Alignment of a femoral component in a patient with a knee endoprosthesis

Abstract

A method of assessing an alignment of a femoral knee arthroplasty component (2) in a patient, said method comprising the steps of: obtaining an orientation of a projection (9), onto a coronal plane, of an axis of a trochlear groove of a femoral knee arthroplasty component (2); and obtaining an orientation of a projection (10), onto the coronal plane, of a spherical axis of a femur (1) of the patient, which femur (1) is provided with said femoral knee arthroplasty component (2).

Description

[0001] Alignment of a femoral knee arthroplasty component in a patient

[0002] Description

[0003] Field of the invention

[0004] The invention relates to a method of assessing an alignment of a femoral knee arthroplasty component in a patient, to methods of planning an alignment of a femoral knee arthroplasty component in a patient, and to a method of monitoring an implanting of a femoral knee arthroplasty component in a patient. The invention moreover relates to methods of a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component in a patient, to methods of operation of a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component in a patient, and to methods of implanting a femoral knee arthroplasty component in a patient. Further, the invention relates to a medical image analysis apparatus for assessing, based on at least one image of the patient's femur and a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component, to medical image analysis apparatus for planning, based on an image of the patient's femur provided with a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component in a patient, and to a medical image analysis apparatus for predicting and monitoring, based on an image of the patient's femur provided with a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component in a patient. Also, the invention relates to a medical imaging apparatus, to a surgical navigation system (SNS), a robotically assisted surgical equipment (RASE) and a robotic surgical instrument (RSI) for assisting an implanting of a femoral knee arthroplasty component in a patient, and to a surgical navigation systems (SNS), a robotically assisted surgical equipment (RASE) and robotic surgical instruments (RSI) for assisting an implanting of a femoral knee arthroplasty component in a patient. Finally, the invention relates to a computer program product.

[0005] Background of the invention The publication by Tanifuji et al “The Vector of quadriceps pull is directed from the patella to the femoral neck”, Clin Orthop Relat Res (2013) 471:1014, discloses findings that an approximation of the quadriceps vector is closely aligned with a spherical axis defined as an axis connecting the spherical centre of the femoral head to the spherical centre of the medial femoral condyle.

[0006] The publication by Sappey-Marinier et al “The trochlear groove of a femoral component designed for kinematic alignment is lateral to the quadriceps line of force and better laterally covers the anterior femoral resection than a mechanical alignment design”, J Pers Med, 2022 October 16; 12(10): 1724, discloses that the orientation of a femoral arthroplasty component should preferably be lateral to the quadriceps line of force. It further discloses that the quadriceps line of force is directed along the line connecting the anterior inferior iliac spine (Al IS) to the center of the knee.

[0007] The publication by Howell SM et al “Better forgotten joint scores when the angle of the prosthetic trochlea is lateral to the quadriceps vector in kinematically aligned total knee arthroplasty”, Knee Surg Sports Traumatol Arthrosc. 2023 Oct 4. doi: 10.1007 / s00167- 02307598-3. Epub ahead of print. PMID: 37792084, discloses improved clinical outcome of kinematically aligned total knee arthroplasty when the angle of the prosthetic trochlea is lateral to the quadriceps vector (QV). It further discloses that the QV is orientated towards the AIIS.

[0008] Object of the invention

[0009] The present invention aims at The invention aims at improving the assessing an alignment of a femoral knee arthroplasty component in a patient, at improving the planning an alignment of a femoral knee arthroplasty component in a patient, and at improving the monitoring an implanting of a femoral knee arthroplasty component in a patient. The invention moreover aims at providing improved methods of a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI) assisting an implanting of a femoral knee arthroplasty component in a patient, improved methods of operation of a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component in a patient, and providing improved methods of implanting a femoral knee arthroplasty component in a patient. Further, the invention aims at providing an improved medical image analysis apparatus for assessing, based on at least one image of the patient's femur and a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component, an improved medical image analysis apparatus for planning, based on an image of the patient's femur provided with a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component in a patient, and an improved medical image analysis apparatus for predicting and monitoring, based on an image of the patient's femur provided with a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component in a patient. Also, the invention aims at providing an improved medical imaging apparatus, an improved surgical navigation system (SNS), an improved robotically assisted surgical equipment (RASE) and an improved robotic surgical instrument (RSI) for assisting an implanting of a femoral knee arthroplasty component in a patient, and an improved surgical navigation systems (SNS), an improved robotically assisted surgical equipment (RASE) and an improved robotic surgical instruments (RSI) for assisting an implanting of a femoral knee arthroplasty component in a patient. Finally, the invention aims at providing a new computer program product. In particular, the invention aims at providing the obove improvement in relation to a patient who has been provided with a total knee arthroplasty (TKA).

[0010] Solution according to the invention

[0011] In the following, any reference to one (including the articles “a” and “the”), two or another number of objects is, provided nothing else is expressly mentioned, meant to be understood as not excluding the presence of further such objects in the invention. The reference numerals in the patent claims are not meant to be limiting but merely serve to improve readability of the claims.

[0012] According to a first aspect of the invention, the problem is solved by a method of assessing the alignment of a femoral knee arthroplasty component in a patient with the features of claim 1. The method comprises the steps of: obtaining an orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of the femoral knee arthroplasty component; and obtaining an orientation of a projection, onto the coronal plane, of a spherical axis of a femur of the patient, which femur is provided with the femoral knee arthroplasty component. It is an achievable advantage of this aspect of the invention that a relationship of the orientations can be established. This aspect of the invention is based on the inventors’ finding that from said relationship, conclusions can be drawn as to the expected functioning of the femoral knee arthroplasty component.

[0013] In the context of the present invention, the “axis of the trochlear groove” of the femoral knee arthroplasty component is the axis that extends along the line of lowest points of the trochlear groove. If the line of lowest points of the trochlear groove extends along a curved line, the axis is the closest linear approximation to this curve.

[0014] In the context of the present invention, the “spherical axis” is an axis that passes through the centre of the femoral head and the centre of the medial condyle of the femur. For the purpose of determining the centres of the of femoral head and the medial condyle, these are preferably approximated by spheres, the centre of said spheres being considered the centres of the femoral head and the medial condyle, respectively. For determining the projection of the spherical axis onto a coronal plane, a line can be constructed that passes through the centres of circles approximating the projections of the femoral head and the medial condyle in said coronal plane.

[0015] This method can advantageously be used during surgery to intra-operatively predict, monitor and verify implant alignment during manual or computer-assisted surgery, in order to achieve a favorable orientation of the femoral components trochlear groove by either using manual surgical tools or instruments designed for this specific purpose, patient-specific instruments (PSI), a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI). Moreover, the method can be used advantageously after surgery to assess the post-operative alignment result achieved by the surgery.

[0016] In the context of the present invention, surgical navigation is a computer-assisted method to guide surgery using medical images, wherein a "surgical navigation system (SNS)" locates the position of surgical tools relative to an individual patients anatomical structure so as to guide the surgeon to perform surgical procedural steps accurately.

[0017] In the context of the present invention, "robotically assisted surgical equipment (RASE)" means medical electrical equipment which incorporates a programmable medical electrical equipment (PMEE) actuated mechanism, intended to facilitate the placement or manipulation of robotic surgical instrument (RSI). In the context of the present invention, a "robotic surgical instrument (RSI)" is an invasive device with an applied part, intended to be manipulated by robotically assisted surgical equipment (RASE) to perform tasks in a surgery.

[0018] In the context of the present invention, "programmable medical electrical equipment (PM EE)" is programmable medical electrical equipment with an applied part, which during normal use of the PM EE necessarily comes into physical contact with a patient to perform its function.

[0019] In the context of the present invention, the above named SNS, RASE, RSI and PMEE also include intelligent systems such as virtual reality, augmented reality and artificial intelligence.

