An orthopaedic training device

Abstract

Training aids for surgeons to simulate the repair or replacement of a knee joint include unitary pieces comprised of a material strong enough to withstand being put under tension without snapping, yet

Description

The present invention relates generally to an orthopaedic training device and an orthopaedic training system, and finds particular, although not exclusive, utility in aids for demonstrating and practicing surgical orthopaedic techniques. It is known to provide orthopaedic training aids for surgeons to simulate the repair or replacement of a human knee joint. The human knee joint is between the femur and tibia. Such training aids include facsimiles of the distal end of the femur and the proximal end of the tibia. In use, the facsimiles are placed within a support structure, and positioned to form a facsimile of an anatomically correct knee joint. Tensioning cords extend between the facsimiles to simulate ligaments and urge the two facsimiles together. Typically, these facsimiles are unitary pieces comprised of a material strong enough to withstand being put under tension without snapping, yet soft enough to be cut, filed, and / or drilled by a surgeon. Because the facsimiles are unitary pieces, the whole device must be replaced for each new training exercise. Additionally, surgeons are making more frequent use of robotics, which may help provide more accurate knee repair and replacements. Robotic surgery techniques use sophisticated hardware trackers, including bone pins, that attach to the facsimile femur and facsimile tibia, which are then tracked using cameras or fluoroscopes to provide real time digital information as to exactly where the implants will fit onto the facsimiles. When using robotic surgery techniques with known facsimiles, movement of the material under tension may deform, which in turn may cause the bone pins to move. This may cause errors in the tracking, which may result in the training exercise having to be restarted. It is desirable to provide an improved orthopaedic training aid capable of withstanding tension, whilst still being usable as a tool for surgeons to cut, file, and / or drill. In a first aspect, the present invention provides an orthopaedic training device for use as a training aid for surgical orthopaedic techniques, the device comprising a facsimile of the distal portion of a femur, and a facsimile of the proximal portion of a tibia, which together form a facsimile knee joint, wherein: the facsimile of the distal portion of the femur comprises a femur diaphysis portion, a femur metaphysis portion integrally attached to the femur diaphysis portion, and a femur epiphysis portion releasably attachable to the femur metaphysis portion; the facsimile of the proximal portion of the tibia comprises a tibia diaphysis portion, a tibia metaphysis portion integrally attached to the tibia diaphysis portion, and a tibia epiphysis portion releasably attachable to the tibia metaphysis portion; and wherein the femur diaphysis portion, femur metaphysis portion, tibia diaphysis portion and the tibia metaphysis portion are comprised of a first material having a first hardness, the femur epiphysis portion is comprised of a second material having a second hardness, and the tibia epiphysis portion is comprised of a third material having a third hardness, the first hardness being greater than the second hardness and the third hardness. In this way, the facsimiles each include a first part formed of the respective diaphysis portion and the metaphysis portion, and a second part formed of the respective epiphysis portion. The first part of each facsimile may be formed of a relatively hard material, such that the first part may be substantially resilient to tensional forces applied to the training aid. The second part of each facsimile may be formed of a material softer than that of the first part, to closely resemble human epiphysis bone that may be cut, filed and / or drilled by a surgeon. Consequently, the first part may be reusable for multiple training exercises, with only the second part needing to be replaced for each new exercise. Additionally, when used in procedures including robotic techniques, with bone pins, or other trackers, attached to the relatively hard first parts, the chance of unwanted movement of the bone pins within the material is reduced, lowering the risk of having to restart training procedures. Moreover, the femur epiphysis portion and tibia epiphysis portion may each have a different hardness, allowing for different hardnesses between each facsimile to be used in a training procedure. The different hardness may reflect different diseased or worn epiphysis portions. Anatomically, the distal portion of a femur is the end portion of the femur located away from the hip joint, and the proximal portion of a tibia is the end portion adjacent to the knee joint. It will be appreciated that the diaphysis portions, metaphysis portions, and epiphysis portions of the facsimiles may not relate directly to the anatomical definitions of these parts. For example, the metaphysis portions may include a proportion of the epiphysis portions, or vice versa. Additionally, the respective epiphysis portions may overlap the respective metaphysis portions. The hardness of each portion may be in relation the Shore Hardness Scale. The femur metaphysis portion and the femur diaphysis portion may have the same hardness. The tibia metaphysis portion and the tibia metaphysis portion may have the same hardness. The facsimile of the distal portion of the femur may be part of a facsimile of a whole human femur. The facsimile of the proximal portion of the tibia may be part of a facsimile of a whole human tibia. The femur diaphysis portion and the femur metaphysis portion may be approximately the same length, measured parallel to the longitudinal axis of the facsimile of the distal portion of the femur. The femur epiphysis portion may be approximately double the length of the femur diaphysis portion or the femur metaphysis portion, measured parallel to the longitudinal axis of the facsimile of the distal portion of the femur. The total length of the facsimile of the distal portion of the femur may be between 150mm and 300mm. Lengths either side of this range are also contemplated, for example, 100mm, or 350mm. The tibia diaphysis portion may be approximately four times the length of the tibia metaphysis portion measured parallel to the longitudinal axis of the facsimile of the proximal portion of the tibia. The tibia epiphysis portion may be double the length of the tibia metaphysis portion measured parallel to the longitudinal axis of the facsimile of the proximal portion of the tibia. The total length of the facsimile of the proximal portion of the tibia may be between 100mm and 25mm. Lengths either side of this range are also contemplated, for example, 50mm, or 300mm. The facsimile of the distal portion of