WO2009095768A2

WO2009095768A2 - Smart structures for bone prosthesis

Info

Publication number: WO2009095768A2
Application number: PCT/IB2009/000148
Authority: WO
Inventors: Clara Maria Mesquita Frias; José António DE OLIVEIRA SIMÕES; António TORRES MARQUES
Original assignee: Universidade Do Porto
Priority date: 2008-01-30
Filing date: 2009-01-28
Publication date: 2009-08-06
Also published as: PT103949A; WO2009095768A3; WO2009095768A4; PT103949B

Abstract

This invention relates to structures to be applied in bone prostheses and it refers to a multi-network concept of biosensors and bioactuators that continually and actively monitor the performance and integrity of bone implants inside living organisms. The biosensors network contemplates different sensor technologies (optical, piezoresistive piezoelectric and piroelectrical), which allow a real-time implant monitoring, during and after the surgery, the actuator network consisting of biomimetic material that stimulates bone growth by biological, mechanical, electromechanical, thermal and electrochemical effects. This invention gets on the emergent concept of smart materials and structures specifically directed to medical applications, such as hip, keen, shoulder and orthodontic implants, providing secondary functions to bone prosthesis, such as clinical preventive measures according to the monitor output data, automatic update of implant databases, implant self-repair capacities, minimization of implant unsuccessful performance, controlled drug release and a method for identifying the patient's clinical background, in case of accident or catastrophe.

Description

Description Title of Invention: SMART FRAMEWORKS FOR

BONE PROSTHESIS

Technical domain of the invention

[1] This invention fits into the application and development of health care structures, in particular with regard to the development of bone prostheses. Background of the invention

[2] The report on the state of the art is linked to the development of bone implant biostructures, based on the emerging concept of intelligent materials and structures.

[3] Degenerative diseases of the joints and bone tissue, osteoporosis, and accidental fractures are increasingly present, and occur more and more frequently in the daily lives of the world population. In this context, efficacy, efficiency, safety and longevity are the most important parameters sought by patients undergoing a bone implant in order to return to a normal life.

[4] At the present time, the failure of bone implants manifests itself as a relative movement between the implant and the supporting bone, which occurs due to failures in implant fixation, making it unable to withstand the cyclic loads to which it is attached. subject. The bone implants used are composed of inert materials whose primary functions are mechanical support, mobility replacement, pain relief, and, in joint implants, tribological joint contact. However, the major problem is in the post-operative and rehabilitation phase where in-situ, in-vivo and real-time monitoring of implant status is needed, as well as clinical intervention measures in case of onset of laxation. (detachment).

[5] The clinical diagnostic methods used focus on patient pain and mobility as assessed by scoring systems and radiographic analyzes. However, these techniques do not allow timely and adequate detection of the degree of implant laxation, preventing the implementation of clinical intervention measures, as well as creating an organized schedule of revision surgeries due to the difficulty of accurately predicting the degree of implant failure.

[6] Therefore, the only current options for evaluating the performance of a bone implant are referred to the medical interpretation capability of the set of parameters obtained by compiling the patient's empirical data (functionality / pain level), and by the radiographic results.

[7] Understanding the current state of bone implant development, its functions and limitations makes it easy to recognize the socio-economic impact of this present technology in the health industry. Thus, the structures of the present invention allow to exceed and minimize the costs with bone implants, which have been increasing annually.

[8] WO2006089069 discloses the introduction of the secondary monitoring capability of articular orthopedic implants by encapsulating the implant surface of piezoresistive sensors. This document describes the tool's ability to diagnose joint implants. However, the present invention goes beyond that disclosed in the aforementioned document in several respects both for its in-situ and real-time monitoring capabilities and for its ability to intervene to eliminate causes of failure in the initial state.

[9] Real-time monitoring capability enables up-to-date diagnostics, actual implant behavior and the definition of prophylactic clinical interventions. Prophylactic clinical interventions are understood in this context as up-to-date diagnosis and a prediction of the useful life of the implant, allowing for better scheduling of revision surgery, as well as the administration of appropriate rehabilitation physiotherapeutic treatment. However, the secondary bone monitoring function of the implant is not sufficient to minimize and avoid the causes of failure, it only allows the patient to be identified and prevented for a second surgery.

