Patent Description:
Some surgical procedures which involve the replacement of a part of the body with a prosthetic component may use trial components during a trialling stage of the surgical procedure. Trial components may be used to help determine the actual prosthetic components to use and/or the positioning and/or orientation of the actual prosthetic components so as to try and attain some intended surgical outcome. Trial components are generally used to help the surgeon understand the selection of the final implant before committing to the final prosthetic implant. The use of trial components can also help avoid any damage or fouling of the actual prosthetic components that might otherwise occur if one or more prosthetic components were used instead for trialling.

A range of trial components of different shapes and/or sizes and/or geometries may be used so that the surgeon can try and determine which prosthetic component to use. However, it can be difficult for the surgeon to understand the effects on the surgical outcome that a particular trial component may have compared to one or more other trial components. While a trial component may improve one aspect of the surgical outcome, it may have a negative impact on another aspect of the surgical outcome Sometimes, multiple trial components may be combined into a trial construct which can exacerbate this.

Furthermore, when a trial or trail construct is in place in the patient's body, it can be hard to visually inspect the trial or trial construct to understand exactly which trial or trial construct is currently being used and how that may impact on the surgical outcome. This is particularly the case for minimally invasive surgical procedures for which visual access to the surgical site may be very limited.

Therefore trial components, kits of trial components and/or methods of trialling which make it easier for the surgeon to understand that likely impact of a particular trial or trials on the outcome of a surgical procedure would be beneficial.

<CIT> provides a neck trial with grooves for mounting a plane guide, and forming the preamble of claim <NUM>. <CIT> provides a femoral stem with grooves for mounting a calcar collar. <CIT> provides a trial femoral head with indicator(s) representative of acetabular cup inclination and/or angle between the femoral neck and the transverse plane and/or acetabular cup anteversion and/or femoral neck version.

A first aspect of the invention provides a neck trial according to claim <NUM>.

The number of first lines may be in the range from <NUM> to <NUM>, and preferably may be in the range from <NUM> to <NUM>.

The number of second lines may be in the range from <NUM> to <NUM>, and preferably may be in the range from <NUM> to <NUM>.

The number of first lines may be greater than one and/or the number of second lines may be greater than one.

Each line may be a structural formation. The or each structural formation may be a male formation, for example a rib or ridge, or a female formation, such as a groove or trough.

All of the first lines and the second lines may be adjacent and/or may be positioned on the same part of the external surface.

All of the first lines and second lines may be on an anterior facing surface and/or a posterior facing surface of the neck trial in use.

The or each first line may be separate to the or each second line. There may be a gap or discontinuity between the or each first line and the or each second line.

The or each first line may be connected to the or each second line.

The or each first line may be positioned medially to the or each second line. The or each first line may be connected to a medial end of the or each second line.

The or each first line may be positioned laterally to the or each second line. The or each first line may be connected to a lateral end of the or each second line.

The or each second line may be positioned superiorly to the or each first line. The or each second line may be connected to a superior end of the or each first line.

The or each second line may be positioned inferiorly to the or each first line. The or each second line may be connected to an inferior end of the or each first line.

A second aspect of the invention provides a kit of parts comprising a plurality of neck trials according to the first aspect of the invention, wherein each neck trial has a different number of first lines and/or a different number of second lines.

A second aspect of the invention also provides a kit of parts comprising: a plurality of neck trials according to the first aspect, wherein each neck trial has a different position of the first line or lines relative to the second line or lines and/or a different position of the second line or lines relative to the first line or lines.

The kit of parts may further include a head trial which is releasably attachable to each of the neck trials and having a head line extending in a plane perpendicular to the neck axis when releasably attached to a one of the neck trials.

The kit of parts may further include a plurality of head trials, each being releasably attachable to each of the neck trials and each having a different number of head lines extending in a respective plane perpendicular to the neck axis when releasably attached to a one of the neck trials, and wherein each head trial is releasably attachable to the one of the neck trials at a different position along the neck axis.

The number of head lines on each head trial may be indicative of the distance along the neck axis of the trial head from the neck trial when the head trial is releasably attached to the neck trial in use.

The kit of parts may further include a liner trial, wherein the liner trial has a rim defining a mouth of the liner trial for accepting the head trial in use, and wherein at least one liner line extends in a plane parallel to the mouth and wherein the number of liner lines indicates the distance by which the trial liner moves the head trial along the neck axis.

The liner line may be on an exterior surface of the liner trial adjacent the mouth.

The kit of parts may further comprise a plurality of liner trials, each liner trial having a different number of liner lines, each liner line extending in a respective plane parallel to a respective mouth.

The kit of parts may further include an augmented liner trial, wherein the augmented liner trial has a portion of a rim defining a mouth of the augmented liner trial for accepting the head trial in use, and wherein a liner line extends in a plane parallel to the mouth.

The or each liner trial and the or each head trial may have the same colour.

The or each liner trial may have an inner diameter and the or each head trial may have an outer diameter and wherein the inner diameter and the outer diameter match such that the head trial can articulate within the liner trial.

The kit of parts may include two different neck trials, or five different neck trials of seven different neck trials.

The kit of parts may include two different liner trials or three different liner trials.

The kit of parts may include six different head trials.

A third aspect of the invention provides a trial assembly, comprising: a neck trial according to the first aspect; and a head trail, wherein the head trial which is releasably attached to the neck trial and has at least one head line, the or each head line extending in a respective plane perpendicular to the neck axis, and wherein the number of head lines is indicative of the length of the trial assembly along the neck axis.

The trial assembly may further comprise: a liner trial, wherein the liner trial has a rim defining a mouth of the liner trial, the head trial being accepted in the mouth, and wherein a liner line extends in a plane parallel to the mouth.

A fourth aspect provides background information as context to the invention and provides a method of trialling a joint of a patient, comprising: assembling a trial joint assembly, the trial joint assembly including a neck trial and a head trial, the trial neck bearing a plurality of lines arranged to indicate an amount of offset in a medial-lateral direction of the patient and an amount of leg-length in an inferior-superior direction of the patient arising from the neck trial; reducing a trial joint of the patient including the trial joint assembly; assessing the behaviour of the trial joint; and inspecting the plurality of lines to determine any changes to prosthetic components to be implanted in the patient to reconstruct the joint of the patient.

