Orthopedic implant system with bone preservation function

Abstract

The tibial insert includes an articular surface and a bottom surface opposite the articular surface. The bottom surface includes one or more bone-conserving features. In some embodiments, the bottom surface may be curved to match the curvature of the articular surface so that the thickness of the tibial insert is relatively constant. In other embodiments, the bottom surface may be relatively flat but include protrusions extending from the flat base surface to maintain a minimum thickness of the tibial insert. The described features may be incorporated into unicompartmental tibial prostheses, bicompartmental prostheses, or total knee prostheses.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This patent application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 842,178, entitled "ORTHOPAEDIC IMPLANT SYSTEM WITH BONE CONSERVING FEATURES," filed May 2, 2019, which is expressly incorporated by reference in its entirety into this application.

[0002] FIELD OF THEINVENTION The present invention relates to orthopaedic surgical systems, and more particularly, to orthopaedic surgical systems for performing knee replacement surgery. [Background technology]

[0003] Arthroplasty is a well-known surgical procedure that replaces a diseased and / or damaged natural joint with an artificial joint. A typical knee prosthesis includes a tibial tray, a femoral component, and a polymer insert or bearing positioned between the tibial tray and the femoral component. Depending on the severity of the damage to the patient's joint, various mobile orthopedic prostheses can be used. For example, a knee prosthesis may include a "fixed" tibial insert when it is desirable to limit the motion of the knee prosthesis, such as when significant soft tissue damage or loss is present. Alternatively, a knee prosthesis may include a "mobile" tibial insert when a greater degree of freedom of movement is desired.

[0004] The type of orthopedic knee prosthesis used to replace the patient's natural knee joint may also depend on whether the patient's posterior cruciate ligament is preserved or sacrificed (i.e., removed) during surgery. For example, if the patient's posterior cruciate ligament is damaged, lesioned, and / or otherwise removed during surgery, a posterior stabilized knee prosthesis may be used to provide additional support and / or control in posterior degrees of flexion. Alternatively, if the posterior cruciate ligament is intact, a cruciate ligament-retaining knee prosthesis may be used.

[0005] In addition, the orthopedic knee prosthesis may be a total knee prosthesis designed to replace the femoral-tibial interface of both condyles of the patient's femur, or a unicompartmental knee prosthesis designed to replace the femoral-tibial interface of a single condyle of the patient's femur, depending on the condition of the patient's knee joint. Total knee replacement or arthroplasty may include replacement of the femur, the proximal femur, the distal femur, and / or the entire femur, and the midshaft portion of the proximal tibia. Unicompartmental knee replacement or arthroplasty includes unicompartmental articular surface replacement. Unicompartmental knee arthroplasty provides an alternative to total knee replacement for rehabilitating the knee when only one condyle is damaged as a result of trauma or disease, such as non-inflammatory degenerative joint disease or its combined diagnosis of osteoarthritis or post-traumatic arthritis. In some cases, an orthopedic knee prosthesis may be a bicompartmental knee prosthesis formed by two unicompartmental knee prostheses replacing each of the patient's medial and lateral tibial condyles. In such cases, a single complete femoral component or two partial femoral components may be used in cooperation with two unicompartmental inserts. Summary of the Invention [Means for solving the problem]

[0006] According to one aspect of the disclosure, a unicompartmental tibial insert includes an anterior end, a posterior end, an articular surface extending from the anterior end to the posterior end, and a bottom surface extending from the anterior end to the posterior end opposite the articular surface. The articular surface is configured to articulate with a corresponding condyle of a natural or prosthetic femur. The bottom surface is configured to mate with a unicompartmental tibial tray and is non-planar.

[0007] In some embodiments, the articular surface has a concave shape when viewed in the sagittal plane and the bottom surface has a convex shape when viewed in the sagittal plane. Additionally or alternatively, the articular surface may have a concave shape when viewed in the coronal plane and the bottom surface may have a convex shape when viewed in the coronal plane.

[0008] The vertical distance between the articular surface and the bottom surface can define a thickness of the tibial insert. In some embodiments, the thickness of the tibial insert is constant between the anterior and posterior ends. For example, the thickness of the tibial insert is about 6 millimeters. Additionally, in some embodiments, the curvature of the articular surface matches the curvature of the bottom surface.

[0009] According to another aspect of the present disclosure, a unicompartmental tibial insert includes an anterior end, a posterior end, an articular surface extending from the anterior end to the posterior end, and a bottom surface extending from the anterior end to the posterior end opposite the articular surface. The articular surface is configured to articulate with a corresponding condyle of a natural or prosthetic femur. The bottom surface is configured to mate with the unicompartmental tibial tray and is non-planar. A vertical distance between the articular surface and the bottom surface can define a thickness of the tibial insert that is constant between the anterior end and the posterior end.

