Systems for providing deeper knee flexion capabilities for knee prosthesis patients

1. <u>Field of the Invention</u>

The present invention relates to knee prostheses. In particular, the present invention relates to systems for providing deeper knee flexion, or full functional flexion capabilities, more physiologic load bearing and improved patellar tracking for knee prosthesis patients. Specifically, these improvements include (i) adding more articular surface to the antero-proximal posterior condyles of a femoral component, (ii) modifications to the internal geometry of the femoral component and the associated femoral bone cuts, (iii) asymmetrical tibial components that have an unique articular surface that allows for deeper knee flexion than has previously been available and (iiii) asymmetrical femoral condyles that result in more physiologic loading of the joint and improved patellar tracking.

2. <u>Background and Related Art</u>

Orthopedic surgeons are experiencing a proliferation of knee replacement surgeries. The demand appears driven by the fact that few procedures return as much quality of life as joint replacement.

Moreover, the increased need for knee replacements implicates the need for durable and long lasting artificial knee devices that provide for and allow full, functional flexion. That is, there is a great need for research that provides new medical advances on the overall function and performance of knee prostheses, and improves corresponding surgical materials and technologies related to such devices.

Improvements to knee prostheses correspondingly increase with demand. Thus, currently-available knee prostheses mimic characteristics of the normal knee more than those previously used. Unfortunately, today's knee prostheses still have many shortcomings.

Among the shortcomings is the inability of a knee prosthesis patient to achieve deep knee flexion, also known as full functional flexion. Though some currently available knee prostheses allow for knee flexion (i.e., bending) of more than 130 degrees from full limb extension (zero degrees being when the patient's knee is fully extended and straight); such prostheses and results are uncommon. Full functional or deep knee flexion is where the limb is bent to its maximum extent, which may be with the femur and tibia at an angle to each other of 140 degrees or more, though the actual angle varies from person to person and with body habitus. Full extension is where the leg/limb is straight and the person is in a standing position.

To illustrate the average range in degrees achieved by patients having standard knee prostheses, the following is provided. When a patient's knee or limb is fully extended, the femur and tibia are in the same plane - at zero degrees or up to 5-10 degrees of hyperextension in some individuals. However, once the knee bends, and the distal tibia moves toward the buttocks, the angle increases from zero to 90 degrees for a person sitting in a chair. Furthermore, when the tibia is closest to the femur, and the heel is almost at, if not touching, the buttock, the angle is around 160 degrees or more. Most knee prosthesis patients are unable to achieve the latter position or any position placing the knee joint at angles above 130 degrees.

For many people, such a limb and body position is not often achieved or desired most of the time. However, nearly everyone, at some point in time, whether or not it occurs when a person is getting on and off the ground to play with children, or merely incidental to those living active lifestyles, finds themselves in a position requiring knee flexion greater than 130 degrees. Unfortunately, those with currently-available knee prostheses are unable to participate in any activity requiring greater knee flexion and are thus limited to watching from the sidelines.

In many populations and cultures such a limb/knee and body position is desired and necessary the majority of the time. For instance, in Asian and Indian cultures, full functional flexion and the squatting position is common and performed for relatively long periods of time.

A need, therefore, exists for knee prostheses for those patients and especially for those in cultures where extensive squatting, sitting with knees fully flexed, and/or kneeling when praying or eating is common, to achieve knee flexion greater than presently possible among those who have currently-available knee prostheses.

Thus, while techniques currently exist that relate to knee prostheses, challenges still exist. Accordingly, it would be an improvement in the art to augment or even replace current techniques with other techniques.

<patcit id="pcit0001" dnum="US6190415B"><text>US 6,190,415</text></patcit> discloses a knee prosthesis, including a femoral element, a tibial element and at least one bearing element between the femoral and tibial components. <patcit id="pcit0002" dnum="US6402786B"><text>US 6,402,786</text></patcit> discloses a femoral knee implant, which includes a fourth compartment of articulation.

<u>SUMMARY OF THE INVENTION</u>

In accordance with the present invention there is provided a femoral component according to claim 1.

The present invention relates to knee prostheses. In particular, the present invention relates to systems for providing deeper knee flexion capabilities for knee prosthesis patients, and more particularly, to: (i) providing a greater articular surface area to the femoral component of a knee prosthesis, with either a modification of, or an attachment to the femoral component of a knee prosthesis, which when integrated with a patient's femur and an appropriate tibial component, results in full functional flexion; (ii) providing modifications to the internal geometry of the femoral component and the opposing femoral bone; (iii) providing asymmetrical under surfaces on the tibial component of the knee prosthesis and uniquely-positioned articular surfaces to facilitate full functional flexion; and (iv) asymmetrical femoral condylar surfaces with a lateralized patellar (trochlear) groove to more closely replicate physiologic loading of the knee and to provide better tracking of the patella.

Implementation of the present invention takes place in association with improved knee prostheses that enable knee prosthesis patients to achieve greater deep knee flexion than previously achievable using presently-designed knee prostheses.

In at least some implementations of the present invention, greater deep knee flexion is provided to the knee prosthesis by providing an articular surface on the proximal, anterior surface (or portion) of the posterior condyles of the femur. At least some implementations of the present invention embrace an additional or increased articular surface on the proximal, anterior portion of either or both of the medial or lateral posterior condyles of the femoral component of the prosthesis. Embodiments of the femoral component add increased articular surface area to the proximal end of the posterior condyles of the femoral component in an anterior direction such that when the patient bends his or her knee during deep knee flexion, contact between the femoral component and the tibial component is maintained, and a greater, deeper knee flexion can be achieved.

In at least some examples, greater deep knee flexion can be provided or improved by modifying the tibial articulation, in which the center of the conforming medial tibial articular surface of the tibial component of the prosthesis is moved posterior relative to what is currently available. Additionally, in some such examples, the overall shape of the lateral tibial articular surface is modified.

In at least some examples, greater deep knee flexion can be achieved by providing an asymmetrical femoral component of the prosthesis. The asymmetrical femoral component permits transfer of more than one-half of the force transmitted across the joint to be transmitted to the medial side, as occurs in the normal knee. In some examples, other modifications to the tibial and femoral components of a knee prosthesis may be made, including having asymmetric femoral condyles, having a closing radius on the femoral component, and removing certain areas of the tibial and femoral components; wherein all of the foregoing result in deeper knee flexion capabilities for knee prosthesis patients than previously achievable.

These and other features and advantages of the present invention will be set forth or will become more fully apparent in the description that follows and in the appended claims. The features and advantages may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. Furthermore, the features and advantages of the invention may be learned by the practice of the invention or will be obvious from the description, as set forth hereinafter.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

