage device 246, a voltage regulator 248, a microcontroller 250, and a modulator 242. The antenna 264 may be a coil antenna or any other type of antenna that can fit into the small form factor of the sensor. The sensor receives an RF amplitude modulated signal 160 from the reader 142. The rectifier 244 rectifies the received signal, and the rectified signal is used to store energy in the energy storage device 246. The energy storage device 244 may be a small rechargeable battery, a capacitor, or any other energy storage device. As the received signal 160 is pulsed (i.e., has an on time and an off time and a duty cycle), the energy storage device 246 can store enough energy from the pulse to power the operation of the sensor until the next pulse is received. The voltage regulator 248 is connected to the energy storage device 246 and adjusts the supply voltage used to power the microcontroller 250.The microcontroller 250 controls the operation of the sensor, including controlling the sensing elements in the sensor, collecting data from the sensing elements, processing the data from the sensing elements, and facilitating the transmission of the sensed data back to the reader 142. The microcontroller 250 may control the modulator 242, which generates a modulated signal that is transmitted back to the reader 142 by the antenna 264. The modulated signal modulates the data from the sensing elements onto a carrier signal.

[0045] FIG. 8 shows the RF amplitude modulated signal transmitted by the reader to interrogate the sensors and the timing of the sensor's data transmission to the reader. The RF amplitude modulated signal 160 is transmitted by the reader 142. The transmission signal 160 may power the sensors 150, 152, 154. When the falling edge of the transmission signal 168 is sensed at the end of the on-time, the sensors then perform measurements 170, 172, 174 and process the measurement data. Then, when the next pulse of the transmission signal 160 is received and the rising edge of the on-time is detected, each sensor transmits its sensed data 180, 182, 184 to the reader 142. To prevent collisions between the data transmitted by each of the sensors 150, 152, 154, each sensor has a specific time window for transmitting its sensor data 180, 182, 184. Thus, the data transmitted by each of the sensors 150, 152, 154 is time division multiplexed. The data transmitted by each sensor may be identified as associated with a particular sensor based on the particular time window used. Alternatively, a particular sensor ID may be transmitted as part of the sensor data 180, 182, 184. Thus, the on-time of the pulses in the transmit signal 160 must be long enough to allow the sensor data 180, 182, 184 from each of the sensors 150, 152, 154 to be transmitted as well as to provide sufficient power to the sensors to perform various operations. Additionally, the off-time of the transmit signal 160 may be selected to provide sufficient time for the sensors to measure data. Depending on the particular application, the duty of the cycle of the transmit signal may be long or short. Time division multiplexing of the sensor 150, 152, 154 transmission of the sensor data 180, 182, 184 allows a single reader 142 to read multiple sensors associated with a bone plate.

[0046] One challenge in reading data from the sensors is finding the optimal alignment of the reader 142 and the sensors 150, 152, 154. This alignment is important when the sensors 150, 152, 154 are inductively powered using a transmit signal 160 because proper alignment maximizes the power received by the sensors 150, 152, 154. If the reader is not properly aligned, the sensors 150, 152, 154 may not receive enough energy to operate properly.

[0047] This alignment problem may be solved by measuring the rectified voltage received by each of the individual sensors 150, 152, 154 and sending these values ​​back to the reader 142. The reader 142 contains a profile of the desired voltage for each of the sensors 150, 152, 154 that indicates proper alignment of the reader. The reader can then compare the measured voltages to the profile and determine if the reader is properly aligned. If not, the reader may then generate instructions to the user of the reader to move the reader in a particular direction. In one embodiment, the sensors of the reader (142) shall be used to confirm the direction the patient has been moving the reader (142). The reader then receives updated voltages from each sensor and updates the instructions to the user until the reader is properly positioned within a certain tolerance level.

[0048] FIG. 9 illustrates a method of aligning a reader with a sensor. The method 900 starts (905) and then interrogates the sensor (910). This may be done by the reader sending a specific signal to the sensor that the sensor recognizes as a voltage interrogation request. The sensor then measures the voltage of the received interrogation signal and communicates the measured voltage value to the reader (910). The reader then compares the measured voltage to the sensor voltage profile (920). The reader then determines whether the measured voltage matches the voltage profile (925). This may be done in a variety of ways. For example, a weighted sum of the differences between each measured voltage and the profile voltage may be calculated, and this weighted sum may then be compared to a threshold. When the sum is less than the threshold, the reader is properly aligned, and the reader may send an indication to the user aligning the reader that the reader is properly aligned (935). This may be done using the user interface 84 on the visual display 88. When the sum is greater than the threshold, the reader may then generate instructions regarding movement of the reader to improve alignment. For example, if there are three sensors in a row, the sensor voltage profile may show that the voltages when aligned are 0.75V, 1.0V, and 0.75V. If the voltages come back as 0.5V, 0.75V, and 1.0V, this indicates that the reader needs to be moved in a direction toward the first sensor. After the instructions are given, the method 900 again queries (910) the sensors and the process is repeated until the reader is aligned. This iterative process provides the user of the reader with the prompts needed to properly align the reader. In other embodiments, the reader may include motion sensing devices that may be used to aid in the alignment process. They may help determine the prompts to provide to the user during alignment. It may also detect when no movement occurs after a prompt has been given to the user, so that further instructions may be provided to the user or another indicator may be provided, such as generating a sound to alert the user.

