WO2025008164A1

WO2025008164A1 - Sensor device for measuring mechano-biological parameters and devices including such a sensor

Info

Publication number: WO2025008164A1
Application number: PCT/EP2024/066731
Authority: WO
Inventors: Markus Windolf
Original assignee: Bios Medical Ag
Current assignee: Bios Medical Ag
Priority date: 2023-07-03
Filing date: 2024-06-17
Publication date: 2025-01-09
Anticipated expiration: 2026-01-03

Abstract

Sensor device (12) for detection and preferably also measurement of a force and/or displacement acting in three space directions on at least one activation member (3) of the sensor device (12), wherein the sensor device (12) comprises at least one elastically deformable membrane (2), and at least one sensing element (4), wherein said at least one sensing element (4) is suitable and adapted to detect and measure one or both of a tension and compression of an elastically deformable material of the elastically deformable membrane (2) on and/or in which the at least one sensing element (4) is located, wherein said at least one elastically deformable membrane (2) is, on an outer portion thereof (26), attached to and/or integral with a framing (2), wherein said at least one elastically deformable membrane (2) comprises a central portion (27) distanced from said outer portion (26), and a surrounding portion (29) circumferentially surrounding said central portion (27), wherein said at least one activation member (3) is attached to and/or integral with said central portion (27), and wherein said at least one sensing element (4) is at least partially provided on and/or integrated with and/or coupled with said surrounding portion (29) of said at least one elastically deformable membrane (2).

Description

TITLE

SENSOR DEVICE FOR MEASURING MECHANO-BIOLOGICAL PARAMETERS AND DEVICES INCLUDING SUCH A SENSOR

TECHNICAL FIELD

The present invention relates to a sensor arrangement for measuring mechano-biological parameters e.g. on implants, medical devices or biological tissues including but not limited to ligaments, tendons, bones, muscles and blood vessels, internally or externally to the human body, to devices including such sensor arrangements, methods of using such sensor arrangements and methods of manufacturing such sensor arrangements.

PRIOR ART

US 2016/0128573 A1 discloses systems, methods, and an apparatus for obtaining medical diagnostic measurements from implanted sensors. In various embodiments, a spinal implant-monitoring apparatus may include: a bridge defining a first hermetically-sealed interior and two or more legs; one or more strain gauges contained within the first hermetically-sealed interior of the bridge to provide a signal indicative of strain measured between the legs of the bridge; a housing defining a second hermetically-sealed interior, the housing mounted on a surface of the bridge; and control circuitry contained within the second hermetically-sealed interior. The control circuitry may be in communication with the one or more strain gauges and may be configured to convert the signal into digital data representative of the signal. Methods of using such apparatus are also disclosed.

Drawbacks of this apparatus are its complexity and space requirements making it unsuitable to measure in confined spaces like implant cannulations remote to the point of strain pickup (strain gauges location). Another drawback is the anisotropic deflection behavior of the proposed structure under different loading directions making the apparatus unsuitable to measure a multitude of loading dimensions in different planes under bending, torsion or tension/compression. Yet another drawback of the proposed apparatus is the presence of two separated and sealed compartments, rendering signal and energy transmission through hermetic barriers necessary, which is technically demanding.

US-A-2018242864 discloses systems and methods for monitoring physiological parameters such as intracranial pressure (“ICP”), intracranial temperature, and subject head position. In some embodiments, an implantable apparatus for measuring ICP can be implanted into a subject skull. The apparatus can comprise an implant body having a hermetically sealed chamber housing a gas at a reference pressure, and a pressure conduction catheter having a proximal end and a distal end, wherein the distal end is configured to extend into the brain through a burr hole in the skull and includes a plurality of ports. A barrier can cover the ports of the distal end of the pressure conduction catheter, wherein the barrier and pressure conduction catheter are filled with a number of gas molecules so that the barrier is not in tension in a predefined range of ICPs. The ports may also be configured such that a barrier is not necessary. Standoffs on the body may be included that stabilize the implant on the skull and enhance reliability and robustness of the measurements.

WO-A-2023018693 concerns an implantable sensor. The implantable sensor includes a sensor assembly configured to connect to a suture. The sensor assembly also includes a substrate and a resonant circuit coupled to the substrate. The resonant circuit is configured to electrically resonate at a resonant frequency when exposed to a first electromagnetic field and to emit a second remotely detectable electromagnetic field. The substrate is configured to deform in response to a tensile force applied by the suture and to change a resonant parameter of the resonant circuit in response to the deformation.

SUMMARY OF THE INVENTION

An object of the invention is to provide a sensor device in particular for measuring mechano- biological parameters on implants, medical devices or biological tissues including but not limited to ligaments, tendons, bones, muscles and blood vessels, internally or externally mounted to the human body.

Body generated forces act on these structures and cause elastic and plastic deformations and deflections of the structures, which are desired to be monitored to diagnose and inform treatment of pathologic conditions and illnesses. In the non-pathologic case, such information can be valuable for health state monitoring and prediction of illnesses and injuries. Particularly when it is intended to surgically implant a sensor device, such data can be highly informative due to direct measurement at the region of interest as opposed to external measurements.

However, space constraints play an increasing role in the implanted case. For example, when it is desired to measure deflection or loading of a hip screw, an intramedullary nail or a bone screw, there is the problem of measuring on small implant surfaces or in narrow cannulations which have typically a diameter in the range of 1-5 mm, a challenging space to accommodate electronic circuitry incl. battery, antenna and hermetic package. The point of measurement with sensing elements must, hence, be dislocated from the peripherical components of the sensor device, a technically demanding design task afflicted with high manufacturing costs, particularly when more than one loading direction should be measured. Another problem of measuring implant deflection inside cannulations is that the cannulation runs through the neutral phase under screw or nail bending. Hence, a potential strain signal magnitude is small and often not suitable for taking measurements.

The invention solves the posed problem with a sensor device in particular for measuring mechano-biological parameters with the features of claim 1.

Generally speaking, the invention relates to a sensor device for detection and measurement of a force, displacement or pressure acting in three space directions on at least one activation member of the sensor device.

The sensor device comprises at least one elastically deformable membrane, and at least one sensing element.

