Pedicle screw system for monitoring microtraumatic screw loosening

Abstract

A screw system includes a screw that has a foramen. The screw includes an inertial measurement unit mounted within the foramen of the screw and configured to detect movement of the screw. The system also includes a monitoring unit in communication with the inertial measurement unit, where the monitoring unit transmits data from the inertial measurement unit to a remote application.

Description

Atty. Dkt. No. 00100-0412-PCTPEDICLE SCREW SYSTEM FOR MONITORING MICROTRAUMATIC SCREW LOOSENINGCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority benefit of U.S. Provisional Patent App. No. 63 / 725,877 filed on November 27, 2024, the entire disclosure of which is incorporated by reference herein.BACKGROUND

[0002] A pedicle screw is a threaded implant that is used to help secure other implant components to bone, such as a vertebra. For example, pedicle screw s are commonly used in spinal procedures to help secure rods and / or plates to vertebral pedicles. Pedicle screws come in various sizes to accommodate different patients and different types of procedures, and are ty pically made from titanium or stainless steel, but other biocompatible materials can also be used. Many pedicle screws have a partially hollow- interior (i.e., a foramen) to help reduce weight, to allow for use of bone cement to help secure the screw, to allow for the use of instrumentation such as K- wires, markers, etc., and to accommodate other surgical techniques and applications.SUMMARY

[0003] An illustrative pedicle screw system includes a commercial pedicle screw that has a foramen. The pedicle screw includes a sensing unit which contains an inertial measurement unit, an optional vibroacoustic sensor, and an optional temperature sensor mounted w ithin the foramen of the pedicle screw7and configured to detect movement of the pedicle screw and / or rod and / or plate. The system also includes a monitoring unit in communication with the sensing unit, w here the monitoring unit transmits data from the sensors to a remote application.

[0004] In an illustrative embodiment, a remote application processes the data from the inertial measurement unit to identify movement of the pedicle screw7. In another embodiment, the remote application compares the detected motion of the pedicle screw to a predefined movement threshold and / or to relative motion values obtained from multiple pedicle screwsensors within the same construct. If the detected motion of a pedicle screw exceeds the movement threshold or exhibits abnormal relative motion compared to one or more adjacentAtty. Dkt. No. 00100-0412-PCT sensors, the remote application can automatically generate an alert indicating a potential loosening condition or other mechanical abnormality. In another embodiment, the inertial measurement unit is mounted within a drop-in sensor unit that is sized to fit within the foramen of the pedicle screw. The drop-in sensor unit can be fully encapsulated in a biocompatible material to isolate the electronics from surrounding tissue and to maintain long-term implant safety7. In another embodiment, the inertial measurement unit is positioned at a distal end of the pedicle screw within the bone.

[0005] In another embodiment, a spinal rod is connected to the pedicle screw, and the system includes a second inertial measurement unit mounted to the spinal rod. In another embodiment, a third inertial measurement unit is attached directly to the posterior vertebral body. In another embodiment, the monitoring unit is in communication with the second and third inertial measurement units and transmits data from the inertial measurement units to the remote application. Another embodiment includes a temperature sensor mounted within the monitoring unit. In one embodiment, the monitoring unit is subcutaneously mounted on a patient, and the temperature sensor detects the temperature of the patient and provides the temperature to the remote application. In another embodiment, the remote application monitors the temperature to identity7a temperature increase that is indicative of inflammation or infection.

[0006] In another embodiment, the monitoring unit is externally mounted on a patient, and the monitoring unit receives the data wirelessly. In another embodiment, the monitoring unit wirelessly provides power to the inertial measurement unit. In another embodiment, a vibroacoustic sensor is mounted within the foramen of the pedicle screw and configured to detect vibrations of the pedicle screw.

[0007] An illustrative method of making a smart pedicle screw system includes mounting an inertial measurement unit mounted within a foramen of a pedicle screw such that the inertial measurement unit detects movement of the pedicle screw. The method also includes positioning a monitoring unit in communication with the inertial measurement unit, where the monitoring unit transmits data from the inertial measurement unit to a remote application. The method can also include mounting the inertial measurement unit to a sensor probe and mounting the sensor probe within the foramen such that an end of the sensor probe extends beyond the foramen of the pedicle screw. The method can also include mounting aAtty. Dkt. No. 00100-0412-PCT vibroacoustic sensor to the sensor probe. The method can also include mounting a temperature sensor to the sensor probe. The method can further include placing the inertial measurement unit into a drop-in sensor unit that is sized to fit within the foramen of the pedicle screw, and encapsulating the drop-in sensor unit in a biocompatible material.

[0008] Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description, and the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Illustrative embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like numerals denote like elements.

[0010] Fig. 1 depicts a vertebra in accordance with an illustrative embodiment.

[0011] Fig. 2 depicts various views of pedicle screws fixed to a standard rod in accordance with an illustrative embodiment.

[0012] Fig. 3 A is a side view of smart pedicle screws mounted to vertebrae in accordance with an illustrative embodiment.

[0013] Fig. 3B is a lateral cross-sectional view of a mounted smart pedicle screw in accordance with an illustrative embodiment.

[0014] Fig. 3C is a posterior view of a mounted pedicle screw system with smart pedicle screws in accordance with an illustrative embodiment.

[0015] Fig. 4 depicts the bioencapsulated power and transmission unit implanted in a patient in accordance with an illustrative embodiment.

[0016] Fig. 5 depicts components of the power and transmission unit in accordance with an illustrative embodiment.

[0017] Fig. 6A is a cross-sectional side view of a mounted pedicle screw system in accordance with an illustrative embodiment.

[0018] Fig. 6B is a posterior side view of a mounted pedicle screw system in accordance with an illustrative embodiment.Atty. Dkt. No. 00100-0412-PCT

[0019] Fig. 7 shows a system in which power and data are wirelessly transmitted between a smart pedicle screw and an external unit in accordance with an illustrative embodiment.

[0020] Fig. 8 depicts a user wearing a harness that holds an external unit in accordance with an illustrative embodiment.

[0021] Fig. 9 depicts another embodiment of a computing device connected to a smart pedicle screw in accordance with an illustrative embodiment.