[0049] Local temperature may indicate local inflammation or infection. Thus, the communication capabilities of the plates described herein may be used to facilitate measuring local temperature to assess whether inflammation or infection is present around the bone plate. Early detection of inflammation or infection may lead to earlier treatment leading to improved patient outcomes. For example, if inflammation becomes severe, it may be necessary to explant the bone plate and wait for a relaxation period before reimplanting the device, and early detection of inflammation and infection may prevent this course of treatment.

[0050] One or more temperature sensors may be placed on the bone plate. The sensors may be stand-alone sensors or may be integrated with other sensors as described above. The sensors are then periodically interrogated to gather temperature information. This information may be analyzed by the reader and transmitted to the data server 20 for further analysis. Various algorithms may be applied to the temperature data to determine if inflammation or infection is indicated. The patient or the patient's healthcare provider may then be alerted of the condition and any necessary treatment provided.

[0051] The sensor uses inductive power supply based on using a specific frequency and resonator circuit. Since the bone plate is a large metal object near the sensor, the bone plate can lead to detuning of the resonator circuit that converts the RF signal into power. FIG. 10 shows the sensor 150 at a distance D from the bone plate 12. The detuning effect on the resonator circuit is based on the distance between the sensor 150 and the bone plate 12. This causes a frequency shift in the resonator circuit, leading to a reduction in power transmission. This can be overcome by selecting a distance D between the sensor 150 and the bone plate 12. At this distance, the detuning of the resonator circuit can be determined. The resonator circuit can then be designed such that when the sensor 150 is at a distance D from the bone plate 12, the detuning of the resonator circuit due to the presence of the bone plate 12 causes the resulting circuit to achieve a desired resonant frequency corresponding to maximum power transfer. To ensure that the distance D is maintained between the bone plate 12 and the sensor 150, an electrically insulating material can be used as a barrier between the sensor 150 and the bone plate 12. Other methods of fixing the sensor at a particular distance D from the bone plate may be used as well.

[0052] Although each of the embodiments are described above with respect to their structural arrangements, it should be understood that the present invention also encompasses associated methods of using the above-described embodiments.

[0053] Although various exemplary embodiments have been described in detail with particular reference to certain exemplary aspects thereof, it should be understood that the invention is capable of other embodiments and its details can be modified in various obvious respects. As will be readily apparent to those skilled in the art, variations and modifications of the various embodiments and combinations can be effected while remaining within the spirit and scope of the invention. Accordingly, the foregoing disclosure, description, and drawings are for illustrative purposes only and do not limit the invention, which is defined solely by the claims.

[0054] [Embodiment] (1) A patient monitoring system comprising: a bone plate configured to be secured to a bone; A plurality of sensors on the bone plate, the plurality of sensors comprising: Measure the parameters, configured to transmit a data signal communicating the measured parameter value; a plurality of sensors, the transmitted data signals from the plurality of sensors being time division multiplexed; an external wireless reader, the external wireless reader including an antenna, a processor, and a wireless communication radio, the external wireless reader comprising: Transmitting a modulated RF signal; and A patient monitoring system configured to receive the transmitted data signals from the plurality of sensors in a time division multiplexed manner. (2) A patient monitoring system as described in embodiment 1, wherein the plurality of sensors harvest energy from the modulated RF signal to power the plurality of sensors. (3) the modulated RF signal has periodic on-times and off-times; 2. A patient monitoring system as described in embodiment 1, wherein the plurality of sensors are configured to measure the parameter when a falling edge of the on-time of the modulated RF signal is detected. (4) the modulated RF signal has periodic on-times and off-times; 2. A patient monitoring system as described in embodiment 1, wherein the plurality of sensors are configured to transmit the data signal when a rising edge of the on-time of the modulated RF signal is detected. (5) A patient monitoring system as described in embodiment 1, wherein the plurality of sensors measure one of load, temperature, and position.

[0055] (6) The plurality of sensors include The antenna, A controller configured to control the sensor; 2. The patient monitoring system of claim 1, further comprising: a modulator configured to produce the data signal. (7) The plurality of sensors include a rectifier configured to rectify the modulated RF signal; 7. The patient monitoring system of claim 6, further comprising an energy storage device configured to store energy from the rectifier. (8) the plurality of sensors measure voltages based on the received modulated RF signals and transmit the measured voltage values ​​to the external wireless reader; The external wireless reader includes: receiving the measured voltage values ​​from the plurality of sensors; comparing the received voltage values ​​to a sensor voltage profile; and 2. A patient monitoring system as described in embodiment 1, configured to generate instructions for moving the external wireless reader to improve alignment between the multiple sensors and the external wireless reader. (9) A patient monitoring system as described in embodiment 8, wherein the external wireless reader is configured to display the instructions regarding moving the external wireless reader on a display. (10) The plurality of sensors are configured to measure temperature; 2. A patient monitoring system as described in embodiment 1, wherein the reader is configured to detect the presence of inflammation or infection based on temperature measurements.