Any one or more of the trial joint components of the first aspect or kits of parts of the second aspect or trial assembles of the third aspect may be used in the method. These may give rise to corresponding counterpart method features.

The head trial may include at least one head line, the or each head line extending in a respective plane perpendicular to a neck axis of the neck trial, and the method may further comprise also inspecting the number of head lines to determine any changes to prosthetic components to be implanted in the patient to reconstruct the joint of the patient.

The trial joint may further include a liner trial, wherein the liner trial has a rim defining a mouth of the liner trial in which the head trial is accepted, and wherein the liner trial includes at least one liner line, the or each liner line extending in a respective plane parallel to the mouth, and the method may further comprise: also inspecting the number of liner lines to determine any changes to prosthetic components to be implanted in the patient to reconstruct the joint of the patient.

Assessing the behaviour of the trial joint may include assessing a resulting off-set in the medial-lateral direction.

Assessing the behaviour of the trial joint may include assessing a resulting leg length in the inferior-superior direction.

Assessing the behaviour of the trial joint may include assessing a resulting soft tissue tension of the trial joint.

The method may further comprise any one or more of: separating the trial joint; selecting a different neck trial and/or head trial and/or liner trial, based on the lines on each of them; reducing a further trial joint using the selected trial component or components in place of the corresponding previous trial component or components; assessing the behaviour of the further trial joint; and inspecting the plurality of lines on the components of the further trial joint to determine any changes to prosthetic components to be implanted in the patient to reconstruct the joint of the patient.

Assessing the behaviour of the trial joint or further trial joint may include assessing the range of motion of the trial joint or further trial joint.

Further aspects provide background information as context to the invention are provided by each of the liner trial, head trial and neck trial components individually.

Further aspects provide background information as context to the invention are provided by any combination of the liner trial, head trial and neck trial components and also in kit form or assembled form.

Further aspects provide background information as context to the invention are provided by methods of use of each of the liner trial, head trial and neck trial components individually or in any combinations thereof.

Embodiments of the invention will now be described in detail, and by way of example only, and with reference to the accompanying drawings, in which:.

Similar items in the different Figures share common reference signs unless indicated otherwise.

Embodiments of the invention will be described within the context of orthopaedics and in particular in relation to a hip joint. However, it will be appreciated that the invention is not necessarily limited in application to hip joints and may also be used in other ball and socket type joints.

As explained in greater detail below, one or more vertical lines (i.e. parallel to the inferior-superior axis of the patient's body in use) may be used to represent an amount of tension introduced into the joint owing to movement of the patient's limb along the medial-lateral axis, and which may be referred to as limb offset. Movement of the limb relative to the body in the medial direction will generally decrease tension and movement of the limb relative to the body in the lateral direction will generally increase tension. One or more horizontal lines (i.e. parallel to the medial-lateral axis of the patient's body in use) are used to represent an amount of tension introduced into the joint owing to movement of the patient's limb along the inferior-superior axis, and which may be referred to as limb length. Movement of the limb relative to the body in the superior direction will generally decrease tension and movement of the limb relative to the body in the inferior direction will generally increase tension. One or more diagonal lines (which may be generally perpendicular to the neck axis in use) may be used to represent an amount of tension introduced into the joint owing to movement of the patient's limb (arm or leg) along both the medial-lateral axis and the inferior-superior axis.

In the following, the "line" or "lines" will generally be used to indicate any linear indicium or linear indicia which can be discerned by a user. The line may have various forms, e.g. solid, broken, chain, etc. and may be embodied in various ways, e.g. by printing or marking or similar, and/or by various physical features, e.g. ridges, ribs, groove or channels or similar. Hence, although line will be used below for the sake of clarity, it will be appreciated that any linear indicium or indicia may be used in practice.

With reference to <FIG>, there is shown a kit of parts <NUM> according to an embodiment of the invention. The kit of parts <NUM> comprises a plurality of different types of trial component which can be used during a trialling stage of a surgical procedure, such as a hip replacement procedure. The kit of parts <NUM> can be provided as a trialling kit within a tray which can be provided to the operating theatre staff for use during the surgical procedure. The kit of parts <NUM> illustrated in <FIG> is for a particular head size or diameter. A similar kit of parts can be provided for other different head diameters. Also, the kit of parts <NUM> is for a particular implant system having a particular set of necks and neck geometries. A similar kit of parts can be provided for other different implant systems having a different neck or set of necks.

As illustrated in <FIG>, the trialling kit <NUM> may include one or a plurality of liner trials <NUM>. Three different liner trials <NUM>, <NUM> and <NUM> are provided. Each liner trial includes one or more lines as described in greater detail below. A first liner trial <NUM> has a body with a rim <NUM> defining a generally hemispherical cavity in which a head trial can be received in use. The circular rim <NUM> extends around and defines a mouth of the liner trial. A line, in the form of a solid line <NUM>, is provided on an outer surface of the liner trial and extends around the periphery of the mouth, adjacent and parallel to the plane of the rim <NUM>. The first liner trial <NUM> has a minimal or smallest thickness of the liner trials <NUM> provided in the kit. The thickness of the first liner trial <NUM> may corresponds to an increase in overall neck length of approximately <NUM>.

The second liner trial <NUM> is generally similar to the first liner trial <NUM>. However, the second liner trial <NUM> is an augmented liner trial which has a further segment <NUM> extending away from the rim <NUM> so as to define a slightly greater than hemispherical cavity within the liner trial <NUM>. This augmented liner trial <NUM> may be used in circumstances in which the trial cup has been placed with a relatively vertical orientation i.e. without much inclination relative to the patient's pelvis. Hence, the segment <NUM> helps to avoid dislocation of the head. The second liner trial <NUM> also includes a single line <NUM> on an outer surface and extending around the mouth of the liner trial and adjacent and generally parallel to the plane of the rim <NUM>. The second liner trial <NUM> has generally the same thickness as the first liner trial <NUM>. Hence, the thickness of the second liner trial <NUM> may correspond to an increase in overall neck length of approximately <NUM>.

