Tibial prosthesis with distal mechanism for uncemented fixation

Abstract

To provide a tibial prosthesis having a distal mechanism for non-cemented fixation.SOLUTION: Techniques described herein relate to a tibial prosthesis for a knee arthroplasty including a baseplate and a tibial keel. The baseplate arbitrarily includes a distal surface 104 sized and shaped to substantially cover a proximal resected surface of a tibia; a proximal surface opposite the distal surface, the proximal surface having a lateral compartment and a medial compartment opposite the lateral 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, wherein the plurality of reference mechanisms 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] The present subject matter relates to orthopedic prostheses, and more particularly to tibial prostheses, such as baseplates used in knee arthroplasty. [Background technology]

[0002] Orthopedic procedures and prostheses are widely used to repair and / or replace damaged bones and tissues within the human body. For example, knee arthroplasty can be used to restore natural knee function by repairing damaged or diseased articular surfaces of the femur and / or tibia. An incision is made within the knee joint to expose the bones that comprise 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. A knee prosthesis can include a femoral component implanted at the distal end of the femur, which articulates with a tibial bearing component and a tibial component (sometimes called a tibial tray or tibial baseplate) implanted at the proximal end of the tibia. Together, these components restore the function of a healthy, natural knee. Various types of knee arthroplasty are known, including knee arthroplasty in which all articular compartments of the joint are repaired with prosthetic components. Summary of the Invention [Problem to be solved by the invention]

[0003] Overview The present disclosure generally relates to tibial prostheses used in knee arthroplasty, including total knee arthroplasty. The inventors have recognized, among other things, tibial baseplates that include distal features that may facilitate better initial fixation to the bone and better adhesion via bony ingrowth or on-growth, so that the tibial baseplate can be securely retained on the proximal tibia. Better adhesion can reduce micromotion of the tibial baseplate and provide greater durability for the tibial baseplate. The inventors have further recognized that the distal features may provide greater stiffness and torsional strength to the tibial baseplate. Additionally, the inventors contemplate instruments and systems that allow a surgeon to intraoperatively prepare the tibia, but also allow the surgeon to intraoperatively select cemented or uncemented instruments. In particular, the cemented and uncemented instruments can share the same or similar stock sizes and the same or similar tibial keel and / or fin geometries (e.g., substantially the same distal profile, shape, size, etc. in two or more dimensions). Provided herein is a system of cemented instruments of different stock sizes and uncemented instruments of different stock sizes, which may, however, share substantially the same geometry depending on the stock size. As an example, a surgeon has the option to switch from uncemented instruments of a first stock size to cemented instruments of the same first stock size during surgery. This may reduce the complexity and time of the surgical procedure. [Means for solving the problem]

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

[0005] To further illustrate the devices, systems, and methods disclosed herein, the following non-limiting examples are provided, hereinafter referred to as techniques. Any or all of these examples / techniques may be combined in any manner.

[0006] In some aspects, the technology described herein relates to a tibial prosthesis for knee arthroplasty, optionally including a baseplate and a tibial keel, the baseplate having a distal surface sized and shaped to substantially cover a proximal resected surface of the tibia, a proximal surface opposite the distal surface, the proximal surface having a lateral section and a medial section opposite the lateral section, a periphery extending between the distal and proximal surfaces, 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 non-porous 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 a tibial keel extending distally from the distal surface to define a longitudinal tibial keel axis.

[0007] In some aspects, the technology described herein relates to a tibial prosthesis as described above, optionally further including a plurality of fins spanning the bifurcation between the tibial keel and the distal face.

[0008] In some aspects, the technology described herein relates to a tibial prosthesis as described above, optionally including the plurality of fins being angled anterior-posterior and medial-lateral to form flutes in the posterior portion of the tibial keel.

[0009] In some aspects, the technology described herein relates to a tibial prosthesis as described above, optionally including the tibial keel including second and third flutes each extending to a distal tip of the tibial keel, the second and third flutes being joined by an anterior fin at the anterior portion of the tibial keel.

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

[0011] In some aspects, the technology described herein relates to a tibial prosthesis as described above, optionally including the plurality of pegs including four pegs positioned adjacent the posterior-medial corner, the posterior-lateral corner, the anterior-lateral corner, and the anterior-medial corner of the periphery, respectively.

[0012] In some aspects, the technology described herein relates to a tibial prosthesis as described above, optionally including the plurality of pegs being one of square or rectangular in cross section and configured to be press-fit into a round hole drilled into the tibia.

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

[0014] In some aspects, the technology described herein relates to a tibial prosthesis as described above, optionally including one or more surfaces of at least one of the tibial keel or fins being fabricated to be smoother than the distal surface to inhibit bony ingrowth.

[0015] In some aspects, the technology described herein provides a tibial prosthesis system optionally including a plurality of prostheses, each of the plurality of prostheses including a baseplate having a distal surface sized and shaped to substantially cover a proximal resected surface of the tibia, a proximal surface opposite the distal surface, the proximal surface having a lateral section and a medial section opposite the lateral section, a periphery extending between the distal and proximal surfaces, and a plurality of pegs extending distally from the distal surface, and a tibial keel extending distally from the distal surface to a dome-shaped 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 in stages with increasing sizes of the plurality of prostheses relative to the distal surface, the proximal surface, and the periphery.

[0016] In some aspects, the technology described herein relates to a system as described above, optionally further including a plurality of fins spanning the bifurcation between the tibial keel and the distal face.

