Intra-operative arthroplasty system

Abstract

Intra-operative adjustment system (1) for a reversed total shoulder arthroplasty procedure, the intra-operative adjustment system comprising a trial humeral articular component (2) configured for mounting on a stem (104) of a humeral assembly (102) of a reversed total shoulder arthroplasty prosthesis (101), the trial humeral articular component (2) comprising a trial metaphysis component (4) having a housing (41), a sensor system (5) mounted in the housing (41), and a trial liner (3) removably mountable to the housing (41) and configured for coupling to the sensor system (5), the sensor system (5) including a force sensing system (6). The force sensing system (6) comprises a shear force sensing device (8) configured for measuring a shear force acting on the trial liner (3) in a shear plane (Sxy) and a compression force sensing device (10) configured to measure a compression force acting on the trial liner (3) in a compression direction (Z) orthogonal to the shear plane.

Description

[0001] P3003PC00

[0002] INTRA-OPERATIVE ARTHROPLASTY SYSTEM

[0003] The present invention relates to a system and device for intra-operative assessment of arthroplasty, in particular reversed total shoulder arthroplasty.

[0004] Restoration of shoulder function by modification of native shoulder biomechanics using reversed total shoulder arthroplasty (rTSA) has evolved as the favoured technique for shoulder joint replacement. rTSA was initially developed for the management of shoulder osteoarthritis associated with rotator cuff tendons insufficiency. It is now indicated as well for severe proximal humerus fractures, irreparable rotator cuff tears, severe osseous anatomy alterations, and tumour surgery.

[0005] During surgical procedures, trial implants are used for assessment of prosthetic joint function before definitive components implantation. Throughout trial phase, individual trial components of the prosthesis can be selected from the complete array of available sizes and shapes until function is determined optimal. Final prosthetic components are then prepared and implanted. In common practice, joint mobility and stability are manually tested by surgeons through an iterative process to optimise range of motion and limit risks of complication under the form of instability or implant fixation failure. Both elements have been reported to display a competing relationship and represent key efficacy and safety features. In its current state, there is considerable room for improving this procedure which remains qualitative and subjective. In particular, instability represents the most common cause of early revision of rTSA (reported in up to 25% of the cases). The main proposed causes of instability are inadequate soft tissue tensioning as well as component sizing / mispositioning potentially leading to impingement against surrounding structures. Increasing incidence of rTSA procedure is paralleled by increasing numbers of revision in shoulder arthroplasty procedures.

[0006] A prosthesis for rTSA is conventionally constituted of three primary component groups: glenoid components (i.e. a baseplate, a glenosphere, and screws), humeral components (i.e. stem and metaphysis), and a liner constituting the humeral articular surface. The configuration of the glenoid components determines the position of the centre of rotation, the configuration of the humeral components modulates the final humeral position relative to the centre of rotation, and the design of the liner modulates joint tension and congruency of the humeral components around glenoid components respectively. Native shoulder girdle can be seen as a P3003PC00 fine compromise between mobility and stability and rTSA aims to restore this balance to ensure successful joint replacement.

[0007] From a clinical point of view, joint stability is assimilated to joint dislocation and can be synthetised as the ratio between the shear force and the compressive force components in the joint. Indeed, while the compressive force component is directed to the joint centre and thus may ensure joint stability, the shear force component tends to destabilise the joint by translating the humeral head towards the glenoid rim. Causes for instability are thus reported to be multifactorial, comprising active and passive constraints. From the surgeon's perspective, numerous parameters of the primary implant may be tuned to optimise stability, varying between implants. They can be summarised as 1) increase / decrease of the liner cup height and depth, 2) increase / decrease of the neck-shaft angle, 3) offset of the humeral component, and 4) increase / decrease of the glenosphere diameter and offset. The primary aim of this tuning is then to modulate tensioning associated with horizontal and vertical displacement of soft tissue insertions on the humerus. Furthermore, tissue tensioning represents a key determinant of other potential complications including periprosthetic fatigue fractures and nerve traction injuries.