the femur, located on the femur diaphysis portion or the femur metaphysis portion, may comprise a first attachment means, and the facsimile of the proximal portion of the tibia, located on the tibia diaphysis portion or the tibia metaphysis portion, may comprise a second attachment means, and wherein the orthopaedic training device may further comprise a tensioning means attachable between the first and second attachment means for urging the facsimile of the distal portion of the femur towards the facsimile of the proximal portion of the tibia. In this way, the tensioning means may be attached to the parts of the training aid having the greater hardness, rather than the parts having a lower hardness. By doing this, the tensioning means is less likely to move or come loose in use, as a result of deformation of the material, and so the facsimiles are less likely to move apart. Additionally, by attaching the tensioning means to the diaphysis portion or metaphysis portion rather than the epiphysis portion, the tensioning means is kept further away from the surgeon’s area of operation, lowering the chances of the tensioning means being inadvertently cut or otherwise damaged by the surgical tools. Moreover, the femur and tibia epiphysis portions may be comprised of relatively soft materials, having a low hardness, to replicate a greater variety of bone types than may not be possible with known facsimiles. For example, facsimiles representing soft bones resulting from age or disease may be used. This is because the part being practiced on by the surgeon may not be under the majority of the tensioning load, in use, and therefore a comprise in hardness to prevent the training aid snapping may not be required. If a cord is utilised in the tensioning means, attachment to a relatively soft material may result in the cord moving within the material, or otherwise cutting into the material. This may result in the tension reducing throughout the course of the procedure, or in altering the relative orientation of the facsimiles, both of which may be detrimental to the training exercise. By using the first and / or second attachment means on the respective diaphysis portion or metaphysis portion of the facsimiles of the first aspect, the risk of reduced tensioning and / or altered relative orientations of the facsimiles may be reduced. The first attachment means and / or the second attachment means may be arranged to releasably attach the tensioning means to the respective facsimile. In this way, if the tensioning means is damaged during a training procedure by a surgeon’s tools, only the tensioning aid may need to be replaced, rather than the whole training aid. The first and / or second attachment means may comprise a slot, the tensioning means may comprise a cord having a ferrule, the ferrule having a diameter greater than the diameter of the slot, and in use the ferrule may be prevented from passing through the slot. The cord may pass through the slot but the ferrule may not. The cord may be elasticated. In this way, the tensioning means may be relatively quickly released from the training aid simply by releasing the tension and removing the ferrule from the slot. The first and / or second attachment means may comprise a guide means, wherein the guide means may be configured to allow the tensioning means to pass through the guide means to an external device for providing tension to the tensioning means. In this way, the guide means may be located at a point on the diaphysis portion or metaphysis portion of the respective facsimile wherein the direction of tension applied by the tensioning means may accurately replicate the direction in which a ligament may tension a human knee joint. The facsimile of the distal portion of the femur may comprise a first bore extending through the femur metaphysis portion and the femur diaphysis portion, and the facsimile of the proximal portion of the tibia may comprise a second bore extending through the tibia metaphysis portion and the tibia diaphysis portion, wherein the cross-sectional area at one end of the first and second bores may be greater than the cross-sectional area at a second end of the first and second bores. In this way, the first and second bores may provide a relatively large hollow space within the respective diaphysis portions and metaphysis portions in which a surgeon may insert a rod as part of a “revision” knee replacement procedure. Because the respective diaphysis portions and metaphysis portions may be reused, the first and second bores may reduce the chance of the surgeon accidentally damaging these portions when inserting a rod. The relatively large hollow space may allow a certain degree of freedom and margin for error. The greatest diameter of the first and / or second bore may be substantially larger than the diameter of the rod. It will be appreciated that the surgeon may still drill through the relatively soft material of the respective epiphysis portions. The greatest cross-sectional area of the first bore may be located in the femur metaphysis portion, and the greatest cross-sectional area of the second bore may be located in the tibia metaphysis portion. In this way, the hollow space may be further maximised by approximately reflecting the proportions of the facsimile of the distal portion of the femur and the facsimile of the proximal portion of the tibia. The facsimile of the distal portion of the femur may include a first securing means for releasably securing the femur metaphysis portion to the femur epiphysis portion. In this way, the femur epiphysis portion may be prevented from releasing from the femur metaphysis portion in use. For example, the first securing means may prevent the release of the femur epiphysis portion in a direction radially from the longitudinal axis of the facsimile of the distal portion of the femur, or in a direction away from the femur metaphysis portion. The femur epiphysis portion and the femur metaphysis portion may be configured to separate by the application of a force applied approximately parallel to the longitudinal length of the facsimile of the distal portion of the femur. Opposing forces may be applied to the femur epiphysis portion and the femur metaphysis portion, to thereby separate them. In this way, the femur epiphysis portion may only be released from the femur metaphysis portion by actively applying a directional release force to the femur epiphysis portion and / or the femur metaphysis portion. The directional release force may be in a different direction to a surgical force applied to the femur epiphysis portion, such as a force applied by a surgeon cutting, drilling, reaming, and / or filing. Alternatively, the directional release force may be in the same direction as a surgical force, but may require a greater force than the average surgical force applied by a surgeon using tools during a procedure. As such, the femur epiphysis portion and the femur metaphysis