Sensor device in the format of a bone screw, nail or pin

Abstract

A sensor device 1 formed as a screw, nail or pin, the device comprising a head 10, shaft 14, and at least one battery cell 50 accommodated in the head or shaft. A sensor housing 40 is arranged beyond

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to a sensor device realised in the format of a bone screw, bone nail or bone pin, as well as associated adapters configured to be used in conjunction with such a sensor device. BACKGROUND

[0002] It is known to incorporate sensor elements in implants, bone plates and bone nails. Such sensors are used to monitor physical parameters that are medically relevant, such as fracture healing, the mechanical stability of an implant or bone plate, and the mechanical stability of a fractured bone to which the implant is attached. Example known sensor elements of this type measure strain on a bone plate screwed to a bone either side of a fracture, monitor loads on a hip prosthesis, and monitor bending of a spinal rod. Specifically, it is known to incorporate the sensor element into a sensor device having the format of a bone screw or bone nail. In this document, the term screw is taken as a synonym for bolt. A bone screw format sensor device can either be screwed into a threaded part of an implant or plate (but not into the patient’s bone), or be screwed into a patient’s bone, for example through a threaded hole in a bone plate. Some published examples of sensor devices that are integrated into bone screws and bone nails are as follows.

[0003] WO2005074821A2 discloses a design of sensor device for monitoring the patient healing process after an implant operation. The sensor device as shown in FIG. 3 of WO2005074821A2 comprises a sensor element, a processor and memory, and a wireless transceiver (telemetry device) powered by an integral battery, which may be wirelessly rechargeable, these components being accommodated in a screw format that can be attached to an implant during surgery and then used to monitor healing through measurement of a relevant physical parameter such as pH-value, oxygen partial pressure, pressure, expansion, acceleration, protein concentration and strain.

[0004] WO2012120439A1 discloses a bone screw format sensor device for monitoring healing. A threaded housing accommodates a sensor element, a processor, a memory, a wireless transceiver and a battery as shown in FIGs. 6 to 8 of WO2012120439A1. The sensor element is disclosed as being any one of many types to sense electrical, chemical, mechanical or optical stresses. It may be a mechanical sensor, a gyrometer, an inclinometer (e.g. a magnetometer), or an accelerometer; a pressure sensor; an electrical conductivity sensor, a temperature sensor a pH sensor; an optical sensor to detect the colour of the surrounding medium.

[0005] WO2016172806A1 discloses in FIG. 6 thereof a sensor device comprising a sensor element and wireless transceiver that is incorporated in an intramedullary bone nail. An intramedullary nail is a structure that is forced into the medullary cavity of a fractured elongate bone, such as the tibia or radius, during surgery. The sensor element is arranged in a hollow interior chamber of the nail and has a wired connection to a data acquisition device arranged near the nail head. The data acquisition device comprises a processor, a memory, a wireless transceiver and a rechargeable battery. The sensor elements are disclosed as being any one of: inductivity meters, capacitance meters, incremental meters strain gauges, particularly wire resistance strain gauges, load cells, piezoelectric pressure sensors, accelerometers, gyroscopes, goniometers, magnetometers and temperature sensors.

[0006] Some other patent publications which disclose sensors for use with implants are the following:

[0007] WO2007090543A1 discloses a sensor device for monitoring the patient healing process after an implant operation. The sensor device has a sensor element and a wireless transceiver. The sensor device is accommodated in a plate which includes a through hole through which a bone screw can pass, to fasten the plate to a bone. Example sensors are a chemical parameter sensor, a temperature sensor and a resistance strain gauge.

[0008] WO2010142045A1 discloses a sensor device for collecting data about bone healing in a patient.

[0009] WO2013112441 Al discloses a design of sensor device for monitoring strain between two parts of a bone either side of a fracture. The sensor device includes multiple strain sensors and a wireless transceiver. The sensor device is accommodated in an elongate plate which includes through holes through which bone screws can pass so that respective end portions of the plate can be screwed onto the two bone parts of a patient with a connecting portion of the plate forming a bridge between the two bone parts across the fracture. The connecting portion is designed to break when subject to a torsion that exceeds a certain threshold.

[0010] WO2019032488Al discloses a sensor device to be attached to an implant in a patient’s body, where the implant may be a bone plate, an intramedullary nail, a bone anchor, a pedicle screw, a spine rod, and an intervertebral implant. The sensor device comprises a sensor and wireless transceiver. Example sensor elements are for sensing strain, load, deflection, rotation, temperature, pressure, pH level, and oxygen level.

[0011] WO2022130127A1 discloses a bone plate incorporating sensor elements for measuring one or more mechanical parameters of the bone plate once screwed onto a bone of a patient. BRIEF SUMMARY OF THE INVENTION

[0012] According to one aspect of the disclosure, there is provided a sensor device formatted as a screw, nail or pin, the sensor device comprising: a head; a shaft extending in a distal direction from the head; at least one battery cell accommodated in the head or shaft; a sensor housing arranged beyond the battery cell in the distal direction, the sensor housing accommodating a sensor element; a wireless transmitter; an antenna formed integrally in the head for wireless communication of data signals to and from the wireless transmitter; and a conductor extending between the antenna and at least one of the wireless transmitter and the sensor element for wired communication of data signals between the wireless transmitter and the antenna and / or wired transmission of electrical power from the antenna to at least one of the wireless transmitter and the sensor element.

[0013] In some embodiments, the sensor device further comprises a bobbin to which the battery cell(s) are mounted. The bobbin has a spindle through which the conductor is routed, e.g., to route the conductor between the antenna and at least one of the sensor element and the wireless transmitter. The spindle may be hollow with the conductor routed through the hollow space or the conductor and spindle may be formed integrally to form a solid element, e.g., filled with insulation and optionally also shielding around a conductor’s metal core. The bobbin may comprise a distal flange with a proximal surface facing the or each battery cell and a distal surface facing the sensor housing. The bobbin may also comprise a proximal flange with a distal surface facing the or each battery cell and a proximal surface facing the head. The proximal flange may include at least one sealed aperture, which, before it is sealed during assembly, allows the or each battery cell to be filled with liquid electrolyte. Moreover, the battery cell(s) may be cylindrical cell(s), each cylindrical cell comprising electrodes and separators that are wound onto the bobbin spindle.

[0014] The head may advantageously be shaped to provide a male or female screw drive having respectively an external or internal polygonal shape to act as driver engaging surfaces. Torque can thereby be applied to the screw, nail or pin format sensor device about the shaft using a complimentary driver. An example external polygonal shape is configured to receive a spanner or nut driver, e.g. an external polygonal shape provided by a plurality of spanner flats that are arranged in parallel pairs for receiving a spanner (e.g. having 4-fold or 6-fold rotational symmetry). An example internal polygonal shape (e.g. having 3-fold, 4-fold, or 6-fold rotational symmetry) is a hexagonal cross-section recess compatible with a hex driver or a recess shaped to be compatible with another pattern of driver, such as a female star-shaped pattern for a torx (registered trade mark) driver.