[0022] Fig. 10 depicts the sensor probe mounted within the screw foramen in accordance with an illustrative embodiment.

[0023] Fig. 11 depicts a sensor unit for a pedicle screw that includes an IMU and a temperature sensor in accordance with an illustrative embodiment.

[0024] Fig. 12 depicts a porcine surgery to test the pedicle screw sensor system in accordance with an illustrative embodiment.

[0025] Fig. 13 shows sensor results for two screws (48L and 48R) from the porcine experiment involving external actuation in accordance with an illustrative embodiment.

[0026] Fig. 14A depicts sensor results from a secure pedicle screw (i.e., not loose) in accordance with an illustrative embodiment.

[0027] Fig. 14B depicts sensor results from a loose pedicle screw in accordance with an illustrative embodiment.

[0028] Fig. 15A shows sensor results from a broken spinal rod in accordance with an illustrative embodiment.

[0029] Fig. 15B shows sensor results from a secure spinal rod (i.e., not broken) in accordance with an illustrative embodiment.

[0030] Fig. 16A shows sensor results from a secure (i.e., not loose) pedicle screw in accordance with an illustrative embodiment.

[0031] Fig. 16B shows sensor data results from a loose pedicle screw in accordance with an illustrative embodiment.

[0032] Fig. 17A depicts sensor results from a pedicle screw (loose screw and secure screw) while the porcine subject was playing in accordance with an illustrative embodiment.Atty. Dkt. No. 00100-0412-PCT

[0033] Fig. 17B depicts sensor results from a pedicle screw (loose screw and secure screw) during a standing action of a porcine subject, in accordance with an illustrative embodiment.

[0034] Fig. 18 is a block diagram of components included in a smart pedicle screw (or spinal rod) system in accordance with an illustrative embodiment.DETAILED DESCRIPTION

[0035] Pedicle screws, which are essential in neurological and orthopedic spine surgeries, are used to secure rods and other instruments to the pedicle of the spinal vertebra. Pedicle screws are commonly placed in vertebrae and are employed in procedures such as spinal fusion, tumor resection, deformity correction, and fracture repair. Other procedures in which pedicle screw s and / or spinal rods are used include posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), anterior lumbar interbody fusion (ALIF), spondylolisthesis correction, disc herniation surgery, scoliosis surgery, kyphosis correction, flatback syndrome correction, congenital spinal deformity’ correction, spinal fracture stabilization, burst fracture stabilization, chance fracture fixation, metastatic spinal tumor surgery, primary spinal tumor surgery, spinal osteomyelitis stabilization, pseudoarthrosis revision surgery, adjacent segment disease surgery, spina bifida correction, spondylolysis fixation, myelopathy stabilization, radiculopathy fusion, percutaneous pedicle screw placement, anterior-posterior fusion, vertebral column resection (VCR), pedicle subtraction osteotomy (PSO), rheumatoid arthritis stabilization, post-laminectomy instability stabilization, syringomyelia stabilization, cerebral palsy deformity correction, and failed back surgery syndrome revision.

[0036] The pedicle screws ty pically extend into pedicles of the vertebrae, which are the stacked bones that make up the spine. Fig. 1 depicts a vertebra in accordance with an illustrative embodiment. As shown, the vertebra includes a vertebral body, pedicles, facet joints, transverse processes, and a spinous process. Once the pedicle screws are anchored into the vertebral pedicles, they are typically connected to rods that run parallel to the spinal column. These screw s and rods are essential for restoring and maintaining spinal alignment, preventing further deformity, and facilitating spinal fusion. Their accurate placement is critical, as suboptimal fixation can lead to hardw are failure requiring revision surgery' and adding to patient morbidity.Atty. Dkt. No. 00100-0412-PCT

[0037] A major challenge with traditional pedicle screws is their tendency to gradually loosen or slip out of the vertebra, a process exacerbated in patients with comorbidities like osteoporosis. This slippage typically begins with microtrauma at the tip of the screw and progresses over time to loosen the entire shaft within the bone, a phenomenon known as haloing. Pedicle screws and rods can also fracture, the set screws securing the rod to the pedicle screws can loosen, or the head of the pedicle screw can detach from the shaft resulting in spinal construct failure. Failed constructs and screws pose severe risks to patients, often requiring emergent revision surgery, which is associated with increased surgical complexity, longer recovery time, heightened risks of nerve damage and infection, higher costs, and worse overall outcomes. Screws at the top and bottom of the instrumentation column are subjected to the most mechanical stress, and are thus most likely to fail.

[0038] Described herein is a pedicle screw sensor system that can be constructed as a smart pedicle screw or integrated into a commercial pedicle screw having a foramen or cannulation. The system is configured to detect movement or stability- changes of a pedicle screw, spinal rod, and / or set screws, which can be an early warning sign of implant failure. The proposed pedicle screw system does not directly influence screw placement, as smart pedicle screw insertion can be done through a wide variety of approaches ranging from freehand to navigated to robotic, with different surgeons and centers each having preferred approaches. One of the key functionalities of the proposed pedicle screw system is the early detection of screw slippage or microtrauma, which are early indicators of pedicle screw failure. Screw loosening is a common cause of hardware failure and often goes undetected until the patient presents with symptoms or follow-up imaging reveals hardware migration. At that point, major revision surgery is often required, which is associated with high healthcare costs, increased patient risk and worse outcomes, and prolonged recovery times. As discussed in more detail below, the proposed system can also be used to detect a breakage and / or movement of a spinal rod that is secured using pedicle screws.

[0039] Pedicle screws come in various shapes and sizes, designed to accommodate anatomical variations in patients. One design feature for the proposed system is a cannula (or foramen), which is a cylindrical hollow core that runs longitudinally through the center of the screw. Cannulated screws are often employed for percutaneous fixation and allow the insertion of bone cement or biologies for enhanced stabilization and fusion. Though cannulated screws are frequently used, traditional pedicle screws are not used in coordinationAtty. Dkt. No. 00100-0412-PCT with sensorized implants for fusion and slippage detection. In the present application, the cannula serves the purpose of housing sensor technology, which represents a significant advancement in real-time monitoring of pedicle screw integrity.

