WO2020037380A1

WO2020037380A1 - A surgical device

Info

Publication number: WO2020037380A1
Application number: PCT/AU2019/050902
Authority: WO
Inventors: Michael Mcauliffe; Martin MCBAIN
Original assignee: Q L Spacer Blocks Pty Ltd
Priority date: 2018-08-24
Filing date: 2019-08-26
Publication date: 2020-02-27

Abstract

Provided herein is a sensor device for assisting a surgeon during joint surgery on a patient, the sensor device having a trial implant with an articulating surface and a contact surface for contacting one or more resected surfaces of a bone and a sensor at least partly disposed over the contact surface of the trial implant and configured to measure one or more forces applied to the contact surface of the trial implant by the one or more resected surfaces of the bone. A spacer device that includes a spacer body having one or more contact surfaces for contacting respective one or more resected surfaces of a bone and a sensor at least partly disposed over the one or more contact surfaces of the spacer body is also provided. Systems and methods utilising said sensor device and spacer device are further described herein.

Description

TITLE

A SURGICAL DEVICE FIELD

THIS INVENTION relates to a device for use in surgery. In particular, the invention is directed to a sensor device or a spacer device for use in joint surgery on a subject and, in particular, knee surgery, that facilitates monitoring or assessment of a force between an implant and an underlying cut surface of a bone. Such devices allow for the detection of underlying defects or deficits in the cut surface of the bone as well as facilitates optimal soft tissue balancing of the associated joint.

BACKGROUND

Aseptic loosening represents a significant cause of tibial tray failure. Aseptic loosening is generally recognised as the failure of the bond between an implant and bone in the absence of infection. As pain and disability due to loosening become severe enough to require revision arthroplasty, abnormalities in the binding of the cement to the bone or prosthesis are almost always visible radiographically. Radiolucent lines (RLLs) are defined as radiolucent intervals (measured in millimetres) between the cement and the bone or implant and bone. The appearance of peripheral RLLs under the tibial component is a frequent occurrence in the immediate postoperative phase.

By way of example, a proximal tibial cut during knee replacement surgery is typically performed using a cutting block, inclusive of patient specific cutting blocks. It is possible that the angle of the cutting block isn’t perfectly perpendicular to the three- dimensional plane of mechanical/anatomic alignment of the knee joint and the requisite implant. Although the saw blade is inserted through the block, it is possible that the cut is not made completely flat across the plane. There exists the likelihood that cut lines and marks can remain on the surface of the cut. These imperfections in the cut surface of the tibia may subsequently fill with cement during attachment of the tibial tray thereto. Radiolucent lines between the cement and the cut surface of the proximal tibia that are visible post operatively represent potential contributing factors for subsequent implant failure and can be associated with poor impaction and ingress of cement to the underlying bone.

Such imperfections in the cut surface of a bone may not be noticeable by sight, but can still be significant enough to cause pressure variations over the base of the tibial plate even though it is seated firmly over the tibial cut. The current method is to physically feel the fit of the trial implant and inspect around the edges for gaps. Gap and pressure readings are currently taken from the distal side of the femoral component and proximal side of the tibial component. Such measurements, however, assume that the cuts are congruent with the prosthesis or implant and therefore that forces are transferred in the same proportions to the underlying bone.

Accordingly, there remains a need for an improved device and method for assessing the cut surface of a bone, such as the tibia and femur, to identify imperfections or defects therein prior to engagement of an implant thereto.

SUMMARY

The present invention is broadly directed to a sensor device and a spacer device for assisting a surgeon during surgery and, more particularly, knee surgery (e.g., total knee replacement), in a patient. In this regard, the sensor device and/or the spacer device can be used to assess the pressure exerted upon one or more resected surfaces of a bone that abut or contact respective contact surfaces of a trial implant, such as femoral, patellar and tibial trial implants, across the range of movement of an associated joint. This may facilitate appropriate revision of the one or more surface cuts or resections by a surgeon as well as allow for suitable tensioning of the soft tissue envelope of the associated joint. The invention is further directed to a surgical system including said devices and methods of using the devices in knee surgery.

In a first aspect, the invention is directed to a sensor device for assisting a surgeon during joint surgery on a patient comprising:

a trial implant having an articulating surface and a contact surface for contacting one or more resected surfaces of a bone; and

a sensor at least partly disposed over the contact surface of the trial implant and configured to measure one or more forces applied to the contact surface of the trial implant by the one or more resected surfaces of the bone.

In one embodiment, the sensor is configured to measure the one or more forces so as to define a surface map relating to force measurements received thereby.

In certain embodiments, the sensor is reversibly engaged to the contact surface of the trial implant. In alternative embodiments, the sensor is integral with or adhered to the contact surface of the trial implant.

In a second aspect, the invention is directed to a spacer device for assisting a surgeon during knee surgery on a patient comprising: a spacer body having one or more contact surfaces for contacting respective one or more resected surfaces of a bone;

a sensor at least partly disposed over the one or more contact surfaces of the spacer body and configured to measure one or more forces applied to the one or more contact surfaces of the spacer body by the one or more resected surfaces of the bone.

In one embodiment, the spacer body comprises one or more U-shaped support portions that define first and/or second contact surfaces.

Suitably, the first and/or second contact surfaces are to be positioned adjacent a resected distal femoral surface, a posterior femoral surface and/or a resected proximal tibial surface.

In another embodiment, the spacer body comprises:

a housing that includes a lateral member having an outer surface that defines a first contact surface and an inner surface and a pair of side members that comprise respective, internal, opposed side walls;

a support portion having a first end portion and a second end portion, the second end portion capable of being initially disposed between the side walls of the housing and the first end portion including a first pair of lateral projections, the first end portion optionally defining a second contact surface; and

wherein the support portion is adapted for axial slidable movement relative to the housing so as to define a first space and a second space between the first pair of lateral projections and respective side members for receiving one or more spacer elements therein.

