Surgical instruments and methods

Abstract

The cement restrictor inserter instrument (130) comprises an inserter (131) having a handle (132) at its proximal end, a cement restrictor attachment formation (137) at its distal end for releasably attaching a cement restrictor (150), a shaft (136) extending from its proximal end to its distal end, and a stop (138) on the shaft and between its proximal and distal ends, and a body (140) adapted to accommodate the shape of an orthopedic prosthetic implant. The inserter includes a body (140) having a shape, a spacer (142), a visible depth guide feature (190), and a releasable attachment mechanism by which the body can be releasably attached to the shaft, wherein the spacer is configured to position the visible depth guide feature in a fixed position relative to the inserter when the spacer abuts a stop that corresponds 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 inserted.

Description

[Technical field]

[0001] The present disclosure relates to surgical instruments and methods, and particularly, but not exclusively, to surgical instruments and methods for placing a cement restrictor during an orthopaedic surgical procedure. [Background technology]

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

[0003] In some cases, a cement restrictor may be inserted into the cavity before the cement is introduced. The cement restrictor may serve a variety of purposes. It may provide a solid base against which the cement may be pressurized to ensure good introduction of the cement into the cavity. Additionally or alternatively, the cement restrictor may prevent or reduce the amount of cement beyond and into the prepared cavity. Excess cement in the cavity may cause problems if a revision surgery is required later, for example, requiring the excess cement to be removed from the cavity during the revision surgery.

[0004] Regardless of the reason for using a cement restrictor, there is generally a preferred location or depth within the cavity where the cement restrictor should be placed. This preferred location or depth may be related to the location of the prosthetic implant to try 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 can create the same potential problems with revision surgery discussed above, while too little can reduce the ability to properly stabilize the prosthetic implant after insertion and / or properly secure the implant within the cavity.

[0005] Thus, it is generally desirable to properly position the cement restrictor. However, the correct location of the cement restrictor may be a function of the size and / or type of implant being used. Also, when the cement restrictor is hidden from view in some cavities, the surgeon has no easy way to visualize the location of the cement restrictor during insertion.

[0006] Introducers for cement restrictors have various markings thereon to provide the surgeon with some guidance as to the depth to which the cement restrictor is inserted. However, these markings may be difficult to see and / or read during surgery. Also, the anatomical features to which these markings should be aligned may be difficult to visualize at the surgical site and / or may be unclear. Also, there may not be a clear relationship between the various markings and the insertion depth the surgeon is currently trying to achieve with the intended prosthetic implant. It may be difficult for the surgeon to reliably remember which of multiple markings to currently use. This problem is exacerbated in more sophisticated implant systems where the proper location of the cement restrictor varies more intricately with the different sizes of implants that may be available. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, instruments and methods that can facilitate the ease and / or reliability with which a cement restrictor can be positioned would be beneficial. [Means for solving the problem]

[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 a proximal end to a distal end, and a stop on the shaft and between the proximal and distal ends; and a body having a shape corresponding to a shape of an orthopedic 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, 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 corresponding to a target cement restrictor position when the visible depth guide feature is aligned with a feature of a patient's bone into which the cement restrictor is to be inserted.

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

[0010] The holddown 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-clip or circlip and a groove configured to receive the C-clip or circlip. The C-clip or circlip may be within a portion of the fastener and / or the releasable attachment feature of the body may include the groove.

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

[0013] The releasable attachment mechanism may be a rotary releasable attachment mechanism. The releasable attachment mechanism may allow rotation of the shaft relative to the body.

[0014] The cement restrictor attachment formation may include a push-fit formation.

[0015] The cement restrictor attachment formation may include a rotary attachment mechanism, which may be a screw thread.

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

[0017] The visible depth guide feature may include a single marking on a surface of a portion of the body.

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

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

[0020] The body may have a size corresponding to a size of an orthopedic prosthetic implant.The body may have a size having a dimension corresponding to within 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm of a size of an orthopedic prosthetic implant.

[0021] The body may be attached to the inserter with a spacer that abuts, engages, or mates with the stop.

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

[0023] A further 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 a shape of an orthopedic prosthetic implant to be implanted in the cavity of 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; and inserting the cement restrictor inserter with the body mounted thereon into the cavity to a depth determined by alignment of the visible depth guide feature with a feature of the patient's bone.

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

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

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

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

[0028] The patient's bone features may be anatomical features of the patient's bone.

[0029] The feature of the patient's bone may be a resected surface, or an edge, or a periphery 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 may be a single marking on the surface of the body.

[0032] The visual depth guide feature may include a plurality of markings on a surface of the body, each of which may correspond to a different position, e.g., an insertion depth, of the orthopaedic prosthetic implant relative to the patient's bone. The method may further include determining a depth to which the cement restrictor inserter is to be inserted using the marking corresponding to a selected one of the different positions.

[0033] The prosthetic orthopaedic implant can be a femoral stem. The patient's bone feature can be a femoral neck resection or a femoral neck resection.