[0010] According to a further aspect of the present disclosure, the unicompartmental tibial insert may include an anterior end, a posterior end, an articular surface extending from the anterior end to the posterior end, and a bottom surface extending from the anterior end to the posterior end opposite the articular surface. The articular surface is configured to articulate with a corresponding condyle of a natural or prosthetic femur. The bottom surface is configured to mate with the unicompartmental tibial tray and includes a flat base surface and a projection extending from the flat base surface. The projection has a curved outer surface.

[0011] In some embodiments, the articular surface may have a concave shape when viewed in the sagittal plane and the bottom projection may have a convex shape when viewed in the sagittal plane. Additionally or alternatively, the articular surface may have a concave shape when viewed in the coronal plane and the bottom projection may have a convex shape when viewed in the coronal plane.

[0012] The vertical distance between the articular surface and the bottom surface can define a thickness of the tibial insert. In such an embodiment, the thickness of the tibial insert can be constant between the anterior end and the posterior end. For example, the thickness of the tibial insert is about 6 millimeters.

[0013] In some embodiments, a first perpendicular distance between the articular surface and the flat base surface of the bottom defines a first thickness, and a second perpendicular distance between the articular surface and the curved outer surface of the protrusion defines a second perpendicular distance. The second perpendicular distance may be equal to the first perpendicular distance.

[0014] Further, in some embodiments, the perpendicular distance between the articular surface and the curved outer surface of the bottom projection can define a thickness of the projection. In some embodiments, the thickness of the projection can be constant. For example, the thickness of the projection can be about 6 millimeters. Further, in some embodiments, the bottom projection can be semi-elliptical in shape. Further, in some embodiments, the bottom projection is offset from the medial-lateral axis of the tibial insert toward the posterior end of the tibial insert.

[0015] According to yet another aspect of the present disclosure, the tibial knee prosthesis may include an anterior, a posterior, a medial articular surface extending from anterior to posterior, a lateral articular surface extending from anterior to posterior, and a bottom surface extending from anterior to posterior opposite the medial and lateral articular surfaces. The medial articular surface may be configured to articulate with a medial condyle of a natural or artificial femur. Similarly, the lateral articular surface may be configured to articulate with a lateral condyle of a natural or artificial femur. The bottom surface includes a flat base surface and a projection extending from the flat base surface below the medial or lateral articular surface. The projection may have a curved outer surface.

[0016] In some embodiments, the tibial insert can further include a peg extending from the bottom projection. Additionally, in some embodiments, each of the medial and lateral articular surfaces can have a concave shape when viewed in the sagittal plane. In such embodiments, the bottom projection can have a convex shape when viewed in the sagittal plane.

[0017] In some embodiments, the perpendicular distance between the medial articular surface and the curved outer surface of the prong, or between the lateral articular surface and the curved outer surface of the prong, defines a thickness of the prong, in such embodiments, the thickness of the prong is constant and may be about 6 millimeters.

[0018] In some embodiments, the tibial insert is embodied as a monoblock prosthesis and can include a polymer bearing attached to a metal platform, in such embodiments, the polymer bearing includes a medial articular surface and a lateral articular surface, and the metal platform includes a bottom surface having a flat base surface and a projection extending from the flat base surface below the medial articular surface or the lateral articular surface. [Brief description of the drawings]