Said at least one sensing element is suitable and adapted to detect and preferably also (quantitatively) measure tensile or compressive strain of an elastically deformable material on and/or in which the at least one sensing element is located.

Said at least one elastically deformable membrane is, on an outer portion thereof, attached to and/or integral with a framing.

Said at least one elastically deformable membrane further comprises a central portion distanced from said outer portion, and a surrounding portion circumferentially surrounding said central portion.

Said at least one activation member is attached to and/or integral with said central portion and said at least one sensing element is at least partially provided on and/or integrated with and/or coupled with said surrounding portion of said at least one elastically deformable membrane.

The sensor device may comprise a housing with an elastically deformable membrane, an activation member connected to or integral with said membrane designed to transmit external force, moment, displacement, strain or pressure to the membrane, and at least one sensing element attached to the membrane configured to pick up deformation of the membrane.

The actuation member can be configured as a thin structure to be placed in narrow cannulations. Also, the actuation member can be long in relation to its diameter and, hence, allows placement of the peripherical components of the sensor device, including the sensing elements, at a suitable remote location, while picking up implant deformation at a desired measurement point.

An elastically deformable membrane, preferably circular, can be easily integrated in a single, preferably cylindrical, metallic, biocompatible and hermetic housing accommodating both, sensing elements and electronic circuitry, making the production simple and cost- effective by use of standard turning and milling processes. Preferably, the device only comprises one single hermetic housing accommodating said elastically deformable membrane. Preferably, the housing and/or the elastically deformable membrane are made of or comprises one of the following materials: Titanium and its alloys, Stainless steel, Cobalt Chrome, Polyetheretherketone (PEEK), Polyoxymethylene (POM), Polyethylene (PE), Polypropylene (PP) or Liquid Cristal Polymer (LCP).

With a stiff activation member being connected to a relatively flexible membrane, the deflection of an implant is transferred to the membrane from a remote location acting like a joystick or lever, while the actual strain of the implant at the measurement point in the neutral phase might be small.

The sensor device according to the invention can, hence, be considered an amplifier for implant deflection. Furthermore, the membrane is locally deformed according to the loading direction of the activation member. With multiple sensing elements distributed over the membrane surface, a multitude of loading directions can be resolved.

With an embodiment of the sensor device according to the invention being mounted in an intramedullary nail in-between the proximal and distal interlocking holes with the point of measurement close to the distal interlocking holes and the point of strain pickup (deformable membrane) close to the proximal interlocking holes, the commonly known problem of distal interlocking can be solved. A locking bolt can be placed through such distal interlocking hole to secure the intramedullary nail in place. Due to the long distance between the proximal aiming arm attachment point to the distal interlocking holes, nail deflection during insertion prevents use of a long rigid aiming arm to guide drill bits and bolts through the holes. A freehand technique must be employed involving excessive X-ray exposure and requiring advanced skills of the operator during the nail insertion procedure. With the aforementioned embodiment according to the invention, the deflection of an intramedullary nail, occurring during insertion into a bone, can be measured and used to adjust the drill trajectory of an adaptable aiming arm or a surgical navigation system or a surgical robot to perform the drilling and bolt insertion procedure.

With another embodiment of a sensor device according to the invention being attached to the stem of a hip, knee, or shoulder endoprosthesis, micromotion or migration of the stem can be detected and monitored. With the point of measurement being at the wall of the intramedullary canal of the bone and the point of strain pickup being fixed relative to the prosthesis stem, relative movement between stem and bone can be measured.

With yet another embodiment of a sensor device according to the invention being configured to be attached to cylindrical rods, rod loading and deflection in posterior spinal fixation constructs or external fixator systems can be monitored. With the measurement point being at a first location at the rod by means of a first clamp and the strain pickup point being fixed to the rod at a second location with a second clamp, a multitude of loading directions can be measured with an isotropic deformation behavior of a preferable cylindrical membrane with narrow space requirements.

With yet another embodiment of a sensor device according to the invention being configured to be attached to a worn device such as a boot or medical tensioning devices like sutures, straps, cerclage wires and cables when slinged around body tissues like muscles, blood vessels or bones. The tension in such device can be transferred and measured to the elastically deformable membrane by means of the actuation member. In another application, tension in sutures can be measured when used in a ligamental or tendon repair procedure to monitor the biological repair process or physiological ligament or tendon loading.

Preferably said activation member protrudes from a first surface of said elastically deformable membrane, and the at least one sensing element is located on said first surface or an opposite second surface.

Preferably the at least one sensing element is located on said second surface, and preferably said activation member takes the form of a pin or a rod, preferably with polygonal or oval or circular cylindrical cross-section, of constant or variable diameter, preferably with an engagement feature at its tip configured to transmit deformation of a measurement object to the activation member.

The activation member can be integral with the elastically deformable membrane and can be preferably made of the same material as the elastically deformable membrane.

The thickness of the elastically deformable membrane can be smaller than the minimum dimension of the activation member in a direction parallel to the plane of the elastically deformable membrane, preferably by at least a factor of 2 smaller.

Preferably there are at least 2 sensing elements, preferably at least 3 sensing elements, or at least 4 sensing elements, most preferably in the range of 2-10 or 2-6 sensing elements, at least partially attached to and/or integral with said surrounding portion, wherein preferably the sensing elements are distributed, preferably regularly, around a circumference of the surrounding portion, preferably at least group-wise with equal radial distance from the central portion.

Preferably there are provided at least 2 or at least 4 sensing elements, which are located adjacent to or at least partially in a transition region between the central portion and the surrounding portion.

Preferably there are provided at least 2 or at least 4 sensing elements which are located adjacent to or at least partially in a transition region between the surrounding portion and the framing. Preferably the framing is part of a housing enclosing an interior cavity, which is preferably hermetically sealed, opposite to a protrusion direction of the activation member and having a housing wall with a housing wall thickness, and wherein the housing wall forms the framing.

Preferably the housing, at least in the region of the framing, is integral with and preferably consists of the same material as the elastically deformable membrane and preferably of the same material as the activation member.

Preferably the elastically deformable membrane is a contiguous membrane, preferably with essentially the same thickness over its whole surface extension.

