Surgical instruments and methods

Abstract

The present invention provides a cement restrictor inserter instrument (130) comprising: an inserter (131) having a handle (132) at a proximal end, a cement restrictor attachment formation (137) at a distal end for releasably attaching a cement restrictor (150), a shaft (136) extending from the proximal end to the distal end, and a stop (138) located on the shaft between the proximal end and the distal end; and a body (140) having a shape corresponding to the shape of an orthopaedic prosthetic implant, a spacer (142), a visible depth guide feature (190) and a releasable attachment mechanism, the body being releasably attachable to the shaft by the releasable attachment mechanism, and wherein the spacer is configured to position the visible depth guide feature at a fixed position relative to the inserter when the spacer abuts the stop, the fixed position corresponding to a target cement restrictor position when the visible depth guide feature is aligned with a feature of the bone of a patient into which the cement restrictor is to be inserted.

Description

[0001] The present disclosure relates to surgical instruments and methods, and more particularly but not exclusively to surgical instruments and methods for placing a cement restrictor during orthopedic surgery.

[0002] Some orthopedic surgeries use cemented implants, where cement is used to help fix a prosthetic orthopedic implant in a patient's bone. Typically, as part of the surgical procedure, a cavity is formed in the bone to receive the prosthetic implant. The cement is then introduced into the cavity, and then the prosthetic implant is inserted.

[0003] In some cases, a cement restrictor can be inserted into the cavity before the cement is introduced. The cement restrictor can be used for various purposes. The cement restrictor can provide a solid platform upon which the cement can be pressurized to ensure that the cement is well introduced into the cavity. Additionally or alternatively, the cement restrictor can prevent or reduce the amount of cement that extends beyond the cement restrictor and further into the prepared cavity. Excessive cement in the cavity can pose difficulties if a revision surgery is later required, for example, the need to remove the excessive cement from the cavity during the revision surgery.

[0004] Regardless of the reason for using the cement restrictor, there is typically a preferred position or depth within the cavity where the cement restrictor should be placed. This preferred position or depth may be related to the position of the prosthetic implant in order to attempt to ensure that there is a preferred amount of cement between the cement restrictor and the prosthetic implant. Too much cement between the cement restrictor and the implant presents the same potential difficulties for the above-mentioned revision surgery, and too little cement may reduce the ability of the prosthetic implant to be properly seated after insertion and / or to properly fix the implant within the cavity.

[0005] Accordingly, it is generally desirable to correctly position the cement restrictor. However, the correct position of the cement restrictor may vary with the size and / or type of implant being used. Additionally, it is not easy for a surgeon to visualize the position of the cement restrictor during insertion because the cement restrictor will be obscured within a portion of the cavity.

[0006] Introducers for cement restrictors have various markings disposed thereon to provide some guidance to the surgeon regarding the depth to which the cement restrictor has been inserted. However, these markings may be difficult to see and / or read during the surgery. Additionally, the anatomical features to which these markings should be aligned may be difficult to visualize at the surgical site and / or may not be clear. Additionally, there may not be an obvious relationship between the various markings and the depth of insertion of the intended prosthetic implant that the surgeon is currently attempting to achieve. The surgeon may have difficulty reliably recalling which of the multiple markings they should be using currently. This problem is exacerbated for more complex implant systems, where the proper position of the cement restrictor varies in a more complex manner with the different sizes of the available implants.

[0007] Accordingly, an instrument and method that can facilitate the easy and / or reliable positioning of a cement restrictor would be beneficial.

[0008] According to a first aspect of the present disclosure, there is provided a cement restrictor inserter instrument comprising: an inserter having a handle at a proximal end, a cement restrictor attachment formation at a distal end for releasably attaching a cement restrictor, a shaft extending from the proximal end to the distal end, and a stop located on the shaft between the proximal end and the distal end; and a body having a shape corresponding to the shape of an orthopaedic prosthetic implant, a spacer, a visible depth guide feature, and a releasable attachment mechanism by which the body can be releasably attached to a rod, and wherein the spacer is configured to position the visible depth guide feature at a fixed position relative to the inserter when the spacer abuts the stop, the fixed position corresponding to a target cement restrictor position when the visible depth guide feature is aligned with a feature of the patient's bone into which the cement restrictor is to be inserted.

[0009] The releasable attachment mechanism may include a push-fit mechanism or a snap-fit mechanism.

[0010] The stop may include an attachment formation, and the releasable attachment mechanism may interact with the attachment formation.

[0011] The releasable attachment formation may include a C-clamp or a round clip and a groove arranged to receive the C-clamp or the round clip. The C-clamp or the round clip may be located within a portion of the stop and / or the releasable attachment mechanism of the body may include a groove.

[0012] The body may define an open channel or a closed channel, and the open channel or the closed channel is configured to receive the shaft. The channel may extend along the longitudinal axis of the body and / or along an axis parallel to the longitudinal axis of the shaft.

[0013] The releasable attachment mechanism can be a rotatable releasable attachment mechanism. The releasable attachment mechanism can permit rotation of the shaft relative to the body.

[0014] The cement restrictor attachment formation can include a press-fit formation.

[0015] The cement restrictor attachment formation can include a rotational attachment mechanism. The rotational attachment mechanism can be a thread.