portion may be less likely to accidently or inadvertently release from each other, in use. It will be appreciated that alternatively, the femur epiphysis portion and the femur metaphysis portion may be configured to separate by the application of a force applied approximately perpendicular to the longitudinal axis of the facsimile of the distal portion of the femur. Opposing forces may be applied to the femur epiphysis portion and the femur metaphysis portion, to thereby separate them. Other directions are also contemplated, such as angles between 0 degrees and 90 degrees from the longitudinal axis of the facsimile of the distal portion of the femur. The first securing means may comprise an interference fit or a snap fit between the femur metaphysis portion and the femur epiphysis portion. In this way, a relatively large force may be required to release the femur epiphysis portion from the femur metaphysis portion, reducing the risk of the two portions inadvertently moving relative to each other during use. The interference or snap fit may be possible due to the resilience of the femur epiphysis portion; the femur epiphysis portion may be comprised of a material capable of elastically deforming to receive, or be removed from, the femur metaphysis portion. It will be appreciated that other means of preventing inadvertent movement of the femur epiphysis portion relative to the femur metaphysis portion are also contemplated, such as screws, bolts, hook and loop fixings, and / or adhesives. The first securing means may comprise at least one projection extending from one of the femur metaphysis portion and the femur diaphysis portion, and a cavity located in the other of the femur epiphysis portion and the femur diaphysis portion, wherein, in use, the projection may be arranged to be releasably receivable within the cavity. In this way, a projection within a cavity may prevent the movement of the femur epiphysis portion in at least one radial direction relative to the longitudinal axis of the facsimile of the distal portion of the femur. The first securing means may comprise one projection and one cavity, or a plurality of projections and a plurality of cavities. The cross-sectional area of the projection may be slightly less than the cross-sectional area of the cavity, to enable the projection to be received within the cavity. The facsimile of the proximal portion of the tibia includes a second securing means for releasably securing the tibia metaphysis portion to the tibia epiphysis portion. In this way, the tibia epiphysis portion may be prevented from releasing from the tibia metaphysis portion in use. For example, the first securing means may prevent the release of the tibia epiphysis portion in a direction radially from the longitudinal axis of the facsimile of the proximal portion of the tibia, or in a direction away from the tibia metaphysis portion. The tibia epiphysis portion and the tibia metaphysis portion may be configured to separate by the application of a force applied approximately perpendicular to the longitudinal length of the facsimile of the proximal portion of the tibia. Opposing forces may be applied to the tibia epiphysis portion and the tibia metaphysis portion, to thereby separate them. In this way, the tibia epiphysis portion may only be released from the tibia metaphysis portion by actively applying a directional release force to the tibia epiphysis portion and / or the tibia metaphysis portion. The directional release force may be in a different direction to a surgical force applied to the tibia epiphysis portion by a surgeon cutting, drilling, reaming, and / or filing. Alternatively, the directional release force may be in the same direction as a surgical force, but may require a greater force than the average surgical force applied by a surgeon using tools during a procedure. As such, the tibia epiphysis portion and the tibia metaphysis portion may be less likely to accidently or inadvertently release from each other, in use. It will be appreciated that alternatively, the tibia epiphysis portion and the tibia metaphysis portion may be configured to separate by the application of a force applied approximately parallel to the longitudinal axis of the facsimile of the proximal portion of the tibia. Opposing forces may be applied to the tibia epiphysis portion and the tibia metaphysis portion, to thereby separate them. Other directions are also contemplated, such as angles between 0 degrees and 90 degrees from the longitudinal axis of the facsimile of the proximal portion of the tibia. The second securing means may be arranged to enable the tibia metaphysis portion to be releasably slidably engageable with the tibia metaphysis portion. In this way, the tibia epiphysis portion may be relatively quickly attached and detached from the tibia metaphysis portion. A channel may be provided within one of the tibia epiphysis portion and the tibia metaphysis portion, and a rail may be provided extending from the other of the tibia epiphysis portion and the tibia metaphysis portion, wherein the rail may be arranged to be slidably engageable within the channel. The opening of the channel may be configured to prevent the rail from disengaging from the channel in a direction perpendicular to the sliding direction. This may be achieved by the opening having a width less than the central portion of the rail, such that the rail may not be able to fit through the opening. The second securing means may comprise an anti-sliding means for preventing the separation of the tibia epiphysis portion from the tibia metaphysis portion in a direction parallel to the sliding direction. In this way, the tibia epiphysis may be prevented from disengaging from the tibia metaphysis portion in a sliding manner, in use, without a user actively releasing the antisliding means. The anti-sliding means may comprise a nub arranged on one of the tibia epiphysis portion and the tibia metaphysis portion, and a recess arranged in the other of the tibia epiphysis portion and the tibia metaphysis portion, wherein in use, the nub may be arranged to be receivable within the recess to prevent sliding movement, and pullable from the recess in a direction perpendicular to the sliding direction to enable sliding movement. In this way, a user may have to manipulate the tibia epiphysis portion from the tibia metaphysis portion in a specific way to engage or disengage the locking mechanism. For instance, one of the tibia epiphysis portion and the tibia metaphysis portion may comprise a tab for a user to lift and / or press to engage and / or disengage the nub from the recess. The first tibia metaphysis portion and the tibia epiphysis portion may comprise a stabilising means for preventing rotational movement of the tibia epiphysis portion relative to the tibia metaphysis portion, about at least one axis perpendicular to the longitudinal axis of the facsimile of the proximal portion of the tibia. In