Tibial prosthesis with distal features for non-cemented fixation

Abstract

To provide a tibial prosthesis with distal features for non-cemented fixation.SOLUTION: Techniques described herein relate to a tibial prosthesis for a knee arthroplasty optionally including a baseplate and a tibial keel. The baseplate optionally includes: a distal surface sized and shaped to substantially cover a proximal resected surface of a tibia; a proximal surface opposite the distal surface, the proximal surface having an outside compartment and an inside compartment opposite the outside compartment; a periphery extending between the distal surface and the proximal surface; a first layer of porous material forming at least a majority of the distal surface and extending to the periphery; and a second layer of nonporous or relatively less porous material having a plurality of reference features extending through the first layer, where the plurality of reference features form at least a portion of the distal surface. The tibial keel extends distally from the distal surface to define a longitudinal tibial keel axis.SELECTED DRAWING: Figure 1C-D

Description

Technical Field

[0001] This subject matter relates to orthopedic prostheses, and more particularly to tibial prostheses such as base plates used in knee arthroplasty.

Background Art

[0002] Orthopedic procedures and prostheses are widely utilized to repair and / or replace damaged bone and tissue within the human body. For example, knee arthroplasty can be used to restore the native knee function by repairing damaged or diseased articular surfaces of the femur and / or tibia. The interior of the knee joint is opened to expose the bone including the joint. A resection guide is used to guide the removal of the articular surface to be replaced. A prosthesis is used to restore the articular surface. The knee prosthesis can comprise a femoral component implanted at the distal end of the femur, and the femoral component is articulately coupled to a tibial bearing component and a tibial component (sometimes referred to as a tibial tray or tibial base plate) implanted at the proximal end of the tibia. These components together restore the function of a healthy native knee. Various types of arthroplasty, including knee arthroplasty where all articular compartments of the joint are restored by prosthesis components, are known.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Overview The present disclosure generally relates to a tibial prosthesis for use in knee arthroplasty, including total knee arthroplasty. The inventor has recognized, inter alia, a tibial baseplate including a distal mechanism that can facilitate better initial fixation to bone and better adhesion via ingrowth or on-growth of bone so as to fixedly hold the tibial baseplate to the proximal tibia. Better adhesion can reduce micromotion of the tibial baseplate and can provide better durability of the tibial baseplate. Further, the inventor has recognized that the distal mechanism can provide high rigidity and torsional strength to the tibial baseplate. Additionally, the inventor contemplates an instrument and system that allows a surgeon to prepare the tibia during surgery and also allows the surgeon to select a cemented or uncemented instrument during surgery. In particular, the cemented and uncemented instruments can share the same or similar stock sizes and can share the same or similar tibial keel and / or fin geometry (e.g., substantially the same distal profile, shape, size, etc. in two or more dimensions). This specification provides a system consisting of cemented instruments of different stock sizes and uncemented instruments of different stock sizes. However, these can share substantially the same geometry depending on the stock size. As an example, a surgeon has the option to switch during surgery from an uncemented instrument of a first stock size to a cemented instrument of the same first stock size. This can reduce the complexity and time of the surgical procedure. **Means for Solving the Problems**

[0004] Additional features and advantages of the various embodiments provided herein are discussed and / or will be apparent to those of ordinary skill in the art.

[0005] To further illustrate the instruments, systems, and methods disclosed herein, the following non-limiting examples are provided, which are referred to hereinafter as techniques. Some or all of these examples / techniques can be combined in any form.

[0006] In some embodiments, the techniques described herein relate to a tibial prosthesis for knee arthroplasty optionally including a baseplate and a tibial keel. The baseplate is dimensioned to substantially cover the proximal resection surface of the tibia and has a contoured distal surface, a proximal surface opposite the distal surface having a lateral section and a medial section opposite the lateral section, a peripheral portion extending between the distal surface and the proximal surface, a first layer of porous material forming at least a majority of the distal surface and extending to the peripheral portion, and optionally a second layer of non-porous material or relatively non-porous material having a plurality of reference features extending through the first layer, the plurality of reference features forming at least a portion of the distal surface, and the tibial keel extends distally from the distal surface to define a longitudinal tibial keel axis.

[0007] In some embodiments, the techniques described herein relate to a tibial prosthesis as described above, optionally further including a plurality of fins straddling the bifurcation point between the tibial keel and the distal surface.

[0008] In some embodiments, the techniques described herein relate to a tibial prosthesis as described above, optionally including that the plurality of fins are angled both anterior-posteriorly and medially-laterally so as to form flutes in the posterior portion of the tibial keel.

[0009] In some embodiments, the techniques described herein relate to a tibial prosthesis as described above, optionally including that the tibial keel includes a second flute and a third flute each extending to the distal tip of the tibial keel, and the second flute and the third flute are joined by an anterior fin at the anterior portion of the tibial keel.

[0010] In some embodiments, the techniques described herein relate to a tibial prosthesis as described above, further including a plurality of pegs extending distally from the distal surface, and optionally including that one or both of the plurality of pegs or the plurality of fins have windows formed from porous material.

[0011] In some aspects, the techniques described herein relate to a tibial prosthesis as described above, optionally including that a plurality of pegs include four pegs disposed adjacent to the respective rear-inner directional corner, rear-outer directional corner, front-outer directional corner, and front-inner directional corner of the periphery.

[0012] In some aspects, the techniques described herein relate to a tibial prosthesis as described above, optionally including that a plurality of pegs are configured to be press-fitted into a round hole drilled into the tibia and have a cross-section that is one of square or rectangular.

[0013] In some aspects, the techniques described herein relate to a tibial prosthesis as described above, optionally including that a window extends completely through at least one of a plurality of fins.

[0014] In some aspects, the techniques described herein relate to a tibial prosthesis as described above, optionally including that one or more surfaces of at least one of a tibial keel or a plurality of fins are fabricated to be smoother than the distal surface to prevent ingrowth of bone.