[0015] In particular, according to a further aspect of the disclosure there may be provided a sensor device formatted as a screw, nail or pin, the sensor device comprising: a head; a shaft extending in a distal direction from the head; at least one battery cell accommodated in the head or shaft; a sensor element; an antenna for wireless communication of data signals; and a wireless transmitter connected to the antenna for wired communication of data signals between the wireless transmitter and the antenna, wherein the antenna is formed integrally in the head, and wherein the head comprises a plurality of spanner flats arranged in parallel pairs for receiving a spanner and thereby applying torque to the screw, nail or pin format sensor device about the shaft. The sensor device may further comprise a conductor extending to connect the wireless transmitter to the antenna.

[0016] In certain embodiments, the sensor element is a strain gauge which is arranged in the sensor housing so as to deform under action of strain acting on the sensor housing. Suitable example strain gauges include a piezoelectric sensor element, a piezoresistive sensor element, a magnetoelastic sensor element, a capacitive strain sensor element and an optical strain sensor (e.g. optical fibre or Fabry P

[0017] With a strain gauge in the sensor housing, the shaft may be provided with a tapered portion extending distal the sensor housing to form a hollow space between the sensor housing and the distal end of the shaft and the sensor device further comprises a rigid element that is arranged in the hollow space, so as to transmit force bearing on the distal end of the shaft onto the sensor housing and thereby onto the strain gauge.

[0018] In particular, according to a still further aspect of the disclosure there may be provided a sensor device formatted as a screw, nail or pin, the sensor device comprising: a head; a shaft extending in a distal direction from the head; at least one battery cell accommodated in the head or shaft; a sensor housing accommodating a sensor element, the sensor element being a strain gauge arranged in the sensor housing so as to deform under action of strain acting on the sensor housing; an antenna for wireless communication of data signals formed integrally in the head; and a wireless transmitter connected to the antenna for wired communication of data signals between the wireless transmitter and the antenna, wherein the shaft has a tapered portion extending distal the sensor housing to form a hollow space between the sensor housing and the distal end of the shaft, the sensor device further comprising a rigid element that is arranged in the hollow space, so as to transmit force bearing on the distal end of the shaft onto the sensor housing and thereby onto the strain gauge. Moreover, the sensor device may further comprise a conductor extending to connect the wireless transmitter to the antenna.

[0019] In certain embodiments, the shaft further comprises an extension portion extending distal to the sensor housing to provide the shaft with additional length. There may be a helical spring arranged in compression in a chamber within the extension portion. Moreover, a male thread may be provided extending along a length portion of the shaft. The male thread may be formed integrally with the shaft or as a separate sleeve that is fitted over the shaft during assembly. The threaded sleeve and shaft are then secured together, which may be by a suitable adhesive bonding, welding or interference fit, for example. Alternatively, nail or pin formats are examples of non-threaded implementations.

[0020] In embodiments in which the sensor element is an electronic component and / or includes an electronic component, and in which the electronic component and wireless transmitter are arranged in the same part of the sensor device, they may be integrated together in a single packaged integrated circuit (so-called chip) or provided as separate components mounted on a common printed circuit board.

[0021] One or more of the above-described screw, nail or pin format sensor devices may form parts in a kit of parts together with a plate, such as a bone plate, or an adapter, such as an adapter for securing a bone screw to an implant rod.

[0022] Specifically, another aspect of the disclosure relates to a kit of parts comprising one or more of the above-described screw format sensor devices bearing a male thread in combination with a plate having a bore with a female threaded length portion complementary to the male thread of the screw format sensor device, so that sensor device can be screw fastened with its male thread into the plate. In certain versions of this kit, the bore in the plate has a further length portion shaped and dimensioned such that, when a sensor device is screw fastened in the plate, the sensor housing is in force transmitting engagement with the further length portion of the bore so that distortion of the plate (e.g. through bending, torsion, thermal expansion or thermal contraction) causes deformation of the strain gauge. In other versions of this kit, the bore is a blind bore terminating in an end surface, the bore being shaped and dimensioned such that, when a sensor device is screw fastened into the plate, the sensor housing is in force transmitting engagement with the end surface of the blind bore so that distortion of the plate (e.g. through bending, torsion, thermal expansion or thermal contraction) causes deformation of the strain gauge.

[0023] A still further aspect of the disclosure relates to a kit of parts comprising one or more of the above-described screw format sensor devices bearing a male thread in combination with an adapter which allows the sensor device to be mounted adjacent a rod. The adapter comprises a passageway enabling the adapter to receive a length portion of a rod; and a female thread defining a thread axis, the female thread being complementary to the male thread of the sensor device, so that a sensor device can be screw fastened to the adapter.

[0024] In certain embodiments of the adapter the passageway extends transverse to the thread axis, whereas in other embodiments the thread axis extends so as to be offset from a rod received in the passageway. The thread axis may extend so as to intersect a rod received in the passageway. Moreover, the female thread of the adapter may be arranged relative to the 5 passageway such that a sensor device can be screwed into the female thread to clamp a rod that is in the passageway to the adapter. Further, when a sensor device is screwed into the female thread of the adapter so as to clamp a rod to the adapter, the sensor housing base may be arranged in force transmitting engagement with the rod. io BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the following, the present invention will further be described by way of example only with reference to exemplary embodiments illustrated in the figures. FIG. 1 is an exploded perspective view of a sensor device in a bone screw format according to a first embodiment of the invention with the battery cell omitted. FIG. 2 is an exploded perspective section view of the sensor device of FIG. 1 with the battery cell omitted. FIG. 3 is a perspective view of the sensor device of FIG. 1 in assembled form with the battery cell omitted. FIG. 4 is an exploded perspective section view of the sensor device of FIG. 1 with the battery cell fitted. FIG. 5 is a perspective view of the sensor device of FIG. 1 in assembled form with the battery cell fitted. FIG. 6 is a perspective view of the sensor device of FIG. 1 in assembled form. FIG. 7 is a perspective view of the sensor device of FIG. 1 fitted in a bone or implant plate. FIG. 8 is a perspective section view of the sensor device of FIG. 1 fitted in a bone or implant plate. FIG. 9 is a perspective view of the sensor device of FIG. 1 arranged adjacent an implant rod via an adapter according to a first adapter embodiment. FIG. 10A is a perspective section view of the sensor device of FIG. 1 arranged adjacent an implant rod via an adapter according to the first adapter embodiment. FIG. 10B is a horizontal section taken from FIG. 10A, the section being in the xz-plane through the mid-plane in the rod as shown by the dot-dashed lines in FIG. 10A. FIG. 11 is a perspective view of the sensor device of FIG. 1 arranged adjacent an implant rod via an adapter according to a second adapter embodiment. FIG. 12 is a perspective view of the sensor device of FIG. 1 arranged adjacent an implant rod via an adapter according to a third adapter embodiment. FIG. 13 is a perspective section view of the sensor device of FIG. 1 arranged adjacent an implant rod via an adapter according to a third adapter embodiment. FIG. 14 is an exploded perspective section view of a sensor device in a bone screw format using the sensor device of FIG. 1 when fitted with a first alternative form of cover. FIG. 15A is a perspective section view of a second alternative form of cover. FIG. 15B is a perspective section view of a third alternative form of cover. FIG. 15C is a perspective section view of a fourth alternative form of cover. FIG. 16 is a perspective section view of the bone screw format sensor device of FIG. 1 when fitted with the sensor cover of FIG. 15A, the sensor device being screwed into an adapter in an arrangement for measuring strain on an implant rod. FIG. 17 is a perspective view of a sensor device in a bone screw format according to a second embodiment of the invention. FIG. 18 is a section perspective view of FIG. 17 with the battery cell omitted. FIG. 19 is a perspective view of a sensor device in a bone screw format according to a third embodiment of the invention fitted in a bone or implant plate. FIG. 20 is a section perspective view of FIG. 19 with the battery cell omitted. FIG. 21 is a perspective view of a sensor device in a bone screw format according to a fourth embodiment of the invention fitted in a bone or implant plate. FIG. 22 is a section perspective view of FIG. 21 with the battery cell omitted. FIG. 23 is a schematic block diagram showing a sensor device embodying the invention arranged within a Medical Device Communication System (MDCS). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In the following detailed description, for purposes of explanation and not limitation, specific details are set forth in order to provide a better understanding of the present disclosure. It will be apparent to one skilled in the art that the present disclosure may be practiced in other embodiments that depart from these specific details. Like reference numerals are used for like parts in the different embodiments.