[0016] The visible depth guide feature can include a surface or an edge of a portion of the body.

[0017] The visible depth guide feature can include markings on a surface of a portion of the body.

[0018] The visible depth guide feature can include a plurality of markings on the surface of the portion of the body. Each of the plurality of markings can correspond to a different insertion position or depth of the orthopaedic prosthetic implant relative to the patient's bone.

[0019] The orthopaedic prosthetic implant can be a humeral stem, a shoulder component, a femoral stem, a femoral component of a knee, or a tibial component.

[0020] The body can have dimensions corresponding to those of the orthopaedic prosthetic implant. The body can have dimensions with a size error corresponding to those of the orthopaedic prosthetic implant of less than 1 mm, 2 mm, 3 mm, 4 mm or 5 mm.

[0021] The body can be mounted on an inserter, wherein a spacer abuts or engages or mates with a stop.

[0022] Another aspect of the present disclosure provides a kit for a surgical instrument portion, the kit including: the cement restrictor inserter instrument of the first aspect; and an additional body having a shape corresponding to the shape of an orthopedic prosthesis implant, an additional spacer, an additional visible depth guide feature, and an additional releasable attachment mechanism, the additional body being releasably attachable to the shaft by the additional releasable attachment mechanism. The additional body may have a different size than the body. The additional body may have a different length and / or a different width. The additional body may be larger or smaller than the body. A plurality of additional bodies may be provided, and each body may have a different size and / or the same shape. The additional body may have a different size than the body and may correspond to the shape of orthopedic prosthesis implants of different sizes. The additional spacer may have a different size than the spacer and may be configured to position the additional visible depth guide feature at a different fixed position relative to the inserter when the additional spacer abuts a stop, the different fixed position corresponding to the target cement restrictor position when the additional visible depth guide feature is aligned with a feature of the patient's bone into which the cement restrictor is to be inserted.

[0023] Another aspect of the present disclosure provides a method of inserting a cement restrictor into a cavity in a patient's bone, the method including: selecting a body having a shape corresponding to the shape of an orthopedic prosthesis implant to be implanted in a cavity in the patient's bone, the body including a visible depth guide feature; releasably attaching the body to a shaft of a cement restrictor inserter at a predetermined position; attaching a cement restrictor to a distal end of the shaft of the cement restrictor inserter; inserting the cement restrictor inserter with the body mounted thereon into the cavity to a depth determined by aligning the visible depth guide feature with a feature of the patient's bone.

[0024] The method may further include rotating the shaft of the cement restrictor inserter relative to the body to disengage the cement restrictor from the distal end of the rod; and removing the cement restrictor inserter from the cavity.

[0025] Selecting the body may further include selecting a body having a size corresponding to the size of the orthopedic implant to be implanted in the cavity of the patient's bone.

[0026] The method may further include: prior to selecting the body, determining the size of the orthopedic implant to be implanted based on a final test component or a final drill or a final reamer or a final cutting instrument.

[0027] The method may further include, after attaching the body and before attaching the cement restrictor, attaching a cement restrictor test piece to the distal end of the shaft and inserting the cement restrictor inserter into the cavity to test the size of the cement restrictor.

[0028] The characteristic portion of the patient's bone can be an anatomical characteristic portion of the patient's bone.

[0029] The characteristic portion of the patient's bone can be the resected surface or edge or rim of the patient's bone.

[0030] The visual depth guide can be a surface or edge of the body.

[0031] The visual depth guide feature can be a mark on the surface of the body.

[0032] The visual depth guide feature can include a plurality of marks on the surface of the body. Each mark can correspond to a different position of the orthopaedic prosthesis implant relative to the patient's bone, such as the depth of insertion. The method can also include using the mark corresponding to the selected one of the different positions to determine the depth to which the cement restrictor inserter is inserted.

[0033] The prosthetic orthopaedic implant can be a femoral stem. The characteristic portion of the patient's bone can be the proximal resection of the femur or the neck resection of the femur.

[0034] The prosthetic orthopaedic implant can be a tibial component. The characteristic portion of the patient's bone can be the proximal resection of the tibia.

[0035] The prosthetic orthopaedic implant can be a humeral stem. The characteristic portion of the patient's bone can be the proximal resection of the humerus or the rim of the cavity reamed in the proximal humerus.

[0036] The embodiments will now be described in detail by way of example only and in conjunction with the accompanying drawings, in which:

[0037] Figure 1 A view of a prosthetic hip joint is shown, which shows the preferred relative positioning of the prosthetic stem implant and the cement restrictor within the patient's femur;

[0038] Figure 2 A 3D view of a cement restrictor inserter instrument according to a first embodiment is shown;

[0039] Figure 3 Shows Figure 2 A side elevation view of the cement restrictor inserter portion of the instrument shown in;

[0040] Figures 4A to 4E Shows Figure 2 Various views and cross-sections of a first embodiment of the body portion of the instrument shown in;

[0041] Figure 5 Shows that can be associated with Figure 3Side views of different sized body portions for use with the inserter shown and which may be provided as part of a surgical instrument kit;

[0042] Figure 6 A flow chart is shown which illustrates a method of using a cement restrictor inserter instrument in accordance with one aspect of the present disclosure;