Preferably the elastically deformable membrane has a polygonal, preferably regularly polygonal shape, or has a rounded shape, preferably an oval and most preferably a circular shape.

Preferably the framing is part of housing, which in a direction parallel to the plane of the elastically deformable membrane has the same shape of outer and/or inner circumference as the elastically deformable membrane, wherein preferably the housing is circular cylindrical.

Preferably the framing has the same shape of inner circumference as the elastically deformable membrane.

Preferably at least 2 sensing elements are configured in at least one Wheatstone half bridge, and/or at least one sensing element is configured in at least one Wheatstone quarter bridge, and/or at least four sensing elements are configured in at least one Wheatstone full bridge, and/or four sensing elements are configured as two independent (Wheatstone) half bridges to pick up two independent strain signals in orthogonal directions.

Preferably the at least one sensing element is a resistive foil strain gauge, a capacitive, piezo-based or photoelectric strain gauge, or a combination thereof.

Preferably the at least one sensing element is attached to and/or integrated into the membrane by a thin film sputtering process.

Preferably the activation member comprises an engagement feature, which is preferably configured as at least one through-hole for receiving one of the following, a medical suture, fiber, strap band, cerclage-wire or -cable.

Preferably the activation member is directly or indirectly coupled to a medical suture, fiber, strap band, cerclage-wire or -cable, and wherein further preferably said sensor device is configured to measure wire/suture tension either by means of activation member bending, or activation member tension/compression.

Preferably it is integrated and/or attached to and/or housed in a device to be worn by and/or connected to a device implanted in a human being or animal and/or implanted in a human being or animal, preferably in a device selected from the group of medical devices, preferably selected from the group of bone screws, in particular a screw or blade component of a cephalic nailing implant or a sliding hip screw and/or blade, or an angular stable locking screw or a compression lag screw or an interlocking bolt or a pedicle screw, or an intramedullary nail, a bone plate, a hip-, knee- or shoulder endoprosthesis, a rod of a spinal pedicle screw system or a rod or Schanz pin of an external fixator system.

Alternatively, the device is integrated and/or attached to a group of externally worn devices, like shoes or boots, preferably at least one device is integrated in a shoe sole.

Preferably the elastically deformable membrane is part of or attached to a housing, which is attached to or integrated into a device or itself comprises attachment means for attaching the device to a reference object, wherein preferably the attachment means is configured as at least one of an external or internal thread, as at least one through hole or open or closed eyelet, or as a press-fit member with conical or cylindrical shape, or as a releasable clamp or as a glued connection.

Preferably the housing comprises a drive feature for engagement with a tool, in particular a screwdriver.

Preferably the housing is designed as a bone screw or an intramedullary nail.

Preferably the device comprises a housing and the housing incorporates an electronic unit with at least one signal conditioner connected to the at least one strain gauge, an analog digital converter, a data processor and a memory to store at least the recorded strain data, where preferably the electronic unit additionally comprises a wireless data transfer unit connected to the memory and to an antenna, and wherein further preferably the wireless data transfer unit is based on a wireless communication standard such as Bluetooth, preferably Bluetooth Low Energy, Zigbee or an RFID (radiofrequency identification) based standard, preferably NFC (near field communication).

Preferably the electronic unit comprises additional sensors connected to the data processor measuring one or a combination of the following dimensions: acceleration of the housing (Accelerometer), angular speed (Gyroscope), location and position, (GPS, global positioning system), or ambient temperature.

Preferably the housing incorporates a battery configured to supply the at least one strain gauge and the electronic unit with energy.

Preferably the housing incorporates an energy harvesting device.

Preferably the housing incorporates an RF induction coil.

Furthermore the present invention relates to a use as defined in the claims, namely to use of sensor device as defined above, as follows: to intermittently or continuously monitor the loading or deflection of a bone screw, implanted into a bone, used as a component of a cephalic hip nail after proximal femur fracture fixation, or inserted into a locking hole of an intramedullary nail, or attached to a bone plate in an angular stable or non-angular stable manner, or to monitor the suture, cerclage or strap tension when slinged around body tissues, or to monitor the suture tension during and after a tendon or ligamental repair procedure or to monitor loading or deflection of an implanted intramedullary nail, or to intra-operatively measure the deflection of an intramedullary nail during insertion into a bone to guide positioning of the interlocking bolts, or to monitor the loading or deflection of the rods of a spinal posterior instrumentation after spinal stabilization or deformity correction surgery, or to monitor the loading or deflection of the rods or Schanz pins of an external fixator, or to monitor micromotion and/or migration of a knee, hip or shoulder endoprosthesis, or to monitor the loading of a foot inside a shoe or boot.

Also the present invention relates to a device with a sensor device as defined above. More specifically, it relates to a device to be worn by and/or connected to a device implanted in a human being or animal and/or implanted in a human being or animal, preferably to a device selected from the group of medical devices, preferably selected from the group of bone screws, in particular a screw or blade component of a cephalic nailing implant or a sliding hip screw and/or blade or an angular stable locking screw or a compression lag screw or an interlocking bolt or a (spinal) pedicle screw, or an intramedullary nail, a bone plate, a hip-, knee- or shoulder endoprosthesis, a (connecting) rod of a spinal pedicle screw system or a rod or Schanz pin of an external fixator system

Further embodiments of the invention are laid down in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1 shows a schematic cut through a sensor according to the invention in a plane perpendicular to the plane of the membrane and including the activation member, wherein in a) the situation is shown without load on the activation member and in b) the situation with a load on the activation member;

Fig. 2 shows a schematic view onto the back surface 2' of the membrane for different configurations and sensing states of the sensing elements, wherein in a) and b) a first embodiment is shown under different loading conditions, in c) and d) a second embodiment is shown under different loading conditions, and in e) a third embodiment is shown;

Fig. 3 shows a cephalic bone screw including the sensor arrangement according to the invention, wherein in a) a side view is shown and in b) an axial cut, and in c) a detailed view of the sensing region according to the oval illustrated in b);

Fig. 4 shows a further biomedical device including the sensor arrangement according to the invention for measuring suture, strap or cerclage tension, wherein in a) the situation is illustrated where the device is subjected to a bending force and in b) the situation is illustrated where the device is subjected to a tension force;