[0027] The embodiments of the invention described in the following detailed description are based around a sensor device formatted as a screw. Related embodiments in a nail or pin format, i.e., non-threaded, will be readily understood. Moreover, in the following detailed description, the sensor device is described as containing one or more sensors and in particular as including a strain gauge. Suitable example types of strain gauge include a piezoelectric sensor element, a piezoresistive sensor element, a magnetoelastic sensor element, a capacitive strain sensor element and an optical strain sensor (e.g. optical fibre or Fabry-Perot). In the following detailed description, when the strain gauge is referred to as a piezoresistive sensor element, this is by way of example only.

[0028] It will be understood that the wireless transmitter may be formed as a wireless transceiver. Indeed, this will be necessary when data is transmitted using a data transmission protocol which requires bidirectional communication but not if a unidirectional data transmission protocol is used. Example suitable unidirectional data transmission protocols are Manchester, Bi-Phase, or NRZ data encoding. On the other hand, a bidirectional data communication protocol will be used when a WPAN transceiver is employed. A WPAN transceiver will be configured to operate using a suitable WPAN protocol, which are bidirectional in nature, such as Bluetooth Low Energy (BLE), Medical Implant Communication System (MICS) or Medical Device Radiocommunications Service (MedRadio). In the following detailed description, when the transmitter is referred to as a transceiver, this is by way of example only.

[0029] FIGs. 1 to 6 show different views of the same sensor device 1 according to a first embodiment of the invention.

[0030] FIG. 1 is an exploded perspective view of the bone screw format sensor device 1, with the ‘explosion’ of the parts being axial to the principal axis of the bone screw format sensor device 1. The principal parts of the bone screw format sensor device 1 are its head 10 and shaft 14. Within the shaft 14 there is arranged a battery cell 50 (not shown in FIG. 1) that is wound on a bobbin (or spool) 30. In FIG. 1, the battery cell 50 is not shown in order to provide a clear view of a bobbin 30. The bobbin 30 is for accommodating the battery cell 50 as described in more detail below. The bobbin has a spindle 31. Each end of the spindle 31 is attached to circular flanges 32, 36. The flange 32 that is nearest to the head 10 is referred to as the proximal flange 32. The flange 36 that is farthest from the head 10 is referred to as the distal flange 36. Generally, in the following we use the terms distal and proximal with reference to the direction or distance away from and towards the head 10 respectively.

[0031] FIG. 2 is an exploded perspective section view of the sensor device 1 with the battery cell 50 omitted. FIG. 3 is a perspective view of the sensor device 1 in assembled form with the battery cell 50 omitted. FIG. 4 is an exploded perspective section view of the sensor device 1 with the battery cell 50 included. FIG. 5 is a perspective view of the sensor device 1 in assembled form with the battery cell 50 fitted. FIG. 6 is a perspective view of the sensor device 1 in assembled form.

[0032] Referring principally to FIGs. 1 to 3, the basic structural components of the bone screw format sensor device 1 are: the head 10 and the shaft 14. The shaft 14 includes the spindle 30 for mounting of a battery cell 50 (omitted from FIGs. 1 to 3 but shown in FIG. 4) as well as a sensor housing 40 and a cylindrical cover 20. The shaft 14 further includes a threaded sleeve 21 which bears a male thread. The sleeve 21 is fitted over and attached to the outside cylindrical surface of the cover 20, e.g., by suitable bonding or fastening. In alternative embodiments of a bone screw format sensor device 1, the cover 20 and sleeve 21 may be integrated as one piece of material.

[0033] The sensor housing 40 accommodates a sensor element 45, such as a strain gauge. The sensor element 45 is arranged in the sensor housing 40 so that it deforms under action of strain acting on the outside of the sensor housing 40 either axially through the sensor housing base 42 or laterally through the sensor housing sidewall 44. The sensor housing 40 also accommodates electronics components, e.g., in a chipset, for supporting the sensor functions, such as obtaining, storing, pre-processing and transmitting sensor signals. The electronics components provide computing and telecommunications resource. The electronics components include a wireless transceiver 46, such as a wireless personal area network (WPAN) transceiver, a memory 47 and a processor 48. The wireless transceiver 46 is operable to wirelessly transmit sensor data collected by the sensor element 45 as well as optionally also to receive control signals, e.g., for sensor configuration, and signals to prompt a transmission of collected sensor data. The sensor housing 40 has a cylindrical shape formed by the sensor housing base 42 which is flat and circular in combination with the sidewall 44 which is cylindrical.

[0034] An antenna 15 for external wireless data communication is formed integrally in the head 10. The antenna 15 is connected to the wireless transceiver 46 via an electrical conductor 16. The conductor 16 is routed from the wireless transceiver 46 to the antenna 15 through the bobbin spindle 31 so that data signals can flow between the wireless transceiver 46 and the antenna 15 for transmitter and receiver action. A further conductor may also be similarly routed to provide an electrical power line, e.g., to allow power to be transmitted from the antenna to the wireless transceiver, the electrical power being picked up inductively by the antenna. The antenna connection conductor 16 is made of a suitable electrical conductor, e.g. solid copper, and is shrouded with a suitable insulator 17, e.g. polyethylene, which in turn is surrounded by a conductive shield 18, e.g. copper braid or mesh or tube, the conductor 16, insulator 17 and shield 18 thus having the form of a coaxial cable. As visible in FIG. 1, where the top part of the head 10 is cut away, the antenna 15 has a spiral shape with an arc of somewhat less than one full turn which spirals out from the centre of the head 10, i.e., from the principal axis of the bone screw format sensor device 1. The axially located antenna end is electrically connected to the proximal end of the conductor 16 where it emerges from the proximal end of the spindle 31, and to the proximal flange 32, forming, in this example, an inverted F-type antenna (IFA). The head 10 is made at least partially of a material which is transparent to radio waves of the frequency band of operation of the wireless transceiver 46, such as a plastics material such as a polymer. Specific examples of plastics materials are polyether ether ketone (PEEK), polymethyl methacrylate (PMMA), polyethylene (PE), polypropylene (PP) and polycarbonate (PC). As can be seen in FIG. 2, the antenna may be embedded in the plastics material of the head 10.

