Patch Rotation Hinge Knee Assembly, Subassembly, and Method

Abstract

To provide assemblies, systems, kits, and methods related to an endoprosthetic rotating hinge assembly.SOLUTION: The exemplary embodiments disclosed herein can comprise a preassembled rotating hinge subassembly having a hingedly rotating femur box configured to be mechanically engaged to a femoral component via a femur fastening mechanism, the femur fastening mechanism being non-axially aligned with a tibial axis of rotation when the knee is in flexion or extension.SELECTED DRAWING: Figure 3A

Description

Background Art

[0001] 1. Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 225,109, filed on July 23, 2021. The disclosure of this related application is incorporated herein by reference in its entirety.

Technical Field

[0002] 2. Technical Field The present disclosure generally relates to the field of knee implants, and more specifically to rotational hinge implants for revision and primary knee and methods of implanting them.

[0003] 3. Related Art Rotational hinge knee implants are typically used in revision knee surgery in situations where the patient's native ligaments and other retaining anatomical structures of the knee are severely damaged. Non - rotational hinge knee implants were initially used to replace the stabilizing function of the lost posterior cruciate ligament ( "PCL"). However, surgeons early on recognized that simple hinge knees tend to accelerate wear and failure. This problem has been addressed by providing a rotational hinge function such that the tibia rotates about the tibial axis generally perpendicular to the femur during flexion. Several designs have been used for this purpose. See, for example, U.S. Patent No. 6,773,461 and U.S. Patent No. 10,682,236.

[0004] Some of the drawbacks of conventional rotating hinge knees include that the hinge pin is often inserted from the side, requiring multiple incisions into the leg. Some hinge rotation assemblies, such as those disclosed in U.S. Patent No. 6,773,461, must be assembled during surgery. Such designs lengthen the duration of the procedure. The lengthening of the procedure duration similarly increases the risk of infection and other complications due to the time under anesthesia. Other designs, such as the rotating hinge assembly disclosed in U.S. Patent No. 10,682,236, require multiple locking mechanisms. Such mechanisms also lengthen the installation and overall procedure duration. Complex locking mechanisms are also difficult to reverse if the patient undergoes a revision surgery in the future.

[0005] Furthermore, the devices disclosed in both U.S. Patent No. 6,773,461 and U.S. Patent No. 10,682,236 have retaining elements that are inserted and disposed around the tibial rotation axis. During operation, lateral load-bearing elements, such as threads disposed around the tibial rotation axis, generally experience significant compressive forces from the femur. This is because the threads are combined with torsional forces that the knee joint may experience during normal bending and rotation, and these threaded elements (or their associated parts) may fail prematurely. Premature implant failure can result in further revision surgery that could be avoided by another method of fixing or replacing the implant. Replacing the entire implant often involves cutting the bone to which the implant was attached. Rotating hinge assemblies are frequently used in patients who are already suffering from significant bone deterioration. If insufficient bone remains, it may not be possible to further revise the failed rotating hinge assembly.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Accordingly, there is a need for an improved rotating hinge knee having the characteristics, features, and functionality described herein.

Means for Solving the Problems

[0008] The problems of long and complicated surgical implantation procedures, as well as the problems of rotating hinge implants that fail prematurely due to mechanical wear of the internal tibial alignment implant fastening elements, can be alleviated by an exemplary knee joint prosthesis assembly, which is a rotating hinge sub-assembly having a femoral box that can articulate in a hinged manner around a tibial yoke (e.g., via a lateral hinge pin), the femoral box being configured to be mechanically engaged with a femoral component via a femoral fastener, the femoral fastener being non-axially aligned with the rotational axis of the tibia when the knee flexes or extends, and the lateral hinge pin of the rotating hinge sub-assembly not being mechanically engaged with the femoral component in the installed configuration.

[0009] It is contemplated that certain exemplary embodiments disclosed herein may enable implantation of a rotating hinge knee through a single incision.

[0010] It is further contemplated that certain exemplary embodiments according to the present disclosure can provide a rotating hinge knee having a pre-assembled rotating hinge sub-assembly that is not pre-assembled with the femoral component or the tibial component of the prosthetic implant.

