Low stress all poly tibial component

A tibial component for use in conjunction with a knee replacement surgery. An inferior surface of the tibial component may be concave to thereby improve bonding between the tibial component and a tibia. The tibial component may produce low stress in the cement mantle during in-vivo loading. A stem extending from the inferior surface of the tibial component may include an anterior curvature to facilitate the use of minimally evasive surgical techniques. The stem may further include medial-lateral wing portions with a posterior curvature to provide improved support.

Not Applicable.

BACKGROUND

1. The Field of the Present Disclosure

The present disclosure relates generally to prostheses and more particularly, but not necessarily entirely, to knee joint prostheses and to a method of installing knee joint prostheses during a knee replacement surgery.

2. Description of Related Art

Knee joint replacement surgery involves replacing a knee joint with an artificial knee joint, referred to sometimes herein as a “prosthesis” or “implant.” Artificial knees may comprise a tibial component and a femoral component. To begin a knee joint replacement, a surgeon may make an incision on the front of the knee to allow access to the joint. Several different approaches may be utilized to make the incision. Once the knee joint is opened, the surgeon may prepare the end of the femur bone to receive the femoral component by making one or more cuts to the bone. A cutting guide may be utilized to ensure proper alignment. The femoral component may then be installed onto the end of the femur. The femoral component may replace the bottom surface of the femur bone and the groove where the patella sits.

Next, the surface of the tibia bone may be prepared for receiving the tibial component. In particular, the top of the tibia may be removed by the surgeon leaving a relatively flat surface. The tibial component may include a stem that is then inserted into the tibia. Bone cement may be utilized to secure the tibial component to the tibia. The tibial component may replace the top surface of the tibia bone. The tibial component may include a surface for receiving the femoral component. The surgeon may then close the incision.

Several shortcomings exist for the previously available tibial components. For example, the stem geometry for previously available tibial components have not been overly conducive to minimally invasive surgery (MIS). That is, previously available tibial components included stems that required extensive displacement of tissue during surgery in order to install the stems into the tibia bone. This extensive displacement of tissue led directly to increased patient recovery time.

Another shortcoming of previously available tibial components is that their design could lead to failure of the bond between the tibia component and the tibia. For example, some previously available tibial components included undercut cement grooves and channels that were utilized to anchor the components using bone cement. Disadvantageously, these grooves and channels produced non-uniform stress fields during in-vivo loading that loosened the tibial components from the tibia.

The prior art is thus characterized by several disadvantages that are addressed by the present disclosure. The present disclosure minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.

The features and advantages of the present disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the present disclosure without undue experimentation. The features and advantages of the present disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.

DETAILED DESCRIPTION

It must be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. In describing and claiming the present disclosure, the following terminology will be used in accordance with the definitions set out below. As used herein, the terms “comprising,” “having,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps.

As used herein, the term “anterior” may refer the front plane of the human body, e.g., a patient. Parts of prostheses labeled as “anterior” or “extending anteriorly” means that after implantation, those parts face or extend towards the anterior of the patient. As used herein, the term “posterior” may refer the back plane of the human body, e.g., a patient. Parts of prostheses labeled as “posterior” or “extending posteriorly” means that after implantation, those parts face or extend towards the posterior of the patient.

Applicant has discovered a novel tibial component or prosthesis for use in a knee replacement surgery. An embodiment of the present disclosure may include a tibial component having a unique stem geometry that is conducive to minimally evasive surgery techniques. An embodiment of the present disclosure may include a tibial component having a more uniform stress field during in-vivo loading. An embodiment of the present disclosure may include a tibial component having an improved bond with the tibia.

An embodiment of the present disclosure may include a tibial component having a bearing surface for receiving a femoral component attached to an end of a femur bone, and an inferior surface opposite the bearing surface, and a stem extending downwardly and anteriorly from the inferior surface to a terminal end. An embodiment of the present disclosure may include a tibial component with a stem having an anterior curvature residing in an anterior to posterior plane bisecting the tibial component, where the anterior to posterior plane is perpendicular to the anterior plane and the posterior plane of the patient.

An embodiment of the present disclosure may include a tibial component having a body with a top and a bottom, wherein a bearing surface is formed on the top of the body and an inferior surface is formed on the bottom of the body. An embodiment of the present disclosure may include a tibial component having a bearing surface with a first concave bearing surface and a second concave bearing surface for receiving a pair of condylar articular surfaces of a femoral component or the femoral bone. An embodiment of the present disclosure may include a tibial component comprising a body of unitary construction. An embodiment of the present disclosure may include a tibial component having a stem with a T-shaped cross-section.