[0035] FIG. 4 shows that the battery cell 50 is a cylindrical cell with multiple layers of electrodes and separators that are wound onto the bobbin spindle 31 to a radius equal to or somewhat less than the radius of the flanges 32, 36, such as with a so-called jellyroll. An alternative battery cell format compatible with mounting on the bobbin spindle 31 is a stack of multiple layers, each shaped as a disk with a central through hole, the disks being stacked in the axial direction of the spindle. The head 10 and proximal bobbin flange 32 are provided with respective through-holes 12 and 34 which are aligned and together form an aperture through which the battery cell 50 can be filled with liquid electrolyte during assembly, after which filling the aperture is sealed with a ball seal 5. It will be understood that this is an optional feature which may be omitted, e.g., if a solid electrolyte is used for the battery cell 50.

[0036] An alternative construction would be to arrange a plurality of cylindrical battery cells, e.g., 3, 4, 5 or 6, symmetrically about the bobbin. The individual battery cells would then not be wound onto the spindle but rather be structurally independent cells constructed, for example, as stacked or jellyroll batteries. The maximum possible total cell volume, and hence cell energy, would however be reduced compared to the illustrated arrangement with a single battery cell wound onto the bobbin. Because of the spaces between the battery cells, there would then be more options for routing the conductor 16 from the wireless transceiver 46 to the antenna 15, although routing the conductor 16 axially through the bobbin spindle 31 would still be an efficient design implementation.

[0037] It is noted that the head 10 has the shape of a screw head with a plurality of spanner flats 11 arranged in three parallel pairs to form a hexagon (with chamfered corners). The head 10 is thus shaped to allow a spanner (synonym wrench) or socket bit to apply torque to the screw, nail or pin format sensor device, e.g., to screw or unscrew the bone screw 1 into a receiving female thread or into bone tissue in the manner of a self-tapping screw. This is an example of shaping the head to provide a male screw drive having an external polygonal shape. In this example, the spanner flats 11 collectively or pairwise act as driver engaging surfaces for a socket bit or spanner. Other external polygonal shapes are also possible, e.g., square, with the flats arranged in parallel pairs.

[0038] The battery cell 50 acts as a power supply for the electronic components of the sensor device 1. The battery cell 50 may be a primary cell (i.e. non-rechargeable) or a secondary cell (rechargeable). In the case of a secondary cell, there is the additional technical challenge of being able to recharge the battery while implanted in a patient, which would typically need to be done wirelessly by an additional inductive loop and would require careful heat management to avoid tissue damage, so would most likely only be practical if the sensor device was implanted subcutaneously close to the skin surface. The battery cell 50 will therefore likely be a primary cell for any bone screw uses where the bone screw is deep inside the patient.

[0039] While FIGs. 1 to 6 show a sensor device 1 in bone screw format, it is also possible to realise the sensor device 1 in bone nail or pin format. This is achieved by omitting the male threaded sleeve 21. It will be further understood that in a bone nail or pin format it is not necessary for the structure to have a circular cross-section. For example, the structure could have a tapering square, pentagonal, hexagonal, octagonal or other regular polygonal crosssection or a non-polygonal or non-regular-polygonal cross-section.

[0040] FIG. 7 is a perspective view of the sensor device 1 of FIGs. 1 to 6 fitted in a bone or implant plate 60 with FIG. 8 being a section view of FIG. 7. The bone plate 60 has a plurality of through-holes or bores 61 bored through it, each of which has an upper female threaded length portion 62 and a lower smooth length portion 63. The length portions 62, 63 are so configured that when the sensor device 1 is screwed into the bore 61 the cylindrical wall 44 of the sensor housing 40 is in a clearance fit. The clearance fit ensures that the sensor housing slides into the bore’s lower length portion 63 unimpeded when the bone screw is screwed in while also ensuring that its proximity to the internal surface of the lower length portion 63 of the bore results in the plate exerting lateral force on the cylindrical wall 44 if the plate 60 bends. Alternatively, if the smooth length portion is tapered, the sensor device may be screwed into the bore with the edge of the sensor housing contacting the smooth length portion. In this way the plate 60 may also exert a lateral force on the cylindrical wall 44 upon bending of the plate 60. The piezoresistive sensor 45 is mounted on the proximal surface of the sensor housing base 42 and experiences a strain via displacement of the sensor housing sidewall 44 that is actuated by the lower length portion 63 of the bore when the plate 60 bows such that its illustrated ends are lower in the y-direction than the middle of the plate where the bone screw format sensor device 1 is located. The piezoresistive sensor element 45 thus provides a signal which increases with increased bending of the plate 60, thereby acting as a strain gauge for bending of the plate 60. The piezoresistive sensor 45 will also be sensitive to twisting of the plate 60 through torsional loading. An example bending moment acting on the plate 60 is shown schematically with the arrows M and the resultant forces that cause strain on the piezoresistive sensor element 45 through the sensor housing 40 are shown with the arrows labelled F C for the compression or pinching force or stress acting in the lower portion of the plate 60 in the positive and negative z-directions onto the sidewall 44 of the sensor housing 40 and with the arrows labelled F_E for the stretching forces acting in the negative and positive z-directions through the bone screw format sensor device 1 in the plate upper portion 62. Upon bending of the plate in the direction shown by the arrows M, the plate lower part 63 exerts compression forces F C on the sensor housing 40 and thus the piezoresistive sensor element 45 is strained.

[0041] The cross-sectional plane where the material does not experience any longitudinal stress in response to bending is referred to as the neutral plane. In the example shown here of a plate, this will be the xz-plane at the half-thickness of the plate. The further the sensor housing is arranged away from the neutral plane the more pinching stress per unit bending will act on the sensor housing, resulting in more strain per unit plate bending acting on the piezoresistive sensor. The upper portion of the plate experiences an elongation or stretching.