[0011] Certain exemplary embodiments according to the present disclosure can provide a rotating hinge knee having one femoral fastener for fixing the rotating hinge sub-assembly to the prosthetic femoral component, the femoral fastener engaging the femoral component in the parasagittal plane.

[0012] Furthermore, certain exemplary embodiments according to the present disclosure do not allow for excessive dislocation of the distal femur relative to the proximal tibia during the installation and assembly of the prosthesis implant, which further contemplates minimizing resection of the surrounding soft tissue, thereby contributing to the patient's rapid recovery.

[0013] Further exemplary embodiments disclosed herein may provide a rotating hinge knee having an extension stop for interacting with a femoral component.

[0014] The foregoing objectives are achieved by providing a rotating hinge knee implant assembly having the features described herein.

[0015] The foregoing will become apparent from the following more particular description of exemplary embodiments of the present disclosure, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, and instead, emphasis is placed on illustrating the disclosed embodiments.

Brief Description of the Drawings

[0016]

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DETAILED DESCRIPTION OF THE INVENTION

[0017] The following detailed description of the preferred embodiments is presented for purposes of illustration and description only and is not intended to be exhaustive or to limit the scope and spirit of the invention. The embodiments have been chosen and described in order to best explain the principles of the invention and its practical applications. One skilled in the art may recognize that many variations of the invention disclosed herein can be made without departing from the scope and spirit of the invention.

[0018] Unless otherwise specified, like reference numerals indicate corresponding parts throughout the several views. The drawings represent embodiments of various features and components according to the present disclosure, but the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate embodiments of the present disclosure, and such illustration should not be construed as limiting the scope of the present disclosure.

[0019] Unless expressly stated otherwise herein, (a) all terms used herein shall be construed to be of such gender or number (singular or plural) as the circumstances require, (b) the singular terms “a,” “an,” and “the” used in this specification and the appended claims shall include plural references unless the context clearly dictates otherwise, (c) the prefix “about” as applied to a recited range or value indicates an approximation of the deviation from the measured value within the range or value known or expected in the art, (d) the terms “herein,” “hereby,” “hereto,” “hereinbefore,” “hereinafter,” and like introductory terms refer to the entire specification and not to a particular paragraph, claim, or other subdivision unless specifically noted otherwise, (e) explanatory headings are for convenience only and do not control or affect the meaning of any part of this specification, and (f) the interpretation rules that “or” and “any” are not exclusive and that “include” and “including” are not limiting apply to this specification. Further, the terms “comprising,” “having,” “including,” and “containing” shall be construed as open-ended terms (i.e., meaning “including, but not limited to”).

[0020] References in this specification to “one embodiment,” “an embodiment,” “exemplary embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but that not all embodiments necessarily include that particular feature, structure, or characteristic. Further, such phrases do not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is presented that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0021] To the extent necessary to provide explanatory support, the subject matter and / or text of the appended claims are hereby incorporated by reference in their entirety into this specification.

[0022] The recitation of a range of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein. Each separate value falling within the recited range is incorporated into the specification or claims as if it were individually recited herein. When a particular range of values is provided, each intervening value, to the tenth of the unit of the lower limit between the upper and lower limits of that range, and any other recited value or intervening value within the recited range of that subrange, is included in the specification, unless the context clearly dictates otherwise. All subranges are also included. The upper and lower limits of these smaller ranges are also included therein, subject to any explicit and expressly excluded limits within the recited range.

[0023] Note that some of the terms used herein are relative terms. For example, the terms "upper" and "lower" are relative to each other in position, i.e., an upper component is located at a higher elevation than a lower component in each orientation, but these terms may change if the orientation is reversed. The terms "inlet" and "outlet" are relative to a fluid flowing therethrough for a given structure, e.g., a fluid flowing into the structure through an inlet and then out of the structure through an outlet. The terms "upstream" and "downstream" are relative to the direction in which a fluid flows through various components before flowing through a downstream component.

