Smart Implants in Orthopaedics

Verasense

Verasense is a sensor-based device used in Total knee arthroplasty (TKA). It has been developed by OrthoSensor Inc. The device delivers data wirelessly to an intra-operative monitor that enables surgeons to make informed decisions regarding implant position and quantify soft-tissue balance to improve knee balance and stability through the range of motion. The use of this device does not affect the surgeon’s work flow. Once the knee implant is positioned, the surgeon places VERASENSE into the tibial tray and examines the mediolateral loading values. This real-time data forms the basis for adjustments that the surgeon makes to arrive at a better-balanced knee.

Using VERASENSE saves money for the patient by lowering variable post-operative and post-acute care.

Reverse Total Shoulder Sensor

OrthoSensor is also working on the development of a new intraoperative sensor trial to assist balancing during reverse total shoulder arthroplasty, showing sufficient accuracy and promising insights into impingement, stability and mobility. However, USFDA clearance for this is still pending and it is not available for commercial sale yet.

Sensor For The Spine

Intellirod Spine has developed LOADPRO and ACCUVISTA. LOADPRO is an intraoperative Rod Strain Sensor. It is a single-use device that allows spine surgeons to balance strains on implanted fusion rods during operation. ACCUVISTA is a post-operative Rod Strain Sensor, a permanent device that allows rod strains to be tracked after spine fusion. These devices measure spinal rod strain and simultaneously communicate left versus right rod strain asymmetry to an external reader during corrective surgical manoeuvres.

Bonetag

BoneTag, a unique and universal RFID device, encapsulated in a biocompatible casing which is about the size of a SIM card. Placed inside knee prostheses, it enables communication with all brands of surgical orthopaedic implants by connecting them and making them smart. The physician has to scan the patient’s knee to read the information transmitted by the device to the dedicated BoneTag software.Bonetag was selected by Bpifrance, the General Commissariat for Investment and SATT Network as a high potential candidate for investment. AXLR SATT under partnership with BoneTag associates developed the said RFID device.

BoneTag fulfils three key functions starting from the moment it is integrated into a knee prosthesis, during the surgical procedure:

Research Institutes/ Universities Working On Smart Implants

Wireless Sensors For Smart Orthopaedic Implants

Other developments that are in progress include orthopaedic implants with wireless communication capabilities for a) detection of loosening for hip implants, (b) force measurements in knee implants, (c) bone healing assessment, (d) wireless correction of orthopaedic structural deformities, (e) temperature measurements for hip implants, (f) measurement of contact forces and moments in the shoulder joint, (g) diagnosis of orthopaedic implant failures, (h) spinal fusion monitoring, etc.

The Department of Electrical and Computer Engineering at The Ohio State University, in a publication, describes the concept of vibrometry which is employed to unobtrusively detect hip implant loosening. There is an insert containing wireless piezoresistive strain sensors which is tested in a mechanical knee simulator that is mimicked under in vivo condition. To assess the bone healing, load measuring electronics has been integrated into the orthopaedic implants. The study demonstrates the wireless telemetry system to measure the bending load in the internal femur.

Recent advances in wireless health care, miniaturized sensors, and wireless powering have indeed enhanced the capabilities of orthopaedic implants by integrating smart functionalities. However, several challenges still remain to be resolved, such as the reliability of the wireless communication link, miniaturization, unobtrusive powering, the ability to achieve stand-alone operation without requiring constant supervision, good measuring accuracy, affordability, low rates of implant failures, animal testing, etc.

Smart Bone Plates That Can Monitor Fracture Healing

In a recent study, scientists at the Department of Bioengineering and Orthopaedics at the University of California, San Francisco (UCSF), used in vivo mouse fracture models to present primary evidence of microscale smart bone plate implants. These implants were able to monitor post-operative fracture healing with high sensitivity using electrical impedance spectroscopy (EIS) integrated to track the healing tissue. In a first, the scientists fixed long bone fractures in a mouse, with external fixtures and bone plates containing the sensor, in an experimental study in the lab. The results have been published in scientific journals.

