Femoral prosthesis

Abstract

A femoral prosthesis comprises a U-shaped main body couplable to a resected distal end of a femoral bone. The main body has an outer surface replicating a structural conformation of the distal end and a plurality of flat inner surfaces opposite to the outer surface. Such plurality of inner surfaces comprises: a succession of posteroinferior surfaces opposite to a posterior and inferior portion of the outer surface and having a main axis lying on a sagittal plane and a secondary axis parallel to a transverse axis; a front surface opposite to a front portion of the outer surface and having a main axis lying on the sagittal plane and a secondary axis inclined with respect to the transverse axis on a transverse plane.

Description

[0001] “FEMORAL PROSTHESIS”

[0002] DESCRIPTION

[0003] The present invention relates to the technical field of medical devices, in particular prostheses, and also to methods for identifying and selecting them.

[0004] In particular, the present invention relates to a femoral prosthesis, and also a method for selecting a femoral prosthesis capable of optimising the processes of identifying and selecting a specific prosthesis based on operating needs.

[0005] In the setting of a bone reconstruction operation, it is necessary to perform a series of cuts on the bone to enable the subsequent insertion and coupling of a prosthesis replicating the shape of the damaged bone structure requiring replacement.

[0006] In order to be able to reduce the patient’s discomfort to a minimum and optimise the postoperative recovery and rehabilitation process, it is customary to carry out a design process whereby a special customised prosthesis, specifically modelled on the basis of measurements of the patient’s bone, as well as the geometry of the specific cuts to be performed during the operation, is generated for the individual patient.

[0007] This approach is particularly followed in the context of knee reconstruction operations, which can be carried out, for example, according to the kinematic alignment (KA) approach.

[0008] In accordance with this technique, the objective is to reconstruct the specific alignment of the patient’s limbs, as well as to completely restore his or her biomechanical situation on the basis of the specific kinematic axes of the patient him / herself.

[0009] By way of example, in the case of a patient affected by arthritis, it is possible to perform a femur arthroplasty operation by resecting the bone along cutting axes specifically selected on the basis of the patient’s pre- arthritic kinematic axes.

[0010] In this context, it appears to be particularly advantageous to produce a customised prosthesis in order to be able to obtain a replica as faithful as possible of the preoperative joint situation.

[0011] However, it is evident that a procedure of this type is extremely burdensome from both a cost and time standpoint.

[0012] In fact, the creation of a prosthesis having this level of customisation requires processing specifically designed around the patient’s bone measurements, thus leading to the generation of a substantially unique piece.

[0013] Thus, there is a strongly felt need in the sector to develop new operating methods, as well as new instruments, capable of providing an approach and solutions that are more generalised and universally applicable without, however, losing the advantages assured by the current level of customisation, thanks to which a satisfactory structural correspondence between the implanted prosthesis and the bone structure it replaces is ensured.

[0014] Furthermore, the known femoral prostheses have a structure that causes a progressive displacement of the patella or the patello-femoral prosthesis coupled to them, causing a stress that damages them and reduces their useful lifetime, as well as reducing their functionality.

[0015] Furthermore, in certain implementational situations, the femoral prostheses of known type are affected by structural problems that make their application in a correct and optimal position particularly complicated.

[0016] In particular, the structure of the known femoral prostheses is such as to produce an undesired interference with the patellar component, with the consequent risk of misalignment of patellar tracking.

[0017] Operatively, the patella could, in fact, not interact correctly with the portion of femoral prosthesis defining the front shield, sliding incorrectly on the latter, with the consequent risk of a dislocation or, in any case, considerable risks of damage to the knee joint.

[0018] In order to avoid this problem, it is known in the sector to alter, during the operative stage, the direction of the cuts to be performed on the femur, so as to be able to rotate / incline the surface of the front shield, in order to alter the coupling thereof with the patellar component and thus obtain a correct patellar tracking.

[0019] This rotation causes, in fact, a change in the inclination of the front shield with respect to the patella, which therefore slides on the former along an optimised profile that avoids the risk of dislocation.

[0020] However, such a rotation is not an optimal solution, as it inevitably also influences the posterior portion of the femoral prosthesis that must interact with the tibial component.

[0021] In this situation, the tibial component therefore has to engage a rotated femoral prosthesis and this has negative repercussions overall on the functioning of the knee joint.

[0022] A possible alternative solution would be to process the front shield by removal, so as to model the surface thereof to adapt it to the necessary movements of the patellar component.

[0023] However, this solution is also unsuitable for addressing this problem in a satisfactory manner, since the further processing of the femoral prosthesis required to shape the front shield opportunely is not only burdensome from the viewpoint of identifying the correct profile and the manufacturing thereof, but also causes a removal of material either on the prosthesis itself, with the consequent risk of compromising the solidity and durability of the femoral prosthesis, or on the femoral bone, with potential disadvantages for the patient's health.

