Patent Application
20230363920
The present invention generally relates to a tibial insert. More specifically, the present invention is directed to a universal tibial insert having an articular surface geometry that remains substantially congruent with a medial condyle of a femoral component when used as part of a right or left total knee replacement system enabled by a universal coupling symmetric across a median and a frontal symmetry plane.
During knee arthroplasty, a femoral component is affixed to the distal end of a patient femur, a tibial baseplate is affixed to the proximal end of a patient tibia, and a tibial insert is positioned between the femoral component and the tibial baseplate. The tibial insert serves as an articular surface about which the femoral component translates when flexing or extending the knee. The tibial insert also helps constrain the femoral component, and specifically with respect to preventing the femoral component from sliding off the tibial baseplate. One goal of a total knee replacement is to mimic the normal kinematics of a healthy knee joint. Generally, during normal flexion of a healthy knee joint, the medial condyle at the distal end of the femur is congruent with one articular surface of the tibial insert, while the motion of the lateral condyle includes translational movement relative to another articular surface of the tibial insert and rotational movement relative to the medial condyle. As such, the surface geometry of the medial and lateral articular surfaces of the tibial insert differ to account for these differences in natural movement. Furthermore, as the anatomy of a patient knee joint differs from person to person, femoral components, tibial baseplates, and tibia inserts may vary in size and shape. Although, manufacturing costs, inventory, and sterilization costs are generally always twofold since two sets of each component are typically needed, namely one set specifically configured for a right total knee replacement and a second set configured for a left total knee replacement.
One example of a prior art medial pivot knee prothesis that provides closer approximation to normal kinematics during knee flexion is shown and described, e.g., in U.S. Pat. No. 6,013,103 to Kaufman, the contents of which are herein incorporated by reference in its entirety. While existing (newer) prior art designs have improved the congruence for the medial condyle and articular surface, the drawback still is that such designs are inefficient from a manufacturing and inventory standpoint because the tibial insert and/or the tibial baseplate are directional, i.e., each manufactured tibial insert and/or tibial baseplate can only be implanted in either the right knee or the left knee; a single conventional tibial insert and/or a single conventional tibial baseplate cannot be implanted in either of the right knee or the left knee. As such, in addition to two femoral components, two tibial inserts and two tibial baseplates still must still be manufactured to accommodate left and right knee arthroplasties. Naturally as a result of these parts not being universally compatible with both the right knee and left knee, the part count is twofold and, as mentioned above, this increases manufacturing complexity and cost, and requires storing upwards of twice as much inventory.
Another undesirable drawback is the potential for an incorrectly sided implant to be used in surgery, which would result in the need for a revision surgery to replace the incorrect implant. This obviously undesirably increases the intrusiveness, time, and cost required to complete the surgery in the event of a mistake.
There exists, therefore, a significant need in the art for a tibial insert universally couplable with a right or a left knee baseplate, such as by way of a base symmetric across an interior and a posterior symmetry plane, and of which includes an articular surface that remains substantially congruent with a medial condyle of a femoral component regardless whether the universal tibial insert is used as part of a right or left total knee replacement system. The present invention fulfills these needs and provides further related advantages.
In one embodiment disclosed herein, a universal tibial insert includes a base selectively engageable with a tibial baseplate and an upwardly presented articular surface having a first side geometry and a second side geometry configured to interface with one of a medial condyle or a lateral condyle of a femoral component in articulatory relation thereof. Here, the articular surface is symmetrical about a median plane such that the universal tibial insert may be oriented relative to the tibial baseplate in one of two configurations 180 degrees relative to the other. Specifically, e.g., the first side geometry is relatively more congruent with the medial condyle and the second side geometry is relatively less congruent with the lateral condyle when the universal tibial insert is in a first orientation for use in one of a right total knee arthroplasty or a left total knee arthroplasty. Conversely, the first side geometry is relatively less congruent with the lateral condyle and the second side geometry is relatively more congruent with the medial condyle when the universal tibial insert is in a second orientation for use in the other of the right total knee arthroplasty or the left total knee arthroplasty.
One feature of this embodiment is that the first side geometry and the second side geometry may be reciprocal, namely that the first side geometry and the second side geometry have approximately the same reciprocal congruence relative to either of the medial condyle or the lateral condyle, depending on the orientation. Specifically, e.g., a radii of the medial condyle of the femoral component relative to a radii of the first side geometry, when the universal tibial insert is in the first orientation, or a radii of the second side geometry, when the universal tibial insert is in the second orientation, may be a medial ratio of about 1:1 to 1:1.2. Moreover, a radii of the lateral condyle of the femoral component relative to a radii of the first side geometry, when the universal tibial insert is in the second orientation, or a radii of the second side geometry, when the universal tibial insert is in the first orientation, may be a lateral ratio of about 1:1.1 to 1:2. In the latter embodiment, the relative congruence may result in an anterior gap and/or a posterior gap between the articular surface and the lateral condyle.