In order that the manner in which the above recited and other features and advantages of the present invention are obtained, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. Understanding that the drawings depict only typical embodiments of the present invention and are not, therefore, to be considered as limiting the scope of the invention, the present invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figures 1A and 1B</figref> depict ranges of flexion of a knee joint;</li><li><figref idref="f0002 f0003">Figures 2A-2C and 3A-3C </figref>depict various views of a generic knee prosthesis;</li><li><figref idref="f0004">Figures 4A-4D</figref> depict representative perspective views of examples of a femoral component of a knee prosthesis;</li><li><figref idref="f0005 f0006">Figures 5A-5D</figref> depict representative perspective views of examples of a femoral component of a knee prosthesis;</li><li><figref idref="f0007">Figures 6A-6B</figref> depict side views of a representative prior art tibial component of a knee prosthesis;</li><li><figref idref="f0007">Figures 6C-6D</figref> depict side views of a representative example of a tibial component;</li><li><figref idref="f0008">Figures 7A and 7B</figref> depict alternate embodiments of femoral and tibial components;</li><li><figref idref="f0009">Figure 8A</figref> illustrates a conventional femoral component while <figref idref="f0009">Figure 8B</figref> illustrates an example of a femoral component;</li><li><figref idref="f0010">Figure 9</figref> illustrates a modular attachment for use with a femoral component;</li><li><figref idref="f0011 f0012">Figures 10A-10H</figref> illustrate representative steps for attaching a femoral component to a femur, the resectioned portions of the femur shown in phantom;</li><li><figref idref="f0013 f0014 f0015">Figures 11A-11K</figref> illustrate representative steps for attaching an alternate example of a femoral component to a femur;</li><li><figref idref="f0016">Figures 12A-12B</figref> and <figref idref="f0017">Figure 13</figref> illustrate comparisons between a conventional femoral component and an example of a femoral component;</li><li><figref idref="f0018">Figure 14</figref> illustrates an alternate example of a femoral component;</li><li><figref idref="f0019">Figures 15A-15D</figref> illustrate comparisons between examples of a femoral component;</li><li><figref idref="f0020">Figures 16A-16D</figref> illustrate a manner in which an articulating surface of the femoral components shown in <figref idref="f0019">Figures 15A-15D</figref> may be extended;</li><li><figref idref="f0021">Figure 16E</figref> illustrates a shortened embodiment in which an articulating surface of the femoral component may be extended;</li><li><figref idref="f0022">Figure 17</figref> illustrates a radiograph of a normal knee flexed to approximately 160 degrees, and further illustrating the position of the patella;</li><li><figref idref="f0023">Figure 18</figref> illustrates an alternate example of a femoral component;</li><li><figref idref="f0024">Figure 19A</figref> illustrates a tibial component that does not have an articular surface posterior to the main articular surface;</li><li><figref idref="f0024">Figure 19B</figref> illustrates the Tibial Full Flex articulation being posterior to the main weight bearing articulation;</li><li><figref idref="f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032 f0033">Figures 20A-20I</figref> illustrate a representative interaction of the Femoral Full Flex articulation and the Tibial Full Flex articulation;</li><li><figref idref="f0034">Figure 21</figref> illustrates a representative interaction of the posterior articulate surface of the medial plateau of the tibia and the popliteal surface during deep flexion of the knee;</li><li><figref idref="f0035">Figure 22</figref> illustrates a representative implementation of a resection block and the femur following resection of the popliteal surface;</li><li><figref idref="f0036">Figure 22A</figref> illustrates a representative implementation of a resection block and the femur prior to resection of the popliteal surface;</li><li><figref idref="f0037">Figure 23</figref> illustrates a representative interaction of the posterior articulate surface of the medial plateau of the tibia and an extended portion of the femoral component of the knee prosthesis during deep flexion; and</li><li><figref idref="f0038">Figure 23A</figref> illustrates a representative interaction of the posterior full flex articular surface of the medial tibial plateau of a tibial component and an extended portion of the femoral component of the knee prosthesis during deep flexion.</li></ul>

<u>DETAILED DESCRIPTION OF THE INVENTION</u>

The present invention relates to knee prostheses. In particular, the present invention relates to systems for providing deeper knee flexion capabilities for knee prosthesis patients, and more particularly, to: (i) providing an extended articular surface on the proximal, anterior surface (or portion) of the posterior condyles of the femur; (ii) making modifications to the internal geometry of the femoral component and the associated femoral bone cuts; (iii) making modifications to the tibial and femoral components of a knee prosthesis, including asymmetrical tibial articular surfaces and removing certain areas of the tibial and femoral components; and (iv) having asymmetric femoral condyles, including having a closing radius on the femoral component, wherein all of the foregoing result in deeper knee flexion capabilities for knee prosthesis patients than previously achievable.

It is emphasized that the present invention, as illustrated in the figures and description herein, may be embodied in other forms. Thus, neither the drawings nor the following more detailed description of the various embodiments of the system of the present invention limit the scope of the invention. The drawings and detailed description are merely representative of examples of embodiments of the invention; the substantive scope of the present invention is limited only by the appended claims recited to describe the many embodiments. The various embodiments of the invention will best be understood by reference to the drawings, wherein like elements are designated by like alphanumeric character throughout.

With reference now to the accompanying drawings, <figref idref="f0001 f0002 f0003">Figures 1A-3C</figref> are provided for general reference to assist in understanding the features of the embodiments of the present invention. <figref idref="f0001">Figures 1A and 1B</figref> depict a range of angles possible between the tibia and femur in a person who is extending and flexing (bending) his or her knee. Specifically, <figref idref="f0001">Figure 1A</figref> depicts a range of angles possible while the person extends and bends his or her knee, realizing that some knees may flex to 160 degrees, 165 degrees, or beyond. <figref idref="f0001">Figure 1B</figref> depicts these various angles in an alternative position. These figures should be kept in mind during the discussion illustrating how with the embodiments of the present invention, knee flexion of greater than 135 degrees is possible for knee prosthetic patients, which is not generally possible with currently-available knee prostheses.

<figref idref="f0002">Figures 2A-2C</figref> depict various perspective views of a generic knee prosthesis 10. Specifically, <figref idref="f0002">Figure 2A</figref> depicts a sagittal view of a left knee joint having a knee joint prosthesis 10, with the tibia and the femur of the normal knee transparent. <figref idref="f0002">Figure 2B</figref> depicts an enlarged view of a femoral component 12 of the knee prosthesis 10, while <figref idref="f0002">Figure 2C</figref> provides a top perspective view of a tibial component 14 of the knee prosthesis. <figref idref="f0002">Figure 2B</figref> depicts certain components of the femoral component 12, such a medial receiving area 16 that may be modified in embodiments of the present invention to integrally connect with an attachment (not shown but hereinafter described) as well as a lateral receiving area 18. The internal geometry of the femoral component 12 is provided to allow a one piece femoral component 12 that is rolled into place on the resectioned femur 32, as shown in <figref idref="f0004">Figure 4D</figref>. Thus, the internal geometry of the femoral component 12 includes various surfaces, including areas 16 and 18, to accommodate the patellar articulation and the anterior extensions of the proximal portions of the posterior condyles. The resectioned portions of the condyles provide flat surfaces which are loaded in compression in full knee flexion. Additionally, the resectioned surfaces are provided such that the articular surface of the femoral component is at essentially the same position as the surface being resectioned. As such, the normal relationship between the femur and the tibia is preserved with full flexion.

Also visible in <figref idref="f0002">Figure 2B</figref> is a medial femoral condylar surface 20 and a lateral femoral condylar surface 22. <figref idref="f0002">Figure 2C</figref> depicts the tibial component 14 and its elements: a lateral tibial condylar surface 24, a medial tibial condylar surface 26, and an intercondylar surface 28. When the knee prosthesis 10 is functioning, an interface exists between the medial femoral condylar surface 20 of the femoral component 12 and the medial tibial condylar surface 26 of the tibial component 14 and between the lateral femoral condylar surface 22 of the femoral component 12 and the lateral tibial condylar surface 24 of the tibial component 14.

<figref idref="f0003">Figures 3A-3C</figref> depict additional perspective views of the generic knee prosthesis 10 with its different components. Specifically, <figref idref="f0003">Figure 3A</figref> depicts a frontal view of the knee prosthesis 10 with the femoral component 12 articulating with the tibial component 14 as described above. <figref idref="f0003">Figure 3B</figref> is a side view of the femoral component 12, and <figref idref="f0003">Figure 3C</figref> is a side view of the tibial component 14, and specifically, of the medial side of the tibial component showing the medial tibial condylar surface 26. The medial femoral condylar surface 20 slidingly interfaces with the medial tibial condylar surface 26 so that as a person flexes or extends his or her knee, the arc of the medial femoral condylar surface 20 runs along the media tibial condylar surface 26.