[0017] In some aspects, the technology described herein relates to a system as described above, further comprising 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 non-porous or relatively non-porous material forming the base, optionally including the plurality of pegs being formed from both the porous material and the non-porous or relatively non-porous material.

[0018] In some aspects, the technology described herein relates to a system as described above, optionally including the tibial keel including a first flute on the posterior side formed between multiple fins added to the tibial keel, and the tibial keel including 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 an anterior fin at the anterior of the tibial keel.

[0019] In some aspects, the technology described herein relates to a system as described above, optionally including a second layer of non-porous 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.

[0020] In some aspects, the technology described herein relates to a system as described above, optionally including one or more surfaces of at least one of the tibial keel or fins being fabricated to be smoother than the distal surface to inhibit bony ingrowth.

[0021] In some aspects, the technology described herein involves providing a first tibial prosthesis, optionally including: a first proximal surface; a first distal surface opposite the first proximal surface, the first distal surface being sized and shaped to substantially cover a proximal resected 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 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 a second tibial prosthesis, optionally including: a first proximal surface; a first distal surface opposite the first proximal surface, the first distal surface being sized and shaped to substantially cover a proximal resected 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 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 including: a first surface; a second distal surface opposite the second proximal surface, the second distal surface being sized and shaped to substantially cover the proximal resected 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 bifurcation between the second keel and the second distal surface, wherein the first keel and the first plurality of fins share substantially the same geometry as the second keel and the second plurality of fins.

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

[0023] In some aspects, the technology described herein relates to a system as described above, optionally including: a first plurality of fins angled in the anterior-posterior and medial-lateral directions to form first flutes in the posterior portion of the first tibial keel; a second plurality of fins angled in the anterior-posterior and medial-lateral directions to form first flutes in the posterior portion of the second tibial keel; and the first flutes of the first tibial prosthesis and the second tibial prosthesis having substantially the same angle.

[0024] In some aspects, the technology described herein relates to a system as described above, optionally including wherein the first plurality of fins is relatively thinner than the second plurality of fins.

[0025] In some aspects, the technology described herein relates to a system as described above, optionally including: the first tibial keel includes second flutes and third flutes, each extending to a distal tip of the first tibial keel; and the second tibial keel includes second flutes and third flutes, each extending to a distal tip of the tibial keel; and the second and third flutes of the first tibial keel share substantially the same geometry as the second and third flutes of the second tibial keel.

[0026] In the drawings, which are not necessarily to scale, like reference numerals may represent like components in different drawings. Like reference numerals with different subscripts may represent various different instances of like components. The drawings generally illustrate, by way of example, but in no way by way of limitation, various embodiments discussed herein. [Brief explanation of the drawings]

[0027] [Figure 1A-B] 1A and 1B show various plan views of a tibial baseplate according to one embodiment of the present application. [Figure 1C-D] 1C and 1D show various plan views of a tibial baseplate according to one embodiment of the present application. [Figure 1E-H] FIG. 1E shows various plan views of a tibial baseplate according to one embodiment of the present application, and FIGS. 1F-1H show various enlarged and / or cross-sectional views of the tibial baseplate of FIGS. 1A-1E according to one embodiment of the present application. [Figure 1I-L] 1I-1L illustrate various enlarged and / or cross-sectional views of the tibial baseplate of FIGS. 1A-1E according to one embodiment of the present application. [Figure 2] FIG. 2 illustrates a system including multiple tibial baseplates having keels of various different proximal-distal lengths, according to one embodiment of the present application. [Figure 2A] FIG. 2A shows a chart of the proximal-distal length variation of a keel compared to a standard size tibial baseplate, according to one embodiment of the present application. [Figure 3A-B] 3A and 3B illustrate a system that provides various sizes of tibial baseplates, including those configured for both uncemented and cemented fixation to the tibia, which can have the same standard size (for both uncemented and cemented versions) and can share substantially the same distal profile for the keel and multiple fins according to one embodiment of the present application. [Figure 4A-B] 4A and 4B illustrate a system that provides various sizes of tibial baseplates, including those configured for both uncemented and cemented fixation to the tibia, which can have the same standard size (for both uncemented and cemented versions) and can share substantially the same distal profile for the keel and multiple fins according to one embodiment of the present application. [Figure 5A-B]5A and 5B illustrate a system that provides various sizes of tibial baseplates, including those configured for both uncemented and cemented fixation to the tibia, which can have the same standard size (for both uncemented and cemented versions) and can share substantially the same distal profile for the keel and multiple fins according to one embodiment of the present application. [Figure 6A-B] 6A and 6B illustrate a system that provides various sizes of tibial baseplates, including those configured for both uncemented and cemented fixation to the tibia, which can have the same standard size (for both uncemented and cemented versions) and can share substantially the same distal profile for the keel and multiple fins according to one embodiment of the present application. [Figure 7A-B] 7A and 7B illustrate a system that provides various sizes of tibial baseplates, including those configured for both uncemented and cemented fixation to the tibia, which can have the same standard size (for both uncemented and cemented versions) and can share substantially the same distal profile for the keel and multiple fins according to one embodiment of the present application. [Figure 8A-B] 8A and 8B illustrate a system that provides various sizes of tibial baseplates, including those configured for both uncemented and cemented fixation to the tibia, which can have the same standard size (for both uncemented and cemented versions) and can share substantially the same distal profile for the keel and multiple fins according to one embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0028] This application relates to tibial prostheses, and more particularly to tibial baseplates and systems. This application focuses on distal aspects and features of tibial baseplates, as further discussed herein. As previously mentioned, these distal features can improve fixation and durability of the tibial baseplate, among other benefits.