[0008] Implant efficacy on the other hand is predominantly related to the resulting joint mobility. From a clinical point of view, shoulder mobility is the result of the motions of glenohumeral and scapulothoracic joints. In particular, the large glenohumeral joint range of motion is partly due to a small glenoid articular surface and a loose connecting capsule. Causes for limited mobility are reported to be related of repositioned humerus and / or humeral implant abutment against surrounding structures. From the surgeon's perspective, primary implant parameters that can be tuned to optimise mobility can be summarised as 1) medial / lateralisation location of the glenosphere centre of rotation, 2) proximal / distal positioning of the glenosphere, 3) inferior / superior tilt of the glenosphere, 4) increase / decrease of the glenosphere diameter, 5) offset of the humeral component, 6) height and retroversion of the humeral component, and 7) inclination of the neck shaft angle. The primary aim of this tuning is then to increase the impingement free range of motion.

[0009] Evaluation of rTSA safety and efficacy is commonly made at three stages including the preoperative stage, the intra-operative stage, and the post-operative stage.

[0010] During the pre-operative stage, the surgery procedure is planned. Commonly based on computer tomography (CT) scan images, 3D models of the scapula and humerus are first P3003PC00 prepared. This allows for patient-specific numerical simulations assisting surgeon choices in terms of components size, shape, position, and orientation with the aim of 1) optimising joint mobility, i.e. implant efficacy, and 2) defining screw trajectories that secure anchoring in adequate-quality bone stock. In particular, to assess implant efficacy, parameters such as joint range of motion and bone collision location can then be numerically estimated.

[0011] During the intra-operative stage, trial implants are used for assessment of prosthetic joint function before implantation of definitive components. In common practice, implant safety and efficacy are manually tested by surgeons during this stage. The joint is mobilised in internal / external rotation in adducted / ab ducted position, and using tests such as the Shuck Test, the Bed Shuffle Test, and the Lateral Trust Test. Parameters such as joint displacement and dislocation are subjectively assessed by the surgeon. Depending on these parameters, individual trial components of the implant can be selected from the complete array of available sizes and shapes until function is determined optimal. Final implant components are then prepared and installed.

[0012] In a recent study involving two French tertiary specialist shoulder centres, the authors reported a clear increasing incidence of rTSA procedure compared to other shoulder prostheses, which is confirmed abroad by other studies. This growth is paralleled by an increasing number of shoulder arthroplasty revisions and overall cost to the health care system. These studies also highlight that the most common indications for revision after rTSA are related to joint instability (25 to 32%). The management of implant safety and efficacy is thus of primary importance to limit revision risk and contain overall costs.

[0013] All previously defined stages, i.e. pre-operative, intra-operative, and post-operative stages, influence implant safety and efficacy. However, the intra-operative stage is important to address the main causes of instability which include inadequate soft tissue tensioning as well as component mispositioning potentially leading to impingement. The use of intra-operative sensors in orthopaedic surgery is known for total knee arthroplasty (TKA).

[0014] In the field of rTSA, to the inventors’ knowledge, there is currently no commercially available intra-operative sensor, however some concepts have been investigated aiming to guide the surgeon in the optimisation of implant safety and efficacy. In a first approach, a sensor is installed in the glenoid component. It is made of four uniaxial strain gauges on a rectangleshape tool connecting the glenosphere to the baseplate. In vitro and intra-operative studies have been then performed, allowing for providing intra-operative ranges of joint contact P3003PC00 forces during standardised humerus motions (i.e. elevation in coronal, sagittal and scapular planes, external rotation). Implanting sensors in the glenoid is however disadvantageous in view of the operations required to replace the trial glenoid component, or to leave the implanted sensors in the final prosthesis.

[0015] In a second approach, a sensor is installed in a trial liner. This has been done using uniaxial strain gauges and uniaxial capacitive load transducers. In both cases, an instrumented trial liner was designed, maintaining dimensional equivalence to the normal trial component, and ensuring the possibility to simulate different insert thicknesses. The resulting instrumentations allow only for quantifying the compressive component of the joint contact force (Fz).

[0016] In a third approach, a sensor is installed in the final implant humeral component. Rather than using a trial phase, this solution proposes an adjustable implant after implantation to optimise joint mobility and stability. Again, only the compressive component of the joint contact force (Fz) is used in this approach.