In some embodiments of the present invention, greater deep knee flexion is provided to the knee prosthesis 10 by providing an articular surface on the proximal, anterior surface (or portion) of the posterior condyles of the femur. At least some embodiments of the present invention embrace an additional or increased articular surface on the proximal, anterior portion of either or both of the medial or lateral posterior condyles of the femoral component 12. Embodiments of the femoral component 12 add increased articular surface area to the proximal end of the posterior condyles of the femoral component 12 in an anterior direction such that when the patient bends his or her knee during deep knee flexion, contact between the femoral component 12 and the tibial component 14 is maintained, and a greater, deeper knee flexion can be achieved.

Four different examples of how this may be achieved are demonstrated with reference to the Figures.

<figref idref="f0009">Figures 8A and 8B</figref> illustrate a femoral component 12 and method of increasing an articular surface area to the proximal end of the posterior condyles of the femoral component 12. <figref idref="f0009">Figure 8A</figref> illustrates a side view of a conventional femoral component 12. In the first example, the shaded area of the femoral component 12 of <figref idref="f0009">Figure 8A</figref>, i.e. the posterior condyle, is thickened in the anterior direction until the resulting surface opposing the bone is approaching the same plane as the posterior surface of the shaft of the distal femur. This thickening may be seen with reference to <figref idref="f0009">Figure 8B</figref>. This results in a greater articular surface area of the posterior condyles of the femoral component 12. This requires resection of more bone but is otherwise an easy modification to current prostheses and requires little to no modification of current surgical technique.

A second type of extension that extends the articular surface area is illustrated by <figref idref="f0004 f0005 f0006">Figures 4A-5C</figref>. Methods of utilizing this type of extension are illustrated with reference to <figref idref="f0010 f0011 f0012">Figures 9-10H</figref>. This type of extension utilizes an extension attachment to the femoral component 12 of a knee prosthesis 10, which when integrated with both the femoral component 12 and a patient's femur, results in a greater surface area of the femoral component 12.

As illustrated in <figref idref="f0004 f0005 f0006">figures 4A-5D</figref>, this type of extension has a modular attachment 30 that provides a modular flexion attachment surface to extend the articular surface area of the anterior portion of the proximal portion of the posterior condyles. The modular attachment 30 may be attached to the inside, or non-articular surface, of a relatively conventional total knee femoral component 12. The modular attachment 30 has a portion that may be partially received, in one embodiment, within a recessed receiving area on the flat anterior surface of one or both of the posterior condyles of the femoral component 12 and may thus be used on the medial posterior condyle, the lateral posterior condyle, or both. Alternatively, it may be implanted in a groove within either or both of the resected posterior condyles of the femur itself.

The modular attachment 30 provides an increased articular contact area as an anterior continuation of the medial femoral condylar surface 20 and/or of the lateral femoral condylar surface 22 of the femoral component 12. In some examples, the modular attachment 30 may be initially placed onto the femoral component 12 and then attached to the distal end of the patient's femur. In other examples, the modular attachment 30 may be connected first to the posterior condyles of the distal end of the femur and then integrally connected with the femoral component 12. The modular attachment 30 may be used on the medial side, on the lateral side or on both sides.

<figref idref="f0004">Figures 4A-4D</figref> depict perspective views of examples of the femoral component 12 and the modular attachment 30. As described, the modular attachment 30 attaches to the femoral component 12 and to the femur of a patient to enlarge the surface area of the femoral component 12 and, ultimately, to enable deep knee flexion beyond 140 degrees in a knee prosthesis patient. <figref idref="f0004">Figure 4A</figref> depicts a simplified side view of an example of the femoral component 12 having the modular attachment 30 attached to the posterior condyle of the femoral component. <figref idref="f0004">Figure 4D</figref> depicts a side view of the attachment integrally attached to a patient's femur and to the femoral component of the knee prosthesis. The modular attachment 30 may be modular as shown in <figref idref="f0004">Figures 4B-4D</figref> and may fit within a recess in either or both of the medial receiving area 16 and the lateral receiving area 18 (i.e. in the anterior interior surface of the posterior condyles of the femoral component 12, as shown in <figref idref="f0002">Figure 2B</figref>) and/or in either or both of the medial and the lateral posterior condyles of the femur or in both the femoral component 12 and the femur. In another example the modular attachment 30 may be a permanent part of the femoral component, as discussed below.

<figref idref="f0004">Figure 4B</figref> depicts a side view of one example of the modular attachment 30 and <figref idref="f0004">Figure 4C</figref> depicts a top view of the depicted example of the modular attachment 30. Specific dimensions of the depicted example of the modular attachment 30 are not given and one of skill in the art will recognize that the dimensions may be modified from patient to patient and will also recognize that the various portions of the modular attachment 30 may all be formed to be as wide as the condyle of the femoral component 12.

In some examples, the modular attachment 30 includes a first portion roughly perpendicular to a second portion. The first portion of the modular attachment 30 entails a flanged articular area 36 ("flanged area 36") at one end of the modular attachment 30, and an elongated stem 38 extending therefrom, which extends roughly perpendicular from the flanged area, distally from the flanged area 36. The elongated stem 38 therefore is attached to the non-articular side of the flanged area 36. Although the elongated stem is illustrated in <figref idref="f0004">Figure 4C</figref> as having a medial-lateral width substantially shorter than the medial-lateral width of the flanged area 36, the elongated stem 38 of other examples may be of any medial-lateral width up to the medial-lateral width of the posterior condyles of the femoral component 12 itself.

The elongated stem 38 has an upper side 40 and a lower side 42. Nodules 44 may be placed on either or both of the upper side 40 and the lower side 42, to enable an integral connection with the femur 32 on the upper side 40, and the femoral component 12 on the lower side 42. Some form of a nodule-receiving groove or recess (not shown) may be made in the femur 32 and/or the femoral component 12 to receive these nodules 44 and to secure the integral connection between the femur 32, the attachment 30, and the femoral component 12; with the modular attachment 30 being disposed between the femur 32 and the femoral component 12.

In examples having no nodules 44 on the elongated stem 38, the attachment 30 may fit within a recess made on either or both of the medial receiving area 16 and the lateral receiving area 18 of the femoral component 12. The elongated stem 38 of the modular attachment 30 would fit within such recesses and integrally connect thereto. The modular attachment 30 may simultaneously connect with the femur 32 on the upper side 40 (generally) of the elongated stem 38. In examples having no nodules on the elongated stem, the stem of the modular portion may further fit into a groove prepared in the resected posterior condyles of the femur.

The modular attachment 30 increases the overall surface area of the femoral component 12 and prolongs the interface and contact that exists between the femoral component 12 and the tibial component 14. This enables greater knee flexion in prosthetic knee patients because the femoral component 12 remains interfaced with the tibial component 14 throughout the full range of flexion resulting in pain-free knee flexion.

Without this increased surface area, the medial and lateral proximal edges of the posterior femoral condyles of a prothesis may push into the proximal surfaces of the tibial component 14 and may produce wear of the tibial component 14. In addition, the tibial component 14 may contact the bone of the distal femur 32 that is anterior and/or proximal to the proximal edges of the posterior condyles of the prosthesis and cause pain to and limit flexion of the prosthetic knee patient and may cause wear to the tibial component. Further, without this added surface area, with flexion beyond 140 degrees, the tibial component 14 may exert a force in the distal direction on the femoral component 12, which may result in loosening of the femoral component 12. Therefore, the modular attachment 30 extends the life of the prosthetic knee, decreases pain to the patient, and ultimately, enables a prosthetic knee patient to achieve deep knee or full functional flexion.

<figref idref="f0005 f0006">Figures 5A-5D</figref> depict various perspective views of the modular attachment 30 as it is attached to the femoral component 12 and to the femur 32. <figref idref="f0005">Figure 5A</figref> is illustrative of the modular attachment 30 as it is attached to the femur 32 prior to attachment of the femoral component 12. <figref idref="f0005 f0006">Figures 5B-5D</figref> are illustrative of the modular attachment 30 as it is recessed within the femoral component 12 prior to attachment to the femur 32, and specifically, as the modular attachment 30 is integrally connected to either or both of the medial femoral receiving area 16 and the lateral femoral receiving areas 18.