[10] The present invention attributes to the implant, in addition to the monitoring capacity, the intervention / actuation capacity. This ability results from knowledge of the operation of the bone system. This actuator network will be distributed along the implant surface according to its geometry, size, function and material.

[11] These actuators are composed of biomimetric materials. Its function is to intervene in order to strengthen the bone extra cellular matrix and its blood and lymphatic vascularization. The mode of intervention / action in the proliferation of the extracellular matrix of the bone system is due to the structural properties and biophysical stimulations of these materials. From a structural point of view, these materials have a surface texture and an optimized internal architecture that facilitate cell adhesion, proliferation, remodeling and bone growth. The basic capacities of the sensors / actuators used for biophysical stimulation are: the piezoelectric capacity, which is a feature also present in the natural remodeling of bone tissue, due to the transformation of the mechanical energy of dog movement into electrochemical energy, and vice versa. versa; pyroelectric, the ability to transform mechanical energy into thermal energy, and vice versa; and biochemistry. This intervention / action system also incorporates a drug delivery system through the use of nanocapsules that will be used to combat or prevent some types of pathologies.

[12] Validation of the application of the sensors / actuators referred to in joint prostheses is done using the example of a hip joint femoral component con- winner However, the application of this technology to other types of bone prostheses can be easily accomplished due to the miniaturization capability of the entire system (interrogation, data transmission and feeding) and the ability to produce biosensors and actuators in the most form-fitting manner. Suitable for metal implants, polymer implants, composites, etc. These biostructures are incorporated during the implant manufacturing process, the new implant and the sensor and actuator network being considered as a single structure.

[13] The versatility of geometry, and the small dimensions of all electronic and optoelectronic devices, ensure the applicability of these structures to all bone implants. The number of elements that make up the sensor and actuator networks depends on their function, size, location in hazardous areas and the material of the implant. General Description of the Invention

[14] The present invention considers structures capable of implementing secondary functions in bone implants. This invention is based on the emerging concept of intelligent materials applied, for example, to joint and orthodontic implants. The concept of intelligent structure arises from the development of structures that continuously and actively monitor and optimize their performance, possessing adaptability and interaction capabilities by varying operating conditions. Similarly to biological systems, the development of an intelligent structure seeks to implement the capacity of self-diagnosis, autonomy and self-adaptation / interaction with the internal / external environment. However, intelligent structure in the biological sense also means the ability to promote a more positive biological response towards compatibility.

[15] The intelligent designation for the present invention is due to the fact that it is a multifunctional structure, while allowing structural functionality and the ability to optimize, control and adapt its performance to the environment. The technological key of this invention is the distribution of biosensor (1) and bioaccu- torator (2) networks to the surface of the bone implant. These were developed and selected in the field of materials science and mechanical engineering, and signal processing systems and control algorithms were developed in the areas of electrical engineering and computer sciences.

[16] Through Artificial Biosensor Networks (1) and Signal Processing Systems

(7), it will be possible to detect or feel one or more variations in the physical conditions and / or chemical compounds of the implant / bone system. This new capability enables the clinician to obtain real-time diagnostics by early identifying the initial points (or regions) of the current causes of failure occurring postoperatively. In this way, it intends to implement a new concept of method of Interactive diagnostics between the bone implant and the physician, which can also be applied during surgery to ensure correct implant placement. The measurement parameters obtained by the sensors will be previously validated by in vitro and in vivo calibrations.

[17] Given the complexity and aggressiveness of the biomechanical environment that exists at the implant / bone interfaces, it would be unwise to reduce the biosensor network (1) to one single sensor technology. Thus, the biosensor (1) and hybrid type network is composed of different sensor technologies, such as piezoelectric (2), piezoresistive (3) and optical (4) sensors.

[18] One of the sensor technologies present in this invention is piezoelectric technology, for its ability to be used simultaneously as sensor and actuator.