[0040] While the description herein largely focuses on pedicle screw s, it is important to understand that the proposed system is not limited to use in pedicle screws. The sensor system can also be used in other types of screws such as orthopedic cancellous bone screws, cortical bone screws, cannulated screws, leg screws, headless compression screws, or Herbert screws, locking screws, malleolar screws, hip screws, and bioabsorbable screws. These are all used in applications such as fracture fixation, bone fragment compression, intramedullary nailing, large joint, arthrodesis (or fusion), small joint arthrodesis (or fusion), osteotomy, soft tissue attachments including tendons and ligaments to bone, large joint replacement, small joint replacement, etc.

[0041] In an illustrative embodiment, the proposed pedicle screw system incorporates three or more t pes of sensors which are packaged into a single unit in order to detect early signs of screw loosening. In alternative embodiments, a single sensor or subset units may be used. The three sensors can include a vibroacoustic sensor, an inertial measurement unit (IMU), and a miniaturized temperature sensor (or thermometer). In one embodiment, the IMU can include an accelerometer, a gyroscope, and / or a magnetometer. Alternatively, the IMU may include just an accelerometer, or any combination of an accelerometer, gyroscope, and magnetometer. Traditional IMUs are large and may not fit into the cannula of a pedicle screw. However, recently developed IMUs are much smaller in size and there exist IMUs that are compact enough to fit within the cannula. Fig. 2 depicts various views of pedicle screws fixed to a standard rod in accordance with an illustrative embodiment. Also shown in Fig. 2 is the foramen (or cannula) of the pedicle screw, which is able to accommodate the sensors and other system components. Fig. 2 also includes a comparison of a traditional IMU to the world’s smallest IMU (dimensions 1 .2 x 0.8 x 0.55 mm2), and indicates that the smaller IMU is sized to readily fit within the cannula of the pedicle screw.

[0042] In an illustrative embodiment, the sensing unit (e.g., IMU, vibroacoustic sensor, and / or thermometer) of the smart pedicle screw7system are embedded within the foramen of the screw to detect early signs of instability, including microtrauma, slipping, or haloing. The sensors can be individually mounted within the foramen, or mounted within a drop-in unitAtty. Dkt. No. 00100-0412-PCT(described below) that is sized to fit within the foramen. The system can also include a sensing unit on the spinal rod and / or on the bone itself, as discussed in more detail below. In one embodiment, the system can also include subcutaneous implantable bioelectronics that provides wired or wireless power to the sensor unit and that receive data from the sensor(s). In one embodiment, the implantable bioelectronics can also perform data processing and use signal transmission to send alerts to a smartphone or other computing device, allowing for real-time monitoring and timely alerts from the pedicle screw. Alternatively, the implantable bioelectronics can send the received sensor data to the smartphone or other computing device for processing and alert generation. This capability facilitates early intervention to prevent complications, aiming to improve post-operative outcomes by reducing the need for revision surgeries and mitigating complications associated with emergency procedures.

[0043] In another illustrative embodiment, the sensor system includes a cylindrical drop- in sensor unit that is deployed within the cannula of the pedicle screw after screw insertion. The drop-in sensor unit strategically positions a high-fidelity vibroacoustic sensor, an IMU, and / or a temperature sensor at the distal tip of the screw, where biomechanical forces are most concentrated. As a result, the sensing unit is able to provide direct feedback on the mechanical stability of the screw-bone interface. In an illustrative embodiment, the drop-in sensor unit is housed within a bioencapsulated cylinder.

[0044] Fig. 3A is a side view of smart pedicle screws mounted to vertebrae in accordance with an illustrative embodiment. Fig. 3B is a lateral cross-sectional view of a mounted smart pedicle screw in accordance with an illustrative embodiment. As shown, the drop-in sensor unit (including the screw IMU, the vibroacoustic sensor, and the temperature sensor) is positioned at the distal end (i.e., at the screw tip) of the pedicle screw, and is connected to a wire that runs through the cannula and out the proximal end (i.e., the head of the screw) of the pedicle screw. The wire extends to a bioencapsulated power and transmission unit (monitoring unit) that is used to power the sensors and communicate with a remote device. Fig. 3C is a posterior view of a mounted pedicle screw system with smart pedicle screws in accordance with an illustrative embodiment. As discussed below, an alternative embodiment uses a wireless, externally mounted monitoring unit to interact with the sensor unit.

[0045] As shown in Fig. 3C, the pedicle screw system can also include a secondary component in the form of a rod-mounted sensor unit which can be secured to a spinal rodAtty. Dkt. No. 00100-0412-PCT using a clamp system. C clamps are used often in spine surgery to attach various instrumentation to spinal rods and, in one embodiment, a C clamp is used to affix the rod IMU in place. The rod sensor tracks dynamic movement and mechanical stress along the spinal rod and compares the data to the screw sensor to evaluate differences characteristic of failure. This is particularly valuable for detecting subtle, early signs of microtrauma or screw loosening, which may go unnoticed during routine follow-ups unless clinical symptoms emerge. In an illustrative embodiment, each pedicle screw of an implant system is independently monitored with its own sensors, while a single rod sensor and power unit can be sufficient to oversee the entire construct, regardless of how many screws are placed in the patient. In alternative embodiments, multiple rod sensors may be used (e.g., one sensor on each spinal rod used in an implant, multiple sensors on a single spinal rod, etc.). A bone mounted sensor unit (e.g., including an IMU, vibroacoustic sensor, and / or temperature sensor) may also be used to detect bone vibrations and temperature to assist with screw / rod monitoring.

[0046] As discussed above, in one embodiment, the proposed system utilizes a subcutaneously placed bioencapsulated power and transmission unit that communicates wirelessly with a remote interface via Bluetooth, Near-Field Communication (NFC), or another wireless technology. The remote interface can be a smartphone, a tablet, a laptop computer, a desktop computer, etc. Fig. 4 depicts the bioencapsulated power and transmission unit implanted in a patient in accordance with an illustrative embodiment. As shown, in this embodiment the single bioencapsulated power and transmission unit is wired to each of the pedicle screw s (with sensors) and to the sensing unit positioned on the spinal rod. The bioencapsulated power and transmission unit provides sensor data from the sensors to an application on a remote device. The transmission of signals from each pedicle screw to an application on the remote device allows real-time monitoring of screw integrity, providing critical data for both patient and clinician.

