Stretching device with reflector

Abstract

The present invention relates to a system for evaluating the evolution of a bone structure of a subject, the system comprising: an implantable medical device comprising a distraction body and at least one reflector coupled to the distraction body, the distraction body being configured to osteotomically distract separated bone segments and comprising a first block for implantation and attachment to a first bone segment, a second block for implantation and attachment to a second bone segment separated from the first bone segment by osteotomy, and an actuator, the actuator being configured to adjust a space between the first block and the second block when activated, thereby achieving distraction between the first bone segment and the second bone segment, wherein the at least one reflector is configured to reflect electromagnetic signals and is embedded in surrounding tissue of the subject when the distraction body is attached to the bone of the subject; a computing module configured to calculate parameters representing the bone structure of the subject surrounding the bone distraction device, the parameters being calculated based on a reflection signal corresponding to reflection of an excitation signal on the reflector embedded in the surrounding tissue of the subject, the excitation signal comprising at least one frequency within a characteristic frequency range of the reflector, the reflection signal representing a dielectric constant of the surrounding tissue.

Description

Technical Field

[0001] The present invention relates to the field of implantable bone distraction devices.

[0002] More particularly, the present invention relates to an apparatus and method for osteotomically distracting separated bone segments. Background Art

[0003] Distraction osteogenesis is a surgical procedure aimed at lengthening bones. Lengthening occurs by creating new bone material in the space between two previously connected bone segments. This new bone is called callus, and its quality and hardness are key parameters for withstanding mechanical stress. For adjusting the distraction osteogenesis procedure, monitoring callus regeneration during the distraction phase of the operation is of great significance. In fact, if the callus is too soft, the distraction step should be postponed to provide more time for the callus regeneration process. On the contrary, if the callus is strengthened too early, the distraction length cannot be reached, and a new surgical intervention is required to restore the distraction. Once the desired length is reached, it is also beneficial to monitor the callus. In fact, once the desired length is reached, the distraction stops and the callus stabilizes. Once the callus solidifies and a rigid mechanical connection is established between the bone segments, the distraction device is removed.

[0004] Prior art includes U.S. Pat. No. 5,364,396, which discloses an implantable bone distraction device and associated methods. The implantable bone device includes two blocks, each of which is fixed to a separate bone segment and connected together to a rotatable drive rod and a drive rod actuator. Actuation of the drive rod actuator causes rotation of the rotatable drive rod actuator, which causes the two blocks to move apart.

[0005] However, in this device, there is no means to monitor bone remodeling. Under such conditions, the operator cannot determine whether the bone structure is regenerating properly.

[0006] A review of the prior art shows that there is a need for an implantable system that allows remote monitoring of bone tissue regeneration. This system would allow patients and caregivers to assess and monitor the local quality and evolution of bone tissue over time. Summary of the invention

[0007] The present invention relates to a system for assessing the evolution of a subject's skeletal structure, the system comprising:

[0008] - An implantable medical device comprising a distraction body and at least one reflector coupled to the distraction body, the distraction being configured to osteotomically distract a separated bone segment, and comprising:

[0009] - a first piece, which is intended to be implanted and attached to a first bone segment,

[0010] - a second piece, which is intended to be implanted and attached to a second bone segment, which is separated from the first bone segment by an osteotomy,

[0011] - an actuator configured to adjust the space between the first and second masses when activated, thereby achieving distraction between the first bone segment and the second bone segment,

[0012] wherein the at least one reflector is configured to reflect electromagnetic signals and to embed into surrounding tissue of the subject when the distraction body is attached to a bone of the subject,

[0013] - A calculation module configured to calculate parameters representing a bone structure of a subject surrounding a bone distraction device, the parameters being calculated based on a reflection signal corresponding to reflection of an excitation signal on a reflector embedded in surrounding tissue of the subject, the excitation signal comprising at least one frequency within a characteristic frequency range of the reflector, the reflection signal representing a dielectric constant of the surrounding tissue.

[0014] In one embodiment, the system further comprises:

[0015] - a transmitting module configured to transmit an excitation signal comprising at least one frequency in a characteristic frequency range of the transmitter;

[0016] - a receiving module configured to receive a reflection signal corresponding to the reflection of the excitation signal transmitted by the transmitting module on a reflector embedded in the surrounding tissue of the subject.

[0017] In one embodiment, at least two of the transmitting module, the receiving module, and the computing module are integrated in the same external non-intrusive device. This embodiment allows for a more convenient and functional external non-intrusive device.

[0018] In one embodiment, the reflector is configured to reflect an excitation signal applied to the reflector.