[0029] The terms "proximal" and "distal" as used herein should be given their commonly understood anatomical interpretation. The term "proximal" means generally a direction toward the patient's torso, and the term "distal" means the opposite direction from proximal, i.e., a direction away from the patient's torso. Of course, 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 typically used with the knee flexed. 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 commonly understood anatomical interpretation. Thus, "posterior" means the back side of the patient, e.g., the back of the knee. Similarly, "anterior" means the front side of the patient, e.g., the front of the knee. Thus, "posterior" means the opposite direction from "anterior." Similarly, the term "lateral" means the opposite direction from "medial." The term "medial-lateral" means from medial to lateral or from lateral to medial. The term "proximal-distal" means from proximal to distal or from distal to proximal. The term "anterior-posterior" means from anterior to posterior or from posterior to anterior.

[0030] As used herein, the "periphery" of a tibial prosthesis refers to any periphery when viewed from a top view, e.g., in a generally lateral anatomical plane. Alternatively, the periphery of a tibial prosthesis can refer to any periphery when viewed from a bottom view, e.g., in a generally lateral plane, and when viewed from a distal surface configured to contact the resected proximal surface of the tibia. In the context of prostheses such as the tibial baseplates described below, a "home axis" refers to an axis oriented relative to the baseplate such that, after implantation of the baseplate in the proper rotational and spatial orientation, the baseplate home axis of the baseplate aligns with the home axis of the tibia. In some baseplate designs, including those exemplified herein, the home axis bisects the PCL notch at the posterior edge of the tibial plateau periphery and bisects the anterior edge at the anterior edge of the tibial plateau periphery. It is contemplated that the home axis may be oriented relative to other baseplate mechanisms, and it is understood that proper alignment and orientation of the baseplate on the tibia involves positioning the home axis of the baseplate so that it coincides with the home axis of the tibia.

[0031] The home axis of a tibial baseplate may be the anterior-posterior axis, since the home axis extends generally anterior and posterior when the baseplate is implanted on the tibia. The tibial baseplate also defines a medial-lateral axis that lies along the longest line contained within the periphery that is perpendicular to the home axis of the baseplate. As described below, the home axis and the medial-lateral axis cooperate to define a coordinate system useful for quantifying certain baseplate features according to the present disclosure. Additionally, distal features, such as a keel and one or more fins, may be aligned with the anterior-posterior axis, the medial-lateral axis, or other axes, such as an axis of symmetry or a proximal-distal axis.

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

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

[0034] The tibial baseplate 100 can have a particular asymmetry relative to the home axis and the anterior-posterior axis AP. Such a shape is designed to maximize tibial coverage for the majority of potential knee replacements, as discussed in various prior applications by the applicant, including U.S. Patent Application Publication Nos. 2013 / 0024001 A1 and 2013 / 0131820 A1, the entire specifications of which are incorporated herein by reference. Maximized cortical bone coverage facilitates superior support for the tibial baseplate 100. Large-area contact between the cortical and cancellous bone of the tibia facilitates firm and durable fixation of the tibial baseplate 100 to the tibia.

[0035] The anterior-posterior axis AP may divide the tibial baseplate 100 into a medial section 114 and a lateral section 116. The medial section 114 may be asymmetrically shaped and sized relative to the lateral section 116 defined along the periphery 106. The periphery 106 may be shaped as a wall and may have a linkage 112 along one or more selected points.

[0036] The tibial baseplate 100 is available in several standard sizes. These standard sizes are selected to allow coverage for various sizes of tibias. By way of example, the tibial baseplate 100 may include nine sizes ranging from size 1 (short stature) to size 9 (tall stature). The various sizes are available to the surgeon as a system to facilitate proper size selection. The standard sizes have different geometries along the proximal side (e.g., periphery 106, proximal surface 102, etc.) and distal side (e.g., distal surface 104, keel 108, and fins 110A and 110B, etc.), as further described herein.

[0037] 1B-1E show additional plan views of the tibial baseplate 100 from various sides. FIG. 1B shows the keel 108 and one of the 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 fins 110A and / or 110B can be part of the keel 108 assembly, but are described here as separate features from the remainder of the keel 108, including the stem feature. The keel 108 can form an angle θ with 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 FIG. 1B, the angle θ can be approximately 90 degrees. The axis of symmetry S1 of the keel 108 can be a proximal-distal axis.

[0038] FIG. 1B illustrates that the keel 108 can include a stem feature having a distal tip 118. The distal tip 118 can be shaped for insertion into the tibial canal. Accordingly, the distal tip 118 can be shaped, for example, as a dome, hemisphere, or other shape that is shaped to eliminate sharp edges. The surfaces forming the distal tip 118 can be shaped to form an angle α of 30 to 70 degrees (in some embodiments, approximately 50 degrees). The surfaces forming the distal tip 118 can be curved, for example, with a radius of curvature of 3 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, an apex. It should be noted that the keel 108 with the distal tip 118 is not configured to couple with a stem extension or other feature, as is common in some total knee replacement systems. Rather, the keel 108 generally increases in proximal-distal length as the standard size of the tibial baseplate 100 increases.