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

[0035] The prosthetic orthopaedic implant can be a humeral stem. The patient's bone feature can be a proximal resection of the humerus or the periphery of a cavity reamed in the proximal humerus. [Brief description of the drawings]

[0036] Embodiments will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] 1 is a diagram of a prosthetic hip joint illustrating a preferred relative positioning of a prosthetic stem implant and a cement restrictor within a patient's femur; [Diagram 2] FIG. 2 is a 3D view of a cement restrictor inserter instrument according to a first embodiment. [Diagram 3] FIG. 3 is a side view of the cement restrictor inserter component of the instrument shown in FIG. 2. [Figure 4A] 3A-3C are various views and cross-sectional views of a first embodiment of the body portion of the device shown in FIG. 2. [Figure 4B] 3A-3C are various views and cross-sectional views of a first embodiment of the body portion of the device shown in FIG. 2. [Figure 4C] 3A-3C are various views and cross-sectional views of a first embodiment of the body portion of the device shown in FIG. 2. [Figure 4D] 3A-3C are various views and cross-sectional views of a first embodiment of the body portion of the device shown in FIG. 2. [Figure 4E] 3A-3C are various views and cross-sectional views of a first embodiment of the body portion of the device shown in FIG. 2. [Diagram 5]4A-4D are side views of different sized body portions that can be used with the inserter shown in FIG. 3 and that may be provided as part of a surgical instrument kit. [Figure 6] 1 is a flow chart illustrating a method of use of a cement restrictor inserter instrument according to one aspect of the present disclosure. [Figure 7] 7 illustrates the relationship of the various trials, instruments, and implants used during the method illustrated in FIG. 6. [Figure 8A] 4A and 4B are side and 3D views, respectively, of a second embodiment of a body portion. [Figure 8B] 4A and 4B are side and 3D views, respectively, of a second embodiment of a body portion. [Figure 9A] 11A and 11B are a side view and a 3D view, respectively, of a third embodiment of a body portion. [Figure 9B] 11A and 11B are a side view and a 3D view, respectively, of a third embodiment of a body portion. [Figure 10A] 5A and 5B are 3D views, respectively, from above and below, of a fourth embodiment of a body portion that can be used with the inserter of FIG. 3 to provide a further embodiment of the device. [Figure 10B] 5A and 5B are 3D views, respectively, from above and below, of a fourth embodiment of a body portion that can be used with the inserter of FIG. 3 to provide a further embodiment of the device. [Figure 11] FIG. 3D is a 3D view of a cement restrictor inserter instrument according to a second embodiment. [Figure 12] FIG. 12 is a 3D view of a fifth embodiment of a body portion for use in the instrument shown in FIG. 11.

[0037] In the drawing figures, the same reference numbers are used to refer to the same parts unless otherwise indicated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Referring to FIG. 1, a diagram of the hip joint of a patient 100 who has undergone a total hip replacement surgical procedure is shown. The prosthetic components include an acetabular cup 102 implanted in a prepared acetabulum of the patient's pelvis 104. As illustrated in FIG. 1, the acetabular cup 102 includes a liner 106 that provides an articulating surface. Also shown is a cross-sectional view of a proximal portion of the patient's femur 110. The femoral component of the prosthesis includes a femoral head 112 attached via a neck 116 to a femoral stem 114. The distal end of the femoral stem 114 includes a centralizer 118. The femoral stem 114 sits within a cement mantle 120 within the intramedullary cavity of the femur. Towards the distal end of the intramedullary cavity a cement restrictor 122 is provided. As illustrated in FIG. 1, there is a gap between the distal most portion of the femur (stabilizer 118) and the cement restrictor 122 on the side surface 124, preferably about 10-20 mm.

[0039] Preferably, the cement mantle 120 has a thickness of a few millimeters, for example about 2 mm, around the stem 114, which is approximately centrally located in the intramedullary cavity of the femur. Also, preferably, the distance between the most distal part of the stem and the cement restrictor 124 is sufficient to allow the stem 114 to be submerged in the cement. However, if a revision surgery is required later, it is not good to have too much cement in the intramedullary cavity, for example to avoid difficulties in removing the excess cement. In practice, the distance 124 is preferably about 20 mm.

[0040] The use of cement restrictors is generally understood by those skilled in the art, and cement restrictors can be used in other orthopedic procedures where several prosthetic components are cemented in place within a cavity in a patient's bone. As briefly discussed above, preferably there is some finite distance between the cement restrictor and the distal majority of the prosthetic implant component. However, a problem arises in trying to ensure that the cement restrictor 122 is placed at a depth within the cavity that will create a desired separation 124 between the end of the prosthetic component and the cement restrictor. This is not something that can be accomplished visually, as the cement restrictor 122 is hidden from view when inserted into the cavity prior to cementation.

[0041] 2 shows a side view of a cement restrictor inserter instrument 130 according to a first embodiment and with a cement restrictor 150 attached to its distal end. The cement restrictor inserter instrument 130 has a handle 132 at a proximal end and an attachment formation at a distal end 134 (not visible in FIG. 2) by which the cement restrictor 150 can be removably attached to the inserter instrument 130. A shaft 136 extends from the handle 132 to the distal end 134. A stop 138 is provided on the shaft between the proximal and distal ends. 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 abutting a spacer portion 142 of the body 140.