[0019] In one embodiment, the reflector has a planar shape or a curved shape. Different reflector shapes allow the reflector to be adjusted to the surface of different implants.

[0020] In one embodiment, the system comprises at least two reflectors arranged at different positions relative to the implant. Multiple reflectors allow to have accurate measurements of bone regeneration. Multiple reflectors on the implant allow to monitor local information about bone quality.

[0021] In one embodiment, the computational module is configured to compute a geometrical map of parameters representative of the subject's skeletal structure based on reflection signals associated with different reflectors and respective positions of the reflectors relative to the distraction body.

[0022] In one embodiment, parameters representing the bone structure of the subject are calculated based on a comparison between the reflected signal and a model that establishes a correlation between the reflected signal on the reflector and its surrounding tissue on the one hand and the parameters representing the bone structure on the other hand.

[0023] In one embodiment, parameters representative of the subject's bone structure are calculated based on a comparison between the reflected signal and previously acquired reflected signals. The comparison allows the state of bone regeneration to be determined.

[0024] In one embodiment, a reflector is fixed to the distraction body, wherein the reflector is fixed to the first mass, the second mass or the actuator.

[0025] In one embodiment, the implantable bone distraction device according to the present invention also includes a drive rod having a first end accommodated in a first chamber hole defined by a first block, and a second end opposite to the first end accommodated in a second chamber hole defined by a second block, the drive rod being capable of adjusting the space between the first block and the second block, wherein the first chamber hole is a drive chamber hole, and the second chamber hole is a threaded hole, and the second end of the drive rod is a threaded end threadedly accommodated in the threaded hole of the second block, wherein the actuator cooperates with the drive rod to rotate the drive rod, and the drive rod is capable of adjusting the space between the first block and the second block.

[0026] The invention also relates to a method for evaluating the evolution of a subject's bone structure using a system according to the invention, the system having an implant intended to be attached to a bone of the subject and at least one reflector coupled to the implant, the reflector being configured to reflect electromagnetic signals and, when the implant is attached to the bone of the subject, to come into contact with surrounding tissue of the subject, the method comprising the steps of:

[0027] - emitting an excitation signal comprising at least one frequency in a characteristic frequency range of the reflector;

[0028] - receiving a reflection signal corresponding to reflection of an excitation signal transmitted by the transmission module on a reflector embedded in surrounding tissue of the subject, the reflection signal representing a dielectric constant of the surrounding tissue;

[0029] - Based on the received reflected signals, parameters representing the subject's bone structure are calculated.

[0030] definition

[0031] In the present invention, the following terms have the following meanings:

[0032] - "Bone regeneration" refers to the physiology of the welding of bone segments. The bone at the interface gradually becomes denser and harder until a rigid mechanical connection is created between the two adjacent bone segments.

[0033] - "Reflector" refers to a member configured to reflect electromagnetic signals and which is embedded in surrounding tissue of a subject when the implant is attached to a bone of the subject. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The following detailed description will be better understood when read in conjunction with the accompanying drawings. For illustrative purposes, the system is shown in a preferred embodiment. However, it should be understood that the application is not limited to the precise arrangements, structures, features, embodiments, and aspects shown. The drawings are not drawn to scale and are not intended to limit the scope of the claims to the described embodiments. Therefore, it should be understood that where features mentioned in the attached claims are followed by reference numerals, these reference numerals are included only for the purpose of enhancing the intelligibility of the claims and are in no way limiting the scope of the claims.

[0035] Features and advantages of the present invention will become apparent from the following description of an embodiment of the system, given by way of example only and with reference to the accompanying drawings, in which:

[0036] Figure 1a is a first stereoscopic view of a medical device implant having a reflector,

[0037] Figure 1b is a second stereoscopic view of another medical device implant having a reflector,

[0038] Figure 2a is a first stereoscopic view of a medical device implant having a screw-on end and a longitudinal reflector,

[0039] Figure 2b is a second stereoscopic view of another medical device implant having a screw-on end and a reflector wrapped around the implant,

[0040] Figure 3a is the first localization of a medical device implant with a reflector within a bone,

[0041] Figure 3b The invention relates to a second positioning of a medical device implant having a reflector on a bone surface. DETAILED DESCRIPTION

[0042] Although various embodiments have been described and illustrated, the detailed description should not be construed as being limited thereto. Various modifications may be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the present disclosure as defined by the claims.

[0043] A first aspect of the invention relates to a system for assessing the evolution of a subject's bone structure during bone distraction, the system comprising at least one reflector for monitoring a bone healing process between two separated bone segments, and a computing module.