[0047] The powder and transmission unit (or monitoring unit), which is morphologically low-profile to minimize discomfort, can be surgically implanted in the lower back or any appropriate location that is accessible for future maintenance or wireless charging. In one embodiment, the power unit enables inductive charging through a charging pad placed on the skin and eliminates the need for battery replacement or additional invasive procedures. In an alternative embodiment, the system utilizes a Near-Field Communication (NFC)-basedAtty. Dkt. No. 00100-0412-PCT wireless power harvesting system to convert ambient radiofrequency (RF) energy into usable electrical power. A rectifying antenna (rectenna) optimized for the 13.56 Megahertz (MHz) frequency band, commonly used in NFC protocols, is included. Radio frequencies above 1 MHz and below 20 MHz, such as the 13.56 MHz band, can penetrate body tissues efficiently, ensuring reliable power delivery to the implanted device. NFC technology also minimizes the risk of tissue heating and avoids interference with biological processes, making it safe for medical implants. In one embodiment, the sensors can be configured to transmit only at certain times (e.g., when power is applied to the system via a charging pad or another signal) to conserve power. In such an embodiment, a solid-state memory (e.g., installed on the power and transmission unit) can be used to store the sensory data until the time of transmission.

[0048] Fig. 5 depicts components of the power and transmission unit in accordance with an illustrative embodiment. As shown, the unit is bioencapsulated with parylene-ecoflex to help protect the electronic components. In one embodiment, to create a biocompatible, reliable barrier for the active electronics, the unit is protected through a two-step encapsulation strategy. First, a 50 pm- thick parylene coating (e.g., Special Coating Systems, Parylene C) is applied via chemical vapor deposition to form a robust water barrier. Subsequently, the device is encapsulated with soft, medical-grade silicone (e.g., Ecoflex 00- 30, Smooth-On, Inc.) to create a smooth, non-irritating surface suitable for long-term implantation. This encapsulated sensory component is designed to be integrated into any commercially-available pedicle screw with a foramen, ensuring universal compatibility. In some embodiments, the sensors and helical wires within the screws foramen are secured in place with bone cement. In alternative embodiments, different biocompatible materials and / or a different process may be used for encapsulation.

[0049] Components of the power and transmission unit are installed on a flexible printed circuit board (PCB), as shown. Specifically, a lithium-ion rechargeable battery is used to power the monitoring unit and the pedicle screws sensors. A Bluetooth system on a chip (SoC) is used for wireless communication, along with a NFC antenna. In alternative embodiments, a different type of battery' and / or communication protocol can be used. The power and transmission unit also includes a temperature sensor, such as a NIST-certified Texas Instruments TMP1 19 temperature sensor. Alternatively, a different type of temperature sensor may be used. The temperature sensor can be positioned within the power and transmission unit to monitor local tissue temperature changes, providing an early w arning ofAtty. Dkt. No. 00100-0412-PCT potential inflammation due to infection, system failure, etc. In one embodiment, a temperature sensor can also be incorporated into the sensor unit that is placed into the foramen of the pedicle screw.

[0050] Fig. 6A is a cross-sectional side view of a mounted pedicle screw system in accordance with an illustrative embodiment. Fig. 6B is a posterior side view of a mounted pedicle screw system in accordance with an illustrative embodiment. In this embodiment, the pedicle screw is a smart pedicle screw equipped with an IMU, vibroacoustic sensor, and a thermometer. In one embodiment, every other pedicle screw positioned along the spine can be a smart pedicle screw. In another embodiment, only the uppermost and lowermost pedicle screws may be smart pedicle screws. In alternative embodiments, every pedicle screw used on a patient may be a smart pedicle screw. In practice, the physician can determine how many smart pedicle screws to use and where to position them on the patient, depending on the type of procedure being performed, the characteristics of the patient, the overall condition of the vertebrae, etc. The smart pedicle screw of Fig. 6A includes a vibroacoustic sensor, temperature sensor, and a first IMU within the foramen of the screw. In Fig. 6B, a second IMU is mounted on the spinal rod via a clamp, which in turn is connected to the pedicle screws, and a third IMU is mounted into the bone directly. All of the pedicle screw sensors and the second and third IMUs are wired to the bioencapsulated power and transmission unit, which can be mounted subcutaneously as discussed above.

[0051] Regarding specific system components, in one embodiment the IMUs can be an ultra-compact Bosch BMA580 3-axis accelerometer IMU (1.2 x 0.8 x 0.55 mm3). As discussed, a first IMU is inserted into the internal foramen as part of the cylindrical sensing unit and extends to the tip of the pedicle screw', and a second sensing unit containing a second IMU is mounted on the spinal rod or the lamina of the spine. The first and second IMUs can be the same type of IMU (e.g.. the BMA580) or different types of IMUs. depending on the embodiment. The vibroacoustic sensor (i.e., microphone) can be a Knowles V2S200D digital voice vibration sensor which is also attached to the end of the pedicle screw'. Both sensors leverage high-performance microelectromechanical systems (MEMS) technology for ultra- high sensitivity and a favorable signal-to-noise ratio (SNR). In alternative embodiments, different types of IMUs and / or vibroacoustic sensors may be used.Atty. Dkt. No. 00100-0412-PCT

[0052] In one embodiment, at the core of the data transmission unit is a Nordic nRF5340 Bluetooth Low Energy (BLE) 5.4 system-on-a-chip (SoC). The advanced dual-core Cortex- M33 microprocessor built in the nRF5340 SoC ensures robust data transmission for large- scale data collection, essential for training personalized machine learning models to detect a loose smart pedicle screw. The processor is also capable of running onboard Edge Al for automatic detection of screw loosening and sending alerts to a remote application or device, notifying the patient. In alternative embodiments, a different type of Bluetooth chip and / or processor may be used. The wires used to connect system components can be flexible helical coil stainless steel wires, providing robust mechanical performance and long-term implantation stability. In one embodiment, the high-speed Serial Peripheral Interface (SPI) protocol or the Inter-Integrated Circuit (I2C) protocol can be used for communication with IMU sensors, and the Pulse Density Modulation (PDM) protocol can be used for communication with vibroacoustic sensors, utilizing separate clock and data lines to minimize signal degradation and crosstalk.