[0042] FIG. 3 shows a side view of the cement restrictor inserter 131, which is a portion of the overall instrument 130, with the body 140 removed. The overall instrument 130 may therefore be considered an assembly of the body 140 and the inserter 131. As illustrated in FIG. 3, the inserter 131 has a generally T-bar configuration. The handle 132 is in the form of a cylindrical crossbar attached to the proximal end of the shaft 136. The shaft 136 has the form of a generally circular rod. As illustrated in FIG. 3, an attachment formation 137 is provided on the distal end 134 of the shaft 136, which in the illustrated embodiment may take the form of a screw thread. However, in other embodiments, the attachment formation may provide a push-fit interface with a corresponding femoral feature of the cement restrictor 150.

[0043] The stop 138 has a flared portion that extends to a larger diameter than the shaft 136 and provides an abutting shoulder portion 139. A cylindrical boss 152 extends toward the distal end and defines a groove or recess 154 therein. A C-clip or circlip 156 sits within the circular groove 154. The circlip 156 is generally in the form of a C-ring or split ring of a resilient material such as a metal, e.g., stainless steel. The inserter part 131 of the cement restrictor inserter instrument illustrated in FIG. 3 may be made from a suitable metal or alloy, e.g., stainless steel.

[0044] 4A-4E show various views of a further body 160 substantially similar to the body 140 illustrated in FIG. 2. As will be explained in more detail below, the major difference between the body 160 shown in FIGS. 4A-4E and the body 140 shown in FIG. 2 is the length of the spacer elements along a direction parallel to the axis of the shaft 136 of the inserter 131. FIG. 4A shows a side view (generally anterior-posterior) of the body 160, and FIG. 4B shows a side view. FIG. 4C shows a cross-sectional view through the body along line L-L'. FIG. 4D shows a perspective view of the body 160, and FIG. 4E shows an enlarged cross-sectional view of a portion 170 of the cross-section of FIG. 4C.

[0045] As best illustrated in FIG. 4A, the body 160 generally has the same shape as the proximal portion of the femoral stem 114 illustrated in FIG. 1. However, the body 160 is truncated distally in that it corresponds only to the proximal portion of the stem 114 and not to the distal portion of the prosthetic stem 114. The body 160 is also truncated at a portion that corresponds to the neck 116 of the prosthetic stem 114. The portion 162 of the body that corresponds to the proximal portion of the stem 114 may also have substantially the same dimensions as the proximal portion of the stem 114. That is, the body 160 generally has the same shape and size as the proximal portion of the corresponding prosthetic component 114.

[0046] It is not essential that the dimensions of the body and the corresponding prosthesis are identical. The body can be a simplified version of the proximal portion of the stem that has roughly the same form or shape and is easier and less expensive to machine. Thus, generally speaking, the body should be as close as possible to the geometry for which the corresponding prosthesis is economically reasonable. However, the body should not be longer, wider, or thicker than the final broach, or trial, or cutting instrument used to prepare the femoral cavity, otherwise it will contact the interior wall of the femoral cavity prematurely and before the cement restrictor has been inserted to the desired depth.

[0047] The spacer portion 164 extends from a proximal portion of the body 166 and generally along a longitudinal axis 168 of the body that is generally parallel to the longitudinal axis of the shaft 136 of the inserter 131. As best illustrated in FIG. 4C, the body 162 defines a channel 172 that extends generally along the longitudinal axis between a lower opening 174 and an upper opening 176 of the spacer 164.

[0048] The spacer element 164 has a generally cylindrical configuration and defines a slightly tapered cavity 178 therein. As best illustrated in Figures 4C and 4E, an inner wall 180 of the spacer defines a groove 182 therein that extends about a longitudinal axis. The cavity 178 is sized to snugly receive the boss 152 therein, and the groove 182 is positioned and dimensioned 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.

[0049] Thus, the body 160 can be slid along the inserter shaft 136 until the spacer 164 abuts the stop 138, fixing the position of the body relative to the rest of the inserter. The releasable attachment mechanism prevents the body from being unintentionally detached from the shaft during handling.

[0050] As best illustrated in Figure 4A, visual depth guide features 190 are provided on the front side 192 of the body. Similar alignment features are provided on the rear side, which is not visible in the drawing.

[0051] In the illustrated embodiment, the visual depth guide feature 190 is in the form of a plurality of markings 194, 196, 198, each comprising a straight section, configured generally perpendicular to the direction of the cervical axis of the corresponding stem component 114. Indeed, a corresponding marking 119 can be seen on the prosthetic stem component 114 in FIG.

[0052] As explained above, the bodies 160, 140 of the inserter tool 130 are releasably attachable to the inserter 131 by sliding them along the shaft 136 and releasably attaching to the stop 138. In practice, multiple bodies may be provided, each corresponding to a different size of prosthetic component. For example, FIG. 5 shows a first body 140, a second body 160, and a third body 200, each corresponding to a different size prosthetic femoral stem. It will be understood that in other embodiments, a greater or lesser number of bodies may be provided. In this illustrated example, the first body 140 corresponds to the smallest stem, the second body 160 corresponds to a medium sized stem, and the third body 200 corresponds to the largest stem.

[0053] Generally speaking, the size of a stem is determined by its size in the medial-lateral direction. The length of the stem may also vary with the size of the stem, such that smaller stems have a shorter length in the anterior-posterior direction than larger sized stems. Thus, the first body 140 corresponds to a prosthetic femoral stem having the shortest length in the superior-inferior direction, the second body 160 corresponds to a second prosthetic femoral stem having a length in the superior-inferior direction that is longer than the first length, and the third body 200 corresponds to a largest prosthetic femoral stem having the longest length in the superior-inferior direction.