[0015] In some aspects, the techniques described herein relate to a tibial prosthesis system optionally including a plurality of prostheses, each of the plurality of prostheses having a baseplate sized and shaped to substantially cover the proximal resection surface of the tibia, and having a shaped distal surface, a proximal surface opposite the distal surface, the proximal surface having an outer section and an inner section opposite the outer section, a peripheral portion extending between the distal and proximal surfaces, and a plurality of pegs extending distally from the distal surface, wherein the size of each of the plurality of prostheses is different with respect to the distal surface, the proximal surface, and the peripheral portion, a baseplate, and a tibial keel extending distally from the distal surface to a domed distal tip, the tibial keel having an elongated length measured in the proximal-distal direction and defining a longitudinal tibial keel axis extending along the elongated length, the elongated length increasing stepwise with an increase in the size of the plurality of prostheses with respect to the distal surface, the proximal surface, and the peripheral portion, optionally including a tibial keel.

[0016] In some aspects, the techniques described herein relate to a system as described above optionally further including a plurality of fins straddling the bifurcation point between the tibial keel and the distal surface.

[0017] In some aspects, the techniques described herein further include a first layer of porous material forming at least a majority of the distal surface and extending to the peripheral portion, and a second layer of non-porous material or material that is not relatively porous forming a base, optionally including that the plurality of pegs are formed from both the porous material and the non-porous material or material that is not relatively porous, relating to a system as described above.

[0018] In some aspects, the techniques described herein relate to a system as described above, optionally including that the tibial keel includes a first flute on the posterior side formed between a plurality of fins added to the tibial keel, and the tibial keel includes a second flute and a third flute each extending to the distal tip of the tibial keel, the second flute and the third flute being joined by anterior fins at the anterior of the tibial keel.

[0019] In some embodiments, the techniques described herein relate to a system as described above, wherein a second layer of non-porous or relatively non-porous material has a plurality of reference features extending through the first layer, and the plurality of reference features optionally include forming at least a portion of the distal surface.

[0020] In some embodiments, the techniques described herein relate to a system as described above, wherein one or more surfaces of at least one of the tibial keel or the plurality of fins are optionally fabricated to be smoother than the distal surface to prevent ingrowth of bone.

[0021] In some aspects, the techniques described herein include a first tibial prosthesis having a first proximal surface and a first distal surface opposite the first proximal surface, the first distal surface being dimensioned and shaped to substantially cover the proximal resection surface of the tibia, at least one pocket formed within the first tibial prosthesis and recessed from the first distal surface, the at least one pocket being configured to receive bone cement therein, a first keel extending distally from the first distal surface, and a first plurality of fins spanning a junction of the first tibial keel and the first distal surface, and optionally a second tibial prosthesis having a second proximal surface and a second distal surface opposite the second proximal surface, the second distal surface being dimensioned and shaped to substantially cover the proximal resection surface of the tibia, a plurality of pegs extending distally from the second distal surface, a first layer of porous material forming at least a majority of the second distal surface, a second layer of non-porous material forming at least a portion of the second tibial prosthesis, a second keel extending distally from the second distal surface, and a second plurality of fins spanning a junction of the second keel and the second distal surface, the first keel and the first plurality of fins sharing substantially the same geometry as the second keel and the second plurality of fins, relating to a tibial prosthesis system.

[0022] In some aspects, the techniques described herein optionally include that substantially the same geometry includes at least two of an elongate length measured in the proximal-to-distal direction, a distal end profile, and a medial-to-lateral direction width, relating to a system as described above.

[0023] In some aspects, the techniques described herein relate to a system as described above, optionally including that a first plurality of fins are angled in an anterior-posterior direction and a medial-lateral direction such that the first plurality of fins form a first flute at a rear portion of a first tibial keel, a second plurality of fins are angled in an anterior-posterior direction and a medial-lateral direction such that the second plurality of fins form a first flute at a rear portion of a second tibial keel, and the first flute of the first tibial prosthesis and the first flute of the second tibial prosthesis have substantially the same angle.

[0024] In some aspects, the techniques described herein relate to a system as described above, optionally including that a first plurality of fins are relatively thinner than a second plurality of fins.

[0025] In some aspects, the techniques described herein relate to a system as described above, optionally including that a first tibial keel includes a second flute and a third flute each extending to a distal tip of the first tibial keel, a second tibial keel includes a second flute and a third flute each extending to a distal tip of the tibial keel, and the second flute and the third flute of the first tibial keel share substantially the same geometry as the second flute and the third flute of the second tibial keel.

[0026] In drawings which are not necessarily to scale, like reference numerals may represent similar components in different drawings. Like reference numerals with different subscripts may represent different instances of similar components. The drawings generally illustrate, by way of example and not limitation at all, various embodiments discussed in this specification.

Brief Description of the Drawings

[0027]

Fig. 1A - B

Fig. 1C - D

Fig. 1E - H

Fig. 1I - L

Fig. 2

Fig. 2A

Fig. 3A - B

Fig. 4A - B

Fig. 5A - B

Fig. 6A - B

Fig. 7A - B

Fig. 8A - B

Best Mode for Carrying Out the Invention

[0028] This application relates to a tibial prosthesis, specifically a tibial baseplate and system. This application focuses on the distal aspect and mechanisms of the tibial baseplate, as further discussed herein. As described above, these distal mechanisms can improve the fixation and durability of the tibial baseplate, among other advantages.

[0029] The terms "proximal" and "distal" as used herein should be given their generally understood anatomical interpretations. The term "proximal" generally means the direction towards the patient's torso, and the term "distal" means the direction opposite to proximal, i.e., away from the patient's torso. Needless to say, when using the terms "proximal" and "distal", this should be interpreted as if the patient were standing with the knee extended, even though the devices described herein are generally used with the knee bent. The intent is to distinguish the terms "proximal" and "distal" from the terms "anterior" and "posterior". The terms "anterior" and "posterior" as used herein should be given their generally understood anatomical interpretations. Thus, "posterior" means the back side of the patient, e.g., the back side of the knee. Similarly, "anterior" means the front side of the patient, e.g., the front side of the knee. Thus, "posterior" means the direction opposite to "anterior". Similarly, the term "lateral" means the direction opposite to "medial". The term "medial-lateral direction" means the direction from medial to lateral, or from lateral to medial. The term "proximal-distal" means the direction from proximal to distal or from distal to proximal. The term "anterior-posterior" means the direction from anterior to posterior or from posterior to anterior.