[0053] In an illustrative embodiment, the system components work in tandem to detect the earliest signs of mechanical degradation. In one embodiment, vibroacoustic sensing captures soundwaves emitted from microfractures, or screw-bone interface movement, or subtle shifts in screw positioning; additionally, the IMU detects changes in angular displacement, velocity, and acceleration which can be diagnostic of screw loosening; additionally, the temperature sensor detects changes in temperature characteristic of infection, heat generation from friction, or low-grade inflammation. In practice, the drop-in sensor unit can be delicately inserted into the cannula and positioned near the distal tip of the pedicle screw during an initial spinal surgery, ensuring that it captures biomechanical forces acting on the screw-bone interface. After sensor placement, the remaining cannula space can be filled with biocompatible epoxy or resin or bone cement, such as polymethylmethacrylate, calcium phosphate cement, polyalkenoate cement, acrylic cement, or calcium sulfate cement. This ensures the sensor remains securely positioned while further stabilizing the screw and protecting the winng from external forces.

[0054] The IMU and / or vibroacoustic sensor captures microfractures, screw-bone interface motion, and subtle shifts in screw positioning by monitoring deviations in vibrational or acoustic frequency profiles from a post-operative baseline or in response to externally applied excitation. The IMU can also track relative angular displacement andAtty. Dkt. No. 00100-0412-PCT linear acceleration, with deviations from expected mechanical behavior signaling potential screw loosening. The temperature sensor detects temperature changes which are typically stable in a healthy vertebra and consequently changes could reflect infection, inflammation, or friction which may indicate early hardware failure. It is expected that movement of the screw tip will be detectable prior to movement of the rod and other portions of the implant. As such, detecting movement at the screw tip (while sensing no movement of the rod) can be an early indicator of a problem. Similarly, detecting movement of both the screw tip and the rod can indicate a more advanced problem with the implant. Failure thresholds can be established by comparing these sensor readings to pre-defined baselines. For instance, a 10% increase in vibration frequency or a 5-degree rotational shift could indicate microtrauma or instability. In alternative embodiments, different thresholds may be used, such as a 7%, 8%, 9%, 12% etc. increase in vibration frequency and / or a 3-degree. 4-degree, 6-degree, etc. rotational shift as the basis for indicating microtrauma or instability.

[0055] In an illustrative embodiment, the remote device (e.g.. smartphone) includes an application installed thereon that communicates with the power and transmission unit. During the data collection phase, the application software can function as a hub for reliable data acquisition, utilizing advanced algorithms to enable real-time display (e.g., on a device screen or display) of sensor signals and data storage for subsequent machine learning model training. In the patient deployment phase, the application software can be responsible for generating timely alerts for potential complications. The application can also include signal processing algorithms that filter noise and analyze the vibroacoustic and IMU data in real-time, allowing for the identification of early failure patterns. Machine learning classification models including Random Forest and Logistic Regression can be integrated to classify these signals and predict hardware failure based on historical data, refining detection accuracy over time. By fusing data from multiple sensors and cross-referencing patient activity levels, the system provides robust, real-time monitoring. This approach allow s for earlier detection of screw7failure, potentially preventing costly revision surgeries and improving patient outcomes.

[0056] In the event that screw failure, loosening, or other movement is detected, the application can send an alert (e.g., a text message, an e-mail, a phone call, an audible alarm, etc.) to warn the physician and / or the patient. In another embodiment, the application software can conduct the automated signal analysis required to detect screw loosening and can also interface with an EHR (electronic health record) of the patient to directly flag / wamAtty. Dkt. No. 00100-0412-PCT the patient’s doctors of an identified problem. The application not only collects and analyzes data but also allows for inter-screw crosstalk, adding an additional layer of diagnostic capability. By cross-referencing data from multiple pedicle screws, the system can assess the overall structural integrity of the spinal construct. Data from the app may be licensable or stored in an electronic data warehouse for research purposes. The data could also be used to train instrument failure detection platforms for other bodily implant systems.

[0057] In an alternative embodiment, the pedicle screw sensor system can be fully housed within the body of a pedicle screw without the need for a wire or subcutaneous electronics, can be externally powered via a wearable battery belt, and can communicate sensed information wirelessly to an external unit (computing device). Sensor readings can be collected intermittently and thus only periodic donning of the powered belt and external unit is necessary to detect hardware instability. The powered belt can transfer wireless power via an alternating current transmitter coil to produce an electromagnetic field into to the patient’s tissues which is then captured by one or more receiving coils (mounted within the sensor unit) and rectified with a rectifier (within the sensor unit) to direct current. The external unit can perform data processing and generate alerts if a problem is detected. Alternatively, the external unit can communicate with a remote device that performs data processing. Fig. 7 shows a system in which power and data are wirelessly transmitted between a smart pedicle screw and an external unit in accordance with an illustrative embodiment. In one embodiment, the external unit can be worn on a harness by a user such that the harness positions the external unit proximate to the smart pedicle screws. As shown, data (e.g., sensor readings) is wirelessly transmitted from the smart pedicle screw' to the external unit and power is wirelessly transmitted from the powered belt to the smart pedicle screw.

[0058] Fig. 8 depicts a user wearing a pow ered wearable belt that conveys wireless power and data communication to the in-screw sensing units and holds an external unit in accordance with an illustrative embodiment. As shown, the user positions the powered belt and external unit along the spine such that they are close to the implanted smart pedicle screw (s) and / or rod sensor(s). In this embodiment, the external unit w irelessly communicates with a remote computing device such as a smart phone. Accordingly, the smart phone (or other computing device) can include an application that processes received data and issues alerts in the event of a detected problem. In the embodiment shown, wireless communicationAtty. Dkt. No. 00100-0412-PCT is via Bluetooth, however, other communication algorithms can be used in alternative embodiments.