[0020] According to a second aspect of the invention, the problem is solved by a method of planning the alignment of a femoral knee arthroplasty component in a patient with the features of claim 3. The method comprises the steps of: providing a simulation of a first femoral knee arthroplasty component, which simulation yields an orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of a first femoral knee arthroplasty component; and obtaining an orientation of a projection, onto the coronal plane, of the spherical axis of a femur of the patient. It is an achievable advantage of this aspect of the invention that the orientation of the projection of the axis of the simulated femoral knee arthroplasty component’s trochlear groove can be compared with the orientation of the projection of the spherical axis. As a result, in the simulation, said first femoral knee arthroplasty component can be brought into a favourable orientation. Advantageously, this orientation of the simulation of the first femoral knee arthroplasty component can be used when aligning in the patient a femoral knee arthroplasty component that is represented, in the simulation, by the simulated first femoral knee arthroplasty component.

[0021] In the present invention, the adjective “first” in “first femoral knee arthroplasty” is not meant to imply that there need to be more than one femoral knee arthroplasty component. If there is only one femoral knee arthroplasty component, the “femoral knee arthroplasty component” is this “first femoral knee arthroplasty component”. Yet, as disclosed further below, some preferred embodiments of the invention use two or more femoral knee arthroplasty components, in particular for selecting one of these as the femoral knee arthroplasty component to be implanted. According to a third aspect of the invention, the problem is solved by a method of planning the alignment of a femoral knee arthroplasty component in a patient with the features of claim 6. The method comprises the steps of: obtaining intrinsic geometrical data of each of two or more femoral knee arthroplasty components, the intrinsic geometrical data including at least the prosthetic trochlea orientation - preferably the prosthetic trochlea angle (PT A) - of the respective femoral knee arthroplasty component; obtaining an orientation of a projection, onto the coronal plane, of a spherical axis of a femur of the patient, which femur is to be provided with the femoral knee arthroplasty component; and choosing amongst the two or more femoral knee arthroplasty components a first femoral knee arthroplasty component by considering at least both the orientation of the projection of the spherical axis and the prosthetic trochlea orientations of the two or more femoral knee arthroplasty components. This aspect of the invention exploits the fact that the prosthetic trochlea orientation, together with the orientation of the femoral knee arthroplasty component, determines the functional orientation of the trochlear groove after implantation and that conclusions can be drawn as to the likely clinical outcome of the surgery, based on the relationship of the projections of the spherical angle and the trochlear groove onto the coronal plane.

[0022] In the context of the present invention, a “prosthetic trochlea orientation” of a femoral knee arthroplasty component is the orientation of the trochlear groove of the of femoral knee arthroplasty component relatively to the orientation of the femoral knee arthroplasty component itself.

[0023] According to a fourth aspect of the invention, the problem is solved by a method of monitoring an implanting of a femoral knee arthroplasty component in a patient with the features of claim 7. The method comprises the steps of obtaining an orientation of a resecting instrument or, the resecting instrument being for resecting the distal end of a femur of the patient, whose femur is provided with said femoral knee arthroplasty component; and obtaining a projection, onto the coronal plane, of an orientation of a spherical axis of the femur. It is an achievable advantage of this aspect of the invention that - if the appropriate intrinsic geometrical parameters of the femoral knee arthroplasty component are known - by predicting and monitoring the orientation of the resecting instrument, the orientation of the femoral resection plane can be inferred, and from this in turn, the orientation which said femoral knee arthroplasty component will have once it is affixed to the femur can be inferred. The invention is based on the inventors' finding that from a comparison of the orientation of the projection of the spherical axis with the orientation of the femoral knee arthroplasty component, conclusions can be drawn as to the expected functioning of the femoral knee arthroplasty component.

[0024] Advantageously, the results of the monitoring can be used for predicting the final position of the femoral arthroplasty component, which in turn can be used for predicting the clinical outcome of the femoral knee arthroplasty surgery.

[0025] According to a sixth aspect of the invention, the problem is solved by a method of operation of a SNS, RASE or RSI assisting an implanting of a femoral knee arthroplasty component in a patient with the features of claim 10, said method comprising the steps of the SNS, RASE or RSI orienting the femoral knee arthroplasty component, taking into consideration at least both an orientation of a projection, onto the coronal plane, of the spherical axis of patient's femur to be provided with the femoral knee arthroplasty component and an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component.

[0026] According to a seventh aspect of the invention, the problem is solved by a method of operation of a SNS, RASE or RSI assisting an implanting of a femoral knee arthroplasty component in a patient with the features of claim 11. Said method comprises the step of the SNS, RASE or RSI positioning a resecting instrument for resecting the distal end of a patient's femur to be provided with the femoral knee arthroplasty component, such that the distal femoral resection plane allows for the femoral knee arthroplasty component to be affixed to the patient's femur in a way that an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of said femoral knee arthroplasty component exhibits a greater or equal degree of valgus with respect to an orientation of a projection, onto a coronal plane, of a spherical axis of the femur.

[0027] According to an eighth aspect of the invention, the problem is solved by a method of implanting a femoral knee arthroplasty component in a patient with the features of claim 12, said method using any one of the methods recited above.

[0028] According to a ninth aspect of the invention, the problem is solved by a method of implanting a femoral knee arthroplasty component in a patient with the features of claim 13, said method comprising the step of affixing the femoral knee arthroplasty component to the patient's femur such that the orientation of a projection, onto a coronal plane, of the axis of a trochlear groove of the femoral knee arthroplasty component exhibits a greater degree of valgus with respect to or is- parallel to the orientation of a projection, onto a coronal plane, of a spherical axis of the femur.

[0029] In the context of the present invention, “valgus” means orientation of, relating to, or being an anatomical part or its respective projection turned outward, away from the midline in the coronal plane. More specifically, in the context of the present invention, of two projections of axes onto the coronal plane, the orientation of the first projection is “in-valgus” with regard to the orientation of the second projection, if the upper half-line of the first projection is oriented further from the midline than the upper half-line of the second projection. A projection's “upper half-line” is the half-line that extends from the intersection between the two projections in an upward direction. The “upward direction” is the general direction of a vector that extends from the patients feet towards the patients head. The “midline” is the intersection between the coronal plane and the sagittal plane. The expression “exhibit a greater degree of valgus” is synonymous with “in valgus”. If, conversely, the first projection’s upper half-line is oriented closer to the midline than the second projections upper half-line, this is referred to as a “lesser degree of valgus”. If the two projection are parallel to each other, this is referred to as an “equal degree of valgus”.

[0030] According to a tenth aspect of the invention, the problem is solved by a medical image analysis apparatus for assessing, based on at least one image of the patient's femur and a femoral knee arthroplasty component, the alignment of a femoral knee arthroplasty component with the features of claim 14. Said apparatus comprises: a trochlear groove gauge or image acquisition unit for obtaining from the image(s) an orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of the femoral knee arthroplasty component; and a spherical axis gauge or image acquisition unit for obtaining from the image(s) an orientation of a projection, onto the coronal plane, of the spherical axis a femur of the patient, whose femur has been provided with the femoral knee arthroplasty component.

[0031] In the context of the present invention, the term “apparatus” also encompasses apparatus with more than one, for example two, devices that cooperate to form the apparatus. Some or all of the devices can be physically separate from some or all other devices of the apparatus. Such device(s) may, for example, be selected from the following group of devices: an apparatus comprising an imaging device for acquiring one or more images of the patient’s femur, a computer for analysing the image(s), a computer for controlling a robot arm based on the analysis of the the image(s) and a robot arm for manipulating a femoral knee arthroplasty component, a resection instrument or a PSI resection guide, and a computer serving as a controller for controlling the computer ar based on the results of the analysis.

[0032] In the context of the present invention, reference is made to at least one image of the patient's femur and the femoral knee arthroplasty component. Said femur and said femoral knee arthroplasty component can be shown in the same image or on separate images.

[0033] According to an eleventh aspect of the invention, the problem is solved by a medical image analysis apparatus for planning, based on an image of the patient's femur to be provided with a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component in a patient with the features of claim 15. Said apparatus comprises: a simulator for providing a simulation of a first femoral knee arthroplasty component, such that said simulation yields an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of a first femoral knee arthroplasty component; and a spherical axis gauge or image acquisition unit for obtaining from the image an orientation of a projection, onto the coronal plane, of a spherical axis of the femur of the patient to be provided with said femoral arthroplasty component.