this way, unwanted movement between the tibia epiphysis portion and the tibia metaphysis portion, in use, may be reduced, such that the training aid may more accurately reflect a human bone, which it will be appreciated does not have separate parts which may rotate or otherwise move relative to each other. Rotational movement may occur because the tibia epiphysis portion may be comprised of a material being relatively elastically deformable, and / or because the connection between the tibia epiphysis portion and the tibia metaphysis portion is not as rigid as the if the facsimile of the proximal portion of the tibia comprised one unitary piece. The stabilising means may be configured to engage simultaneously when the tibia epiphysis portion is engaged with the tibia metaphysis portion. An anti-lift means may be arranged to prevent the tibia epiphysis portion from moving away from the tibia metaphysis portion in a direction perpendicular to the sliding direction. If the channel and rail are utilised to enable the sliding movement, and the channel passes through the second bore, in a direction substantially perpendicular to the longitudinal axis of the facsimile of the proximal portion of tibia, one end of the rail may be suspended within the second bore, and not connected to the channel. As such, only a relatively small area of the engagement between the rail and the channel, resulting in a potentially weak connection. If the tibia epiphysis portion is comprised of a material being relatively elastically deformable, the tibia epiphysis portion may be susceptible to unwanted rotation in a direction perpendicular to the sliding movement. As such, the anti-lift means may be provided to counter the unwanted rotation. The anti-lift means may comprise a socket located in the end of one of the channel and the rail, and a protrusion extending from the end of the other of the channel and the rail, wherein, in use, the protrusion is engageable within the socket. In this way, the end of the rail comprising the socket or protrusion may be prevented from rotating out of the channel. It will be appreciated that alternatively, the facsimile of the distal portion of the femur may instead comprise the second securing means, and the facsimile of the proximal portion of the tibia may instead comprise the first securing means. The first material may have a first density, the second material may have a second density, and the third material may have a third density, wherein the first density may be greater than the second and third densities. The second density may be the same as the third density. The first material may comprise a relatively rigid plastic, and the second material and third material may both comprise open or closed cell foam. Neither of the femur epiphysis portion nor the tibia epiphysis portion may include an attachment means for attaching the tensioning means. In this way, the tensioning means may only be connected to the part of the facsimiles comprised of a relatively hard material, to reduce the likelihood of the tensioning means moving within, or damaging, the softer material. Additionally, this may reduce the risk of the tensioning means being accidently cut or otherwise damaged by surgical tools acting on the epiphysis portions. In a second aspect, there is provided an orthopaedic training system for use as a training aid for surgical orthopaedic techniques, the system comprising the orthopaedic training device of the first aspect, and a support structure arranged to hold the facsimile of the distal portion of the femur adjacent to the facsimile of the proximal portion of the tibia, to thereby form a facsimile knee joint having the correct relative anatomical orientation. In a third aspect, the present invention provides an orthopaedic training device for use as a training aid for surgical orthopaedic techniques, the device comprising a facsimile of the distal portion of a femur, and a facsimile of the proximal portion of a tibia, which together form a facsimile knee joint, wherein: the facsimile of the distal portion of the femur comprises a femur diaphysis portion, a femur metaphysis portion integrally attached to the femur diaphysis portion, and a femur epiphysis portion releasably attachable to the femur metaphysis portion; and the facsimile of the proximal portion of the tibia comprises a tibia diaphysis portion, a tibia metaphysis portion integrally attached to the tibia diaphysis portion, and a tibia epiphysis portion releasably attachable to the tibia metaphysis portion. Any of the features described above in relation to the first aspect may be incorporated, individually or combination, with the third aspect. The first material having a first hardness, the femur epiphysis portion is comprised of a second material having a second hardness, and the tibia epiphysis portion is comprised of a third material having a third hardness, the first hardness being greater than the second hardness and the third hardness. The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings. Figure 1 is a facsimile knee joint; Figure 2 is the facsimile of the distal portion of a femur of Figure 1, in a plane parallel to the coronal plane of a human body; Figure 3 is the facsimile of Figure 2, in a plane parallel to the sagittal plane of a human body; Figure 4 is a cross-sectional view of the femur diaphysis portion and the femur metaphysis portion of Figure 2 in a plane parallel to the coronal plane of a human body; Figure 5 is a bottom view of the femur epiphysis portion, in a plane perpendicular to the longitudinal axis of the femur facsimile; Figure 6 is the facsimile of the proximal portion of a tibia facsimile, in a plane parallel to the coronal plane of a human body; Figure 7 is the facsimile of Figure 6, in a plane parallel to the sagittal plane of a human body; Figure 8 shows a cross-sectional view of the tibia diaphysis portion and the tibia metaphysis portion of Figure 6 in a plane parallel to the coronal plane of a human body; and Figure 9 shows a cross-sectional view of the tibia epiphysis portion of Figure 6 in a plane parallel to the coronal plane of a human body. The present invention will be described with respect to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. Each drawing may not include all of the features of the invention and therefore should not necessarily be considered to be an embodiment of the invention. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other sequences than described or illustrated herein. Likewise, method steps described or claimed in a particular sequence may be understood to operate in a different sequence. Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that operation is capable in other orientations than described or illustrated herein. It is to be noticed that the term “comprising”, used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B. Reference throughout this specification to “an embodiment” or “an aspect” means that a particular feature, structure or characteristic described in connection with the embodiment or aspect is included in at least one embodiment or aspect of the present invention. Thus, appearances of the phrases “in one embodiment”, “in an embodiment”, or “in an aspect” in various places throughout this specification are not necessarily all referring to the same embodiment or aspect, but may refer to different embodiments or aspects. Furthermore, the particular features, structures or characteristics of any one embodiment or aspect of the invention may be combined in any suitable manner with any other particular feature, structure or characteristic of another embodiment or aspect of the invention, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments or aspects. Similarly, it should be appreciated that in the description various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Moreover, the description of any individual drawing or aspect should not necessarily be considered to be an embodiment of the invention. Rather, as the following claims reflect, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention. Furthermore, while some embodiments described herein include some features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form yet further embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination. In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practised without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. In the discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value. The use of the term “at least one” may mean only one in certain circumstances. The use of the term “any” may mean “all” and / or “each” in certain circumstances. The principles of the invention will now be described by a detailed description of at least one drawing relating to exemplary features. It is clear that other arrangements can be configured according to the knowledge of persons skilled in the art without departing from the underlying concept or technical teaching, the invention being limited only by the terms of the appended claims. Figure 1 shows a facsimile knee joint 100, for use as a training aid for surgical orthopaedic techniques. The facsimile knee joint 100 is shown to include a facsimile of the distal portion of a femur, hereinafter termed the femur facsimile 200, and a facsimile of the proximal portion of a tibia, hereinafter termed the tibia facsimile 300. The tibia facsimile 300 is arranged below the femur facsimile 200, and the longitudinal axes of the femur and tibia facsimiles 200, 300 are orientated approximately 120 degrees to each other, wherein the longitudinal axes of the femur facsimile 200 and tibia facsimile 300 each extend in a direction parallel to the anatomic axis of the respective facsimile 200, 300. In this way, the facsimile knee joint 100 is shown to be in a correct relative anatomical orientation. The facsimile knee joint 100 is supported on a support structure 400, connected to the lower end of the tibia facsimile 300. A tensioning means 500 is connected to the support structure 400. The tensioning means 500 includes a tensioning cord 510 having a ferrule 515 on one end, and a tightening mechanism 520 for applying or removing tension to the tensioning cord 510. The tightening mechanism comprises a substantially square main bracket 522 extending away from the support structure, a threaded aperture 524 within the centre of the main bracket 522, a threaded bolt 526 inserted within the threaded aperture 524, and a ferrule holder 528 connected to the end of the threaded bolt 526. The ferrule holder 528 is shown to be U-shape, and includes a slot on one side, and a hole on the other side, in which an end of the threaded bolt 526 is located. The tensioning cord 510 is shown to be attached to the femur facsimile 200, and to the tibia facsimile 300. These attachments are discussed in more detail below. The ferrule 515 is located in the ferrule holder 528, with a portion of the tensioning cord 310 located in the slot of the ferrule holder 528, such that the tensioning cord 510 is further attached to the tensioning mechanism 520. A second tensioning means (not shown) may also be provided, located on the opposite side of the facsimile knee joint 100. In use, rotating the threaded bolt 526 clockwise may pull the tensioning cord 510 taut, thereby urging the femur facsimile 200 and the tibia facsimile 300 together. In this way, the tensioning means 500 may simulate the tension provided by ligaments in a human knee joint. Rotating the threaded 526 anti-clockwise may release tension, such that the femur facsimile 200 and tibia facsimile 300 may be disconnected after use. When tensioned, a surgeon may carry out surgical techniques on the facsimile knee joint 100 as they would on a human knee joint. Figure 2 shows an isolated femur facsimile 200, in a plane parallel to the coronal plane of a human body. The femur facsimile 200 has the general shape of the distal portion of a human femur, including a narrow shaft portion at one end, and a gradually increasing taper towards two generally bulbous lobes 201 at the other end. The femur facsimile 200 includes a femur square shaft 210 located at the end the femur facsimile 200 opposite to the end arranged adjacent to the tibia facsimile 300, in use (as shown in Figure 1). The femur square shaft 210 extends parallel to the longitudinal axis of the femur facsimile 200. In use, the femur square shaft 210 may be connected to a second support structure (not shown). A femur diaphysis portion 220 is connected to the femur shaft 210, extending parallel to the longitudinal axis of the femur facsimile 200. The femur diaphysis portion 220 is shown to have a substantially square cross-section, which is greater than the cross-sectional area of the femur square shaft 210. In this way, the second support structure may attach to the femur square shaft 210 and abut against the femur diaphysis portion 220, thereby preventing the femur facsimile 200 from sliding progressively further onto the second support structure when tension is applied, in use. The shape of the femur diaphysis portion 220 is generally cuboidal. A femur metaphysis portion 230 is also shown, adjacent to the femur diaphysis portion 220. The femur metaphysis portion 230 begins at the point that the cross-sectional area of the femur facsimile 200 begins to taper and increase. It will be appreciated that there may be a degree of overlap where the femur diaphysis portion 220 transitions into the femur metaphysis portion 230, depending on the exact shape of the femur facsimile 200. The width of the femur metaphysis portion 230 is narrowest at the end of the femur metaphysis portion 230 adjacent to the femur diaphysis portion 220. Together, the femur diaphysis portion 220 and the femur metaphysis portion 230 form a unitary part. Also shown is a femur epiphysis portion 240. The femur epiphysis portion 240 is shown to be connected