[0059] Fig. 9 depicts another embodiment of a computing device connected to a smart pedicle screw sensors in accordance with an illustrative embodiment. As shown, the computing device includes an onboard IMU, connections for connecting to a plurality of IMU probes, a battery management integrated circuit, onboard storage, and a communication interface (Bluetooth 5.4 SoC). In alternative embodiments, the computing device can include fewer, different, and / or additional components. The computing device is connected to an IMU sensor probe that is sized to be positioned in the screw foramen. A vibroacoustic sensor is also attached to the probe and sized to be positioned in the pedicle screw foramen. Fig. 10 depicts the sensor probe mounted within the screw foramen in accordance with an illustrative embodiment. In this embodiment the probe is show n as a sharp tip that extends outward from the pedicle screw' through its foramen (for illustrative purposes). In practice the probe or drop-in sensor unit can be fully contained within the foramen.

[0060] As discussed, in an illustrative embodiment a temperature sensor can be incorporated into the pedicle screw or the sensor probe that mounts within the pedicle screw. The ultra-high-sensitivity temperature sensor can be used to detect elevated temperature to detect infection, to detect elevated temperature resulting from friction, etc. Fig. 11 depicts a sensor unit for a pedicle screw that includes an IMU and a temperature sensor in accordance with an illustrative embodiment.

[0061] Use of the pedicle screw sensor system to detect loosening and other issues is described in more detail below. In one embodiment, a detection mode utilizes externally applied mechanical actuation. In such an embodiment, an external actuator (e.g. vibration motor, magnetic transducer, acoustic driver, or mechanical tapping device) is positioned on the skin above the spinal segment containing the target pedicle screws. The actuator delivers a controlled vibrational stimulus at one or more frequencies in a defined range (e.g. 100 Hz constant excitation or 0-500 Hz sweeping) designed to induce structural resonance within the screw-bone interface. The vibration propagates through skin, soft tissue, and spinal bone and into the screw', with transmission characteristics dependent on the fixation condition of the screw; The sensor system positioned within the pedicle screw detects these vibrations, andAtty. Dkt. No. 00100-0412-PCT the characteristics of the detected response (e.g., amplitude, harmonic composition, or damping behavior) are analyzed to determine the fixation condition of the pedicle screw.

[0062] The implanted sensor, positioned within the cannulation of the pedicle screw, detects vibrational responses produced by the external actuation. The recorded sensor data are analyzed to compute (1) primary resonance amplitude at the excitation frequency, (2) harmonic content generated by nonlinear screw motion, and (3) damping and bandwidth parameters indicative of mechanical coupling between bone and screw.

[0063] In a fully secured pedicle screw, the pedicle screw behaves as a rigidly coupled structure, producing a narrow, high-efficiency resonance response with minimal harmonic generation. In contrast, when the screw becomes loosened, micro-motion develops at the screw-bone interface, producing nonlinear vibration behavior characterized by (i) reduced amplitude at the fundamental excitation frequency, (ii) emergence of broadband and harmonic components (e.g., at 2x - 4x the excitation frequency), and (iii) a reduced quality factor (Q) and increased bandwidth due to energy dissipation from rattling, frictional slip, and other non-rigid interactions. These spectral changes provide a mechanical signature of loosening that can be quantified automatically.

[0064] This method of using external actuation has been validated in a live porcine spinal model to demonstrate accurate assessment of pedicle screw fixation under physiological loading conditions over the course of twelve weeks. Fig. 12 depicts a porcine surgery to test the pedicle screw sensor system in accordance with an illustrative embodiment. As shown, the experiment includes an intentionally broken spinal rod, and screws that were intentionally loosened. Specifically, the setup included two pedicle screws with broken rods, two screws intentionally loosened, and four intact screws to act as controls. To conduct the experiment, external vibration was applied through skin and subcutaneous tissue, and the implanted sensor in the cannulated screw captured the screw response. Loosening was selectively- induced in specific screws while others were preserved as controls. Mechanical inspection confirmed fixation status, and the resulting vibrational signatures distinctly differentiated stable screws from loosened screws using the above-described spectral and damping metrics.

[0065] Fig. 13 shows sensor results for two screws (48L and 48R) from the porcine experiment in accordance with an illustrative embodiment. Specifically, Fig. 13 is a data snapshot of normal daily activity in the porcine experiment. Fig. 14A depicts sensor resultsAtty. Dkt. No. 00100-0412-PCT from a secure pedicle screw in accordance with an illustrative embodiment. Fig. 14B depicts sensor results from a loose pedicle screw in accordance with an illustrative embodiment. The test results also verified that the pedicle screw sensor system can identify a broken spinal rod. Fig. 15A shows sensor results from a broken spinal rod in accordance with an illustrative embodiment. Fig. 15B shows sensor results from a control spinal rod (i. e. , not broken) in accordance with an illustrative embodiment. The circles on the frequency vs. power spectral density (PSD) charts show a distinct difference in frequency between the broken spinal rod and the control spinal rod. The test results further verified that the pedicle screw system can identify a loose screw. Fig. 16A shows sensor results from a control (secure) pedicle screw in accordance with an illustrative embodiment. Fig. 16B shows sensor data results from a loose pedicle screw in accordance with an illustrative embodiment.

[0066] The inventors also tested the proposed system for detection of pedicle screw loosening during daily activity Fig.13. Mechanical vibrations generated naturally during daily activities (including standing, breathing, ambulating, posture changes, or muscular contraction) propagate through spinal tissue and into pedicle screws implanted within a vertebra. These physiological forces excite the screw-bone interface without the need for an applied external actuator. An implanted sensor within the cannulation of the pedicle screw detects these activity -induced vibrations. The recorded signal contains characteristics influenced by the rigidity' of screw fixation, allowing the system to determine screw stability based on the screw’s dynamic response under normal physiological loading.