[0019] The detailed description makes specific reference to the following drawings: [Figure 1] FIG. 1 is an exploded perspective view of one embodiment of an exemplary orthopaedic knee prosthesis system for implantation into a patient's tibia. [Diagram 2] FIG. 2 is a perspective view of the tibia of FIG. 1 after total knee prosthesis removal. [Diagram 3] FIG. 3 is a perspective view of the tibia of FIG. 2 after unicompartmental knee prosthesis resection. [Figure 4] 2 is a medial-lateral cross-sectional view of an exemplary tibial insert that may form a component of the exemplary orthopaedic knee prosthesis system of FIG. 1. [Diagram 5] FIG. 1 illustrates a top perspective view of one embodiment of a unicompartmental tibial insert having bone conserving features. [Figure 6] FIG. 6 is a top plan view of the unicompartmental tibial insert of FIG. 5. [Figure 7] FIG. 6 is an inferior plan view of the unicompartmental tibial insert of FIG. 5. [Figure 8] FIG. 6 is an internal view of the unicompartmental tibial insert of FIG. 5 . [Figure 9] FIG. 6 is a rear view of the unicompartmental tibial insert of FIG. 5 . [Figure 10] FIG. 6 is an anterior-posterior cross-sectional view of the unicompartmental tibial insert of FIG. 5 . [Figure 11] FIG. 5 is an anterior-posterior cross-sectional view of an exemplary tibial insert similar to FIG. 4. [Figure 12] FIG. 6 is a medial-lateral cross-sectional view of the unicompartmental tibial insert of FIG. 5 . [Figure 13] 12 is a medial-lateral cross-sectional view of the exemplary tribal insert of FIG. 11. FIG. [Figure 14] FIG. 6 is a perspective view of a patient's tibia after removal of the unicompartmental tibial insert in preparation for implantation of the unicompartmental tibial insert of FIG. 5. [Figure 15] 15 is a cross-sectional evaluation of the tibia of the patient of FIG. 14 after implantation of a unicompartmental knee prosthesis including the unicompartmental tibial insert of FIG. 5. [Figure 16] FIG. 13 is a bottom perspective view of another embodiment of a unicompartmental tibial insert having bone preserving features. [Figure 17] FIG. 17 is a top plan view of the unicompartmental tibial insert of FIG. 16. [Figure 18] FIG. 17 is an inferior plan view of the unicompartmental tibial insert of FIG. 16 . [Figure 19] FIG. 17 is an internal view of the unicompartmental tibial insert of FIG. 16 . [Figure 20] FIG. 17 is a rear view of the unicompartmental tibial insert of FIG. 16 . [Figure 21] FIG. 17 is an anterior-posterior cross-sectional view of the unicompartmental tibial insert of FIG. 16 . [Figure 22] FIG. 11 is an anterior-posterior cross-sectional view of an exemplary tibial insert similar to FIG. 10. [Diagram 23] 17 is a medial-lateral cross-sectional view of the unicompartmental tibial insert of FIG. 16 . [Figure 24] FIG. 23 is a medial-lateral cross-sectional view of the exemplary tribal insert of FIG. 22. [Diagram 25] FIG. 1 is a lower perspective view of a tibial total knee prosthesis having bone preserving features. [Figure 26] FIG. 26 is an inferior plan view of the tibial total knee prosthesis of FIG. 25. [Figure 27] FIG. 26 is a top plan view of the tibial total knee prosthesis of FIG. 25. [Figure 28]FIG. 26 is a posterior view of the tibial total knee prosthesis of FIG. 25. [Figure 29] FIG. 26 is an anterior view of the tibial total knee prosthesis of FIG. 25. [Diagram 30] FIG. 26 is a side view of the tibial total knee prosthesis of FIG. 25. [Diagram 31] 26 is another side view of the tibial total knee prosthesis of FIG. 25. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific illustrative embodiments thereof have been shown by way of example in the drawings and are herein described in detail, It should be understood, however, that there is no intention to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0021] Terms denoting anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etc., may be used throughout this specification with reference to the orthopedic implants and surgical instruments described herein, as well as the patient's natural anatomy. Such terms have well-understood meanings both in the study of anatomy and in the field of orthopedic surgery. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings, unless otherwise specified.

[0022] 1, an exemplary orthopaedic total knee prosthesis system 100 includes an exemplary "mobile" or "rotating" orthopaedic knee prosthesis 102 and an exemplary "fixed" orthopaedic knee prosthesis 104. Each of the orthopaedic knee prosthesis 102 and the orthopaedic knee prosthesis 104 is configured to be secured to a surgically-prepared proximal end of a patient's tibia 106, as described in more detail below.

[0023] The exemplary "mobile" orthopaedic knee prosthesis 102 includes a tibial insert 110 and a tibial tray 112. The tibial insert 110 is typically formed from a polymeric material, such as ultra-high molecular weight polyethylene (UHMWPE), while the tibial tray 112 is formed from a metallic material, such as cobalt chrome or titanium.

[0024] The tibial insert 110 is configured to be coupled with the tibial tray 112 and includes a platform 120 having an upper bearing surface 122 and a bottom surface 124. To facilitate coupling between the tibial insert 110 and the tibial tray 112, the tibial insert 110 also includes a stem 126 extending downwardly from the bottom surface 124 of the platform 120. The stem 126 is configured to be received within a bore 138 of the tibial tray 112. During use, the tibial insert 110 is configured to rotate relative to the tibial tray 112 about an axis defined by the stem 126.

[0025] As described below in connection with FIG. 2, the tibial tray 112 is configured to be secured to the surgically-prepared proximal end of the patient's tibia 106. The tibial tray 112 may be secured to the patient's tibia using bone adhesive or other attachment means. The tibial tray 112 includes a platform 130 having an upper surface 132 and a bottom surface 134. The tibial tray 112 also includes a stem 136 extending downwardly from the bottom surface 134 of the platform 130. A bore 138 is defined in the upper surface 132 of the platform 130 and extends downwardly into the stem 126.

[0026] The exemplary "fixed" orthopaedic knee prosthesis 104 includes a tibial insert or bearing 140 attached to a tibial platform or base 142. The tibial insert 140 is typically formed from a polymeric material such as ultra-high molecular weight polyethylene (UHMWPE), while the tibial platform 142 is formed from a metallic material such as cobalt chrome or titanium. The orthopaedic knee prosthesis 104 may also include one or more pegs or keels 150 extending downwardly from a bottom surface 152 of the tibial platform 142 to facilitate fixation to the patient's tibia 106.