<figref idref="f0010 f0011 f0012">Figure 9 and Figures 10A-10H</figref> illustrate methods of attaching the modular attachment 30 to the femur 32, followed by attaching the femoral component 12 to the femur 32 and modular attachment 30. <figref idref="f0010">Figure 9</figref> illustrates the resection needed on the femur 32 prior to creating the recess in the femur to allow attaching the modular attachment 30. <figref idref="f0010 f0011 f0012">Figure 9 and Figures 10A-10H </figref>do not illustrate the specific resection needed for the modular attachment 30, but the resection needed will be appreciated by one of skill in the art. After resection is completed, as at <figref idref="f0011">Figure 10A</figref>, the modular attachment 30 may be attached to the femur as at <figref idref="f0011">Figure 10B</figref>. The femoral component 12 may then be attached to the femur 32 (and to the modular attachment 30, if desired) by positioning and moving the femoral component 12 as illustrated in <figref idref="f0011 f0012">Figures 10C-10H</figref>. As may be appreciated from the sequence of illustrations depicted in <figref idref="f0011 f0012">Figures 10C-10H</figref>, the femoral component 12 needs to be rotated or rolled into position, with initial contact beginning in the posterior region as illustrated in <figref idref="f0012">Figure 10E</figref> and progressing to the fully-seated position illustrated in <figref idref="f0012">Figure 10G</figref>. This is a new implantation technique that will require some additional practice and training over current techniques.

As has been set forth above in reference to <figref idref="f0004">Figure 4A</figref>, a third type of extension having an extended articular surface is not modular and does not utilize a separate modular attachment 30. In such extensions, an extended articular surface corresponding to the flanged area 36 of the modular attachment 30 may be integrally formed as part of one or both condyles of the femoral component 12. Placement of one such example is illustrated with reference to <figref idref="f0013 f0014 f0015">Figures 11A-11K</figref>. As may be appreciated with reference to these Figures, placement of such an extension also utilizes a similar rotational placement technique to that illustrated in <figref idref="f0011 f0012">Figures 10C-10H</figref>. As may be appreciated by reference to <figref idref="f0012 f0015">Figures 10H and 11 K</figref>,any of the modular or non-modular extensions may, optionally, be further secured by one or more screws placed in an anterior flange of the femoral component 12.

One advantage of the example illustrated in <figref idref="f0013 f0014 f0015">Figures 11A-11K</figref> is that the implanting surgeon may decide whether to utilize the illustrated example or a traditional femoral component 12 after the distal and anterior oblique cuts have been made. This is illustrated in <figref idref="f0016">Figures 12A and 12B. Figure 12A</figref> shows a traditional femoral component 12. <figref idref="f0016">Figure 12B</figref> shows the example of the femoral component 12 illustrated in <figref idref="f0013 f0014 f0015">Figures 11A-11K</figref>. As may be appreciated by reference to the Figures, the distal cuts 62 and anterior oblique cuts 64 are essentially identical. This may be further appreciated by reference to <figref idref="f0017">Figure 13</figref>, which shows a superimposed view of <figref idref="f0016">Figures 12A and 12B</figref>, not only showing that the distal femoral cuts 62 and the anterior oblique cuts 64 are identical, but also showing that the total amount of bone resected for the illustrated embodiment is similar to or less than the amount resected using current techniques and femoral components 12.

In a non-modular example of the femoral component 12 as shown in <figref idref="f0013 f0014 f0015">Figures 11A-11K</figref> and in a modular example of the femoral component as shown in <figref idref="f0004 f0005 f0006">Figures 4A-5D</figref>, there are junctions where the inside flat surfaces of the prosthesis (which when implanted are in contact with the bone) meet. These flat surfaces, rather than coming together at a sharp angle, may or may not have a radius connecting the two flat surfaces. Not all of the junctions of the flat surfaces necessarily need a radius and in some embodiments none of the junctions of flat surfaces will have radii. The flat surfaces may or may not be in exactly the same planes as on conventional knees and will provide for the placement of a non-modular surface that will provide an articulation for the proximal, anterior portion of the posterior femoral condyles extending to or almost to a plane that is a continuation of the posterior cortex of the distal femoral shaft. In examples where one or more radii are provided to the junction(s) of the inside flat surfaces of the femoral component 12, corresponding radii 31 or curvatures may be provided to the resected bone surface of the femur, as is illustrated in <figref idref="f0005">Figure 5A</figref>. As may be appreciated by one of skill in the art, the presence of the corresponding radii 31 may assist in the rotational placement of the femoral component 12 as illustrated in <figref idref="f0011 f0012 f0013 f0014 f0015">Figures 10A-10H and 11A-11K</figref>.

This internal configuration allows the femoral component 12 to be initially applied to the femur in a flexed position and then rotated into the fully extended position as it is implanted fully, as illustrated and discussed with reference to <figref idref="f0011 f0012 f0013 f0014 f0015">Figures 10A-10H and 11A-11K</figref>. Screw(s) may, optionally, be placed in the anterior flange of the femoral component 12 to firmly stabilize the component. This ability facilitates implanting the non-modular femoral component 12 or a modular femoral component 12 with the modular attachment 30 already implanted on the posterior condyles of the femur 32.

A fourth type of femoral component 12 is illustrated in <figref idref="f0018">Figure 14</figref>. This example has a femoral component 12 that replaces the weight-bearing distal femoral condyles, in addition to some or all of the articular surface of the posterior condyles extending proximally and anteriorly to an area that is in the same plane as a continuation of the posterior cortex of the distal one fourth to one third of the femur. Such an example may comprise separate medial and lateral components or they may be attached together to form one component that replaces or resurfaces the medial and lateral condyles.

Historically, many early total knee femoral components 12 did nothing regarding the patello-femoral joint. Because a certain percentage of those patients had anterior knee pain, an anterior flange was added to the femoral component 12 to resurface the trochlea (patellar groove). This weakened the patella and resulted in fractures in some patients. Recently techniques have been developed to minimize patellar pain which do not require implantation of a component. The example shown in <figref idref="f0018">Figure 14</figref> does not have an anterior flange that is an integral part on the condylar portion of the prosthesis. It is anticipated that such a device alone may, in some patients, be adequate to replace the femoral condyles and allow the surgeon to treat the patello-femoral joint as he/she felt was indicated. Alternatively, a separate patello-femoral articular surface or surfaces could be implanted. The patello-femoral implant(s) could be entirely separate or could be modular and attached to the device shown in <figref idref="f0018">Figure 14</figref>. The example illustrated in <figref idref="f0018">Figure 14</figref> includes the ability to attach a modular anterior flange (trochlear groove) to the device shown in the Figure. It can be appreciated in <figref idref="f0018">Figure 14</figref> that the prosthesis shown with the profile of the femur in light outline, could not be implanted without significant flexion of the knee.

Implementations of the present invention embrace a femoral component 12 and/or a modular attachment 30 comprising a metal, metal alloy, ceramic, carbon fiber, glass, polymer (including bone cement), organic material, retrieved human or animal tissue, and naturally occurring or synthetic materials used either separately or in any combination of two or more of the materials.

As may be appreciated by reference to the above discussion and the corresponding Figures, currently-existing femoral components 12 provide an articular surface that only extends a short distance in the proximal anterior direction of the posterior condyle. For example, as may be seen with reference to <figref idref="f0002">Figures 2A</figref> and <figref idref="f0009">8A</figref>, the articular surface at the anterior end of the posterior condyle typically extends to and replaces at most the posterior third of the posterior condyle, as measured from the most posterior portion of the patient's original posterior condyle (or from the most posterior portion of the femoral component 12) to a plane that is a continuation of the distal one fourth to one third of the posterior cortex of the femoral shaft.