Fig. 5 shows a further biomedical device including the sensor arrangement according to the invention, for measuring suture tension during or after a tendon or ligament repair procedure, wherein a) shows the situation under tension counteracted by the suture on the right side, whereas b) shows the same embodiment with the tension being counteracted by a thread feature on the housing and a drive feature for positioning of the sensor, and c) shows an embodiment allowing to use one single suture only;

Fig. 6 shows an intramedullary nail to be implanted in a bone including the sensor arrangement according to the invention, wherein in a) an axial cut through the whole nail is shown while in b) the sensor region in the proximal portion of the nail is shown in an axial cut under magnification;

Fig. 7 shows a bone screw including a sensor arrangement according to the invention, wherein in a) a side view is shown and in b) an axial cut of a first embodiment, and in c) an axial cut of a second embodiment is shown;

Fig. 8 shows a device for measurement of the loading or deflection of the connection rod of a spinal pedicle screw system or of an external fixator including a sensor according to the invention, wherein in a) and b) two perspective reviews from different viewing directions are illustrated and in c) a perspective view with a partial offset axial cut top portion revealing the sensor arrangement is shown;

Fig. 9 shows a device for measurement of micro-motion and migration of a knee endoprosthesis including a sensor according to the invention, wherein in a) a perspective view is shown and in b) the same view but with a partial axial cut revealing the sensor portion is shown; Fig. 10 shows a shoe including a sensor according to the present invention, wherein in a) a lateral view is shown and in b) a posterior view with transparent shoe sole is shown to illustrate one possible position of the sensor;

Fig. 11 shows a further biomedical device including the sensor arrangement according to the invention for measurement of the loading or deflection of the connecting rod of a spinal pedicle screw system, wherein in a) a perspective view is shown and in b) a perspective view, in which the connecting rod is shown in a half-cut representation including an enlarged representation of the sensor housing part.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 a and 1 b illustrate the measuring principle according to the invention in a cross-section view. A sensor device 12 for measuring mechano-biological parameters comprising a housing 1 enclosing an interior cavity T with an integrated elastically deformable membrane 2, characterized by having a smaller thickness than the thickness of the housing wall 1", one or more sensing elements 4 attached to the internal membrane surface 2' and an activation member 3 integral with or attached to the membrane 2 on the inner membrane surface 2" in a “joystick” type configuration, the activation member 3 having a high stiffness in relation to the stiffness of the membrane 3. The membrane 2 is attached to or integral with the framing 28 of the housing 1 at its edge portion or circumference 26. The activation member 3 is attached to or integral with the membrane 2 in a central portion 27 thereof. Between the central portion 27 or the activation member 3 and the edge portion 26 there is a surrounding portion 29, circumferentially enclosing the central portion 27 or the activation member 3.

Fig. 1 b illustrates the activation member 3 being loaded or displaced along arrow F and transmitting the load or displacement F to the membrane 2 and thereby deforming the membrane 2. A characteristic deformation pattern of the membrane 2 is generated and is picked up by sensing elements 4 in terms of compressive (C) and tensile (T) strains at the membrane surface, the change in strain normally being linear to the change in exerted force or displacement.

Fig. 2a-e show illustrative planar views of the membrane 2 surface area with different sensing element 4 configurations and loading conditions. Here, the membrane 2 is circular, the activation member 3 is attached to or integral with the center of the membrane 2 and the membrane 2 is arranged concentrically inside a circular cylindrical housing 1 of the sensor device 12.

Fig. 2a illustrates a configuration with four sensing elements 4 arranged on a circle in 90° angular increments around the transition area 23 between membrane 2 and activation member 3 where the highest surface strain is generated. The activation member 3 is loaded with a force F at its tip to the left exerting a bending moment to the membrane 2 resulting in tensile strain (+) at the left sensing element 4 and compressive strain (-) at the right sensing element 4, while the other two sensing elements 4 remain unloaded (0).

When the direction of the force F changes (e.g. pointing upwards in Fig. 2b), loading of the sensing elements 4 changes accordingly.

Generally speaking, and not limited to the specific embodiments as illustrated in the figures, the sensing elements 4 can be one of, but not limited to, resistive-, capacitive-, piezo-based or photoelectric strain gauges. The sensing elements can be foil strain gauges glued to the membrane 2 or can be thin film sputtered to the membrane surface.

The sensing elements 4 can be configured in one or more Wheatstone bridges, e.g. in a full-bridge with four sensing elements or, for example, in two half bridges, where upper and lower sensing elements form one bridge and left and right sensing elements 4 form the other bridge.

This has the advantage that two separate strain signals in orthogonal directions can be recorded allowing for also determining the direction of the force or displacement vector F in addition to its magnitude. Further, it has the advantage of eliminating sensing blind spots when the rotational orientation of the housing 1 with respect to the direction of the force F cannot be determined prior to operation.

A single sensing element can be configured in a Wheatstone quarter bridge.

Fig. 2c and 2d show another configuration of the sensing elements 4 with two sensing elements positioned at the transition 23 between membrane 2 and activation member 3 and two sensing elements 4 positioned at the transition 24 between membrane 2 and housing 1 , where another strain peak is located. Two sensing element pairs can e.g. be formed in two Wheatstone half bridges with one pair arranged horizontally and one pair vertically, which has the advantage that, besides bending force magnitude and direction, also compression and tension acting on the activation member 3 can be measured (Fig. 2d).

Fig. 2e shows yet another configuration of four sensing elements 4 in a line positioned at the transition 24 between housing 1 and membrane 2 and the transition 23 between activation member 3 and membrane 2. When configured in a Wheatstone full bridge this configuration has the advantage that the highest strain signal is generated, when a bending force F acts on the activation member 3 in the direction of the strain sensing line.

Fig. 3a illustrates an embodiment of a sensor device 12 for measuring mechano-biological parameters according to the invention for monitoring the loading or deflection of a cephalic bone screw 11 used as a component of a cephalic hip nail for proximal femur fracture fixation. Loading or deflection data may be used to derive digital mobility measures or digital biomarkers to inform physiotherapy and to monitor the rehabilitation process.