[0024] In this context, the object of the present invention is to provide a femoral prosthesis characterised by a specific structural conformation capable of simultaneously guaranteeing a correct engagement and movement of the patellar component, without at the same time compromising the integrity of the femoral prosthesis or the interaction thereof with the tibial component.

[0025] A further technical task at the basis of the present invention is to propose a method for selecting a femoral prosthesis that overcomes at least some of the aforementioned drawbacks of the prior art. In particular, it is an object of the present invention to provide a method capable of reducing the times and costs of selecting and obtaining the prosthesis, while at the same time maintaining an optimal correspondence between the selected prosthesis and bone structure to be repaired.

[0026] The stated technical task and specified objects are substantially achieved by a femoral prosthesis comprising the technical features set forth in one or more of the appended claims.

[0027] Further aspects of the present invention relate to a knee arthroplasty system, a method for selecting a femoral prosthesis and a database of prosthetic data, as presented in the independent claims.

[0028] The dependent claims, which are incorporated herein by reference, correspond, on the other hand, to different embodiments of the invention.

[0029] Further features and advantages of the present invention will become more apparent from the indicative, and hence non-limiting, description of a preferred, but not exclusive, embodiment of a femoral prosthesis, as illustrated in the appended drawings, in which:

[0030] - figure 1 shows a femoral prosthesis;

[0031] - figures 2A-2B show in detail one component of the prosthesis in figure 1 ;

[0032] - figures 3A-3B illustrate a comparison between the structure of a femoral prosthesis of known type (shown on the left) and a femoral prosthesis according to the present invention (shown on the right) viewed on a transverse plane.

[0033] In the present description, reference number 1 is used to indicate a femoral prosthesis, which, for the sake of descriptive simplicity, will be referred to below as prosthesis 1 .

[0034] Such prosthesis 1 essentially comprises a main body 2 configured to replace the structure of the distal end of the femur.

[0035] Preferably, the prosthesis 1 is of the ball-and-socket type and further comprises a medial sphere couplable to the main body.

[0036] This type of prosthesis envisages replicating the joint mechanics of the knee by means of a main body 2 replacing the structure of the distal end of the femur and which is couplable to the tibia via a medial sphere.

[0037] The medial sphere in turn operatively defines at least in part a ball joint capable of ensuring optimal mobility of the limb at the end of the operation. Advantageously, the prosthesis 1 can possibly also comprise a tibial prosthesis contributing overall to define a prosthesis for the knee joint.

[0038] In more detail, the main body 2 has a U-shaped conformation that defines and operatively delimits a volume adapted to house by insertion a resected distal end of the femoral bone.

[0039] In other words, during an operation to replace the knee joint, the distal end of the patient's femur is resected, i.e. cut, along specific cutting planes and the main body 2 of the prosthesis 1 is then fitted onto such resected end.

[0040] Structurally, the main body 2 has an outer surface replicating a structural conformation of the distal end.

[0041] In other words, the outer surface identifies the portion of the main body 2 aimed at replicating the structure, conformation and function of the distal end, providing the interface configured to abut against a tibial prosthesis and, in any case, configured to interface the main body 2 with the other components of the knee joint.

[0042] The main body 2 has and further comprises a plurality of flat inner surfaces.

[0043] Such flat inner surfaces are opposite to the outer surface (therefore defining an inner profile of the U) and therefore delimit the insertion / coupling volume of the resected distal end.

[0044] Such flat inner surfaces are therefore configured to abut against respective resected surfaces of the distal end.

[0045] In more detail, each flat inner surface is defined by a respective main axis and by a respective secondary axis.

[0046] In general, main axis and secondary axis identify the plane on which the respective flat inner surface lies.

[0047] In this context, in a configuration of use of the prosthesis, i.e. when the prosthesis 1 is coupled to the resected distal end of the femoral bone, each main axis is lying on a sagittal plane S, i.e. a plane that runs in an anteroposterior direction and divides the body into two parts, right and left. The secondary axes, on the other hand, can have different inclinations.

[0048] In particular, the plurality of inner surfaces comprises a succession of posteroinferior surfaces and a front surface 11 .

[0049] The posteroinferior surfaces are opposite to a posterior portion of the outer surface, i.e. in a configuration of use, they engage the posterior and inferior resected portions of the distal end, whereas the front surface 11 is opposite to a front portion of the outer surface, i.e. in a configuration of use it engages the resected front portion of the distal end.

[0050] Each posteroinferior surface has a secondary axis parallel to a transverse axis and, preferably, perpendicular to a sagittal axis.

[0051] In other words, the posteroinferior surfaces are perpendicular (or parallel) to the sagittal plane S.

[0052] In accordance with a possible embodiment, the succession of posteroinferior surfaces can comprise a first surface 7, a second surface 8, a third surface 9 and a fourth surface 10.

[0053] The first surface 7 is parallel to the front plane F and thus its main axis, in addition to lying on the sagittal plane S, is also parallel to the longitudinal axis.

[0054] The second surface 8, on the other hand, is parallel to the transverse plane and thus its main axis, in addition to lying on the sagittal plane S, is also parallel to the sagittal axis.