[0034] According to a twelfth aspect of the invention, the problem is solved by a medical image analysis apparatus for planning, based on an image of the patient's femur to be provided with a femoral knee arthroplasty component, an alignment of a femoral knee arthroplasty component in a patient with the features of claim 16. Said apparatus comprises: an intrinsic geometrical data acquisition unit for obtaining intrinsic geometrical data of each of two or more femoral knee arthroplasty components, the intrinsic geometrical data including at least the prosthetic trochlea orientation of the respective femoral knee arthroplasty component; a spherical axis gauge or image acquisition unit for obtaining from the image an orientation of a projection, onto the coronal plane, of a spherical axis of the femur; and a component selector or selection algotithm for choosing amongst the two or more femoral knee arthroplasty components a first femoral knee arthroplasty component by considering at least both the orientation of projection of the spherical axis and the prosthetic trochlea orientations of the two or more femoral knee arthroplasty components. According to a thirteenth aspect of the invention, the problem is solved by a medical image analysis apparatus for planning, based on an image of the patient's femur to be provided with a femoral knee arthroplasty component, an implantating of a femoral knee arthroplasty component in a patient with the features of claim 17. Said apparatus comprising: a resecting instrument orientation gauge for obtaining an orientation of a resecting instrument for resecting the distal end of the femur; and a spherical axis gauge for obtaining from the image an orientation of a projection, onto the coronal plane, of a spherical axis of the femur of the patient.

[0035] The present invention also includes embodiments of the image analysis apparatus as part of a medical imaging apparatus-, such a digital x-ray-, CT-, MRI-, or nuclear imaging apparatus or PACS system, a medical CAD / CAM apparatus or system, such as a medical device milling, shaping or casting machine or medical 3D-printer, and a SNS, RASE or RSI .

[0036] In particular, according to a fourteenth aspect of the invention, the problem is solved by a medical imaging apparatus, SNS, RASE or RSI for assisting an implanting of a femoral knee arthroplasty component in a patient with the features of claim 18, said medical imaging apparatusthe robot comprising the medical image analysis apparatus according to any one of apparatus of claims 14 to 17.

[0037] According to a fifteenth aspect of the invention, the problem is solved by a RASE or RSI for assisting an implanting of a femoral knee arthroplasty component in a patient with the features of claim 19, said RASE or RSI comprising: a manipulator for orienting the femoral knee arthroplasty component; and a control unit for operating the manipulator to orient the femoral knee arthroplasty component by considering at least both an orientation of a projection, onto the coronal plane, of a spherical axis of the patient's femur to be provided with the femoral knee arthroplasty component and an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component.

[0038] According to a sixteeth aspect of the invention, the problem is solved by a RASE or RSI for assisting an implanting of a femoral knee arthroplasty component in a patient with the features of claim 20, said robot comprising: a manipulator for orienting a resecting instrument for resecting the distal end of the patient's femur to be provided with the femoral knee arthroplasty component; and a control unit for operating the manipulator to orient the resecting instrument such that the distal femoral resection plane allows for the femoral knee arthroplasty component to be affixed to the patient's femur in a way that an orientation of a projection, onto a coronal plane, of the axis of the trochlear groove of the femoral knee arthroplasty component exhibits an equal or greater degree of valgus with respect to the orientation of the projection, onto a coronal plane, of the spherical axis.

[0039] According to a seventeenth aspect of the invention, the problem is solved by a computer program product adapted to cause, when executed on a computer, the computer comprising a processor and a memory, one or more of the abore-mentioned methods.

[0040] The methods, apparatus and computer program product of the present invention can be used for the manufacture of a PSI-resection guide. For example, based on the simulation of the first femoral knee arthroplasty component and the orientation of the projection onto the coronal plane, of a spherical axis of a femur (1) of the patient provided and obtained, respectively, in the method according to claim 3, a PCI-resection guide can be manufactured. PCI resection guides and methods of manufacturing a PCI resection guide ar for example known from Vicente J Leon-Munoz et als publication “Patient-Specific Instrumentation Accuracy Evaluated with 3D Virtual Models”, J Clin Med 2021, 10, 1439. htps: / / doi.org / 10.3390 / icm10071439, in particular with regard to MyKnee ™ patient-specific TKA instrumentation (Medacta International SA, Castel San Pietro, Switzerland) discussed on page 2 of the publication. The relevant part of the publication are incorporated into this application by reference.

[0041] In the context of the present invention, a "PSI-resection guide" is a form of patient specific instrumentation based on preoperative planning by imaging in an individual patient, with the sole aim to enhance surgical accuracy of the resection plane it has been designed to provide. A suitable PSI resection guide is for example the MyKnee Efficiency PSI known from Medacta International S.A,, Switzerland. The preferred PSI resection guide is produced by 3D-printing.

[0042] According to a fifth aspect of the invention, the problem is solved by a method of a surgical navigation system (SNS), a robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component in a patient according to claim 9. The method comprises the features of claim 1. With this aspect of the invention, it is advantageously achievable that the SNS, RASE or RSI can consider the orientations of the projections when assisting the implanting of the femoral knee arthroplasty component in the most favorable alignment.

[0043] The present invention also encompasses any combination of the above-described aspects of the invention.

[0044] Preferred embodiments of the invention

[0045] Preferred features of the invention which may be applied alone or in combination are discussed in the following and in the dependent claims.

[0046] The apparatus according to the present invention can perform one or more of the methods according to the invention. Likewise, the apparatus is provided with devices to perform steps of the methods of the invention described herein. The preferred apparatus comprises a computer memory and a processor, for example a memory and a processor as can be used in a conventional computing devices such as a desktop or mobile computer, a tablet computer or a mobile phone. Preferably, one or more, more preferably all, of the components of the apparatus, such as the trochlear groove gauge, the spherical axis gauge, the simulator, the comparator, the alignment gauge and the control unit are realised as software components held in the memory and executed on the processor.

[0047] Similarly, the preferred SNS, RASE or RSI comprise a computer memory and a processor.

[0048] The memory preferably includes an image memory for holding more images of the patients femur and / or the femoral knee arthroplasty component. The memory preferably includes a geometrical data memory for holding intrinsic geometrical data of one or more femoral knee arthroplasty components.

[0049] The orientations of the projections of the spherical axis and / or the axis of the trochlear groove onto the coronal plane are preferably obtained from one or more images of the patient's femur and / or the femoral knee arthroplasty component, preferably images that project these onto the coronal plane. The femur and the femoral knee arthroplasty component can be shown in the same image or on separate images. A preferred image is an x-ray image, which can for example be obtained with a FXR MultiSuite 50165180 kW) manufactured by (Fujifilm, Japan).

[0050] Yet, the present invention can also be practiced with other types of images, for example ultrasound images and images obtained by nuclear magnetic resonance imaging, which can for example be obtained with a Signa™ Voyager MRI-System manufactured by GE Healthcare, or computed tomography, which can for example be obtained with a Revolution Frontier CT-System manufactured by GE Healthcare

[0051] The preferred apparatus of the present invention is provided with an image display, which can for example be a computer screen, a virtual reality headset or an augmented reality headset. Preferably, the image display presents to at least one, preferably more than one human operator(s) of the apparatus at least part of one or more of the images. Preferably, the image display presents to at least one, preferably more than one operator(s) of the apparatus representations of at least one of the projections of the spherical axis and the axis of the trochlear groove onto the coronal plane, more preferably both. It is particularly preferred that the representation(s) of the projection(s) is / are superimposed onto the image(s) of the femur and / or the femoral knee arthroplasty component. A representation may for example be realised by means of line drawn on the image display, the orientation of the line representing the orientation of the projection of the spherical axis or the axis of the trochlear groove.