[19] As a sensor, this polymeric or ceramic material has the advantage that it can be used in various geometric forms, for example in the form of film or fibers (2). The behavior of this sensor to the mechanically aggressive medium, the enzymatic reactions, and to the aqueous medium inside the human body, is perfectly suitable for this application, reflecting in the non-release of particles and a long period of functionality. As a sensor, piezoelectric technology allows, during a dynamic request, the transformation of the applied mechanical energy into previously calibrated electrical signals. Piezoelectric sensors (2) do not require any power supply for their operation.

[20] The piezoresistive technology used in this invention allows the deposition of piezoresistive sensors (3) on bio-substrates of various shapes, ensuring all mechanical resistance and functionality within the human body. The deposition of these sensors will allow real time monitoring of some parameters that define the relative position of the implant. The main function of these quasi-statistical sensors, in the monitoring of the implant, is to characterize the pressure gradient variation, informing the implant's laxation level and the initiation zones. This sensor also allows the geometry of the entire implant to be surveyed in relation to a fixed reference. However, this sensor needs an electrical power supply.

[21] The integration of optical sensors (4) in this application allows, as quasi-statistical sensors in the monitoring scheme, to detect longitudinal, transverse deformations and surface temperature of the implant. Through the measurement of these physical parameters, it is possible to identify the implant sinking levels, as well as the initial laxation zones, working as a complementary method to the piezoresistive sensors (3). These sensors have the advantage over previous immunity to electromagnetic fields. Similar to piezoresistive sensors (3), optical sensors (4) require a power supply (5) to ensure its operation. These sensors have the characteristic of being composed of biodegradable materials, and are used during surgery only to indicate in a minimally invasive way the relative position of the implant during surgery. In the case of metal implants, the placement of these sensors can be done using a biomembrane that is part of the optical sensor network (4).

[22] All sensors used are small in size, light in weight and easily encapsulated in composites or deposited on metal surfaces, contributing to a minimal invasion of the living organism and the device itself. These sensors in various forms guarantee their ease of implementation during the manufacturing process of conventional metal bone implants, or in composite materials.

[23] Regarding the selection of the number and location of the sensors that make up the invention, these depend on the particular application. Critical areas of the implant, which can be predicted by simulation, are monitored by sensors. To define the position relative to a fixed reference frame, at least six sensors are required to determine three translations and three rotations in space. To locate fissure events, both bone and prosthesis, but especially at the interface, several sensors are required. The location of the crack is determined by the times between the occurrence and the arrival of the signal to the sensor. The unknowns to be determined are the space coordinates and the velocity of propagation in the medium (which is considered isotropic). Through the amplitude of the recorded signals, it is possible to distinguish if this occurred in the bone or at the interface.

[24] The present invention further contemplates interrogation schemes appropriate to sensors, allowing the digitization of optical and electronic signals, and the recording and processing of data. The data processing allows, through artificial intelligence, the automatic and manual control of the actuators (2). The interrogation system incorporates a micro-chip that contains a code of access to the National Health System database, which allows, in case of 'catastrophe', to obtain the entire existing clinical history of the patient.

[25] In addition, this invention allows the intervention capacity to be increased by stimulating growth and consequent bone reinforcement at the implant interface, promoting greater implant stability.

[26] Actuators (2) are materials with a biomimetric structure similar to the bony system, which allows its remodeling, mineralization and vascularization through biochemical and biofficial stimulations. These biomimetric actuators distributed along the implant surface and in direct contact with bone are based on piezoelectric technology. In a piezoelectric material, when applying a potential difference between the ends there is a volumetric expansion. These actuators (2) are controlled by microprocessors or by medical indication, also integrating power supply systems (3). Brief Description of the Figures

[27] Figure 1 - This figure represents a femoral component of a hip implant, in different perspectives, with the structures according to the present invention;

(1) Elements of the sensor and actuator network.

[28] Figure 2 - This figure illustrates the concept of multilayer biosensor and actuator networks with the following elements:

(2) bioactivator and / or piezoelectric sensor;

(3) piezo resistive sensor;

(4) optical sensor.

[29] Figure 3 - This figure illustrates the concept of an instrumented femoral component, with the following elements:

(5) feeding system;

(6) electronic / optoelectronic system;

(7) transmit / receive antenna.