[0043] Figure 7 Illustrates during the method shown in Figure 6 The relationship between the various test pieces, instruments and implants used;

[0044] Figure 8A And Figure 8B Show a side elevation view and a 3D view of a second embodiment of the body portion respectively;

[0045] Figure 9A And Figure 9B Show a side elevation view and a 3D view of a third embodiment of the body portion respectively;

[0046] Figure 10A And Figure 10B Show 3D views of a fourth embodiment of the body portion from top to bottom respectively, which body portion may be used with the inserter of Figure 3 To provide another embodiment of the instrument;

[0047] Figure 11 Shows a 3D view of a cement restrictor inserter instrument according to the second embodiment; and

[0048] Figure 12 Illustrates Figure 11 A 3D view of a fifth embodiment of the body portion used in the instrument shown in

[0049] In the drawings, unless otherwise indicated, the same reference numerals are used to refer to like parts.

[0050] Reference Figure 1 Which illustrates a view of the hip joint of a patient 100 who has undergone total hip replacement surgery. The prosthetic components include an acetabular cup 102 implanted in the prepared acetabulum of the patient's pelvis 104. As Figure 1 Shown, the acetabular cup 102 includes a liner 106 which provides the articulating surface. Also shown is a cross-sectional view of the proximal portion of the patient's femur 110. The femoral portion of the prosthesis includes a femoral head 112 mounted on a femoral stem 114 via a neck 116. The distal end of the femoral stem 114 includes an aligner 118. The femoral stem 114 is located within a cement mantle 120 within the medullary cavity of the femur. A cement restrictor 122 is provided towards the distal end of the medullary cavity. As Figure 1As shown, there is a gap between the farthest part of the femur (stabilizer 118) and the cement restrictor 122 of the side 124, and this gap is preferably about 10 mm - 20 mm.

[0051] Preferably, the thickness of the cement shroud 120 around the stem 114 is a few millimeters, such as about 2 mm, and it is usually centered within the intramedullary cavity of the femur. Similarly, preferably, the distance between the farthest part of the stem and the cement restrictor 124 is sufficient to allow the stem 114 to be placed within the cement. However, if a revision surgery is subsequently required, the distance is not so large that an excessive amount of cement is present within the intramedullary cavity, for example, to avoid difficulty in removing the cement. In fact, the distance 124 is preferably about 20 mm.

[0052] The use of the cement restrictor is generally understood by those of ordinary skill in the art, and the cement restrictor can be used in other orthopedic surgeries where some prosthetic components are cemented in place within the cavity of the patient's bone. As briefly discussed above, preferably, there is a certain limited distance between the cement restrictor and the farthest part of the prosthetic implant component. However, difficulties may arise in attempting to ensure that the cement restrictor 122 is placed at a certain depth within the cavity to possibly create a preferred spacing 124 between the end of the prosthetic component and the cement restrictor. This is not something that can be visually achieved because the cement restrictor 122 is obscured when inserted into the cavity prior to cementing.

[0053] Figure 2 A side view of a cement restrictor inserter instrument 130 according to a first embodiment and having a cement restrictor 150 attached to its distal end is shown. The cement restrictor inserter instrument 130 has a handle portion 132 at the proximal end and an attachment formation (not visible in Figure 2 ), to which the cement restrictor 150 can be releasably attached via the attachment formation at the distal end 134. The shaft 136 extends from the handle portion 132 to the distal end 134. A stop 138 is provided on the shaft between the proximal end and the distal end. A body 140 is provided on the shaft 136. The position of the body 140 along the shaft 136 is controlled by the stop 138 that abuts the spacer portion 142 of the body 140.

[0054] Figure 3 A side elevation view of the cement restrictor inserter 131 as part of the entire instrument 130, with the body 140 omitted, is shown. Thus, the entire instrument 130 can be considered as an assembly of the body 140 and the inserter 131. As Figure 3 shown, the inserter 131 has a configuration of a generally T-shaped bar. The handle portion 132 is in the form of a circular cylindrical cross bar attached to the proximal end of the shaft 136. The shaft 136 has a generally circular rod form. AsFigure 3 As shown, an attachment formation 137 is provided at the distal end 134 of the shaft 136 and, in the illustrated embodiment, may take the form of a thread. However, in other embodiments, the attachment formation may provide a press-fit interface with a corresponding femoral feature in the cement restrictor 150.

[0055] The stop 138 has an expanded portion extending to a diameter larger than that of the shaft 136 and provides an adjacent shoulder portion 139. A circular cylindrical protrusion 152 extends distally and defines a groove or recess 154 therein. A C-clip or circular clip 156 is located within the circular groove 154. The circular clip 156 is generally in the form of a C or open ring of an elastic material such as metal, e.g., stainless steel. Figure 3 The inserter portion 131 of the cement restrictor inserter instrument shown may be made of a suitable metal or alloy, e.g., stainless steel.