[0054] Because the distance between the stop 138 and the inserter's distal end 134 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 manner, the inserter 130 can be used to reliably position the cement restrictor 150 preferably spaced apart from the most distal point of the prosthetic implant by using a visual depth guide feature that is used to control the insertion depth of the cement restrictor 150.

[0055] The first body 140 accommodates a prosthetic stem having the shortest vertical length, and therefore has the longest spacer portion 142 to position the visual depth guide feature further down the shaft relative to the stop 138. The intermediate sized body 160 accommodates a femoral stem having a longer vertical length than the femoral stem corresponding to the first body 140, and therefore has a shorter spacer 164 to position the visual depth guide feature 190 closer to the stop 138.

[0056] The third body 200 corresponds to a femoral stem having the longest length in the vertical direction and therefore has the shortest spacer 204 to position the visual depth guide feature 210 closest to the stop 138.

[0057] By varying the length of the spacer portion along the longitudinal axis of the body to compensate for the different vertical lengths of the stem corresponding to the body, the visual depth guide feature can be used to guide insertion of the cement restrictor 150 to a depth within the cavity corresponding to the desired separation 124 between the cement restrictor and the distal-most portion of the prosthetic stem when implanted.

[0058] Referring to FIG. 6, a flow chart is shown illustrating a method 300 of using the cement restrictor inserter instrument 130 to insert the cement restrictor 150 to the appropriate depth in the intramedullary cavity of the femur. Various components of the entire hip replacement procedure have been removed for clarity, but are generally known to those skilled in the art. Thus, FIG. 6 illustrates only a portion of a total hip replacement procedure that is useful for illustrating the use of the inserter instrument 130. At 302, the femur is prepared. This may include resecting the natural neck of the femur and also forming an intramedullary cavity that extends generally along the proximal anatomical axis of the femur. Various cutting instruments, such as broaches and rasps, may be used to form the intramedullary cavity. In some embodiments, a trial femoral stem component that also functions as a final broach may be used to form the cavity in the femur.

[0059] For example, FIG. 7 shows a cross-sectional view of the proximal portion 110 of a patient's femur, illustrating the resection plane 113 resulting from the resection of the natural femoral neck. A trial femoral stem 400 is shown having a neck 402 and cutting teeth 404 mounted on the stem and used to broach the femoral cavity. The anterior sidewall of the trial stem 400 includes a visual depth guide feature 406 similar to that present on the body, e.g., 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 the lines corresponds to a different amount of offset of the femur relative to the pelvis in the medial-lateral and superior-inferior directions. The intermediate line 408 may correspond to an intermediate amount of medial-lateral offset and inferior-superior offset (also referred to as leg length). The upper line 410 may correspond to a reduced amount of superior-inferior offset and medial-lateral offset. The inferior line 412 may correspond to an increased amount of medial-lateral offset and superior-inferior offset. Thus, the surgeon may use the trial stem 400 to complete broaching of the femoral intramedullary cavity until one of the markings corresponding to the desired change, and offset if applicable, is aligned with the plane of the femoral resection. As illustrated in FIG. 7, the intermediate offset line 408 is generally aligned with the femoral resection plane 113.

[0060] The femoral trial 400 has a correspondingly sized prosthetic femoral stem 114. However, the prosthetic femoral stem 114 has a slightly smaller size than the trial stem 400 to provide for the cement mantle 120 surrounding the prosthetic stem 114. Thus, once trialing is completed at 304, the surgeon may determine the size of the prosthetic femoral stem that corresponds to the trial femoral stem 400.

[0061] 7, the body 140 has a shape and size that corresponds to the prosthetic femoral stem 114. Thus, at 306, the surgeon may select the body of the inserter that corresponds to the selected size of the prosthetic femoral stem 114.

[0062] At 308, the selected body 104 may be attached to the inserter 131 by sliding it along the shaft and may be attached 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 abutment of the spacer portion 142 and the stop 138.

[0063] A cement restrictor trial may then be attached to the distal end of the inserter instrument 130 at 310. The inserter instrument 130 may then be used to introduce the cement restrictor trial into the intramedullary cavity of the femur. Generally, the purpose of the cement restrictor trial is to measure the appropriate diameter of the cement restrictor to be used. Thus, the surgeon may move the cement restrictor trial distally into the intramedullary cavity to measure the diameter of the intramedullary cavity near the intended target location of the cement restrictor. This may be done simply by feel, as precise positioning of the trial is not critical. Alternatively or additionally, at 312, the surgeon may use the visual depth guide feature 144 on the front of the body by comparing the location of a marking, such as marking 408, corresponding to the previously planned location relative to the resection plane 113 of the femur.

[0064] At 314, the surgeon may determine whether the cement restrictor trial has an appropriate diameter for the target insertion depth. If not, the method may return to step 310, as illustrated by flow line 316, and a different cement restrictor trial may be attached to the distal end of the larger or smaller diameter introducer. Thus, the method may be repeated until the cement restrictor diameter is successfully determined.