[0030] As used herein, the "periphery" of a tibial prosthesis means any periphery as seen in a top view, e.g., in an approximately transverse anatomical plane. Alternatively, the periphery of a tibial prosthesis may be any periphery as seen in a bottom view, e.g., in an approximately transverse plane and when viewing the distal surface configured to contact the resected proximal surface of the tibia. In the context of a prosthesis such as the tibial baseplate described below, the "home axis" is an axis oriented with respect to the baseplate such that after the baseplate is implanted in a proper rotational and spatial orientation, the home axis of the baseplate aligns with the home axis of the tibia. In some baseplate designs, including those illustrated herein, the home axis bisects the PCL notch at the posterior edge of the periphery of the tibial plateau and bisects the anterior edge at the anterior edge of the periphery of the tibial plateau. It is also contemplated to orient the home axis with respect to other baseplate mechanisms, and it is understood that the proper alignment and orientation of the baseplate on the tibia positions the home axis of the baseplate such that it coincides with the home axis of the tibia.

[0031] Since the home axis generally extends anteriorly and posteriorly when the baseplate is implanted on the tibia, the home axis of the tibial baseplate can be an anteroposterior axis. The tibial baseplate also defines a mediolateral axis that is located along the longest line segment contained within the periphery and is perpendicular to the home axis of the baseplate. As described below, the home axis and the mediolateral axis cooperate to define a coordinate system useful for quantifying certain baseplate mechanisms according to the present disclosure. In addition, distal mechanisms such as the keel and one or more fins can also be aligned with other axes such as the anteroposterior axis, the mediolateral axis, or the axis of symmetry, the proximal-distal axis.

[0032] Figures 1A through 1E are plan views showing various sides of the tibial baseplate 100. The tibial baseplate 100 can include a proximal surface 102, a distal surface 104, and a peripheral portion 106. As shown in Figures 1B through 1E, the tibial baseplate 100 can include a keel 108 and a plurality of fins 110A and 110B (both shown in Figure 1D).

[0033] Figure 1A is a plan view showing the proximal side of the tibial baseplate 100, showing the proximal surface 102, the anteroposterior axis AP, and the peripheral portion 106. A connection mechanism 112, such as a boss, rail, notch, and / or other mechanism, can be utilized on the proximal side for connection to a tibial bearing component (not shown). The structure of the connection mechanism 112 can be similar to that of the commercially available Persona® Total Knee System from Zimmer Biomet Inc. in Warsaw, Indiana.

[0034] The tibial baseplate 100 can have a specific asymmetry with respect to the home axis and the anteroposterior axis AP. Such a shape is designed to maximize the tibial coverage of most knee replacement candidates, as discussed in various previous applications by the applicant, including U.S. Patent Application Publication Nos. 2013 / 0024001A1 and 2013 / 0131820A1, the entire disclosures of which are incorporated herein by reference in their entirety. The maximized cortical bone coverage facilitates excellent support of the tibial baseplate 100. The large area of contact between the cortical and cancellous bone of the tibia facilitates firm and permanent fixation of the tibial baseplate 100 to the tibia.

[0035] The anteroposterior axis AP can divide the tibial baseplate 100 into an inner section 114 and an outer section 116. The inner section 114 can be shaped and dimensioned asymmetrically with respect to the outer section 116 defined along the peripheral portion 106. The peripheral portion 106 can be shaped as a wall and can have a connection mechanism 112 along one or more selected locations.

[0036] The tibial baseplate 100 can be utilized in a plurality of standard sizes. These standard sizes are selected to enable coverage for tibias of various sizes. As an example, the tibial baseplate 100 can include nine sizes from size 1 (short stature) to size 9 (tall stature). To make an appropriate size selection, a surgeon can utilize the various sizes as a system. The standard sizes have different geometries along the proximal side (e.g., the peripheral portion 106, the proximal surface 102, etc.) and the distal side (e.g., the distal surface 104, the keel 108, and the plurality of fins 110A and 110B, etc.), as further described herein.

[0037] Figures 1B through 1E show additional plan views of the tibial baseplate 100 as viewed from various sides. Figure 1B shows the keel 108 and one of the plurality of fins 110A. The fin 110A can extend between the keel 108 and the distal surface 104. The keel 108 can extend generally distally from the distal surface 104 and the remainder of the tibial baseplate 100. The fin 110A and / or 110B can be part of the assembly of the keel 108, but are described herein as a different mechanism from the remainder of the keel 108 that includes the stem mechanism. The keel 108 can form an angle θ with respect to the distal surface 104 (measured from the distal surface 104 to the axis of symmetry S1 of the keel 108). According to the embodiment of Figure 1B, the angle θ can be approximately 90 degrees. The axis of symmetry S1 of the keel 108 can be a proximal-distal direction axis.

[0038] Figure 1B shows that the keel 108 can include a stem mechanism having a distal tip 118. This distal tip 118 can be shaped to insert into the canal of the tibia. Thus, the distal tip 118 can be shaped, for example, as domed, hemispherical, or other shapes that are shaped so as not to have a sharp edge. The surface forming the distal tip 118 can have a geometry for forming an angle α of 30 degrees to 70 degrees (in some embodiments, approximately 50 degrees). The surface forming the distal tip 118 can be curved and can have, for example, a radius of curvature of 3 mm to 6 mm. According to one embodiment, the radius of curvature can be, for example, approximately 4.5 mm. The distal tip 118 can include, for example, a top. Note that the keel 108 having the distal tip 118 is not configured to connect to a stem extension or other mechanism as is common in some total knee systems. Rather, the keel 108 generally increases in proximal-distal length as the standard size of the tibial baseplate 100 increases.

[0039] Figures 1C and 1D show a keel 108 extending from the distal surface 104 and a plurality of fins 110A and 110B. The fins 110A and 110B can have a symmetric arrangement relationship and a mirror-image geometry with respect to each other and with respect to the keel 108 disposed on its opposing inner and outer sides. Although two fins 110A and 110B are shown in Figures 1C and 1D, in other embodiments three or more fins can be contemplated. The keel 108 can include a first groove with a first flute 120A and a second groove with a second flute 120B. The first flute 120A and the second flute 120B can extend from a few millimeters from the distal surface 104 to the distal tip 118. Thus, the first flute 120A and the second flute 120B can extend over a majority (e.g., 50% to 95% of the length) of the proximal-distal length of the keel 108. The first flute 120A and the second flute 120B can be positioned generally on the front side of the keel 108 so as to face forward. The first flute 120A and the second flute 120B can be shaped symmetrically with respect to each other. The geometry of the first flute 120A and the second flute 120B will be discussed further subsequently.