[0056] Figures 4A to 4E There is shown generally similar to Figure 2 various views of an additional body 160 similar to the body 140 shown therein. As will be explained in more detail below, Figures 4A to 4E the main difference between the body 160 shown therein and the body 140 shown in Figure 2 is the length of the spacer element in a direction parallel to the axis of the inserter 131, i.e., the shaft 136. Figure 4A There is shown a side elevation view (generally in the anteroposterior direction) of the body 160 and Figure 4B a side elevation view is shown. Figure 4C There is shown a cross-sectional view through the body along line L-L'. Figure 4D There is shown a perspective view of the body 160 and Figure 4E there is shown Figure 4C an enlarged cross-sectional view of a portion 170 of the cross-section of

[0057] As Figure 4A best shown, the body 160 generally has the same shape as the proximal portion of the femoral stem 114 shown in Figure 1 . However, the body 160 corresponds only to the proximal portion of the stem 114 and is truncated distally as the distal portion of the prosthetic stem 114 is not present. Additionally, the body 160 is truncated at the portion corresponding to the neck 116 of the prosthetic stem 114. The portion 162 of the body corresponding to the proximal portion of the stem 114 may also have substantially the same size as the proximal portion of the stem 114. That is, the body 160 has generally the same shape and dimensions as the proximal portion of the corresponding prosthetic component 114.

[0058] It is not important that the body and the corresponding prosthesis be the same size. The body can be a simplified form of the proximal portion of the stem, having generally the same form or shape and being easier and less expensive to machine. Thus, in general, the geometry of the body should approximate that of the corresponding prosthesis to an economically reasonable degree. However, the body should not be longer or wider or thicker than the final drill or trial or cutting instrument used to form the femoral cavity, otherwise the body will contact the inner wall of the femoral cavity prematurely and before the cement restrictor has been inserted to the desired depth.

[0059] The spacer portion 164 extends from the proximal portion of the body 166 and extends generally along the longitudinal axis 168 of the body, which longitudinal axis is generally parallel to the longitudinal axis of the shaft 136 of the inserter 131. As Figure 4C Best shown, the body 162 defines a passage 172 that extends generally along the longitudinal axis and between a lower opening 174 and an upper opening 176 of the spacer 164.

[0060] The spacer element 164 has a generally circular cylindrical configuration and defines a slightly tapered cavity 178 therein. As Figure 4C and Figure 4E Best shown, the inner wall 180 of the spacer defines a groove 182 extending about the longitudinal axis therein. The cavity 178 is sized to closely receive the protrusion 152 therein, and the groove 182 is positioned and sized to receive the circuit 156 therein to provide a releasable attachment mechanism between the body 160 and the remainder of the cement restrictor inserter 130.

[0061] Thus, the body 160 can slide along the shaft 136 of the inserter until the spacer 164 abuts the stop 138 to fix the position of the body relative to the remainder of the inserter. The releasable attachment mechanism prevents the body from being inadvertently removed from the shaft during grasping.

[0062] As Figure 4A Best shown, a visual depth guide feature 190 is provided on the front surface 192 of the body. Similar alignment features are provided on the rear side that is not visible in the drawings.

[0063] In the illustrated embodiment, the visual depth guide feature 190 is in the form of a plurality of markings 194, 196, 198, each marking including a linear segment. The linear segments are arranged generally perpendicular to the direction of the neck axis of the corresponding stem component 114. In fact, corresponding markings 119 can be seen on the stem component 114 in Figure 1 .

[0064] As described above, the body portions 160, 140 of the inserter instrument 130 can be releasably attached to the inserter 131 by sliding along the shaft 136 and releasably attaching to the stop 138. In practice, multiple body portions can be provided, each corresponding to a different-sized prosthetic component. For example, Figure 5 a first body 140, a second body 160, and a third body 200 are shown, each corresponding to a different-sized prosthetic femoral stem. It should be understood that in other embodiments, more or fewer bodies can be provided. In the example described, the first body 140 corresponds to the smallest stem, the second body 160 corresponds to the medium-sized stem, and the third body 200 corresponds to the largest stem.

[0065] Generally, the size of the stem is determined by its dimensions in the inner-outer direction. The length of the stem can also vary with the size of the stem, such that a smaller stem will have a smaller length in the anterior-posterior direction compared to a larger-sized stem. Thus, the first body 140 corresponds to a prosthetic femoral stem having the smallest length in the inferior-superior direction, the second body 160 corresponds to a second prosthetic femoral stem having a length greater than that of the first body in the inferior-superior direction, and the third body 200 corresponds to the largest prosthetic femoral stem having the largest length in the inferior-superior direction.

[0066] Since the distance between the stop 138 and the distal end 134 of the inserter to which the cement restrictor is attached is fixed, the length of the spacer portion of each body decreases as the size of the corresponding stem increases. In this way, by using the visual depth guide feature to be used to control the insertion depth of the cement restrictor 150, the inserter 130 can be used to reliably position the cement restrictor 150 at a preferred spacing from the farthest point of the prosthetic implant.

[0067] The first body 140 corresponds to a prosthetic stem having the shortest length in the inferior-superior direction and thus has the longest spacer portion 142 to position the visual depth guide feature further down the shaft relative to the stop 138. The medium-sized body 160 corresponds to a femoral stem having a greater length in the inferior-superior direction compared to the femoral stem corresponding to the first body 140 and thus has a shorter spacer 164 to position the visual depth guide feature 190 closer to the stop 138.

[0068] The third body 200 corresponds to a femoral stem having the largest length in the inferior-superior direction and thus has the shortest spacer 204 to position the visual depth guide feature 210 closer to the stop 138.