An embodiment of the present disclosure may include a tibial component having a stem with a anteriorly facing surface extending between an inferior surface and a terminal end, the anteriorly facing surface may comprise a concave portion, also referred to herein as an “anterior curve forming a concave, anterior-facing space,” also referred to herein as a stem that is “curving anteriorly.” An embodiment of the present disclosure may include a tibial component having a stem extending downwardly from an inferior surface, wherein the stem may comprise a pair of laterally extending wing portions that curve in the posterior direction.

An embodiment of the present disclosure may include a tibial component having an inferior surface with a concave portion. An embodiment of the present disclosure may include a tibial component having an inferior surface with a concave portion, wherein a rim circumscribes the concave surface, or a portion of the concave surface.

An embodiment of the present disclosure may include forming a cavity in a prepared surface of a tibia, wherein the cavity extends downwardly from the prepared surface of the tibia. The cavity may include an anterior curvature. An embodiment of the present disclosure may include forming a convex or conical cement mantel between an inferior surface of a tibial component and a prepared surface of a tibia.

An embodiment of the present disclosure may include an apparatus for forming a cavity in a prepared surface of a tibia. The apparatus may include a block portion that attaches to the anterior of the tibia bone. A pivot arm may be pivotably connected to the block portion. A punch extending from the free end of the pivot arm may form the cavity when the pivot arm is rotated.

Referring now toFIGS. 1A and 1B, there is depicted a front view of a tibial component100according to an embodiment of the present disclosure. The tibial component100may be formed entirely of a plastic, such as polyethylene. In an embodiment, the tibial component100may be formed of any elastohydrodynamic material, including PEEK and polycarbonate urethane (PCU) and hard bearing material such as ceramics and diamond surfaces. In an embodiment of the present disclosure, the tibial component100may be of unitary construction. In an embodiment, the tibial component100may be formed from disparate pieces.

The tibial component100may include a bearing body102having an articulating or bearing surface104and a tibial tray106. The articulating surface104of the tibial component100may be configured for receiving a head of a femoral component (not shown) or the head of a natural femur. In particular, the articulating surface104may comprise a first concave bearing surface104A and a second concave bearing surface104B for receiving artificial, or natural, femur condyles.

In an embodiment of the present disclosure, the articulating surface104may be an ultracongruent bearing surface. The tibial tray106may be bonded with bone cement to a tibial plateau of a tibia that has been previously prepared. (Typically, tibia preparation involves resecting the proximal end of the tibia.)

Extending downwardly from the tibial tray106may be a stem108. As best seen inFIG. 1B, the stem108may include a primary stem portion110and a pair of medial-lateral wing portions112and114. The wing portions112and114may extend laterally on either side of the primary stem portion110. The primary stem portion110may extend a greater distance below the tibial tray106of the tibial component100than the wing portions112and114.

Referring now toFIG. 2, there is depicted a cross-sectional view of the tibial component100taken along the cross-section B-B shown inFIG. 1B, where like reference numerals depict like components. The tibial component100may include an anterior portion116and a posterior portion118separated by a pair of opposing side portions120and122.

As can be observed inFIG. 2, the cross-sectional geometry of the primary stem portion110may include a T-shaped portion123to provide improved torsional resistance when the stem108is implanted into a tibia. (The T-shaped nature of the primary stem portion110can also be observed inFIG. 1B.) That is, the T-shaped cross-section of the primary stem portion110may resist torsional forces exerted on the tibial component100during in-vivo loading.

As can be further observed inFIG. 2, in an embodiment of the present disclosure, the wing portions112and114of the stem108may be arcuate. In particular, the wing portions112and114of the stem108may curve toward the posterior portion118of the tibial component100as they extend laterally away from the primary stem portion110and an anterior-posterior plane121bisecting the component100. In an embodiment of the present disclosure, the wing portions112and114may extend beneath the most concave points of the articulating surface104,104A and104B, to thereby provide optimal support to the knee joint.

In an embodiment of the present disclosure, the wing portions112and114may have a thickness of about 0.118 inches to 0.236 inches (3 mm to 6 mm). In addition, the posterior portion118of the tibial component100may include a cutout124for accommodating tissue, such as a patient's posterior-cruciate ligament (not shown). Thus, the cutout124may reduce the need for tissue resection. In addition, the cutout124may provide a visual observation point for excess cement removal and for bony osteophyte removal, if needed. The wing portions112and114may each include an anterior facing surface142. The anterior facing surfaces142may be convex.

Referring now toFIGS. 1B and 2A, a terminating surface132of the stem108, including the primary stem portion110and the wing portions112and114, may include chamfered portions134and136connecting sides138and140, respectively, to the terminating surface132. The intersection between side138and the chamfered portion134, and the chamfered portion134and terminating surface132may be angular or rounded. The intersection between side140and the chamfered portion136, and the chamfered portion136and terminating surface132may also be angular or rounded. It will be appreciated that the chamfer may reduce the occurrence of cortical bone impingement while maximizing load carrying capacity.