Suitably, the outer surface of the lateral member and/or the first end of the support portion are to be positioned adjacent a resected distal femoral surface, a posterior femoral surface and/or a resected proximal tibial surface. Accordingly, in particular embodiments, the sensor comprises a first sensor at least partly disposed over the first contact surface of the lateral member and/or a second sensor at least partly disposed over the second contact surface of the first end portion of the support portion.

Suitably, the housing comprises first and second portions that allow for axial and/or sagittal movement of the first portion relative to the second portion. Preferably, the first and second portions are slidably connected to each other.

In a third aspect, the invention provides a system for assisting a surgeon during joint surgery on a patient comprising:

a sensor device of the first aspect or a spacer device of the second aspect; and a processor operably connected to the sensor device or the spacer device and configured to process the one or more forces measured by the sensor.

In one embodiment, the processor is adapted to generate a surface map relating to the one or more forces measured by the sensor.

In particular embodiments, the system further includes a display operably connected to the processor and configured to display the one or more forces measured by the sensor. More preferably, the display is configured to display the surface map generated by the processor.

In certain embodiments, the system further includes a projector for projecting the surface map onto the one or more resected surfaces of the bone.

In a fourth aspect, the invention provides a method for assisting a surgeon during joint surgery on a patient including the steps of:

(a) positioning a sensor device of the first aspect or a spacer device of the second aspect adjacent one or more resected surfaces of a bone of the joint of the patient; and

(b) measuring one or more forces exerted by the one or more resected surfaces of the bone on a contact surface of the trial implant or the spacer device by the sensor.

In one embodiment, the method of the present aspect further includes the step of generating by a processor a surface map relating to the one or more forces measured by the sensor.

In some embodiments, the present method further includes the step of detecting one or more defects or deficits in the one or more resected surfaces of the bone.

Suitably, the present method further includes the step of displaying on a display the one or more forces measured by the sensor. More preferably, the displaying step includes displaying the surface map generated by the processor.

In particular embodiments, the present method further includes the step of projecting the surface map onto the one or more resected surfaces of the bone.

In some embodiments, the step of measuring the one or more forces exerted on the contact surface of the trial implant or the spacer device is performed when the joint is in extension. In other embodiments, the step of measuring the one or more forces exerted on the contact surface of the trial implant or the spacer device is performed when the joint is in flexion. Preferably, the step of measuring the one or more forces exerted on the contact surface of the trial implant or the spacer device is performed substantially throughout the range of motion of the joint.

Suitably, the method of the present aspect further includes the step of using the force measured to determine a course of action associated with joint surgery on the patient. Preferably, the course of action includes further resection of one or more of the resected surfaces of the bone. In particular embodiments, this includes further resection of the resected distal femoral surface, the resected posterior femoral surface, the resected anterior femoral surface, the resected proximal tibial surface and/or the resected posterior patellar surface. More preferably, further resection is the course of action when:

(a) the force measured across the one or more resected surfaces of the bone is not substantially equal;

(b) the force measured indicates one or more defects or deficits in the one or more resected surfaces of the bone.

Referring to the aforementioned aspects, the joint is suitably a knee joint. As such, the trial implant may be or comprise a trial femoral implant, a trial tibial implant, and/or a trial patella implant. Accordingly, and referring to the method of the fourth aspect, the step of positioning the sensor device or spacer device may comprise positioning the sensor device or spacer device adjacent a resected femur, a resected tibia and/or a resected patella.

With respect to the above aspects, the one or more resected surfaces, such as a first resected surface, suitably comprise a resected femoral surface, such as a resected distal femoral surface, a resected anterior femoral surface, a resected posterior femoral surface and any combination thereof. In other embodiments, the one or more resected surfaces, such as a second resected surface, additionally or alternatively comprise a resected tibial surface, such as a resected proximal tibial surface. In further embodiments, the one or more resected surfaces comprise a resected posterior patellar surface.

Suitably, the sensor, including first and second sensors, of the aforementioned aspects is selected from the group consisting of a sensor film (such as a thin sensor film or a thick sensor film), an electromechanical sensor (such as a strain gauge sensor), a piezoelectric sensor, a capacitive sensor and any combination thereof. In one particular embodiment, the sensor is or comprises a sensor film, which may comprise a plurality of force sensor elements.

It will be appreciated that the indefinite articles“a” and“an” are not to be read as singular indefinite articles or as otherwise excluding more than one or more than a single subject to which the indefinite article refers. As used herein, unless the context requires otherwise, the words“comprise”, “comprises” and“comprising” will be understood to mean the inclusion of a stated integer or group of integers but not the exclusion of any other non- stated integer or group of integers.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention may be readily understood and put into practical effect, reference will now be made to the accompanying illustrations, wherein like reference numerals are used to refer to like elements.

Figure 1: is a perspective view of an embodiment of a sensor device for application to a resected femur.

Figure 2: is a perspective view of a further embodiment of a sensor device for application to a resected tibia.

Figure 3: is a perspective view of the sensor devices of Figures 1 and 2 being applied to a knee joint.

Figure 4 is a side on perspective and cross-sectional view of a further embodiment of a sensor device for application to a resected patella.

Figure 5: is a schematic diagram of an embodiment of a surgical system that incorporates the sensor devices of Figures 1, 2 and 4.

Figure 6 is a perspective view of an embodiment of a spacer device for application to a resected knee joint.

Figure 7 is a perspective view of a further embodiment of a spacer device for application to a resected knee joint.

Figure 8 is an exploded view of the spacer device of Figure 7.

DETAIFED DESCRIPTION

The present invention relates to a device, such as a sensor device or spacer device for use during joint surgery and, in particular, knee surgery (e.g., TKR/TKA), for determining or detecting imperfections, defects or deficits in one or more cut surfaces of a bone. Additionally or alternatively, the device can assist in determining an appropriate soft tissue balance of the joint in question in extension and/or flexion. While the device described herein is particularly suited for use in TKR/TKA, the present invention has general applicability to all types of joints (e.g., elbows, shoulders, wrists and fingers) and replacement surgery thereof that requires accurate and substantially level (i.e., flat and even) cut surfaces prior to the engagement of an implant thereto.