[0040] The keel 108 and fins 110A and 110B can, in addition, form a third flute 120C (FIG. 1D) or a recessed area along the rear side of the keel 108 and fins 110A and 110B. The third flute 120C can be formed mainly by the fins 110A and 110B that can be angled with respect to each other to form an angle β. In particular, the fins 110A and 110B can extend not only in the proximal-distal direction (in some embodiments, as the keel 108), but also further in the medial-lateral direction and the anterior-posterior direction. The angle β can be, for example, approximately 105 degrees to 140 degrees. According to one embodiment, the angle β can be approximately 126 degrees. The fins 110A and 110B can have a radius of curvature with respect to the keel 108 along their rear side. This radius of curvature can be approximately 5 mm to 10 mm. According to one embodiment, the radius of curvature can be approximately 7.6 mm. The thickness T (FIG. 1D) of the fins 110A and 110B can vary as desired, but in the case of a non-cemented prosthesis of the same stock size, it can be relatively thicker compared to a cemented prosthesis. Note that the thickness T changes when moving in the proximal-distal direction along the fins 110A and 110B. However, the thickness T of a non-cemented prosthesis of the same stock size can be relatively thicker compared to the thickness of a cemented prosthesis at the same proximal-distal position.

[0041] The distal surface 104 and other mechanisms, such as the window 126 in FIGS. 1E to 1G, will be described subsequently. These mechanisms can be formed from a porous or highly porous material that promotes endochondral bone growth. For example, the distal surface and the window 126 may be composed of, or coated with, a highly porous biomaterial. The highly porous material is useful as a bone substitute and as a material capable of receiving cells and tissues. The porosity of the highly porous biomaterial can be as low as 30%, 55%, or as high as 70%, 80%, 85%, or 90%. The average pore size of the highly porous biomaterial can be, for example, from 100 microns to 1000 microns.

[0042] An example of such a porous or highly porous material is OsseoTi® which is generally available from Zimmer Biomet Inc. in Warsaw, Indiana. The material can comprise titanium or a titanium alloy and can additionally comprise other materials. Such materials (including a relatively non-porous or non-porous biocompatible base) can be manufactured using additive manufacturing processes such as laser sintering or the like. OsseoTi® is highly biocompatible, has high corrosion resistance, and includes a highly interconnected porous architecture that mimics the porous structure of human cancellous bone and can improve bone integration and ingrowth. The porous or highly porous material can be manufactured to be laminated with / on top of, or structured with, a relatively non-porous or non-porous biocompatible material such as titanium, a titanium alloy, stainless steel, or other materials known to those skilled in the art.

[0043] Another example of such a porous or highly porous material is manufactured using Trabecular Metal® which is generally available from Zimmer Biomet Inc. in Warsaw, Indiana. Such materials are disclosed in detail in Kaplan's U.S. Patent No. 5,282,861, the entire disclosure of which is hereby expressly incorporated by reference herein, and may be formed from a reticulated vitreous carbon foam substrate that is infiltrated and coated with a biocompatible metal such as tantalum by a chemical vapor deposition (CVD) process. In addition to tantalum, other metals such as niobium, or alloys of tantalum and niobium with each other or with other metals may be used. The porous tantalum structure may be formed at various densities to selectively tailor the structure for a particular application. In particular, as discussed in the above-incorporated U.S. Patent No. 5,282,861, the porous tantalum may be fabricated to have virtually any desired porosity and pore size and may be adapted to harmonize with the native bone at the periphery to provide an improved matrix for endochondral bone growth and calcification.

[0044] Generally, the porous material structure under consideration can include a number of ligaments that define an open space therebetween, and each ligament generally includes a core covered by a thin metal film. The open space between the ligaments forms a matrix of continuous channels without dead ends so as not to inhibit the growth of cancellous bone through the porous tantalum structure. The porous or highly porous material may include void space up to 70%, 85%, or more. Thus, the porous or highly porous material is a lightweight and strong porous structure with a generally uniform and consistent composition, and is very similar to the structure of native cancellous bone. This provides a matrix into which cancellous bone can grow internally to enable fixation of the tibial baseplate 100 to the patient's bone.

[0045] Referring to FIG. 1D, various distal mechanisms such as pegs 122A, 122B, 122C, and 122D, as well as reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F are shown. The pegs 122A, 122B, 122C, and 122D can have a square or rectangular shape. The width dimension of the pegs 122A, 122B, 122C, and 122D can be on the order of 2.5 mm to 7.5 mm. The proximal-distal direction length (depth) of the pegs 122A, 122B, 122C, and 122D can be, for example, 5 mm to 15 mm. The square or rectangular pegs 122A, 122B, 122C, and 122D can be configured to be press-fitted into round (cross-sectional) holes having a similar or smaller diameter drilled into the tibia.

[0046] According to one embodiment, the proximal-distal direction length (depth) of pegs 122A, 122B, 122C, and 122D can be from 7.5 mm to 12.5 mm. The pegs 122A, 122B, 122C, and 122D can be arranged asymmetrically with respect to the keel 108, fins 110A, 110B, peripheral portion 106, anteroposterior axis AP (FIG. 1A), and / or the medial-lateral axis. The pegs 122A, 122B, 122C, and 122D can be arranged within 15 mm or less from the peripheral portion 106. In particular, the pegs 122A, 122B, 122C, and 122D can be arranged adjacent to (within 12 mm or less) the front-medial direction corner, rear-medial direction corner, rear-lateral direction corner, and front-lateral direction corner of the peripheral portion 106, respectively. Similarly, the pegs 122A, 122B, 122C, and 122D can be arranged within 10 mm or less from each one of the fins 110A, 110B. The pegs 122A, 122B, 122C, and 122D can be oriented at approximately 90 degrees or another angle with respect to the distal surface 104.