The universal tibial insert as disclosed herein is usable with either of a symmetrical femoral component or an asymmetrical femoral component, and at least a portion of the first side geometry and/or at least a portion of the second side geometry may include a reciprocal concave geometry and/or a reciprocal flat geometry. The universal tibial insert may also include at least one indicator that provides a visual notification or identification regarding whether the universal tibial insert is in the first orientation or the second orientation for purposes of proper orientation during surgery. Here, the indicator may be in the form of an alphanumeric symbol or a color-code. In another aspect of these embodiments, each of the first side geometry and the second side geometry may include a respective anterior peak terminating to a medial side of the universal tibial insert and a posterior peak terminating to a lateral side of the universal tibial insert. Here, the anterior peak may be positioned medial to the median plane, whereby the universal tibial insert may be used in a first orientation that is approximately 180 degrees relative to the second orientation.
In another embodiment as disclosed herein, a universal tibial insert may include a keyed lock plate generally symmetrical across a median plane and a frontal plane and selectively engageable with an asymmetrical tibial base plate in one of two orientations approximately 180 degrees relative to one another. Here, the keyed lock plate may include a downwardly projecting base and a pair of lock bars in spaced apart relation relative thereto, wherein the base and the lock bars cooperate with one another to form a respective pair of notches therebetween having a size and shape for select reception of at least a portion of an upwardly projecting peripheral edge of the tibial baseplate. Opposite the keyed lock plate is an upwardly presented articular surface, which may reciprocally interface with a medial condyle and a lateral condyle of a femoral component in articulatory relation therewith when the universal tibial insert is in the first orientation or in the second orientation when coupled thereto by the keyed lock plate.
In another aspect of these embodiments, one of the pair of lock bars may selectively engage an anterior tibial channel formed by an anterior overhang extending inwardly from the upwardly projecting peripheral edge thereof and the other of the pair of lock bars may selectively reside within a keyed channel of the tibial baseplate when the universal tibial insert is selectively engaged with the tibial baseplate in either of the first orientation or the second orientation. Here, each of the pair of lock bars may be of a width approximately equal to that of the keyed channel, thereby stabilizing side-to-side movement of the universal tibial insert relative to the tibial baseplate when coupled thereto in either of the first orientation or the second orientation. Each of the pair of lock bars may also include a chamfered projection forming a lock bar channel that selectively engages the anterior overhang.
Additionally, the base may also include a reciprocal pair of outwardly projecting ledges forming a pair of grooves therein that selectively engage a pair of inwardly projecting posterior overhangs on opposite sides of the keyed channel of the tibial baseplate for slotted reception therewith. The downwardly projecting base may also be of a size and shape for select reception within an inner cavity of the tibial baseplate formed by the upwardly projecting peripheral edge. Here, the keyed lock plate may include an outwardly projecting flange having a size and shape for seated reception on an upper surface of the peripheral edge of the tibial baseplate while the downwardly projecting base simultaneously seats flush within the inner cavity of the tibial baseplate.
In another alternative embodiment, the universal tibial insert may include a symmetric pair of apertures formed therein and in general alignment with a pair of bores in the tibial baseplate when in the first orientation and in the second orientation. As such, the apertures and the bores may have a size and shape for select slide through reception and tightening engagement of at least one bolt to retain the universal tibial insert to the tibial baseplate. Alternatively, an adhesive selected from the group consisting of a fibrin adhesive, collagen adhesive, polyurethane, epoxy resin, cyanoacrylates, polyesters, and zinc polycarboxylate may help couple, alone or in combination with other features disclosed herein (e.g., the aforementioned snap-fit engagement or bolt), the universal tibial insert to the tibial baseplate.
In another embodiment, the universal tibial insert may include a keyed lock plate generally symmetrical across a median plane and a frontal plane and selectively engageable with an asymmetrical tibial base plate. Here, the keyed lock plate may include a downwardly projecting base and a pair of lock bars in spaced apart relation relative thereto, which cooperate to form a groove in between for select reception and retainment of at least a portion of an upwardly projecting peripheral edge of the tibial baseplate. Moreover, an upwardly presented articular surface having a first side geometry and a second side geometry may be configured so that each interface with one of a medial condyle or a lateral condyle of a femoral component in articulatory relation relative thereto. Here, the first side geometry and the second side geometry may be symmetrical about a median plan and relatively more congruent with the medial condyle than the lateral condyle.