In the study, EIS measurements were conducted across two microelectrodes in the fracture gap, to track longitudinal differences in mice with good versus poor healing. The scientists presented an equivalent circuit model that combined the EIS data, so as to differentiate the states of fracture repair. Their measurements, which strongly correlated with standard qualitative X-ray microtomography (microCT) values, allowed the frequency-based technique to validate clinically relevant operating frequencies. The results pointed towards the possibility of EIS being combined into existing clinical fracture management strategies such as bone plating. The process developed in the study can ultimately provide physicians quantitative information on the state of fracture repair in patients to guide clinical decision-making.

Smart, Self-Powered Knee Implants

Scientists at Binghamton University, University of Western Ontario and State University of New York determined that their new smart, self-powered implant needs 4.6 microwatts to function and preliminary testing showed that the average person’s walk produces six microwatts of power, more than enough to power the sensors. The new implant geometry comprises two ridge-shaped surfaces which rub against one another when a person walks. The frictional sliding that occurs as a result transfers electron from one surface to another, which provides the self-powered charge to the implant. The sensors allow doctors to guide patients when a certain movement has a high impact on the implant so that patients can quickly adjust and avoid damage to the implant.

Rather than using a battery that would add weight to the implants and require periodic replacement, the scientists opted to use an energy harvesting mechanism that powers the knee implant using the patient’s motion. An energy harvesting prototype using triboelectric energy, or energy collected from friction under a mechanical testing machine, was tested to examine its output under equivalent body loads. The harvester prototype was placed between the tibial component and polyethylene bearing of the knee replacement implant. Continual monitoring of knee loads after surgery offers the potential to improve surgical procedures and implant designs.

Smart Implant For Orthopaedics Surgery (SImOS – a Nano-Tera Project)

Nano-Tera projects are cooperatively organised engineering projects that aim to analyse and develop innovative systems featuring small-scale components (micro- and nanoscale) and systems comprising very large data sets (tera). The goal of the select Nano-Tera project was to design a system to measure biomechanical parameters of a knee prosthesis. The system comprises partly implanted and partly external tools that could help the surgeons during surgery and the rehabilitation and thereby increase the quality of life of the patients. The system helps in estimation of imbalance in medial-lateral ligaments based on force measurements and estimation of loosening of the prosthesis through measurement of kinematics. Also, this would help in measuring the other biomechanical forces acting on the prosthesis, including joint angles and translation motions.

1. US20180140251– SMART JOINT IMPLANT SENSORS

   The invention from Zimmer Inc. relates to a prosthesis for implantation into a mammalian body with a sensor array comprising multiple sensors mounted to the prosthesis configured to measure pressure of the fluids in the body; and an electronics structure for receiving signals from the sensor array and wirelessly transmitting the same to a remote receiver; the sensors are in communication with fluids bathing the prosthesis to measure the pressure of the fluids.
2. US10219699– IMPLANTABLE SENSORS AND METHODS OF USE

   The invention from Intellirod Spine Inc. deals with medical diagnostic measurements from implanted sensors. A spinal implant-monitoring apparatus that includes: a bridge, strain gauges to provide a signal indicative of strain measured between the legs of the bridge; a second interior with the control circuitry, the housing mounted on the surface of the bridge, etc. The control circuitry is in communication with the strain gauges and are configured to convert the signal into digital data.
3. EP3345538A1– IMPLANTABLE KNEE SENSOR AND METHODS OF USE

   The invention from Biomet LLC deals with an implantable sensor configured to be inserted in an intramedullary canal consisting of a primary insert, a secondary insert, and an antenna. The primary insert can include a distal end and a proximal end, and a central bore that can extend from an opening in the distal end towards the proximal end. The secondary insert can include a body and a sensor module. The sensor module can be disposable within the body and can be configured to produce a sensor signal as a function of a parameter indicative of infection. The antenna can be disposed in the central bore and can be configured to transmit a wireless signal as a function of the sensor signal.
4. WO2017143400A1– IMPLANTED SENSING SYSTEM FOR JOINT REPLACEMENTS

   The invention from MACQUARIE UNIVERSITY deals with a sensor for monitoring a prosthesis implanted in biological tissue. The sensor transmits a measurement signal towards the prosthesis which is received by a receiver. An antenna transmits data to an external device. A data analyser analyses the transmitted data to obtain monitoring information comprising spatial position of the prosthesis relative to the sensors.
5. CN105832448A– INTELLIGENT KNEE JOINT TIBIA PLATFORM TEST PAD MODULE