[0044] like Figure 1a and 1b As shown, a system for evaluating the evolution of a subject's bone structure is shown. The system includes an implantable medical device 1, which includes an implant 2 and a reflector 3. In these embodiments, the implant 2 is a distraction device implanted on the two separated bone segments. The implantable medical device 1 can be implanted on any bone that allows distraction or in a bone to be distracted. The implant 2 can be made of various materials, such as metals, polymers or ceramics. In another embodiment, the implant 2 can also be made of carbon graphite fiber.

[0045] like Figure 1a As shown, the implantable medical device 1 includes a first piece 2a for implantation and attachment to a first bone segment, the first piece 2a defining a first chamber hole (not shown) located in an inner portion of the implantable medical device 1. The implantable medical device 1 includes a second piece 2b for implantation and attachment to a second bone segment separated from the first bone segment by an osteotomy, the second piece defining a second chamber hole. In one embodiment, the first piece 2a is configured to accommodate the second piece 2b.

[0046] The second section 2b is able to slide within the first piece 2a, which allows the space between the first piece 2a and the second piece 2b to be adjusted. The first piece 2a and the second piece 2b are cylindrical, but in another embodiment, the first piece 2a and the second piece 2b can have other shapes, such as rectangular. The size of the implantable medical device 1 is defined according to the size of the distracted bone. The implantable medical device 1 is made to fit the distracted bone.

[0047] The implantable medical device 1 also comprises an actuator for adjusting the space between the first block 2a and the second block 2b when activated, which allows distraction between the first bone segment and the second bone segment. In the system according to the invention, different types of actuators can be used. One possibility would be a motor with a worm, or even a magnetic coupling system as known to those skilled in the art. The inventors do not want to be limited to specific actuators; the actuators can be arranged in different positions according to the requirements.

[0048] The implantable medical device 1 further comprises a hook device divided into two parts 4a and 4b. The first hook device 4a is fixed to the first block 2a and the second hook device 4b is fixed to the second block 2b. The first hook device 4a comprises three arms with at least one hole at each end of each arm. The number of arms is not limited. The first hook device 4a rotates around the first part of the implant 2. The second hook device 4b is fixed at the end of the second block 2b. The second hook device 4b is cap-shaped, but may have other shapes in another embodiment. The second hook device 4b has three arms with at least one hole 5 at each end of each arm. The number of arms is not limited.

[0049] The at least one hole 5 is configured to receive at least one screw for screwing the implant onto a bone surface or into a bone.

[0050] Figure 1a and 1b The implantable medical device also includes at least one reflector 3, which can be set at multiple positions on the implant 2 for monitoring the regeneration of bones between the first piece 2a and the second piece 2b during distraction. When the implant 2 is arranged, the reflector 3 contacts the surrounding tissue of the subject. The at least one reflector 3 is configured to reflect electromagnetic signals with a characteristic frequency range of 1 MHz to 50 GHz. Preferably, the characteristic frequency range is 500 MHz to 15 GHz. The reflector 3 can amplify and / or filter the reflected signal to improve the signal-to-noise ratio. The number of reflectors 3 on the implant 2 is not limited.

[0051] exist Figure 1a and 1b In the embodiment, the reflector is arranged on the first hook device 4a of the implant 2. In other embodiments, the reflector can be arranged in other positions, such as on the first piece 2a or the second piece 2b of the implant 2, or on each part of the implant 2. The number of reflectors on the implant 2 is not limited. In this embodiment, the reflector 3 has a rectangular shape. In other embodiments, the reflector 3 may have other shapes, such as a circular or square shape. Multiple reflectors 3 may have different shapes to provide specific and identifiable reflection signals. The relative position of each identifiable reflector 3 can be known during the implantation step.

[0052] In another embodiment, the at least one reflector 3 is partly the implant 2 itself. For example, the first block 2a or the second block 2b of the implant 2 can be configured to emit electromagnetic waves. In another embodiment, the implant 2 can itself be the reflector 3. Each part of the implant 2 can reflect electromagnetic waves.

[0053] In another embodiment, the implant 2 may be the reflector itself, comprising at least one hole with a complementary shape of the reflector 3, which allows reflecting electromagnetic signals without a reflector. In this embodiment, the implant may be 3D printed, for example, and may be made of titanium.

[0054] In another embodiment, the reflector 3 may be a passive implantable reflector, and in a specific embodiment, the reflector 3 may be a resonator. For example, the resonator may be an open-loop resonator or a dipole antenna.