[0047] The reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F can include circular, cylindrical, or other shaped mechanisms on a base made of a relatively non-porous or non-porous biocompatible material. The reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F project distally from a base (not shown in FIG. 1D but shown in FIG. 1L) and form at least a portion of the distal surface 104 of the tibial base plate 100. The reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F are relatively small, on the order of 0.5 mm to 2.0 mm in diameter. Since at least most (and preferably more) of the distal surface 104 can be formed from a porous or highly porous material, it can be difficult to determine the overall flatness or angulation of the distal surface 104 having such a material. Thus, the reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F formed from a relatively non-porous or non-porous biocompatible material can be utilized. The reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F can be disposed at various locations and project to form the distal surface 104 at various locations. By measuring the reference mechanisms 124A, 124B, 124C, 124D, 124E, and 124F at various locations on the distal surface 104, it can be determined whether the distal surface 104 has the desired overall flatness or angulation.

[0048] FIG. 1E shows a plan view of the tibial base plate 100 as viewed from the posterior-medial or posterior-lateral side, showing both of the plurality of fins 110A and 110B. FIG. 1E also shows the window 126. The window 126 can be formed, for example, in the fins 110A, 110B, the keel 108, and / or the pegs 122A, 122B, 122C, and 122D. The window 126 can be formed from the same porous or highly porous material or can be formed similarly to at least most of the distal surface 104.

[0049] FIG. 1F is an enlarged view of a portion of fin 110A and shows one of the windows 126. The window 126 can have an inner-outer width that is elongated with respect to the proximal-distal depth. The inner-outer width can be, for example, from 5 mm to 10 mm. According to one embodiment, the inner-outer width can be about 6 mm. According to one embodiment, the proximal-distal depth can be 1.7 mm. The edge of the window 126 can be located from about 3.5 mm to 6.5 mm from the distal edge of the fin 110A.

[0050] FIG. 1G shows a window 126 having a porous or highly porous material 128. The window 126 can pass completely through a portion of the fin 110A and can form a portion of the fin 110. The window 126 can be positioned adjacent to (in its distal direction) the distal surface 104 formed within the indicated area by the porous or highly porous material 128. In particular, the distal portion and most of the fin 110A along the distal surface can be composed of a relatively non-porous or non-porous biocompatible material. In fact, according to some embodiments, the fins 110A, 110B (not shown in FIG. 1G), and the keel 108 (not shown in FIG. 1G) can be fabricated to have a relatively smooth surface finish (e.g., less than 8.0 micron Ra) compared to the surface finish of the distal surface 104 or other portions of the tibial baseplate 100 (e.g., as-printed, machined, dry-blasted, etc.). Such a relatively smooth surface finish can prevent bone ingrowth or surface growth at the distal portions / distal surfaces of the fins 110A, 110B, keel 108, and / or pegs compared to the distal surface 104 and window 126 formed of the porous or highly porous material 128. However, the surface finish of the fins 110A and / or 110B and / or the keel 108 is not contemplated in some embodiments.

[0051] Figure 1H shows a cross-section of the tibial base plate 100 including the distal surface 104, pegs 122A and 122B, reference mechanisms 124A, 124B and 124C, window 126, base B and the porous or highly porous material 128. The pegs 122A and 122B can be symmetrically shaped and can have relatively the same size and shape. The distal ends 130 of the pegs 122A and 122B are pyramidal and can be angled at about 30 degrees with respect to their axis of symmetry. Thus, the pegs 122A and 122B can form an angle θ with respect to the sides of the distal ends 130 facing each other. The angle θ can be, for example, about 60 degrees. The distal ends 130 can have, for example, a blunt tip 132 less than 1.0 mm in the major dimension.

[0052] As shown in the embodiment of FIG. 1H, the porous or highly porous material 128 need not extend completely through the pegs 122A and 122B at the window 126 and may cover the proximal base portions 134 of the pegs 122A and 122B from a depth of 0.25 mm to 1.5 mm. In particular, most of the pegs 122A and 122B along the distal portion, distal ends 130 and distal surface can be composed of a relatively non-porous or non-porous biocompatible material.

[0053] Figures 1I through 1K show cross-sectional views of the keel 108 and the plurality of fins 110A and 110B, showing mechanisms such as a first flute 120A, a second flute 120B, and a third flute 120C. As shown in FIGS. 1I through 1K, the keel and the plurality of fins 110A and 110B can taper from a location adjacent to the distal face toward the distal tip. The first flute 120A and the second flute 120B can be separated by the front fin 140. The front fin 140 can form the foremost portion of the keel 108 and can have a substantially uniform width over at least a majority of the proximal-distal length of the keel 108. The width of the front fin 140 can be on the order of 1 mm to about 3 mm, for example, over a majority of its longitudinal length. The width of the front fin 140 can increase adjacent to the proximal portion of the keel 108 shown in FIG. 1I. The first flute 120A can have an angle θ1 of from about 100 degrees to about 140 degrees. According to one embodiment, the angle θ1 can be about 117 degrees. Similarly, the second flute 120B can also have an angle θ1 of from about 100 degrees to about 140 degrees. According to one embodiment, the angle θ1 can be about 117 degrees. The keel 108 may not have a taper and may not be tapered substantially along at least a majority or more of its proximal-distal length. The fins 110A and 110B can be tapered as described above.

[0054] Fins 110A and 110B can be formed monolithically or integrally with the remainder of the tibial base plate 100 including the distal surface 104 and the keel 108. Thus, fins 110A and 110B can be the mechanism of the keel 108 described above. However, it is also conceivable that fins 110A and 110B can be separately attached to other mechanisms of the tibial base plate 100. Alternatively, fins 110A and 110B can be formed monolithically together as a single piece and can also be connected separately from the keel 108 or the distal surface 104. The keel 108 and / or fins 110A and 110B can be formed by a layered manufacturing process such as laser sintering or the like (either together with each other or not together with each other, and together with or without the remainder of the tibial base plate 100).

[0055] Similarly, referring to FIG. 1H, mechanisms such as pegs 122A, 122B, reference mechanisms 124A, 124B and 124C, window 126, and porous or highly porous material 128 can be formed monolithically or integrally with the base B by a layered manufacturing process or other processes, etc.