Fig. 3b shows a section view of the configuration and a magnification view in Fig. 3c of the sensor device 12 attached to the cannulated cephalic bone screw 11 by an attachment means 7 in form of a thread. The sensor device 12 comprises a hermetic and biocompatible housing 1 , the housing 1 comprising a drive feature 8 for receiving a screw-driver and for controlling the rotational alignment of the sensor device 12 with respect to the anatomy of the patient. The housing 1 further comprises an elastically deformable membrane 2 and an activation member 3 attached to the membrane 2, extending into the cannulation of the cephalic bone screw 11 and having an engagement feature 13 in form of a slotted tip section ensuring spring loaded contact to the walls of the cannulation to transform deflection of the cephalic bone screw 11 under patient loading into displacement of the tip of the activation member 3 resulting in deformation of the membrane 2. The housing 1 further comprises a set of sensing elements 4 in form of strain gauges attached to the inner surface of the membrane 2 and configured to pick up strain on the membrane 2. The set of strain gauges is electrically connected to an electronic unit 9 located inside the hermetic housing 1 in an electronic compartment 10 comprising at least one signal conditioner, at least one analog digital converter, a data processor for collecting raw data and a memory to store the recorded raw data. The electronic unit 9 additionally comprises a wireless data transfer unit connected to the memory and to an antenna 5 via a hermetic feedthrough for transmission of the recoded raw data to a receiving device by means of a wireless communication standard such as Bluetooth, preferably Bluetooth Low Energy, Zigbee or an RFID (radiofrequency identification) based standard, preferably NFC (near field communication). The electronic compartment 10 further comprises a battery 6 to power the electronic unit 9 and the set of strain gauges to enable continuous and autonomous data monitoring for at least 6 months, preferably 12 months post operation without the need for an inductive external power supply or recharging. The electronic unit 9 further comprises at least one, preferably three accelerometers, configured to measure accelerations acting on the sensor device 12 in the three spatial directions as an additional measure for patient mobility. Together with the at least one raw strain signal, the at least one raw acceleration signal is stored in the memory and transmitted to the external receiving device. The at least one accelerometer is further configured to trigger wake and sleep states of the system according to patient activity to save energy. The electronic unit 9 further comprises a temperature sensor to measure, store and transmit ambient body temperature for example for detection of bacterial infection.

Fig. 4a and 4b illustrate another embodiment of a sensor device 12 for measuring mechano- biological parameters according to the invention to measure tension in sutures, cerclages or straps 14 slinged around body tissues, such as muscles, blood vessels, tendons, bones, etc. The sensor device 12 comprises a hermetic and biocompatible housing 1 and attachment means 7 to receive a medical suture 14 or a comparable tensioning device where the suture 14 is attached to or contacts the activation member 3. Tension in the suture 14 as generated by tissue expansions, contractions or movements translates either into a bending force Fbending (Fig. 4a) or a tension force F_tension (Fig. 4b) acting on the activation member 3 depending on the configuration of the attachment means 7. The activation member transmits its displacement to an elastically deformable membrane 2 and to sensing elements 4 (not shown) attached to the membrane 2 for measurement of suture tension.

Yet another embodiment of the sensor device 12 according to the invention is illustrated in Fig. 5a-c for measurement of suture tension during and after a tendon or ligamental repair procedure. The sensor device 12 comprises a hermetic and biocompatible housing 1 with an elastically deformable membrane 2 and an activation member 3 connected to said membrane 2, the activation member 3 being configured to receive or be attached to or connected with a medical suture 14 or a comparable tensioning device for example by means of an eyelet. The medial suture 14 being surgically attached to a torn or injured ligament such as a cruciate ligament or a tendon such as an Achilles- or rotator-cuff tendon or being attached to a bone using a suture anchor or suture button acting as a ligamental brace bridging the injured ligament, the activation member 3 transfers the suture 14 tension to the elastically deformable membrane 2 and to sensing elements 4 (not shown) attached to the membrane 2 for measurement of suture tension intraoperatively or during the biological repair process.

The sensor device 12 further comprises an attachment means 7 to counteract the force exerted by the suture 14 which can be configured as a thread feature on the circumferential surface of a cylindrical housing 1 to be screwed into a bone drill channel as created during ligamental repair surgery (Fig. 5b). Here the sensor device 12 further comprises a drive feature 8 to transmit torque from a screwdriver to the housing.

In Fig. 5a the attachment means 7 is configured as an eyelet receiving another suture 14 which can be connected for example to a suture button placed at the entrance of a bone channel for ligamental repair. This has the advantage that the sensor device 12 can be inserted into the bone channel without turning the housing 1 and thereby twisting the suture 14.

In another embodiment as depicted in Fig. 5c having the advantage that only one suture 14 is used, the suture 14 runs from the ligamental or tendon attachment through an eyelet at the activation member 3 over the housing 1 through another eyelet at the attachment means 7 to a fixation point such as a suture anchor or button. While in Fig. 5a and b a pure tension force F_tension acts on the deformable membrane 2, here also a bending component Fbending is present for measuring suture tension.

Fig. 6a and b show a cross-section view and a magnification view of another embodiment of a sensor device 12 according to the invention to measure loading or deflection of an intramedullary nail 15 implanted in a bone. In between its proximal 17 and distal 16 interlocking holes the intramedullary nail 15 incorporates an elastically deformable membrane 2 and an activation member 3 attached to the membrane 2, extending into the cannulation of the intramedullary nail 15 and having an engagement feature 13 establishing contact to the wall of the cannulation to transform deflection or loading of the intramedullary nail 15 into displacement of the activation member 3 resulting in deformation of the membrane 2 and hence of the sensing elements 4 attached to the inner surface of the membrane 2.

Fig. 6a and b illustrate an embodiment of the invention with the sensor device 12 comprising a separate housing 1 with attachment means 7, which can be threaded or press-fit into the intramedullary nail 15. This configuration offers the advantage that the sensor device 12 can be inserted into the intramedullary nail 15 after its implantation leaving the cannulation empty for guide wire insertion in the first place. However, it is also perceivable that the intramedullary nail 15 serves as housing for the sensor device 12 in an integrated embodiment according to the invention. The intramedullary nail 15 can further comprise antenna outlets 18 to allow for wireless signal transmission by means of the antenna 5.