In contrast, the various examples of the femoral component 12 illustrated in the Figures and discussed above provide an extended articular surface for either or both of the medial condyle and the lateral condyle that extends in a proximal anterior direction so as to extend half or more of the antero-posterior distance between the most posterior portion of the posterior condyle and the plane that is a continuation of the distal one fourth to one third of the posterior cortex of the femoral shaft. In some examples, the extended articular surface extends at least two-thirds of the antero-posterior distance between the most posterior portion of the posterior condyle and the plane that is a continuation of the distal one fourth to one third of the posterior cortex of the femoral shaft. In other examples, the extended articular surface extends nearly the entire antero-posterior distance between the most posterior portion of the posterior condyle and the plane that is a continuation of the distal one fourth to one third of the posterior cortex of the femoral shaft. In embodiments of the invention, the extended articular surface extends even further, to encompass a distal portion of the posterior cortex of the femoral shaft, as illustrated in <figref idref="f0020">Figures 16A-16D</figref>.

The surface of the extension, which may or may not contact bone and is a continuation of the femoral articular surface, can be referred to as the Full Flex Articulation. There may be a corresponding surface on the posterior edge of the medial and or lateral_tibial articulation which is not part of the articular surface of the tibia when the tibia is in full extension. For example, in some implementations of the current invention there is a corresponding surface on the posterior edge of the medial tibial articulation where the center of the medial articular surface is more than 20% of the distance from the posterior edge of the component to the anterior edge.

The embodiment illustrated in <figref idref="f0024">Figure 19A</figref> shows a non-articular surface 41 posterior to the main articular surface 43. <figref idref="f0024">Figure 19B</figref> illustrates a full flex articular surface 45 and an articular surface 47. The Tibial Full Flex articulation of <figref idref="f0024">Figure 19B</figref> is posterior to the main weight bearing articulation and articulates with a specific articular area on the femoral component, the Femoral Full Flex articulation (proximal extension 50) shown in <figref idref="f0020">Figures 16A-16D</figref> and shown in a slightly shortened embodiment in <figref idref="f0021">Figure 16E</figref>. The interaction of the Femoral Full Flex articulation and the Tibial Full Flex articulation is illustrated in <figref idref="f0025 f0026 f0027 f0028 f0029 f0030 f0031 f0032 f0033">Figures 20A-20I</figref>, wherein <figref idref="f0025 f0026 f0027 f0028 f0029">Figures 20A-20E</figref> are at 0 degrees, <figref idref="f0030 f0031 f0032 f0033">Figures 20F-20</figref> is at 90 degrees, <figref idref="f0031">Figure 20G</figref> is at 130 degrees, <figref idref="f0032">Figure 20H</figref> is at 150 degrees, and <figref idref="f0033">Figure 20I</figref> is at 160+ degrees. <figref idref="f0026">Figure 20B</figref> identifies a representative position of unresected tibial plateau 51. <figref idref="f0027">Figure 20C</figref> identifies a representative closing radius on a posterior portion of a femoral component 53. <figref idref="f0028">Figure 20D</figref> identifies a representative Full Flex Femoral articulation 50. <figref idref="f0029">Figure 20E</figref> identifies a representative Full Flex Tibial articulation 55. <figref idref="f0032">Figure 20H</figref> identifies a representative approach of the Full Flex Femoral articulation 50 to the Full Flex Tibial articulation 55 during flexion. <figref idref="f0033">Figure 20I</figref> identifies a representative contact of the Full Flex Femoral articulation 50 to the Full Flex Tibial articulation 55 during deep flexion.

<figref idref="f0019">Figures 15A-15D</figref> illustrate the various manners in which the four previously-discussed examples of the femoral component 12 provide an extended articular surface 48. The concept of adding more articular surface to the proximal portion of the posterior condyles of the femoral component may be generally accomplished by extending the proximal portion anteriorly until the articular surface approaches, or extends beyond the plane of the posterior surface of the shaft of the distal femur, if that plane were to extend distally. For example, as may be seen from <figref idref="f0019">Figures 15A-15D</figref>, the extended articular surface 48 of each embodiment extends the articular surface at the anterior end of one or both of the medial posterior condyle or the lateral posterior condyle. According to the invention and as illustrated in <figref idref="f0020">Figures 16A-16D</figref>, the articular surface may be further extended in a proximal direction from the end of the extended articular surface 48. This further extension is provided by a proximal extension 50. The proximal extension 50 may be an integral part of the femoral component 12, it may be a part of the modular attachment 30, or it may be provided as a separate and additional component. In one embodiment where the proximal extension 50 is provided, the proximal extension 50 acts as a fulcrum that interacts with the tibia or with the tibial component 14 to increase separation between the femur 32 and the tibia during full functional flexion to improve the deep knee flexion. In another embodiment, the proximal extension 50 allows the normal relationships between the tibia and femur in full functional flexion to exist while maintaining contact between the two surfaces.

Thus, in some embodiments of the present invention, greater deep knee flexion is facilitated by providing an articular surface on the proximal, anterior surface (or portion) of the posterior condyles of the femur. At least some such embodiments embrace an additional or increased articular surface on the proximal, anterior portion of either or both of the medial or lateral posterior condyles of the femoral component 12. Embodiments of the femoral component 12 add increased articular surface area to the proximal end of the posterior condyles of the femoral component 12 in an anterior direction such that when the patient bends his or her knee during deep knee or full functional flexion, contact between the femoral component 12 and the tibial component 14 is maintained, and a greater, deeper knee flexion may be achieved.

In at least some examples, greater deep knee flexion may be provided or improved by modifying the tibial articulation, in which the center of the conforming medial tibial articular surface of the tibial component 14 is moved posterior relative to what is currently available. Additionally, the overall shape of the lateral tibial articular surface may be modified. This is illustrated with reference to <figref idref="f0007">Figures 6A-6D</figref>.

In such examples of the tibial component 14, the condylar or articular plateau surfaces may be asymmetric. That is, the lateral undersurface side of the tibial component 14 is shorter in the anterior-posterior dimension than the medial side, and the top of the tibial component 14 may also be asymmetric.

Anatomically the tibial plateau has a greater anterior-posterior dimension medially than it has laterally. In order to cover as much of the cut proximal tibia as possible and avoid anterior or posterior overhang of the lateral plateau, it is necessary to have a component that is larger in the antero-posterior dimension medially than it is laterally. In one example, this is accomplished by moving the center of the medial articular surface posteriorly to compensate for the dimensional differences. In order to achieve full flexion, it is important to have the medial center of rotation on the tibia (which is a concave segment of a sphere) more posterior than is currently available with other designs. This allows the proximal tibia, when the knee is flexed beyond approximately 120-130 degrees, to be positioned anteriorly enough so that there is no impingement of the posterior edge or portion of the medial tibial articular surface on the proximal portion of the posterior medial condyle of the femur. Current designs of tibial components 14, which will allow the tibia to move anterior with flexion, either have a non-spherical medial tibial articular surface or the center of rotation of the spherical articular surface is not as far posterior as is provided by the examples described below. However, examples may be used in combination with any knee replacement design that will allow knee flexion to 120° or greater.

Currently-available total knee tibial components 14 that have a fixed center of rotation medially have the center of rotation located at a position that is around 35-45% of the entire antero-posterior dimension from the posterior surface of the tibial component 14. In some examples of the tibial component 14, the center of rotation is moved posteriorly so that it is between 18-30% of the antero-posterior dimension from the posterior wall of the tibial component 14.

In the normal knee the medial side of the knee is constrained in that for any degree of flexion the position of the medial femoral condyle relative to the tibial articular surface is roughly fixed and does not move anteriorly or posteriorly a significant amount in the flexion range of roughly 20-140 degrees. In contrast, on the lateral side, except for full extension and flexion, after around 20-40 degrees of flexion the lateral femoral condyle can move anterior and posterior on the lateral tibial plateau. In full functional flexion to 160 degrees and beyond, the lateral femoral condyle may appear to be touching only the most posterior portion of the opposing tibial plateau or it may contact the plateau more anterior clearly on the flattened portion of the lateral tibial plateau.