One aspect of these embodiments is that the first side geometry and the second side geometry may be reciprocal of one another. With respect to the congruence, a radii of the medial condyle relative to at least one radii of the first side geometry and at least one radii of the second side geometry may have a medial ratio of about 1:1 to 1:1.2 and a radii of the lateral condyle relative to at least another radii of the first side geometry and at least another radii of the second side geometry may have a lateral ratio of about 1:1.1 to 1:2. The femoral component itself may be a symmetrical femoral component or an asymmetrical femoral component, and an adhesive selected from the group consisting of a fibrin adhesive, collagen adhesive, polyurethane, epoxy resin, cyanoacrylates, polyesters, and zinc polycarboxylate may help secure the universal tibial insert to the tibial baseplate, alone or in combination with other features disclosed herein (e.g., snap-fit engagement of the universal tibial insert with the tibial baseplate). Additionally, the universal tibial insert may include at least one indicator visually identifying whether the universal tibial insert is in one of a pair of orientations relative to the tibial baseplate. Such an indicator may include an alphanumeric symbol or a color-code.
The pair of lock bars may include a width approximately equal to that of a keyed channel of the tibial baseplate and include a chamfered projection selectively engageable underneath an inwardly projecting anterior overhang of the tibial baseplate to help secure the universal tibial insert to the tibial baseplate. Moreover in this respect, the downwardly projecting base may further include a reciprocal pair of ledges that form a pair of slots therein that selectively engage a pair of inwardly projecting posterior overhangs on opposite sides of the keyed channel to facilitate further snap-fit securement thereto.
In another alternative embodiment, the downwardly projecting base may be of a size and shape for select reception within an inner cavity of the tibial baseplate and an outwardly projecting flange of the keyed lock plate may be of a size and shape for seated reception on an upper surface of the peripheral edge while the downwardly projecting base simultaneously seats flush within the inner cavity. The keyed lock plate and the upwardly presented articular surface may also couple to the tibial baseplate in a first position for use in a right total knee arthroplasty or a second position 180 degrees relative to the first position for use in a left total knee arthroplasty.
Other features and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
The accompanying drawings illustrate the invention. In such drawings:
As shown in the exemplary drawings for purposes of illustration, the present invention for a universal tibial insert is generally illustrated in
More specifically as illustrated in
The universal tibial insert 20 may couple to the tibial baseplate 26 by first inserting one set of the pair of ledges 54 or 54′ into a corresponding pair of posterior channels 62 (best illustrated in
Specifically in this respect, each of the lock bars 60, 60′ include an outwardly extending protrusion 72, 72′ with a leading chamfered edge 74, 74′ that contacts an anterior overhang 76 outwardly extending over the recess 52 to form an anterior channel 78 thereunder in a similar manner as the pair of posterior overhangs 64 form the respective posterior channels 62 thereunder. Through continued downward rocking movement, the respective protrusion 72 or 72′ eventually clears the anterior overhang 76 such that the respective chamfered edge 74 or 74′ is no longer in engagement therewith, whereby the respective protrusion 72 or 72′ is able to slide down underneath the anterior overhang 76 within the anterior channel 78 in snap-fit engagement therewith.
When in this position, one set of the pair of the ledges 54 or 54′ now reside within the posterior channels 62 underneath the posterior overhangs 64, the lock bar 60 or 60′ formed on the same side as the pair of ledges 54 or 54′ within the posterior channels 62 resides within the keyed channel 68, and the other of the lock bars 60 or 60′ is engaged on the anterior side 70 by way of its protrusion 72 or 72′ extending into the anterior channel 78 under the anterior overhang 76. Here, the universal tibial insert 20 is effectively in snap-fit engagement with the tibial baseplate 26. Of course, because the base 28 of the universal tibial insert 20 is symmetrical, the universal tibial insert 20 is engageable with the tibial baseplate 26 in one of two orientations that are 180° opposite each other, depending whether the universal tibial insert 20 is to be used in the right total knee replacement system 34 or the right total knee replacement system 36.