[0042] FIG. 9 is a perspective view of the sensor device 1 of FIGs. 1 to 6 arranged adjacent a rod 80 via an adapter 70 according to a first adapter embodiment. FIG. 10A is a section view of FIG. 9. FIG. 10B is a horizontal section taken from FIG. 10 A, the section being in the xz-plane through the mid-plane in the rod 80 as shown by the dot-dashed lines in FIG. 10A. The rod 80 may for example be a spinal rod as fitted during back surgery, for example a Harrington rod for treating curvature of the spine (scoliosis). The adapter 70 is formed with a passageway 74 which is open towards the x-direction allowing a length portion of the rod 80 to be accepted into the passageway. The passageway 74 and rod 80 have complementary cross-sectional dimensions for this purpose. The adapter 70 captures a length portion of the rod 80 securely in the open passageway 74 by means of grub screws 75 (not shown) screwed into a pair of threaded bores 76 extending in the y-direction that are arranged in flange portions of the adapter 70. The rod 80 is thus held in the adapter 70 at two fixed points that are a distance 7’ apart such that bending of the rod between these two fixed points is detected as strain by the piezoresistive sensor element 45. The adapter 70 shown in FIGs. 9, 10A and 10B measures bending of the rod in the yz-plane in a similar way to the plate example of FIGs. 7 &8 in that the rod bending in the direction shown in FIG. 10A by the bending moments M bears laterally on the sidewall 44 of the sensor housing 40 with a compression force F C while an elongation force F_E occurs through the adapter 70. The neutral plane, when the rod 80 bends as indicated in FIG. 10A by the arrows M, is the yz-plane that intersects the rod’s principal axis. The rod principal axis is shown by the dotted line in FIG. 10B. The piezoresi stive sensor element is mounted on the proximal surface of the sensor housing base 42 and experiences a strain via bending of the sensor housing base 42 induced by bending of the adapter 70 in response to bending of the rod 80. As visible in FIG. 9, a pair of slots 78 are provided in the adapter 70 to cause thinning of a middle portion of the adapter 70 which increases the flexibility of the adapter 70 to respond to bending of the rod 80 about the central axis of the sensor device 1. The piezoresistive sensor element 45 thus provides a signal which increases with increased bending of the rod 80, thereby acting as a strain gauge for bending of the rod 80.

[0043] FIG. 11 is a perspective view of the sensor device 1 of FIGs. 1 to 6 arranged adjacent an implant rod 80 via an adapter 70 according to a second adapter embodiment. The adapter 70 captures a length portion of the rod 80 securely in the open passageway 74 by means of a pair of grub screws 75 screwed into a pair of threads 76 extending in the x-direction that are arranged in flange portions of the adapter 70. The rod 80 is thus held in the adapter 70 at two fixed points that are a distance 7’ apart such that bending of the rod in the yz-plane between these two fixed points is detected as strain by the piezoresistive sensor element 45.

[0044] FIG. 12 is a perspective view of the sensor device 1 of FIGs. 1 to 6 arranged adjacent an implant rod 80 via an adapter 70 according to a third adapter embodiment with FIG. 13 being a section view of FIG 12. The adapter 70 is in the form of so-called tulip and has an open passageway 74 comprising an upper, female threaded length portion 72 for receiving a bone screw format sensor device 1 and a lower, unthreaded length portion 73 for receiving the sensor housing 40. The bone screw format sensor device 1 is received in the passageway 74 such that the distal surface of the sensor housing base 42, which is planar and extends in the xz-plane, is arranged tangentially to a length portion of the rod 80. The piezoresistive sensor element 45 is thus able to measure bending of the rod 80 in the yz-plane. An example bending moment acting on the rod 80 is shown schematically with the arrows M and the resultant forces that cause strain on the piezoresistive sensor element 45 are shown with the arrow labelled F_S for the force acting in the y-direction from the rod 80 onto the under or distal side of the sensor housing 40 and with the arrow labelled FT for the reaction force acting in the negative y-direction through the walls of the tulip-like adapter 70.

[0045] FIG. 14 is an exploded perspective section view of a sensor device in a bone screw format using the sensor device of FIG. 1 when fitted with a first alternative form of cover. Instead of the cover 20 terminating at its distal end with an open cylinder as in the embodiment of FIG. 4, the distal end of the cover 20 has a tapered end formed by conically tapering walls 22 that terminate at a point 29. The conical taper 22 forms a hollow interior space underneath, i.e., on the distal side of, the sensor housing base 42 in which a ball bearing 25 is arranged. The ball bearing 25 is seated in the conical taper and, at its uppermost, i.e., most proximal point, in contact with the sensor housing base 42. The contact point being along the axis of the cover 20. The ball bearing 25 serves as a rigid element for force transmission from the distal point 29 of the cover 20 to the sensor housing base 42, so that a sensor element 45 attached to the proximal surface of the sensor housing base 42 acts as a strain gauge.

[0046] FIGs. 15A to 15C show in perspective section view three alternative forms of the cover 20 that can be used instead of the cover shown in FIG. 4 or FIG. 14, i.e., all these cover types are compatible with the same sub-assembly as shown in the upper part of FIGs. 4 &14, the sub-assembly being formed by the head 10, bobbin / battery cell 30 / 50 and sensor housing 40. These are all shown as having a threaded sleeve 21 to provide a bone screw format but the threaded sleeve could be omitted to provide a bone nail format.

[0047] FIG. 15A is a perspective section view of a second alternative form of cover. A solid extension 23 extends from the distal side of the conical taper 22 such that a waisted portion 26 is formed. The waisted portion 26 acts as a bellows by deforming in response to a force acting upwards on the point 29 of the cover 20. The bellows action lowers the axial stiffness of the cover leading to more strain being translated to the strain gauge in response to a given force being applied axially to the taper point 29. The single bellows shown here, can be extended to several bellows, i.e., multiple waists arranged in sequence, to lower the axial stiffness still further and thus translate even more strain per unit of applied force to the strain gauge, making the strain gauge even more sensitive.

[0048] FIG. 15B is a perspective section view of a third alternative form of cover. Compared with the cover design of FIG. 15A the extension 23 is hollow being provided with an internal chamber 28 in which a helical spring 27 is arranged in compression to spring-load the ball bearing 25. The spring 27 lowers the sensitivity of the strain gauge allowing larger forces to be measured by the strain gauge. The spring 27 causes a larger proportion of force applied to the point 29 to be routed to the upper side walls of the cover (where the thread 21 is shown) so that the maximum strain that can be tolerated by the strain gauge 45 is increased.

[0049] FIG. 15C is a perspective section view of a fourth alternative form of cover. This cover design lowers the strain gauge sensitivity still further. In comparison to the cover design of FIG. 15B, the waisted portion 26 is replaced with thicker solid sidewalls, so there is no longer a bellows action. This more rigid design allows the strain gauge to measure even higher forces, since a very high proportion of force applied axially to the point 29 is transferred to the cover sidewalls with only a small proportion reaching the spring-loaded ball bearing 25.

[0050] The purpose of the distal extension 23 of the cover 20 shown in Figs. 15 A, 15B and 15C is to transfer a force applied at the distal end 29 of the cover extension 23 at various proportions to the sensor housing 40 and thus the strain gauge 45. The remainder of the force is transmitted to the plate 60 or adapter 70 in which the device 1 is mounted via the screw thread 21 / 62 or 21 / 72. The greater the axial stiffness of the cover extension 23, the lower the force transmitted to the sensor housing 40. With a distal extension 23 of a given yield strain (above which it plastically deforms), it is therefore possible with the respective designs of Figs. 15 A, 15B and 15C to allow successively higher forces to be applied to the tip 29 with respective greater proportions of force attenuation of the force transmitted to the sensor housing 40, thereby avoiding plastic deformation.

[0051] In summary, it is possible to provide multiple different cover designs which can all be fitted to the same sub-assembly of head 10, bobbin / battery cell 30 / 50 and sensor housing 40 such that the same strain gauge can be re-used with different cover designs to provide different sensitivity ranges for force applied axially to the cover distal point 29.