[0055] The third surface 9 is interposed between the first and the second surface 8 and acts as the coupling between the two, thus being inclined with respect to them and intersecting them (therefore being incident to them) on respective lines parallel to the transverse axis.

[0056] The fourth surface 10, on the other hand, acts as the coupling between the second surface 8 and the front surface 11 , being interposed between the two.

[0057] Such fourth surface 10 is incident with the second surface 8 along a line parallel to the transverse axis and with the front surface 11 along a line inclined with respect to the transverse axis on the transverse plane.

[0058] In contrast with the posteroinferior surfaces, the front surface 11 has a secondary axis inclined inside the transverse plane with respect to the transverse axis.

[0059] In other words, the front surface 11 is inclined with respect to the sagittal plane S.

[0060] As a result, therefore, as can be seen in figure 3B, the front surface 11 is inclined with respect to the front plane F and, above all, has an inclination with respect to the corresponding front surface 11 of a main body 2 of known type (shown on the left side of figure 3).

[0061] Preferably, the front surface 11 is inclined by a predefined angle comprised between -5° and +5°, meaning that the secondary axis of the front surface 11 is inclined by an angle comprised between -5° and +5° with respect to the transverse axis.

[0062] Therefore, as can be seen in figure 3, the front portion 4 of the prosthesis 1 is rotated and, taking as a reference the plane X (parallel to the front plane F) tangent to a lateral component 12 of the known femoral prosthesis shown on the left in figure 3, it can be observed that such plane is, on the contrary, distanced from and therefore not tangent to the corresponding lateral component 13 of the prosthesis 1 according to the present invention, shown on the right in the same figure.

[0063] The present application also relates to a knee arthroplasty system comprising a plurality of families of prostheses for reconstructing a femoral bone.

[0064] Such prostheses 1 are specifically designed for the reconstruction of a femoral bone, in particular a distal end of the femoral bone, and are preferably manufactured in accordance with the structural specifications described above.

[0065] In addition to what has already been discussed, the main body 2, which may be seen in detail in figures 2A-2B, has a front portion 4 and two joint portions 5 that extend away from the front portion 4.

[0066] The front portion 4 replicates the structure of the intercondylar fossa of the distal end of the femur and defines a portion of the prosthesis 1 identified as the front shield, whereas the joint portions 5 replicate the structure of the medial condyle and lateral condyle of the femur, respectively.

[0067] The arched shape of the front portion 4 and of the joint portions 5 combine to delineate the housing volume intended to house and abut at least partially against the femoral bone (in particular with its resected distal end) and inside which the medial sphere is accommodated.

[0068] The medial sphere can, in turn, be coupled with a tibial prosthesis 6 to interconnect the patient's tibia and femur (such tibial prosthesis may or may not be part of the prosthesis 1 ).

[0069] The use of a structure of the ball-and-socket type with the presence of the medial sphere makes it possible to define, operatively, a joint endowed with a high degree of freedom, such as to optimally replicate a healthy knee joint, resulting in a particularly efficient, robust prosthesis 1 and reducing the times (and thus also the costs) of a subsequent patient movement rehabilitation process.

[0070] Each family of femoral prostheses 1 comprises a respective plurality of femoral prostheses 1 whose structure is defined by at least one engagement parameter and one bone parameter.

[0071] The engagement parameter is representative of a size and / or shape and / or inclination (intended as an inclination of the main and secondary axes) of each flat inner surface adapted to engage respective resected surfaces or a diameter of a medial sphere coupled or couplable to the main body 2, and the bone parameter, on the other hand, is representative of a size and / or shape of a portion of the front surface 11 .

[0072] Therefore, the engagement parameter identifies the structure, shape and size of the cuts and thus of the bone surface against which the prosthesis will be abutted or in any case of elements configured to interact directly with the bone to be repaired, whereas the bone parameter identifies the shape and size of the portion of bone that will be replaced by the prosthesis.

[0073] In this context, analogously to what was described above, each femoral prosthesis 1 has the same engagement parameter as each other femoral prosthesis 1 of the same family and at least one bone parameter different from a corresponding bone parameter of at least one other femoral prosthesis 1 of the same family.

[0074] Making reference now to an embodiment, identified for the sake of descriptive simplicity as embodiment A, the system comprises a plurality of distinct families characterised by different diameter values of the medial sphere.

[0075] In other words, different families have different diameter values of the medial sphere whereas the members of each family have the same engagement parameter, i.e. the same diameter of the medial sphere, and different bone parameters.

[0076] Making reference now to a further embodiment, identified for the sake of descriptive simplicity as embodiment B, the femoral prostheses 1 are subdivided into a plurality of distinct families characterised by different values of at least one of the length, height, width, inclination of the flat inner surfaces of the prosthesis 1 .

[0077] In other words, different families have different values of at least one of the length, height, width, inclination of the flat inner surfaces of the prosthesis 1 , whereas the members of each family have the same engagement parameters, i.e. equal values for at least one of the length, height, width and inclination of the flat inner surfaces of the prosthesis 1 , and different bone parameters.