[0039] 1C and 1D show a keel 108 and multiple fins 110A and 110B extending from the distal surface 104. The fins 110A and 110B can have a symmetrical arrangement and mirror-image geometry relative to each other and to the keels 108 located on opposite inner and outer sides thereof. While two fins 110A and 110B are shown in FIGS. 1C and 1D, three or more fins are contemplated in other embodiments. The keel 108 can include a first groove with first flutes 120A and a second groove with second flutes 120B. The first flutes 120A and second flutes 120B can extend from a few millimeters from the distal surface 104 to a distal tip 118. Thus, the first flutes 120A and the second flutes 120B can extend across a majority of the proximal-distal length of the keel 108 (e.g., 50% to 95% of the length). The first flutes 120A and the second flutes 120B can be positioned toward the front of the keel 108, generally facing forward. The first flutes 120A and the second flutes 120B can be shaped symmetrically relative to one another. The geometry of the first flutes 120A and the second flutes 120B is discussed further below.

[0040] The keel 108 and fins 110A and 110B may additionally define third flutes 120C ( FIG. 1D ) or recessed areas along the posterior sides of the keel 108 and fins 110A and 110B. The third flutes 120C may be defined primarily by the fins 110A and 110B, which may be angled relative to one another to define an angle β. In particular, the fins 110A and 110B may extend not only in a proximal-distal direction (as the keel 108, in some embodiments), but also in a medial-lateral and anterior-posterior direction. The angle β may be, for example, approximately 105 to 140 degrees. According to one embodiment, the angle β may be approximately 126 degrees. The fins 110A and 110B may have a radius of curvature relative to the keel 108 along their posterior sides. This radius of curvature may be approximately 5 to 10 mm. According to one embodiment, the radius of curvature may be approximately 7.6 mm. The thickness T (FIG. 1D) of the fins 110A and 110B can vary as desired, but may be relatively thicker for a non-cemented prosthesis of the same stock size compared to a cemented prosthesis. Note that thickness T varies as you move proximally-distally along the fins 110A and 110B. However, thickness T of a non-cemented prosthesis of the same stock size may be relatively thicker than the thickness of a cemented prosthesis at the same proximal-distal location.

[0041] The distal surface 104 and other features, such as the window 126 in FIGS. 1E-1G, are described next. These features can be formed from porous or highly porous materials that promote bone ingrowth. For example, the distal surface and window 126 can be constructed from or coated with highly porous biomaterials. Highly porous materials are useful as bone substitutes and as materials receptive to cells and tissue. The porosity of highly porous biomaterials can be as low as 30%, 55%, or as high as 70%, 80%, 85%, or 90%. The average pore size of highly porous biomaterials can be, for example, 100 microns to 1000 microns.

[0042] One example of such a porous or highly porous material is OsseoTi®, publicly available from Zimmer Biomet Inc., Warsaw, Indiana. The material can include titanium or a titanium alloy, as well as 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, highly corrosion resistant, and includes a highly interconnected pore architecture that mimics the porous structure of human cancellous bone, which may enhance bone integration and ingrowth. The porous or highly porous material can be fabricated to be layered or structured with / onto a relatively non-porous or non-porous biocompatible material, such as titanium, titanium alloys, 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., Warsaw, Indiana. Such materials may be formed from a reticulated vitreous carbon foam substrate by infiltrating and coating the substrate with a biocompatible metal, such as tantalum, via a chemical vapor deposition (CVD) process, as disclosed in detail in U.S. Patent No. 5,282,861 to Kaplan, the entire disclosure of which is expressly incorporated herein by reference. In addition to tantalum, other metals, such as niobium, or alloys of tantalum and niobium with each other or with other metals, may also be used. Porous tantalum structures may be formed in a variety of densities to selectively tailor the structure for specific applications. In particular, as discussed in the above-incorporated U.S. Pat. No. 5,282,861, porous tantalum may be fabricated to virtually any desired porosity and pore size and may be matched to the surrounding natural bone to provide an improved matrix for bone ingrowth and mineralization.

[0044] Generally, contemplated porous material structures can include multiple ligaments defining open spaces therebetween, with each ligament generally comprising a core covered by a thin metal film. The open spaces between the ligaments form a matrix of continuous channels with no dead ends, so as not to inhibit cancellous bone growth through the porous tantalum structure. Porous or highly porous materials may contain up to 70%, 85%, or more void space. Thus, porous or highly porous materials are lightweight, strong, porous structures with a substantially uniform and consistent composition, closely resembling the structure of natural cancellous bone. This provides a matrix into which cancellous bone can grow, enabling fixation of the tibial baseplate 100 to the patient's bone.

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

[0046] According to one embodiment, the proximal-distal length (depth) of pegs 122A, 122B, 122C, and 122D may be 7.5 mm to 12.5 mm. Pegs 122A, 122B, 122C, and 122D may be positioned asymmetrically with respect to keel 108, fins 110A, 110B, rim 106, anterior-posterior axis AP ( FIG. 1A ), and / or medial-lateral axis. Pegs 122A, 122B, 122C, and 122D may be positioned within 15 mm or less of rim 106. In particular, pegs 122A, 122B, 122C, and 122D may be positioned adjacent (within 12 mm or less) the anterior-medial, posterior-medial, posterior-lateral, and anterior-lateral corners of rim 106, respectively. Similarly, pegs 122A, 122B, 122C, and 122D can be positioned within 10 mm or less of each of fins 110A, 110B. Pegs 122A, 122B, 122C, and 122D can be oriented at approximately 90 degrees or another angle relative to distal face 104.