to the end of the femur metaphysis portion 230 opposite to the end adjacent to the femur diaphysis portion 220. The femur epiphysis portion 240 includes the two generally bulbous lobes 201 of the femur facsimile 200. Moreover, the femur epiphysis portion 240 is shown to overlap the end of the femur metaphysis portion 230 opposite to the end adjacent to the femur diaphysis portion 220. It will be appreciated that there may be a degree of overlap where the femur epiphysis portion 240 transitions into the femur metaphysis portion 230, depending on the exact shape of the femur facsimile 200. The femur epiphysis portion 240 is arranged to be releasably attachable to the femur metaphysis portion 230. Figure 3 shows an isolated femur facsimile 200, in a plane parallel to the sagittal plane of a human body. The femur epiphysis portion 240 is shown to be generally U-shape in this plane. The internal area of the U-shape defines a cavity 250. A projection 260 is shown to extend from the femur metaphysis portion 230, in a direction away from the femur diaphysis portion 220. Whilst not shown in Figure 3, a second projection is also present. In Figure 2, the outer edge of each projection 260 are shown protruding from behind the femur epiphysis portion 240. The projection 260 shown in Figure 3 is located within the cavity 250, and the external dimensions and shape of the projection 260 are shown to substantially match the dimensions and shape of the cavity 250. The connection of the projection 260 within the cavity 250 may be an interference fit or a snap fit. However, it will be appreciated that other securing means are also contemplated, such as a screw or bolt. It will also be appreciated that each projection 260 may be insertable into separate cavities 250. A slot 270 is located in the projection 260. In use, the slot 270 may receive the tensioning cord 510, as shown in Figures 1 and 2. Figure 4 shows a cross-sectional view of the femur diaphysis portion 220 and the femur metaphysis portion 230 in a plane parallel to the coronal plane of a human body, but upside down compared to a human being. The two projections 260 are fully shown in this view, each spaced apart from the other, and each extending from the end of the femur metaphysis portion 230 opposite to the end adjacent to the femur diaphysis portion 220. A first bore 280 is shown to extend vertically through the centre of the femur diaphysis portion 220 and the femur metaphysis portion 230. The width of the first bore 280 is greatest at the end of the femur metaphysis portion 230 adjacent to the two projections 260. The width of the first bore 280 is narrowest at the end of the femur facsimile 200 comprising the femur square shaft 210. The cross-sectional shape of the first bore 280 may be, for example, circular, square, or oval. Alternatively, the cross-sectional shape of the first bore 280 may be irregular, and formed to match the outside cross-sectional shape of the femur facsimile 200. In use, a surgeon may drill a hole within the femur epiphysis portion 230, from the top to the bottom of the femur epiphysis portion 230, and insert a rod through the hole and into the first bore 280. The diameter of the rod may be substantially less than the greatest diameter of the first bore 280. In this way, a margin of error is provided if the surgeon inserts the rod at the wrong position, or at the wrong angle. This may reduce the risk of the surgeon accidentally damaging the internal surface of the femur metaphysis portion 230 and / or femur diaphysis portion 220 when inserting a rod. A void 290 is provided between the two projections 260, and adjacent to the end of the first bore 280 having the greatest width. In use, a section of the femur epiphysis portion 240 located between the two cavities 250 may be receivable within the void 290 when the femur epiphysis portion 240 is connected to the femur metaphysis portion 230. In this way, movement of the femur epiphysis portion 230 relative to the femur metaphysis portion 240 may be prevented in all radial directions from the longitudinal axis of the femur facsimile 200. Figure 5 is a bottom view of the femur epiphysis portion 240, in a plane perpendicular to the longitudinal axis of the femur facsimile 200. The bottom of the femur epiphysis portion 240 is the side which, in use, connects to the femur metaphysis portion 230. The lobes 201 are shown extending from the top left and top right of the femur epiphysis 240, respectively. A protuberance 245 is located in the centre of the femur epiphysis portion 240. The two cavities 250 are shown as recesses to the left and right of the protuberance 245 such that the protuberance 245 and the two recesses are aligned along a central axis which is parallel to the coronal plane with the femur in a vertical orientation (in a hypothetical with the human body standing up). In use, when the femur epiphysis portion 240 is secured to the femur metaphysis portion 230, the protuberance 245 may fill the void 290 in the femur metaphysis portion 230, such that the protuberance 245 may be unable to move within the void 290, in any direction extending radially from the longitudinal axis of the femur facsimile 200. Figure 6 shows an isolated tibia facsimile 300, in a plane parallel to the coronal plane of a human body, in the correct orientation compared to a human being. The tibia facsimile 300 has the general shape of the proximal portion of a human tibia, including a narrow shaft portion at one end, and a gradually increasing taper towards two generally concave portions 301 at the other end, as more clearly shown in Figure 1. The taper of the tibia facsimile 300 is greater than the taper of the femur facsimile 200. The tibia facsimile 300 includes a tibia square shaft 310 located at the end the tibia facsimile 300 opposite to the end arranged adjacent to the tibia facsimile 200, in use (as shown in Figure 1). The tibia square shaft 310 extends parallel to the longitudinal axis of the tibia facsimile 300. In use, the tibia square shaft 310 is connectable to the support structure 400. A tibia diaphysis portion 320 is connected to the tibia square shaft 310, extending parallel to the longitudinal axis of the tibia facsimile 300. The tibia diaphysis portion 320 has a substantially square cross-section, which is greater than the cross-sectional area of the tibia square shaft 310. In this way, the support structure 400 may attach to the tibia square shaft 310 and abut against the tibia diaphysis portion 320, thereby preventing the tibia facsimile 300 from sliding progressively further onto the support structure 400 when tension is applied, in use. The shape of the tibia diaphysis portion 320 is generally cuboidal. A tibia metaphysis portion 330 is also shown, adjacent to the tibia diaphysis portion 320. The tibia metaphysis portion 330 begins at the point that the cross-sectional area of the tibia facsimile 300 begins to taper and increase. It will be