[30] Figure 4 - This figure illustrates the concept of interaction between instrumented implant and physician. Detailed Description of the Invention

[31] According to the present invention, the bone prosthesis is added to an intelligent structure, with sensory and acting capacity. This intelligent structure includes a hybrid network of piezoelectric (2), piezoresistive (3) and optical (4) sensors.

[32] Piezoelectric sensors (2) are used to measure transient signals, such as the occurrence of cracking and the velocity of pressure wave propagation in the medium. To process and record this information it is necessary to pre-amplify the analog signal and convert it to digital signal.

[33] Piezo-resistive sensors (3) are used to measure the pressure variations that occur on the implant surface when performing a certain standardized physical exercise. By measuring the pressure at the implant interface and knowing the properties of the materials, it is possible to determine the stresses applied to the bone / prosthesis system and, consequently, to evaluate the evolution of the rehabilitation. These sensors are deposited on a polymeric bio-substrate that will be placed on the implant surface during the implant manufacturing process.

[34] Fiber-optic FBG sensors are used to measure the variations in quasi-statistical deformations that occur on the implant surface. This information complements the information received from the piezo resistive sensors and, during the surgical fixation procedure, guides the placement of the prosthesis. Your correct Placing under pressure allows surface-distributed sensors to have a similar register. Failure to do so means that the prosthesis has been misplaced or cavitation has occurred. Optical sensors (4) must be illuminated by a broad spectrum light source, usually an LED. The interrogation system incorporates a tunable bandpass optical filter and a digital signal loss detector for the processor.

[35] The actuator network (2) is composed of bone-mimetic biomaterials and features optimization of biochemical properties, geometry, macro and microstructure, porosity, internal architecture, surface roughness and mechanical support. of tissue proliferation is the bone surface of the implant.

[36] These biomaterials (2) have bone-tissue piezoelectric capabilities that stimulate bone growth by mechanical, electromagnetic effects. Based on bionanotechnology, this class of biomaterials also allows the controlled release of drugs that are inside semi-embedded nanocapsules in the actuators. Controlled drug release will be effected whenever necessary by material deformation (piezoelectric effects).

[37] All of the technology present in this invention will allow for better bone implant stability, with direct or indirect intervention, in response to early signs of failure that trigger implant failure. The hybrid sensor network is controlled by an optoelectronic scheme (6) which receives the signals emitted by the sensors and processes them. This electronic scheme includes a microprocessor, an analogue to digital signal converter and vice versa, a microcontroller programmed in function of the present sensing technologies (that allows to optimize and to control the various electronic devices), and an electronic microdistive, associated to a rechargeable power supply, which provides controlled electronic micro-loads to the actuators (2).

[38] The structures also incorporate a wireless interface, which allows the data to be transmitted to an electronic device outside where it is recorded (6), or from outside to the controller at the doctor's instruction using a small antenna placed on it inside the implant (7). Technologies for wireless data transmission can be wireless, Bluetooth and radio frequency identification (RFID).

[39] The power system must be sized and can be internal or external, depending on the number of sensors and actuators, their energy consumption and frequency of use, to ensure a minimum permanent use of at least two years. Information about the behavior of the implant in the first two years allows you to predict its long-term behavior. deadline. With this initial information it is also possible to optimize rehabilitation treatments.

[40] The power supply system consists of rechargeable or non-rechargeable batteries and / or small capacitors. Rechargeable batteries are charged during locomotion through physiological stresses that deform piezoelectric materials. These settings generate alternating currents that are transformed into direct current, and stored with the approximate value of 13x10 ³ WN. The rechargeable battery should operate according to medical application standards. An example is a rechargeable lithium ion battery (QL00031 battery, www.quallion.com) with a nominal voltage of 3.6 volts, an amperage of 15 mA, and a nominal capacity of 3 mAh.

[41] The capacitors will be a surrogate or complementary method of the power supply that is activated by the physician during the routine consultation. Activation is controlled via a self-contained radio frequency translator, allowing the electronic system implanted in the prosthesis to transmit sensor data via a low-power wireless link.

[42] In the particular case of the femoral component, both systems will be validated.