Appropriate resection of the bones of the knee (i.e., proximal tibia and distal femur) requires that the resultant cut surfaces of these bones be substantially flat (i.e., include substantially no defects, deficits or imperfections in the cut surface) as well as appropriately level with a desired alignment of the cut or resection as determined by a surgeon (e.g., substantially perpendicular to the mechanical and/or anatomical axis of the knee joint).

In addition to the above, it is preferable that the soft tissues surrounding and/or interconnecting the bones of the knee at an approximately equal or similar tension relative to one another when the femur and its corresponding tibia are appropriately aligned. Preferably, this tension is approximately equal or similar to the physiological tension of these soft tissues in the native knee at rest. Non-limiting examples of the soft tissues surrounding and/or interconnecting the bones of the knee include the medial and lateral collateral ligaments, the anterior and posterior cruciate ligaments, the posteromedial and posterolateral ligamentous structures and the posterior capsule.

While the principles described herein are based on methods of providing surgical devices for humans, this invention may also be extended to other mammals such as livestock (e.g. cattle, sheep), performance animals (e.g. racehorses) and domestic pets (e.g. dogs, cats), although without limitation thereto.

Referring to Figures 1 and 3, a first sensor device 100 according to particular embodiments is provided. To this end, the first sensor device 100 is configured to be used during total knee arthroplasty (TKA) and is adapted for engaging a femur 800 of a knee joint 700. In this regard, the first sensor device 100 broadly includes a trial femoral component or implant 110 which is of appropriate dimensions to engage or contact one or more cut or resected surfaces of a distal femur 801.

In the embodiment provided, the trial femoral implant 110 is a unitary, one- piece article preferably made of a surgical grade material, plastic, metal or metal alloy such as a cobalt-chromium-molybdenum alloy, titanium, a titanium alloy or the like as are known in the art, that is capable of withstanding the forces applied by the femur and/or tibia thereon, while also preferably being biocompatible and resistant to corrosion.

The trial femoral implant 110 has a substantially U-shaped configuration and broadly includes spaced apart lateral and medial condyle portions 111,112, which are adapted for mutual articulation with a spaced pair of condyle bearing portions 2l3a-b of a trial tibial component 210 during extension and flexion of the knee joint 700. In addition to its condyle portions 111,112, the trial femoral implant 110 includes an anterior plate portion 115, which together define an outer curved articulating surface 116 of the trial femoral implant 110.

The condyle portions 111,112 and the anterior plate portion 115 additionally form or define an inner channel 113 that further defines an inner contact surface 114. In this manner, the inner contact surface 114 is adapted to reciprocally abut or contact a resected distal femoral surface 802, a resected anterior femoral surface 803 and a resected posterior femoral surface 804 of a distal femur 801. Disposed within the inner channel 113 and extending upwardly therein from the inner contact surface 114 of the respective condyle portions 111,112 are a pair of fixation pegs or elements 117,118. As shown in Figure 3, the fixation elements 117,118 are adapted for placement within pre drilled holes 805a-b in the resected distal femoral surface 802.

As illustrated in Figure 1, the sensor device 100 further includes an electronic force sensor comprising a first sensor film 120 reversibly engaged to the contact surface 114 of the trial femoral implant 110. In this manner, the first sensor film 120 can be formed into the shape of at least a portion of the contact surface 114 of the trial femoral implant 110 and may be suitable for use across a range of trial femoral implants 110 of differing sizes as required. It will be appreciated that in alternative embodiments, the first sensor film 120 can be integral with or adhered to the contact surface 114 of the trial femoral implant 110. As such, each trial femoral implant 110 comprises its own sensor film 120 associated therewith.

The first sensor film 120 includes a plurality or array of force sensor elements 121 evenly distributed throughout. By virtue of this arrangement, the force sensor elements 121 of the first sensor film 120 are configured (e.g., of sufficient number, concentration and sensitivity) to measure a plurality of forces applied by the resected distal femoral surface 802, the resected anterior femoral surface 803 and the resected posterior femoral surface 804 of a distal femur 801 to the contact surface 114 of the trial femoral implant 110. In alternative embodiments, the first sensor film 120 may be disposed only over a portion of the contact surface 114 of the trial femoral implant 110 so as to underlie and abut only a portion of the cut surfaces of the distal femur 801, such as one of the resected distal femoral surface 802, the resected anterior femoral surface 803 and the resected posterior femoral surface 804. Preferably, the first sensor film 120 is adapted to measure a plurality of forces across one or more of the cut surfaces 802- 804 of the femur 800 that are capable of being utilised to define a surface or pressure map 300 relating to force measurements received from the plurality of pressure sensor elements 121 and their spatial distribution across the resected femoral surfaces 802- 804.

Referring to Figure 2, a further embodiment of a second sensor device 200 is provided. The second sensor device 200 includes the trial tibial implant 210 having a plastic ( e.g ., ultra-high molecular weight polyethylene) insert 211 held by and secured by known means to a metallic tibial tray 212. The plastic insert 211 includes the condyle bearing portions 2l3a-b described previously that define a further articulating surface 218. The tibial tray 212 comprises a base 214 having opposed upper and lower surfaces 215,216. Extending distally from the lower surface 216 of the base 214 is a stem 217 having a cylindrical cross-sectional shape and support elements 218 extending therefrom. The upper surface 215 of the base 214 has a recess for supporting the plastic insert 211 therein. Suitably, the plastic insert 211 and the tibial tray 212 are made of a surgical grade material, such as those hereinbefore described, or as are known in the art.

Similar to the first sensor device 100, the second sensor device 200 includes a second sensor film 220 of a substantially planar shape that is reversibly engaged to the lower surface 216 of the trial tibial implant 210 and extending substantially thereover. In this manner, the second sensor film 220 can be formed into the shape of at least a portion of the lower surface 216 of the trial tibial implant 210 and may be suitable for use across a range of trial tibial implants 210 of differing sizes as required. In alternative embodiments, the second sensor film 220 can be integral with or adhered to the lower surface 216 of the trial tibial implant 210. As such, each trial tibial implant 210 may comprise its own sensor film 220.