[0056] FIG. 1L shows an enlarged view of the reference mechanism 124A of FIG. 1H. The reference mechanism 124A can have a distal end that forms a part of the distal surface 104. The reference mechanism 124A can extend generally distally from the base B and can be formed from the same or a similar material as the base B, such as a relatively non-porous or non-porous biocompatible material 150. This relatively non-porous or non-porous material 150 can be joined to the porous or highly porous material 128 using laser sintering, an adhesive layer, or other techniques known to those skilled in the art.

[0057] In other words, the porous or highly porous material 128 can form at least a first layer 152 that forms at least a majority of the distal surface 104. The relatively non-porous or non-porous material 150 can include at least a second layer 154. The reference mechanism 124A can extend through the first layer 152 and can form at least a portion of the distal surface 104.

[0058] FIG. 2 shows a system 200 that includes tibial base plates 100A, 100B, and 100C of various sizes. The tibial base plate 100A can be a standard size 1 configured for a patient having a knee corresponding to a low stature. The tibial base plate 100B can be a standard size 5 configured for a patient having a knee corresponding to a medium stature. The tibial base plate 100C can be a standard size 8 configured for a patient having a knee corresponding to a tall stature. The tibial base plates 100A, 100B, and 100C can be configured to provide a desired amount of coverage of the resected tibia without overhang or other undesirable placement configurations. The tibial base plates 100A, 100B, and 100C can vary in dimensions such as an inner-lateral direction extension (e.g., measured from a first most medial edge of the periphery to a second most lateral edge) and an anterior-posterior direction extension (e.g., measured from a third most anterior edge of the periphery to a fourth most posterior edge). However, the inner-lateral direction width W1 of the tibial base plate 100A may vary from that of the tibial base plate 100B or the tibial base plate 100C by only, for example, 20 mm or less. Thus, the inner-lateral width W1 may not increase significantly with the change in standard size in a way that commiserates with other dimensions (e.g., the inner-lateral direction extension of the periphery, the anterior-posterior direction extension of the periphery). The proximal-distal direction length L1 of the tibial base plate 100A may vary from that of the tibial base plate 100B or the tibial base plate 100C by only, for example, the substantial amount shown in FIGS. 2 and 2A.

[0059] Figure 2 shows that the tibial base plates 100A, 100B, and 100C are not all structurally stemmable (although a stemmable structure is also conceivable). Thus, the proximal-distal length of the keel 108A generally increases with an increase in the standard size. Thus, the proximal-distal length of the keel 108A of the tibial base plate 100A is relatively shorter than that of the keels 108B and 108C. FIG. 2A shows that by having two or more different standard sizes share the same proximal-distal length respectively, it is possible to increase the proximal-distal length of the keel 108A in a stepwise manner. In other words, the proximal-distal length does not increase linearly and smoothly with an increase in the standard size, but increases stepwise. Thus, at least two of the standard sizes (and in some cases up to four of the standard sizes) share the same proximal-distal length.

[0060] An exemplary length of the keel per standard size is provided in FIG. 2A. Note that the keel length does not transition linearly and smoothly, but has a step function such that several sizes (size 1 to 2, size 3 to 6, and size 7 to 9) can share substantially the same proximal-distal length. However, the general trend shown by the best-fit curve is that the proximal-distal length of the keel increases linearly with the change in size. It should be noted that other mechanisms discussed herein, such as the flute angle, flute radius, medial-lateral width of the flute, size of the front fin (medial-lateral width), and / or fin radius, angle of the rear flute (e.g., the angle between fins), distal tip of the keel geometry, etc., may remain substantially constant in geometry even as the standard size changes. Thus, for example, the tibial base plate 100A of standard size 1 will have a front groove of the same size (medial-lateral direction) as that of the tibial base plate 100C (see FIG. 2) of standard size 8.

[0061] Figures 3A through 8B illustrate another aspect of the tibial baseplate system 300. In particular, the system 300 includes, for example, tibial baseplates 100D (Figs. 3A and 3B), 100E (Figs. 4A and 4B), 100F (Figs. 5A and 5B), 100G (Figs. 6A and 6B), 100H (Figs. 7A and 7B), and 100I (Figs. 8A and 8B).

[0062] Tibial baseplates 100D and 100E are of the same standard size (e.g., standard size 2), but may have different structures in that tibial baseplate 100D is configured for non-cement fixation (rather, it utilizes ingrowth) as compared to tibial baseplate 100E which is configured for cement fixation. Similarly, tibial baseplates 100F and 100G are of the same standard size (e.g., standard size 4), but may have different structures in that tibial baseplate 100F is configured for non-cement fixation (rather, it utilizes ingrowth) as compared to tibial baseplate 100G which is configured for cement fixation. Tibial baseplates 100H and 100I are of the same standard size (e.g., standard size 7), but may have different structures in that tibial baseplate 100H is configured for non-cement fixation (rather, it utilizes ingrowth) as compared to tibial baseplate 100I which is configured for cement fixation.

[0063] The tibial base plates 100D and 100E can share substantially the same size (e.g., the medial-lateral extent of the periphery can be substantially the same, the anterior-posterior extent of the periphery can be substantially the same, etc.). Additionally, the geometry of the distal mechanisms of the tibial base plates 100D and 100E can also be substantially the same. This includes the geometries of the plurality of aspects of the keel 108D and fins 110D, 110DD of the tibial base plate 100D as compared to the corresponding aspects of the keel 108E and fins 110E, 110EE of the tibial base plate 100E. Thus, as shown from FIGS. 3A to 4B, the keel 108D and fins 110D, 110DD of the tibial base plate 100D can share substantially the same distal profile 302 (measured along the most distal-facing surfaces of the keel 108D and fins 110D, 110DD moving in the medial-lateral direction along the extent of the keel 108D and fins 110D, 110DD) with the keel 108E and fins 110E, 110EE of the tibial base plate 100E. In other words, the keels 108D and 108E can share the same geometric features such as, but not limited to, proximal-distal length, diameter, groove shape and size, flute size and shape, thickness, etc. Similarly, the fins 110D, 110DD can share the same geometry (angle, medial-lateral width, proximal-distal length, etc.) with the fins 110E, 110EE. This substantial shape match between the keel 108D and fins 110D, 110DD and the keel 108E and fins 110E, 110EE allows the surgeon to select a cemented or uncemented implant during the surgery. This eliminates the need to perform reaming or other surgical procedures that would be necessary for switching from a cemented implant to an uncemented implant (or vice versa), reducing time and complexity. According to some embodiments, the fins 110D, 110DD and the fins 110E, 110EE may differ only in that the thickness of the fins 110D, 110DD is slightly greater than the corresponding thickness of the fins 110E, 110EE.