During the nail insertion procedure, the invention solves the commonly known problem of distal interlocking, where a locking bolt needs to be placed through the distal interlocking holes 16 to secure the intramedullary nail in place. Due to the long distance between the proximal aiming arm attachment point and the distal locking holes 16, nail deflection during insertion prevents use of long rigid aiming arms to guide drill bits and bolts through the holes 16.

A freehand technique must be employed involving excessive X-ray exposure and requiring advanced skills of the operator. A method for use of the sensor device 12 according to the invention to solve the aforementioned problem involves the steps of:

1 . Recording a first reference measurement of the sensing elements 4 before insertion of the intramedullary nail 15 into the bone and calculating the position of the distal interlocking holes in the undeformed state of the nail.

2. Inserting the intramedullary nail 15 into the bone.

3. Recording a second measurement of the sensing elements 4 of the deformed intramedullary nail 15 and calculating the position of the distal interlocking holes in the deformed state of the nail.

4. Calculating the displacement of the distal interlocking holes 16 as a result of intramedullary nail 15 insertion by relating said second to said first measurement at least in the plane normal to the axis of the distal interlocking holes 16.

5. Using the displacement information derived in step 4 for adjusting the drill trajectory of an adaptable aiming arm or a surgical navigation system or a surgical robot.

6. Drilling the pilot holes and inserting the locking bolts by aid of the adjusted aiming arm, surgical navigation system or surgical robot.

After the operation, the intramedullary nail 15 deflects under physiological loading of the patient. This deflection is again transferred to the deformable membrane 2 via the engagement feature 13 and the activation member 3. Continuous measurement of the intramedullary nail deflection over the postoperative period can hence be performed by means of the invention.

Yet another embodiment of a sensor device 12 according to the inventions is depicted in Fig. 7a-c for measurement of the deflection or loading of a bone screw 19, the bone screw 19 accommodating an elastically deformable membrane 2 and an activation member 3 attached to the membrane 2, extending into a cannulation 25 within the shaft of the bone screw 19 and having an engagement feature 13 in contact to the wall of the cannulation to transform deflection of the bone screw 19 into displacement of the activation member 3 resulting in deformation of the membrane 2 and hence of the sensing elements 4 attached to the inner surface of the membrane 2.

Furthermore, the bone screw 19 accommodates an electronic unit 9 electrically connected to the sensing elements 4 and a battery 6 for suppling the electronic unit with electrical energy. The electronic unit 9 further comprises a wireless data transfer unit connected to an antenna 5 via a hermetic feedthrough and the antenna 5 being located outside the hermetically sealed bone screw interior. The bone screw 19 further comprises a drive feature 8 to transmit torque from a screwdriver to the bone screw 19.

As illustrated in Fig. 7a and b, the bone screw additionally comprises an attachment means 7 in form of a thread at its shaft to be inserted into bone or additionally placed through an interlocking hole 16 of an intramedullary nail 15, the bone screw 19 serving as an interlocking bolt.

As illustrated in Fig. 7c, the bone screw can additionally comprise a further attachment means 7 in form of another thread at its screwhead to be locked, for example, into a threaded hole of a bone plate for angular stable fixation.

Fig. 8a-c illustrate another embodiment of a sensor device 12 according to the invention for measurement of the loading or deflection of the connecting rod of a spinal pedicle screw system after spinal stabilization or deformity correction surgery or of the rods or Schanz- pins of an external fixator. The sensor device 12 comprises a hermetic and biocompatible housing 1 , the housing 1 comprising an elastically deformable membrane 2 and an activation member 3 attached to the membrane 2, where the activation member 3 is a cylindrical pin with variable diameter, which poses the advantage of the activation member 3 acting as a hinge at its smaller diameter when transferring spinal rod deflection to the membrane 2. The activation member 3 comprises an engagement feature 13 in form of a first clamp for rigid but releasable attachment to a spinal or external fixator rod by means of a tightening screw 20 to transmit the deflection of the rod under patient loading to the deformable membrane 2. The housing 1 further accommodates a set of sensing elements 4, preferable four strain gauges configured in two Wheatstone half-brides and attached to the inner surface of the membrane 2 to measure rod bending and torsion independently. The sensor device 12 further comprises an attachment means 7 integral with or attached to the housing 1 in form of a second clamp and a second tightening screw 20 aligned with the first clamp to counteract bending and torsion of the rod.

In its electronic compartment 10 the sensor device 12 further accommodates an electronic unit 9, which is electrically connected to the sensing elements 4 and a battery 6 for supplying the electronic unit with electrical energy. The electronic unit 9 further comprises a wireless data transfer unit connected to an antenna 5 via a hermetic feedthrough and the antenna 5 being located outside the hermetically sealed housing 1.

Fig. 9a and b depict yet another embodiment of a sensor device 12 according to the invention for measurement of micromotion and/or migration of a knee endoprosthesis. A sensor device 12 is attached to a tibia component of a knee endoprosthesis 21 with a threaded or conical or press-fit fixation means 7. The sensor device 12 comprises a hermetic and biocompatible housing 1 , the housing 1 comprising an elastically deformable membrane 2 and an activation member 3 attached to the membrane 2, where the activation member 3 has an engagement feature 13 configured to contact the intramedullary walls of the bone and to transmit relative micromotion or migration between the prosthesis stem and the bone via the activation member 3 to the elastically deformable membrane 2. Membrane deformation is then picked up by sensing elements 4 and transmitted to an external receiver wirelessly by means of the antenna 5. In other embodiments the endoprosthesis is a hip or shoulder endoprosthesis.