[0047] Reference features 124A, 124B, 124C, 124D, 124E, and 124F can include circular, cylindrical, or other shaped features in a base made of a relatively non-porous or non-porous biocompatible material. Reference features 124A, 124B, 124C, 124D, 124E, and 124F protrude 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 baseplate 100. Reference features 124A, 124B, 124C, 124D, 124E, and 124F are relatively small, on the order of 0.5 mm to 2.0 mm in diameter. Because at least a majority (and preferably a greater portion) of the distal surface 104 may be made of 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, reference features 124A, 124B, 124C, 124D, 124E, and 124F formed from a relatively non-porous or non-porous biocompatible material may be utilized. Reference features 124A, 124B, 124C, 124D, 124E, and 124F may be positioned at various locations and protrude into distal surface 104 at various locations. By measuring reference features 124A, 124B, 124C, 124D, 124E, and 124F at various locations on distal surface 104, it may be determined whether distal surface 104 has a desired overall flatness or angulation.

[0048] FIG. 1E shows a plan view of the tibial baseplate 100 from the posterior-medial or posterior-lateral side, illustrating both the fins 110A and 110B. FIG. 1E also shows the windows 126. The windows 126 may be formed, for example, in the fins 110A, 110B, the keel 108, and / or the pegs 122A, 122B, 122C, and 122D. The windows 126 may be formed from the same porous or highly porous material or may be formed similarly to at least a majority of the distal surface 104.

[0049] FIG. 1F is an enlarged view of a portion of fin 110A, showing one of windows 126. Window 126 can have an elongated medial-lateral width relative to its proximal-distal depth. The medial-lateral width can be, for example, 5 mm to 10 mm. According to one embodiment, the medial-lateral width can be approximately 6 mm. According to one embodiment, the proximal-distal depth can be 1.7 mm. The edge of window 126 can be approximately 3.5 mm to 6.5 mm from the distal edge of fin 110A.

[0050] FIG. 1G illustrates 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 form part of the fin 110. The window 126 can be positioned adjacent to (distal to) the distal surface 104, defined within the area shown by the porous or highly porous material 128. In particular, the distal portion and a majority of the fin 110A along its distal surface can be constructed from a relatively non-porous or non-porous biocompatible material. Indeed, 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 (e.g., as-printed, machined, dry-blasted, etc.) to have a relatively smoother surface finish (e.g., less than 8.0 microns Ra) than the surface finish of the distal surface 104 or other portions of the tibial baseplate 100. Such a relatively smooth surface finish, as compared to distal surface 104 and window 126 formed of porous or highly porous material 128, can inhibit bone ingrowth or overgrowth on the distal portions / surfaces of fins 110A, 110B, keel 108 and / or pegs. However, the surface finish of fins 110A and / or 110B and / or keel 108 is not contemplated in some embodiments.

[0051] FIG. 1H shows a cross-section of the tibial baseplate 100, including the distal surface 104, pegs 122A and 122B, reference features 124A, 124B, and 124C, window 126, base B, and 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 can be pyramidal and angled at approximately 30 degrees relative to their axis of symmetry. Thus, the pegs 122A and 122B can form an angle θ with respect to opposite sides of the distal end 130. The angle θ can be, for example, approximately 60 degrees. The distal end 130 can have a blunt tip 132, for example, less than 1.0 mm in a major dimension.

[0052] 1H, the porous or highly porous material 128 may not extend completely through the pegs 122A and 122B at the windows 126, but may cover the proximal base portions 134 of the pegs 122A and 122B to a depth of 0.25 mm to 1.5 mm. In particular, the majority of the pegs 122A and 122B along their distal portions, distal ends 130 and distal faces may be constructed from a relatively non-porous or non-porous biocompatible material.

[0053] FIGS. 1I through 1K show cross-sectional views of the keel 108 and fins 110A and 110B, illustrating features such as the first flute 120A, second flute 120B, and third flute 120C. As shown in FIGS. 1I through 1K, the keel and fins 110A and 110B may taper from adjacent the distal surface toward the distal tip. The first flute 120A and the second flute 120B may be separated by a front fin 140. The front fin 140 may form the forward-most portion of the keel 108 and may have a substantially uniform width across at least a majority of the proximal-distal length of the keel 108. The width of the front fin 140 may be on the order of 1 mm to about 3 mm, for example, across a majority of its longitudinal length. The width of the front fin 140 may increase adjacent the proximal portion of the keel 108 shown in FIG. 1I. The first flutes 120A can have an angle θ1 of about 100 degrees to about 140 degrees. According to one embodiment, the angle θ1 can be about 117 degrees. Similarly, the second flutes 120B can have an angle θ1 of about 100 degrees to about 140 degrees. According to one embodiment, the angle θ1 can be about 117 degrees. The keel 108 can be untapered and can be substantially untapered along at least a majority or more of its proximal-distal length. The fins 110A and 110B can be tapered as described above.

[0054] The fins 110A and 110B can be monolithically or integrally formed with the remainder of the tibial baseplate 100, including the distal surface 104 and the keel 108. Thus, the fins 110A and 110B can be features of the keel 108 described above. However, it is contemplated that the fins 110A and 110B can be separately attached to other features of the tibial baseplate 100. Alternatively, the fins 110A and 110B can be monolithically formed together as a single piece and separately connected to the keel 108 or distal surface 104. The keel 108 and / or fins 110A and 110B can be formed (with or without each other, and with or without the remainder of the tibial baseplate 100) by an additive manufacturing process, such as laser sintering or the like.

[0055] Similarly, with reference to FIG. 1H, features such as pegs 122A, 122B, reference features 124A, 124B and 124C, window 126 and porous or highly porous material 128 can be monolithically or integrally formed with base B, such as by an additive manufacturing process or other process.