[0017] Prototype sensor studies have demonstrated the feasibility of intra-operative joint contact forces quantification in rTSA. However, successful implementation of a tool assisting surgeons in the optimisation of rTSA implant sizing and positioning would need to address various factors.

[0018] First, for assessing and improving joint stability, it would be advantageous to measure all of the three joint contact force components. Indeed, from a mechanical point of view, joint stability depends from the ratio between the shear force (Fx, Fy) and the compressive force (Fz) components in the joint. The compressive component of the joint contact force, used in several studies, may only provide to the surgeon feedback about the impact of the implant positioning and sizing on soft tissue loading (in particular deltoid fibres). However, it has already been demonstrated that after rTSA, the deltoid may not only contribute to a joint compressive force, but also to a significant increase of a glenohumeral joint superior shear.

[0019] Second, it would be advantageous to reduce operative time to reduce risk of intra / post- operative complication and costs. In this sense, the instrumentation of the trial liner is of superior interest than the glenoid components. Indeed, the installation / deinstallation of this liner only requires decoaptation of the humerus components without the need of screws or tools. Instead, for glenoid components a full posterior joint dislocation is required to give access to the glenoid, with the arm in external rotation, as well as the need of screws and tools. P3003PC00

[0020] In addition to increase operating time, this procedure leads to a greater risk of nerve injury that can conduct to persistent neurologic deficits.

[0021] It is thus needed to provide a sensing device to measure compression forces during an intraoperative procedure, the sensors being installed in the trial liner in order to assist the surgeon to select the components with a desired shape and size for the final prosthesis.

[0022] The drawback of conventional systems is however the inability to properly take into account forces in compression a well as in shear forces in a direction orthogonal of direction of compression for optimal selection of the prosthesis components in particular the humeral component shape and dimensions. Another drawback of many intra-operative systems is the complexity and increase of operation time either due to the difficulty of correctly placing the sensors and properly reading the measurement data to arrive at a correct assessment of the shape and dimensions of the humeral assembly and in particular the liner thereof.

[0023] In view of the foregoing, it is an object of this invention to provide an intra-operative adjustment system for arthroplasty that is easy to install and remove in a surgery setting, and that provides comprehensive and accurate measurement data allowing a surgeon to select the optimal prosthesis components.

[0024] It is advantageous to provide an intra-operative adjustment system that is reliable and easy to use.

[0025] It is advantageous to provide an intra-operative adjustment system that minimizes the surgery time.

[0026] It is advantageous to provide an intra-operative adjustment system that is economical to produce and operate.

[0027] Objects of the invention have been achieved by providing a system according to claim 1.

[0028] Dependent claims set out various advantageous features of embodiments of the invention.

[0029] Disclosed herein is an intra-operative adjustment system for a reversed total shoulder arthroplasty procedure, the intra-operative adjustment system comprising a trial humeral articular component configured for mounting on a stem of a humeral assembly of a reversed P3003PC00 total shoulder arthroplasty prosthesis, the trial humeral articular component comprising a trial metaphysis component having a housing, a sensor system mounted in the housing, and a trial liner removably mountable to the housing and configured for coupling to the sensor system, the sensor system including a force sensing system.

[0030] The force sensing system comprises a shear force sensing device configured for measuring a shear force acting on the trial liner in a shear plane (Sxy) and a compression force sensing device configured to measure a compression force acting on the trial liner in a compression direction (Z) orthogonal to the shear plane.

[0031] In an advantageous embodiment, the force sensing system comprises an elastic liner support including a shear plane spring and an axial compression spring, the trial liner comprising a coupling interface configured to engage the shear plane spring and axial compression spring, the elastic liner support configured to allow elastic displacement of the trial liner in a direction of the shear plane (Sxy) and the compression direction (Z).

[0032] In an advantageous embodiment, the shear plane spring comprises a plurality of upstanding spring blades, the shear plane spring fixed to the housing.

[0033] In an advantageous embodiment, the upstanding spring blades and a base form a crown structure, the coupling interface of the trial liner having a plurality of complementary recesses within which the upstanding spring blades are lodged.

[0034] In an advantageous embodiment, the upstanding spring blades and base are stamped and formed from sheet metal.

[0035] In an advantageous embodiment, the axial compression spring comprises a plate spring.