Like the first sensor film 120, the second sensor film 220 contains an array of force sensor elements 221 arranged so as to measure a plurality of forces applied to the lower surface 216 of the base 214 by the resected proximal tibial surface 902. Again, the second sensor film 220 is preferably designed to measure a plurality of forces across the resected surface 902 of the proximal tibia 901 so as to generate force data 350 that can be utilised to define a surface map 300 of the resected tibial surface 902 relating to force measurements received therefrom by the force sensor elements 221 and their spatial distribution thereacross. Figure 4 provides an embodiment of a third sensor device 600. The third sensor device 600 includes a trial patellar implant 610 made of a surgically acceptable material or plastic (e.g. ultra-high molecular weight polyethylene) for engagement to a patella 750. The trial patellar implant 610 comprises a substantially dome shaped outer articulating surface 614 configured for slidingly abutting the condylar surface and trochlear groove of the knee joint 700 during movement thereof. Opposed to the articulating surface 614, is a planar inner contact surface 616 for abutting a resected posterior surface 751 of the patella 750. The inner contact surface 616 is also provided with three serially spaced studs 6l8a-c for anchoring the third sensor device 600 in the patella 750 during use.

Similar to the first and second sensor devices 100,200, the third sensor device 600 includes a third sensor film 620 of a substantially planar shape that is reversibly engaged to the inner contact surface 616 of the trial patellar implant 610 and extending substantially thereover. In this manner, the third sensor film 620 can be formed into the shape of at least a portion of the inner contact surface 616 of the trial patellar implant 610 and may be suitable for use across a range of trial patellar implants 610 of differing sizes as required. In alternative embodiments, the third sensor film 620 can be integral with or irreversibly adhered to the inner contact surface 616 of the trial patellar implant 610.

Like the first and second sensor films 120,220, the third sensor film 620 suitably contains an array of force sensor elements 621 arranged so as to measure a plurality of forces applied to the inner contact surface 616 of the trial patellar implant 610 by the resected posterior surface 751 of the patella 750. Again, the third sensor film 620 is preferably designed to measure a plurality of forces across the resected posterior surface 751 of the patella 750 so as to generate force data 350 that can be utilised to define a surface map 300 relating to force measurements and their spatial distribution received from the force sensor elements 621.

It will be appreciated that the femoral, tibial and patellar trial implants 110,210,610 of the first, second and third sensor devices 100,200,600 can vary between different knee surgical systems as are known in the art. Indeed, it is envisaged that the present invention can include or utilise any trial implant known in the art. Additionally, it is envisaged that a surgeon may only use one particular sensor device at a specific time or, as described herein, two or more sensor devices (e.g., the first, second and third sensor device 100,200,600) may be implemented simultaneously within a single joint. An embodiment of a spacer device 500 is provided in Figure 6. The skilled artisan will appreciate that the spacer device 500 is an embodiment of a dogbone-type spacer device for assisting a surgeon during knee replacement surgery.

As shown in Figure 6, the spacer device 500 includes respective first and second U-shaped support portions 510,520 of suitable dimensions to cover and contact at least in part resected surfaces of a distal femur 800 and/or a proximal tibia 900 when temporarily inserted therebetween. The support portions 510,520 are positioned at opposing first and second ends 501,502 of an elongate shaft or handle 505 and extending outwardly or axially therefrom. In the embodiment provided, the second support portion 520 is of a lesser height than the first support portion 510, and in doing so being flush with the height of the handle 505. This arrangement allows for the assessment during knee surgery of extension and/or flexion gaps across a range of dimensions with the use of a single spacer device 500. It will be appreciated, however, that in alternative embodiments the spacer device 500 may simply include a single support portion disposed at one end of the handle 505.

Each of the support portions 510,520 have an upper surface 515,525 and a lower surface 516,526. In the embodiment provided, both the upper and lower surfaces 515,516,525,526 are substantially flattened and planar to define a pair of condyle support platforms 517,527. As shown in Figure 6, each of the upper and lower surfaces 515,516,525,526 further comprise a sensor film 530a-d of a substantially flattened or planar shape that extends substantially thereover and is substantially adhered to or is integral with the support portions 510,520.

In alternative embodiments, it is envisaged that the sensor film 530 of the upper and lower surfaces 515,516,525,526 can be reversibly engaged therewith so as to be readily switchable between the respective support portions 510,520 and/or the upper and lower surfaces thereof 515,516,525,526. To this end, the spacer device 500 may include a single sensor film 530 that is interchangeable between each of the upper and lower surfaces 515,516,525,526 of the support portions 510,520.

Suitably, the sensor film 530a-d contains an array of force sensor elements 531 arranged in a manner so as to measure a plurality of forces applied to the upper and lower surfaces 515,516,525,526 of the support portions 510,520 by a resected surface 802-804 of a distal femur 801 or a resected surface 902 of a proximal tibia 901. Additionally, the first sensor film 530a-d is preferably designed to measure a plurality of forces across the resected surfaces of the distal femur 800 and/or the proximal tibia so as to generate force data 350 that can be utilised to define a surface map 300 of a cut surface by way of the force measurements received from the force sensor elements 531. To this end, the upper and lower surfaces 515,516,525,526 of the support portions 510,520 are of suitable dimensions to abut or receive a resected distal femoral surface and/or a resected proximal tibial surface, so as to receive a force applied thereto by said resected surfaces and determine a surface or pressure map 350 based on the spatial distribution of the force sensor elements 531 and the force applied thereto.

In alternative embodiments, the lower surfaces 516,526 may be configured to reciprocally abut or engage an underlying tibial tray (not shown), such as by way of a locking component. In this exemplary embodiment, the lower surface 516,526 suitably does not include a sensor film 530 disposed thereon or integrated therewith. In another alternative embodiment, the upper surface 515,525 of each of the condyle support platforms 517,527 defines a shallow concavity for receiving a femoral component or implant, inclusive of trial femoral components or implants, thereon. In this exemplary embodiment, the upper surface 515,525 suitably does not include a sensor film 530 disposed thereon or integrated therewith. In such alternative embodiments, it will be appreciated that the spacer device 500 is configured to only assess the resected surface of one of the distal femur 800 or proximal tibia 900 by way of the sensor film 530.