[0052] A preferred method according to the present invention comprises the step of obtaining a projection, onto a coronal plane, of an orientation of an axis of a trochlear groove of the femoral knee arthroplasty component. Correspondingly, a preferred apparatus according to the invention is provided with a trochlear groove gauge for obtaining from the image(s) an orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of the femoral knee arthroplasty component. The inventors have found that the orientation of this axis is of considerable importance for the proper functioning of the knee. In particular, according to the inventors' findings, if the projection, onto the coronal plane, of the axis of a trochlear groove extends too far into valgus, this can result into an inferior clinical outcome, for example reduced mobility for the patient. A preferred method according to the present invention comprises the step of obtaining an orientation of a projection, onto the coronal plane, of a spherical axis of a femur of the patient, which femur is provided with the femoral knee arthroplasty component. Correspondingly, a preferred apparatus according to the invention is provided with a spherical axis gauge for obtaining from the image(s) an orientation of a projection, onto the coronal plane, of a spherical axis of a femur of the patient, which femur is provided with the femoral knee arthroplasty component. The inventors have found that the orientation of the spherical axis can provide guidance as to a favourable orientation of the trochlear groove. In particular, according to the inventors' findings, the orientation of the projection of the spherical axis onto the coronal plane can provide guidance as to how far into valgus the trochlear groove should extend in order to avoid an inferior clinical outcome such as reduced mobility for the patient.

[0053] The invention incudes embodiments in which the orientation of the projection of the axis of the trochlear groove is obtained manually by an operator as well as embodiments in which it is obtained automatically. Likewise, The invention incudes embodiments in which the orientation of the projection of the spherical axis is obtained manually by an operator as well as embodiments in which it is obtained automatically.

[0054] For manually obtaining such orientation, the operator provides the orientation of the projection, preferably by inputting it into the apparatus, for example by drawing the representation of the projection of the trochlear grove and / or the spherical axis onto the image display, preferably superimposed onto an image of the trochlear groove. For this purpose, the apparatus preferably is provided with a human interface device such as a touch screen, a mouse, a joystick or a track ball. Moreover, the preferred apparatus is provided with a drawing software that allows the operator to draw the representation onto the image display by means of the human interface device. Suitable drawing software is, for example, known from JiveX Review 5.3.0.25 manufactured by Visus Health IT GmbH, Germany, where it is used for the purpose of viewing and measuring medical image data for clinical, research or educational purposes. A skilled person can readily adapt the software to be suitable the purposes of the present invention.

[0055] Preferably, for assisting the operator to find the centres of the femoral head and the medial condyle, the drawing software is provided with a circle tool that allows approximating the images of the femoral head and the medial condyle with circles and draws or assists the operator in drawing a line through the centres of these circles.

[0056] Preferably, for assisting the operator to find the orientation of the projection of the trochlear groove, a representation, for example in the form of a line drawing, of the femoral knee arthroplasty component is displayed in the image display, and the operator can, by means of moving and orienting this representation using the human interface device, superimpose the representation onto the image of the femoral knee arthroplasty component. Preferably, intrinsic geometrical data, preferably including in particular the prosthetic trochlea orientation, is provided to the apparatus so that the orientation of the projection of the trochlear grooved can be obtained. Preferably, this orientation is indicated on the image display, for example by means of a line drawn of the display.

[0057] For automatically obtaining the orientation of the projection of the axis of the trochlear groove, use is made of image recognition software suitable to recognise the femoral knee arthroplasty component and its orientation. Suitable image recognition software is known from IB Lab LAMA™ manufactured by IB Lab GmbH, Vienna Austria, where it is used for the purpose of digitizing musculoskeletal (MSK) diagnostic parameters on radiographs, providing quantitative and standardized reporting). A skilled person can readily adapt the software to be suitable the purposes of the present invention. From the orientation of the femoral knee arthroplasty component, the orientation of the femoral groove can be obtained. For this purpose, intrinsic geometrical data is provided that at least comprises the prosthetic trochlea orientation.

[0058] Similarly, for automatically obtaining the orientation of the projection of the spherical axis, use is made of image recognition software suitable to recognise the femoral head and the medial condyle in the image. Suitable image recognition software is known from IB Lab LAMA™ manufactured by IB Lab GmbH, Vienna Austria, where it is used for the purpose of digitizing musculoskeletal (MSK) diagnostic parameters on radiographs, providing quantitative and standardized reporting). The projections, onto the coronal plane, of the femoral head and the medial condyle are preferably approximated by circles and the projection of the spherical axis is considered to be the axis that passes through the centres of these circles. The preferred method according to the present invention comprises a step of comparing an orientation of the projection, onto the coronal plane, of the axis of the trochlear groove with an orientation of the projection, onto the coronal plane, of the spherical axis.

[0059] Correspondingly, the preferred apparatus is provided with a comparator for comparing the orientations of the projection of the axis of the trochlear groove with an orientation of the projection of the spherical axiSr The inventors have found that, in particular, the relative orientations of these two projection provides guidance as to a potentially unfavourable result of the surgery.

[0060] In particular, the inventors have found that if the orientation of the projection, onto the coronal plane, of the axis of the trochlear groove exhibits a lesser degree of valgus with respect to the orientation of the projection, onto the coronal plane, of the spherical axis, this may compromise mobility of the patient. The inventors consider such situation a Functional Trochlear Malalignment (FTMA). Moreover, the inventors have found that a situation in which the orientation of the projection, onto the coronal plane, of the axis of the trochlear groove exhibits an equal degree of valgus with respect to the orientation of the projection, onto the coronal plane can be particularly favourable.

[0061] Thus, in one embodiment the method comprises a step of determining, based on the result of the comparing the orientation of the axis of the trochlear groove with the orientation of the projection of the spherical axis, at least one of (a) whether or not the orientation of the projection of the axis of the trochlear groove exhibits a lesser degree of valgus, (b) whether the orientation of said projection of the axis of the trochlear groove exhibits an equal degree of valgus or (c) whether the orientation of said projection of the axis of the trochlear groove exhibits a greater degree of valgus with respect to the orientation of the projection of the spherical axis. In the preferred apparatus, this is determined in the comparator, ie, the comparator of the apparatus determines, based on the result of the comparing, at least one of (a) whether the orientation of the projection of the axis of the trochlear groove exhibits a lesser degree of valgus, (b) whether the orientation of the projection of the axis of the trochlear groove exhibits an equal degree of valgus or (c) ) whether the orientation of the projection of the axis of the trochlear groove exhibits a greater degree of valgus with respect to the orientation of the projection of the spherical axis. This step preferably constitutes the determining the presence or absence of FTMA. Alternatively or in addition, a preferred method of the of invention comprises a step of determining, based on the result of the comparing the orientation of the axis of the trochlear groove with the orientation of the projection of the spherical axis, a valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis. In the preferred apparatus, this is determined in the comparator.

[0062] In the context of the present invention, the absolute value of the “valgus angle” of a first projection of an axis onto the coronal plane with respect to a second projection of an axis onto the coronal plane is the angle between these projections at their intersection. The sign of the valgus angle is positive, if the first projection is “in valgus” with regard to the second projection, ie, if the proximal half-line of the first projection is further from the sagittal plane than the proximal half-line of the second projection is. The sign of the valgus angle is negative, if the first projection-exhibits a lesser degree of valgus with regard to the second projection.

[0063] More preferably, the method comprises a step of determining, typically in the apparatus’ comparator, whether the valgus angle is equal or more than 0, preferably more than 1 , even more preferably more than 2 degrees (one degree being the 360th of a full circle).

[0064] Similarly, the method more preferably comprises a step of determining, typically in the apparatus’ comparator, whether the valgus angle is less than 9, preferably less than 5, preferably less than 3 degrees (one degree being the 360th of a full circle).

[0065] The results of the determining steps described above preferably are provided to the operator(s), for example on a display, particularly preferably on the image display.

[0066] A preferred method of planning an alignment of a femoral knee arthroplasty component in a patient comprises the steps of providing a simulation of a first femoral knee arthroplasty component. The preferred apparatus comprises a simulator for providing a simulation of a first femoral knee arthroplasty component. Preferably, the first femoral knee arthroplasty component is simulated to be affixed to the patient’s femur.