[0036] In an advantageous embodiment, the plate spring comprises a plurality of plate spring blades.

[0037] In an advantageous embodiment, the plate spring blades extend radially outwardly from a center portion of the plate spring.

[0038] In an advantageous embodiment, the shear force sensing device comprises a plurality of strain gauges bonded to the shear plane spring.

[0039] In an advantageous embodiment, the strain gauges are bonded to the upstanding spring blades configured to measure a bending strain of the spring blades. P3003PC00

[0040] In an advantageous embodiment, the housing has a peripheral wall having a substantially circular shape and the upstanding spring blades are arranged in a spaced apart manner adjacent an inner side of the peripheral wall around the full circumference of the peripheral wall.

[0041] In an advantageous embodiment, the compression force sensing device comprises strain gauges bonded to the axial compression spring.

[0042] In an advantageous embodiment, the strain gauges are bonded to plate spring blades.

[0043] In an advantageous embodiment, the shear force sensing device and compression force sensing device comprise optical sensors configured for measuring a displacement of the shear plane spring, respectively axial compression spring, or of the trial liner coupling interface.

[0044] In an advantageous embodiment, the trial liner comprises or consists of an engineering plastic such as polyoxymethylene (POM).

[0045] In an advantageous embodiment, the system further comprises a computing system having a force measurement module installed therein configured for receiving measurement data output by the shear force sensing device and the compression force sensing device and processing said measurement data to output information and optionally recommendations on the shear force and compression force to assist in assessing an optimal shape and dimensions of a liner of the reversed total shoulder arthroplasty prosthesis.

[0046] In an advantageous embodiment, the sensor system comprises an electronic circuit including a circuit substrate coupled to the shear sensing device and compression force sensing device.

[0047] In an advantageous embodiment, the electronic circuit comprises a battery and a wireless communication module for wireless transmission of measurement data to the computing system.

[0048] In an advantageous embodiment, the electronic circuit is connected via a wired connection to the computing system or to an electronic module installed outside of the housing of the trial metaphysis component.

[0049] In an advantageous embodiment, the sensor system further comprises an accelerometer coupled to the trial liner or to the metaphysis component configured to measure 3D kinematics of the trial liner. P3003PC00

[0050] In an advantageous embodiment, the coupling interface of the trial liner comprises bottom end protuberances engaging the axial compression spring.

[0051] Embodiments of the invention advantageously optimise the trial phase of the primary reversed total shoulder arthroplasty procedure and reduce the risk for patients to undergo multiple surgery revisions and related costs.

[0052] Further advantageous features of the invention will be apparent from the following detailed description of embodiments of the invention and the accompanying illustrations.

[0053] Brief description of the figures

[0054] Figure l is a schematic illustration of a reversed total shoulder arthroplasty system showing a reversed total shoulder arthroplasty prosthesis installed by a surgeon with the assistance of computing system and an intra-operative adjustment system according to an embodiment of the invention;

[0055] Figure 2a illustrates a humeral assembly implanted in a humerus and comprises a trial humeral articular prosthesis component assembled to an implanted humeral articular component, according to an embodiment of the invention;

[0056] Figure 2b is a similar to figure 2a with the trial humeral articular prosthesis component replaced with the final humeral articular component of a prosthesis;

[0057] Figure 2c illustrates an articular portion of a humeral assembly implanted in a humerus to show dimensional characteristics affecting joint stability and mobility;

[0058] Figure 3a is an exploded perspective view of a humeral assembly comprising a trial humeral articular component mounted on an implanted humeral bone component, according to an embodiment of the invention;

[0059] Figure 3b is a view similar to figure 3a from a different angle;

[0060] Figure 3c is a top cross-sectional view of the embodiment of figures 3a, 3b;

[0061] Figure 3d is a close-up view of a portion of figure 3b;

[0062] Figure 3e is a close-up view of a portion of figure 3c;

[0063] Figure 4a is a side cross-sectional view of a humeral assembly comprising a trial humeral articular component mounted on an implanted humeral bone component, according to the first embodiment illustrated in figures 3a to 3c;

[0064] Figures 4b, 4c and 4d are detailed views of areas IVb, IVc and IVd of figure 4a; P3003PC00

[0065] Figure 5a is an exploded perspective view of a humeral assembly comprising a trial humeral articular component mounted on an implanted humeral bone component, according to a second embodiment of the invention;

[0066] Figure 5b is a view of the components of figure 5a from a different angle;

[0067] Figure 5c is a top cross-sectional view of the embodiment of figures 5a, 5b;

[0068] Figure 6a is a longitudinal cross-sectional view of the assembled components of figure 5a;

[0069] Figure 6b is a detailed view of the area VIb of figure 6a;

[0070] Figure 6c is a detailed view of the area Vic of figure 6a.