[0078] In general, i.e. irrespective of the specific embodiment implemented, the system makes it possible to classify the femoral prostheses 1 , making them more easily identifiable and providing a wide array of solutions wherein the best solution is more easily identifiable and made immediately available thanks to the presence of a kit of different femoral prostheses 1 characterised by different shapes and sizes.

[0079] Advantageously, each prosthesis 1 can be further catalogued, categorised or defined based on a biometric parameter representing an indication of potential patient phenotypes and / or morphotypes.

[0080] In other words, the biometric parameter identifies the respective prosthesis, defining an adaptability thereof to specific known phenotypes and / or morphotypes.

[0081] In particular, within every family of femoral prostheses there thus exist prostheses specifically adapted to best accommodate the needs of the specific patient morphotype / phenotype, such as, for example, a varus or valgus form of the hip-knee-ankle (HKA) angle according to the traditional classification or joint line obliquity (distal, neutral, proximal apex), according to the CPAK classification.

[0082] A customisation of the prosthesis 1 is thus made possible, while at the same time avoiding the need to design and produce individual prostheses 1 for every arthroplasty operation.

[0083] The present invention also relates to a method aimed at optimising the process of selecting the femoral prosthesis 1 most suitable to be used during a bone reconstruction operation, in particular an operation for reconstruction of the knee joint.

[0084] The method has particular application in the selection of a prosthesis for reconstructing a distal end of a femur.

[0085] The method is executable by a computer, i.e. any electronic device comprising one or more processing units, processors, and electronic components endowed with a capacity to compute and to manipulate inputs required for the correct execution of the method itself, which are presented and described in detail further below in the present description.

[0086] In this context, the claimed method is carried out by acquiring a three- dimensional model of a patient’s femur at a pre-operative stage.

[0087] In other words, one acquires, by means of known methods (for example by means of a tomography technique or by reconstructing a three- dimensional model from two-dimensional X-ray images or else by means of magnetic resonance techniques), information making it possible to generate and acquire a three-dimensional representation of the femur on which the bone repair operation will be performed.

[0088] Once the image has been acquired, one proceeds to measure a plurality of identification parameters in that 3D model.

[0089] The identification parameters are generally parameters which enable specific structural and dimensional characteristics of the femur to be determined and categorised so as later to be able to identify the femoral prosthesis 1 that best reproduces and / or approximates those characteristics.

[0090] In greater detail, the identification parameters comprise at least one engagement parameter and at least one bone parameter.

[0091] As already mentioned when discussing the system, the engagement parameter is a parameter representative of a size and / or shape and / or inclination of each flat inner surface adapted to engage respective resected surfaces.

[0092] In fact, in a bone reconstruction operation it is necessary to perform cuts on the patient’s femoral bone to enable the placement and coupling of the prosthesis (which in turn replicates the bone structure that was removed following the cuts).

[0093] The bone parameter, on the other hand, is representative of a size and / or shape of a portion of the front surface 11 .

[0094] In greater detail, the present invention has particular application for reconstructing the distal end of the femur through the implementation of a prosthesis of the ball-and-socket type.

[0095] In general, the engagement parameter comprises at least one of: a maximum height and / or width and / or an inclination of one or more flat inner surfaces of the prosthesis 1 .

[0096] The engagement parameter thus defines in general a structure, geometry, and shape of the inner surfaces of the prosthesis, i.e. the surfaces configured to engage bone surfaces appropriately cut and shaped to receive that prosthesis.

[0097] In other words, in the specific case of prostheses of the ball-and-socket type, the engagement parameter can thus comprise a profile of the internal cut, hence the length, height, and width of the inner surfaces of the prosthesis (i.e. the portion configured to define the seat suitable to accommodate the medial sphere), or parameters defined based on a couplability of the prosthesis with the patient’s femoral bone, such as, for example, the corresponding dimensions of the surfaces or bone structures of the patient that will abut against or in general will have to interact with one or more portions of the prosthesis.

[0098] Alternatively, or additionally, in the case of prostheses of the ball-and- socket type, the engagement parameter can also refer to dimensional parameters of the medial sphere, thus including, for example, a radius of a medial sphere.

[0099] The bone parameter, on the other hand, comprises at least one of: a radius of a sphere approximating the profile of a portion of the femoral prosthesis 1 replicating a femoral condyle, a maximum width and / or height of a portion of the prosthesis replicating a posterior and / or distal portion of the femoral condyle, a maximum width and / or height and / or an angle of inclination of a main axis of extension of a portion of the prosthesis replicating the intercondylar fossa.

[0100] The bone parameters can also comprise other parameters representative of the structure of the prosthesis, such as, for example, the orientation of the trochlea or the length and width of the anterior shield or the distal width or the height and width of the posterior condyles.