An alternative embodiment of a spacer device 1000 is provided in Figures 7 and 8. Similar to that for the spacer device 500 previously described, the spacer device 1000 is for assisting a surgeon during knee replacement surgery, which includes a T-shaped open-sided housing 1010 that defines a longitudinal axis and an inner support portion 1020. The inner support portion 1020 has a first end portion 1021 and a second end portion 1022 connected by a central portion 1023. The housing 1010 includes a central axial projection l0l7a-b that extends axially and distally from a substantially planar upper wall lOl la-b thereof and is disposed within an open-sided central channel 1028 at a second end 1022 of the inner support portion 1020 so as to be configured to allow for axial slidable movement thereof relative to the inner support portion 1020. Each portion of the central axial projection l0l7a-b comprises a curved shoulder portion that curves downwardly and outwardly from the planar upper wall lOl la-b to a distal free end thereof.

As shown in Figures 7 and 8, the housing 1010 is composed of approximately equally dimensioned first and second portions lOlOa-b that are reversibly engaged or abut together at an inner or central portion or surface of their respective portions of the central axial projection l0l7a-b. It will be understood that other means of reversibly engaging the first and second portions lOlOa-b, as are known in the art, are contemplated for the present embodiment, such as by a mortise and tenon joint as described in PCT/AU2018/050209, which is incorporated by reference herein.

The upper wall 101 la-b of the housing 1010 has first and second upper surfaces 101 la’, 101 lb’, which together define an upper contact surface, and corresponding first and second lower surfaces (not shown).

Similar to the aforementioned sensor devices 100,200,600, the spacer device 1000 includes first and second sensor films l030a-b of a substantially planar shape that is integral with or adhered to their respective upper wall 101 la-b of the housing 1010 and extending substantially thereover. In this manner, the first and/or second sensor films l030a-b can be formed into the shape of at least a portion of the upper wall 101 la- b of the housing 1010. In alternative embodiments, the first and/or second sensor films l030a-b can be reversibly engaged with the upper wall 101 la-b of the housing 1010. As such, a single sensor film l030a-b may used across a number of difference spacer devices 1000.

The first and second sensor films l030a-b contain an array of force sensor elements 1031 arranged so as to measure a plurality of forces applied to the upper wall 101 la-b of the housing 1010 by the resected distal femoral surface 902. Additionally, the first and second sensor films l030a-b are preferably designed to measure a plurality of forces across the resected surface 802 of the distal femur 801 so as to generate force data 350 that based on its spatial distribution thereover can be utilised to define a surface map 300 relating to force measurements received from the force sensor elements 1031. To this end, the upper surfaces 101 la’, 101 lb’ of the housing 1010 are of suitable dimensions to abut or receive a resected distal femoral surface 802 so as to receive a force applied thereto by said resected distal femoral surface 802 and together with the first and second sensor films l030a-b disposed thereon and utilised to generate a surface map 300 based on the force applied thereto.

The housing 1010 further comprises a pair of directly opposed side walls l0l2a- b. Each of the side walls l0l2a-b extends axially and distally from a respective end portion of the upper wall 101 la-b so as to form a pair of channels l0l4a-b in which to receive the inner support portion 1020. The side walls l0l2a-b further include a respective inwardly projecting tab l0l3a-b at a distal end thereof that assist in maintaining the inner support portion 1020 disposed within the housing 1010. In this manner, each of the first and second portions lOlOa-b are essentially mirror images of each other and include a respective portion of the upper wall 101 la- b, one of the side walls l0l2a-b and a portion of the central axial projection l0l7a-b. By virtue of this arrangement, the first and second portions lOlOa-b of the housing 1010 are configured to allow for independent axial and/or sagittal distraction or movement of the first portion lOlOa relative to the second portion lOlOb so as to allow for the generation of a lateral inner space l060a and a medial inner space l060b. To this end, one or more spacer elements 1500 could be inserted into the lateral and medial inner spaces l060a-b so as to maintain the spacer device 1000 in the distracted position.

As each of the first and second portions lOlOa-b are distracted relative to the other, stability of the housing 1010 is maintained, at least in part, by the first and second portions lOlOa-b abutting each other. This is further assisted by the central axial projection l0l7a-b abutting respective side walls of the central channel 1028. Rather than simply contacting or abutting, it will be appreciated that the central axial projection l0l7a-b may alternatively be slidably engaged with the respective side walls of the central channel 1028.

As illustrated in Figures 7 and 8, the second end portion 1022 and the central portion 1023 are, at least partially, disposed between the side walls l0l2a-b of the housing 1010 and are maintained in this position by virtue of the second end portion 1022 having a second pair of radially extending tabs l025a-b, which may contact their respective and opposing inwardly projecting tab l0l3a-b of the housing 1010 upon distraction of the spacer device 1000 (i.e., axial movement of the inner support portion 1020 relative to the housing 1010). The first end portion 1021 of the inner support portion 1020 also includes a first pair of radially extending tabs l024a-b. As can be observed from Figure 7, the first pair of radially extending tabs l024a-b are slightly longer in dimension than the second pair of radially extending tabs l025a-b. To this end, the first pair of radially extending tabs l024a-b are configured to be positioned adjacent or abut the resected proximal tibial surface 902 when in use.

The first end 1021 of the inner support portion 1020 further includes a distal channel 1029. To this end, the height of the spacer device 1000 can be adjusted, such as by reversibly attaching or engaging a foot portion 1100 to the distal channel 1029 by way of a reciprocally dimensioned projection 1110 disposed and extending from an upper surface thereof. The foot portion 1100 has a similar horseshoe or U-shaped profile as the housing 1010 and the inner support portion 1020. As a result of this arrangement, the overall height of the spacer device 1000 can be approximated to accommodate the extension gap and/or flexion gap regardless of their dimensions and then this height can be fine tuned with spacer elements 1500 as required.