The third liner trial <NUM> is generally similar to the first liner trial <NUM> and also includes a rim <NUM> extending around a mouth of hemispherical cavity defined by the body of the liner trial <NUM>. However, liner trial <NUM> includes a first line <NUM> and a second line <NUM>, each in the form of a solid line. Liner trial <NUM> has a greater thickness than the first <NUM> and second <NUM> liner trials. Hence, when inserted in a trial cup, the third liner trial <NUM> modifies the position of the centre of rotation of the joint in a direction away from the pelvis in both the lateral and inferior directions, and generally along the neck axis compared to the first or second liner trials.

In other embodiments, the liner trial <NUM> may be adapted otherwise to modify the position of the centre of rotation along the neck axis. For example, rather than having a different thickness, other features of the liner trial may be modified in order to change the position of the centre of rotation of a head trial in use. For example, third liner trial <NUM> may move the centre of rotation approximately <NUM> further along a cup axis (defined by a line passing through the centre of the mouth of the cup and liner and perpendicular to the plane of the mouth of the liner and cup), compared to the first and second liner trials. Hence, the thickness of the third liner trial <NUM> may corresponds to an increase in overall neck length of approximately <NUM>.

Hence, each liner trial includes at least one line and the number of lines on any liner trial is proportional to, or otherwise corresponds to, an amount of distance introduced into the trial joint assembly, and corresponding tension in the trial joint assembly, by use of that liner trial in the trial joint assembly.

Each of trial liners <NUM>, <NUM>, <NUM> defines a generally hemispherical cavity having an inner diameter of approximately <NUM>, for example. The trialling kit <NUM> also includes a plurality of head trials <NUM> as illustrated in <FIG>. In the illustrated embodiment, six head trials <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are provided. Each head trial has a generally truncated spherical form and has the same outer diameter of approximately <NUM>. Hence, each of head trials <NUM> to <NUM> can be received in any respective one of the liner trials <NUM>, <NUM>, <NUM> of the kit.

The liner trials and head trials of <FIG>, therefore correspond to a first size. A plurality of sets of liner trials and head trails can be provided, with each set corresponding to a different size. For example, liner trial inner diameters and head trial outer diameters of approximately <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be provided for corresponding sized prosthetic components. As will be appreciated from the following, the same neck trials can be used with liner trials and head trials of different sizes.

The body of each head trial defines a respective cavity therein for receiving a free end of a neck trial. Each cavity extends generally along a head axis, e.g. <NUM>, which passes through the centre of the head trial, and generally perpendicularly to a flat underside thereof and through a pole of the head trial.

Each of the head trials <NUM> to <NUM> is generally similar other than the position along the head axis <NUM> of the respective cavities is different for each of the head trials so that the centre of rotation of each head trial can adopt a different position along the neck axis when assembled on a neck trial in use. Also, each head trial includes a different number of lines and the number of lines is proportional to, or otherwise corresponds to, the resulting position along the neck axis arising from the position of the cavity within the head trial. Hence, each head trial includes at least one line and the number of lines indicates the amount by which the trial joint assembly will change along the neck axis, and with a corresponding change in soft tissue tension, owing to use of that head trial in the trial joint assembly.

For example, the first head trial <NUM> has a single line <NUM> generally in the form of a solid line extending at least partially around the head axis <NUM> and in a plane generally perpendicular to the head axis <NUM>. This first head trial <NUM> corresponds to a smallest neck length which may be less than a normal or default neck length and hence can be used to reduce an overall neck length in use.

A second head trial <NUM> includes first and second lines <NUM>, <NUM> and has a cavity arranged to position the centre of rotation of head trial <NUM> further away from the neck trial along the neck axis when assembled thereon in use compared to the first head trial <NUM>. For example, the difference in position along the neck axis between the first head trial <NUM> and second head trial <NUM> may be approximately <NUM>. Similarly, each of the third, fourth, fifth and sixth head trials have an incremental number of lines and each have respective cavities configured to position the centre of rotation of the head trial further along the neck axis and away from the neck trial. For example, the sixth head trial <NUM> has six lines <NUM> and corresponds to the greatest neck length which may be approximately <NUM> longer than a corresponding neck length arising from use of a first head trial <NUM> on the same neck trial.

It will be appreciated that each line does not need to correspond to the same change in neck length. For example, each additional line may not correspond to a same <NUM> change in neck length. Rather, the amount of the change in neck length may vary for addition or omission of a line. It is simply that the number of lines indicates or corresponds to the change in the neck length resulting from use of that particular trial head. The greater the number of lines, the greater the neck length and the fewer the number of lines, the less the neck length.

As noted above, each head trial has the same outer diameter and the outer diameter of each head trial matches the inner diameter of each of the liner trials so that any one of head trials <NUM> to <NUM> can be used with any one of liner trials <NUM> to <NUM>. This compatibility between the head trials and liner trials can be indicated by making the colour of the head trials and the colour of the liner trials the same. For example, <NUM> diameter liner trials and head trials may all be tan coloured, <NUM> diameter liner trials and head trials may all be green coloured, <NUM> diameter liner trials and head trials may all be blue coloured, <NUM> diameter liner trials and head trials may all be orange coloured and <NUM> diameter liner trails and head trials may all be pink coloured.

Hence, for a particular size of head, the compatibility between the head trials and liner trials may be indicated by the head trials and liner trials all having the same matching colour.

In some embodiments, the head trials and the liner trials may be made from suitable plastics and polymers such as Polyphenylsulfone (PPSU) or Polyoxymethylene (POM) or similar.

A trialling kit for a different sized head may include similar components but having different inner and outer diameters and each of the head trials and liners trials for the second trialling kit may have a matching colour different to the matching colour of the first trialling kit. It will be appreciated that typically a reasonable number of different sized heads may be provided by an orthopaedics manufacturer (for example approximately five different sized femoral heads of approximately <NUM>, <NUM>, <NUM>, <NUM> and <NUM>) and each trialling kit for each head size may have its own colour which matches within the kit but differs between kits, as described above.