[0069] Upon implantation, the visual depth guide feature can be used to direct the depth of insertion of the cement restrictor 150 into the cavity corresponding to the desired spacing 124 between the cement restrictor and the most distal portion of the prosthetic stem by varying the length of the spacer portion along the longitudinal axis of the body to compensate for different lengths in the superior-inferior direction of the stem corresponding to the body.

[0070] Reference Figure 6 , which shows a flow chart that illustrates a method 300 of using a cement restrictor inserter instrument 130 to insert a cement restrictor 150 at an appropriate depth within the intramedullary cavity of the femur. For clarity, various parts of the entire hip replacement surgery are omitted, but these parts are generally known to those of ordinary skill in the art. Thus, Figure 6 only those parts of the total hip replacement surgery that can be used to explain the use of the inserter instrument 130 are shown. At 302, the femur is prepared. This can include resection of the natural neck of the femur and also formation of an intramedullary cavity that generally extends along the proximal anatomical axis of the femur. Various cutting instruments such as drills and rasps can be used to form the intramedullary cavity. In some embodiments, a trial femoral stem component that also serves as the final drill can be used to form the cavity within the femur.

[0071] For example, Figure 7 shows a cross-sectional view of the proximal portion 110 of a patient's femur and shows the resection plane 113 resulting from resection of the natural femoral neck. The illustrated trial femoral stem 400 has a neck 402 and cutting teeth 404 disposed on the stem and has been used to drill the femoral cavity. The anterior sidewall of the trial stem 400 includes a visual depth guide feature 406 that is similar to those present on a body such as body 140 and corresponding prosthetic femoral stem component 114. The visual depth guide feature 406 is similarly in the form of three parallel lines that are generally perpendicular to the neck axis of the stem. Each of these lines corresponds to a different amount of offset of the femur relative to the pelvis in the medial-lateral and superior-inferior directions. The middle line 408 can correspond to a neutral amount of medial-lateral offset and superior-inferior offset (also referred to as leg length). The upper line 410 can correspond to a reduced amount of superior-inferior offset and medial-lateral offset. The lower line 412 can correspond to an increased amount of medial-lateral offset and superior-inferior offset. Thus, the surgeon can use the trial stem 400 to complete drilling of the intramedullary cavity of the femur until one of the marks corresponding to the desired change in offset (if any) aligns with the resection plane of the femur. As Figure 7 shown, the neutral offset line 408 is generally aligned with the resection plane 113 of the femur.

[0072] The femur test piece 400 has a prosthetic femoral stem 114 of corresponding dimensions. However, the dimensions of the prosthetic femoral stem 114 are slightly smaller than those of the test stem 400 to provide a cement mantle 120 around the prosthetic stem 114. Thus, once the test is completed at 304, the surgeon can determine the size of the prosthetic femoral stem corresponding to the test femoral stem 400.

[0073] As Figure 7 Further shown, the body 140 has a shape and dimensions corresponding to the prosthetic femoral stem 114. Thus, at 306, the surgeon can select a body corresponding to the selected size of the prosthetic femoral stem 114 for the inserter.

[0074] At 308, the selected body 104 can be attached to the inserter 131 by sliding axially and attaching via a releasable attachment mechanism. As discussed above, the position of the body 140 along the longitudinal axis of the inserter is determined by the spacer portion 142 abutting against the stop 138.

[0075] Then at 310, the cement restrictor test piece can be attached to the distal end of the inserter instrument 130. Then, the inserter instrument 130 can be used to introduce the cement restrictor test piece into the intramedullary cavity of the femur. Generally, the purpose of the cement restrictor test piece is to measure the appropriate diameter of the cement restrictor to be used. Thus, the surgeon can move the cement restrictor test piece distally into the intramedullary cavity to measure the diameter of the intramedullary cavity near the intended target position of the cement restrictor. Since precise positioning of the test piece is not required, this can be done simply by feel. Alternatively or in addition, at 312, the surgeon can use the visual depth guide feature 144 on the front surface of the body by comparing the position of a marker (e.g., marker 408) relative to the resection plane 113 of the femur corresponding to a previously planned position.

[0076] At 314, the surgeon can determine whether the cement restrictor test piece has the appropriate diameter for the target insertion depth. If it does not have the appropriate diameter, then as shown by the flow line 316, the method can return to step 310, and a different cement restrictor test piece can be attached to the distal end of a larger or smaller diameter introducer. Thus, the method can be repeated until the diameter of the cement restrictor has been successfully determined.

[0077] At 318, after the cement restrictor test piece has been removed, a cement restrictor having a diameter determined by testing is releasably attached to the distal end of the rod. In embodiments where a threaded connection is used, the cement restrictor is then screwed onto a screw formation at the distal end 134 of the inserter instrument 130. In other embodiments where a press-fit attachment mechanism is used, the cement restrictor 150 can then simply be pushed onto the distal end 134 of the inserter instrument 130. Then at 320, the cement restrictor 150 is introduced into the intramedullary cavity and the cement restrictor 150 is inserted into the intramedullary cavity using the inserter 130. The shape of the body 140 helps to ensure that the longitudinal axis of the inserter 130 is generally aligned with the central axis of the cavity and not tilted in the coronal plane. However, the size of the body 140 is smaller than the size of the trial stem 400 and thus does not itself limit the insertion depth of the cement restrictor. Rather, the shape of the body helps to provide a visual context to the surgeon regarding the correct insertion depth of the cement restrictor. Specifically, the visual depth guide feature on the body 140 corresponds to the visual depth guide feature 406 on the trial stem and also corresponds to the visual depth guide feature 119 on the prosthetic stem.