Additionally, it is envisaged that a lower surface of the foot portion 1100 and/or the inner support portion 1020 may further comprise a further sensor film (not shown), such as those previously described herein, disposed thereacross. In this regard, the further sensor film (not shown) is suitably configured to measure a plurality of forces across the resected surface 902 of the proximal tibia 901 when contacted therewith so as to generate force data 350 that can be utilised to define a surface map 300 to assist a surgeon in identifying any defects or deficits on the resected surface 902 of the proximal tibia 901.

Once appropriately positioned within the knee joint 700, the first and second portions lOlOa-b of the housing 1010 of the spacer device 1000 can now be extended or distracted along its longitudinal axis relative to the inner support portion 1020. As described previously, axial movement of the first and second portions lOlOa-b relative to the inner support portion 1020 results in the generation of the lateral and medial inner spaces l060a-b that may be suitable for receiving the appropriately dimensioned spacer element 1500 therein. By way of example, the embodiment provided in Figure 7 illustrates the spacer element 1500 inserted into the medial inner space l060b. In this regard, the spacer element 1500 maintains the spacer device 1000 in the desired distracted position and facilitates appropriate contact of the first, second and further sensor films l030a-b with the respective resected surfaces 802,902 of the distal femur 801 and proximal tibia 901 under conditions of normal or near-normal soft tissue tension as well as appropriate extension and/or flexion gaps.

The skilled person will appreciate that the distraction distance of the first and second portions lOlOa-b of the housing 1010 relative to the inner support portion 1020 may depend, for example, upon the patient and the operative context in question. By way of example, revision knee surgery requires an increased extension/flexion gap in comparison to that of primary knee arthroplasty. This variable degree of distraction of the first and second portions lOlOa-b can be achieved by the addition of one or more shims 1500 of variable size to increase the overall height or width of the spacer device 1000 to an appropriate dimension as required by the particular surgical context. As described herein, the extension/flexion gap determined by distraction of the spacer device 1000 suitably results in an appropriate soft tissue balance or ligament tensioning of the knee. Additionally, once a suitable extension/flexion gap has been achieved by the spacer device 1000, this can then be utilized, together with ligament tension/soft tissue balance readings to determine an appropriate implant size, such as the polyethylene insert of the tibial tray, for a subject’s knee.

In certain embodiments, the spacer device 1000 has a width dimension of about 50 mm to about 80 mm and a thickness or depth dimension of about 50 mm to about 80 mm. Therefore, the spacer device 100 may be at least as large as the leading edges of the resected femoral and tibial surfaces. For instance, the spacer device 1000 may be about 20 mm to about 50 mm in depth and width in order to substantially conform to the resected leading edges of the resected femoral and tibial surfaces. As will be readily understood by the skilled artisan, the dimensions for the spacer device 1000 described herein will depend to some degree on the size of the knee joint 700 to which the device 1000 is to be applied.

It is further envisaged that particular embodiments of the spacer device 1000 may be configured or of dimensions for use in unicompartmental knee replacement (i.e., on the lateral or medial side of the knee joint 700). Additionally, embodiments of the spacer device 1000 may be adapted for use in bicruciate retaining total knee replacement surgery. In such an embodiment, the spacer device 1000 would need a posterior channel adapted to receive the cruciate ligament that have been left in-situ therein and the medial and lateral sides of the spacer device 1000 would be connected by an anterior bridge. Alternatively, two separate spacer devices 1000 may be utilised in the medial and lateral sides of the knee joint 700.

It is envisaged that the sensor devices 100,200,600 and spacer devices 500,1000 may be constructed in a variety of different shapes and sizes, as are known in the art and available commercially. To this end, it will be appreciated that the dimensions of the spacer devices and sensor devices provided herein may change to suitably fit the end range anatomical dimensions associated with smaller and larger knees. As such, this may allow the sensor devices 100,200,600 and the spacer devices 500,1000 to be used for different patients and/or for different techniques; for example, according to an exemplary embodiment, there may be spacer device designs that are intended to be used for posterior stabilized total knee replacement, and spacer device designs that are intended to be used for cruciate retaining total knee replacement, or cruciate sacrificing knee replacement, or any other type of knee replacement, as desired.

Suitably, prior to insertion of the first, second and/or third sensor devices 100,200,600 and/or the spacer devices 500,1000 hereinbefore described, the knee joint 700 is exposed and the distal femur 801 and the proximal tibia 901 are resected to thereby establish an appropriate extension gap of the knee joint 700. In this regard, spacer devices as are known in the art, such as those described in PCT/AU2018/050208 and PCT/AU2018/050209, which are incorporated by reference herein, may be utilised so as to determine an appropriate soft tissue balance across the knee joint 700 in both extension and flexion prior to insertion of the sensor devices 100,200,600 therein.

Preferably, resection of the proximal tibia 901 and/or the distal femur 801 requires the determination of a joint line on, for example, a three-dimensional model of the aligned knee in extension and/or flexion. As would be readily understood, engagement of the lateral and medial femoral condyles with the superior surface of the tibia 900 of the extended knee establishes a joint line. Accordingly, such determination may be made at least in part from one or more anatomical indicators, including, but not limited to, a distal portion of a medial condyle, a distal portion of a lateral condyle, a proximal portion of the medial tibial plateau, a proximal portion of the lateral tibial plateau, a central portion of a lateral meniscus and a central portion of a medial meniscus.

Referring to Figure 5, the first and second sensor devices 100,200 are then inserted into the extension gap to act or function as femoral and tibial trial implants 110,210 respectively. In this manner, the first and second sensor devices 100,200 are not only configured to appropriately engage or abut the respective articulating surfaces 116,218 therebetween, but also the cut surfaces 802-804,902 of the distal femur 801 and the proximal tibia 901. Although not shown in Figure 5, it will be appreciated that the spacer devices 500,1000 hereinbefore described may be similarly inserted in the extension gap to not only determine an appropriate soft tissue balance across the knee joint 700, but also bring the sensor film 530,1030 in contact with one or more resected surfaces 802-804,902 thereof.