The trialling kit <NUM> also includes a plurality of neck trials <NUM> as illustrated in <FIG>. In the embodiment illustrated in <FIG>, the trialling kit <NUM> includes five neck trials <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. Each neck trial has a generally similar overall construction but a different geometry.

For example, with reference to the first neck trial <NUM>, each neck trial has a body <NUM> with a male formation <NUM> extending from an underside thereof. A neck portion <NUM> extends away from the body <NUM> and along a neck axis <NUM>. A taper <NUM> is provided at a free end of the neck <NUM> for releasably attaching a head trial thereto in use. The first neck trial has a neck-stem angle of approximately <NUM>°.

First neck trial <NUM> is illustrated in <FIG> so as to form a part of a right hand hip joint in use. Hence, surface <NUM> is a generally anterior facing surface of the neck trial <NUM>. Anteriorly facing surface <NUM> bears a first line <NUM> and a second line <NUM>, each of which is in the form of a solid line.

The first line <NUM> is arranged to extend in a first direction generally parallel to the inferior-superior axis of a patient's body in use. The second line <NUM> is arranged to extend generally parallel to the medial-lateral axis of a patient's body in use.

The first line <NUM> indicates the extent to which the neck trial <NUM> will change the medial-lateral offset of the patient's leg. The second line <NUM> indicates the extent to which the neck trial <NUM> will change the leg length of the patient in use. As illustrated in <FIG>, the first neck trial <NUM> has only a single first line <NUM> and a single second line <NUM>. The single second line <NUM> indicates that this trail neck <NUM> provides the minimal amount of change in the leg length of the patient in use.

As also illustrated in <FIG>, there is a gap <NUM> between a superior the end of the first line <NUM> and a medial end of the second line <NUM>. The gap <NUM> signifies the position of the first line <NUM> relative to the second line <NUM> and in particular that the first line <NUM> is positioned more medially than the medial end of the second line <NUM>. This arrangement of the first line <NUM> relative to the second line <NUM> signifies or indicates that the first neck trial <NUM> will result in the minimal medial-lateral distance. In particular, the gap <NUM> signifies that the first neck trial <NUM> will provide a smaller media-lateral offset than a second neck trial <NUM>. In particular, the first neck trial will move the limb approximately <NUM> in the medial direction along the medial-lateral axis relative to the pelvis.

Second neck trial <NUM> is generally similar to first neck trial <NUM> except that the position of its neck <NUM>' relative to its body <NUM>' is different such that the position of the taper <NUM>' will move the limb relative to the pelvis further in the lateral direction compared to the first neck trial <NUM>. The neck-stem angle for the second neck trial <NUM> is approximately <NUM>°. As can be seen in <FIG>, the superior end of the first line <NUM> is connected to the medial end of the second line <NUM> and the absence of the gap <NUM> compared to the first neck trial <NUM>, signifies that the second trial neck <NUM> will result in a greater offset in the lateral direction, approximately <NUM>, compared to the first trial neck <NUM>.

The second neck trial <NUM> can be considered a neutral neck trial. In that case, the first neck trial <NUM> can be considered a reduced off-set neck trial as the first neck trial <NUM> will move the femur medially, by approximately <NUM>, compared to the second neck trial <NUM>.

Further, the anterior facing surface of the second neck trial <NUM> includes one second line <NUM> parallel to the medial-lateral axis similarly to the first neck trial <NUM> and at the same position on the body <NUM>' of the second neck trial as the second line <NUM> on the body <NUM> of the first neck trial <NUM>. This combination and configuration of lines indicates that the second neck trial <NUM> provides the same leg length position as the first neck trial <NUM>, but increases the medial-lateral offset of the leg (in the lateral direction) compared to the first neck trial <NUM>.

The connected single first line <NUM> and single second line <NUM> may be used to indicate that the second neck trial is a neutral neck and hence positions the femur at a neutral leg-length and a neutral medial-lateral position. This may correspond to a standard or default neutral leg position for a surgical procedure.

For example, the second neck trial <NUM> may increase the medial-lateral offset, in the lateral direction by approximately <NUM>, compared to the first neck trial <NUM>. Further, the second neck trial <NUM> has a slightly reduced neck-stem angle, compared to the first neck trial <NUM>. The first neck trial <NUM> may have a neck stem angle of approximately <NUM>° whereas the second neck trial <NUM> has a smaller neck-stem angle of approximately <NUM>°.

The third neck trial <NUM> is generally similar to the first and second neck trials other than the neck is arranged relative to its body to position the leg relative to the pelvis further laterally along the medial-lateral axis of a patient in use, compared to the first and second neck trials. The third neck trial <NUM> may have a stem-neck angle of approximately <NUM>°, similarly to the second neck trial, but be a high-offset neck trial. The third trial neck results in a femur positioned approximately <NUM> more laterally in the medial-lateral direction than the second trail neck <NUM>. This further increase of the resulting medial-lateral offset of the patient's femur arising from the third neck trial <NUM> is represented by the presence of two first lines <NUM>, <NUM> generally parallel to the superior-inferior axis on the anteriorly facing surface. Again, there is only a single second line <NUM> indicating that the third neck trial neck does not result in a chance of the leg-length compared to the first neck trial <NUM> or the second neck trial <NUM>. The first first line <NUM> has the same position on the anterior surface as the first line <NUM> of the second neck trial, whereas the second first line <NUM> is more laterally positioned on the anterior surface of the third neck trial compared to the first line <NUM>.