[0101] The bone parameter thus defines in general a structure, geometry, and shape of the outer surfaces of the prosthesis, i.e. the surfaces configured to replicate an outer structure / surface of one or more bone portions.

[0102] Advantageously, the bone parameters can also be defined on the basis of elements and anatomical structures external to the bone itself but nonetheless such as to be in direct contact with the bone.

[0103] In other words, the bone parameters can also be defined on the basis of parameters relating, for example, to connective tissues destined to engage the prosthesis 1 and / or comprise such parameters relating for example to connective tissues.

[0104] Operatively, the method described herein thus envisages making a series of measurements on the 3D image of the femur and identifying thereon the parameters that define the prosthesis best matching the patient’s specific anatomy, mainly considering the structure of the femoral bone and potentially also the structure and the characteristics of the adjacent tissues.

[0105] For example, by measuring the sizes of the cuts to be performed on the femoral bone it is possible to obtain the engagement parameter simply by defining the dimensions of the inner surface of the prosthesis that best match those sizes.

[0106] Similarly, by measuring for example a size of the patient’s condyles and / or acquiring data on the intercondylar fossa, it is possible to determine and define the corresponding bone parameters.

[0107] Referring by way of example to a possible implementation corresponding with the aforementioned embodiment A, the method is carried out by measuring an engagement parameter corresponding to the diameter of the medial sphere and a plurality of bone parameters.

[0108] The bone parameters in this specific context comprise: a mediolateral dimension of the patient’s femur, an anteroposterior dimension of the patient’s femur, a length of the posterior condyle, a length of the intercondylar fossa, an orientation of the intercondylar fossa (for example the inclination thereof relative to one or more cutting planes), a sagittal profile of the intercondylar fossa, an axial profile of the intercondylar fossa, an axial or lateral position of the intercondylar fossa, a dimensional measurement of an anterior shield of the prosthesis.

[0109] Referring now to a possible implementation corresponding with the aforementioned embodiment B, the method is carried out by measuring a plurality of engagement parameters corresponding to a profile of the cuts to be performed on the femur, i.e. these engagement parameters thus correspond to at least one of a length, height, width, inclination of the flat inner surfaces of the prosthesis 1 .

[0110] The bone parameters in this specific context comprise: an anteroposterior dimension of the patient’s femur, a length of the posterior condyle, a length of the intercondylar fossa, an orientation of the intercondylar fossa (for example the inclination thereof relative to one or more cutting planes), a sagittal profile of the intercondylar fossa, an axial profile of the intercondylar fossa, an axial or lateral position of the intercondylar fossa, and a dimensional measurement of an anterior shield of the prosthesis.

[0111] Once the identification parameters of interest have been acquired, one proceeds to query a specific database comprising prosthetic data identifying a plurality of femoral prostheses catalogued and categorised according to such identification parameters.

[0112] In particular, the femoral prostheses are stored and subdivided within the database into a plurality of distinct families.

[0113] The families are established in such a way that each femoral prosthesis 1 has the same engagement parameter as each other femoral prosthesis 1 of the same family and at least one bone parameter different from a corresponding bone parameter of at least one other prosthesis of the same family.

[0114] Therefore, each family is defined overall by all the femoral prostheses 1 suitable to be applied to a given cutting profile (and thus interfaceable with a femoral bone on which cuts having specific dimensional characteristics have been made) and contains within it a plurality of femoral prostheses 1 characterised by structures adapted to replicate respective bone structures of different sizes.

[0115] Based on the query just described, the specific femoral prosthesis 1 having the highest number of matches between the identification parameters measured on the 3D femur and the identification parameters of the femoral prosthesis is selected from within the database.

[0116] The expression “highest number of matches” is meant to identify the femoral prosthesis 1 that best approximates the highest possible number of parameters identifying the patient’s femoral bone.

[0117] Making reference to embodiment A presented above, the method is carried out by querying a database comprising prosthetic data identifying a plurality of femoral prostheses 1 according to respective identification parameters, wherein the femoral prostheses 1 are subdivided into a plurality of distinct families characterised by different diameter values of the medial sphere.

[0118] In other words, different families have different diameter values of the medial sphere whereas the members of each family have the same engagement parameter, i.e. the same diameter of the medial sphere, and different bone parameters.

[0119] With reference, on the other hand, to embodiment B, the method is carried out by querying a database comprising prosthetic data identifying a plurality of femoral prostheses 1 according to respective identification parameters, wherein the femoral prostheses 1 are subdivided into a plurality of distinct families characterised by different values of at least one of the length, height, width, inclination of the flat inner surfaces of the prosthesis 1 .

[0120] In other words, different families have different values of at least one of the length, height, width, inclination of the flat inner surfaces of the prosthesis 1 , whilst the members of each family have the same engagement parameters, i.e. equal values for at least one of the length, height and width of the flat inner surfaces of the prosthesis 1 , and different bone parameters.