[0071] Referring to the figures starting with figure 1, an arthroplasty system, in particular a reversed total shoulder arthroplasty system 100 is illustrated. The reversed total shoulder arthroplasty system 100 comprises a reversed total shoulder arthroplasty prosthesis 101 implanted by a surgeon with the assistance of an intra-operative adjustment system 1 according to embodiments of the invention. The intra-operative adjustment system 1 includes a computing system 9 and a trial humeral articular component 2 (as illustrated in figures 2a, 3a to 6c) providing measurement data, in particular force measurement data, transmitted to the computing system 9 to assist the surgeon in selecting the optimal prosthesis for a particular patient, in particular an optimal humeral articular component 106.

[0072] A reversed total shoulder arthroplasty prosthesis 101, per se well known in the art, typically comprises a humeral assembly 102 fixed to the patient’s humerus 201, and a glenoid assembly 103 fixed to a patient’s scapula 202.

[0073] The glenoid assembly 103 comprises a gl enosphere component 107 having a spherical convex joint surface. The gl enosphere component 107 is mounted on a base component 108 that is fixed to the patient’s scapula 202 with screws (not shown). Such glenoid assemblies 103 are well known and do not need to be further described herein.

[0074] The humeral assembly 102 comprises a stem 104 for insertion in the canal of the shaft of the humerus 201 as per se well known in the field. A metaphysis component 105 is coupled to the stem 104 and comprises a liner 106, typically a liner, with a concave joint surface complementary to the convex spherical joint surface of the gl enosphere component 107. P3003PC00

[0075] Adjustment of the relative position of the glenoid assembly 103 and humeral assembly 102 for optimal joint stability and mobility is variable and depends on the patient’s morphology. The joint stability and mobility may be adjusted by the surgeon during the intra-operative phase by selecting a humeral articular component from a range of different shaped and dimensioned humeral articular components.

[0076] Referring to figure 2c, different humeral articular components for different patients may have different shapes and dimensions, these dimensions including:

[0077] - the lateral position of the centre C of the joint surface 31 relative to the assembly plane

[0078] Sxy of the stem 104,

[0079] - the tilt angle P and tilt orientation (position within the cone A) of the centre C of the joint surface 31 relative to the axis Z orthogonal to the assembly plane Sxy,

[0080] - the radius R of the j oint surface,

[0081] - the height H of the liner relative to the assembly plane Sxy (i.e thickness of the liner).

[0082] Dimensions of the glenoid assembly components and humeral assembly components are defined in a pre-operative stage whereas in the intra-operative stage typically the glenoid assembly will be predefined with a specific gl enosphere component 107 and the humeral assembly 102 with a specific dimensioned and shaped stem 104. The radius R of the joint surface will typically be defined and set in the pre-operative stage. Adjustments occur typically on the liner 110 of the humeral articular component 106 which may be selected from one of a plurality of liners of different shapes and sizes.

[0083] It may further be possible in the intra-operative stage to also change the glenosphere component 107 that is fitted on the base component 108 fixed with screws to the patient’s scapula 202. It may be necessary to change the glenosphere component 107 if the radius R of the joint surface needs to be increased or decreased, but typically in the intra-operative stage the dimensions that are predefined will not require modification of the radius R of the joint surface. This is also preferably avoided due to the risk of scapular fractures when manipulating intra-operatively the glenosphere component 107.