Fourth neck trial <NUM> is generally similar to second neck trial <NUM> except that the neck portion is arranged relative to the body portion to move the leg more inferiorly relative to the pelvis along the inferior-superior axis than the first, second or third neck trials. The fourth neck trial may have a stem-neck angle of approximately <NUM>° and may move the leg approximately <NUM> inferiorly compared to the first to third neck trials. This is indicated by the presence of a single first line <NUM> and a first <NUM> and a second <NUM> second line on the anteriorly facing surface. The first second line <NUM> has the same position on the anterior face of the fourth neck trial as the first second line <NUM> on the third neck trial, whereas the second second line <NUM> is positioned more inferiorly on the fourth neck trial compared to the first second line <NUM> on the third neck trial. The fourth neck trial will result in the same medial-lateral position of the leg as the second neck trial <NUM> as indicated by the single first line <NUM>.

The fifth neck trial <NUM> is generally similar to the fourth neck trial <NUM> other than the neck being arranged relative to the body so as to increase the medial-lateral offset of the femur in the lateral direction compared to the second and fourth neck trials. The fifth neck trial may have a stem-neck angle of approximately <NUM>°. The resulting leg position in the inferior-superior direction is the same as for the fourth neck trial, i.e. approximately <NUM> more inferior, as indicated by the first <NUM> and second <NUM> second lines, and which have the same position on the anterior face of the fifth neck trial as lines <NUM> and <NUM> on the fourth neck trial. The amount of lateral offset in the medial-lateral direction is indicated by the presence of first <NUM> and second <NUM> first lines generally parallel to the superior-inferior axis and similarly to the third neck trial <NUM>. Hence, the fifth neck trail may move the femur approximately <NUM> laterally and <NUM> inferiorly compared to the second neck trial <NUM>.

The second neck trial <NUM> (having a stem-neck angle of approximately <NUM>°) may be taken as a reference or neutral which provides a neutral or first amount of off set and a neutral or first amount of leg length. Compared to the second neck trial, the fist neck trial <NUM> (having a stem-neck angle of approximately <NUM>°) may move the leg approximately <NUM> medially, as reflected by the gap between, and relative position of, the vertical line <NUM> and the horizontal line <NUM> compared to the connected vertical line <NUM> and horizontal line <NUM> on the second neck trial, and does not change the leg length as reflected by the single horizontal line <NUM>, <NUM> on each of them and at the same position on the anterior faces.

Compared to the second neck trial <NUM>, the third neck trial <NUM> (having a stem-neck angle of approximately <NUM>°) may move the leg approximately <NUM> laterally, as reflected by the two vertical lines <NUM>, <NUM> compared to the one vertical line <NUM> on the second neck trial <NUM>, and does not change the leg length as reflected by the single horizontal line on each of them. Hence, in this example, the second vertical line <NUM> on the third trial <NUM> indicates a change of <NUM> laterally compared to the second neck trial <NUM>, whereas the gap and relative positions of the vertical line <NUM> and horizontal line <NUM> on the first neck trial <NUM> corresponds to a change of <NUM> medially compared to the second neck trial.

Compared to the second neck trial <NUM>, the fourth neck trial <NUM> (having a stem-neck angle of approximately <NUM>°) may move the leg approximately <NUM> inferiorly along the inferior-superior axis, as reflected by the two horizontal lines <NUM>, <NUM> compared to the one horizontal line <NUM> on the second neck trial <NUM>, and does not change the leg length as reflected by the single vertical line on each of them.

Compared to the second neck trial <NUM>, the fifth neck trial <NUM> (having a stem-neck angle of approximately <NUM>°) may move the leg approximately <NUM> inferiorly along the inferior-superior axis, as reflected by the two horizontal lines <NUM>, <NUM> compared to the one horizontal line <NUM> on the second neck trial, and also moves the leg approximately <NUM> laterally as reflected by the two vertical lines <NUM>, <NUM> on the fifth neck trial compared to the one vertical line <NUM> on the second neck trial <NUM>.

Hence, the number of lines and/or relative position of the lines, is generally proportional to or corresponds to the change in the position of the leg (the more lines, the greater the change, the fewer lines the less the change). Each line, or relative position, may not corresponds to the same amount of change. For example the second vertical line <NUM> on the third neck trail corresponds to a change of <NUM>, compared to the second neck trial, whereas the gap <NUM> on the first neck trial <NUM> corresponds to a change of <NUM> compared to the second neck trial <NUM>.

The same arrangements of linear indicia may be provided on the posteriorly facing surface of the neck trials as illustrated in <FIG>. Hence, those markings may be used when the neck trials are used for a left hand hip joint.

<FIG> shows a further set of neck trials <NUM> which may be provided additionally or alternatively to the neck trials <NUM> illustrated in <FIG>. For example, neck trials <NUM> may correspond to a different implant system to that of neck trials <NUM> and hence may be used instead of neck trials <NUM> with the liner trials <NUM> and head trials <NUM> shown in <FIG>.

The further neck trials <NUM> comprise a first neck trial <NUM> and a second neck trial <NUM> which are generally similar to those shown in <FIG>. First neck trail <NUM> and second neck trail <NUM> each have the same stem-neck angle of approximately <NUM>°. First neck trial <NUM> includes a single vertical line <NUM> and a single horizontal line <NUM> and second neck trial <NUM> has a two vertical lines <NUM>, <NUM> and a single horizontal line <NUM>. Similarly to above, the single horizontal line on each neck trial indicates that each neck trial results in the same leg position along the inferior-superior axis, whereas the two vertical lines <NUM>, <NUM> compared to the single vertical line <NUM> indicates that the second neck trial <NUM> results in a greater offset of the leg laterally compared to the first neck trial <NUM>.

For example, the first neck trial <NUM> can be considered a neutral neck trial which has a standard off set positon of the leg as reflected by the single vertical line, whereas the second neck trial <NUM> can result in a high offset position as it moves the leg laterally, e.g. by approximately <NUM> to <NUM>, compared to the first trial neck <NUM>.

An implant system may provide a different sizes of prosthesis and a pair of neck trials <NUM>, <NUM> may be provided corresponding to the smaller sized prostheses and the larger sized prostheses. For example, for a first implant system, the second neck trial <NUM> for the smaller sized prostheses may move the leg <NUM> laterally whereas the second neck trial <NUM> for the larger sized prostheses may move the leg <NUM> laterally. For example, for a second implant system, a pair of neck trails <NUM>, <NUM> may be provided for each of five different sizes of prostheses, and the lateral movement provided by the second neck trial <NUM> may be <NUM>, <NUM>, <NUM>, <NUM> and <NUM> for the smallest to the largest of the five sizes of prostheses.