[0027] The tibial insert 140 and the tibial platform 142 may be of a modular design (e.g., the tibial insert 140 and the tibial platform 142 may be separate components) or may be of a one-piece design. For example, in some embodiments, the tibial insert 140 may be permanently attached (e.g., molded) to the tibial platform 142. Nevertheless, similar to the tibial tray 112, the tibial platform 142 is configured to be secured to the surgically-prepared proximal end of the patient's tibia 106.

[0028] As discussed above, in a total knee arthroplasty (TKA), either the orthopaedic knee prosthesis 102 or the orthopaedic knee prosthesis 104 may be used to replace the proximal end of the patient's tibia 106. To do so, the patient's tibia 106 is resected by making a planar cut across the tibial plateau to provide a flat resection surface 200 at the proximal end of the patient's tibia 106, as shown in FIG. 2. The flat resection surface 200 provides a base for supporting either the bottom surface 134 of the platform 130 of the tibial tray 112 or the bottom surface 152 of the tibial platform 142, depending on whether the orthopaedic knee prosthesis 102, 104 is used. In either case, the tibial insert 110, 140 provides an artificial tibial articular surface against which the patient's natural or artificial femur can articulate. Of course, additional surgical procedures (eg, drilling of the tibia 106) may be required to fully implant the orthopaedic knee prosthesis 102, 104.

[0029] In some cases, total knee replacement may not be necessary because only one condyle of the patient's tibia and / or femur may be diseased or damaged. In such cases, an orthopedic unicompartmental knee prosthesis may be used to replace the natural condyles of the patient's tibia 106 and / or femur. A typical unicompartmental knee prosthesis is similar to one half of a total knee prosthesis, but is configured to replace a single condyle or articular surface. Thus, a typical unicompartmental tibial prosthesis includes a tibial insert having a single articular surface and a tibial tray configured to be fixed to the patient's tibia 106. A unicompartmental knee arthroplasty (UKA) surgical procedure may be used to implant a typical unicompartmental tibial prosthesis. To do so, one of the articular surfaces of the patient's tibia 106 is resected by making a planar cut across the tibial plateau to provide a flat resection surface 300 on the medial or lateral side at the proximal end of the patient's tibia 106, as shown in FIG. 3. 2, the planar resection surface 300 provides a base for supporting the bottom surface of the platform of a typical unicompartmental tibial prosthesis. Of course, when a bicompartmental knee prosthesis is used, both the medial and lateral sides of the proximal end of the patient's tibia 106 may be resected.

[0030] One standard that is commonly recommended and adhered to in orthopedic tibial prostheses is the minimum distance between the articular surface of the tibial insert and the upper surface of the tibial tray. As mentioned above, the tibial insert is generally formed from a polymeric material, while the tibial tray is metal. Thus, the minimum thickness of the polymeric tibial insert should be maintained so that the tibial insert does not break or wear excessively during use. For example, as shown in FIG. 4, the minimum distance 400 between the articular surface of the tibial insert 140 and the upper surface of the tibial platform 142 (i.e., the thickness of the tibial insert) may be adhered to at 6 to 8 millimeters. However, maintaining the minimum tibial insert thickness, especially at the dwell point of the articular surface of the tibial insert, may require the removal of excess bone from the patient's tibia. That is, due to the curved articular surface of a typical tibial insert, the patient's tibia 106 must be resected a distance equal to the minimum distance beyond the dwell point of the articular surface (e.g., 6-8 millimeters), which can result in excessive bone resection in areas anterior to and posterior to the dwell point of the articular surface where the articular surface is not as deep as the dwell point.

[0031] Furthermore, in some circumstances, resecting the patient's tibia 106 in a planar manner can result in a "see-saw" loading effect of the tibial knee prosthesis, where compressive loading on one side of the tibial knee prosthesis can lift the opposite side. Additionally, flexion and extension of the knee prosthesis can transmit shear forces across the articular surface of the orthopaedic prosthesis of the knee prosthesis. Because a planar surface provides reduced resistance to shear forces, the orthopaedic tibial prosthesis may require pegs or keels to resist such shear forces, which may require additional bone removal.

[0032] 5-9, the exemplary unicompartmental tibial insert 500 includes bone-sparing features to reduce the amount of bone removed during implantation of the tibial insert 500 into a patient's tibia. The unicompartmental tibial insert 500 is generally "D-shaped" when viewed in plan view as shown in FIGS. 6 and 7 and includes an articular surface 502 and a bottom surface 504 opposite the articular surface 502. The articular surface 502, which extends from an anterior end 506 to a posterior end 508 of the tibial insert 500, is curved and configured to articulate with a corresponding natural or artificial condyle of the patient's femur. Additionally, unlike typical unicompartmental tibial inserts, the bottom surface 504 is also curved and extends from the anterior end 506 to the posterior end 508 of the tibial insert 500.