Therefore, in examples of the tibial component 14, the lateral tibial articular surface is basically flat in the antero-posterior sense, except anteriorly where there is an anterior lip which prevents the tibial component from rotating too far externally and allowing the lateral femoral condyle to slide off the anterior edge of the tibial component. In some examples, the basically flat portion of the lateral tibial articular surface may comprise between two-thirds and seven-eighths of the total antero-posterior dimension of the tibial component 14. In some examples, a slight lip may be present posteriorly on the lateral side, however, as long as the fixed center of rotation is positioned as described, no lip is required posteriorly on the lateral side. The lateral tibial articular surface is either flat or concave when viewed in the frontal plane and, if concave, may or may not be the same radius of curvature of the opposing femoral condyle or it may have a greater radius when viewed in the frontal plane. This flat or concave groove is flat on the bottom when viewed in the sagittal plane, except for the anterior and posterior ends as noted above and is generated around a point that corresponds to the center of rotation of the medial condyle. In some examples, the postero-lateral tibial articulation may be the same as described for the medial posterior full flex articulation. In other examples, the medial tibial articular surface may be the same as, or similar to the flat articular surface described for the lateral tibial plateau. However, the position of the medial articular contact is mainly obligatory while the position of the lateral articular contact is non-obligatory. Thus, the position of the lateral articular contact is likely determined by the task being performed, by comfort, or by culture.

<figref idref="f0007">Figures 6A-6D</figref> depict a comparison of a prior art tibial component 14's medial tibial condylar surface 26 and lateral tibial condylar surface 24 with an example of the tibial component 14 as discussed above. Specifically, <figref idref="f0007">Figures 6A and 6B</figref> reflect side views of medial and lateral sides of some currently available tibial components 14, respectively, while <figref idref="f0007">Figures 6C and 6D</figref> illustrate side views of medial and lateral sides of an example of the tibial component 14 as discussed above. It will be appreciated that a number of varied configurations for the medial and lateral articular surfaces ranging from almost flat, both medially and laterally, to more conforming, as shown in <figref idref="f0007">Figures 6A and 6B</figref>, have been used in the past; however, there are none that have either a combination of a posteriorly-displaced medial articular surface and a relatively-flat lateral articular surface, or a medial femoral full flex tibial articulation. These configurations permit the lateral femoral condyle to move anteriorly and posteriorly as the knee flexes and extends. Other configurations may be provided, so that as long as the lateral tibial articular surface will allow this antero-posterior motion, the lateral tibial configuration does not need to be specifically as shown in <figref idref="f0007">Figure 6D</figref>.

The lateral tibial articulation may in some examples have no posterior lip (Figure 6E) and in other examples the posterior surface may slope downward (Figure 6F) when it is accompanied by a medial tibial articulation that provides for flexion beyond 135 degrees.

In the prior art tibial component 14, the condylar surface has a curvature centered on a fixed point 52. The distance from the fixed point 52 (or from the low point of the curvature centered on the fixed point 52) to the posterior edge 54 of the tibial component is approximately 35-45% of the antero-posterior dimension of the tibial component 14. These measurements are similar for the medial (<figref idref="f0007">Figure 6A</figref>) and lateral (<figref idref="f0007">Figure 6B</figref>) sides of the tibial component 14. Currently available tibial components 14 have a lip 56.

In the example of the tibial component 14 illustrated in <figref idref="f0007">Figures 6C and 6D</figref>, there is no tibial component lip 56. Rather, the medial tibial condylar surface 26 runs along a smooth arc. As the arc is generated, a low lip may be present in some embodiments and may extend up to and include the femoral full flex posterior articulation. The amount of the lip will be determined by the relationship of the center of rotation to the posterior edge 54 of the tibial component 14. Though the radius from fixed point 52 to the articular surface in <figref idref="f0007">Figures 6A and 6C</figref> is the same, the distance from the fixed point 52 (or from the low point of the curvature centered on the fixed point 52) to the posterior edge 54 of the tibial component 56 is shorter, at approximately 18-30% of the antero-posterior dimension from the posterior end of the tibial component 14, as may be seen in <figref idref="f0007">Figure 6C</figref>. With respect to the lateral side of the tibial component 14, in the example illustrated in <figref idref="f0007">Figure 6D</figref>, there is both an anterior lip 58 and a small posterior lip 60. In alternate examples, the posterior lip 60 may be omitted as discussed above.

Thus, as has been illustrated with reference to <figref idref="f0007">Figures 6A-6D</figref>, greater deep knee flexion may be provided or improved by modifying the tibial articulation, in which the center of the conforming medial tibial articular surface of the tibial component 14 is moved posterior relative to what is currently available. This change alone, with some currently-available femoral components, will increase the amount of flexion achieved when compared to a standard tibial component. Additionally, the overall shape of the lateral tibial articular surface may be modified. This allows the proximal tibia, when the knee is flexed beyond approximately 120-130 degrees, to be positioned anteriorly enough so that there is no impingement of the posterior edge or portion of the medial tibial articular surface on the proximal portion of the medial condyle of the femur. Therefore, greater deep knee flexion may be achieved. It can thus be appreciated that the use of the above tibial component with a conventional femoral component will facilitate greater flexion than will the use of a conventional tibial component. Similarly, the use of any of the above-described femoral components with a conventional tibial component will facilitate more flexion than will use of a conventional tibial component with a standard femoral component.

<figref idref="f0008">Figures 7A and 7B</figref> depict modifications to the femoral component 12 and the tibial component 14 to enable deeper knee flexion. Specifically, <figref idref="f0008">Figure 7A</figref> depicts a sagittal sectional view of a knee prosthesis 10 with a modified femoral component 12 and tibial component 14. In <figref idref="f0008">Figure 7A</figref> an area 102 of the femoral component 12 is removed, as represented by the dashed line. This area 102 is above and between the posterior extreme 104 and the anterior side 106 of the posterior extreme 104. By removing the area 102, deeper flexion for prosthetic knee patients is partially achievable.

Similarly, with the tibial component 14 in <figref idref="f0008">Figure 7B</figref>, a medial side 25 may appear to be relatively lengthened in the antero-posterior dimension anteriorly by moving the articular surface 24 posterior and thereby having more of the tibial component anterior to the posteriorly-displaced medial articulation. This may give the appearance of having removed a posterior portion of the tibial component 14 and moved it to the anterior. A lateral side 27 of the tibial component may be shortened in the antero-posterior dimension relative to the medial side 25 (i.e., area 100). <figref idref="f0008">Figure 7B</figref> illustrates the foregoing in plan view. In other words, by posteriorly shortening the lateral side.27 (i.e. by removing area 100) of the tibial component 14 and by displacing the medial articular surface 24 more posterior, deeper knee flexion is possible. And, these modifications create the opportunity for a prosthetic knee patient to achieve a deeper knee flexion than possible with currently-available prosthetic knees.

In at least some examples, greater deep knee flexion can be achieved by providing an asymmetrical femoral component 12. The asymmetrical femoral component 12 permits transfer of more than one-half of the force transmitted across the joint to be transmitted to the medial side, as occurs in the normal knee. Some such examples are illustrated with reference to <figref idref="f0022 f0023">Figures 17-18</figref>. <figref idref="f0022">Figure 17</figref> illustrates a radiograph of a knee at 160-degree flexion. In the radiograph, the femur 32 is viewed in the antero-posterior direction, and a medial condyle 66 of the femur 32, a lateral condyle 68 of the femur 32, and a patella 70 are visible. As may be appreciated by reference to the Figure, the medial-lateral width of the articulating portion of the medial condyle 66 is larger than the medial-lateral width of the lateral condyle 68. Specifically, in the Figure, the medial-lateral width of the articular portion of the medial condyle 66 is represented by X. As may be seen in the Figure, the medial-lateral width of the lateral condyle 68 is approximately 75% or less of the medial-lateral width X of the medial condyle 66.