The neck trials may be made from any suitable material, such as surgical grade stainless steel or various suitable polymers such as Polyetheretherketone (PEEK), or Polyarylketherketone (PAEK) or similar. The linear indicia may be provided on the anterior and/or anterior facing surfaces of the neck trials using laser marking.

The lines or linear indicia can be provided on the various trials as simple and high contrast markings which are easy to visualise by a user in order to understand the effect of the trial components on the trial joint assembly. The colour of the liners and/or heads can also be used to encode and communicate size information to the user.

<FIG> shows a perspective view of an example trial hip joint <NUM> that may be constructed using a selection of the trial components illustrated in <FIG>. The trial hip joint <NUM> includes a final broach <NUM> which has been used to prepare a femoral cavity within the femur of the patient. It will be appreciated that in other embodiments, other femoral parts may be used instead of a femoral broach. For example, a trial femoral stem may be used. In other embodiments, a prosthetic femoral stem may be used. Also, other instruments and/or tools used during preparation of the femur may be used instead.

The third neck trial <NUM> is releasably mounted on a proximal surface <NUM> of femoral broach <NUM>. The proximal surface <NUM> has an aperture for receiving the male member <NUM> extending from the distal surface of the neck trial <NUM>. In other embodiments, a male member may be provided on the proximal surface <NUM> to be received within a corresponding female formation within the body of the neck trial <NUM>. The third head trial <NUM> is releasably attached to the taper of the neck trial <NUM>. The head trial <NUM> is received within the cavity defined by the body of the augmented liner trial <NUM>. The augmented liner trial <NUM> is received within a trial acetabular cup <NUM> which may be provided in the form of a shell as illustrated in <FIG>. In other embodiments, the liner trial <NUM> may be received in the prosthetic shell or cup.

As discussed above, each of the trial components of the trialling kit <NUM> includes a number of lines or linear indicia and the number of lines or linear indicia, and/or the relative position of the horizontal and vertical lines, visually indicates the effect of each trial component on a particular property of the resulting joint. The linear indicia are a visual representation or indication of both the amount and direction of tension which is being applied to the resulting joint by each of the trail components in the trial joint assembly.

As illustrated in <FIG>, the line <NUM> on augmented trial liner <NUM> is visible as are the three lines <NUM> on the head trial <NUM>. Each of these are generally perpendicular to the neck axis <NUM> and indicate the amount by which the neck length is affected by each of these trial components. The linear indicia on the neck trial <NUM> indicate that the neck trial <NUM> has a minimal effect on the leg length, but have an increased effect on the medial-lateral offset of the resulting joint.

This is further illustrated in <FIG> which shows a graphical representation <NUM> of the relationship between the linear indicia on the trial components and the changes to the resulting joint.

The number of linear indicia extending in the superior-inferior direction effects the medial-lateral offset of the leg of the patient as illustrated by line A in <FIG>. The greater the number of vertical lines on the neck trial, the greater the offset of the patient's leg laterally along the medial-lateral axis, as indicated by arrow <NUM>. Similarly, the greater the number of horizontal lines, parallel to the medial-lateral direction, the greater the effect of the neck trial on the leg length of the patient, as illustrated by line B in <FIG>. The greater the number of lines parallel to the medial-lateral axis, the greater the change in leg length in the inferior direction illustrated by line <NUM> in <FIG>.

Further, the number of linear indicia on the liner trial and/or neck trial of the j oint, the greater the change in neck length along line C of <FIG> extends generally in the direction of the neck axis <NUM> and can increase tension in the hip joint in the direction illustrated by line <NUM> in <FIG>. As will be appreciated from a comparison of <FIG> and <FIG>, the linear indicia on the head trial <NUM> and liner trial <NUM> are generally perpendicular to the direction of the neck axis <NUM>.

If the head trial and / or liner trial are changed to alter the neck length, C, then as illustrated in <FIG>, this can also have an effect on the leg length, B, and offset, A. For example, reducing the overall neck length has the effect of reducing the offset A and the leg length B. Similarly, increasing the overall neck length has the effect of increasing the offset A and leg length B.

Similarly, increasing the offset A will increase the neck length C slightly, but not necessarily also the leg length B. Similarly, increasing the leg length B will increase the neck length C slightly but may not change the offset A in the medial-lateral direction.

The visual indicia included on the trialling components therefore provides an easily understandable system for allowing the surgeon to immediately understand the contribution which each of the trial components provides to the trial joint in terms of offset and/or leg length and/or neck length. A surgeon can therefore easily determine which one or more of the trial components to change in order to improve the likely outcome of the procedure by visually inspecting the trial components used in the trial joint.

Further, the surgeon can easily determine which of the trial components in the kit to use for a further trial assembly, in order to re-trial the joint with a modified trial joint, using other trialling components from the kit.

For example, <FIG> shows a view in the generally anterior-posterior direction of a right hand hip trial joint <NUM>, similar to that shown in <FIG>. The trial joint <NUM> includes trial shell <NUM>, first trial liner <NUM>, fifth trial head <NUM> and second trial neck <NUM>.

As indicated by the visual indicia <NUM>, <NUM> on the trial neck <NUM>, the current trial neck <NUM> has a neutral impact on the leg length and the offset. The single linear indicia on the liner trial <NUM> shows that the liner trial is providing a minimal contribution to the overall neck length whereas the five linear indicia on the head trial <NUM> shows that the head trial is contributing significantly to the overall neck length. Hence, if the surgeon wishes to reduce the overall neck length, for example because of significant tension in the soft tissues of the reduced trial joint, then the surgeon may quickly understand, by inspection of the trial joint <NUM> that the trial head <NUM> is contributing significantly to the tissue tension.

Hence, the surgeon may replace the trial head <NUM> with the third trial head <NUM> so as to reduce the overall neck length and resulting in the trial joint <NUM> illustrated in <FIG>.