[0052] FIG. 16 is a perspective section view of the bone screw format sensor device of FIGs. 1 to 6 when fitted with the cover of FIG. 15 A, the sensor device being screwed into an adapter 70 that is an intermedullary nail (only upper portion illustrated) in an arrangement for measuring strain on a locking screw 80 (external thread not shown). The intermedullary nail 70 has a hollow cylindrical shape with a central axial bore. The central axial bore of the intermedullary nail 70 has an upper threaded portion 72 providing a female thread into which the male thread 21 of the bone screw format sensor device 1 of FIG. 1 can be screwed. The screw format sensor device 1 is thus performing the role that is conventionally fulfilled by a set screw. The intermedullary nail 70 also has a passageway 74 formed by a bore at right angles through the sidewalls of the hollow cylinder of the intermedullary nail 70. The passageway extends transverse to the thread axis that receives the bone screw format sensor device. The passageway is of a defined cross-section, here circular with a certain diameter, to enable the intermedullary nail 70 to receive the locking screw 80, which is of complementary cross-sectional dimensions. Bending of the locking screw 80 thus transmits force axially to the point 29 of the bone screw format sensor device 1 allowing the sensor device’s strain gauge to measure the strain. It is noted that the locking screw is shown as solid but may also be cannulated.

[0053] While the above embodiments have described the sensor housing as containing a strain gauge to measure strain in the axial or lateral directions, the sensor housing may incorporate other sensor types either in combination with a strain gauge or instead of a strain gauge. By way of example, these may be one or more of the following sensor types: temperature sensor, pH-value sensor, pressure sensor (e.g. oxygen partial pressure), expansion sensor, protein concentration sensor, gyroscope, inclinometer (e.g. a magnetometer), accelerometer; electrical conductivity sensor, inductivity meter, capacitance meter, wire resistance strain gauge, electrochemical sensor, immunosensor, enzymatic sensor, ion sensor. The sensor may also be an optical sensor, or combination of light source and optical sensor, to detect the colour or spectral properties of the surrounding medium through a window formed in the sensor housing, e.g., in the base or sidewall, e.g. the light of a specific fluorescent substance, either naturally occurring or added as a fluorescent label, emitted upon excitation with the light source. The optical sensor may also be configured and arranged to detect the temporal evolution of scattered light or fluorescence emitted, e.g. to count cells as in a flow cytometer.

[0054] FIG. 17 is a perspective view of a sensor device 1 in a bone screw format according to a second embodiment of the invention. FIG. 18 is a section perspective view of FIG. 17 with the battery cell omitted. With reference to FIG. 17, the bone screw format sensor device 1 of the second embodiment has a similar external structure to that of the first embodiment with a head 10 and shaft 14. The head 10 is facetted with spanner flats 11 that form a hexagonal shape for receipt of a spanner or socket set bit. An antenna 15 for external wireless data communication is integrally formed in the head 10 as in the first embodiment. The shaft 14 comprises a cylindrical cover 20, which has an integral male thread 21 extending over a length portion of the cover’s outer cylindrical surface. Alternatively, the thread could be formed in a separate sleeve fitted over the cover as illustrated in connection with the first embodiment. Referring to FIG. 18, it can be seen that in this second embodiment the component design in the interior volume of the sensor device 1 differs from that of the first embodiment. A cylindrical battery compartment 52 is provided for accommodating a standard cylindrical battery cell, i.e., a a battery cell without a cannulated bobbin as in the first embodiment. The advantage of the design of the second embodiment compared to the first embodiment is that a standard battery cell can be used rather than a custom-manufactured battery cell as needed for the first embodiment. The disadvantage is however a less efficient space utilization compared with the first embodiment, so that for a given external dimension, there is a reduced volume for the battery cell. In the second embodiment, the cover 20 in its lower portion also forms a housing for a sensor 45, in particular a strain gauge. Alternatively, a separate sensor housing could be provided as illustrated for the first embodiment.

[0055] The cover 20 accommodates a sensor element 45, such as a strain gauge. The cover 20 has a cylindrical shape formed by the cover base 42 which is flat and circular. In an alternative, the cover base 42 may be conical to terminate in a sharp or rounded tip. The sensor element 45 is bonded to the cover base 42, so that the sensor element 45 deforms under action of strain acting on the outside of the cover 20. The cover 20 also accommodates electronics components, e.g., in a chipset, for supporting the sensor functions, such as obtaining, storing, pre-processing and transmitting sensor signals. The electronics components provide computing and telecommunications resource. The electronics components include a wireless transceiver 46, such as a wireless personal area network (WPAN) transceiver, a memory 47 and a processor 48. The wireless transceiver 46 is operable to wirelessly transmit sensor data collected by the sensor element 45 as well as optionally also to receive control signals, e.g., for sensor configuration, and signals to prompt a transmission of collected sensor data. If the wireless transceiver is a WPAN transceiver then it will be configured to operate using a suitable WPAN protocol such as Bluetooth Low Energy (BLE), Medical Implant Communication System (MICS) or Medical Device Radiocommunications Service (MedRadio). In the second embodiment, the wireless transceiver 46 is arranged on the proximal side of the battery compartment 52 so that it is adjacent the head 10 and antenna 15. Sensor signal from the sensor element 45 is routed to the electronics components, in particular to the wireless transceiver 46, through an electrical connector 49. The electrical connector 49 is routed around the outside of the battery compartment 52 through a channel provided between the outer surface of the battery compartment housing 54 and the inner surface of the cover 20. The channel can be provided by a chamfer in the outer cylindrical surface of the battery compartment housing 54 and / or a recessed groove in the inner surface of the cover 20. A battery cell 50 of suitable shape is shown schematically in the inset, showing a cylindrical shape as would have a conventional cell formed by wound or stacked electrodes and separators into a cylindrical bundle.