[0078] Accordingly, the surgeon can advance the inserter instrument into the medullary canal until a marker (in this example, the center line) corresponding to a previous trial mark is aligned with the resection plane 113 of the femur. The surgeon can now be confident that the cement restrictor 150 has been positioned at the target depth within the medullary cavity of the femur and that, when inserted at the corresponding location within the medullary cavity, the cement restrictor will have an appropriate degree of spacing 124 from the most distal part of the prosthetic stem 114, as defined by the same midline that aligns with the resection plane 113 of the visual depth guide feature 119.

[0079] Accordingly, in embodiments where a press-fit is used, the greater frictional force between the inner wall of the femur and the outer surface of the cement restrictor will overcome the frictional force of the press-fit interface between the distal end of the inserter and the cement restrictor, and thus the inserter instrument 130 can simply be removed from the intramedullary cavity, thereby fixing the cement restrictor 150 in place at the target depth.

[0080] Alternatively, if a threaded attachment is used, the handle 132 can be used to rotate the shaft 136, which can rotate relative to the body 140, thereby allowing the distal end 134 of the inserter to disengage from the cement restrictor 150. The circular clip and groove releasable attachment mechanism allows the shaft 136 to rotate relative to the body, thereby allowing the threaded attachment mechanism to separate. Accordingly, at 322, the inserter disengages from the cement restrictor, which remains in place at the target depth, as Figure 1 shown.

[0081] Thus, the cement can be introduced into the medullary canal, and then the prosthetic stem 114 can be introduced and positioned such that the center mark of its corresponding visual depth guide feature is aligned with the resection plane 113 of the femur.

[0082] Reference Figure 8A and Figure 8B , which show side and perspective views of another embodiment of the body 500 that can be part of a cement restrictor inserter instrument. The body 500 is generally similar to the first embodiment described above, rather than a releasable attachment mechanism, through which the body is releasably attached to the stop of the inserter. Figure 8A and Figure 8B The body 500 shown in has the same geometric structure and dimensions as the body 140 shown in Figure 2 , Figure 5 and Figure 7 . The body 500 generally has a shape and dimensions corresponding to the proximal portion of the corresponding femoral stem 114. Visual depth guide features 502 in the form of multiple markers each including a line are provided on the front surface 504 of the body 500.

[0083] Similarly, the spacer 506 extends generally along the longitudinal axis of the body from the upper portion of the body 500 and defines a circular cylindrical cavity therein for receiving the shaft 136 of the inserter 131 in use. The proximal end of the spacer 506 defines a shoulder 508 that is arranged to abut against the stop 138 of the inserter. However, in the illustrated embodiment, the releasable attachment mechanism 510 is in the form of a snap-fit connector including four resilient tongues, rather than using a circular clip and groove. The stop 138 of the inserter 131 defines a generally annular cavity therein and also defines a groove within the inner wall of the spacer that is configured to receive a protrusion, such as the protrusion 512 of the tongue 514, at the free end of the tongue. Thus, the body 500 can be used in a manner generally similar to the first embodiment described above. Also, the snap-fit of the attachment mechanism allows the shaft of the inserter to rotate relative to the body, and thus the cement restrictor inserter provided with the body can be used with a cement restrictor attached via a press-fit or screw-fit connection.

[0084] Figure 9A and Figure 9BShows a side view and a perspective view of a third embodiment of the body 600. Similarly, the body 600 has the shape and size corresponding to the prosthetic femoral stem 114 and includes a visual depth guide feature 602 on its front surface 604. In the illustrated embodiment, the visual depth guide feature 602 is in the form of a plurality of circles or dots equally spaced along an axis parallel to the longitudinal axis of the body 600. The body 600 generally corresponds to the body 200 and similarly includes a spacer element 606 extending from the upper end portion of the body 600. The proximal surface 608 of the spacer 606 is arranged to abut against the stopper 138 of the inserter to control the position of the body relative to the inserter instrument.

[0085] However, as Figure 9B best shown, the releasable attachment mechanism of the body 600 is provided by a generally open channel 610 defined by portions of the front surface 604 and the rear surface 612 of the body. The channel 610 extends generally along the longitudinal axis of the body and is sized to receive the shaft 136 of the inserter 131 immediately below the stopper 138. When using this body, the inserter 131 omits the protrusion 152 such that the body 600 can simply be clipped onto the shaft 136 of the inserter, with the spacer 606 abutting the farthest surface of the stopper 138. The body 600 is made of a suitable plastic material to provide a snap-fit releasable attachment mechanism. Also as Figure 9B shown, a groove 614 can be defined by the inner surface wall 616 of the channel 610. A protruding ring can extend around the shaft 136 of the inserter 131 and is positioned to be received within the groove 614 when the surface 608 abuts the distal surface of the stopper 138 to ensure the correct relative positioning of the body 600 relative to the stopper 138 and to prevent the body from sliding distally downward along the shaft 136 into an incorrect relative position. The material ring can be an integral part of the shaft formed by machining rather than some separate part subsequently attached to the shaft.