However, by reducing the overall neck length, along direction C in <FIG>, the surgeon has now also reduced the offset by moving the leg medially along the medial-lateral axis A. Therefore, the medial-lateral offset of the patient's leg has now been reduced by the trail joint assembly <NUM> compared to the situation for the trial joint assembly <NUM> of <FIG>. The surgeon may determine that it is desirable to increase the medial-lateral offset laterally. By inspecting the trialling kit <NUM>, the surgeon can immediately see that the third neck trial <NUM> increases the medial-lateral offset laterally by virtue of the two lines <NUM>, <NUM> parallel to the inferior-superior axis.

Hence, the surgeon may replace second trial neck <NUM> with third trial neck <NUM> so as to arrive at the trial joint <NUM> illustrated in <FIG>. Hence, in the third trial joint <NUM>, the overall neck length has been reduced compared to the first trial assembly <NUM> and the medial-lateral offset increased by the third neck trial <NUM> so as to better reproduce the intended medial-lateral offset and to compensate for the reduction in medial-lateral offset by the use of the third head trial <NUM> in the place of the fifth head trial <NUM> to reduce the overall neck length.

As can be seen in <FIG>, the number of linear indicia generally perpendicular to the neck axis (those on the liner trial and the head trial) are representative of the amount of tension in the trial joint. The number of linear indicia extending in the inferior-superior direction are generally indicative of the amount of offset of the trial joint. The number of linear indicia in the medial-lateral direction are indicative of the amount of leg length in the trial joint. Hence, the linear indicia provide an easy to see and simple to understand indication of the effect of each of the different trialling components on the likely surgical outcome for such a hip joint.

Furthermore, not only do the linear indicia allow the surgeon to understand which trialling components are contributing what effect to the hip joint, the surgeon can also use the visual indicia to easily and accurately determine which of the other trial components to select to use to retrial the joint in order to correct for any undesirable properties of the current trial, e.g. in terms of offset, leg length and / or tissue tension. This will be explained in greater detail with reference to <FIG>.

<FIG> illustrates a flow chart illustrating a method <NUM> of using the trialling kit <NUM> according to a further embodiment of the invention. A number of the steps of the surgical procedure for replacing a hip joint are generally known, and are not described in detail so as not to obscure the present invention. The present invention is particularly relevant to the trialling stage of a hip replacement surgical procedure.

The method <NUM> begins with preparation of the acetabulum at <NUM>. This may include removing the various soft tissue structures surrounding the acetabulum and using an acetabular grater and/or reamer in order to prepare a substantially hemispherical cavity within the acetabulum of the patient's pelvis.

At <NUM>, the femur of the patient is prepared. This can include resecting the femoral head and the proximal part of the femur. Various tools and instruments commonly known in the art may be used to initiate and prepare an intramedullary cavity extending generally along the proximal part of the femoral axis. At some stage in the preparation of the femur, a final size broach may be used <NUM> to finally prepare the femoral cavity. A handle may then be removed from the broach and the broach may be left within the femur. For example, broach <NUM> is shown in <FIG>.

At <NUM>, according to a planned surgical procedure, a cup trial, e.g. trial <NUM>, may be selected and inserted in the prepared acetabular cavity. At step <NUM>, a liner trial can be selected from the trialling kit which corresponds to the pre-planned cup and head size for the patient. If the cup trial has been inserted with a significant vertical orientation or there is a risk of the patient dislocating, then augmented liner <NUM> may be used. Otherwise, the surgeon may select a standard liner trial for insertion in the cup trial.

At <NUM>, a one of the neck trials <NUM> can be selected in accordance with the pre-planned surgical procedure and releasably attached to the broach <NUM> at step <NUM>.

At <NUM>, a selected one of the head trials <NUM> can be selected and attached to the taper of the neck trial at <NUM>. Then at <NUM> the trial joint can be reduced and has the general structure illustrated in <FIG> and <FIG>.

At <NUM>, the surgeon can assess the properties of the resulting trial joint. This can include assessing the tension in the soft tissues of the hip joint. This may also include assessing the resulting leg length of the patient, along the generally inferior-superior axis of the patient. This may also include assessing the offset of the patient's leg along the medial-lateral axis. Step <NUM> may also include carrying out a range of motion (ROM) assessment to determine any likely impact between the trial components and also to assess the tissue tension arising from the currently selected trial components. At step <NUM>, the surgeon may determine, based on experience or other factors, whether the hip joint arising from this selection of components is acceptable or not. If it is acceptable, then at <NUM>, the trial components can be removed. The trial components can then be replaced with prosthetic components having generally the same size, position and/or orientation as the trial components.

Alternatively, the surgeon may select prosthetic components having slightly different geometries to compensate for any properties of the hip joint determined during the assessment stage <NUM> instead of selecting prosthetic components identical to the trial components. For example, if the surgeon determines at <NUM> that the tissue tension is slightly too great, than at <NUM>, the surgeon may select to use a slightly shorter neck length for the femoral prosthesis in order to help reduce the tissue tension.

Returning to step <NUM>, if the surgeon determines that the joint is not acceptable in some way, then at <NUM>, the surgeon can inspect the trial joint in situ. For example, if at <NUM>, the surgeon assesses the joint and determines that the tissue tension is too loose and also the medial-lateral offset is too small for the current trial assembly then the surgeon can inspect the trial construct at <NUM> to determine how the trial construct might be modified. For example, <FIG> shows a view of a trial assembly <NUM> comprising the third head trial <NUM> mounted on the second neck trial <NUM> mounted on femoral broach <NUM>. As can be seen from the number of linear indicia on the head trial <NUM>, the head trial is contributing a moderate amount to the overall neck length and, from the linear indicia on the neck trail <NUM>, the neck trial <NUM> is contributing neutral amounts to the leg length and offset. Hence, the surgeon can easily understand how the current trial components are impacting on the trial joint performance.