[0033] Illustratively, the articular surface 502 has a concave curvature and the bottom surface 504 has a convex curvature such that the bottom surface 504 mirrors the curvature of the articular surface 502. For example, as shown in Figure 8, the articular surface 502 is concave in the anterior-posterior direction when viewed in the sagittal plane, and the bottom surface 504 is convex in the anterior-posterior direction when viewed in the sagittal plane. Similarly, as shown in Figure 9, the articular surface 502 is concave in the medial-lateral direction when viewed in the coronal plane, and the bottom surface 504 is convex in the medial-lateral direction when viewed in the coronal plane.

[0034] 10-13, in some embodiments, the curvature of the bottom surface 504 matches the curvature of the articular surface 502 such that the thickness of the unicompartmental tibial insert 500 is constant within manufacturing tolerances. For example, in an exemplary embodiment, the vertical distance 1000 defined between the articular surface 502 and the bottom surface 504 defines the thickness of the unicompartmental tibial insert 500, which is constant in the anterior-posterior direction as shown in FIG. 10 and in the medial-lateral direction as shown in FIG. 12.

[0035] 10 and 12, the perpendicular distance 1000 is defined by the length of an imaginary line (distance 1000) that is perpendicular to an imaginary tangent line 503 that is tangent to the articular surface 502 and perpendicular to an imaginary tangent line 505 that is tangent to the bottom surface 504. For example, the perpendicular distance 1000 can be measured as the distance between the tangent line 503's tangent to the articular surface 502 and the tangent line 505's tangent to the bottom surface 504.

[0036] Conversely, as shown in Figures 11 and 12, the typical unicompartmental tibial insert 1100 has a flat bottom surface 1102, which causes the thickness of the typical unicompartmental tibial insert 1100 to vary in both the anterior-posterior direction as shown in Figure 11 and the medial-lateral direction as shown in Figure 13. Thus, the typical unicompartmental tibial insert 1100 requires the removal of additional bone from the patient's tibia in the peripheral anterior, posterior, medial and lateral regions (i.e., regions away from the dwell point).

[0037] 14 and 15, it should be appreciated that the unicompartmental tibial insert 500 may include or be configured to mate with a unicompartmental tibial tray 1500 to form a unicompartmental tibial prosthesis 1550. In some embodiments, the unicompartmental tibial tray 1500 may include a tibial platform 1502 having a curved upper surface 1504 configured to mate with the unicompartmental tibial insert 500 and a bottom surface 1506 that is curved similarly to or otherwise curved to match the curvature of the bottom surface 504 of the unicompartmental tibial insert 500 to reduce the amount of bone removed during implantation. Thus, as shown in FIG. 14, the unicompartmental tibial prosthesis 1550 may be embedded within a circular or semi-elliptical recess 1402 drilled or otherwise formed in the proximal end of the patient's tibia 1400 without the need to cut the patient's tibia 1400 planarly as shown. Because of the curved bottom surfaces 504, 1506, the recess 1402 can be formed to have a minimum depth necessary to ensure a minimum distance between the articular surface 502 of the unicompartmental tibial insert 500 and the top surface 1504 of the tibial tray 1500. In this manner, bone of the patient's tibia 1400 is preserved compared to resecting the patient's tibia in a planar manner. Furthermore, it should be appreciated that the elliptical shape of the recess 1402 can improve resistance to shear forces, thereby reducing or eliminating the need for pegs or keels on the tibial tray 1500 and further preserving bone of the patient's tibia 1400.

[0038] 16-20, another exemplary unicompartmental tibial insert 1600 includes bone-sparing features to reduce the amount of bone removed during implantation of the tibial insert 1600 into a patient's tibia. The unicompartmental tibial insert 1600 is similar to the unicompartmental tibial insert 500 described above and is generally "D-shaped" when viewed in plan view as shown in FIGS. 17 and 18. The unicompartmental tibial insert 1600 includes an articular surface 1602 and a bottom surface 1604 opposite the articular surface 1602. Similar to the unicompartmental tibial insert 500, the articular surface 1602, which extends from an anterior end 1606 to a posterior end 1608 of the tibial insert 1600, is curved and configured to articulate with a corresponding natural or artificial condyle of the patient's femur. However, the bottom surface 1604 of the unicompartmental tibial insert 1600 has a flat base surface 1610 and a protrusion 1620 that extends away (eg, downwardly) from the flat base surface 1610.