   The invention from Just Huajian Medical Device Ltd relates to an intelligent knee joint tibia platform test pad module. The intelligent knee joint tibia platform test pad module comprises test pad body which is provided with an accommodating cavity and a force measurement chip which is arranged in the accommodating cavity in the intelligent knee joint tibia platform test pad module, so that the stress distribution on the inner and the outer side of a knee joint during a moving process can be measured and displayed accurately through pressure sensor probes which are uniformly arranged on a force measurement plate frame. When a movement test is performed on the knee joint, causes are excluded in time in an operation; uniform distribution of the stress is realized; effective cooperation of artificial prostheses of various parts is ensured.
6. WO2018085417A1– DEVICE FOR SENSING IMPLANT LOCATION AND IMPINGEMENT

   The invention from Zimmer Inc. deals with a system and method for assessing hip arthroplasty component movement. The method includes receiving data from a sensor embedded in a femoral head component, which is configured to fit in an acetabular component, determining information about a magnetic field from the data, and outputting an indication of an orientation, coverage, or a force of the femoral head component relative to the acetabular component.
7. US20180125366– SYSTEMS AND METHODS FOR MONITORING IMPLANTABLE DEVICES FOR DETECTION OF IMPLANT FAILURE UTILIZING WIRELESS IN VIVO MICRO SENSORS

   The invention from Synergistic Biosensors deals with an implantable position detecting system configured to detect a position of an implantable device with respect to a body structure. The system includes one proximity measuring transducer configured to be implanted on the body structure a distance from the implantable device, and another being configured to receive energy from an external electromagnetic field generated by an external sensing interface.
8. US9955983– SYSTEMS AND METHODS FOR PROVIDING ALIGNMENT IN TOTAL KNEE ARTHROPLASTY

   The invention from Arthromeda Inc. deals with systems and methods for providing alignment in total knee arthroplasty operations. It includes multiple sensors coupled to a patient’s bones or other surgical tools. The sensors detect their position and orientation in space and communicate this information to a processor. The processor can utilize the information to display data to a surgeon or other user regarding the position, angle, and alignment of a patient’s bones, surgical tools, and the reconstructed knee joint.

Conclusion

Smart implants will revolutionize the Orthopaedic sector by reducing the post-operative risks associated with surgeries. A handful of products are out in the market from companies such as Orthosensor, Intellirod spine, SpineGuard, etc. Companies like Zimmer, Smith & Nephew Inc. and Stryker have partnered with Orthosensor for VERSASENSE, however top companies in the space are yet to invest in smart implants technology. Interestingly, small companies seems to be playing an active role in this area and also most of the Universities/Research institutes are engaged in developing prototypes of smart implants, conducting trials with funding from investors. In some cases, the prototype has been successfully developed and some are still in the development stage, down the lane few will be able to complete the clinical trials successfully and some will end up in the middle because of lack of funds

The smart implant area in orthopedics is picking up slowly possibly because of the challenges in the reliability of sensors, biocompatibility of smart implants, also customization of the implants in conjunction with sensors, and also with the site of surgery (Knee, Hip, Shoulder OR spine, etc.). Hence, with smart technologies revolutionizing modern medicine, it is anticipated that more companies will invest in further development of this technology.

References

1. Stryker
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2. 7-Eleven launches smart convenience store with Lotte
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3. L’innovation au service de l’orthopédie
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4. Implant électronique RFID pour le suivi de prothèse orthopédique
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5. Intellirod Spine Receives $1.6 Million Ohio Third Frontier Award
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6. Intellirod Spine Receives First-Ever Spine FDA De Novo Approval
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7. SpineGuard Announces First Ever DSG™ Sensor-Guided Pedicle Screw System Launch in the USA by Zavation
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8. Wireless Sensors for Smart Orthopedic Implants
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9. Smart bone plates can monitor fracture healing
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10. Smart, self-powered knee implants
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11. Smart Implant for Orthopedics Surgery (nano-tera project)
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12. Startup Aims to Monitor Joint Loosening and Infection with Implantable Sensors
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