[0084] An intra-operative adjustment system 1 according to embodiments of the invention as mentioned above comprises a trial humeral articular component 2 and a computing system 9 connectable to the trial humeral articular component for receiving and processing measurement data of forces sensed by the trial humeral articular component. A force P3003PC00 measurement module installed in the computer system 9 is configured to process the force measurement data and to provide information to the surgeon intra-operatively on adjustments in the position and dimensions of the liner, or to provide a recommendation on the proposed liner to achieve the target shear and compression forces for an optimal prosthesis satisfying the desired aim of stability and mobility.

[0085] In embodiments, the computing system 9 may be further configured to process kinematic data to improve the assessment of mobility and stability.

[0086] The trial humeral articular component 2 according to embodiments of the invention comprises a trial metaphysis component 4 configured for assembly to a mounting interface of the stem 104 of the humeral assembly 102, a trial liner 3 assembled over the trial metaphysis component 4, and a sensor system 5 mounted within the trial metaphysis component 4 below the trial liner 3. The trial liner 3 comprises a coupling interface 33 configured to couple to the sensor system 5. The trial liner may be made for instance of polyethylene, as often observed for the prosthesis liner 106 of the humeral assembly.

[0087] The trial humeral articular component 2 may include a plurality of trial liners 3 of different shapes and dimensions as previously mentioned and repeated hereafter for convenience (with reference to figure 2c:

[0088] - the lateral position of the centre C of the joint surface 31 relative to the assembly plane Sxy of the stem 104,

[0089] - the tilt angle P and tilt orientation (position within the cone A) of the centre C of the joint surface 31 relative to the axis Z orthogonal to the assembly plane Sxy, the radius R of the j oint surface,

[0090] - the height H of the liner relative to the assembly plane Sxy (i.e thickness of the liner), from which the surgeon can select during the intra-operative stage. The surgeon may start with a trial liner dimensioned during the pre-operative stage, and replace with a different trial liners 3 during the intra-operative stage if the assessment based on the measurement data obtained from with the first trial liner leads to a recommendation to modify dimensions. If necessary, the process can be repeated until dimensions of an optimal trial liner are determined. The force measurement module software installed in the computer 9 may advantageously be configured to provide recommendations on the shape and dimensions of the trial liner to be selected as a function of the shear and compression forces measured by the sensor system on a specific liner 3. Such recommendation reduces the trial liner replacement P3003PC00 steps to find an optimal dimensioned humeral articular component for the final installed prosthesis.

[0091] The trial metaphysis component may have a general cup shaped housing 41 comprising abase 43 and a peripheral wall 45 upstanding therefrom, the base configured for fixing with screws or bolts to the coupling interface of the humeral stem 104. The housing 41 receives therein the sensor system 5, the open end of the housing closed by the trial liner 3 when the parts are assembled together.

[0092] The trial liner 3 is removably mountable to the housing of the trial metaphysis component 4 so that different trial liners 3 may be mounted to the trial metaphysis component 4. In a variant, the trial liner 3 may be positionable in different angular orientations with respect to the trial metaphysis component 4 such that a predefined trial liner with a certain height H of the joint surface and a certain tilt angle P with respect to the assembly plane Sxy may be selected. The orientation angle of the liner rotated about the center axis Z may be varied by turning the selected trial liner 2 about the centre axis Z to change the orientation angle relative to the stem. The variable angular orientation may take discreet positions, i.e. step changes, for instance by having the trial liner coupling interface 33 provided with protrusions 35 and recesses 37, for instance in a form of a splined shaft surface, that interengage with complementary teeth or recesses in the trial metaphysis component 4 and / or sensor system 5. In the illustrated embodiments, the sensor system comprises upstanding spring blades 24 that are inserted in the recesses 37 between the protrusions 35.

[0093] The sensor system 5 comprises a force sensing system 6 including a liner spring support 7, a shear force sensing device 8, and a compression force sensing device 10. The liner spring support 7 comprises a base coupled with one or more fixing elements for instance in the form of screws 16 to the base 43 of the trial metaphysis component housing 41. The liner spring support 7 further comprises a shear plane spring 18 and an axial compression spring 20. The shear plane spring 18 is configured to allow lateral displacement, in other words a displacement in a direction having a component in the assembly plane Sxy, orthogonal to the direction of compression along the center axis Z, and the axial compression spring 20 allows displacement of the trial liner 3 in a direction parallel to the compression axis Z.