[0039] The prongs 1620 have a curved outer surface with a convex curvature that mirrors the concave curvature of the articular surface 1602 in the region of the prongs 1620. For example, as shown in FIG 19, when viewed in the sagittal plane, the articular surface 1602 is concave in the anterior-posterior direction, and when viewed in the sagittal plane, the curved outer surface of the prongs 1620 is convex in the anterior-posterior direction. Similarly, as shown in FIG 20, the articular surface 1602 is concave in the medial-lateral direction when viewed in the coronal plane, and the curved outer surface of the prongs 1620 is convex in the medial-lateral direction when viewed in the coronal plane.

[0040] The projection 1620 is illustratively semi-elliptical, but may have a different shape in other embodiments. The projection 1620 is positioned on the flat base surface 1610 such that it is aligned with a dwell point of the articular surface 1602 such that the thickness of the unicompartmental tibial insert 1600 meets a minimum thickness (e.g., 6-8 millimeters). For example, as shown in FIG. 18, the dwell point of the articular surface 1602 is positioned toward the posterior end 1608 of the unicompartmental tibial insert 1600, and thus the projection 1620 is offset toward the posterior end 1608 relative to the medial-lateral axis 1630 of the unicompartmental tibial insert 1600 as well.

[0041] 21-24, in some embodiments, the curvature of the curved outer surface of the projection 1620 matches the curvature of the articular surface 1602 such that the thickness of the unicompartmental tibial insert 1600 in the region of the projection 1620 is constant within manufacturing tolerances. For example, in an exemplary embodiment, the vertical distance 2100 between the articular surface 1602 and the curved outer surface of the projection 1620 defines a thickness of the projection 1620 that is constant in the anterior-posterior direction as shown in FIG. 21 and in the medial-lateral direction as shown in FIG.

[0042] 21 and 23, the perpendicular distance 2100 is defined by the length of an imaginary line (distance 2100) that is perpendicular to an imaginary tangent 1603 that is tangent to the articular surface 1602 and perpendicular to an imaginary tangent 1605 that is tangent to the curved outer surface of the prong 1620. For example, the perpendicular distance 2100 can be measured as the distance between the tangent point 1603 of the articular surface 1602 and the tangent point 1604 of the curved outer surface of the prong 1620.

[0043] Conversely, as shown in Figures 22 and 24, the typical unicompartmental tibial insert 1100 has a flat bottom surface 1102, which causes the thickness of the typical unicompartmental tibial insert 1100 to vary in both the anterior-posterior direction, as shown in Figure 22, and the medial-lateral direction, as shown in Figure 24.

[0044] Illustratively, the overall thickness of the unicompartmental tibial insert 1600 varies between the projections 1620 and the flat base surface 1610. For example, as shown in FIG. 21 , a vertical distance 2102 between the articular surface 1602 and the flat base surface 1610 defines a thickness of the unicompartmental tibial insert 1600 that differs from the thickness of the projections 1620 described above. However, in some embodiments, the overall thickness of the unicompartmental tibial insert 1600 may not differ from or may be equal to the thickness of the projections 1620 (i.e., the vertical distance 2100).

[0045] The tibial insert 500, 1600 has been shown and described as a unicompartmental tibial insert for replacing a single condyle of a patient's tibia. However, it should be understood that in some embodiments, a medial and a lateral unicompartmental tibial insert 500, 1600 may be used to form a bicompartmental tibial insert for replacing both condyles of a patient's tibia.

[0046] 25-31, an exemplary tibial knee prosthesis 2500 includes bone sparing features to reduce the amount of bone removed during implantation of the tibial knee prosthesis 2500 into a patient's tibia. The tibial knee prosthesis 2500 is embodied as a total knee prosthesis configured to replace the proximal end of the patient's tibia. As such, the tibial knee prosthesis 2500 includes a medial articular surface 2502, a lateral articular surface 2522, and a bottom surface 2504 opposite the medial articular surface 2502 and the lateral articular surface 2522. The medial articular surface 2502, which extends from an anterior end 2506 to a posterior end 2508 of the tibial knee prosthesis 2500, is curved and configured to articulate with a corresponding natural or artificial medial condyle of the patient's femur. Similarly, the lateral articular surface 2522, which extends from the anterior end 2506 to the posterior end 2508 of the tibial knee prosthesis 2500, is curved and configured to articulate with a corresponding natural or artificial lateral condyle of the patient's femur. However, the bottom surface 2504 has a flat base surface 2510 and a pair of projections 2550, 2552 that extend away from the flat base surface 2510 (e.g., downwardly).