[0121] For the sake of completeness, it is noted that in accordance with embodiment B, there are different possible implementational situations in which, for example, a same family has the same value for only one of the length, height, width, and inclination of the inner surfaces of the prosthesis without placing particular constraints on the other parameters, or each family has the same value for two or even three of the parameters specified above without placing particular constraints on the parameters not selected, or also be characterised by identical values of all four of the parameters specified above.

[0122] Advantageously, it is likewise possible to associate with each identification parameter (engagement or bone) a relative weight representative of a level of relevance thereof and the selection of the femoral prosthesis 1 is made also based on that relative weight.

[0123] Preferably, it is likewise possible to acquire at least one biometric parameter of the patient and the selection of the femoral prosthesis 1 can be made also as a function of that biometric parameter, possibly weighed on the basis of a specific relative weight thereof.

[0124] In particular, the biometric parameter can comprise a morphotype and / or a phenotype of the patient, such as, for example, a classification into varus / valgus or according to specific known classifications, e.g. CPAK.

[0125] Advantageously, it is likewise possible to edit or update the database by storing or modifying prosthetic data.

[0126] This operation may be carried out also on the basis of the outcomes of the femoral prosthesis 1 selection step in order to optimise and improve that process.

[0127] For example, if the selected femoral prosthesis 1 is not sufficiently satisfactory from the standpoint of adaptability to the patient’s anatomy, it will be possible to modify the relative weight of the parameters and / or modify the identification data of the prosthesis and repeat the database query in order to identify a femoral prosthesis 1 better suited to the bone repair operation that is being planned.

[0128] Once the femoral prosthesis 1 has been selected, it is possible, moreover, to query a tracking table in which tracking data of the femoral prostheses 1 are stored, i.e. data identifying the presence and preferably the position of the selected femoral prosthesis 1 within a storage warehouse.

[0129] In other words, the method envisages identifying a specific femoral prosthesis 1 and also identifying the position in which that prosthesis is to be found to enable an easier acquisition and possibly also automate a process of dispatching the prosthesis from the warehouse to the facility in which the bone reconstruction operation will be performed.

[0130] Advantageously, if it is not possible to identify a femoral prosthesis 1 sufficiently conforming and corresponding to the acquired identification parameters (or if the selected femoral prosthesis 1 is not present within the storage warehouse) it is possible to generate an alert signal.

[0131] For example, this signal can be generated when the database does not comprise prosthetic data identifying a femoral prosthesis 1 having at least one identification parameter corresponding to the identification parameters measured on the 3D femur.

[0132] It is worth highlighting that the correspondence is preferably a numerical correspondence and a confidence threshold can be set to determine when there is or is not a correspondence between the values analysed.

[0133] For example, a value can be considered to correspond if it falls within a range of values centred on the reference value and extending from -10% to + 10% of the reference value.

[0134] For example, considering a bone parameter corresponding to the radius of a sphere approximating the profile of a lateral condyle, given a measurement of 20 mm on the 3D image, one may consider all the femoral prostheses having a radius of a sphere approximating the profile of the portion of prosthesis which replicates the lateral condyle in the range of between 18 mm and 22 mm as conforming to that measurement. In this context, it is also possible to define a level of conformity in which prostheses with parameters coming closer to the specific value measured on the 3D image have a higher level of conformity than prostheses which, despite still being within the range indicated, are in any case farther from the reference value. In the event of complete equivalence between several prostheses (also after considering the number of parameters found to conform, the relative weight of each parameter and the level of conformity thereof) it is also possible to provide an indication and selection of all the prostheses considered to conform sufficiently to the patient’s anatomy.

[0135] In order to further optimise the selection of the most suitable femoral prosthesis 1 , the present method can also be carried out in such a way as to display the 3D model on a video terminal, superimposing thereon a graphic representation of the selected femoral prosthesis 1 .

[0136] On the video terminal it is thus possible to highlight any identification parameters for which there is not conformity between the 3D model and the graphic representation of the selected femoral prosthesis 1 .

[0137] In this manner it is possible to verify whether the selection of the relative weights of the various identification parameters is satisfactory or whether it is instead necessary to introduce modifications so as to select a different femoral prosthesis 1 that better approximates different structural features of the bone.

[0138] The method may also be carried out to store a result of the femoral prosthesis 1 selection step by populating a database of results.

[0139] In other words, the data of the specific femoral prostheses 1 selected in successive iterations of the method are stored in the database of results.

[0140] It is thus possible to apply a statistical analysis on the database of results by determining a selection incidence curve for the femoral prostheses 1 as a function of the identification parameters thereof.

[0141] Therefore, it is possible to generate a curve which represents the statistical use of the femoral prostheses 1 as a function of their structural and dimensional characteristics.

[0142] This information may be used to optimise the management of the families of femoral prostheses 1 by reducing the number of (or even eliminating) the femoral prostheses 1 that over time are not selected or selected a statistically insignificant number of times and instead increasing the number of femoral prostheses 1 whose use is more frequent.

[0143] In this manner, one optimises the possibility of always having available a given femoral prosthesis 1 that is suited to the patient’s anatomy in the event of a specific request for the performance of an arthroplasty operation.