[0055] like Figure 2a and 2b As shown, a screw for fixing the implant 2 can be associated with the implantable medical device 1. Figure 2a In the embodiment, the device 1 comprises a reflector 3. The implant 2 can be made of various materials, such as metal or polymer or ceramic. In another embodiment, the implant 2 can be made of carbon graphite fibers.

[0056] exist Figure 2a and 2b In the embodiment, implant 2 is a fixing screw. The screw passes through the Figure 1a and 1b The implantable medical device 1 is fixed to the bone through the holes 5 of the first hook device 4a and the second hook device 4b. Figure 2a and 2b The implant 2 passes through the entire bone segment and provides information on the progress of bone regeneration.

[0057] exist Figure 2a and 2b In the embodiment, the implant 2 has a threaded end, which allows the threaded part to be inserted into the bone by directly screwing it. In this embodiment, the implant 2 is screwed by the front end 16 of the implant 2. After the movement of the front end 16, the rear end 15 of the implant 2 is screwed, which allows the implantable medical device 1 to be implanted. Figure 2a The reflector 3 extends longitudinally along the surface of the bone, and Figure 2b The reflector is wound around the surface of the bone in a thread-like configuration. The rear end 15 has a larger diameter than the front end 16 to lock the first part of the implant to the bone. The rear end 15 is located outside the truncated bone. For this embodiment, see Figure 3b In this embodiment, the rear end 15 is locked into one of the holes of the first hook device 4a and the second hook device 4b of the implant. In another embodiment, when the implant 2 is fixed directly into the bone to be distracted, the rear end 15 is in the cut bone. For this embodiment, see Figure 3a .

[0058] According to a preferred embodiment, the system for assessing bones further comprises a calculation module (not shown in the drawings) configured to calculate parameters representing the bone structure of the subject.

[0059] The transmitting module transmits an excitation signal including at least one frequency, and the reflector 3 receives the excitation signal in the surrounding tissue of the subject and reflects the signal to the calculation module.

[0060] The reflected signal results in a parameter representing the bone structure. After the measurement, the computing module compares the parameter with the previous measurement. The comparison results in an indication of the evolution of the bone structure. In another embodiment, the computing module compares the parameter with a model or a predetermined threshold to determine an indication of the progress of bone regeneration.

[0061] In one embodiment, the calculation module is a non-invasive device. In another embodiment, the calculation module can be an invasive device combined with, for example, an implantable medical device 1. The parameter is calculated based on a reflection signal corresponding to the reflection of the excitation signal on the reflector 3 in contact with the surrounding tissue. The reflection signal represents at least one electrical property of the surrounding tissue, such as a dielectric constant.

[0062] The dielectric parameters of bone tissue are well correlated with its composition. For example, the relative dielectric constant at frequencies of 100kHz to 5MHz is different from that of tissues with a loose structure. It has been found that the microstructural parameters on the surface of the trabecular structure are the main determinants of the relative dielectric constant. This shows that changes in different microstructural elements can be detected by various electrical parameters.

[0063] When an electromagnetic wave is incident on human tissue, some of the energy is transmitted and some is reflected back due to impedance mismatch. The reflection and transmission coefficients vary between tissues and depend on the dielectric constant, conductivity, conductivity and frequency.

[0064] The reflected electromagnetic waves depend on the dielectric properties of the tissue; frequency analysis of the reflected electromagnetic waves leads to detection of tissue differentiation or contrast.

[0065] When bone tissue regeneration occurs, there is an evolution of the dielectric properties that can be monitored by reflected wave analysis (either in frequency or in time).

[0066] Example: Osteoporosis is a disease that develops into a serious health condition, the main symptoms of which are a decrease in density and damage to the bone tissue structure. Bone tissue generally consists of two layers: the outer layer is cortical bone and the inner layer is trabecular bone. When bone tissue is damaged by osteoporosis, calcium flows away from the trabecular bone. As a result, the pores and cracks that gradually form are filled with liquid components: fat and bone marrow. As a result, the development of osteoporosis leads to changes in the physical characteristics of the trabecular bone, especially the complex dielectric constant.

[0067] According to another embodiment, the system for assessing bone evolution comprises a transmitting module configured to transmit an excitation signal comprising at least one frequency in a characteristic frequency range of the reflector 3 .

[0068] The system further comprises a receiving module configured to receive a reflection signal; the reflection signal corresponds to the reflection of the excitation signal emitted by the excitation module on the reflector 3 in contact with the surrounding tissue of the subject. The transmitting module and the receiving module can be only a single non-invasive device. In another embodiment, the transmitting module, the receiving module, and the computing module are coupled in one non-invasive device.