As may also be appreciated by reference to <figref idref="f0022">Figure 17</figref>, the center of the patella 70 is lateral to the midline of the knee. Specifically, in the Figure the medial-lateral distance between the most medial portion of the distal end of the femur 32 and the center of the patella 70 is represented by Y. As may be seen, the corresponding medial-lateral distance between the most lateral portion of the distal end of the femur 32 and the center of the patella 70 is approximately 75% or less (73% in the Figure) of Y. In some embodiments of the invention, the femoral component 12 may mimic the actual physical structure of the knee represented in <figref idref="f0022">Figure 17</figref>.

In such examples of the femoral component as illustrated in <figref idref="f0023">Figure 18</figref>, the articular portion of the lateral condyle is, in its medial-lateral width, 75% or less than the width of the medial condyle. This allows for more than one half of the force that is transmitted across the joint to be transmitted to the medial side, which is what occurs in the normal knee. It also allows the patellar or trochlear groove to be lateralized because this groove distally is defined by its position between the medial and lateral condyles. In the normal knee the patella tends to be slightly lateralized on the femur and this lateral displacement of the groove accomplishes what many conventional total knee replacements accomplish by externally rotating the femoral component 12 in the total knee replacement. In one example the condyles in the frontal plane are seen to be circular with a constant radius. The medial and lateral condyles do not need to be the same radius, but may both be circular when viewed in that plane. When viewed in the sagital plane the condyles will be seen to have a closing radius posteriorly and anteriorly may blend into the anterior flange in the embodiments where an anterior flange is used.

<figref idref="f0023">Figure 18</figref> illustrates a front view of a femoral component 12 in accordance with the described example. In the Figure, illustrative measurements are illustrated to show features of the described example, and are not meant to be limiting of the features of the described embodiments. As shown in <figref idref="f0023">Figure 18</figref>, the total medial-lateral width of the femoral component 12 may be approximately 72 millimeters (mm). In this example, the medial-lateral width of the medial femoral condylar surface 20 in the posterior portion of the medial posterior condyle is approximately 32 mm, while the medial-lateral width of the lateral femoral condylar surface 22 is approximately 22 mm. Thus, in the illustrated example, the medial-lateral width of the lateral femoral condylar surface 22 is approximately 69% of the medial-lateral width of the medial femoral condylar surface 20.

In the illustrated example, a patellar groove 72 is defined by the space between the medial femoral condylar surface 20 and the lateral femoral condylar surface 22. Because the medial-lateral width of the medial femoral condylar surface 20 is larger than the medial-lateral width of the lateral femoral condylar surface 22, the patellar groove 72 is displaced laterally, which is what occurs in the normal knee. As may be appreciated by reference to <figref idref="f0023">Figure 18</figref>, the patellar groove 72 may be provided at an angle as the patellar groove 72 moves from a most proximal anterior portion to a distal anterior portion to a distal posterior portion and to a proximal posterior portion. For example, the angle of the patellar groove 72 in <figref idref="f0023">Figure 18</figref>, as measured from a sagittal plane is approximately 86 degrees.

Thus, the illustrated femoral component 12 may assist in achieving deeper knee flexion and, in some examples, full functional flexion, by providing an asymmetric femoral component 12. The asymmetric femoral component 12 may assist in achieving deeper knee flexion by better simulating physiologic loading and patellar tracking. The asymmetric femoral component 12 allows for more normal loading of the joint with the medial side taking more of the load than the lateral side. Additionally, the asymmetrical femoral component 12 allows for more anatomically correct lateral tracking of the patella which may decrease problems of patellar pain, subluxation, and dislocation. One of skill in the art will readily recognize that in some examples the tibial component 14 may be modified to accommodate an asymmetric femoral component 12.

As discussed herein, at least some examples embrace providing deeper knee flexion capabilities where the medial femoral side stays relatively fixed and the lateral side glides forwards and backwards. While some examples embrace a knee with a tibial component that keeps the femoral component relatively fixed on the medial side and able to glide on the lateral side, other examples embrace a knee that is relatively fixed on the lateral side and able to glide on the medial side. This, for example, would apply to the tibial component.

Additionally, while the additional articular surface on the femoral component could be medial, lateral or both, at least some examples embrace its application to use the Tibial and Femoral Full Flex articulations either medially, laterally, or both.

Referring now to <figref idref="f0034">Figure 21</figref> a perspective side view of a knee 200 is shown. In at least some examples, greater deep knee flexion may be further provided, improved, or enhanced by removing a portion of the popliteal surface 202 of the femur 210. The popliteal surface 202 may include bone proximal to the posterior articular surfaces of the medial condyle, the lateral condyle, or both the medial and lateral condyles. Resection of the popliteal surface 202 may be accomplished by any appropriate method known in the art. For example, a portion of the tibia is first resectioned thereby providing sufficient clearance to resect the necessary portion of the popliteal surface 230.

The amount of bone resected from the tibia, the femur or both will vary from individual to individual depending upon the specific anatomy of the tibia and the femur. The resectioned popliteal surface 230 provides additional clearance between opposing surfaces of the tibia 220 and the femur 210. Specifically, the resectioned popliteal surface 230 prevents an impingement of the posterior articulate surface 250 of the medial condyle 240 of the tibia 220 on the femur 210 during deep flexion of the knee 200. As such, the knee 200 may flex freely without the tibia 220 adversely binding on, or contacting any portion of the femur 210. Additionally, the resectioned popliteal surface 230 may provide flexion exceeding 140°. In one example, the resectioned popliteal surface 230 provides flexion exceeding 160°.

Referring now to <figref idref="f0035">Figure 22</figref>, a perspective side view of a knee 200 is shown following resection of the popliteal surface 202 to provide the resectioned surface 230. As previously discussed, resection of the popliteal surface 230 may be accomplished by any appropriate method known in the art. However, in one example a resection block 300 is utilized to guide a cutting device 310 in making the resection 230. The resection block 300 is comprised of a metallic material, similar to the metallic materials previously discussed, and includes an outer surface 312, an inner surface 314, and a slot 316. The outer surface 312 is contoured and adapted to substantially overlap the lateral and medial condyles of the femur 210. The inner surface 314 includes a plurality of angled surfaces that mirror the resectioned and shaped surfaces of the lateral and medial condyles of the femur 210. Thus, the inner surface 314 of the resection block 300 is adapted to compatibly engage the resectioned surfaces 62, 64, and 366 of the femur 210. The engaged resection block 300 and femur 210 are further secured via a plurality of fasteners 320, such as screws. This may not be necessary in all cases. The fasteners 320 are required only to firmly attach the guide to the femur. In some examples, the interaction between the guide and the femur is such that the guide is held firmly in place without fasteners. In another example, the guide is held in place by any means to facilitate an accurate resection of the above mentioned area of the femur.

The interaction between the resection block 300 inner surface 314 and the resectioned surfaces 62, 64, and 366 of the femur 210 accurately aligns the slot 316 with the popliteal surface 202 of the femur 210. The slot 316 generally comprises an external opening 330 and an internal opening 332. The external opening 330 comprises a first width that is slightly greater than the width 338 of the cutting device 310. As such, the external opening 330 is adapted to compatibly receive the cutting device 310. The internal opening 332 is positioned exactly adjacent to the popliteal surface 202 and comprises a second width that is greater than the first width and approximately equal to the desired width of the popliteal resection 230. Thus, the walls 334 of the slot taper inwardly from the second opening to the first opening thereby providing a wedged slot 316.