[0067] The sensed vibration data are processed to extract (1 ) fundamental spectral energy associated with natural motion, (2) harmonic components and broadband signatures generated by nonlinear oscillation of a loosened screw, and (3) damping characteristics and spectral bandwidth indicative of mechanical coupling between bone and screw. A firmly fixated pedicle screw exhibits a rigid mechanical coupling to bone, resulting in efficient energy transfer when excited by physiological motion. This produces a narrow spectral response with limited harmonic distortion. A loosened screw undergoes micro-motion relative to surrounding bone, generating nonlinear vibrational behavior and energy dissipation, which manifests as (a) increased harmonic and broadband spectral content, (b) reduced amplitude at the dominant physiological frequency, and (c) a lower qualify factor (Q) or broadened spectral peak. These naturally -induced spectral features serve as diagnostic indicators of screw loosening, eliminating the need for external mechanical stimulation.Atty. Dkt. No. 00100-0412-PCT

[0068] The method has been validated in a live porcine spine under normal physiologic behavioral activity, including standing, sitting, walking, postural shifts, and playful motion, etc. Vibrational energy transmitted through skin and vertebra produced distinct sensor signatures according to screw fixation state. Select screws were mechanically loosened while others remained secure. The recorded signals demonstrated clear spectral disparities between loose and secure screws based on harmonic intensity, spectral slope, and damping response, confirming reliable classification of loosening using only daily physiological activity. Fig. 17A depicts sensor results from a pedicle screw (loose screw and tight screw) while the porcine subject was playing in accordance with an illustrative embodiment. Fig. 17B depicts sensor results from a pedicle screw (loose screw and tight screw) while the porcine subject was standing in accordance with an illustrative embodiment.

[0069] Fig. 18 is a block diagram of components included in a smart pedicle screw (or spinal rod) system in accordance with an illustrative embodiment. Specifically, Fig. 18 shows a smart pedicle screw (or spinal rod) 1850 in communication with an intemal / extemal monitoring unit 1875, which in turn is in communication with a computing device 1800. As shown, the smart pedicle screw 1850 includes an IMU 1855, a vibroacoustic sensor 1860, and a temperature sensor 1865. In alternative embodiments, the smart pedicle screw 1850 can include few- er or additional sensors and / or additional components such as a processor, memory, network interface, battery, etc. In an illustrative embodiment, the intemal / extemal monitoring unit 1875 is an external unit that is wirelessly connected to the smart pedicle screw' 1850 and used to receive data from the IMU 1855, the vibroacoustic sensor 1860, and the temperature sensor 1865. The external monitoring unit 1875 can also wirelessly send power to the smart pedicle screw 1850 to power the sensors incorporated therein. As discussed above, the external monitoring unit can be worn by the user such that it is positioned as close as possible to the smart pedicle screw 1850. The monitoring unit 1875 includes a processor 1880, a memory 1885, a battery' 1890, and a network interface 1895. In alternative embodiments, the monitoring unit 1875 can include fewer, additional, and / or different components. In an alternative embodiment, the intemal / extemal monitoring unit 1875 can be an internal monitoring unit. In such an embodiment, the internal monitoring unit may communicate with the smart pedicle screw71850 through a w ired connection, as discussed herein.Atty. Dkt. No. 00100-0412-PCT

[0070] The computing device 1800 is in communication with the monitoring unit 1875 and receives the sensor data therefrom for processing to determine if there are any problems with the smart pedicle screw (or spinal rod) 1850. The computing device 1800 can be a smartphone, a laptop computer, a desktop computer, etc. In an alternative embodiment, the monitoring unit 1875 can process the sensor data and generate alerts as needed such that the computing device 1800 may be excluded from the system. The computing device 1800 includes a processor 1805, an operating system 1810, a memory 1815, an input / output (I / O) system 1820. a network interface 1825, and a pedicle screw application 1835. In alternative embodiments, the computing device 1800 may include fewer, additional, and / or different components. The components of the computing device 1800 communicate with one another via circuit board traces, one or more buses, or any other interconnect system.

[0071] The processor 1805 of the computing device 1800 can be in electrical communication with and used to perform any of the operations described herein, such as receiving sensed data, processing the gathered data, sending data to a user device or other external systems, generating alerts or instructions, etc. The processor 1805 can be any type of computer processor known in the art, and can include a plurality of processors and / or a plurality of processing cores. The processor 1805 can include a controller, a microcontroller, an audio processor, a graphics processing unit, a hardware accelerator, a digital signal processor, etc. Additionally, the processor 1805 may be implemented as a complex instruction set computer processor, a reduced instruction set computer processor, an x86 instruction set computer processor, etc. The processor 1805 is used to run the operating system 1810, which can be any type of operating system.

[0072] The operating system 1810 is stored in the memory 1815, which is also used to store programs, algorithms, network and communications data, peripheral component data, the pedicle screw application 1835, and other operating instructions. The memory 1815 can be one or more memory systems that include various types of computer memory such as flash memon, random access memory' (RAM), dynamic (RAM), static (RAM), a universal serial bus (USB) drive, an optical disk drive, a tape drive, an internal storage device, a non-volatile storage device, a hard disk drive (HDD), a volatile storage device, etc.

[0073] The I / O system 1820, or user interface, is the framework which enables users (and peripheral devices) to interact with the computing device 1800. The I / O system 1820 canAtty. Dkt. No. 00100-0412-PCT include one or more keys or a keyboard, one or more buttons, a speaker, a microphone, a display, etc. The I / O system 1820 allows the user to interact with and control the computing device 1800. The I / O system 1820 can also include circuitry and a bus structure to interface with and control peripheral computing components such as one or more power sources, etc.

[0074] The network interface 1825 includes transceiver circuitry (e.g., a receiver and / or a transmitter) that allows the computing device 1800 to transmit and receive data to / from other devices such as the monitoring unit 1875. The network interface 1825 enables communication through a network, which can be one or more communication networks. The network can include a cable network, a fiber network, a cellular network, a Wi-Fi network, a landline telephone network, a microwave network, a satellite network, etc. The network interface 1825 also includes circuitry to allow device-to-device communication such as NearField communication (NFC), Bluetooth® communication, etc.

[0075] The pedicle screw application 1835 can include software and algorithms (e.g., in the form of computer-readable instructions) which, upon activation or execution by the processor 1805, performs any of the various operations described herein such as activating sensors, recording sensed data, processing the sensed data to determine information regarding the pedicle screw or spinal rod, transmitting sensed data and / or processed information to a user device, generating alerts based on the analyzed data, etc. The pedicle screw application 1835 can utilize the processor 1805 and / or the memory 1815 as discussed above.

[0076] The smart pedicle screw system adds value for patients by addressing the critical unmet need of early screw loosening detection, which can lead to costly and complex revision surgeries associated with worse patient outcomes. Spinal surgeries generally receive high rates of reimbursement by insurance companies provided that patients try and fail conservative medical alternatives, including steroid injections and physical therapy. With the global spinal implants and devices market expected to reach $18.7 billion by 2027, this innovation positions itself as a valuable tool for improving patient outcomes and reducing healthcare costs, and is poised to be commercially viable from a market analysis and reimbursement standpoint.