appreciated that there may be a degree of overlap where the tibia diaphysis portion 320 transitions into the tibia metaphysis portion 330, depending on the exact shape of the tibia facsimile 300. The width of the tibia metaphysis portion 330 is narrowest at the end of the tibia metaphysis portion 330 adjacent to the tibia diaphysis portion 320. Together, the tibia diaphysis portion 320 and the tibia metaphysis portion 330 form a unitary part. Also shown is a tibia epiphysis portion 340. The tibia epiphysis portion 340 is shown to be connected to the end of the tibia metaphysis portion 330 opposite to the tibia diaphysis portion 320. The tibia epiphysis portion 340 includes the two generally concave portions 301 of the tibia facsimile 300. The tibia epiphysis portion 340 is arranged to be releasably securable to the tibia metaphysis portion 330. A first channel 350 is shown within the end of the tibia metaphysis portion 340 opposite the end adjacent to the tibia diaphysis portion 320. The first channel 350 has a substantially semi-circular cross-section, and the first channel 350 extends in a direction perpendicular to the longitudinal axis of the tibia facsimile 300. The tibia epiphysis portion 340 comprises a first rail 360 having a cross-section with a shape and dimensions substantially matching the shape and dimensions of the cross-section of the first channel 350. In this way, the first rail 360 may be slideable within the first channel 350 to secure the tibia epiphysis 340 to the tibia metaphysis 330. An opening 355 of the first channel 350 extends across the end of the tibia metaphysis portion 340 opposite the end adjacent to the tibia diaphysis portion 320. The width of the opening 355 is narrower than the width of the central portion of the first rail 360. In this way, the tibia epiphysis portion 340 may be prevented from being detached from the tibia metaphysis portion 330 in a direction parallel to the longitudinal axis of the tibia facsimile 300. Guide slots 370 are shown to be located on the tibia diaphysis portion 320, and the tibia metaphysis portion 330. The guide lots 370 are shown to be located on opposite sides of the tibia facsimile 300 to each other. The guide slots 370 are orientated such that the length of the guide slots 370 extend in a direction parallel to the longitudinal axis of the tibia facsimile 300. The width of the guide slots 370 may be narrower than the diameter of the tensioning cord 510. In this way, the tensioning cord 510 may be clamped within the guide slots 370, to prevent the tensioning cord 510 from releasing from the guide slots 370 in use. Alternatively, a lip 373 (Figure 6) may extend into the guide slots 370, to act to hook the tensioning cord 510 to prevent the tensioning cord 510 from releasing from the guide slots 370 in use. Figure 7 shows an isolated femur facsimile 300, in a plane parallel to the sagittal plane of a human body. An internal view (in broken lines) of the tibia metaphysis portion 330 shows the first rail 360 within the first channel 370. The first rail 360 includes a protrusion 365 extending from one end of the first rail 360 in a direction perpendicular to the longitudinal axis of the tibia facsimile 300. A socket 375 is located within an internal surface of the tibia metaphysis portion 330, adjacent to the protrusion 365. In use, with the tibia epiphysis portion 340 secured on the tibia metaphysis portion 330, the protrusion 365 is located within the socket 375. In this way, the tibia epiphysis portion 340 may be prevented from rotating in a clockwise direction away from the tibia metaphysis portion 330 in the sagittal plane. Also shown is a nub 305 extending from the first rail 360 in a direction away from the tibia epiphysis portion 340. When the tibia epiphysis portion 340 is secured to the tibia metaphysis portion 330, the nub 305 may be located within a recess (not shown) within the tibia metaphysis portion 330. In this way, the nub 305 may prevent relative sliding movement between the tibia epiphysis portion 340 and the tibia metaphysis portion 330. To enable relative sliding movement between the tibia epiphysis portion 340 and the tibia metaphysis portion 330, a user may very slightly rotate the tibia epiphysis portion 340 in an anti-clockwise direction, to release the nub 305 from the recess, before sliding the tibia epiphysis portion 340 relative to the tibia metaphysis portion 330 in the sagittal plane. Figure 8 shows a cross-sectional view of the tibia diaphysis portion 320 and the tibia metaphysis portion 330 in a plane parallel to the coronal plane of a human body, and Figure 9 shows a cross-sectional view of the tibia epiphysis portion 340 in a plane parallel to the coronal plane of a human body. A second bore 380 is shown to extend through the centre of the tibia diaphysis portion 320 and the tibia metaphysis portion 330. The width of the second bore 380 is greatest at the end of the tibia metaphysis portion 330 adjacent to the channel 350. The width of the second bore 380 is narrowest at the end of the tibia facsimile 300 comprising the tibia square shaft 310. The cross-sectional shape of the second bore 380 may be, for example, circular, square, or oval. Alternatively, the cross-sectional shape of the second bore 380 may be irregular, and formed to match the cross-sectional shape of the tibia facsimile 300. In use, a surgeon may drill a hole within the tibia epiphysis portion 330, and insert a rod through the hole, and into the second bore 380. The diameter of the rod may be substantially less than the greatest diameter of the second bore 380. In this way, a margin of error is provided if the surgeon inserts the rod at the wrong position or at the wrong angle, and may reduce the risk of the surgeon accidentally damaging the internal surface of the tibia metaphysis portion 330 and / or tibia diaphysis portion 320 when inserting a rod. A second channel 390 is also shown. The second channel 390 is located on the end of the tibia metaphysis portion 340 opposite the end adjacent to the tibia metaphysis portion 330, but spaced away from the first channel 350. A second rail 395 is shown extending from the tibia epiphysis in Figure 9, in a direction approximately 90 degrees 5 from the direction in which the first rail 360 extends. When the tibia epiphysis portion 340 is secured to the tibia metaphysis portion 330, in use, the second rail 395 will be located within the second channel 390. In this way, the tibia epiphysis portion 340 will be prevented from rotating in an anti-clockwise direction relative to the tibia metaphysis portion 330, thereby stabilising the tibia epiphysis portion 340, in use. 10 The facsimile knee joint 100 may be used by a surgeon as a training aid for repairing and / or replacing knee joint. The respective epiphysis portions and metaphysis portions may be reused for multiple procedures, and only the respective epiphysis portions may be replaced for each procedure. 15