[0067] In the context of the present invention, providing a “simulation” refers to providing geometrical parameters of a first femoral knee arthroplasty component that is not actually present in the patient. The simulated first femoral knee arthroplasty component, therefore, for example is not present on images of the patient’s femur. The geometrical properties preferably comprise at least an orientation of the simulated first femoral knee arthroplasty.

[0068] The simulation preferably yields an orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of a first femoral knee arthroplasty component. In addition, the preferred method comprises the step of obtaining an orientation of a projection, onto the coronal plane, of a spherical axis of the patient’s femur. A preferred apparatus comprises a spherical axis gauge for obtaining this orientation.

[0069] The orientation of the axis of a trochlear groove of a first femoral knee arthroplasty component can, for example, be derived from the prosthetic trochlea orientation of the first femoral knee arthroplasty component. In a preferred method intrinsic geometrical data of the femoral knee arthroplasty components is provided that includes the prosthetic trochlea orientation.

[0070] It is preferred that the image display presents a representation of the simulated first femoral knee arthroplasty component to at least one, preferably more than one operator(s) of the apparatus. Preferably, the representation of the simulated first femoral knee arthroplasty component comprises at least a representation of its femoral groove. Preferably, the representation of the simulated first femoral knee arthroplasty component is superimposed onto the image(s) of the femur of the patent. The representation of the femoral groove may for example be realised by means of line drawn on the image display, the orientation of the line representing the orientation of the projection of the axis of the trochlear groove.

[0071] Preferably, an orientation of the projection, onto the coronal plane, of the axis of the trochlear groove of the simulated first femoral knee arthroplasty component is compared with an orientation of the projection, onto the coronal plane, of the spherical axis. More preferably, based on the result of the comparing it is determined whether or not the orientation of the projection of the axis of the trochlear groove exhibits a lesser degree of valgus with respect to the orientation of the projection of the spherical axis. Alternatively or in addition, based on the result of the comparing a valgus angle of the projection of the axis of the simulated first trochlear groove with respect to the projection of the spherical axis is determined.

[0072] Advantageously, based on the result of the above comparing, more preferably comparing and determining, the simulated first femoral knee arthroplasty component can be oriented to provide for a desired functioning of the femoral knee arthroplasty component. The invention incudes embodiments in which the orienting is performed manually by an operator as well as embodiments in which it is performed automatically.

[0073] For manually orienting the simulated first femoral knee arthroplasty component, the operator provides the orientation, preferably by inputting it into the apparatus, for example by manipulating a representation of the simulated first femoral knee arthroplasty component on the image display, preferably superimposed onto an image of a representation of the projection of the spherical axis onto the coronal plane and / or an image of the patient’s femur. For this purpose, the simulator preferably is provided with a human interface device such as a touch screen, a mouse, a joystick or a track ball. Moreover, the simulator is provided with a drawing software that allows the manipulation of the representation of the simulated first femoral knee arthroplasty component by means of the human interface device. Suitable drawing software is, for example, known from mediCAD® 2D Version 7.0 manufactured by mediCAD Hectec GmbH, Germany, where it is used for the purpose of digital visualization, preoperative templating and surgical planning of bone and joint deformities, joint-replacing implants, osteotomies and other orthopaedic surgical procedures based on 2D medical images and 3D models. A skilled person can readily adapt the software to be suitable the purposes of the present invention. Preferably, during and / or at the end of the manipulation, the results of the determining steps described above are provided to the operator(s), for example on a display, particularly preferably on the image display.

[0074] A preferred method comprises the steps of calculating an orientation of the simulated first femoral knee arthroplasty components relatively to the patient's femur such that an orientation of the projection, onto a coronal plane, of the axis of its trochlear groove exhibits an equal or greater degree of valgus with respect to the orientation of the projection, onto a coronal plane, of the spherical axis. This step serves to avoid FTMA.

[0075] Alternatively, or in addition, a preferred method comprises the steps of calculating an orientation of the simulated first femoral knee arthroplasty component where the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis has a pre-determined minimum value, which value preferably is equal or more than 0, preferably more than 1 , even more preferably more than 2 degrees. Similarly, a preferred method comprises the steps of calculation an orientation of the simulated first femoral knee arthroplasty component where the valgus angle has a pre-determined maximum value, which value preferably is less than 9, preferably less than 5, preferably less than 3 degrees. Preferably, in the method for manually orienting the simulated first femoral knee arthroplasty component, a representation of the simulated first femoral knee arthroplasty component in one of more orientations calculated as describe above is displayed on the image display for the operators’ information.

[0076] A preferred apparatus comprises an alignment gauge for performing one or more of the calculating steps recited above are performed in an alignment gauge auf the apparatus.

[0077] For automatically orienting the simulated first femoral knee arthroplasty component, the simulated first femoral knee arthroplasty component preferably is oriented in a predetermined orientation based on orientations calculated as above. For example, the predetermined orientation is one of the orientations calculated as defined above, or it is at a valgus angle that is the mean value of the minimum and the maximum orientation as defined above.

[0078] A preferred method of planning an alignment of a femoral knee arthroplasty component in a patient comprises the step of calculating a distal femoral resection plane for affixing to the patient's femur a femoral knee arthroplasty component of the kind of the simulated first femoral knee arthroplasty component in the orientation of the simulated first femoral knee arthroplasty component. For example, the orientation of the distal femoral resection plane can be provided relatively to the axis of the distal femoral shaft.

[0079] The preferred apparatus comprises an alignment gauge for performing the above-described calculating steps.

[0080] Preferably, intrinsic geometrical data of the first femoral knee arthroplasty component is provided that contains the orientation of the distal femoral resection plane relatively to the orientation of the first femoral knee arthroplasty component.

[0081] The result of the calculation preferably is provided to the operator(s), for example on a display, particularly preferably on the image display. In addition or alternatively, it may be provided to a SNS, such as the OrthoPilot ® Navigationsystem FS101 (Software 5.1) manufactured by Aesculap AG, Tuttlingen, Germany, where the realtime information aand feedback on implant and instrument positions during surgery is monitored, or a sa medical robot comprising RASE or RSI according to the present invention for assisting the implanting of a femoral knee arthroplasty component in a patient, such as the Mako®, manufactured by Stryker, Mahwah, NJ, USA, where the manipulator is used for the purpose of using the semi-automated haptic Stryker MAKO ® robotic system or the CORI ®, manufactured by (Smith&Nephew™, USA) where the robot works in conjunction with the robotics-assisted handpiece.

[0082] A preferred method of planning an alignment of a femoral knee arthroplasty component in a patient comprises the step of choosing amongst the two or more femoral knee arthroplasty components a first femoral knee arthroplasty component by considering at least both the orientation of the projection, onto the coronal plane, of the spherical axis and the prosthetic trochlea orientations of the two or more femoral knee arthroplasty components. Accordingly, a preferred medical image analysis apparatus comprises an intrinsic geometrical data acquisition unit for obtaining intrinsic geometrical data of each of two or more femoral knee arthroplasty components, the intrinsic geometrical data including at least the prosthetic trochlea orientation of the respective femoral knee arthroplasty component. From the prosthetic trochlear orientation and the orientation of the femoral knee arthroplasty component the orientation of the trochlear groove of the femoral knee arthroplasty component can be calculated. In a preferred method intrinsic geometrical data of the femoral knee arthroplasty components is provided that includes the prosthetic trochlea orientation.

[0083] Typically, a femoral knee arthroplasty component is intended to be affixed to the patient’s femur in in a pre-determined range of orientations. The range may be determined by the desired bending axis of the knee after implantation. The manufacturer of the femoral knee arthroplasty component my recommend a range of suitable orientations, or such recommendation can be found in the literature such as a scientific publication or an official guideline. The range can for example be provided as a range of orientations of the femoral knee arthroplasty component relatively to the axis of the distal femoral shaft. The range can be narrow or broad. In a preferred method intrinsic geometrical data of the femoral knee arthroplasty components is provided that includes the ranges.