[0086] It should be understood that the use of the cement restrictor is not limited to femoral stems and can in fact be used with other cemented orthopedic implants having some shank portion that extends into a cavity and is not visible to the surgeon. The use of a body having the same shape and size as the proximal portion of the corresponding prosthetic implant is intended to help the surgeon better understand and / or recollect whether the insertion depth of the cement restrictor is correct by comparing some visual depth guide features with some portion of the patient's bone, but within the common context of the body and the corresponding prosthetic implant. In many embodiments, the body itself is not used to control the insertion depth. And due to the required clearance between the wall of the cavity and the prosthetic implant, the body will have a smaller size than the cavity to receive the cement cavity. By partially filling the proximal portion of the cavity, the body can help with the centering of the inserter. However, the shape and dimensions of the body are more intended to provide visual and contextual feedback to the surgeon such that they can immediately understand that the body is in the correct position when the implant will be in that same position.

[0087] Due to the length of the spacer element and the position of the visual depth guide features on the body along an axis generally parallel to the axis of the inserter, the relative position of the cement restrictor for a currently selected body size is determined by the correct positioning of the body on the rod. Thus, the same inserter axis can be used with multiple different bodies corresponding to different sized prosthetic implants having different sized stem lengths.

[0088] Thus, one aspect of the present disclosure also relates to a partial kit or surgical system that includes an inserter instrument, a plurality of bodies of different sizes, and optionally a plurality of corresponding prosthetic implants of different sizes.

[0089] Other common orthopedic implants that can use cemented stems include humeral stems, conventional and reverse shoulders, and tibial components and femoral components of knee prostheses. Some femoral components include cemented stems, especially those for revision surgeries.

[0090] For example, in Figure 10A and Figure 10B a body 650 having the shape and size of a corresponding prosthetic tibial component is shown. The prosthetic tibial component can generally have the form of a tibial tray where a stem extends from the lower surface and provides an attachment mechanism for a bearing surface on the upper side. Thus, when using a tibial tray with a cemented stem, the same general method can also be used where the body 650 has the shape and size of the proximal portion of the tibial prosthesis, i.e., not including at least the farthest portion of the stem.

[0091] For example, as Figure 10A and Figure 10BAs shown, the body 650 includes a tibial tray portion 652 having the general shape and dimensions of the tibial tray of the corresponding prosthetic component. At least a portion of the tibial stem 654 extends from the lower side surface 656 of the tibial tray portion 652 in a downward direction. A pair of wings or flanges 658, 660 extend between the stem 654 and the lower side surface 656 of the tray 652. Similar to the above-described body, the spacer 662 generally extends from the upper surface 664 of the tray 652 in the direction of the inferior-superior axis and parallel to the longitudinal axis of the shaft 136 of the inserter 131. The spacer 662, the tray portion 652, and the stem portion 654 therebetween define a central circular cylindrical cavity 666 into which the shaft 136 of the inserter 131 is inserted in use. The inner surface 668 of the spacer 662 defines a groove 670 that is arranged to receive a circular clip of the inserter 131 to provide a releasable attachment mechanism that also allows the shaft 136 to rotate relative to the body 650.

[0092] The length of the spacer 662 in the direction of the longitudinal axis of the shaft 136 is selected such that when the free end of the spacer 662 abuts the stop 138 when mounted on the inserter 131, the cement restrictor will be positioned at the appropriate distance 124 from the most distal portion of the stem of the corresponding prosthetic component when the lower side or lower surface 656 of the tray 652 is located on the resected surface of the tibia (produced by the proximal tibial cut) within the intramedullary cavity of the tibia. Thus, in this embodiment, the correct positioning of the cement restrictor is determined by the surgeon observing that the tibial tray portion 652 lies flush on the resected tibial surface, rather than by comparing a mark on the body or a structural portion of the body to some portion of the patient's bone. Thus, in this embodiment, the lower surface or lower side surface 656 of the tray portion 652 provides a visual depth guide feature of the body 650 by which the surgeon can visually assess the insertion depth of the cement restrictor.

[0093] By way of another example, Figure 11Shows another embodiment of a cement restrictor inserter instrument 700, which includes a body 710 that generally has the shape and size of a humeral stem or shoulder stem prosthesis. Shoulder stem prostheses are commonly used in reverse shoulder arthroplasty surgeries. The shoulder stem prosthesis is inserted into the intramedullary cavity of the patient's humerus to provide a shallow cup into which a bearing component can be inserted to provide an articulating surface for a corresponding ball-shaped prosthetic implant positioned within the patient's shoulder. Thus, the body 710 generally has the shape and form of a humeral prosthetic implant that includes a portion of the stem 712 and a cup portion 714. The cup portion 714 includes a generally annular wall 716, the upper edge or surface 718 of which provides a visual depth guide feature for evaluating the correct positioning of the cement restrictor inserter within the intramedullary cavity of the humerus. Similarly, a spacer portion 720 extends from the upper portion of the body 710, with a groove 722 defined within the inner surface 724 of the spacer portion 720 for releasably attaching the body 710 to a circular clamp of the inserter 131. The spacer 720, the cup portion 714, and the stem portion 712 therebetween define a central circular cylindrical cavity 726 into which the shaft 136 of the inserter 131 is inserted in use.