[0047] Each of the projections 2550, 2552 of the tibial knee prosthesis 2500 may be substantially similar to the projection 1620 described above. For example, each projection 2550, 2552 has a curved outer surface with a convex curvature that mirrors the concave curvature of the corresponding medial articular surface 2502 or lateral articular surface 2522 in the region of the corresponding projection 2550, 2552. For example, as best shown in Figures 28 and 29, the medial articular surface 2502 is concave in the anterior-posterior direction when viewed in the sagittal plane, and the curved outer surface of the projection 2550 is convex in the anterior-posterior direction when viewed in the sagittal plane. Similarly, the lateral articular surface 2522 is concave in the anterior-posterior direction when viewed in the sagittal plane, and the curved outer surface of the projection 2552 is convex in the anterior-posterior direction when viewed in the sagittal plane. 30 and 31, the medial articular surface 2502 is concave in the medial-lateral direction when viewed in a coronal plane, and the curved outer surface of the projection 2550 is convex in the medial-lateral direction when viewed in a coronal plane. Similarly, the lateral articular surface 2522 is concave in the medial-lateral direction when viewed in a coronal plane, and the curved outer surface of the projection 2552 is convex in the medial-lateral direction when viewed in a coronal plane.

[0048] Each of the projections 2550, 2552 is illustratively semi-elliptical, but may have different shapes in other embodiments. Additionally, while the tibial knee prosthesis 2500 includes two projections 2550, 2552 in the illustrative embodiment, the tibial knee prosthesis 2500 may include additional or fewer projections 2550, 2552 in other embodiments. Each of the projections 2550, 2552 is aligned with a dwell point of the corresponding medial articular surface 2502 / lateral articular surface 2522 such that the thickness of each projection 2550, 2552 (i.e., the vertical distance between the outer surface of each projection 2550, 2552 and the corresponding medial articular surface 2502 / lateral articular surface 2522) meets a minimum thickness (e.g., 6-8 millimeters). As discussed above, the dwell points of the articular surfaces 2502, 2522 are located toward the posterior end 2508, and therefore each prong 2550, 2552 is similarly offset toward the posterior end 2508. Further, in the illustrative embodiment, each prong 2550, 2552 includes a peg 2560, 2562 extending from the curved outer surface of the corresponding prong 2550, 2552, respectively.

[0049] It is understood that the tibial knee prosthesis 2500 may be of modular or one-piece design. For example, in some embodiments, the tibial knee prosthesis 2500 includes a tibial insert including articular surfaces 2502, 2522 and a tibial tray. In such embodiments, the tibial insert may be removably attached to the tibial tray to form the tibial knee prosthesis 2500. In other embodiments, the tibial insert of the tibial knee prosthesis 2500 is attached (e.g., molded) to the tibial tray of the tibial knee prosthesis 2500. For example, the tibial tray may have a porous coating or outer surface to facilitate attachment of the tibial insert. Such designs are commonly referred to as "monolithic" tibial prostheses.

[0050] While the present disclosure has been illustrated and described in detail in the drawings and foregoing description, it is understood that such illustration and description is merely illustrative in nature and should not be regarded as restrictive, and that merely illustrative embodiments have been shown and described, and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.

[0051] The present disclosure has multiple advantages based on various features of the methods, devices, and systems described herein. It is noted that alternative embodiments of the methods, devices, and systems of the present disclosure do not include all of the features described, but still benefit from at least some of the advantages of such features. Those skilled in the art can easily implement their own methods, devices, and systems that incorporate one or more of the features of the present invention and are within the spirit and scope of the present disclosure as defined in the appended claims.

[0052] [Embodiment] (1) A unicompartmental tibial insert, a front end and a rear end; an articular surface extending from the anterior end to the posterior end and configured to articulate with a corresponding condyle of a natural or artificial femur; a bottom surface extending from the anterior end to the posterior end opposite the articular surface and configured to mate with a unicompartmental tibial tray, the bottom surface being non-planar; A unicompartmental tibial insert, wherein a vertical distance between the articular surface and the bottom surface defines a thickness of the tibial insert, the thickness of the tibial insert being constant between the anterior end and the posterior end. (2) the articular surface has a concave shape when viewed in a sagittal plane; 2. The unicompartmental tibial insert of embodiment 1, wherein the bottom surface has a convex shape when viewed in the sagittal plane. (3) the articular surface has a concave shape when viewed in a coronal plane; 3. The unicompartmental tibial insert of embodiment 2, wherein the bottom surface has a convex shape when viewed in the coronal plane. (4) A unicompartmental tibial insert as described in embodiment 1, wherein the curvature of the articular surface matches the curvature of the bottom surface. (5) A unicompartmental tibial insert as described in embodiment 1, wherein the thickness of the tibial insert is about 6 millimeters.