[0065] At 318, after removing the cement restrictor trial, a cement restrictor having a diameter determined by the trial is releasably attached to the distal end of the rod. In embodiments where a threaded connection is used, the cement restrictor is then threaded into the thread formation on the distal end 134 of the inserter instrument 130. In other embodiments where a push-fit attachment mechanism is used, the cement restrictor 150 may then simply be forced into the distal end 134 of the inserter instrument 130. The cement restrictor 150 is then introduced into the intramedullary cavity at 320, and the inserter 130 is used to insert the cement restrictor 150 into the intramedullary cavity. The shape of the body 140 helps ensure that the longitudinal axis of the inserter 130 is generally aligned with the central axis of the cavity, rather than being tilted in the coronal plane. However, the dimensions of the body 140 are smaller than the dimensions of the trial stem 400, and therefore do not, in and of themselves, limit the insertion depth of the cement restrictor. Rather, the shape of the body assists in providing the surgeon with visual context regarding the correct insertion depth of the cement restrictor. Specifically, the visual depth guide features on the body 140 correspond to the visual depth guide features 406 on the trial stem and also the visual depth guide features 119 on the prosthesis stem.

[0066] Thus, the surgeon may advance the inserter instrument into the intramedullary canal until a marking, in this example a central line, corresponding to a previously trialed marking is aligned with the femoral resection plane 113. At this point, the surgeon can be confident that the cement restrictor 150 has been positioned at the target depth within the femoral intramedullary canal, the target depth position having the appropriate degree of separation 124 from the distal-most portion of the prosthesis stem 114 when inserted into the intramedullary canal at the corresponding location defined by the same midline of the visual depth guide feature 119 that is aligned with the resection plane 113.

[0067] Thus, in embodiments in which a push-fit is used, the greater frictional force between the inner wall of the femur and the outer surface of the cement restrictor overcomes the frictional force of the push-fit interface between the distal end of the inserter and the cement restrictor, and thus the inserter instrument 130 can simply be withdrawn from the intramedullary cavity, leaving the cement restrictor 150 fixed in place at the target depth.

[0068] 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 inserter's distal end 134 to be removed from the cement restrictor 150. The circlip and groove releasable attachment mechanism allows for rotation of the shaft 136 relative to the body, thereby allowing disengagement of the thread attachment mechanism. Thus, at 322, the inserter is separated from the cement restrictor and left in place at the target depth, as illustrated in FIG.

[0069] As a result, cement can be introduced into the intramedullary canal and then into the introduced prosthesis stem 114, positioned with the central marking of its corresponding visual depth guide feature aligned with the resection plane 113 of the femur.

[0070] 8A and 8B, side and perspective views of a further embodiment of a body 500 that may be used as part of a cement restrictor inserter tool are shown. The body 500 is generally similar to the first embodiment described above, except for a releasable attachment mechanism by which the body is releasably attached to a stop on an inserter. The body 500 shown in FIGS. 8A and 8B has generally the same geometric shape and size as the body 140 shown in FIGS. 2, 5, and 7. The body 500 generally has a shape and size corresponding to the proximal portion of a corresponding femoral stem 114. A visual depth guide feature 502 in the form of a plurality of markings, each including a line, is provided on a front surface 504 of the body 500.

[0071] Similarly, the spacer 506 extends from the top of the body 500 generally along the longitudinal axis of the body and defines a 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 configured to abut the stop 138 of the inserter. However, in the illustrated embodiment, instead of using a circlip and groove, the releasable attachment mechanism 510 is in the form of a snap-fit ​​connector including four resilient tongues. The stop 138 of the inserter 131 defines a generally annular cavity therein and also defines a groove in the inner wall of the spacer configured to receive a protrusion on a free end of the tongues, e.g., the protrusion 512 of the tongue 514. The body 500 can therefore be used in a manner generally similar to the first embodiment described above. Again, the snap-fit ​​parts of the attachment mechanism allow the inserter shaft to rotate relative to the body, so that a cement restrictor inserter provided with this body can be used with a cement restrictor attached via a push-fit or threaded fit connection.

[0072] 9A and 9B show side and perspective views of a third embodiment of a body 600. Again, the body 600 has the shape and size of a corresponding prosthetic femoral stem 114 and includes visual depth guide features 602 on its anterior surface 604. In the illustrated embodiment, the visual depth guide features 602 are 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 an upper end of the body 600. A proximal surface 608 of the spacer 606 is arranged to abut the stop 138 of the inserter to control the position of the body relative to the inserter instrument.

[0073] However, as best illustrated in FIG. 9B, the releasable attachment mechanism of the body 600 is provided by a generally open channel 610 defined by a portion 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 just below the stop 138. When using this body, the inserter 131 omits the boss 152, so that the body 600 can simply be clipped onto the shaft 136 of the inserter with the spacer 606 abutting the distal-most surface of the stop 138. The body 600 is made of a suitable plastic material to provide a snap-fit ​​releasable attachment mechanism. As also illustrated in FIG. 9B, the groove 614 can be defined by an inner wall 616 of the channel 610. A proud ring may extend around the shaft 136 of the inserter 131 and be positioned to be received in groove 614 when surface 608 abuts the distal face of stop 138 to ensure correct relative positioning of body 600 with respect to stop 138 and prevent the body from being slid distally down shaft 136 to an incorrect relative position. The ring of material may be an integral part of the shaft formed by machining rather than subsequently attaching several separate pieces to the shaft.