[0064] As discussed with respect to tibial base plates 100D and 100E, tibial base plates 100F and 100G can also share substantially the same size (e.g., the medial-lateral extent of the periphery can be substantially the same, the anterior-posterior extent of the periphery can be substantially the same, etc.). Additionally, the geometry of the distal mechanisms of tibial base plates 100F and 100G can also be substantially the same. This includes the geometry of the plurality of aspects of keel 108F and fins 110F, 110FF of tibial base plate 100F when compared to the corresponding aspects of keel 108G and fins 110G, 110GG of tibial base plate 100G. Thus, as shown in FIGS. 5A through 6B, keel 108F and fins 110F, 110FF of tibial base plate 100F can share substantially the same distal profile 304 (measured along the most distal-facing surfaces of keel 108F and fins 110F, 110FF as they move in the medial-lateral direction along the extent of keel 108F and fins 110F, 110FF) with keel 108G and fins 110G, 110GG of tibial base plate 100G. In other words, keels 108F and 108G can share the same geometric features such as, but not limited to, proximal-distal length, diameter, groove shape and size, flute size and shape, etc. Similarly, fins 110F, 110FF can share the same geometry (angle, medial-lateral width, proximal-distal length, thickness, etc.) with fins 110G, 110GG. According to some embodiments, fins 110F, 110FF and fins 110G, 110GG may differ only in that the thickness of fins 110F, 110FF is slightly greater than the corresponding thickness of fins 110G, 110GG.

[0065] The tibial base plates 100H and 100I can share substantially the same size (e.g., the medial-lateral extent of the periphery can be substantially the same, the anterior-posterior extent of the periphery can be substantially the same, etc.). Additionally, the geometry of the distal mechanisms of the tibial base plates 100H and 100I can also be substantially the same. This includes the geometries of the keel 108H and fins 110H, 110HH of the tibial base plate 100H compared to the corresponding aspects of the keel 108I and fins 110I, 110II of the tibial base plate 100I. Thus, as shown in FIGS. 7A through 8B, the keel 108H and fins 110H, 110HH of the tibial base plate 100H can share substantially the same distal profile 306 (measured along the most distal-facing surfaces of the keel 108H and fins 110H, 110HH as they move in the medial-lateral direction along the extent of the keel 108H and fins 110H, 110HH) with the keel 108I and fins 110I, 110II of the tibial base plate 100I. In other words, the keels 108H and 108I can share the same geometry of features such as, but not limited to, proximal-distal length, diameter, groove shape and size, flute size and shape, etc. Similarly, the fins 110H, 110HH can share the same geometry (angle formation, medial-lateral width, proximal-distal length, thickness, etc.) as the fins 110I, 110II. According to some embodiments, the fins 110H, 110HH and the fins 110I, 110II may differ only in that the thickness of the fins 110H, 110HH is slightly greater than the corresponding thickness of the fins 110I, 110II.

[0066] According to the embodiments provided in this specification, the tibial baseplate can include a cruciate retaining (CR) design. Thus, the tibial baseplate can have a relief for the posterior cruciate ligament that is not resected during implantation. However, other prosthesis designs are also contemplated, including, for example, a posterior-stabilized (PS) design, a mid-level constraint (MLC) or a constrained posterior stabilized (CPS) design, and an ultra-congruent (UC) design. The PS and MLC designs utilize a spine and a cam as known to those skilled in the art. Since the posterior cruciate ligament is excluded, there is no need for a relief.

[0067] Supplementary Note The detailed description above includes references to the accompanying drawings. These drawings form a part of the detailed description. The drawings illustrate, by way of example, specific embodiments in which the invention may be practiced. Such embodiments are also referred to herein as "examples." Such examples may include elements in addition to those illustrated or described. However, the inventor also contemplates examples in which only the elements illustrated or described are provided. Further, the inventor also contemplates examples that use combinations or substitutions of the elements (or one or more aspects thereof) illustrated and described with respect to a particular example (or one or more aspects thereof) illustrated or described, or with respect to other examples (or one or more aspects thereof).

[0068] In this document, the terms "generally", "substantially", and "about" mean within 15 percent (±) of the provided value. The terms "a" or "an" are used to include one or more than one, independent of any other instance or use such as "at least one" or "one or more", as is common in patent documents. In this document, the term "or" means non-exclusive or, such that, unless otherwise specified, "A or B" is used to include "A but not B", "B but not A", and "A and B". In this document, the terms "including" and "in which" are used as plain English equivalents of the respective terms "comprising" and "wherein". Also, in the following claims, "including" and "comprising" are open-ended, i.e., a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such terms in the claims, and these elements are still considered to be within the scope of the claims. Further, in the following claims, terms such as "first", "second", and "third" are used merely as labels and do not impose numerical requirements on these objects.

[0069] The above description is intended to be illustrative and not restrictive. For example, the above embodiments (or one or more aspects thereof) can be used in combination with each other. From an overview of the above description, other embodiments can be used by, for example, those skilled in the art. The abstract is provided to comply with 35 U.S.C. § 1.72(b) to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above detailed description, the disclosure can be simplified by grouping various features together. This should not be construed as intending that features disclosed outside the claims are essential to any of the claims. Rather, the subject matter of the present invention does not lie in all of the features of the particular embodiments disclosed. Accordingly, the following claims are here incorporated by reference into the detailed description as examples or embodiments. Each claim stands on its own as a separate embodiment, and such embodiments can be combined with each other in various combinations or permutations. The scope of the present invention should be determined by reference to the appended claims, along with the full scope of equivalents to such claims.