[0056] 1H. The reference feature 124A can have a distal end that forms a portion of the distal surface 104. The reference feature 124A can extend generally distally from the base B and can be formed from a similar or identical material to the base B, such as a relatively non-porous or non-porous biocompatible material 150. The 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 feature 124A can extend through the first layer 152 and can form at least a portion of the distal surface 104.

[0058] 2 shows a system 200 including various sizes of tibial baseplates 100A, 100B, and 100C. Tibial baseplate 100A can be a standard size 1 configured for patients with knees corresponding to short stature. Tibial baseplate 100B can be a standard size 5 configured for patients with knees corresponding to medium stature. Tibial baseplate 100C can be a standard size 8 configured for patients with knees corresponding to tall stature. Tibial baseplates 100A, 100B, and 100C can be configured to provide a desired amount of coverage to the resected tibia without overhang or other undesirable mounting arrangements. Tibial baseplates 100A, 100B, and 100C may differ with respect to dimensions such as medial-lateral extension (e.g., measured from the first medial-most edge of the periphery to the second lateral-most edge) and anterior-posterior extension (e.g., measured from the third anterior-most edge of the periphery to the fourth posterior-most edge). However, the medial-lateral width W1 of tibial baseplate 100A may vary from that of tibial baseplate 100B or tibial baseplate 100C by, for example, 20 mm or less. Thus, the medial-lateral width W1 may not increase with standard size changes in a commiserate manner with other dimensions (e.g., medial-lateral extension of the periphery, anterior-posterior extension of the periphery). The proximal-distal length L1 of tibial baseplate 100A may vary from that of tibial baseplate 100B or tibial baseplate 100C only by a substantial amount, for example, as shown in FIGS. 2 and 2A.

[0059] FIG. 2 illustrates that the tibial baseplates 100A, 100B, and 100C are not all stemmable in structure (although stemmable structures are also contemplated). Therefore, the proximal-distal length of the keel 108A generally increases with increasing standard size. Therefore, the proximal-distal length of the keel 108A of the tibial baseplate 100A is relatively shorter than that of the keels 108B and 108C. FIG. 2A illustrates that two or more different standard sizes may each share the same proximal-distal length, thereby allowing the proximal-distal length of the keel 108A to increase in stages. In other words, the proximal-distal length does not increase linearly with increasing standard size, but rather increases in stages. Therefore, at least two of the standard sizes (and possibly up to four of the standard sizes) share the same proximal-distal length.

[0060] Exemplary keel lengths per standard size are provided in FIG. 2A . Note that the keel length does not transition smoothly in a straight line, but rather has a step function, such that some sizes (e.g., from size 1 to size 2, size 3 to size 6, and size 7 to size 9) may share substantially the same proximal-distal length. However, the general trend indicated by the best-fit curves is a linear increase in the proximal-distal length of the keel with size change. Note that other features discussed herein, such as flute angle, flute radius, flute medial-lateral width, anterior fin size (medial-lateral width), and / or fin radius, posterior flute angle (e.g., angle between fins), and distal tip of the keel geometry, may remain substantially constant in geometry as the standard size changes. Thus, for example, a standard size 1 tibial baseplate 100A would have an anterior groove of the same size (medial-lateral) as a standard size 8 tibial baseplate 100C (see FIG. 2 ).

[0061] 3A-8B illustrate another embodiment of a tibial baseplate system 300. In particular, system 300 includes, for example, tibial baseplate 100D (FIGS. 3A and 3B), tibial baseplate 100E (FIGS. 4A and 4B), tibial baseplate 100F (FIGS. 5A and 5B), tibial baseplate 100G (FIGS. 6A and 6B), tibial baseplate 100H (FIGS. 7A and 7B), and tibial baseplate 100I (FIGS. 8A and 8B).

[0062] Tibial baseplates 100D and 100E may be the same standard size (e.g., standard size 2) but may have a different structure in that tibial baseplate 100D is configured for uncemented fixation (rather utilizing bone ingrowth) compared to tibial baseplate 100E, which is configured for cemented fixation. Similarly, tibial baseplates 100F and 100G may be the same standard size (e.g., standard size 4) but may have a different structure in that tibial baseplate 100F is configured for uncemented fixation (rather utilizing bone ingrowth) compared to tibial baseplate 100G, which is configured for cemented fixation. Tibial baseplates 100H and 100I may be the same standard size (e.g., standard size 7) but may have a different structure in that tibial baseplate 100H is configured for uncemented fixation (rather utilizing bone ingrowth) compared to tibial baseplate 100I, which is configured for cemented fixation.