[0074] It will be appreciated that the use of the cement restrictor is not limited to femoral stems, and may in fact be used with other cemented orthopedic implants that have some stem-like portion that extends into the cavity and is not visible to the surgeon. The use of a body having the same shape and dimensions as the proximal portion of the corresponding prosthetic implant is intended to help the surgeon better understand and / or recall whether the insertion depth of the cement restrictor is correct but within the common context of the body and the corresponding prosthetic implant by comparing it to some portion of the patient's bone using some visual depth guide features. In many embodiments, the body itself is not used to control the depth of insertion. Rather, the body has smaller dimensions than the cavity due to the clearance required between the walls of the cavity and the prosthetic implant to receive the cement cavity. The body may aid in some centering of the inserter by partially filling the proximal portion of the cavity. However, the shape and size of the body is further intended to provide visual and contextual feedback to the surgeon so that they can immediately understand that the body is in the correct position when the implant is in that same position.

[0075] The relative position of the cement restrictor with respect to the currently selected body size is addressed by the length of the spacer element along an axis generally parallel to the longitudinal axis of the inserter shaft and the correct positioning of the body on the rod by the location of the visual depth guide features on the body. Thus, the same inserter shaft can be used with multiple different bodies corresponding to different sized prosthetic implants having different sized stem lengths.

[0076] Thus, one aspect of the present disclosure also relates to a kit of parts 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.

[0077] Other common orthopaedic implants that may use cemented stems include humeral stems in both conventional and reverse shoulders, as well as the tibial and femoral components of knee prostheses. Some femoral components, especially those used in revision surgeries, include cemented stems.

[0078] For example, Figures 10A and 10B illustrate a body 650 having the shape and size of a corresponding prosthetic tibial component. The prosthetic tibial component may generally have the form of a tibial tray with a stem extending from the lower surface and providing an attachment mechanism for the upper bearing surface. Thus, if a cemented stem tibial tray is used, the same general approach may also be used, in which the body 650 has a shape and size that does not include the proximal portion of the tibial prosthesis, i.e., at least the most distal portion of the stem. For example, as illustrated in Figures 10A and 10B, the body 650 includes a tibial tray portion 652 having the general shape and size of the tibial tray of the corresponding prosthetic component. At least a portion of a tibial stem 654 extends inferiorly from the lower side 656 of the tibial tray portion 652. A pair of wings or flanges 658, 660 extend between the stem 654 and the lower side 656 of the tray 652. Similar to the body described above, the spacer 662 extends generally in a vertical axial direction from an upper surface 664 of the tray 652 and parallel to the longitudinal axis of the shaft 136 of the inserter 131. The spacer 662, tray portion 652 and stem portion 654 define a central cylindrical cavity 666 therebetween into which, in use, the shaft 136 of the inserter 131 is inserted. An inner surface 668 of the spacer 662 defines a groove 670 arranged to receive a circlip of the inserter 131 to provide a releasable attachment mechanism that also allows the shaft 136 to rotate relative to the body 650.

[0079] The length of the spacer 662 in the direction of the longitudinal axis of the shaft 136 is selected so that when the free end of the spacer 662 is mounted on the inserter 131 and abuts the stop 138, the cement restrictor is located within the tibial intramedullary cavity at an appropriate distance 124 from the distal-most portion of the stem of the corresponding prosthetic component when the lower or underside surface 656 of the tray 652 is seated against the resected surface of the tibia (resulting from the proximal tibial cut). Thus, in this embodiment, the correct positioning of the cement restrictor is determined by the surgeon observing that the tibial tray portion 652 is seated flush against the resected tibial surface, rather than by comparing a marking or feature of the body to some portion of the patient's bone. Thus, in this embodiment, the lower or underside surface 656 of the tray portion 652 provides a visual depth guide feature of the body 650 by which the insertion depth of the cement restrictor may be visually assessed by the surgeon.

[0080] As a further example, FIG. 11 illustrates a further embodiment of a cement restrictor inserter instrument 700 including a body 710 having generally the shape and dimensions of a humeral stem or shoulder stem prosthesis. A shoulder stem prosthesis is typically used in a reverse shoulder arthroplasty procedure. The shoulder stem prosthesis is inserted into an intramedullary cavity in a patient's humerus to provide a shallow cup into which a bearing component may be inserted to provide an articulating surface for a corresponding ball-shaped prosthetic implant located in the patient's shoulder. Thus, the body 710 generally has the shape and configuration of a humeral prosthetic implant, including a portion of a stem 712 and a cup-shaped portion 714. The cup portion 714 includes a generally annular wall 716 and an upper edge or surface 718 that provides a visual depth guide feature used to assess correct positioning of the cement restrictor inserter within the intramedullary cavity of the humerus. Similarly, a spacer portion 720 extends from the top of the body 710 and has a groove 722 defined therein in an inner surface 724 of the spacer portion 720 for releasably mounting the body 710 to a circlip of the inserter 131. The spacer 720, the cup portion 714 and the stem portion 712 define therebetween a central cylindrical cavity 726 into which the shaft 136 of the inserter 131 is inserted in use.