[0056] (11) The plurality of sensors includes a resonator circuit configured to harvest power from the modulated RF signal; A patient monitoring system as described in embodiment 1, wherein parameters of the resonator circuit are based on the distance between the multiple sensors and the bone plate to achieve a desired resonant frequency associated with wireless power transfer. (12) A patient monitoring system as described in embodiment 11, wherein the distance between the plurality of sensors and the bone plate is set by an electrically insulating layer between the plurality of sensors and the bone plate. (13) A method for monitoring a bone plate having a plurality of sensors, comprising: measuring parameters with the plurality of sensors; transmitting data signals communicating parameter values ​​measured by the plurality of sensors, the transmitted data signals from the plurality of sensors being time division multiplexed; transmitting, by the reader, a modulated RF signal; receiving, by the reader, the transmitted data signals time division multiplexed from the plurality of sensors. (14) The method of embodiment 13, further comprising harvesting energy from the modulated RF signal from the plurality of sensors to power the plurality of sensors. (15) The method of embodiment 13, wherein the modulated RF signal has periodic on and off times, and further comprising measuring the parameter with the plurality of sensors when a falling edge of the on time of the modulated RF signal is detected.

[0057] (16) The method of embodiment 13, wherein the modulated RF signal has periodic on and off times, and further comprising transmitting, by the plurality of sensors, the data signal when a rising edge of the on time of the modulated RF signal is detected. (17) The method of embodiment 13, wherein the plurality of sensors measure one of load, temperature, and position. (18) measuring voltages based on the modulated RF signals received by the plurality of sensors; and transmitting voltage values ​​measured by the plurality of sensors to the external wireless reader; receiving, by the reader, the measured voltage values ​​from the plurality of sensors; comparing, by the reader, the received voltage values ​​to a sensor voltage profile; 14. The method of claim 13, further comprising generating, by the reader, instructions for moving the external wireless reader to improve alignment between the plurality of sensors and the external wireless reader. (19) The method of embodiment 18, further comprising displaying, by the reader, the instructions regarding moving the external wireless reader on a display. (20) measuring temperature with the plurality of sensors; and 14. The method of claim 13, further comprising detecting, by the reader, the presence of inflammation or infection based on the temperature measurement.

Claims

1. 1. A patient monitoring system comprising: a bone plate configured to be secured to a bone; A plurality of sensors on the bone plate, the plurality of sensors comprising: Measure the parameters, configured to transmit a data signal communicating the measured parameter value; a plurality of sensors, the transmitted data signals from the plurality of sensors being time division multiplexed; an external wireless reader, the external wireless reader including an antenna, a processor, and a wireless communication radio, the external wireless reader comprising: Transmitting a modulated RF signal; and A patient monitoring system configured to receive the time division multiplexed transmitted data signals from the plurality of sensors.

2. The patient monitoring system of claim 1 , wherein the plurality of sensors harvest energy from the modulated RF signal to power the plurality of sensors.

3. the modulated RF signal has periodic on-times and off-times; The patient monitoring system of claim 1 , wherein the plurality of sensors are configured to measure the parameter when a falling edge of the on-time of the modulated RF signal is detected.

4. the modulated RF signal has periodic on-times and off-times; The patient monitoring system of claim 1 , wherein the plurality of sensors are configured to transmit the data signal when a rising edge of the on-time of the modulated RF signal is detected.

5. The patient monitoring system of claim 1 , wherein the plurality of sensors measures one of load, temperature, and position.

6. The plurality of sensors include The antenna, A controller configured to control the sensor; The patient monitoring system of claim 1 , further comprising: a modulator configured to produce the data signal.

7. The plurality of sensors include a rectifier configured to rectify the modulated RF signal; 7. The patient monitoring system of claim 6, further comprising an energy storage device configured to store energy from the rectifier.

8. The plurality of sensors measure voltages based on the received modulated RF signals and transmit the measured voltage values ​​to the external wireless reader; The external wireless reader includes: receiving the measured voltage values ​​from the plurality of sensors; comparing the received voltage values ​​to a sensor voltage profile; and The patient monitoring system of claim 1 , configured to generate instructions for moving the external wireless reader to improve alignment between the plurality of sensors and the external wireless reader.

9. The patient monitoring system of claim 8 , wherein the external wireless reader is configured to display the instructions regarding moving the external wireless reader on a display.

10. the plurality of sensors are configured to measure temperature; The patient monitoring system of claim 1 , wherein the external wireless reader is configured to detect the presence of inflammation or infection based on temperature measurements.

11. the plurality of sensors including a resonator circuit configured to harvest power from the modulated RF signal; The patient monitoring system of claim 1 , wherein a parameter of the resonator circuit is based on a distance between the plurality of sensors and the bone plate to achieve a desired resonant frequency associated with wireless power transfer.

12. 12. The patient monitoring system of claim 11, wherein the distance between the plurality of sensors and the bone plate is set by an electrically insulating layer between the plurality of sensors and the bone plate.

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