[0056] FIG. 19 is a perspective view of a sensor device 1 in a bone screw format according to a third embodiment of the invention which is fitted in a bore 61 / 62 of a bone or implant plate 60. FIG. 20 is a section perspective view of FIG. 19 with the battery cell omitted. In the third embodiment, a battery compartment 52 is formed within the head 10 of the sensor device 1. The battery compartment 52 is defined by a two-piece housing 54 having an upper cap-like piece and a disk-shaped lower piece. A battery cell 50 of suitable shape is shown schematically in the inset, showing a hollow cylindrical shape with a flat aspect ratio dimensioned to fit into the battery compartment 52. It will be understood that a battery cell with such a disk-like shape will most likely be formed as a stack (rather than rolled or wound). Fitting the battery compartment inside the head 10 has an advantage when the volume available in the shaft 14 is insufficient to meet the specified capacity needed for the battery cell. This may be as a result of a smaller diameter plate bore and / or a thinner plate into which the sensor device 1 is to be fitted. In the third embodiment, the wireless transceiver 46 is arranged on the distal side of the battery compartment 52 in an upper / proximal portion of the cover 20 adjacent the head 10 and antenna 15. The sensor element 45 at the cover base 42 is electrically connected to the electronics components, in particular to the wireless transceiver 46, through a folded flex connector 49 which forms an electrically conducting connection by soldering or other suitable bonding technique. The bone plate 60 has a plurality of through-holes or bores 61 bored through it, each of which has an upper female threaded length portion 62 and a lower smooth length portion 63. The length portions 62, 63 are so configured that when the sensor device 1 is screwed into the bore 61 the cylindrical wall of the cover 20 adjacent the strain sensor 45 is in a clearance fit. The clearance fit ensures that the unthreaded distal end portion of the cover 20 slides into the bore’s lower length portion 63 unimpeded when the bone screw is screwed in while also ensuring that its proximity to the internal surface of the bore’s lower smooth length portion 63 results in the plate 60 exerting lateral force on the distal end portion of the cover 20 if and when the plate 60 bends. Alternatively, if the bore’s smooth end portion 63 is tapered, the sensor device 1 may be screwed into the bore 61 with the edge of the unthreaded part of the cover 20 contacting the smooth length portion 63. In this way the plate 60 may also exert a lateral force on the distal end portion of the cover 20 upon bending of the plate 60. The piezoresistive sensor 45 is mounted on the proximal surface of the cover base 42 and experiences a strain via displacement of the cover sidewall that is actuated by the lower length portion 63 of the bore when the plate bows such that its illustrated ends are lower in the y-direction than the middle of the plate where the bone screw format sensor device 1 is located. The piezoresistive sensor element 45 thus provides a signal which increases with increased bending of the plate 60, thereby acting as a strain gauge for bending of the plate 60. The sensor will also be sensitive to twisting of the plate 60 through torsional loading. An example bending moment acting on the plate 60 is shown schematically with the arrows M and the resultant forces that cause strain on the piezoresistive sensor element 45 through the sensor housing 40 are shown with the arrows labelled F C for the compression or pinching force or stress acting in the lower portion of the plate in the positive and negative z-directions onto the cover sidewall and with the arrows labelled F_E for the stretching forces acting in the negative and positive z-directions through the bone screw in the plate upper portion 62. Upon bending of the plate in the direction shown by the arrows M, the plate lower part 63 exerts compression forces F C on the adjacent length portion of the cover 20 and thus the piezoresistive sensor element 45 is strained.

[0057] FIG. 21 is a perspective view of a sensor device 1 in a bone screw format according to a fourth embodiment of the invention which is fitted in a bore 61 / 62 of a bone or implant plate 60. FIG. 22 is a section perspective view of FIG. 21 with the battery cell omitted. The head 10 is shaped to provide a female screw drive having respectively an internal polygonal shape. Torque can be applied to the screw format sensor device about the cover 20 using a complimentary driver. In this example, the polygonal shape is suitable for receipt of a male star-shaped bit in the proprietary ‘torx’ (registered trade mark) format. The illustrated pattern has 6-fold rotational symmetry. Another example internal polygonal shape would be of hexagonal cross-section for receiving a standard hex driver, this also being of 6-fold rotational symmetry. The antenna 15 is illustrated as having a diameter less than the minimum inside diameter associated with the female screw drive. Alternatively, the antenna may have a larger diameter, if arranged in the head deeper than, i.e., below the female screw drive recess. Referring to FIG. 22, it can be seen that the other features of the sensor device 1 are similar to those of the third embodiment as shown in FIG. 20, so are not described again here.

[0058] FIG. 23 shows the above-described sensor device 1 in a system context, namely within a standard architecture of a Medical Device Communication System (MDCS) 100. The MDCS 100 provides for communication between the sensor device 1, in particular when implanted in a patient, and a remotely located data centre 160, which is accessible to health care staff using suitable application software. In case the battery cell 50 is a secondary cell, the battery cell 50 can be charged in a contactless manner by a charger 123, for example a resonant inductive charger, which is placed on the patient's skin adjacent the implanted sensor device 1. The charger 123 is itself provided with an energy source 124, here a rechargeable battery 124, as well as an external mains power connection 129, for example an external power jack, to power the charger 123 so that its rechargeable battery 124 can be recharged. Alternatively, the charger's battery 124 can be recharged wirelessly by placing the charger 123 on a mains-powered charging pad.

[0059] The patient is provided with a patient remote controller 130 (hereinafter also called “patient remote 130”), for example a smartphone with wireless transceivers 132, 135, 136 respectively for WPAN (e.g. BLE), LPWAN, cellular (e.g., 4G / LTE / 5G) and WLAN communication. If a smartphone is used, this is a smartphone that is possessed, e.g., owned, by the patient in which the plate 60, rod 80 or other implant with bone screw, nail or pin format sensor device 1 is implanted and on which a software application ('app') is installed. The app is then a so-called Software as a Medical Device (SaMD) which is defined by the United States Food and Drug Administration (FDA) as software intended to be used for one or more medical purposes that perform these purposes without being part of a hardware medical device.

[0060] The cellular transceiver 135 and WLAN transceiver 136 provide two different data communication paths for the patient remote 130 to upload clinical data from the sensor device 1 via an internet connection 150 to a remotely located data centre 160 (hereinafter also called “backend 160”) acting as repository for storage of clinical data and / or as a host for the services. The remote's WLAN transceiver 136 can upload data to the backend 160 via a router 138 and a telephone line 140 (or telephone network 140) using a wired internet connection 150. The internet connection 150 may provide access to one or more distributed networks and / or cloud services. The remote's cellular transceiver 135 can upload data to the backend 160 via one or more cellular network base stations 142 (cellular towers), for example LPWAN-capable cellular network base station. In some cases, instead of a public communication network, a dedicated point-to-point transmission, e.g., via a dedicated telephone line, may be provided for uploading clinical data. In all these scenarios, uploading of clinical data from the sensor device 1 to the backend 160 takes place via the intermediary of the patient remote 130, the latter thereby acting as a relay device.

[0061] Health care staff, such as health care professionals (HCPs), clinical specialists and representatives and remote care team members have access to the backend 160 via suitable portals 170 with the aid of a software application running on the backend 160 and / or the portal 170 to provide the necessary user interfacing, diagnostics and so forth. At least one portal 170 is provided by at least one workstation for health care staff to access a data centre, e.g., the backend 160. Analysis and diagnostic software may also be run at the backend 160 to analyse clinical data from individual patients or groups of patients.

[0062] It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present disclosure. REFERENCE NUMERALS 1 sensor device in format of a bone screw, nail or pin 5 ball seal 10 head 11 head, driver engaging surfaces, e.g. spanner flats, hex driver flats 12 head, aperture for passage of ball seal 14 shaft 15 antenna 16 antenna connection conductor, e.g. solid copper 17 antenna connection insulator, e.g. polyethylene 18 antenna connection conductive shield, e.g. copper braid, mesh or tube 20 cover 21 cover threaded sleeve (male thread) 22 cover, hollow conical taper for accommodating ball bearing 23 cover, distal extension 25 rigid element for force transmission, e.g., ball bearing 26 waist or bellows 27 helical compression spring 28 internal chamber for helical compression spring 29 point of conical taper / / distal end of cover 20 30 bobbin (or spool) 31 bobbin spindle 32 bobbin proximal flange 34 bobbin proximal flange, aperture for locating ball seal 36 bobbin distal flange 40 sensor housing 42 sensor housing base 44 sensor housing, sidewall 45 sensor element, e.g., strain gauge 46 wireless transmitter or transceiver 47 memory 48 processor 49 electrical connector 50 battery cell, cylindrical 52 battery cell compartment 54 battery cell compartment housing 60 bone or implant plate 61 bone screw receiving bore in implant plate 62 female threaded length portion of bore 63 force transmitting length portion of bore 70 adapter, e.g., intermedullary nail 71 bone screw receiving bore in adapter 72 female threaded length portion of bore 73 unthreaded length portion of bore 74 rod receiving passageway in adapter 75 grub screws for adapter 76 threaded bores for receiving grub screws 78 adapter slot pair 80 implant rod or locking screw for intermedullary nail 100 Medical Device Communication System (MDCS) 123 charger 124 charger energy source 129 charger external mains power connection 130 patient remote controller (patient remote), e.g., smartphone or tablet device 132 smartphone wireless personal area network (WPAN) transceiver 135 smartphone cellular transceiver (LTE) 136 smartphone wireless local area network (WLAN) transceiver 138 router 140 telephone line / telephone network 142 cellular network base station (cellular tower) 150 internet connection 160 remotely located data centre (backend) 170 portal