Additionally, for the third sensor device 600, the posterior surface 751 of the patella 750 can be exposed by means of conventional surgical techniques such as slitting the supporting side tendons and rotating the patella 750 to expose the posterior surface 751 thereof. The posterior surface 751 of patella 750 can then be resected to remove the damaged areas such that a generally flat surface area remains. One or more circular holes or depressions 752a-c may be formed or drilled in the resected posterior surface 751 of the patella 750 to matingly accept the studs 6l8a-c of the trial patellar implant 610. The third sensor device 600 can then be secured in place adjacent the resected posterior surface 751 of the patella 750 by, for example, sutures and the like, if required.

Although illustrated as a sensor film for the embodiments of sensor devices 100,200,600 and spacer devices 500,1000 described herein, it is envisaged that the electronic force sensor or sensor film provided herein could be any as are known in the art that may be appropriately utilised for the present invention. This may include, for example, a thin film sensor, a thick film sensor, a piezoelectric sensor, a capacitive sensor, and an electromechanical sensor (e.g., a strain gauge sensor), albeit without limitation thereto.

The sensor film 120,220,620,530,1030 described herein can comprise any sensor film, sensor array or thin film sensor material known in the art. By way of example, reference is made to US Publication No. 2018/0003577, which is incorporated by reference herein. Other embodiments of the sensor film 120,220,620 may include resistive elements, which respond to changes in pressure or force with changes in resistance, and/or capacitive sensors. The array of force sensor elements 121,221,621 may be configured in a row/column format, although other configurations are possible, as the invention is not limited in this respect. As used herein, the force sensor elements 121,221,621,531,1031 can have any suitable size and/or shape, as the invention is not limited in this respect.

With respect to the above and referring to Figure 5, force data 350 measured or acquired by one or more of the first, second and third sensor films 120,220,620 of the first, second and/or third sensor devices 100,200,600 or the sensor films 530,1030 of the spacer devices 500,1000 may then be transmitted by any wired means and/or wirelessly to an external or remotely located processor 410 and/or computer device 400. In typical embodiments, the force data 350 can be transmitted by way of a conventional data transmission protocol as are known in the art, such as BlueTooth, Wi-Fi or the like. In an alternative embodiment, the force data 350 measured or acquired by the sensor films 120,220,620,530,1030 is transmitted wired and/or wirelessly to a processor disposed in or on the respective sensor device 100,200,600 or spacer device 500,1000 itself.

Once processed by the processor 410 and/or the computer device 400, the force data 350 can then be transmitted to a display 450 and/or a projector unit 460 operably coupled or connected thereto. In the embodiment provided in Figure 5, a force exerted on the sensor films 120,220,620,530,1030 changes the resistance of one or more of the respective sensor elements 121,221,621,531,1031, which is sent to the processor 410 and/or computer device 400, where it is processed and converted to an array of pressure values by software therein to define a topographical surface map, a pressure map, a pressure distribution map or a heat map 300, thereby illustrating the force data 350 topographically or spatially across the cut surface of the bone in question. This surface map 300 can then be displayed on the display 450 and/or directly projected onto the associated cut surface by the handheld projector unit 460. It is further envisaged that the surface map 300 can be displayed to a surgeon by way of an augmented reality or virtual reality standalone systems or navigation systems, as are known in the art.

It is envisaged that the surface map 300 can be a three-dimensional plot or a two-dimensional intensity plot wherein various colors correspond to particular load or force values. It is further contemplated that the processor 410 and/or computer 400 can be configured to display the surface map 300 substantially in real-time. In the embodiment provided, the computer 400 includes a memory unit 420 adapted to store the force or pressure data and/or calculations for the plurality of sensor elements 121,221,621 for future analysis and graphical display by the surgeon if required.

In this manner, the present sensor devices 100,200,600 and/or spacer devices 500,1000 allow a surgeon to observe on the surface map 300 any defects, deficits and/or variations that may be present in the resected surface 902 of the tibia 900 distal to the trial tibial implant 210, the resected surfaces 802-804 of the femur 800 proximal to the trial femoral implant 110 and/or the posterior resected surface 751 of the patella 750 that are currently imperceptible to the naked eye and/or present prior art detection methods. As noted earlier, a joint implant could be perfectly level with the underlying bone and exhibit no gaps around the visible circumference therebetween, but still possess one or more significant concave or convex defects or deficits in one or more portions of the cut surface thereof. Further to this and even with cut surfaces that have minimal or no detectable deficits or defects therein, the sensor devices 100,200,600 and spacer devices 500,1000 of the invention also advantageously afford the ability for surgeons to accurately visualise soft tissue balance around the associated joint.

After viewing the topographic analysis or surface map 300, the surgeon could employ a variety of corrective actions. Such actions could include, although not be limited to, readjusting the joint line or resurfacing the cut.

The surgeon could mark the cut surface of the bone in question with, for example, a sterile ink marker whilst a representation of the surface map 300 is displayed upon it by the projector unit 500. Corrective cuts and/or resurfacing could then be performed based upon there indicator marks. In this regard, the surgeon could use either mechanical or hand tools freehand whilst the surface map 300 is appropriately displayed upon the cut surface to effect corrections or alternatively existing cutting blocks may be used. The surgeon could then repeat the previously described method to assess the cut surface of the bone with the sensor devices 100,200,600 and/or spacer devices 500,1000 described herein to confirm the revised cut(s) effectiveness.

After analysis of the topographic pressure data or surface map 300 and subsequent corrective action, the surgeon could decide that the resected surfaces of the bone in question are sufficiently precise that an uncemented tibial tray may be the most appropriate prothesis or implant to use. This may save surgical time, as cementing an implant to a bone can add up to 15 minutes to a surgical procedure such as TKA, whereas retesting to produce a cut surface with little or no imperfections or deficits may only take 5 - 10 minutes.