[0053] (6) A unicompartmental tibial insert, a front end and a rear end; an articular surface extending from the anterior end to the posterior end and configured to articulate with a corresponding condyle of a natural or artificial femur; a bottom surface extending from the anterior end to the posterior end opposite the articular surface and configured to couple with a unicompartmental tibial tray, the bottom surface including a flat base surface and a protrusion extending from the flat base surface, the protrusion having a curved outer surface. (7) The articular surface has a concave shape when viewed in a sagittal plane; 7. The unicompartmental tibial insert of claim 6, wherein the protrusion on the bottom surface has a convex shape when viewed in the sagittal plane. (8) the articular surface has a concave shape when viewed in a coronal plane; 8. The unicompartmental tibial insert of embodiment 7, wherein the protrusion on the bottom surface has a convex shape when viewed in the coronal plane. (9) A unicompartmental tibial insert as described in embodiment 6, wherein the vertical distance between the articular surface and the bottom surface defines a thickness of the tibial insert, and the thickness of the tibial insert is constant between the anterior end and the posterior end. (10) The unicompartmental tibial insert of embodiment 9, wherein the thickness of the tibial insert is about 6 millimeters.

[0054] (11) The unicompartmental tibial insert of embodiment 6, wherein a first vertical distance between the articular surface and the flat base surface of the bottom surface defines a first thickness, and a second vertical distance between the articular surface and the curved outer surface of the protrusion defines a second vertical distance equal to the first vertical distance. (12) The unicompartmental tibial insert of embodiment 6, wherein the vertical distance between the articular surface and the curved outer surface of the protrusion on the bottom surface defines a thickness of the protrusion, and the thickness of the protrusion is constant. (13) The unicompartmental tibial insert of embodiment 12, wherein the thickness of the protrusion is about 6 millimeters. (14) The unicompartmental tibial insert of embodiment 6, wherein the protrusion on the bottom surface is semi-elliptical in shape. (15) The unicompartmental tibial insert of embodiment 6, wherein the protrusion on the bottom surface is offset from the medial-lateral axis of the tibial insert toward the posterior end of the tibial insert.

[0055] (16) A tibial knee prosthesis, A front side and a rear side, a medial articular surface extending from the anterior side to the posterior side and configured to articulate with a medial condyle of a natural or artificial femur; a lateral articular surface extending from the anterior side to the posterior side and configured to articulate with a lateral condyle of the natural or artificial femur; a bottom surface extending from the anterior side to the posterior side opposite the medial and lateral articular surfaces, the bottom surface including a flat base surface and a projection extending from the flat base surface below the medial or lateral articular surface, the projection having a curved outer surface. (17) The tibial knee prosthesis of claim 16, further comprising a peg extending from the projection on the bottom surface. (18) Each of the medial articular surface and the lateral articular surface has a concave shape when viewed in a sagittal plane; 17. The tibial knee prosthesis of claim 16, wherein the protrusion on the bottom surface has a convex shape when viewed in the sagittal plane. (19) The tibial knee prosthesis of embodiment 16, wherein the perpendicular distance between the medial articular surface and the curved outer surface of the projection or between the lateral articular surface and the curved outer surface of the projection defines a thickness of the projection, the thickness of the projection being constant and approximately 6 millimeters. (20) The tibial knee prosthesis of embodiment 16, wherein the tibial insert comprises a polymer insert attached to a metal platform, the polymer insert including the medial articular surface and the lateral articular surface, and the metal platform includes a bottom surface having the flat base surface and the protrusion extending from the flat base surface below the medial articular surface or the lateral articular surface.

Claims

1. 1. A unicompartmental tibial prosthesis comprising: a unicompartmental tibial tray including a tibial platform having a curved upper surface and a curved bottom surface; 1. A unicompartmental tibial insert, comprising: a front end and a rear end; an articular surface extending from the anterior end to the posterior end and configured to articulate with a corresponding condyle of a natural or artificial femur; a bottom surface extending from the anterior end to the posterior end opposite the articular surface and configured to mate with the curved upper surface of the unicompartmental tibial tray, the bottom surface being non-planar; a unicompartmental tibial insert comprising: a vertical distance between the articular surface and the bottom surface defines a thickness of the unicompartmental tibial insert, the thickness of the unicompartmental tibial insert being constant between the anterior end and the posterior end; A unicompartmental tibial prosthesis, wherein the curvature of the articular surface, the curvature of the bottom surface, the curvature of the curved top surface, and the curvature of the curved bottom surface correspond to one another.

2. the articular surface has a concave shape when viewed in a sagittal plane; The unicompartmental tibial prosthesis of claim 1 , wherein the bottom surface has a convex shape when viewed in the sagittal plane.

3. the articular surface has a concave shape when viewed in a coronal plane; The unicompartmental tibial prosthesis of claim 2 , wherein the bottom surface has a convex shape when viewed in the coronal plane.

4. The unicompartmental tibial insert comprises:

2. The unicompartmental tibial prosthesis of claim 1, further comprising an outer sidewall extending from the articular surface and terminating at the bottom surface, a portion of the outer sidewall defining the anterior end and another portion of the outer sidewall defining the posterior end.

5. The unicompartmental tibial prosthesis of claim 1 , wherein the thickness of the unicompartmental tibial insert is approximately six millimeters.

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