[0094] The length of the spacer 720 in the direction of the longitudinal axis of the shaft 136 is selected such that when the free end of the spacer 720 abuts the stop 138 when mounted on the inserter 131, the cement restrictor will be positioned at an appropriate distance 124 from the most distal part of the stem of the corresponding prosthetic component when the surface 718 of the wall 716 is aligned with the edge of the cavity formed in the proximal portion of the humerus. Figure 11 The use of the cement restrictor inserter instrument 700 shown in is generally similar to the cement restrictor inserter instrument referenced above Figure 2 described, except that the correct depth of insertion of the cement restrictor 150 is determined by aligning the edge or surface 718 of the body with the resected or otherwise prepared portion of the patient's humerus.

[0095] The above-described body portion can be made of various materials, and various plastics (especially polymeric plastics) are particularly suitable. For example, the body portion can be made of acetal or polyoxymethylene (POM), polyphenylsulfone (PPS), polyetheretherketone (PEEK), polyaryletherketone (PAEK), or the like, as well as filled forms of those plastics or the like.

[0096] Thus, it is evident that there are many different benefits provided by the various instrument sets described herein and the methods enabled thereby.

[0097] In this specification, exemplary embodiments have been presented in terms of a selected set of details. However, those of ordinary skill in the art will understand that many other exemplary embodiments may be practiced that include combinations of different selections of these details. The following claims are intended to cover all possible exemplary embodiments.

[0098] The steps of the flowcharts in the figures above may be performed in other orders, unless inherently required or explicitly stated in a particular order. Additionally, those skilled in the art will recognize that while one exemplary method has been discussed, the materials in this specification may also be combined in many ways to produce other examples, and should be understood within the context provided by this specific implementation.

[0099] Although the present disclosure is susceptible to various modifications and alternative forms, specific details thereof have been shown by way of example in the drawings and are described in detail. However, it should be understood that other embodiments are possible in addition to the specific embodiments described. All modifications, equivalents, and alternative embodiments falling within the scope of the appended claims are also contemplated.

Claims

1. A cement restrictor inserter instrument, comprising: An inserter having a handle at a proximal end, a cement restrictor attachment formation at a distal end for releasably attaching a cement restrictor, a shaft extending from the proximal end to the distal end, and a stop located on the shaft between the proximal end and the distal end; And A body having a shape corresponding to the shape of an orthopaedic prosthetic implant, a spacer, a visible depth guide feature, and a releasable attachment mechanism by which the body can be releasably attached to the shaft, and wherein the spacer is configured to position the visible depth guide feature in a fixed position relative to the inserter when the spacer abuts the stop, the fixed position corresponding to a target cement restrictor position when the visible depth guide feature is aligned with a feature of the patient's bone into which the cement restrictor is to be inserted.

2. The cement restrictor inserter instrument according to claim 1, wherein, The releasable attachment mechanism includes a push-fit mechanism or a snap-fit mechanism.

3. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The stop includes an attachment formation, and wherein the releasable attachment mechanism interacts with the attachment formation.

4. The cement restrictor inserter instrument according to claim 3, wherein, The attachment formation includes a circular clip located within a portion of the stop, and the releasable attachment mechanism of the body includes a groove configured to receive the circular clip.

5. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The body defines an open channel or a closed channel extending along a longitudinal axis of the body and configured to receive the shaft.

6. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The releasable attachment mechanism permits rotation of the shaft relative to the body.

7. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The cement restrictor attachment formation includes a push-fit formation.

8. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The cement restrictor attachment formation includes a thread.

9. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The visible depth guide feature includes a surface or an edge of a portion of the body.

10. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The visible depth guide feature includes a mark on a surface of a portion of the body.

11. The cement restrictor inserter instrument according to claim 10, wherein, The visible depth guide feature includes a plurality of marks on the surface of the portion of the body, and wherein each of the plurality of marks corresponds to a different position of the orthopaedic prosthetic implant relative to the patient's bone.

12. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The orthopaedic prosthetic implant is a humeral stem, a femoral stem, a femoral component of a knee, or a tibial component.

13. The cement restrictor inserter instrument according to claim 1 or 2, wherein, The body has a size corresponding to the size of the orthopaedic prosthetic implant.

14. A kit of surgical instrument parts, comprising: The cement restrictor inserter instrument according to any one of claims 1 to 13; And An additional body having a shape corresponding to the shape of the orthopaedic prosthesis implant, an additional spacer, an additional visible depth guide feature and an additional releasable attachment mechanism, the additional body being releasably attachable to the shaft by the additional releasable attachment mechanism, and wherein the additional body has a different size from the body and corresponds to the shape of the orthopaedic prosthesis implant of a different size, and wherein the additional spacer has a different size from the spacer and is configured to position the additional visible depth guide feature at a different fixed position relative to the inserter when the additional spacer abuts the stop, the different fixed position corresponding to the target cement restrictor position when the additional visible depth guide feature is aligned with the feature of the bone of the patient into which the cement restrictor is to be inserted.

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