[0024] The terms "horizontal" and "vertical" are used to indicate absolute references, i.e., directions with respect to the ground level. However, these terms should not be construed as requiring that the structures be absolutely parallel or perpendicular to each other. For example, a first vertical structure and a second vertical structure are not necessarily parallel to each other. The terms "top" and "bottom" or "base" are used to indicate absolute references, i.e., with respect to the surface of the earth, where the top always refers to a position or surface higher than the bottom or base. The terms "upward" and "downward" are also relative to an absolute reference, and an upward flow is always against the gravity of the earth.

[0025] Throughout this disclosure, various positional terms such as "distal", "proximal", "medial", "lateral", "front", and "rear" are used in the conventional manner when referring to human anatomical structures. More specifically, "distal" refers to a region away from the point of attachment to the body, and "proximal" refers to a region near the point of attachment to the body. For example, the distal femur refers to the portion of the femur near the tibia, and the proximal femur refers to the portion of the femur near the hip joint. The terms "medial" and "lateral" are also essentially antonyms. "Medial" refers to something disposed at a position closer to the center of the body. "Lateral" means that something is disposed at a position closer to the right or left side of the body than the center of the body. With respect to "front" and "rear", "front" refers to something disposed at a position closer to the front of the body, and "rear" refers to something disposed at a position closer to the rear of the "body".

[0026] "Varus" and "valgus" are broad terms that include, but are not limited to, rotational movements in the medial and / or lateral directions with respect to the knee joint.

[0027] The phrase "mechanical axis of the femur" refers to an imaginary line drawn from the center of the femoral head to the center of the distal femur at the knee.

[0028] The phrase "mechanical axis of the tibia" refers to an imaginary line drawn from the center of the proximal tibia to the center of the distal tibia just above the ankle.

[0029] The term "anatomical axis" refers, as appropriate, to an imaginary line drawn longitudinally through the center of the femoral shaft or the tibial shaft.

[0030] In this specification, a hinge knee assembly, system, and method can be configured to be incorporated into matters similar to currently available primary and revision surgical techniques.

[0031] During a primary or revision surgery, the surgeon generally makes a midline incision perpendicular to the anterior side of the operative knee. The incision is generally made with the knee flexed at or below the tibial tubercle and can extend several inches above the patella.

[0032] In a primary TKA, the surgeon continues to incise through the adipose tissue to expose the anterior surface of the joint capsule. The surgeon then performs a medial parapatellar arthrotomy to penetrate the joint capsule and excise the medial retinaculum. A retractor is then commonly used to move the patella generally laterally to expose the distal condyles of the femur and the chondral menisci resting on the proximal tibial plateau. The surgeon then removes the menisci, measures and resections the distal femur and proximal tibia using instruments, and inserts a trial implant. The trial implant is generally a test prosthesis having the same functional dimensions as the actual prosthesis, but the trial implant is designed to be temporarily inserted and removed for the purpose of evaluating the fit of the actual prosthesis and for the purpose of evaluating the kinematics of the knee joint. When the surgeon is satisfied with the size of the trial implant and the kinematic characteristics of the knee joint, the trial implant is removed and the actual implant is inserted.

[0033] During the revision procedure, after the surgeon makes the initial incision, the surgeon may release the scar tissue around the patellar tendon. Next, the surgeon generally moves the patella or patellar implant laterally (i.e., pre-forms a subluxation), exposing the previously implanted implant, which typically includes a femoral component disposed on the distal femur, a tibial component disposed on the proximal tibia, and a meniscal insert disposed between the femoral component and the tibial component. Next, the surgeon removes the previously implanted implant.

[0034] It should be understood that the type of previously implanted implant may vary from case to case. The previously implanted implant may include a static spacer inserted into aligned intramedullary canals in the distal femur and proximal tibia to fix the knee joint, or a complex implant used to reconstruct a traumatized portion of the knee joint. However, common previously implanted implants include implants placed during primary TKA or previously revised implants. Various factors influence the decision to replace a previously implanted implant with a rotating hinge knee implant, but common factors may include excessive wear or non-function, the presence of trauma, progression of a bone degenerative disease, integrity of the underlying bone, and severe varus / valgus deformity. Common bone degenerative diseases include rheumatoid arthritis and osteoarthritis.