Claims

1. An orthopaedic training device for use as a training aid for surgical orthopaedic techniques, the device comprising a facsimile of the distal portion of a femur, and a facsimile of the proximal portion of a tibia, which together form a facsimile knee joint, wherein:the facsimile of the distal portion of the femur comprises a femur diaphysis portion, a femur metaphysis portion integrally attached to the femur diaphysis portion, and a femur epiphysis portion releasably attachable to the femur metaphysis portion;the facsimile of the proximal portion of the tibia comprises a tibia diaphysis portion, a tibia metaphysis portion integrally attached to the tibia diaphysis portion, and a tibia epiphysis portion releasably attachable to the tibia metaphysis portion; andwherein the femur diaphysis portion, femur metaphysis portion, tibia diaphysis portion and the tibia metaphysis portion are comprised of a first material having a first hardness, the femur epiphysis portion is comprised of a second material having a second hardness, and the tibia epiphysis portion is comprised of a third material having a third hardness, the first hardness being greater than the second hardness and the third hardness.

2. The orthopaedic training device of claim 1, wherein the facsimile of the distal portion of the femur, located on the femur diaphysis portion or the femur metaphysis portion, comprises a first attachment means, and the facsimile of the proximal portion of the tibia, located on the tibia diaphysis portion or the tibia metaphysis portion, comprises a second attachment means, and wherein the orthopaedic training device further comprises a tensioning means attachable between the first and second attachment means for urging the facsimile of the distal portion of the femur towards the facsimile of the proximal portion of the tibia.

3. The orthopaedic training device of claim 2, wherein the first attachment means and / or the second attachment means is arranged to releasably attach the tensioning means to the respective facsimile.

4. The orthopaedic training device of claim 3, wherein the first and / or second attachment means comprises a slot, the tensioning means comprises a cord having aferrule, the ferrule having a diameter greater than the diameter of the slot, and in use the ferrule is prevented from passing through the slot.

5. The orthopaedic training device of any preceding claim, wherein the first and / or second attachment means comprises a guide means, wherein the guide means is configured to allow the tensioning means to pass through the guide means to an external device for providing tension to the tensioning means.

6. The orthopaedic training device of any preceding claim, wherein the facsimile of the distal portion of the femur comprises a first bore extending through the femur metaphysis portion and the femur diaphysis portion, and the facsimile of the proximal portion of the tibia comprises a second bore extending through the tibia metaphysis portion and the tibia diaphysis portion, wherein the cross-sectional area at one end of the first and second bores is greater than the cross-sectional area at a second end of the first and second bores.

7. The orthopaedic training device of claim 6, wherein the greatest cross-sectionalarea of the first bore is located in the femur metaphysis portion, and the greatest cross-sectional area of the second bore is located in the tibia metaphysis portion.

8. The orthopaedic training device of any preceding claim, wherein the facsimile of the distal portion of the femur includes a first securing means for releasably securing the femur metaphysis portion to the femur epiphysis portion.

9. The orthopaedic training device of claim 8, wherein the femur epiphysis portion and the femur metaphysis portion are configured to separate by the application of a force applied approximately parallel to the longitudinal length of the facsimile of the distal portion of the femur.

10. The orthopaedic training device of claim 8 or claim 9, wherein the first securing means comprises an interference fit or a snap fit between the femur metaphysis portion and the femur epiphysis portion.

11. The orthopaedic training device of any of claims 8 to 10, wherein the first securing means comprises a projection extending from one of the femur metaphysis portion andthe femur diaphysis portion, and a cavity located in the other of the femur epiphysis portion and the femur diaphysis portion, wherein, in use, the projection is arranged to be releasably receivable within the cavity.

12. The orthopaedic training device of any preceding claim, wherein the facsimile of the proximal portion of the tibia includes a second securing means for releasably securing the tibia metaphysis portion to the tibia epiphysis portion.

13. The orthopaedic training device of claim 12, wherein the tibia epiphysis portion and the tibia metaphysis portion are configured to separate by the application of a force applied approximately perpendicular to the longitudinal length of the facsimile of the proximal portion of the tibia.

14. The orthopaedic training device of claim 12 or claim 13, wherein the second securing means is arranged to enable the tibia metaphysis portion to be releasably slidably engageable with the tibia metaphysis portion.

15. The orthopaedic training device of claim 13 or claim 14, wherein a channel is provided within one of the tibia epiphysis portion and the tibia metaphysis portion, and a rail is provided extending from the other of the tibia epiphysis portion and the tibia metaphysis portion, wherein the rail is arranged to be slidably engageable within the channel.

16. The orthopaedic training device of any of claims 14 or claim 15, wherein the second securing means comprises an anti-sliding means for preventing the separation of the tibia epiphysis portion from the tibia metaphysis portion in a direction parallel to the sliding direction.

17. The orthopaedic training device of claim 16, wherein the anti-sliding means comprises a nub arranged on one of the tibia epiphysis portion and the tibia metaphysis portion, and a recess arranged in the other of the tibia epiphysis portion and the tibia metaphysis portion, wherein in use, the nub is arranged to be receivable within the recess to prevent sliding movement, and pullable from the recess in a direction perpendicular to the sliding direction to enable sliding movement.

18. The orthopaedic training device of any preceding claim, wherein one of the first tibia metaphysis portion and the tibia epiphysis portion comprises a stabilising means for preventing rotational movement of the tibia epiphysis portion relative to the tibia metaphysis portion, about at least one axis perpendicular to the longitudinal axis of the facsimile of the proximal portion of the tibia.

19. The orthopaedic training device of any of claims 13 to 17, further comprising an anti-lift means arranged to prevent the tibia epiphysis portion from moving away from the tibia metaphysis portion in a direction perpendicular to the sliding direction.

20. The orthopaedic training device of claim 19, when dependent on claim 15, wherein the anti-lift means comprises a socket located in the end of one of the channel and the rail, and a protrusion extending from the end of the other of the channel and the rail, wherein, in use, the protrusion is engageable within the socket.

21. The orthopaedic training device of any preceding claim, wherein the first material has a first density, the second material has a second density, and the third material has a third density, the first density being greater than the second and third densities.

22. The orthopaedic training device of any preceding claim, wherein the first material comprises a relatively rigid plastic, and the second material and third material both comprise open or closed cell foam.

23. The orthopaedic training device of claim 3, or any of claims 4 to 22 when dependent directly or indirectly on claim 2, wherein neither of the femur epiphysis portion and the tibia epiphysis portion include an attachment means for attaching the tensioning means.

24. An orthopaedic training system for use as a training aid for surgical orthopaedic techniques, the system comprising the orthopaedic training device of any preceding claim, and a support structure arranged to hold the facsimile of the distal portion of the femur adjacent to the facsimile of the proximal portion of the tibia, to thereby form a facsimile knee joint having the correct relative anatomical orientation.

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