Claims

**Claim 1** A tibial prosthesis for knee arthroplasty, comprising: A base plate, Dimensioned and shaped to substantially cover the proximal resection surface of the tibia and having a shaped distal surface, A proximal surface opposite the distal surface, the proximal surface having an outer section and an inner section opposite the outer section, A peripheral portion extending between the distal surface and the proximal surface, A first layer of porous material forming at least a majority of the distal surface and extending to the peripheral portion, and A second layer of non-porous material or a material that is not relatively porous having a plurality of reference mechanisms extending through the first layer, the plurality of reference mechanisms forming at least a part of the distal surface, the base plate including the second layer; A tibial keel extending distally from the distal surface to define a longitudinal tibial keel axis; A tibial prosthesis for knee arthroplasty. **Claim 2** The tibial prosthesis according to claim 1, further comprising a plurality of fins straddling a branch point between the tibial keel and the distal surface. **Claim 3** The tibial prosthesis according to claim 2, wherein the plurality of fins are angled in the anterior-posterior direction and the medial-lateral direction so as to form flutes at the rear of the tibial keel. **Claim 4** The tibial prosthesis according to claim 3, wherein the tibial keel includes a second flute and a third flute each extending to a distal tip of the tibial keel, and the second flute and the third flute are joined by an anterior fin at the anterior of the tibial keel. **Claim 5** The tibial prosthesis according to any one of claims 2 to 4, further comprising a plurality of pegs extending distally from the distal surface, wherein one or both of the plurality of pegs or the plurality of fins have windows formed from a porous material. **Claim 6** The tibial prosthesis according to claim 5, wherein the plurality of pegs include four pegs disposed adjacent to respective posterior-medial direction corners, posterior-lateral direction corners, anterior-lateral direction corners, and anterior-medial direction corners of the peripheral portion. **Claim 7** The tibial prosthesis according to claim 5 or claim 6, wherein the plurality of pegs have a cross-section that is one of square or rectangular and are configured to be press-fitted into round holes drilled into the tibia. **Claim 8** The tibial prosthesis according to any one of claims 5 to 7, wherein the window extends completely through at least one of the plurality of fins.

9. The tibial prosthesis according to any one of claims 2 to 8, wherein at least one of the tibial keel or the plurality of fins has one or more surfaces fabricated to be smoother than the distal surface to prevent endosteal growth of bone.

10. A tibial prosthesis system, comprising a plurality of prostheses, each of the plurality of prostheses being a baseplate, dimensioned and shaped to substantially cover the proximal resection surface of the tibia and having a distal surface, a proximal surface opposite the distal surface, the proximal surface having an outer section and an inner section opposite the outer section, a peripheral portion extending between the distal surface and the proximal surface, and a plurality of pegs extending distally from the distal surface, wherein the size of each of the plurality of prostheses is different with respect to the distal surface, the proximal surface, and the peripheral portion, a baseplate, and a tibial keel extending distally from the distal surface to a domed distal tip, the tibial keel having an elongated length measured in the proximal - distal direction and defining a longitudinal tibial keel axis extending along the elongated length, the elongated length increasing stepwise with an increase in the size of the plurality of prostheses with respect to the distal surface, the proximal surface, and the peripheral portion, a tibial keel, including. A tibial prosthesis system.

11. The system according to claim 10, further comprising a plurality of fins straddling a branch point between the tibial keel and the distal surface.

12. A first layer of porous material forming at least a majority of the distal surface and extending to the peripheral portion, and a second layer of non - porous material or a material that is not relatively porous forming a base, further comprising, wherein the plurality of pegs are formed from both the porous material and the non - porous material or the material that is not relatively porous.

13. The tibial keel includes, in addition to the tibial keel, a first flute on the rear side formed between the plurality of fins, and the tibial keel includes a second flute and a third flute each extending to the distal tip of the tibial keel, and the second flute and the third flute are joined by a front fin at the front of the tibial keel. The system according to claim 12.

14. The second layer of the non-porous material or the material that is not relatively porous has a plurality of reference mechanisms extending through the first layer, and the plurality of reference mechanisms form at least a part of the distal surface. The system according to claim 12 or claim 13.

15. One or more surfaces of at least one of the tibial keel or the plurality of fins are fabricated to be smoother than the distal surface to prevent endosteal growth of bone. The system according to any one of claims 10 to 14.

16. A tibial prosthesis system, A first tibial prosthesis, A first proximal surface, A first distal surface on the side opposite to the first proximal surface, dimensioned and shaped to substantially cover the proximal resection surface of the tibia, and a first distal surface, At least one pocket formed in the first tibial prosthesis and recessed from the first distal surface, configured to receive bone cement, and at least one pocket, A first keel extending distally from the first distal surface, A first plurality of fins straddling the branch point between the first keel and the first distal surface, A first tibial prosthesis comprising, and A second tibial prosthesis, A second proximal surface, A second distal surface on the side opposite to the second proximal surface, dimensioned and shaped to substantially cover the proximal resection surface of the tibia, and a second distal surface, A plurality of pegs extending distally from the second distal surface, A first layer of porous material forming at least a majority of the second distal surface, A second layer of non-porous material forming at least a part of the second tibial prosthesis, A second keel extending distally from the second distal surface, A second plurality of fins straddling the branch point between the second keel and the second distal surface, A second tibial prosthesis comprising, Comprising, A tibial prosthesis system in which the first keel and the first plurality of fins share substantially the same geometry as the second keel and the second plurality of fins.

17. The system of claim 16, wherein the substantially same geometry includes at least two of an elongate length measured in the proximal - distal direction, a distal end profile, and a medial - lateral direction width.

18. The first plurality of fins are angled in the anterior - posterior direction and the medial - lateral direction so as to form a first flute at the rear of the first tibial keel, and the second plurality of fins are angled in the anterior - posterior direction and the medial - lateral direction so as to form a first flute at the rear of the second tibial keel, and the first flute of the first tibial prosthesis and the first flute of the second tibial prosthesis have substantially the same angle, the system of claim 17.

19. The system according to any one of claims 16 to 18, wherein the first plurality of fins are relatively thinner than the second plurality of fins.

20. The first tibial keel includes a second flute and a third flute each extending to the distal tip of the first tibial keel, and the second tibial keel includes a second flute and a third flute each extending to the distal tip of the tibial keel, and the second flute and the third flute of the first tibial keel share substantially the same geometry as the second flute and the third flute of the second tibial keel, the system according to any one of claims 16 to 19.

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