[0084] Accordingly, in a preferred method, a first femoral knee arthroplasty component is chosen for which at least one orientation of the first femoral knee arthroplasty component relatively to the patient femur exist that is (a) within the pre-determined range of orientations relatively to the patient femur and in which (b) the orientation of the projection, onto the coronal plane, of its trochlear groove - as calculated from the prosthetic trochlea orientation exhibits an equal or greater degree of valgus with respect to the orientation of the projection, onto a coronal plane, of the spherical axis. Step (b) serves to avoid FTMA.

[0085] Alternatively, or in addition to criterion (b) above, the criterion is applied that (c) the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis is equal to or greater than a pre-determined minimum value, which value preferably is equal or more than 0, preferably more than 1 , even more preferably more than 2 degrees. Similarly, alternatively or in addition to criteria (b) and / or (c) above, the criterion is applied that (d) the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis is equal to or smaller than a pre-determined maximum value, which value preferably is less than 9, preferably less than 5, preferably less than 3 degrees (one degree being the 360th of a full circle).

[0086] A preferred method of monitoring the implanting of a femoral knee arthroplasty component in a patient comprises the steps of obtaining an orientation of a resecting instrument, the resecting instrument or the resection guide being for resecting the distal end of the femur. Accordingly, a preferred medical image analysis apparatus comprises a resecting instrument orientation gauge for obtaining an orientation of a resecting instrument for resecting the distal end of the femur of the patient, which femur (1) is to be provided with said femoral knee arthroplasty component (2). Thereby, a surgeon can be assisted in correctly resecting the femur, or a medical robot can be controlled to perform the resection or to assist the surgeon in doing so. The orientation of the resecting instrument can for example be obtained as known from the OrthoPilot ® Navigationsystem FS101 (Software 5.1) manufactured by Aesculap AG, Tuttlingen, Germany, where the where the orientation of a surgical resection instrument (resection block) is monitored during surgery. A skilled person can readily adapt the software to be suitable the purposes of the present invention.

[0087] Preferably, from the orientation of a resecting instrument the orientation of the distal femoral resection plane is calculated. For this purpose, preferably, intrinsic geometrical data of the resecting instrument is provided that indicates the orientation of the distal femoral resection plane it can produce relatively to the resecting instrument’s orientation. A preferred apparatus is provided with an alignment gauge for calculating the orientation of the distal femoral resection plane from the orientation of a resecting instrument. Preferably, based on the orientation of the distal femoral resection plane, an orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of a first femoral knee arthroplasty component is calculated. For this purpose, preferably, intrinsic geometrical data of the first femoral knee arthroplasty component is provided that includes the prosthetic trochlea orientation. A preferred apparatus is provided with an alignment gauge for calculating, based on the orientation distal femoral resection plane, the orientation of a projection, onto a coronal plane, of an axis of a trochlear groove of a first femoral knee arthroplasty component is calculated.

[0088] Preferably, the orientation of the projection of the axis of the trochlear groove thus obtained is compared with an orientation of the projection of the spherical axis. Based on this comparison, determinations can be made as previously discussed. In particular, it preferably is determined at least one of (a) whether the orientation of the projection of the axis of the trochlear groove exhibits a lesser degree of valgus, (b) whether the orientation of the projection of the axis of the trochlear groove exhibits an equal degree of valgus or (c) whether the orientation of the projection of the axis of the trochlear groove exhibits a greater degree of valgus with respect to the orientation of the of the projection of the spherical axis. Thus the presence or absence of FTMA is determined.

[0089] Alternatively, or in addition it is preferably determined, typically in the apparatus’ comparator, whether the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis is equal or more than 0, preferably more than 1, even more preferably more than 2 degrees. Similarly, it is preferably determined, typically in the apparatus’ comparator, whether the valgus angle is less than 9, preferably less than 5, preferably less than 3 degrees.

[0090] A preferred apparatus is provided with a comparator for performing one or more of the above-cited comparing steps.

[0091] In a preferred method of operation of a robot assisting an implanting of a femoral knee arthroplasty component in a patient, the robot orients the femoral knee arthroplasty component. For this purpose, the robot preferably is provided with a manipulator that can hold and orient the femoral knee arthroplasty component. A suitable manipulator is for example known from Mako®, manufactured by Stryker, Mahwah, NJ, USA, where the manipulator is used for the purpose of using the semi-automated haptic Stryker MAKO® robotic system. Moreover, the robot is provided with a control unit of operating the manipulator in order to orient the femoral knee arthroplasty component.

[0092] In orienting the femoral knee arthroplasty component, preferably an orientation of a projection, onto the coronal plane, of a spherical axis of the patient's femur to be provided with the femoral knee arthroplasty component, and an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component are considered. These are preferably obtained as discussed before.

[0093] In a preferred method, the robot orients the femoral knee arthroplasty component relatively to the patient's femur such that an orientation of the projection, onto a coronal plane, of the axis of its trochlear groove exhibits an equal or greater degree of valgus with respect to the orientation of the projection, onto a coronal plane, of the spherical axis. This serves to avoid FTMA.

[0094] Alternatively or in addition, the robot preferably orients the femoral knee arthroplasty component relatively to the patient's femur such that the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis has a predetermined minimum value, which value preferably is equal to or more than 0, preferably more than 1 , even more preferably more than 2 degrees (one degree being the 360th of a full circle). Similarly, the robot preferably orients the femoral knee arthroplasty component relatively to the patient's femur such that the valgus angle has a pre-determined maximum value, which value preferably is less than 9, preferably less than 5, preferably less than 3 degrees.

[0095] In a preferred method of operation of a robot assisting the implanting of a femoral knee arthroplasty component in a patient, the robot positions a resecting instrument for resecting the distal end of the patient's femur to be provided with the femoral knee arthroplasty component. For this purpose, the robot preferably is provided with a manipulator that can hold and orient the resecting instrument. A suitable manipulator is for example known from Mako®, manufactured by Stryker, Mahwah, NJ, USA, where the manipulator is used for the purpose of using the semi-automated haptic Stryker MAKO® robotic system. Moreover, the robot is provided with a control unit of operating the manipulator in order to orient the resection instrument. The robot preferably orients the resecting instrument relatively to the patient's femur such that the distal femoral resection plane allows for the femoral knee arthroplasty component to be affixed to the patient's femur in a way that an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component exhibits an equal or greater degree of valgus with respect to an orientation of a projection, onto a coronal plane, of a spherical axis of the femur. This serves to avoid FTMA.

[0096] Alternatively, or in addition, the robot preferably orients the resection instrument relatively to the patient's femur such that the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis has a pre-determined minimum value, which value preferably is equal to or more than 0, preferably more than 1 , even more preferably more than 2 degrees. Similarly, the robot preferably orients the resection instrument relatively to the patient's femur such that the valgus angle has a pre-determined maximum value, which value preferably is less than 9, preferably less than 5, preferably less than 3 degrees.

[0097] The preferred robot calculates the orientation of the resecting instrument from a desired resection plane for affixing to the patient's femur a femoral knee arthroplasty component. The orientation of the distal femoral resection plane can be provided for example relatively to the axis of the distal femoral shaft. For this purpose, preferably, intrinsic geometrical data of the resecting instrument is provided that indicates the orientation of the distal femoral resection plane it can produce relatively to the resecting instrument’s orientation.

[0098] The desired resection plane, in turn, preferably is calculated from the desired orientation of the femoral knee arthroplasty component. For this purpose, preferably, intrinsic geometrical data of the femoral knee arthroplasty component is provided that contains the orientation of the distal femoral resection plane relatively to the orientation of the femoral knee arthroplasty component.

[0099] The desired orientation of the femoral knee arthroplasty component, in turn, preferably is calculated from the orientation of the axis of the femoral groove that fulfils the above criteria with regard to the orientation of the projection, onto the coronal plane, of the axis of the femoral groove. For this purpose, preferably, intrinsic geometrical data of the first femoral knee arthroplasty component is provided that includes the prosthetic trochlea orientation. In a preferred method of implanting a femoral knee arthroplasty component in a patient, the femoral knee arthroplasty component is affixed to the patient's femur such that an orientation of a projection, onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component exhibits a greater degree of valgus or with respect to or, more preferably, is parallel to an orientation of a projection, onto a coronal plane, of a spherical axis of the femur. This serves to avoid FTMA.