Referring now toFIG. 3, there is depicted a cross-sectional view of the tibial component100taken along the cross-section A-A shown inFIG. 1B, where like reference numerals depict like components. The primary stem portion110may extend downwardly from an inferior surface125of the tibial tray106. A first portion110A of the primary stem portion110may extend relatively straight down from the interior surface125. A second portion110B of the primary stem portion110may follow the first portion110A and terminate at a free end110C.

The second portion110B of the primary stem portion110may include a curvature. In an embodiment of the present disclosure, the second portion110B of the primary stem portion110may curve anteriorly, i.e., towards the anterior portion116of the tibial component100as it extends downwardly. In particular, the second portion110B may comprise an anteriorly facing surface128that may be concave and a posteriorly facing surface130that may be convex. The anterior facing surface128may be referred to herein as an anterior curve forming a concave, anterior-facing space131.

In an embodiment of the present disclosure, a cross-section of the stem108may have an anterior curvature in the anterior-posterior plane121. Thus, it will be appreciated that an embodiment of the present disclosure may comprise a stem having an anteriorly curved stem portion and posteriorly curved medial-lateral wing portions.

The second portion110B of the primary stem portion110may include a radius of curvature indicated by the arrow marked with the reference numeral113. In an embodiment of the present disclosure, the radius of curvature113may be selected from one of 1.131 inches (2.872 cm), 1.167 inches (2.964 cm), 1.202 inches (3.053 cm), 1.246 inches (3.164 cm), 1.291 inches (3.279 cm), 1.336 inches (3.393 cm), and 1.380 inches (3.505 cm). In an embodiment of the present disclosure, the radius of curvature113may be between 0.75 inches and 1.75 inches (1.905 cm and 4.445 cm). In an embodiment of the present disclosure, the radius of curvature113may be between 1.0 inch and 1.4 inches (2.54 cm and 3.556 cm).

The first portion110A of the primary stem portion110may include a length marked with the reference numeral115. In an embodiment of the present disclosure, the length115may be between about 0.25 inches and 0.75 inches (0.635 cm and 1.905 cm). In an embodiment, the length115may be about 0.407 inches (1.033 cm).

In an embodiment of the present disclosure, the primary stem portion110may extend from the inferior surface125to the free end110C at a length indicated by the double arrows indicated by the reference numeral117. In an embodiment of the present disclosure, the length117may be between about 0.6 inches and 1.5 inches (1.524 cm and 3.81 cm). In an embodiment, the length117may be one of 0.755 inches (1.917 cm), 0.798 inches (2.026 cm), 0.842 inches (2.138 cm), 0.895 inches (2.273 cm), 0.948 inches (2.407 cm), 1.001 inches (2.542 cm), and 1.055 inches (2.679 cm). In an embodiment, the length117may be between 0.393 inches and 1.968 inches (1 cm and 5 cm).

In an embodiment of the present disclosure, the primary stem portion110may be offset from an anterior-most edge139of the anterior portion116by a length indicated by the double arrows marked with the reference numeral119. In an embodiment, the length119may be between about 0.5 inches and 1.25 inches (1.27 cm and 3.175 cm). In an embodiment, the length119may be one of 0.647 inches (1.643 cm), 0.683 inches (1.734 cm), 0.718 inches (1.823 cm), 0.763 inches (1.938 cm), 0.807 inches (2.049 cm), 0.852 inches (2.164 cm), and 0.896 inches (2.275 cm).

As can be seen inFIGS. 2 and 3, the inferior surface125may comprise a concave portion127. It will be appreciated that the concave portion127of the inferior surface125may provide an increased bonding area as compared to conventional flat surfaces that are found in previously available tibial components. The concave portion127may form a convex or conical bone cement mantle when the tibial component100is bonded onto a prepared surface of a tibia. The tibial tray106may also include a flat-surface portion or rim126that extends below and around the entire perimeter of the concave portion127of the inferior surface125. The flat-surface portion or rim126may allow cortical coverage with respect to the tibia (not shown) and may be about 0.1 inches (2.6 mm) in width.

The concave portion127varies in height (height variation being an inherent feature of concavity) and may have a largest height which, when measured from the bottom surface of the rim126is indicated by the double arrows marked with the reference numeral129inFIG. 3. In an embodiment, the largest height129of the concave portion127may be between 0.019 inches and 0.196 inches (0.5 mm and 5 mm). Thus, it will be appreciated that a corresponding largest height of the convex or conical bone cement mantle formed under the concave portion127may be referred to as having a thickness of about 0.019 inches and 0.196 inches (0.5 mm and 5 mm).