[0144] It is also possible to use this information for the subsequent design of new prostheses, in order to populate the most widely used families of femoral prostheses 1 with a higher number of different copies and create new femoral prostheses 1 having identification parameters falling among the values of those that are most widely used.

[0145] If, for example, one finds a large use of prostheses belonging to adjacent families, i.e. ones having values of the engagement parameters immediately consecutive to each other, it will be possible to develop a new family having engagement parameters which are intermediate between the ones of the two most widely used families, thus also improving the precision with which the prostheses 1 can be selected.

[0146] Therefore, the method described thus far makes it possible to identify and select the femoral prosthesis 1 that best satisfies the patient’s needs, thanks to an optimised approach whereby the available femoral prostheses are categorised by means of objective criteria that can be rapidly and efficiently selected and if necessary also modified, while providing useful feedback for inventory management and for the design of new femoral prostheses 1 .

[0147] What has been discussed so far in regard to the method, with particular reference to the selectable parameters, also has an identical and corresponding application in the system presented above.

[0148] The present invention also relates, moreover, to a database comprising prosthetic data identifying a plurality of femoral prostheses 1 belonging to a system according to what was described in the previous paragraphs and thus subdivided according to respective identification parameters.

[0149] In particular, the femoral prostheses 1 are subdivided into a plurality of distinct families, wherein the femoral prostheses 1 of a same family have the same engagement parameter and at least one different bone parameter.

[0150] Moreover, the database is specifically queryable during the execution of the method described above.

[0151] Making reference to embodiment A presented above, the database can comprise prosthetic data identifying a plurality of femoral prostheses as a function of respective identification parameters, wherein the femoral prostheses are subdivided into a plurality of distinct families characterised by different diameter values of the medial sphere.

[0152] In other words, different families have different diameter values of the medial sphere whereas the members of each family have the same engagement parameter, i.e. the same diameter of the medial sphere, and different bone parameters.

[0153] With reference, on the other hand, to embodiment B, the database comprises prosthetic data identifying a plurality of femoral prostheses as a function of respective identification parameters, wherein the femoral prostheses are subdivided into a plurality of distinct families characterised by different values of at least one of the length, height, width and inclination of the inner surfaces of the prosthesis.

[0154] In other words, different families have different values for at least one of length, height, width and inclination of the inner surfaces of the prosthesis, whereas the members of each family have the same engagement parameters, i.e. equal values for at least one of the length, height, width and inclination of the inner surfaces of the prosthesis 1 , and different bone parameters.

[0155] Preferably, the database also comprises a tracking table of femoral prostheses 1 containing tracking data of a position of the femoral prostheses 1 within a storage warehouse.

[0156] The database can further comprise within it (allocated to a suitable local or distributed storage unit) a database of results adapted to store each femoral prosthesis selected by carrying out the selection method presented herein.

[0157] Advantageously, in all the aspects claimed and described, the present invention achieves the proposed objects, overcoming the aforementioned drawbacks in the prior art, by providing the user with a method for selecting femoral prostheses 1 , a system comprising such femoral prostheses 1 and a database enabling the desired prosthesis 1 to be identified within the system by carrying out the various operations envisaged by the method.

Claims

CLAIMS1. Femoral prosthesis comprising a U-shaped main body (2) couplable to a resected distal end of a femoral bone, said main body (2) having:- an outer surface replicating a structural conformation of said distal end; and- a plurality of flat inner surfaces opposite to the outer surface and configured to abut against respective resected surfaces of the distal end, said flat inner surfaces being defined by a combination of respective main axes lying on a sagittal plane (S) and secondary axes; wherein said plurality of flat inner surfaces comprises:- a succession of posteroinferior surfaces opposite to a posterior and inferior portion of the outer surface and having a secondary axis parallel to a transverse axis;- a front surface (11 ) opposite to a front portion of the outer surface and having a secondary axis inclined with respect to said transverse axis on a transverse plane.

2. The prosthesis according to claim 1 , wherein the secondary axis of the front surface (11 ) is inclined with respect to the transverse axis by an angle comprised between -5° and +5°.

3. The prosthesis according to claim 1 or 2, wherein the succession of posteroinferior surfaces comprises:- a first surface (7) parallel to a front plane (F);- a second surface (8) parallel to a transverse plane;- a third surface (9) interposed between the first and the second surface (8) and incident with said first and second surface (8) along respective lines parallel to the transverse axis;- a fourth surface (10) interposed between the second surface (8) and the front surface (11 ) and incident with said second surface (8) along a line parallel to the transverse axis and incident with the front surface (11 ) alonga line inclined with respect to the transverse axis on a transverse plane.

4. The prosthesis according to any one of the preceding claims, wherein said prosthesis (1 ) is of the ball-and-socket type and further comprises a medial sphere couplable to the main body (2).