Fig. 10a (lateral view) and b (posterior view) illustrate yet another embodiment of a sensor device 12 according to the invention for measurement of hindfoot loading F as exerted by a foot in a shoe or boot to the sole 22 and counteracted by the ground reaction. The sensor device 12 comprises a circular cylindrical housing 1 with attachment means 7, in form of a thread or a glue or a press-fit design to secure the housing 1 to a bore in the shoe-sole 22. In a transparent view of the shoe-sole 22, Fig. 10b depicts a configuration of the sensor device 12 inside the sole 22, the housing 1 being located at the lateral or medial aspect of the shoe-sole 22 and the sensor device 12 further comprising an activation member 3 extending in a medio-lateral direction through the sole material. In another configuration the activation member 3 extends from posterior to anterior with the housing 1 being located at the posterior aspect of the shoe-sole 22. The activation member 3 comprises an engagement feature 13 configured to contact the shoe-sole 22 material and being located central underneath the heel contact point to transfer compression of the sole material due to loading of the heel via the activation member 3 to an elastically deformable membrane 2 arranged in or integral with the housing 1. The sensor device 12 further comprises sensing elements configured to pick-up the deformation of the membrane 2 and an electronic unit electrically connected to the sensing elements and configured to wirelessly transmit the measured deformation data by means of an antenna 5 to an external receiver. In yet another configuration one or more sensor devices 12 are located in the shoe-sole 22 at the hindfoot and/or the forefoot region to measure hindfoot and/or forefoot loading.

Fig. 11 illustrates yet another embodiment of a sensor device 12 according to the invention for measurement of the loading or deflection of the connecting rod of a spinal pedicle screw system comprising a cannulated connecting rod 30 and at least two pedicle screws 31 with seat portions 32 for receiving the connecting rod 30 after spinal stabilization or deformity correction surgery or of the rods or Schanz-pins of an external fixator. The sensor device 12, which is attached to the connecting rod 30 or to a cross-link rod by way of a threading 7, comprises a hermetic and biocompatible housing 1. The housing 1 comprises an elastically deformable membrane 2 and an activation member 3 attached to the membrane 2. The activation member s takes the form of a pin which coaxially penetrates into the cavity 34 in the cannulated connecting rod 30. The activation member 3 comprises an engagement feature 13 in the form of a widening, in this case a spring-loaded tip, which is in contact with the interior side of the wall 33 of the rod-cannulation 34 to transmit deflections of the rod, as generated by the pedicle screws 31 under patient loading, to the deformable membrane 2. The housing 1 further accommodates a set of sensing elements 4, preferable four strain gauges configured in two Wheatstone half-bridges and attached to the inner surface of the membrane 2 to measure rod deflection under flexion-extension and lateral bending of the patient independently.

The advantage of this configuration is the ability to monitor the spinal recovery process while accommodating the sensor device 12 at the end of the connecting rod 30, a location where tissue irritation from additional implanted volume is unlikely to occur. LIST OF REFERENCE SIGNS housing 17 proximal interlocking hole interior cavity of 1 18 antenna outlet " thick housing wall 19 bone screw elastically deformable 20 tightening screw membrane 21 knee endoprosthesis ' inner membrane surface 22 sole " outer membrane surface 23 transition area activation member 24 transition area sensing element 25 cannulation antenna 26 outer circumference of 2 battery 27 central portion of 2 attachment means, e.g. 28 framing of 2 in 1 thread 29 surrounding portion of 2 drive feature 30 connecting rod electronic unit 31 pedicle screw0 electronic compartment 32 seat portion in 31 for 301 bone screw 33 wall of cannulated 302 sensor device 34 cannulation/cavity in 303 engagement feature 4 medical suture C compression 5 intramedullary nail F force/displacement6 distal interlocking hole T tension

Claims

1 . Sensor device (12) for detection and preferably also measurement of a force and/or displacement acting in three space directions on at least one activation member (3) of the sensor device (12), wherein the sensor device (12) comprises at least one elastically deformable membrane (2), and at least one sensing element (4), wherein said at least one sensing element (4) is suitable and adapted to detect and measure tension or compression of an elastically deformable material of the elastically deformable membrane (2) on and/or in which the at least one sensing element (4) is located, wherein said at least one elastically deformable membrane (2) is, on an outer portion thereof (26), attached to and/or integral with a framing (28), wherein said at least one elastically deformable membrane (2) comprises a central portion (27) distanced from said outer portion (26), and a surrounding portion (29) circumferentially surrounding said central portion (27), wherein said at least one activation member (3) is attached to and/or integral with said central portion (27), and wherein said at least one sensing element (4) is at least partially provided on and/or integrated with and/or coupled with said surrounding portion (29) of said at least one elastically deformable membrane (2).

2. Sensor device (12) according to claim 1 , wherein said activation member (3) protrudes from a first surface (2") of said elastically deformable membrane (2), and wherein the at least one sensing element (4) is located on said first surface (2") or an opposite second surface (2'), wherein preferably the at least one sensing element (4) is located on said second surface (2'), wherein preferably said activation member (3) takes the form of a pin or a rod, preferably with circular cylindrical cross-section, of constant or variable diameter, preferably with an engagement feature (13) at its tip configured to transmit deformation or loading of a measurement object to the activation member (3).

3. Sensor device (12) according to any of the preceding claims, wherein the activation member (3) is separate and attached, preferably at least one of press-fit or screwed or welded, to a central portion of the elastically deformable membrane (2), or is integral with the elastically deformable membrane (2), and is preferably made of the same material as the elastically deformable membrane (2), wherein the thickness of the elastically deformable membrane (2) is smaller than the minimum dimension of the activation member (3) in a direction parallel to the plane of the elastically deformable membrane (2), preferably by at least a factor of 2 or a factor of 4 smaller.

4. Sensor device (12) according to any of the preceding claims, wherein there are at least 2 sensing elements (4), preferably at least 3 sensing elements (4), or at least 4 sensing elements (4), most preferably in the range of 2-10 or 2-6 sensing elements (4), at least partially attached to and/or integral with said surrounding portion (29), wherein preferably the sensing elements (4) are distributed, preferably regularly, around a circumference of the surrounding portion (29), preferably at least group-wise with equal radial distance from the central portion (27).

5. Sensor device (12) according to the preceding claim, wherein there are provided at least 2 or at least 4 sensing elements (4) which are located adjacent to or at least partially in a transition region between the central portion (27) and the surrounding portion (29), and/or wherein there are provided at least 2 or at least 4 sensing elements (4) which are located adjacent to or at least partially in a transition region between the surrounding portion (29) and the framing (28).