[0081] The length of the spacer 720 in the direction of the longitudinal axis of the shaft 136 is selected so that, when the free end of the spacer 720 is mounted on the inserter 131 and abuts the stop 138, the cement restrictor is positioned within the humeral intramedullary cavity at an appropriate distance 124 from the distal-most portion of the stem of the corresponding prosthetic component when the surface 718 of the wall 716 is aligned with the periphery of the cavity formed in the proximal portion of the humerus. Use of the cement restrictor inserter instrument 700 illustrated in Figure 11 is generally the same as that described above with reference to Figure 2, except that the correct insertion depth of the cement restrictor 150 is determined by aligning an edge or surface 718 of the body with a resected or otherwise prepared portion of the patient's humerus.

[0082] The body described above can be made from a variety of materials, with various plastics being particularly suitable, particularly polymeric plastics, for example the body can be made from acetal or polyoxymethylene (POM), polyphenylsulphone (PPS), polyetheretherketone (PEEK), polyaryletherketone (PAEK), or the like, as well as filled versions or the like of these plastics.

[0083] It will therefore become apparent that there are a number of different benefits provided by the various instrument sets and methods enabled thereby described herein.

[0084] Exemplary embodiments have been presented herein with respect to a selected set of details. However, those skilled in the art will appreciate that many other exemplary embodiments may be practiced that incorporate different sets of these selected details. The following claims are intended to cover all possible exemplary embodiments.

[0085] The steps of the flow charts in the above figures may be performed in other orders unless a particular order is inherently required or explicitly stated. Also, those skilled in the art will recognize that while one exemplary method is discussed, the contents herein may be combined in various ways to yield other examples as well, and should be understood within the context provided by this detailed description.

[0086] While 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 have been described in detail. It will be understood, however, that other embodiments are possible other than the specific embodiments described. All modifications, equivalents, and alternative embodiments falling within the scope of the appended claims are also contemplated.

[0087] [Embodiment] (1) A cement restrictor inserter device 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 said proximal end to said distal end, and a stop on said shaft and between said proximal and distal ends; 1. A cement restrictor inserter instrument comprising: a body having a shape corresponding to a shape of an orthopedic prosthetic implant; a spacer; a visible depth guide feature; and a releasable attachment mechanism by which the body can be releasably attached to the rod, 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 that corresponds to a target cement restrictor position when the visible depth guide feature is aligned with a feature of a patient's bone into which the cement restrictor is to be inserted. (2) The cement restrictor inserter instrument of embodiment 1, wherein the releasable attachment mechanism comprises a push-fit mechanism or a snap-fit ​​mechanism. (3) A cement restrictor inserter instrument as described in embodiment 1 or 2, wherein the stopper includes an attachment forming portion and the releasable attachment mechanism interacts with the attachment forming portion. (4) The cement restrictor inserter instrument of embodiment 3, wherein the attachment forming portion includes a circlip within a portion of the fastener, and the releasable attachment mechanism of the body includes a groove configured to receive the circlip. (5) The cement restrictor inserter instrument of any one of claims 1 to 4, wherein the body defines an open or closed channel extending along a longitudinal axis of the body and configured to receive the shaft.

[0088] (6) The cement restrictor inserter instrument of any one of claims 1 to 5, wherein the releasable attachment mechanism enables rotation of the shaft relative to the body. (7) The cement restrictor inserter instrument of any one of the preceding claims, wherein the cement restrictor attachment formation comprises a push-fit formation. (8) The cement restrictor inserter instrument of any one of the preceding claims, wherein the cement restrictor attachment forming portion comprises a screw thread. (9) A cement restrictor inserter instrument as described in any one of embodiments 1 to 8, wherein the visible depth guide feature comprises a surface or edge of a portion of the body. (10) A cement restrictor inserter instrument as described in any one of embodiments 1 to 8, wherein the visible depth guide feature includes a marking on a surface of a portion of the body.

[0089] (11) The cement restrictor inserter instrument of claim 10, wherein the visible depth guide feature comprises a plurality of markings on the surface of the portion of the body, each of the plurality of markings corresponding to a different position of the orthopedic prosthetic implant relative to the bone of the patient. (12) The cement restrictor inserter instrument of any one of claims 1 to 11, wherein the orthopedic 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 of any one of claims 1 to 12, wherein the body has a size corresponding to the size of the orthopedic prosthetic implant. (14) A kit of surgical instrument parts, comprising: A cement restrictor inserter instrument according to any one of claims 1 to 13, and a further body having a shape corresponding to the shape of the orthopedic prosthetic implant, a further spacer, a further visible depth guide feature, and a further releasable attachment mechanism by which the further body can be releasably attached to the shaft, wherein the further body has a different size than the main body and corresponds to the shape of the different sizes of the orthopedic prosthetic implants, and the further spacer has a different size than the spacer, and the further visible depth guide feature is configured to position the further visible depth guide feature in a different fixed position relative to the inserter when the further spacer abuts the stop that corresponds to the target cement restrictor position when aligned with the feature of the bone of the patient into which the cement restrictor is to be inserted. (15) A method of inserting a cement restrictor into a bone cavity of a patient, comprising: selecting a body having a shape corresponding to a shape of an orthopaedic prosthetic implant to be implanted in a patient's bone cavity, the body including a visible depth guide feature; releasably attaching the body to a shaft of a cement restrictor inserter at a predetermined location; attaching a cement restrictor to a distal end of the shaft of the cement restrictor inserter; and inserting the cement restrictor inserter with the body mounted thereon into the cavity to a depth determined by alignment of the visible depth guide feature with a bone feature of the patient.