As illustrated in
Alternatively, the universal tibial insert 20 may couple to the tibial baseplate 26 by first inserting the protrusion 72 or 72′ outwardly extending from the corresponding lock bar 60 or 60′ at an angle into the anterior channel 78. At the same time, the anterior overhang 76 may at least partially extend into the lock bar channel 80 as well. The universal tibial insert 20 is then pressed downwardly into rocking engagement with the tibial baseplate 26 whereby one pair of the corresponding ledges 54 or 54′ engage with the posterior channels 62 underneath the posterior overhangs 64. The lock bar 60 or 60′ not otherwise engaged with the anterior side 70 of the tibial baseplate 26 then slides within the space formed by the keyed channel 68. The lock plate 46 may include a chamfered edge 84 around its periphery, including along each of the ledges 54, 54′, to facilitate insertion of the ledges 54 or 54′ past the posterior overhangs 64. Once therein, the posterior overhangs 64 may extend into the grooves 56 or 56′ above the corresponding ledges 54 or 54′ for snap-fit coupling thereto.
Another method for coupling the universal tibial insert 20 to the tibial baseplate 26 may include initially aligning one of the lock bars 60 or 60′ of the universal tibial insert 20 within the keyed channel 68. Then, the universal tibial insert 20 is pressed downwardly so the lock bar 60 or 60′ descends into the keyed channel 68 wherein the chamfered edge 74 of the protrusion 72 contacts the anterior overhang 76 at the same time the chamfered edges 84 along the ledges 54 or 54′ contact the posterior overhangs 64. Applying a continued downward force causes the chamfered edges 74 and 84 to somewhat deflect the posterior protrusion 72 and the ledges 54 or 54′ into the respective anterior channel 78 and the pair of posterior channels 62 for snap-fit engagement therewith, while the other lock bar 60 or 60′ is able to fully descend into the keyed channel 68. The universal tibial insert 20 is then engaged with the tibial baseplate 26 as shown and described above with respect to, e.g.,
In addition to snap-fit engagement, the universal tibial insert 28 may further attach to the tibial baseplate 26 by adhesives or mechanical engagement, such as by way of a threaded screw or bolt, locking cross pin or metal clip. In one embodiment, the adhesive may be applied to the base surface 48 and/or the recessed outer periphery 82 of the universal tibial insert 20, or the adhesive may be applied to the inner surface 50 and/or the peripheral edge 66 of the tibial baseplate 26. The adhesive then serves to further retain the universal tibial insert 20 to the tibial baseplate 26 as it cures therebetween. In other embodiments, the adhesive may be used alone to exclusively retain the universal tibial insert 20 to the tibial baseplate 26. In one embodiment, the adhesive may be a bone cement (e.g., polymethylmethacrylate (PMMA) or the like) known in the art. Alternatively, the adhesive may include a fibrin adhesive, collagen adhesive, polyurethane, epoxy resin, cyanoacrylates, polyesters, or zinc polycarboxylate.
In an alternative embodiment, the universal tibial insert 20 may couple to the tibial baseplate 26 via a bolt that extends through, e.g., one of the corresponding apertures 86 or 86′ formed within the universal tibial insert 20 (
As illustrated in
More specifically as illustrated in
Further to constraining movement of the medial condyle 40 relative to the medial articular surface 38 and permitting relative enhanced movement of the lateral condyle 44 relative to the lateral articular surface 42, the universal tibial insert 20 includes a pair of peaks 102, 102′ culminating between a gradual slope 104, 104′ on one side and a relatively steep slope 106, 106′ on an opposite side thereof. As shown best in
Moreover, the universal tibial insert 20 may further include an upwardly slopped and centrally located post 108 that may assist in aligning the femoral component 24 with the universal tibial insert 20. For example, the post 108 may assist in providing medial-to-lateral stability for the femoral component 24 and, as a secondary consideration, the centrally located post 108 may further assist in rolling back the femoral component 24 to a generally parallel position with the universal tibial insert 20 during flexion.
Lastly, the medial articular surface 38 and/or the lateral articular surface 42 may include an indicator that may assist the surgeon in coupling the universal tibial insert 20 to the tibial baseplate 26 in the correct orientation. For example, the medial articular surface 38 and/or lateral articular surface 42 may include an alphanumeric symbol such as a “M” on the medial articular surface 38 to designate the same and/or a “L” on the lateral articular surface 42 to designate the same. Of course, the indicator may include any symbol, alphanumeric or otherwise, to assist in differentiating the medial articular surface 38 from the lateral articular surface 42. Alternatively, the indicator may be color-coded to differentiate the medial articular surface 38 from the lateral articular surface 42. For example, in one embodiment, the medial articular surface 38 may be blue and the lateral articular surface 42 may be green. Moreover, the universal tibial insert 20 may be made of high-density plastic such as polyethylene or the like.
Although several embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.
| Number | Date | Country | |
|---|---|---|---|
| 63342536 | May 2022 | US |