[0100] Preferably, the femoral knee arthroplasty component is affixed to the patient's femur such that the valgus angle of the projection of the axis of the trochlear groove with respect to the projection of the spherical axis has a pre-determined minimum value, which value preferably is equal to or more than 0, preferably more than 1 , even more preferably more than 2 degrees. Similarly, the femoral knee arthroplasty component preferably is affixed to the patient's femur such that such that the lateral angle has a pre-determined maximum value, which value preferably is less than 9, preferably less than 5, preferably less than 3 degrees.

[0101] Brief description of the drawings

[0102] In the following, further preferred embodiments of invention are illustrated by means of examples. The invention is not limited to these examples, however.

[0103] The drawings schematically show:

[0104] Figure 1 a projection, onto the coronal plane of a section of the spherical axis of a patient’s right femur superimposed on an image of said femur;

[0105] Figure 2 a femoral knee arthroplasty component;

[0106] Figure 3 a case of Functional Trochlea Malalignment (FTMA);

[0107] Figure 4 a case in which FTMA is avoided;

[0108] Figure 5 the effect of avoiding FTMA in terms of the Forgotten Joint Score (FJS); and Figure 6 the effect of avoiding FTMA in terms of the Knee injury and Osteoarthritis Outcome Score (KOOS).

[0109] Detailed description of an embodiment of the invention

[0110] In the following description of preferred embodiments of the invention, identical reference numerals refer to identical or similar components.

[0111] Figure 1, is an x-ray image in the coronal plane of a patient’s right femur 1. The x-ray image also shows a femoral knee arthroplasty component 2 affixed to the distal end of the femur 1. The projections, onto the coronal axis, of the femoral head and the medial condyle are approximated by circles 3, 4 superimposed on the x-ray image. In order to obtain the orientation of the projection, onto the coronal plane, of the spherical axis, a section 5 (full line) of such projection is drawn by connecting the centres of these circles 3, 4. The orientation of the projection of the spherical axis is the orientation of this section 5.

[0112] Figure 2 shows the femoral knee arthroplasty component 2 for the right femur. The projection, onto the coronal plane, of the axis of the femoral groove 6 is shown as a dotted line. For orientation, the figure also shows the base line 7 of the component (full line) and a vertical 8 (dashed line) on the base line 7, both in the coronal plane. The projection of the axis of the femoral groove 6 is oriented in valgus with regard to the vertical 8 on the base line 7.

[0113] Figure 3 shows the situation of a Femoral Trochlear Malalignment (FTMA). Onto an x-ray image in the coronal plane of a patient’s right femur 1 and a femoral knee arthroplasty component 2 affixed to the distal end of the femur 1, the projections, onto this coronal plane, of the axis of the femoral grove 9 (dotted line) and the spherical axis 10 (full line) are superimposed. The upper half-lines 11 , 12 of the projections extend generally upwards from the intersection 13 of the two projections. The upper half line 11 of the projection of the axis of the femoral grove is closer the sagittal plane (on the right of the figure, not shown) than the upper half line of the projection of the spherical axis 12. Thus, the projection 9 of the axis of the femoral grove exhibits a lesser degree of valgus with regard to the projection 10 of the spherical axis. Also, as a result, the valgus angle 14 of the projection 9 of the axis of the femoral grove with regard to the projection 10 of the spherical axis is negative. In contrast, Figure 4 shows the situation in which a Femoral Trochlear Malalignment (FTMA) is avoided. As in Figure 3, onto an x-ray image in the coronal plane of a patient’s right femur 1 and a femoral knee arthroplasty component 2 affixed to the distal end of the femur 1, the projections, onto this coronal plane, of the axis of the femoral grove 9 (dotted line) and the spherical axis 10 (full line) are superimposed. Unlike in Figure 3, in Figure 4 the upper half line 11 of the projection of the axis of the femoral grove is further form the sagittal plane (on the right of the figure, not shown) than the upper half line 12 of the projection of the spherical axis. Thus, the projection9 of the axis of the femoral grove is in valgus with regard to the projection 10 of the spherical axis. Also as a result, the valgus angle 14 of the projection 9 of the axis of the femoral grove with regard to the projection 10 of the spherical axis is positive.

[0114] The chart of Figure 5 shows the result of an analysis of the Forgotten Joint Score (FJS) questionnaire of a total of 206 patients that underwent femoral knee arthroplasty surgery, with 73 diagnosed to have FTMA and the remaining 133 diagnosed to have no FTMA. In the chart, the distribution of FJS results in patients with FTMA (dashed line) is compared with that of patients without FTMA (full line). The analysis shows that on average, patients without FTMA achieve a significantly higher score than patients with FTMA, which suggests a better clinical outcome. In particular, in the cohort without FTMA, there is a considerable higher number of patients with excellent FJS results of 80 and above (see crosshatched area).

[0115] Similarly, the chart of Figure 6 shows the result of an analysis of Knee injury and Osteoarthritis Outcome Score (KOOS) of the same 206 patients. Again, in the chart the distribution of KOOS results in patients with FTMA is compared with that of patients without FTMA. The analysis shows that on average, patients without FTMA achieve a significantly higher score than patients with FTMA, which is another indication of a better clinical outcome and that in the cohort without FTMA, there is again a considerable higher number of patients with excellent KOOS results of 80 and above (see crosshatched area).

[0116] The features as described in the above description, claims and figures can be relevant individually or in any combination to realise the various embodiments of the invention.

Claims

Claims1. A method of assessing an alignment of a femoral knee arthroplasty component (2) in a patient, said method comprising the steps of: obtaining an orientation of a projection (9), onto a coronal plane, of an axis of a trochlear groove of a femoral knee arthroplasty component (2); and obtaining an orientation of a projection (10), onto the coronal plane, of a spherical axis of a femur (1) of the patient, which femur (1) is provided with said femoral knee arthroplasty component (2).

2. The method of claim 1 further comprising the steps of comparing the orientation of the projection (9), onto the coronal plane, of the axis of the trochlear groove with the orientation of the projection (10), onto the coronal plane, of the spherical axis of the femur (1); determining, based on the result of the comparing, at least one of (a) whether the orientation of said projection (9) of the axis of the trochlear groove exhibits a lesser degree of valgus, (b) whether the orientation of said projection (9) of the axis of the trochlear groove exhibits an equal degree of valgus or (c) whether the orientation of said projection (9) of the axis of the trochlear groove exhibits a greater degree of valgus with respect to the orientation of said projection (10) of the spherical axis.

3. A method of planning an alignment of a femoral knee arthroplasty component (2) in a patient, said method comprising the steps of: providing a simulation of a first femoral knee arthroplasty component (2), which simulation yields an orientation of a projection (9), onto a coronal plane, of an axis of a trochlear groove of said first femoral knee arthroplasty component (2); and obtaining an orientation of a projection (10), onto the coronal plane, of a spherical axis of a femur (1 of the patient.

4. The method of claim 3 further comprising the steps of calculating an orientation of the first femoral knee arthroplasty component (2) relatively to the patient's femur (1) such that the orientation of a projection (9), onto a coronal plane, of the axis of the trochlear groove exhibits a greater or equal degree of valgus with respect to the orientation of the projection (10), onto a coronal plane, of the spherical axis of the femur (1).

5. The method of claim 4 further comprising the step of calculating a distal femoral resection plane for affixing the first femoral knee arthroplasty component (2) to the patient's femur (1) in the calculated orientation relatively to the patient's femur (1).

6. A method of planning an alignment of a femoral knee arthroplasty component (2) in a patient, said method comprising the steps of: obtaining intrinsic geometrical data of each of two or more femoral knee arthroplasty components (2), the intrinsic geometrical data including at least the prosthetic trochlea orientation of the respective femoral knee arthroplasty component (2); obtaining an orientation of a projection (9), onto the coronal plane, of a spherical axis of a femur (1) of the patient, which femur (1) is to be provided with the femoral knee arthroplasty component (2); and choosing amongst said two or more femoral knee arthroplasty components (2) a first femoral knee arthroplasty component (2) by considering at least both the orientation of the projection (9) of the spherical axis and the prosthetic trochlea orientations of the two or more femoral knee arthroplasty components (2).