Claims

1. A sensor device formatted as a screw, nail or pin, the sensor device comprising:a head;a shaft extending in a distal direction from the head;at least one battery cell accommodated in the head or shaft;a sensor housing arranged beyond the battery cell in the distal direction, the sensor housing accommodating a sensor element;a wireless transmitter;an antenna formed integrally in the head for wireless communication of data signals from the wireless transmitter; anda conductor extending between the antenna and at least one of the wireless transmitter and the sensor element for wired communication of data signals between the wireless transmitter and the antenna and / or wired transmission of electrical power from the antenna to at least one of the wireless transmitter and the sensor element.

2. The sensor device of claim 1, wherein the battery cell is accommodated in the shaft and the sensor device further comprises a bobbin to which the or each battery cell is mounted, the bobbin having a spindle through which the conductor is routed.

3. The sensor device of claim 2, wherein the bobbin comprises a distal flange with a proximal surface facing the or each battery cell and a distal surface facing the sensor housing.

4. The sensor device of claim 2 or 3, wherein the bobbin comprises a proximal flange with a distal surface facing the or each battery cell and a proximal surface facing the head.

5. The sensor device of claim 4, wherein the proximal flange includes at least one sealed aperture, which, before it is sealed during assembly, allows the or each battery cell to be filled with liquid electrolyte.

6. The sensor device of any one of claims 2 to 5, wherein the at least one battery cell includes a cylindrical cell with electrodes and separators that are wound onto the spindle.

7. The sensor device of any one of the preceding claims, wherein the head is shaped to provide a male or female screw drive having respectively an external or internal polygonal shape, thereby allowing a matched driver to apply torque to the screw, nail or pin format sensor device about the shaft.

8. A sensor device formatted as a screw, nail or pin, the sensor device comprising:a head;a shaft extending in a distal direction from the head;at least one battery cell accommodated in the head or shaft;a sensor element;an antenna for wireless communication of data signals; anda wireless transmitter connected to the antenna for wired communication of data signals between the wireless transmitter and the antenna, andwherein the antenna is formed integrally in the head,wherein the head is shaped to provide a male or female screw drive having respectively an external or internal polygonal shape, thereby allowing a matched driver to apply torque to the screw, nail or pin format sensor device about the shaft.

9. The sensor device of claim 8, further comprising a conductor extending to connect the wireless transmitter to the antenna.

10. The sensor device of any one of the preceding claims, wherein the sensor element is a strain gauge arranged in the sensor housing so as to deform under action of strain acting on the sensor housing.

11. The sensor device of claim 10, wherein the shaft has a tapered portion extending distal the sensor housing to form a hollow space between the sensor housing and the distal end of the shaft, the sensor device further comprising a rigid element that is arranged in the hollow space, so as to transmit force bearing on the distal end of the shaft onto the sensor housing and thereby onto the strain gauge.

12. A sensor device formatted as a screw, nail or pin, the sensor device comprising: a head;a shaft extending in a distal direction from the head;at least one battery cell accommodated in the head or shaft;a sensor housing accommodating a sensor element, the sensor element being a strain gauge arranged in the sensor housing so as to deform under action of strain acting on the sensor housing;an antenna for wireless communication of data signals formed integrally in the head; anda wireless transmitter connected to the antenna for wired communication of data signals between the wireless transmitter and the antenna,wherein the shaft has a tapered portion extending distal the sensor housing to form a hollow space between the sensor housing and the distal end of the shaft, the sensor device further comprising a rigid element that is arranged in the hollow space, so as to transmit force bearing on the distal end of the shaft onto the sensor housing and thereby onto the strain gauge.

13. The sensor device of claim 12, further comprising a conductor extending to connect the wireless transmitter to the antenna.

14. The sensor device of any one of any one of the preceding claims, wherein the sensor housing is formed integrally with the shaft.

15. The sensor device of any one of the preceding claims, wherein the shaft further comprises an extension portion extending distal to the sensor housing to provide the shaft with additional length.

16. The sensor device of claim 15, further comprising a spring arranged in compression in a chamber within the extension portion.

17. The sensor device of any one of the preceding claims, further comprising a male thread extending along a length portion of the shaft.

18. The sensor device of claim 17, wherein the male thread is formed integrally with the shaft.

19. The sensor device of claim 17, wherein the male thread is formed as a sleeve that is fitted over and secured to the shaft.

20. A kit of parts comprising:a sensor device according to any one of claims 17 to 19; anda plate having a bore formed therein, the bore having a threaded length portion with a female thread complementary to the male thread of the sensor device, so that sensor device can be screw fastened with its male thread into the plate.

21. The kit of claim 20, wherein the bore has a further length portion shaped and dimensioned such that, when a sensor device is screw fastened in the plate, the sensor housing is in force transmitting engagement with the further length portion of the bore so that distortion of the plate causes deformation of the strain gauge.

22. The kit of claim 20, wherein the bore is a blind bore terminating in an end surface, the bore being shaped and dimensioned such that, when a sensor device is screw fastened into the plate, the sensor housing is in force transmitting engagement with the end surface of the blind bore so that distortion of the plate causes deformation of the strain gauge.

23. A kit of parts comprising:a sensor device according to any one of claims 17 to 19; andan adapter, the adapter comprising:a passageway enabling the adapter to receive a length portion of a rod; anda female thread defining a thread axis, the female thread being complementary to the male thread of the sensor device, so that a sensor device can be screw fastened to the adapter.

24. The kit of claim 23, wherein the passageway extends transverse to the thread axis.5 25. The kit of claim 24, wherein the thread axis extends so as to be offset from a rodreceived in the passageway.

26. The kit of claim 24, wherein the thread axis extends so as to intersect a rod received in the passageway.

27. The kit of claim 23, wherein the female thread of the adapter is arranged relative to the io passageway such that a sensor device can be screwed into the female thread to clamp a rod that is in the passageway to the adapter.

28. The kit of claim 27, wherein, when a sensor device is screwed into the female thread of the adapter so as to clamp a rod to the adapter, the sensor housing base is in force transmitting engagement with the rod.15

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