[0090] (16) rotating the shaft of the cement restrictor inserter relative to the body to remove the cement restrictor from the distal end of the rod; 16. The method of claim 15, further comprising withdrawing the cement restrictor inserter from the cavity. (17) The method of any one of claims 15 to 16, wherein selecting the body further comprises selecting the body having a size corresponding to the size of the orthopedic implant to be implanted in the cavity of the bone of the patient. (18) The method of embodiment 17, further comprising determining the size of the orthopedic implant to be implanted based on a final trial component, or a final broach, or a final reamer, or a final cutting instrument prior to selecting the body. (19) The method of any of embodiments 15 to 18, further comprising attaching a cement restrictor trial to the distal end of the shaft, and after attaching the body and prior to attaching the cement restrictor, inserting the cement restrictor inserter into the cavity to trial the size of the cement restrictor. (20) A method according to any one of embodiments 15 to 19, wherein the feature of the bone of the patient is an anatomical feature of the bone of the patient.

[0091] (21) The method of any one of embodiments 15 to 19, wherein the feature of the bone of the patient is a resected surface, edge, or periphery of the bone of the patient. (22) The method of any one of embodiments 15 to 21, wherein the visual depth guide is a surface or edge of the body. (23) The method of any one of embodiments 15 to 21, wherein the visual depth guide feature is a single marking on the surface of the body. (24) The method of embodiment 23, wherein the visual depth guide feature comprises a plurality of markings on a surface of the body, each marking corresponding to a different position of the orthopedic prosthetic implant relative to the bone of the patient, and further comprising using the marking corresponding to a selected one of the different positions to determine a depth to which the cement restrictor inserter is to be inserted. (25) The method of any one of claims 15 to 24, wherein the prosthetic orthopedic implant is a femoral stem and the feature of the patient's bone is a neck resection of the femur.

[0092] (26) The method of any one of embodiments 15 to 24, wherein the prosthetic orthopedic implant is a tibial component and the feature of the patient's bone is a proximal resection of the tibia. (27) The method of any one of claims 15 to 24, wherein the prosthetic orthopedic implant is a humeral stem and the feature of the patient's bone is the proximal resection of the humerus.

Claims

1. 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 said proximal end to said distal end, and a stop on said shaft and between said proximal and distal ends; 1. A cement restrictor inserter instrument comprising: a body having a shape corresponding to a shape of an orthopedic 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, 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 that corresponds to a target cement restrictor position when the visible depth guide feature is aligned with a feature of a patient's bone into which the cement restrictor is to be inserted.

2. The cement restrictor inserter instrument of claim 1 , wherein the releasable attachment mechanism comprises a push-fit mechanism or a snap-fit ​​mechanism.

3. The cement restrictor inserter instrument of claim 1 or 2, wherein the stop includes an attachment forming portion, and the releasable attachment mechanism interacts with the attachment forming portion.

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

5. The cement restrictor inserter instrument of any one of claims 1 to 4, wherein the body defines an open or closed channel extending along a longitudinal axis of the body and configured to receive the shaft.

6. The cement restrictor inserter instrument of any preceding claim, wherein the releasable attachment mechanism allows rotation of the shaft relative to the body.

7. The cement restrictor inserter instrument of any preceding claim, wherein the cement restrictor attachment formation comprises a push-fit formation.

8. The cement restrictor inserter instrument of any preceding claim, wherein the cement restrictor attachment formation comprises a screw thread.

9. The cement restrictor inserter instrument of any preceding claim, wherein the visible depth guide feature comprises a surface or edge of a portion of the body.

10. The cement restrictor inserter instrument of any preceding claim, wherein the visible depth guide feature comprises a single marking on a surface of a portion of the body.

11. 11. The cement restrictor inserter instrument of claim 10, wherein the visible depth guide feature comprises a plurality of markings on the surface of the portion of the body, each of the plurality of markings corresponding to a different position of the orthopaedic prosthetic implant relative to the bone of the patient.

12. The cement restrictor inserter tool of any one of claims 1 to 11, 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 of any one of claims 1 to 12, wherein the body has a size corresponding to a size of the orthopaedic prosthetic implant.

14. 1. A kit of surgical instrument parts, comprising: A cement restrictor inserter instrument according to any one of claims 1 to 13; and a further body having a shape corresponding to the shape of the orthopedic prosthetic implant, a further spacer, a further visible depth guide feature, and a further releasable attachment mechanism by which the further body can be releasably attached to the shaft, wherein the further body has a different size than the main body and corresponds to the shape of the different sizes of the orthopedic prosthetic implants, and the further spacer has a different size than the spacer, and the further visible depth guide feature is configured to position the further visible depth guide feature in a different fixed position relative to the inserter when the further spacer abuts the stop that corresponds to the target cement restrictor position when aligned with the feature of the bone of the patient into which the cement restrictor is to be inserted.

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