Hence, at <NUM>, the surgeon can separate the trial joint and select one or more trial components from the trialling kit <NUM> in order to rectify the surgical outcome. For example, if the surgeon considers that the tissue tension is slightly too loose and the medial-lateral offset is too small, the surgeon can easily determine, from inspecting the trialling kit <NUM> which of the other neck trials can be used to increase the medial-lateral offset but without increasing the leg length. As noted above, increasing the medial-lateral offset will also increase the overall neck length slightly. Hence, at <NUM>, the surgeon may disassemble the initial trial assembly <NUM> and replace neck trial <NUM> with the third neck trial <NUM> to arrive at the trial assembly <NUM> illustrated in <FIG>.

Hence, process flow can return as illustrated by process flow line <NUM> to step <NUM> at which the surgeon can reduce the trial joint with the new trial assembly <NUM>. The effect of replacing neck trial <NUM> with neck trial <NUM> is illustrated in <FIG>. The previous position of the femoral broach <NUM> is indicated in shadow and the new position of femoral broach is indicated in darker form <NUM>'. Hence, the effect of replacing neck trial <NUM> with neck trial <NUM> is to move the patient's leg laterally along the medial-lateral axis by increasing the offset by about <NUM>, but while maintaining the leg length. In <FIG>, the linear indicia on the anteriorly facing surface of the neck trial <NUM> indicate that the neck trial has the effect of moving the patient's leg laterally relative to the centre of rotation of the hip joint.

Hence, the reduced replacement trial joint <NUM> can be assessed again at step <NUM> and the surgeon may determine that the second trial hip joint <NUM> is likely to lead to a satisfactory surgical outcome and therefore may be adopted for the final prosthetic implants.

As another example, returning to step <NUM>, if it were determined at <NUM> that the tissue tension were too great and the medial-lateral offset were too small at <NUM> for the initial trial assembly <NUM>, then at <NUM>, the surgeon can immediately understand from the linear indicia on the initial trial head <NUM> that the trial head is contributing significantly to the neck length and therefore to the tension. Hence, at <NUM>, the surgeon may easily determine that a trial head which reduces the tissue tension could be tried and can easily identify, e.g., the second trial head <NUM> owing to the reduced number of linear indicia thereon. The surgeon can also easily identify that trial neck <NUM> may be considered as that will increase the medial-lateral offset (two vertical lines <NUM>, <NUM>) without changing the leg length (one horizontal line <NUM>). Hence, the surgeon may select the second trial head <NUM> and the third trial neck <NUM> and assemble trial assembly <NUM> as illustrated in <FIG>.

Process flow returns as indicated by line <NUM> to <NUM> and the trial joint can be reduced again and further assessed at <NUM>. The surgeon may then determine that the tissue tension is now appropriate and also that the offset is appropriate at <NUM>. As illustrated in <FIG>, the second head trial <NUM> has the effect of reducing the overall neck length while the third neck trial <NUM> has the effect of increasing the offset laterally, without changing the leg length, and slightly contributing to the overall neck length.

Further, the angle between the linear indicia on the liner trial and the linear indicia of the head trail can be used to help assess whether an augmented liner trial might be used. For example, assuming a neutral liner trial is currently being used, then during the assessment at <NUM>, the surgeon may place the femur in the Ranawat sign position (generally the operated leg is placed in extension and internally rotated by <NUM>°). The surgeon may then assess whether the linear indicium on the liner trial are sufficiently parallel to the linear indicia on the head trial. If they are, for example because the acute angle subtended between them is less than a few degrees, for example less than about <NUM>°, then the surgeon may determine that the risk of dislocation is low and select to use a normal liner. Alternatively, if the acute angle subtended between them is greater than about <NUM>°, for example, then the surgeon may determine that the risk of dislocation is high and the surgeon may select to use an augmented liner instead. Hence, the linear indicia of tension in the joint can also be used to assess the risk of dislocation and hence whether to use an augmented liner or not.

Hence, the number of linear indicia in the first and second directions on the neck trial indicate the amount to which the neck trial contributes to the position of the patient's leg in the offset and leg length directions. The number of linear indicia on the head trial and / or liner trial are representative of the amount by which these components contribute to the neck length. Therefore, the surgeon can easily understand by visual inspection how each of the different trial components are contributing to the behaviour of the trial joint simply by inspecting them in situ.

Further, the linear indicia can easily be used to select a one or more replacement trial components in order to compensate for any potential deficiencies in a current trial joint and allow a further trial assembly to be assembled likely to reduce any deficiencies in the joint.

Further, as the liner trials and head trials of any particular head size are colour coded, a surgeon can easily ensure that the trial head size and trial liner size match for any trialling kit. Hence, if a trialling kit is provided with liner trials and head trials of different sizes, such that a surgeon decides to use a different sized liner trial, then the surgeon can easily determine which head trials match the different sized liner based on their matching colours.

In this specification, example embodiments have been presented in terms of a selected set of details. However, a person of ordinary skill in the art would understand that many other example embodiments may be practiced which include a different selected set of these details. It is intended that the following claims cover all possible example embodiments. Any instructions and/or flowchart steps can be executed in any order, unless a specific order is explicitly stated or implicitly required.

Claim 1:
A neck trial [<NUM>] comprising:
a body [<NUM>] having an exterior surface; and
a neck [<NUM>] extending away from the body [<NUM>] and along a neck axis [<NUM>], wherein at least one first line [<NUM>] is provided on the exterior surface and the or each first line [<NUM>] extends in a first direction parallel to an inferior-superior axis of a patient when in use and at least one second line [<NUM>] is provided on the exterior surface and the or each second line [<NUM>] extends in a second direction parallel to a medial-lateral axis of the patient in use, and characterised in that:
the number of first lines [<NUM>], or the position of the first line or lines [<NUM>] relative to the second line or lines [<NUM>], is indicative of an amount of offset of the patient's leg in the medial-lateral direction caused by the neck trial [<NUM>] in use; and
the number of second lines [<NUM>], or the position of the second line or lines [<NUM>] relative to the first line or lines [<NUM>], is indicative of an amount of leg-length of the patient's leg in the inferior-superior direction caused by the neck trial [<NUM>] in use.