[0063] Tibial baseplates 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 features of tibial baseplates 100D and 100E can also be substantially the same. This includes the geometry of aspects of the keel 108D and fins 110D, 110DD of tibial baseplate 100D as compared to corresponding aspects of the keel 108E and fins 110E, 110EE of tibial baseplate 100E. 3A-4B, the keel 108D and fins 110D, 110DD of the tibial baseplate 100D can share substantially the same distal profile 302 (measured along the distal-most surface of the keel 108D and fins 110D, 110DD moving in a medial-lateral direction along the extent of the keel 108D and fins 110D, 110DD) as the keel 108E and fins 110E, 110EE of the tibial baseplate 100E. In other words, the keels 108D and 108E can share the same geometric characteristics, 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.) as the fins 110E, 110EE. This substantial geometric match between the keel 108D and fins 110D, 110DD and the keel 108E and fins 110E, 110EE allows the surgeon to select between a cemented or uncemented device during surgery. This eliminates the need for reaming or other surgical procedures that would otherwise be required to convert from a cemented device to a uncemented device (or vice versa), reducing time and complexity. According to some embodiments, the fins 110D, 110DD and 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 tibial baseplates 100D and 100E, tibial baseplates 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 features of tibial baseplates 100F and 100G can also be substantially the same. This includes the geometry of several aspects of the keel 108F and fins 110F, 110FF of tibial baseplate 100F when compared to corresponding aspects of the keel 108G and fins 110G, 110GG of tibial baseplate 100G. 5A-6B, the keel 108F and fins 110F, 110FF of the tibial baseplate 100F can share substantially the same distal profile 304 (measured along the distal-most surface of the keel 108F and fins 110F, 110FF moving in a medial-lateral direction along the extent of the keel 108F and fins 110F, 110FF) as the keel 108G and fins 110G, 110GG of the tibial baseplate 100G. In other words, the keels 108F and 108G can share the same geometric characteristics, such as, but not limited to, proximal-distal length, diameter, groove shape and size, flute size and shape, etc. Similarly, the fins 110F, 110FF can share the same geometry (angle, medial-lateral width, proximal-distal length, thickness, etc.) as the 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] Tibial baseplates 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 distal features of tibial baseplates 100H and 100I can also be substantially the same. This includes the geometry of aspects of the keel 108H and fins 110H, 110HH of tibial baseplate 100H when compared to corresponding aspects of the keel 108I and fins 110I, 110II of tibial baseplate 100I. 7A-8B, the keel 108H and fins 110H, 110HH of the tibial baseplate 100H can share substantially the same distal profile 306 (measured along the distal-most surface of the keel 108H and fins 110H, 110HH moving in a medial-lateral direction along the extent of the keel 108H and fins 110H, 110HH) as the keel 108I and fins 110I, 110II of the tibial baseplate 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 (angulation, medial-lateral width, proximal-distal length, thickness, etc.) as the fins 110I, 110II. According to some embodiments, the fins 110H, 110HH may differ from the fins 110I, 110II 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 herein, the tibial baseplate can include a cruciate retaining (CR) design. Therefore, the tibial baseplate can have relief for the posterior cruciate ligament, which 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 constrained posterior stabilized (CPS) design, and an ultra-congruent (UC) design. The PS and MLC designs utilize spines and cams, as known to those skilled in the art. Because the posterior cruciate ligament is eliminated, no relief is required.

[0067] Additional notes The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as "embodiments." Such embodiments may include elements in addition to those shown or described. However, the inventors also contemplate embodiments in which only the elements shown or described are provided. Furthermore, the inventors also contemplate embodiments using combinations or substitutions of the illustrated and described elements (or one or more aspects thereof) with respect to the specific embodiment (or one or more aspects thereof) shown or described, or with respect to other embodiments (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," as common in patent documents, are used to include one or more than one, independent of any other instance or use of "at least one" or "one or more." In this document, the term "or" means a non-exclusive or, whereby "A or B" is used to include "A but not B," "B but not A," and "A and B," unless otherwise specified. In this document, the terms "including" and "in which" are used as plain English equivalents of the terms "comprising" and "wherein," respectively. Also, in the claims below, the terms "including" and "comprising" are open-ended, i.e., systems, devices, articles, compositions, formulations, or processes that include 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. Furthermore, in the claims below, the terms "first," "second," "third," etc. are used merely as labels and do not impose numerical requirements on their objects.