Referring now toFIGS. 4A-4G, there is depicted a tool and method for installing the tibial component100into a proximal end of a tibia pursuant to an embodiment of the present disclosure. Referring toFIG. 4B, there is depicted a tool198for forming a cavity in a bone. The tool198may include a block portion206and a pivot arm220. The block portion206may be L-shaped and include a first portion206A and a second portion206B. The first portion206A and the second portion206B may form a ninety-degree angle with respect to each other. The first portion206A and the second portion206B of the block portion206may include each include a pair of guide holes215.

The pivot arm220may be L-shaped. The pivot art220may include a first portion220A and a second portion220B. The first portion220A and the second portion220B may form a ninety-degree angle with respect to each other. The second portion220B may include a pair of spaced apart members223. Extending between the spaced apart member223may be a shaft214. Disposed on the first portion220A may be a tool receptacle or socket224for receiving a shaft of a handle. Also disposed on the first portion220A is an impact head222. Extending downward from the first portion220A may be a punch226that corresponds in shape and size to the stem of a tibial component. For example, the punch226may correspond in shape and size to the stem108of the tibial component100. The punch may include an end portion226A that corresponds in shape and size to that of the stem108of the tibial component100. In particular, the end portion226A may include stem portion226B that includes a curvature corresponding to that of the primary stem portion110of the stem108. This means that stem portion226may have an anterior curve forming a concave, anterior-facing space, and may have a radius of curvature of between 0.75 inches and 1.75 inches, and may have a length of curvature of between 0.393 inches and 1.968 inches, and may have an anterior-posterior position of between 0.5 inches and 1.25 inches, and the latter may also be states as follows: the stem may have an anterior surface that is offset from an anterior-most edge of the anterior portion of the tibial component by a length of between 0.5 inches and 1.25 inches. Wing portions226C may also extend laterally from the stem portion226B similar to wings112and114of the stem108. As will be explained in more detail hereinafter, the punch226may be used to form a cavity in a prepared surface of a tibia.

The second portion206B of the pivot block206may include a seat216for receiving the shaft214. A latch218may secure the shaft214in the seat216. With the shaft214secured in the seat216, the pivot arm220may pivotally rotate.

Referring now toFIGS. 4A,4C-4G, a procedure of implanting the tibial component100onto an end of a tibia will be disclosed. Referring toFIG. 4A, a tibia200may first be resected to provide a prepared surface202on the tibial plateau as is known to one having ordinary skill in the art. A template204may then be secured onto the surface202. The template204may indicate the location of the cavity for receiving the stem108of the tibial component100.

The pivot block206may then be installed to an anterior portion208of the tibia200. The pivot block206may be secured to the tibia200using pins or screws210installed into the guide holes215.

As shown inFIGS. 4C and 4D, when the pivot arm220is installed into the pivot block206, a surgeon may form a cavity228in the prepared surface202of the tibial plateau by impacting the impact head222on the pivot arm220with a tool. Optionally, the surgeon may insert a handle230into the tool receptacle224to provide additional stability and leverage. The cavity228is formed as the punch226is rotatably driven into the tibial plateau202by the force of the impact. Because the punch226is mounted to the pivot arm220, it will be appreciated that the punch226is rotatably driven into the prepared surface202along an arcuate path.

As shown inFIGS. 4E-4G, the stem108of the tibial component100may be inserted into the cavity228formed in the tibial plateau202by the punch226. It will be noted that the stem108may be rotatably inserted into the cavity228as shown by the arrow indicated with the reference numeral232. The cavity228may extend from the surface202downwardly, with an anterior curvature.

It will be appreciated that the ability to rotatably install the stem108into the cavity228requires less resection and displacement of surrounding tissue as compared to stems that must be vertically inserted into cavities. Further, as perhaps best seen inFIG. 4F, when installed, the stem108of the tibial component100curves anteriorly, i.e., towards the anterior portion208of the tibia200.

Referring now toFIG. 5, the tibial component100may be secured to the tibia200by bone cement240. In particular, the bone cement240may be applied between the inferior surface125of the tibial tray106of the tibial component100and the prepared surface202. Because of the concave nature of the inferior surface125of the tibial tray106, the cement mantle242may include a top surface that is convex or conical. The concave inferior surface125may produce lower stress in the cement mantle242under in-vivo loading. The bone cement240may also be utilized to secure the stem108into the cavity228.

Those having ordinary skill in the relevant art will appreciate the advantages provide by the features of the present disclosure. For example, it is a feature of the present disclosure to provide a tibial component that provides low stress in the cement mantle during in-vivo loading. Another feature of the present disclosure to provide a tibial component with an anterior curved stem.

In the foregoing Detailed Description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited. Rather, inventive aspects lie in less than all features of a single foregoing disclosed embodiment.