[0077] In addition to the uses already discussed, deidentified and HIPAA-compliant vibroacoustic and IMU sensor data can be licensed to medical device companies aiming to drive innovation that further improves detection of pathologies. Data from smart screwAtty. Dkt. No. 00100-0412-PCT sensors can be used to train algorithms which predict other pathologies within the spine and central nervous system. Data can be used in tandem with other smart implants, such as sensorized vertebral cages, to provide better early monitoring of instrumentation failure. Data can also be analyzed by academic researchers to identify if specific features of the recorded signals are independently predictive of other medical conditions.

[0078] Intraoperative use cases of Smart screws are reasonable as well. If powered on and compatible with the drill apparatus, the vibroacoustic and IMU sensors can be trained to aid the surgeon in screw placement, ensuring that breach is avoided. Data can be steamed in real time to optical recognition (OR) visualization software, or even directly to robotic platforms. The robotic placement of pedicle screws is the most common application of robotics in neurosurgery. Sensorized screws would only provide further control and accuracy for a robotic screw placing system. Additionally, during or after pedicle screw insertion, stress can be applied to the system to verify that the mounted implant is sturdy and not prone to movement. If any movement is detected, a correction can be made during the initial surgery, which helps avoid the need for subsequent procedures.

[0079] Furthermore, the potential for integration of the proposed system with electronic health records adds tactical value, making the system an attractive option for neurosurgeons and orthopedic surgeons aiming to streamline post-operative care in such a way that interfaces with other healthcare providers as other early detectors of screw failure. Outpatient facilities, including physical therapy clinics, can detect and warn patients about early signs of screw failure without substantial training as the software handles the signal analysis.Subacute changes in sensor outputs can be monitored by outpatient healthcare providers over time as well.

[0080] In summary, as discussed herein, the smart pedicle screw system provides continuous real-time feedback and aims to improve screw failure detection. Specifically, the system can be used to detect the earliest signs of pedicle screw loosening, detect the earliest signs of set screw loosening, detect the earliest signs of rod breakage, and detect the earliest signs of pedicle screw fracture. Detecting impending screw failure before clinical symptoms arise allows for earlier, more targeted interventions, reducing the likelihood of full hardware failure, improving patient outcomes, and reducing the need for costly and complex revision surgeries. The system is versatile enough to be used across a wide variety of spinalAtty. Dkt. No. 00100-0412-PCT pathologies, from trauma to degenerative disease and even oncological resections requiring spinal stabilization. The smart pedicle screw system is the first of its kind in spinal fixation hardware, and offers promise to transform post-operative monitoring for spine patients. The proposed smart pedicle screw system integrates cutting-edge sensor technology’ into the current surgical workflow without needing new instrumentation. This system is designed to work with the most widely used cannulated pedicle screws, including those from major manufacturers such as Medtronic, DePuy, and Stry ker.

[0081] The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more.”

[0082] The foregoing description of illustrative embodiments of the invention has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims

Atty. Dkt. No. 00100-0412-PCTWHAT IS CLAIMED IS:

1. A screw system comprising: a screw that has a foramen, wherein the screw includes an inertial measurement unit mounted within the foramen of the screw and configured to detect movement of the screw; and a monitoring unit in communication with the inertial measurement unit, wherein the monitoring unit transmits data from the inertial measurement unit to a remote application.

2. The system of claim 1, wherein the remote application processes the data from the inertial measurement unit to identify movement of the screw.

3. The system of claim 2. wherein the remote application compares the identified movement of the screw to a movement threshold.

4. The system of claim 3, wherein the remote application generates an alert if the identified movement of the screw exceeds the movement threshold.

5. The system of claim 1, wherein the inertial measurement unit is mounted within a drop-in sensor unit that is sized to fit within the foramen of the screw.

6. The system of claim 5, wherein the drop-in sensor unit is encapsulated in a biocompatible material.

7. The system of claim 1. wherein the inertial measurement unit is positioned at a distal end of the screw.

8. The system of claim 1, wherein a spinal rod is connected to the screw, and further comprising a second inertial measurement unit mounted to the spinal rod.

9. The system of claim 8, wherein the monitoring unit is in communication with the second inertial measurement unit and transmits data from the second inertial measurement unit to the remote application.Atty. Dkt. No. 00100-0412-PCT10. The system of claim 1 , further comprising a temperature sensor mounted within the monitoring unit.

11. The system of claim 10, wherein the monitoring unit is subcutaneously placed in a patient, and wherein the temperature sensor detects a temperature of the patient and provides the temperature to the remote application.

12. The system of claim 11, wherein the remote application monitors the temperature to identify a temperature increase that is indicative of inflammation or infection.

13. The system of claim 1, wherein the monitoring unit is externally mounted on a patient, and wherein the monitoring unit receives the data wirelessly.

14. The system of claim 1, wherein the monitoring unit comprises a powered belt that wirelessly provides power to the inertial measurement unit.

15. The system of claim 1 , further comprising a vibroacoustic sensor mounted within the foramen of the screw and configured to detect vibrations of the screw.

16. The system of claim 1. further comprising a temperature sensor mounted within the foramen of the screw and configured to detect temperature changes within and around the screw.

17. A method of making a smart screw system, the method comprising: mounting an inertial measurement unit mounted within a foramen of a screw such that the inertial measurement unit detects movement of the screw; and positioning a monitoring unit in communication with the inertial measurement unit, wherein the monitoring unit transmits data from the inertial measurement unit to a remote application.

18. The method of claim 17, further comprising mounting a vibroacoustic sensor within the foramen of the screw.Atty. Dkt. No. 00100-0412-PCT19. The method of claim 18, further comprising mounting a temperature sensor within the foramen of the screw.

20. The method of claim 19. further comprising placing the inertial measurement unit, the vibroacoustic sensor, and the temperature sensor into a drop-in sensor unit that is sized to fit within the foramen of the screw, and encapsulating the drop-in sensor unit in a biocompatible material.

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