[0069] The above description is intended to be illustrative, not limiting. For example, the above embodiments (or one or more aspects thereof) can be used in combination with each other. Other embodiments can be used, for example, by those skilled in the art, upon review of the above description. The Abstract is provided to comply with 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. Furthermore, the grouping of various features in the above Detailed Description serves to simplify the disclosure. This should not be construed as intending that a non-claimed feature is essential to any claim. Rather, inventive subject matter lies in less than all features of a particular disclosed embodiment. Accordingly, the following claims are herein incorporated 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 range of equivalents to which such claims are entitled. According to aspect (1), there is provided a tibial prosthesis for knee arthroplasty, comprising: A base plate, a distal surface sized and shaped to substantially cover the proximal resected surface of the tibia; a proximal surface opposite the distal surface, the proximal surface having an outer section and an inner section opposite the outer section; 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 base plate including a second layer of non-porous 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 a tibial keel extending distally from the distal surface to define a longitudinal tibial keel axis; A tibial prosthesis for knee arthroplasty comprising: According to aspect (2), the prosthesis further includes a plurality of fins spanning the bifurcation point between the tibial keel and the distal surface. According to aspect (3), the fins are angled in the anterior-posterior and medial-lateral directions to form flutes on the posterior portion of the tibial keel. According to aspect (4), the tibial keel has second and third flutes each extending to the distal tip of the tibial keel, and the second and third flutes are connected by an anterior fin at the anterior portion of the tibial keel. According to aspect (5), the device further comprises a plurality of pegs extending distally from the distal surface, and one or both of the plurality of pegs or the plurality of fins have windows formed from a porous material. According to aspect (6), the plurality of pegs includes four pegs positioned adjacent to a rear-medial corner, a rear-lateral corner, an anterior-lateral corner, and an anterior-medial corner of the peripheral edge, respectively. According to aspect (7), the plurality of pegs have a cross section that is one of square and rectangular, and are configured to be press-fit into a round hole drilled in the tibia. According to aspect (8), the window extends completely through at least one of the plurality of fins. According to aspect (9), one or more surfaces of the tibial keel or at least one of the plurality of fins are fabricated to be smoother than the distal surface to inhibit bone ingrowth. According to aspect (10), there is provided a tibial prosthesis system, comprising: A plurality of prostheses, each of the plurality of prostheses comprising: A base plate, a distal surface sized and shaped to substantially cover the proximal resected surface of the tibia; a proximal surface opposite the distal surface, the proximal surface having an outer section and an inner section opposite the outer section; a periphery extending between the distal surface and the proximal surface; and a plurality of pegs extending distally from the distal face; Equipped with a base plate, wherein each of the plurality of prostheses has a different size relative to the distal surface, the proximal surface, and the periphery; a tibial keel extending distally from the distal surface to a dome-shaped distal tip, the tibial keel having an elongated length measured in a proximal-distal direction and defining a longitudinal tibial keel axis extending along the elongated length, the elongated length increasing in stages with increasing sizes of the plurality of prostheses relative to the distal surface, the proximal surface, and the periphery; A tibial prosthesis system comprising: According to aspect (11), the prosthesis further includes a plurality of fins spanning a bifurcation point between the tibial keel and the distal surface. According to aspect (12), a first layer of porous material forming at least a majority of the distal surface and extending to the periphery; a second layer of non-porous or relatively non-porous material forming the base; The pegs are formed from both the porous material and the non-porous or relatively non-porous material. According to aspect (13), the tibial keel includes, in addition to the tibial keel, a first flute on the posterior side formed between the multiple 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 connected by an anterior fin at the anterior part of the tibial keel. According to aspect (14), the second layer of non-porous or relatively non-porous material has a plurality of reference features extending through the first layer, the plurality of reference features forming at least a portion of the distal surface. According to aspect (15), one or more surfaces of the tibial keel or at least one of the plurality of fins are fabricated to be smoother than the distal surface to inhibit bone ingrowth. According to aspect (16), there is provided a tibial prosthesis system, comprising: 1. A first tibial prosthesis, comprising: a first proximal surface; and a first distal surface opposite the first proximal surface, the first distal surface being sized and shaped to substantially cover the proximal resected surface of the tibia; at least one pocket formed in the first tibial prosthesis and recessed from the first distal surface, the at least one pocket configured to receive bone cement; a first keel extending distally from the first distal surface; a first plurality of fins spanning a bifurcation between the first keel and the first distal surface; a first tibial prosthesis comprising: a second tibial prosthesis, a second proximal surface; and a second distal surface opposite the second proximal surface, the second distal surface being sized and shaped to substantially cover the proximal resected 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; a second plurality of fins spanning a bifurcation between the second keel and the second distal surface; a second tibial prosthesis comprising: Equipped with The first keel and the first plurality of fins share substantially the same geometry as the second keel and the second plurality of fins. According to aspect (17), the substantially same geometry includes at least two of an elongate length measured in a proximal-distal direction, a distal end profile, and a medial-lateral width. According to aspect (18), the first plurality of fins are angled in the anterior-posterior direction and medial-lateral direction to form first flutes on the posterior portion of the first tibial keel, and the second plurality of fins are angled in the anterior-posterior direction and medial-lateral direction to form first flutes on the posterior portion of the second tibial keel, and the first flutes of the first tibial prosthesis and the first flutes of the second tibial prosthesis have substantially the same angle. According to aspect (19), the first plurality of fins are relatively thinner than the second plurality of fins. According to aspect (20), the first tibial keel includes second flutes and third flutes each extending to the distal tip of the first tibial keel, the second tibial keel includes second flutes and third flutes each extending to the distal tip of the tibial keel, and the second flutes and third flutes of the first tibial keel share substantially the same geometry as the second flutes and third flutes of the second tibial keel.

Claims

1. 1. A tibial prosthesis for knee arthroplasty, comprising: A base plate, a flat-shaped distal surface sized to substantially cover the proximal resected surface of the tibia; a proximal surface opposite the distal surface, the proximal surface having an outer section and an inner section opposite the outer section; 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 base plate including: a second layer of non-porous or relatively non-porous material extending from the second layer through the first layer and having a plurality of reference features having distal ends, the distal ends of each of the plurality of reference features being flush with and forming at least a portion of the distal surface; a tibial keel extending distally from the distal surface to define a longitudinal tibial keel axis; a plurality of fins spanning a bifurcation between the tibial keel and the distal surface; a plurality of pegs extending distally from the distal face; 1. A tibial prosthesis for knee arthroplasty, comprising:

2. The tibial prosthesis of claim 1 , wherein the plurality of fins are angled in an anterior-posterior direction and a medial-lateral direction to form flutes on the posterior portion of the tibial keel.

3. 3. The tibial prosthesis of claim 2, wherein the tibial keel includes second and third flutes each extending to a distal tip of the tibial keel, the second and third flutes being joined by an anterior fin at an anterior portion of the tibial keel.

4. The tibial prosthesis of claim 1 , wherein one or both of the plurality of pegs and the plurality of fins have windows formed from a porous material.

5. 5. The tibial prosthesis of claim 4, wherein the plurality of pegs comprises four pegs positioned adjacent a posterior-medial corner, a posterior-lateral corner, an anterior-lateral corner, and an anterior-medial corner of the circumferential edge, respectively.

6. The tibial prosthesis of claim 4 , wherein the pegs are square or rectangular in cross section and press fit into round holes drilled into the tibia.

7. The tibial prosthesis of claim 4 , wherein the window extends completely through at least one fin of the plurality of fins.

8. 4. The tibial prosthesis of claim 1, wherein one or more surfaces of one or both of the tibial keel and the plurality of fins are fabricated to be smoother than the distal surface to inhibit bone ingrowth.

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