6. Sensor device according to any of the preceding claims, wherein the framing (28) is part of a housing (1) enclosing an interior cavity (1 '), which is preferably hermetically sealed, opposite to a protrusion direction of the activation member (3) and having a housing wall (1") with a housing wall thickness, and wherein the housing wall (1") forms the framing (28), wherein preferably the housing (1), at least in the region of the framing (28), is integral with and preferably consists of the same material as the elastically deformable membrane (2) and preferably of the same material as the activation member (3).

7. Sensor device (12) according to any of the preceding claims, wherein the elastically deformable membrane (2) is a contiguous membrane, preferably with essentially the same thickness over its whole surface extension, and/or wherein the elastically deformable membrane (2) has a polygonal, preferably regularly polygonal shape, or has a rounded shape, preferably an oval and most preferably a circular shape, and/or wherein the framing (28) is part of the housing (1), which in a plane parallel to the plane of the elastically deformable membrane (2) has the same shape of outer and/or inner circumference as the elastically deformable membrane (2), wherein preferably the housing (1) is circular cylindrical, and/or wherein the framing (28) has the same shape of inner circumference as the elastically deformable membrane.

8. Sensor device (12) according to any of the preceding claims, wherein at least 2 sensing elements (4) are configured in at least one Wheatstone half bridge, and/or wherein at least one sensing element (4) is configured in in at least one Wheatstone quarter bridge, and/or wherein at least four sensing elements (4) are configured in in at least one a Wheatstone full bridge, and/or wherein four sensing elements (4) are configured in two independent (Wheatstone) half bridges to pick up two independent strain signals in orthogonal directions.

9. Sensor device (12) according to any of the preceding claims, wherein the at least one sensing element (4) is a resistive foil strain gauge, a capacitive, piezo-based or photoelectric strain gauge, or a combination thereof, and/or wherein the at least one sensing element (4) is attached to and/or integrated into the membrane by a thin film sputtering process.

10. Sensor device (12) according to any of the preceding claims, wherein the activation member (3) comprises an engagement feature (13), which is preferably configured as at least one through-hole for receiving one of the following, a medical suture, fiber, strap band, cerclage-wire or -cable and/or wherein preferably the activation member is directly or indirectly coupled to a medical suture, fiber, strap band, cerclage-wire or -cable, and wherein further preferably said sensor device (12) is configured to measure wire/suture tension either by means of activation member bending, or activation member tension/compression.

11. Sensor device (12) according to any of the preceding claims, wherein the sensor device (12) is integrated and/or attached to and/or housed in a device to be worn by and/or connected to a device implanted in a human being or animal and/or implanted in a human being or animal, preferably in a device selected from the group of medical devices, preferably selected from the group of bone screws, in particular a screw or blade component of a cephalic nailing implant or a sliding hip screw and/or blade or an angular stable locking screw or a compression lag screw or an interlocking bolt or a pedicle screw, or an intramedullary nail, a bone plate, a hip-, knee- or shoulder endoprosthesis, a rod of a spinal pedicle screw system or a rod or Schanz pin of an external fixator system.

12. Sensor device (12) according to any of the preceding claims, wherein the elastically deformable membrane (2) is part of or attached to the housing (1), which is attached to or integrated into a device or itself comprises attachment means (7) for attaching the device to a reference object, wherein preferably the attachment means (7) is configured as at least one of an external or internal thread, as at least one through hole or open or closed eyelet, or as a press-fit member with conical or cylindrical shape, or as a releasable clamp or as a glued connection. and/or wherein the housing (1) comprises a drive feature for engagement with a tool, in particular a screwdriver, and/or wherein the housing (1) is designed as a bone screw or an intramedullary nail.

13. Sensor device (12) according to any of the preceding claims, wherein the device comprises a housing (1) and wherein the housing incorporates an electronic unit (9) with at least one signal conditioner connected to the at least one strain gauge, an analog digital converter, a data processor and a memory to store at least the recorded strain data, where preferably the electronic unit (9) additionally comprises a wireless data transfer unit connected to the memory and to an antenna (5), and wherein further preferably the wireless data transfer unit is based on a wireless communication standard such as Bluetooth, preferably Bluetooth Low Energy, Zigbee or an RFID (radiofrequency identification) based standard, preferably NFC (near field communication) and/or wherein the electronic unit comprises additional sensors connected to the data processor measuring one or a combination of the following dimensions: acceleration of the housing (Accelerometer), angular speed (Gyroscope), location and position (GPS, global positioning system), ambient temperature and/or wherein the housing incorporates a battery (6) configured to supply the at least one strain gauge and the electronic unit with energy, and/or wherein the housing incorporates an energy harvesting device and/or wherein the housing incorporates an RF induction coil

14. Use of the sensor device (12) according to any of the preceding claims to intermittently of continuously monitor the loading or deflection of a bone screw, implanted into a bone, in particular used as a component of a cephalic hip nail after proximal femur fracture fixation, inserted into a locking hole of an intramedullary nail, attached to a bone plate in an angular stable or non- angular stable manner, or to monitor the suture, cerclage or strap tension when slinged around body tissues, or to monitor the suture tension during and after a tendon or ligamental repair procedure, or to monitor loading or deflection of an implanted intramedullary nail, or to intra-operatively measure the deflection of an intramedullary nail during insertion into a bone to guide positioning of the interlocking bolts, or to monitor the loading or deflection of the rods of a spinal posterior instrumentation after spinal stabilization or deformity correction surgery, or to monitor the loading or deflection of the rods or Schanz pins of an external fixator, or to monitor micromotion and/or migration of a knee-, hip- or shoulder endoprosthesis, or to monitor the loading of a foot inside a shoe or boot.

15. Device with a sensor device (12) according to any of the preceding claims 1- 13, to be worn by and/or connected to a device implanted in a human being or animal and/or implanted in a human being or animal, preferably device selected from the group of medical devices, preferably selected from the group of bone screws, in particular a screw or blade component of a cephalic nailing implant or a sliding hip screw and/or blade or an angular stable locking screw or a compression lag screw or an interlocking bolt or a (spinal) pedicle screw, or an intramedullary nail, a bone plate, a hip-, knee- or shoulder endoprosthesis, a (connecting) rod of a spinal pedicle screw system or a rod or Schanz pin of an external fixator system.