The cutting device 310 may include any device compatible with the slot 316. In one embodiment an oscillating blade 340 is provided. The oscillating blade 340 includes a shank 342, a cutting head 344 and a stop 346. The shank 342 generally comprises a surface that is adapted to compatibly and securely engage a tool (not shown) capable of moving the blade 340 relative to the resection block 300 and femur 210. The cutting head 344 generally comprises a plurality of teeth suitable for removing the desired portions of the popliteal surface 202 to form the resection 230. The stop 346 generally comprises a ferule, a crimp, or some other feature that provides a point on the blade 340 that is wider than the first opening 330 of the slot 316. As such, the stop 346 is unable to enter the slot 316 thereby limiting the depth into which the blade 340 is permitted to enter the slot 316. Thus, the stop 346 acts as a depth gauge to control or limit the final depth of the popliteal resection 230. In one embodiment, the stop 346 further comprises a set screw whereby the stop 346 is loosened and repositioned on the blade 340 to change the depth into which the blade 340 is permitted to enter the slot 316. In another embodiment, the cutting device 310 is a burr bit having a stop 346 to limit the cutting depth of the burr.

Referring now to <figref idref="f0036">Figure 22A</figref>, an underside, perspective view of the femur 210 and resection block 300 are shown. The resection block 300 includes a first slot 316 and a second slot 318 separated by a connecting portion 326 of the resection block 300. The first slot 316 is positioned adjacent to the medial condyle 66 of the femur 210 and the second slot 318 is positioned adjacent to the lateral condyle 68. Each slot is positioned at a different height relative to the asymmetric, natural positions of the medial and lateral condyles 66 and 68. Thus, the first and second slots 316 and 318 of the resection block 300 are adapted to optimally resect the popliteal surface 202 of the femur 210 with respect to the asymmetric positions of the condyles 66 and 68. In another example, the first and second slots 316 and 318 are positioned at equal heights so as to provide a resectioned popliteal surface 230 that is symmetrical without respect to the asymmetrical condyles 66 and 68. In yet another example, the positioning of the external opening 330 relative to the internal opening 332 of the first slot 316 is different than the positioning of the external opening 330 relative to the internal opening 332 of the second slot 318. As such, the radius of each wedge opening 316 and 318 is different and the resultant contours or shapes of the resectioned popliteal surface 230 for the first and second slots 316 and 318 will be asymmetrical. In another example, connecting portion 326 is eliminated thereby providing a single guide slot. In this example, upper and lower portions of the guide are held in place relative to one another via lateral and medial bridges. The lateral and medial bridges maintain the position of the upper and lower portions of the guide, as well as define the outer edges of the slot. In another example, lateral and medial bridges are used to provide multiple slots within the guide.

Referring now to <figref idref="f0035">Figures 22</figref> and <figref idref="f0036">22A</figref>, the popliteal resection 230 is made by inserting the cutting device 310 into the slot 316 and removing the popliteal surface 202 to the desired depth, as limited by the stop feature 346 and the radial limitations of the wedged slot 316. The wedged shape of the slot 316 permits the cutting device 310 to be pivoted along the radius of the wedge, wherein the contact between the stop 346 and the external opening 330 acts as a fulcrum for the radius of the wedge. The resultant resection 230 therefore comprises a radial surface configured and shaped to receive the femoral component 12 of the knee prosthesis. Following formation of the popliteal resection 230, the screws 320, or other stabilizing methods, and the resection block 300 are removed from the femur 210.

Referring now to <figref idref="f0037">Figures 23</figref>, a cross-sectional side view of a knee 200 is shown following resection of the popliteal surface 230. The femoral component 12 of the knee prosthesis may be modified to correspond to the resectioned portion 230 of the popliteal surface 202. For example, a portion 212 of the femoral component 12 of the knee prosthesis is extended and contoured to seat within the resected portion 230 of the popliteal surface 202. As such, the posterior articular surface 250 of the medial condyle 240 of the tibia 220 compatibly and smoothly interacts with the extended portion 212 thereby further enabling the knee 200 to achieve deep flexion. Furthermore, the interaction between the posterior articulate surface 250 and extended portion 212 prevents the posterior articulate surface 250 from binding on a terminal surface 214 of the femoral component and displacing the femoral component 12 in an anterior direction 300 during deep flexion. In some examples, the extended portion 212 is used in conjunction with a tibial implant having a spherical medial side. In another embodiment, the extended portion 212 is used in conjunction with any knee replacement that will allow knee flexion to 120° or greater. For example, in one example a femoral component of a knee prosthesis system is modified to include a piece of metal up the back of the posterior portion of the component to provide an extended portion 212 compatible with the tibial component of the knee prosthesis system.

In some examples including the extended portion 212, the femoral component 12 does not include an interior flange or any provision for patella-femoral articulation, as shown in <figref idref="f0019">Figures 15B</figref> and <figref idref="f0020">16B</figref> above. As such, the lack of an anterior flange allow the component 12 to be impacted onto the femur in a relatively conventional manner, except that the component 12 is implanted after being rotated posteriorly relative to a conventional prosthesis. Additionally, the femoral component 12 can be used without a separate patella-femoral articular implant. In some examples, the component 12 is used with a modular flange attached to the condylar implant to provide femoral articulation of the patella. In another example, the femoral component 12 is used with separate, unattached patella-femoral implants. Finally, in another example a separate femoral flange is used for a patella that does not have an implanted component.

Referring now to <figref idref="f0038">Figure 23A</figref>, a cross-sectional side view of a knee 200 is shown following resection of the popliteal surface 230, wherein the femoral component 12 is used in conjunction with a tibial component 14. In some examples, the above described femoral component 12 is used in conjunction with a conventional tibial component 14 that does not have the tibial full flex articulation. For example, the above described femoral component 12 is used in conjunction with a tibial component 14 that has the center of the medial tibial articulation displaced posteriorly. In another example, the femoral component 12 is used in conjunction with a tibial component 14 that has the center of the medial tibial articulation in a position that corresponds with currently available designs. In addition to occupying or lining the resectioned popliteal surface 230, the extended portion 212 may include additional features to modify the position of the tibia and the femur during full flexion.

For example, the extended portion 212 is modified to rotate the tibia relative to the femur with the knee in full flexion. In another example, the extended portion 212 is modified to prevent rotation of the tibia relative to the femur with the knee in full flexion. In yet another example, the extended portion 212 is modified to include a spherical surface on its upper or most proximal portion. As such, this spherical surface allows the tibia to rotate relative to the femur in full flexion. In some examples it may be desirable to have the spherical surface articulate with a corresponding concave surface in the femoral full flex articulation. Such a concavity would offer medial-lateral stability, provide area contact between the femoral and tibial components, and decrease polyethylene wear of the prosthesis. Referring again to <figref idref="f0037">Figure 23</figref>, in some examples, the femoral component 12 is used in conjunction with a non-resected posterior portion of the patient's own tibial plateau to articulate with extended portion 212.

Thus, as discussed herein, the embodiments of the present invention embrace knee prostheses. In particular, embodiments of the present invention relate to systems for providing deeper knee flexion capabilities for knee prosthesis patients, and more particularly, to: (i) providing a flexion attachment to the femoral component of a knee prosthesis or providing an extension of the femoral component, which when integrated with both the femoral component and a patient's femur, results in a greater articular surface area of the femoral component; (ii) making modifications to the internal geometry of the femoral component and the associated femoral bone cuts, (iii) providing asymmetrical condylar or articular surfaces on the tibial component of the knee prosthesis; (iv) making modifications to the tibial and femoral components of a knee prosthesis, including removing certain areas of the tibial and femoral components; (v) having asymmetric femoral condyles, including having a closing radius on the femoral component; and (vi) providing femoral and/or tibial full flex articulations, wherein all of the foregoing result in deeper knee flexion capabilities for knee prosthesis patients than previously achievable.

The present invention may be embodied in other specific forms and the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description.