[0069] In one embodiment, the non-invasive device is configured to individually identify the reflection signal of each reflector 3 of the implantable medical device. In another embodiment, the non-invasive device is configured to display a parameter of the progress of bone regeneration. The parameter is calculated for each reflector 3 of the implantable medical device. The advantage of this embodiment is that the operator can make his diagnosis based on the measurement provided by the specific reflector 3 located according to the required information. In another embodiment, the parameter can be calculated based on the synthesis of different reflection signals of multiple reflectors 3. The advantage of this embodiment is that the operator can make his diagnosis based on the measurement set provided by each reflector 3 representing the global information of the progress of regenerating bone.

[0070] In another embodiment, the non-invasive device is configured to display the estimated remaining time before complete regeneration and formation of bone between the first mass 2a and the second mass 2b. With such information, the subject can adjust his daily living activities accordingly.

[0071] After implantation of the implantable medical device 1 on or in a bone, after a distraction step, a bone regeneration process between the first mass 2a and the second mass 2b is expected. The progress of the bone regeneration process can change the excitation signal during reflection of the reflector 3.

[0072] When a practitioner uses a non-invasive device, the implantable medical device is exposed to the stimulus. Measurements may be performed, for example, every month. In another embodiment, the measurements are continuous. The frequency of measurements is not limited.

Claims

1. A system for assessing the evolution of a subject's skeletal structure, the system comprising: An implantable medical device (1) comprising a distraction body (2) and at least one reflector (3) coupled to the distraction body (2), the distraction body (2) being configured to osteotomically distract a separated bone segment and comprising: - a first piece (2a) for implantation and attachment to a first bone segment, - a second piece (2b) for implantation and attachment to a second bone segment separated from the first bone segment by an osteotomy, - an actuator configured to adjust the space between the first block (2a) and the second block (2b) when activated, thereby achieving distraction between the first bone segment and the second bone segment, wherein the at least one reflector (3) is configured to reflect electromagnetic signals and to embed into surrounding tissue of the subject when the distraction body (2) is attached to a bone of the subject, - A calculation module configured to calculate parameters representing the bone structure of the subject surrounding the bone distraction device, the parameters being calculated based on a reflection signal corresponding to reflection of an excitation signal on a reflector (3) embedded in surrounding tissue of the subject, the excitation signal comprising at least one frequency within a characteristic frequency range of the reflector (3), the reflection signal representing the dielectric constant of the surrounding tissue.

2. The system according to claim 1, further comprising: - a transmitting module, which is configured to transmit an excitation signal including at least one frequency in a characteristic frequency range of the reflector (3); - a receiving module configured to receive a reflection signal corresponding to the reflection of the excitation signal emitted by the transmitting module on a reflector (3) embedded in the surrounding tissue of the subject.

3. The system according to claim 2, wherein: At least two of the transmitting module, the receiving module, and the calculating module are integrated in the same external non-intrusive device.

4. The system according to claim 1, wherein: The reflector (3) has a planar shape.

5. The system according to claim 1, wherein: The reflector (3) has a curved shape.

6. The system according to claim 1, wherein: The calculation module is configured to calculate a geometric map of parameters representing the bone structure of the subject based on the reflection signals associated with different reflectors (3) and the corresponding positions of the reflectors relative to the distraction body.

7. The system according to claim 1, wherein: Parameters representing the bone structure of the subject are calculated based on a comparison between the reflection signal and a model, which establishes a correlation between the reflection signal on the reflector (3) and its surrounding tissue on the one hand and the parameters representing the bone structure on the other hand.

8. The system according to claim 1, wherein: Based on a comparison between the reflection signal and previously acquired reflection signals, a parameter representative of the subject's bone structure is calculated.

9. The system according to claim 1, wherein: The reflector (3) is fixed to the tension body (2), wherein the reflector (3) is fixed to the first block, the second block (2b) or the actuator.

10. The system according to claim 1, further comprising a drive rod having a first end received in a first chamber hole defined by the first block (2a), and a second end opposite to the first end received in a second chamber hole defined by the second block (2b), the drive rod being capable of adjusting the space between the first block (2a) and the second block (2b), wherein: The first chamber hole is a drive chamber hole, and the second chamber hole is a threaded hole, the second end of the drive rod is a threaded end threadedly received in the threaded hole of the second block (2b), and wherein the actuator cooperates with the drive rod to rotate the drive rod, and the drive rod is capable of adjusting the space between the first block (2a) and the second block (2b).

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