7. A method of monitoring an implanting of a femoral knee arthroplasty component (2) in a patient, said method comprising the steps of obtaining an orientation of a resecting instrument, the resecting instrument or the resection guide being for resecting the distal end of a femur (1) of the patient, which femur (1) is to be provided with said femoral knee arthroplasty component (2); and obtaining a projection (10), onto the coronal plane, of a spherical axis of the femur (1) of the patientr8. The method of claim 7 further comprising the steps of calculating, from the orientation of a resecting instrument, the orientation of the distal femoral resection plane; calculating, based on the orientation of the distal femoral resection plane a projection (9), onto a coronal plane, of an axis of a trochlear groove of a first femoral knee arthroplasty component (2);comparing an orientation of the projection (9) of the axis of the trochlear groove with an orientation of the projection (10), onto the coronal plane, of the spherical axis of the femur (1); determining, based on the result of the comparing the orientation of the projection (9) axis of the trochlear groove with the orientation of the projection (10) of the spherical axis, at least one of (a) whether the orientation of the projection (9) of the axis of the trochlear groove exhibits a lesserTdegree of valgus, (b) whether the orientation of said projection (9) of the axis of the trochlear groove exhibits an equal degree of valgus or (c) whether the orientation of said projection (9) of the axis of the trochlear groove exhibits a greater degree of valgus with respect to the orientation of the of the projection (10) of the spherical axis of the femur.(1).

9. A method of a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component (2) in a patient, said method comprising the method of claim 1.

10. A method of operation of a surgical navigation system (SNS), robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component (2) in a patient, said method comprising the step of the SNS, RASE or RSI orienting the femoral knee arthroplasty component (2) by considering at least both an orientation of a projection (10), onto the coronal plane, of a spherical axis of the patient's femur (1) to be provided with the femoral knee arthroplasty component (2), and an orientation of a projection (9), onto a coronal plane, of an axis of the trochlear groove of said femoral knee arthroplasty component (2).

11. A method of operation of a surgical navigation system (SNS), a robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), assisting an implanting of a femoral knee arthroplasty component (2) in a patient, said method comprising the step of the SNS, RASE or RSI robot positioning a resecting instrument for resecting the distal end of a patient's femur (1) to be provided with the femoral knee arthroplasty component (2) such that the distal femoral resection plane allows for said femoral knee arthroplasty component (2) to be affixed to the patient's femur (1) in a way that an orientation of a projection (9), onto a coronal plane, of the axis of a trochleargroove of the femoral knee arthroplasty component (2) exhibits a equal or greater degree of valgus with respect to the orientation of a projection (10), onto a coronal plane, of a spherical axis of the femur.

12. A method of implanting a femoral knee arthroplasty component (2) in a patient, said method comprising the method of any one of claims 1 to 11.

13. A method of implanting a femoral knee arthroplasty component (2) in a patient, the method comprising the steps of obtaining an orientation of a projection (10), onto the coronal plane, of a spherical axis of a femur (1) of the patient, which femur (1) is provided with said femoral knee arthroplasty component (2); and affixing the femoral knee arthroplasty component (2) to the patient's femur (1) such that an orientation of a projection (9), onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component (2) exhibits a greater degree of valgus or with respect to or is parallel to an orientation of the projection (10), onto a coronal plane, of a spherical axis of the femur.

14. A medical image analysis apparatus for assessing, based on at least one image of the patient's femur (1) and a femoral knee arthroplasty component (2), an alignment of a femoral knee arthroplasty component (2), said apparatus comprising: a trochlear groove gauge or image acquisition unit for obtaining from the image(s) an orientation of a projection (9), onto a coronal plane, of an axis of a trochlear groove of the femoral knee arthroplasty component (2); a spherical axis gauge or image acquisition unit for obtaining from the image(s) an orientation of a projection (10), onto the coronal plane, of a spherical axis a femur(1) of the patient, which femur (1) is provided with the femoral knee arthroplasty component (2).

15. A medical image analysis apparatus for planning, based on an image of the patient's femur (1) provided with a femoral knee arthroplasty component (2), an alignment of a femoral knee arthroplasty component (2) in a patient, said apparatus comprising: a simulator for providing a simulation of a first femoral knee arthroplasty component(2), such that said simulation yields an orientation of a projection (9), onto a coronalplane, of the axis of a trochlear groove of a first femoral knee arthroplasty component (2); a spherical axis gauge or image acquisition unit for obtaining from the image an orientation of a projection (10), onto the coronal plane, of the spherical axis of the femur (1) of the patient to be provided with said femoral arthroplasty component.

16. A medical image analysis apparatus for planning, based on an image of the patient's femur (1) to be provided with a femoral knee arthroplasty component (2), an alignment of a femoral knee arthroplasty component (2) in a patient, said apparatus comprising: an intrinsic geometrical data acquisition unit for obtaining intrinsic geometrical data of each of two or more femoral knee arthroplasty components (2), the intrinsic geometrical data including at least the prosthetic trochlea orientation of the respective femoral knee arthroplasty component (2); a spherical axis gauge or image acquisition unit for obtaining from the image an orientation of a projection (9), onto the coronal plane, of a spherical axis of the femur (1); and a component (2) selector or selection algorithm for choosing amongst the two or more femoral knee arthroplasty components (2) a first femoral knee arthroplasty component (2) by considering at least both the projection of the spherical axis (10) and the prosthetic trochlea orientations (9) of the two or more femoral knee arthroplasty components (2).

17. A medical image analysis apparatus for predicting and monitoring, based on an image of the patient's femur (1) provided with a femoral knee arthroplasty component (2), an alignment of a femoral knee arthroplasty component (2) in a patient, said apparatus comprising: a resecting instrument orientation gauge or image acquisition unit for obtaining an orientation of a resecting instrument or 3D-printed PSI resection guide for resecting the distal end of the femur (1); and a spherical axis gauge or image acquisition unit for obtaining from the image an orientation of a projection (10), onto the coronal plane, of a spherical axis of the femur (1) of the patient, whose femur (1) is to be provided with said femoral knee arthroplasty component (2).

18. A medical imaging apparatus, a surgical navigation system (SNS), a robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI) for assisting an implanting of a femoral knee arthroplasty component (2) in a patient, said, medical imaging apparatus SNS, RASE or RSI comprising the medical image analysis system according to any one of claims 14 to 17.

19. A surgical navigation system (SNS), a robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI), for assisting an implanting of a femoral knee arthroplasty component (2) in a patient, said SNS, RASE or RSI comprising: a manipulator for orienting the femoral knee arthroplasty component (2); and a control unit for operating the manipulator to orient the femoral knee arthroplasty component (2) by considering at least both an orientation of a projection (10), onto the coronal plane, of a spherical axis of the patient's femur (1) to be provided with the femoral knee arthroplasty component (2) and an orientation of a projection (9), onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component (2).

20. A surgical navigation system (SNS), a robotically assisted surgical equipment (RASE) and / or a robotic surgical instrument (RSI) for assisting an implanting of a femoral knee arthroplasty component (2) in a patient, said SNS, RASE or RSI comprising: a manipulator for orienting a resecting instrument for resecting the distal end of a patient's femur (1) to be provided with the femoral knee arthroplasty component (2); and a control unit for operating the manipulator to orient the resecting instrument such that the distal femoral resection plane allows for the femoral knee arthroplasty component (2) to be affixed to the patient's femur (1) in a way that an orientation of a projection (9), onto a coronal plane, of an axis of the trochlear groove of the femoral knee arthroplasty component (2) exhibits an equal or greater degree of valgus with respect to an orientation of a projection (10), onto a coronal plane, of a spherical axis of the femur.

21. A computer program product adapted to cause, when executed on a computer, the computer comprising a processor and a memory, the method according to any of claims 1 to 13.