[0094] In an advantageous embodiment, as illustrated, the shear plane spring 18 comprises a base 14 and a plurality of upstanding spring blades 24 that may for instance form a crown shaped structure 22. The upstanding spring blades 24 are configured to be inserted in recesses 37 P3003PC00 between the protuberances 35 of the coupling interface 33 of the trial liner 3. A shear force having a main force component directed in the lateral plane Sxy will cause elastic bending of the upstanding spring blades 24 that provide an elastic counter reaction force against the applied shear force. Displacement in the shear plane Sxy is measured by the shear force sensing device 8.

[0095] In a first embodiment, the shear force sensing device 8 may comprise strain gauges 32 bonded to the upstanding spring blades 24 to measure a bending strain of the spring blades and thus a displacement in a specific direction in the assembly plane Sxy. Depending on which spring blades are bent and the amplitude of bending on the spring blades, in which the angular orientation / position of each spring blades is known, it is possible to determine the amplitude and direction of the elastic displacement due to applied shear force and thus the direction and amplitude of the applied shear force.

[0096] Instead of strain gauges mounted on the upstanding spring blades, optical sensors mounted on the peripheral wall 45 of the trial metaphysis component 4 may be provided to measure displacement by means of optical sensors. The optical sensors may measure displacement of the upstanding spring blades 24 or of the trial liner whereby also in this embodiment the direction and amplitude of the shear force component Fxy may be determined.

[0097] The amplitude of the compression force Fz may be measured by the compression force sensing device 10 where the displacement under compression force is subject to an elastic compression of the axial compression spring 20.

[0098] The axial compression spring 20 may take various forms, whereby in an advantageous embodiment as illustrated, the axial compression spring comprises a plate spring 26 with a plurality of plate spring blades 28, for instance in a star shaped arrangement. It may however be noted that various compression springs including a coil spring, other shapes of plate springs, or pads of elastomeric material may be provided as variants compression springs within the scope of the invention. The main function of the axial compression spring 20 is to provide a known elastic force that allows elastic displacement of the trial liner pressing thereagainst subject to a compression force. The axial displacement may be measured by strain gauges mounted on the plate spring 26, in particular the plate spring blades 28, or more generally on any elastic component. Similar to the embodiments available for the shear force sensing device, the compression force sensing device 10 may also comprise optical sensor 30 measuring a displacement of the axial compression spring 20. In variants, compression force P3003PC00 may be measured by capacitive, inductive or piezoelectric sensors measuring a displacement or a compression of spring material pressed by the trial liner coupling interface 33.

[0099] A motion sensor, for instance comprising an accelerometer coupled to the trial liner or the trial metaphysis component, may further be included in the sensor system, to output a measurement of 3D kinematics of the trial liner during the movement of the patient’s arm in addition to the measurement of the shear and compression forces Fz, Fxy.