[43] Subsequently, to complement the entire diagnostic process, the electronic data receiving device will expose the results to three dimensions. If the onset of detachment or other anomaly is detected, the physician will initiate a set of prophylactic measures, including microvibrations at the implant surface, and / or controlled release of drugs. In these two processes, the electronic system will be activated by an external control which will allow the application of a potential difference to the piezoelectric actuators thereby stimulating osteosynthesis.

Claims

[Claim 1] Bone prosthesis structures, characterized in that they are composed of at least one biosensor network (1), an interrogation system, a microprocessor, a signal converter, a microcontroller, a power system (5), an interface Wireless to transmit sensor data (6 and 7), hardware, and a software interface to represent the operating conditions of the implant in real time.

[Claim 2] Bone prosthesis structures according to claim 1, characterized in that they are composed of at least one network of bioactuators (2), a microprocessor, a microcontroller, signal converters, a power system (5), and wireless interface to enable control of bioactuators

(2) from the outside.

[Claim 3] Bone prosthesis structures according to Claim 1, characterized in that the biosensor network (1) comprises at least one biodegradable or inert organic or inorganic piezoelectric sensor (5).

[Claim 4] Bone prosthesis structures according to claim 1, characterized in that the biosensor network (1) comprises at least one biodegradable or inert organic or inorganic piezoresistive sensor (3).

[Claim 5] Bone prosthesis structures according to claim 1, characterized in that the biosensor network (1) includes at least one biodegradable or inert optical (4) organic or inorganic sensor.

[Claim 6] Bone prosthesis structures according to claim 1, characterized in that the smart bone prosthesis structure contains at least one biosensor network (1) which detects the movement of the bone prosthesis with 6 degrees of freedom during the surgery.

[Claim 7] Bone prosthesis structures according to Claim 1, characterized in that the smart bone prosthesis structure contains at least one biosensor network (1) which detects the movement of the bone prosthesis with 6 degrees of freedom through least during the two years after surgery.

[Claim 8] Bone prosthesis structures according to Claim 1, characterized in that the interrogation scheme includes at least one electronic and optoelectronic component (6) for interrogating the sensor data (1).

[Claim 9] Bone prosthesis structures according to claim 2, characterized in that the bioactuators (2) include at least one biocomposite material whose functionality is based on piezoelectricity by combining ceramic or polymeric materials, such as inorganic materials C, Si , SiGe, TIO or HA and PVDF, PMMA or epoxy organic matrices.

[Claim 10] Bone prosthesis structures according to claim 2, characterized in that the bioactuators (2) include at least one biocomposite using bio-micro and nanocapsules to implement controlled release properties of drugs.

[Claim 11] Bone prosthesis structures according to claim 2, characterized in that the bioactuator network (2) comprises at least one biomimetric material based on piezoelectric technology that promotes the growth of the bone system and endothelial cells by mechanical stimulation. .

[Claim 12] Bone prosthesis structures according to claim 2, characterized in that the bioactuator network (2) comprises at least one biomimetric material based on piezoelectric technology that promotes growth of the bone system and endothelial cells by stimulation. electromagnetics.

[Claim 13] Bone prosthesis structures according to claim 2, characterized in that the bioactuator network (2) comprises at least one biomimetric material based on piezoelectric technology which allows controlled release of drugs.

[Claim 14] Structures for bone prostheses according to claim 2, characterized in that the microprocessor is responsible for executing pre-programmed or unscheduled instructions, processing capacity and data compilation of the different sensors.

[Claim 15] Bone prosthesis structures according to claim 2, characterized in that the signal converters are responsible for converting the output and output signals of the different sensors (1) and actuators (2) into digital or analog signals.

[Claim 16] Structures for bone prostheses according to claim 2, characterized in that the microcontroller is responsible for optimizing and controlling the electronic devices.

[Claim 17] Structures for bone prostheses according to claim 2, characterized in that the microcontroller includes at least one micro chip with the patient's entire medical history.

[Claim 18] Bone prosthesis structures according to claim 2, characterized in that the electronic actuating device includes at least one electronic component that supplies controlled electrical charges to the bioactuators (2).

[Claim 19] Structures for bone prostheses according to claim 2, characterized in that the feeding system (5) may be conventional non-rechargeable or rechargeable using commercially available bio-microbacteria.