Accordingly, the sensor devices 100,200,600 and the spacer devices 500,1000 described herein can advantageously provide for the combination of a sufficiently precise cut having little or no obvious radiolucent lines, and an uncemented implant, which can result in a stronger implant to bone interface and reduced operating time. Each of these outcomes is advantageous for patients, surgeons and medical expense providers alike.

Suitably, the sensor devices 100,200 and the spacer devices 500,1000 described herein are suitable for use throughout the range of motion of the knee joint 700 (e.g., full flexion to full extension, i.e., approximately 0 degrees when full extended to approximately 160 degrees when fully flexed). The skilled artisan, however, would appreciate that this may not be possible or feasible in all patients, owing, for example, to the presence of pre-existing disease or deformities of the limb. By way of example, a patient with a flexion deformity or contracture of the knee may be physically unable to fully flex or extend the knee.

As used herein, the terms“ approximately” and“ about” refer to tolerances or variances associated with numerical values recited herein. The extent of such tolerances and variances are well understood by persons skilled in the art. Typically, such tolerances and variances do not compromise the structure, function and/or implementation of the devices and methods described herein. Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention.

All computer programs, algorithms, patent and scientific literature referred to herein is incorporated herein by reference.

Claims

1. A sensor device for assisting a surgeon during joint surgery on a patient comprising:

2. The sensor device of Claim 1, wherein the sensor is configured to measure the one or more forces so as to define a surface map relating to force measurements received thereby.

3. The sensor device of Claim 1 or Claim 2, wherein the sensor is reversibly engaged to the contact surface of the trial implant.

4. The sensor device of Claim 1 or Claim 2, wherein the sensor is integral with or adhered to the contact surface of the trial implant.

5. A spacer device for assisting a surgeon during joint surgery on a patient comprising:

a spacer body having one or more contact surfaces for contacting respective one or more resected surfaces of a bone; and

6. The spacer device of Claim 5, which comprises one or more U-shaped support portions that define first and/or second contact surfaces.

7. The spacer device of Claim 6, wherein the first and/or second contact surfaces are to be positioned adjacent a resected distal femoral surface, a posterior femoral surface and/or a resected proximal tibial surface.

8. The spacer device of Claim 5, wherein the spacer body comprises:

9. The spacer device of Claim 8, wherein the outer surface of the lateral member and/or the first end of the support portion are to be positioned adjacent a resected distal femoral surface, a posterior femoral surface and/or a resected proximal tibial surface.

10. A system for assisting a surgeon during joint surgery on a patient comprising: a sensor device according to any one of Claims 1 to 4 and/or a spacer device according to any one of Claims 5 to 9; and

a processor operably connected to the sensor device and/or the spacer device and configured to process the one or more forces measured by the sensor.

11. The system of Claim 10, wherein the processor is adapted to generate a surface map relating to the one or more forces measured by the sensor.

12. The system of Claim 10 or Claim 11, further comprising a display operably connected to the processor and configured to display the one or more forces measured by the sensor.

13. The system of Claim 12, wherein the display is configured to display the surface map generated by the processor.

14. The system of any one of Claims 10 to 13, further comprising a projector for projecting the surface map onto the one or more resected surfaces of the bone.

15. A method for assisting a surgeon during joint surgery on a patient including the steps of:

(a) positioning a sensor device according to any one of Claims 1 to 4 and/or a spacer device according to any one of Claims 5 to 9 adjacent one or more resected surfaces of a bone of the joint of the patient; and

(b) measuring one or more forces exerted by the one or more resected surfaces of the bone on a contact surface of the sensor device and/or the spacer device by a sensor.

16. The method of Claim 15, further including the step of generating by a processor a surface map relating to the one or more forces measured by the sensor.

17. The method of Claim 15 or Claim 16, further including the step of displaying on a display the one or more forces measured by the sensor.

18. The method of Claim 17, wherein the displaying step includes displaying the surface map generated by the processor.

19. The method of any one of Claims 16 to 18, further including the step of projecting the surface map onto the one or more resected surfaces of the bone.

20. The method of any one of Claims 15 to 19, wherein the step of measuring the one or more forces exerted on the contact surface of the sensor device and/or the spacer device is performed substantially throughout the range of motion of the joint.

21. The method of any one of Claims 15 to 20, further including the step of detecting one or more defects or deficits in the one or more resected surfaces of the bone.

22. The method of any one of Claims 15 to 21, further including the step of using the force measured to determine a course of action associated with joint surgery on the patient.

23. The method of Claim 22, wherein the course of action includes further resection of one or more of the resected surfaces of the bone.

24. The method of Claim 23, wherein the course of action includes further resection of the resected distal femoral surface, the resected posterior femoral surface, the resected anterior femoral surface, the resected proximal tibial surface and/or the resected posterior patellar surface.

25. The method of any one of Claims 22 to 24, wherein further resection is the course of action when:

26. The sensor device, spacer device, system or method of any one of the preceding claims, wherein the joint is suitably a knee joint.

27. The sensor device, system or method of any one of Claims 1-4 and 10-26, wherein the trial implant is or comprises a trial femoral implant, a trial tibial implant and/or a trial patellar implant.

28. The sensor device, spacer device, system or method of any one of the preceding claims, wherein the one or more resected surfaces comprises one or more of a resected distal femoral surface, a resected anterior femoral surface, a resected posterior femoral surface, a resected proximal tibial surface and a resected posterior patellar surface.

29. The method of any one of Claims 15 to 28, wherein the step of positioning the sensor device and/or the spacer device may comprise positioning the sensor device and/or spacer device adjacent a resected femur, a resected tibia and/or a resected patella.

30. The sensor device, spacer device, system or method of any one of the preceding claims, wherein the sensor is selected from the group consisting of a sensor film, an electromechanical sensor, a piezoelectric sensor, a capacitive sensor and any combination thereof.

31. The sensor device, spacer device, system or method of Claim 30, wherein the sensor is or comprises a sensor film comprising a plurality of force sensor elements.