[0100] P3003PC00

[0101] List of features

[0102] Hum eras 201

[0103] Scapula 202

[0104] Arthroplasty system

[0105] Reversed total shoulder arthroplasty system 100

[0106] Reversed total shoulder arthroplasty prosthesis 101

[0107] Humeral assembly 102

[0108] Stem 104

[0109] Metaphysis component 105

[0110] Humeral articular component 106

[0111] Liner 110

[0112] Glenoid assembly 103

[0113] G1 enosphere component 107

[0114] Base component 108

[0115] Fixing elements 109

[0116] Intra-operative adjustment system 1

[0117] Trial humeral articular component 2

[0118] Trial liner 3

[0119] Joint surface 31

[0120] Coupling interface 33

[0121] Side wall

[0122] Protrusions 35

[0123] Recesses 37

[0124] Bottom wall

[0125] Protuberances 39

[0126] Trial metaphysis component 4

[0127] Housing 41

[0128] Base 43

[0129] Peripheral wall 45

[0130] Fixing element 12

[0131] Sensor system 5

[0132] Force sensing system 6

[0133] Liner spring support 7

[0134] Base 14

[0135] Fixing element 16

[0136] Screws P3003PC00

[0137] Shear plane spring 18

[0138] Crown structure 22

[0139] Upstanding spring blades 24

[0140] Axial compression spring 20 Plate spring 26

[0141] Plate spring blades 28

[0142] Shear force sensing device 8

[0143] Optical sensor 30

[0144] Strain gauge 32 Compression force sensing device 10

[0145] Optical sensor 30

[0146] Strain gauge 32

[0147] Accelerometer

[0148] Computing system 9 Force (and motion) measurement module

Claims

P3003PC00Claims1. Intra-operative adjustment system (1) for a reversed total shoulder arthroplasty procedure, the intra-operative adjustment system comprising a trial humeral articular component (2) configured for mounting on a stem (104) of a humeral assembly (102) of a reversed total shoulder arthroplasty prosthesis (101), the trial humeral articular component (2) comprising a trial metaphysis component (4) having a housing (41), a sensor system (5) mounted in the housing (41), and a trial liner (3) removably mountable to the housing (41) and configured for coupling to the sensor system (5), the sensor system (5) including a force sensing system (6), characterized in that the force sensing system (6) comprises a shear force sensing device (8) configured for measuring a shear force acting on the trial liner (3) in a shear plane (Sxy) and a compression force sensing device (10) configured to measure a compression force acting on the trial liner (3) in a compression direction (Z) orthogonal to the shear plane.

2. The system according to claim 1 wherein the force sensing system (6) comprises an elastic liner support (7) including a shear plane spring (18) and an axial compression spring (20), the trial liner comprising a coupling interface (33) configured to engage the shear plane spring (18) and the axial compression spring (20), the elastic liner support configured to allow elastic displacement of the trial liner in a direction of the shear plane (Sxy) and in the compression direction (Z).

3. The system according to the preceding claim wherein the shear plane spring comprises a plurality of upstanding spring blades (24), the shear plane spring fixed to the housing (41).

4. The system of the preceding claim wherein the upstanding spring blades (24) and a base (14) form a crown structure (22), the coupling interface (33) of the trial liner (3) having a plurality of complementary recesses (37) within which the upstanding spring blades (24) are lodged.

5. The system according to any preceding claim wherein the axial compression spring (20) comprises a plate spring (26).

6. The system of the preceding claim wherein the plate spring (26) comprises a plurality of plate spring blades (28), preferably the plate spring blades (28) extending radially outwardly from a center portion of the plate spring.

7. The system of any preceding claim wherein the shear force sensing device (8)P3003PC00 comprises a plurality of strain gauges (32) bonded to the shear plane spring (18).

8. The system of the preceding claim in combination with claim 3 wherein the strain gauges are bonded to the upstanding spring blades (24) configured to measure a bending strain of the spring blades.

9. The system of any preceding claim in combination with claim 3 wherein the housing (41) has a peripheral wall (45) having a substantially circular shape and the upstanding spring blades (24) are arranged in a spaced apart manner adjacent an inner side of the peripheral wall around the full circumference of the peripheral wall.

10. The system of any preceding claim wherein the compression force sensing device (10) comprises strain gauges bonded to the axial compression spring (20), preferably wherein the strain gauges are bonded to plate spring blades (28).

11. The system of any preceding claim wherein the shear force sensing device (8) and compression force sensing device (10) comprise optical sensors configured for measuring a displacement of the shear plane spring (18), respectively axial compression spring (20), or of the trial liner coupling interface (33).

12. The system of any preceding claim further comprising a computing system (9) having a force measurement module installed therein configured for receiving measurement data output by the shear force sensing device and the compression force sensing device and processing said measurement data to output information and optionally recommendations on the shear force and compression force to assist in assessing an optimal shape and dimensions of a liner (110) of the reversed total shoulder arthroplasty prosthesis (101).

13. The system of any preceding claim wherein the sensor system (5) comprises an electronic circuit coupled to the shear sensing device (8) and compression force sensing device (10), optionally wherein the electronic circuit is connected via a wired or wireless connection to the computing system or to an electronic module installed outside of the housing (41) of the trial metaphysis component (4).

14. The system of the preceding claim wherein the electronic circuit comprises a battery and a wireless communication module for wireless transmission of measurement data to the computing system.

15. The system of any preceding claim wherein the sensor system further comprises an19P3003PC00 accelerometer coupled to the trial liner (3) or to the metaphysis component (4) configured to measure 3D kinematics of the trial liner.

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