5. A knee arthroplasty system comprising a plurality of families of prostheses (1 ) for reconstructing a femoral bone, preferably for reconstructing a distal end of said femoral bone, wherein each family of prostheses (1 ) comprises a respective plurality of femoral prostheses (1 ) in accordance with any one of the preceding claims and wherein a structure of each femoral prosthesis (1 ) is defined by at least one engagement parameter representative of a size and / or shape and / or inclination of each flat inner surface adapted to engage respective resected surfaces and at least one bone parameter representative of a size and / or shape of a portion of the front surface (11 ); each femoral prosthesis (1 ) having the same engagement parameter as each other femoral prosthesis (1 ) of the same family and at least one bone parameter different from a corresponding bone parameter of at least one other prosthesis (1) of the same family.

6. The system according to claim 5, wherein each prosthesis (1 ) comprises a prosthesis (1 ) of the ball-and-socket type and wherein the engagement parameter comprises at least one of: a height and / or a maximum width and / or an inclination of one or more flat inner surfaces; and wherein said bone parameter comprises at least one of: a radius of a sphere approximating the profile of a portion of the femoral prosthesis (1 ) replicating a femoral condyle, a maximum width and / or height of a portion of the prosthesis (1 ) replicating a posterior and / or distal portion of said femoral condyle, a maximum width and / or height and / or an angle of inclination of a main axis of extension of a portion of the prosthesis (1 )replicating the intercondylar fossa.

7. Computer-executable method for selecting a femoral prosthesis (1 ) in accordance with any one of the preceding claims, comprising the steps of:- acquiring a 3D model of a patient's femur at a pre-operative stage;- measuring on said 3D model a plurality of identification parameters comprising at least one engagement parameter representative of a size and / or shape and / or inclination of each flat inner surface adapted to engage respective resected surfaces and at least one bone parameter representative of a size and / or shape of a portion of the front surface (11 );- querying a database comprising prosthetic data identifying a plurality of femoral prostheses (1 ) according to respective identification parameters, said femoral prostheses (1 ) being subdivided into a plurality of distinct families, wherein each femoral prosthesis (1 ) has the same engagement parameter as each other femoral prosthesis (1 ) of the same family and at least one bone parameter different from a corresponding bone parameter of at least one other prosthesis (1 ) of the same family;- selecting from said database a femoral prosthesis (1 ) with the highest number of matches between the identification parameters measured on the 3D femur and the identification parameters of said femoral prosthesis (1 )-8. The system according to claim 7, wherein the engagement parameter comprises at least one of: a height and / or a maximum width and / or an inclination of one or more flat inner surfaces; and wherein said bone parameter comprises at least one of: a radius of a sphere approximating the profile of a portion of the femoral prosthesis (1 ) replicating a femoral condyle, a maximum width and / or height of a portion of the prosthesis (1 ) replicating a posterior and / or distal portion of said femoral condyle, a maximum width and / or height and / or an angle of inclination of a main axis of extension of a portion of the prosthesis (1) replicating the intercondylarfossa.

9. The method according to claim 7 or 8, comprising a step of associating with each identification parameter a relative weight representative of a level of relevance of said identification parameter and said step of selecting a femoral prosthesis (1 ) is also performed as a function of said relative weight.

10. The method according to any one of claims 7 to 9, comprising a step of querying a tracking table containing tracking data of a position of the femoral prostheses (1 ) to verify a presence and preferably a position of the selected prosthesis (1 ) within a storage warehouse.

11. The method according to any one of claims 7 to 10, comprising the steps of:- displaying the 3D model on a video terminal;- superimposing a graphic representation of the selected femoral prosthesis (1 ) on said 3D model;- highlighting on said video terminal any non-conforming identification parameters between the 3D model and said graphic representation of the selected prosthesis (1 ).

12. The method according to any one of claims 7 to 10, comprising the steps of:- storing a result of said femoral prosthesis (1) selection step by populating a database of results;- applying a statistical analysis to said database of results by determining a selection incidence curve for said prostheses (1 ) as a function of the respective identification parameters.

13. Database comprising prosthetic data identifying a plurality of femoralprostheses (1 ) according to respective identification parameters comprising at least one engagement parameter representative of a size and / or shape and / or inclination of each flat inner surface adapted to engage respective resected surfaces and at least one bone parameter representative of a size and / or shape of a portion of the front surface (11 ), said femoral prostheses (1 ) being subdivided into a plurality of distinct families, wherein the femoral prostheses (1 ) of a same family have the same engagement parameter and at least one different bone parameter.

14. Database according to claim 13, comprising a tracking table of said femoral prostheses (1 ) containing tracking data of a position of said femoral prostheses (1 ) within a storage warehouse.

15. Database according to claim 13 or 14, comprising a results database adapted to store each femoral prosthesis (1 ) selected by performing said selection method.

16. Database according to any one of claims 13 to 15, wherein said database is queryable during the execution of a method for selecting prostheses (1 ) according to any one of claims 7 to 12 and / or said database is configured to store prosthetic data identifying a plurality of femoral prostheses (1 ) belonging to a system according to claim 5 or 6.

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