[0035] Previously implanted implants may be bonded to bone in various ways. Press-fit implants typically have a porous, rough surface on the connecting side of the femoral and tibial components. The porous surface allows bone to regrow into these ingrowths over time. Another very common bonding technique involves the use of antibiotic-infused grout, commonly known as "bone cement" by those in the orthopedic industry. It will be understood that "bone cement" is a term in the art even though the bone cement itself generally does not have adhesive properties. Bone cement generally relies on a close mechanical connection between the irregular surface of the bone and the surface of the prosthetic on the bonding side. Common bone cements include polymethylmethacrylate ("PMMA"), calcium phosphate cement ("CPC"), and glass polyalkenoate isomer cement ("GPIC").

[0036] Removal of previously implanted implants generally involves cutting the bone under the bone cement or, in the case of press-fit implants, the bone under the press-fit implant. This resection exposes fresh bone that can receive a revision press-fit or bone-cemented implant. If bone is removed to remove a previously implanted implant and the revision implant is not sized to replace the newly resected bone, the joint line will shift.

[0037] This tibial resection is typically coplanar with a transverse body plane orthogonal to the anatomical axis of the tibia. When resected, the resected area of the tibia may be known as the "tibial plateau." After previously implanted implants are removed, intramedullary reamers set to a series of different sizes are used to prepare or expand intramedullary perforations in both the tibia and femur to accommodate the tibial and femoral components of the revision implant, respectively. After reaming, the surgeon can use instruments to further measure and resect the proximal tibial plateau. Next, the surgeon may place the investigational tibial component on the resected proximal tibial plateau. The surgeon generally uses different instruments to measure and resect the distal femoral condyle for the purpose of installing the investigational femoral component. If the investigational component is not properly accommodated, the surgeon may use additional instruments to measure and resect the femoral condyle and / or tibial plateau until the desired accommodation is achieved.

[0038] The rotating hinge knee typically has a femoral box cavity (see FIG. 2A, 280) in the femoral component of the prosthetic implant (see FIG. 2A, 205). To accommodate the femoral box cavity, additional resection of the outside of the medial condyle and the inside of the lateral condyle is generally required. In other words, the surgeon creates a box-shaped notch in the center of the distal femur to accommodate the femoral box cavity of the femoral component of the implant. Failure to properly resect the distal femur can lead to an intercondylar fracture.

[0039] Next, the surgeon generally inserts the trial meniscal insert between the trial tibial tray and the trial femoral component to test the knee flexion and extension of the trial implant, overall stability, and patellar tracking. A metal block called an "augment" can be attached to the tibial or femoral component to replace missing or damaged bone. When satisfied with the trial and movement characteristics, the surgeon can permanently fix the actual tibial and femoral components of the prosthetic implant using a new, uncured antibiotic-impregnated bone cement, or, if desired, use a press-fit implant and avoid using bone cement.

[0040] Other rotating hinge knee systems differ from the present disclosure in that many other rotating hinge knee systems require an intraoperative lateral assembly of the hinge component. This intraoperative assembly requires additional resection of the outer surface of one or more femoral condyles to provide access to the hinge component (usually a pin). Some designs require additional posterior resection of the condyles. The additional resection prolongs the procedure and reduces the amount of remaining bone available for future revisions. It will also be appreciated that the additional but unnecessary lateral and / or posterior condyle resections prolong the patient's recovery time, introduce new areas that may become infected, and, particularly in the presence of existing bone deterioration, introduce areas of structural weakness. Any area of structural weakness increases the risk of catastrophic implant failure during normal use.

[0041] Also, the intraoperative assembly of a rotating hinge knee prolongs the procedure and increases the risk of infection and other complications caused by the increased time under anesthesia.

[0042] Some other rotating hinge knees use a retaining element having threads configured to be inserted and disposed about the tibial axis of rotation. Without being bound by theory, in operation, the lateral load-bearing elements disposed about the tibial axis of rotation are generally assumed to experience significant compressive forces from the femur. This, combined with the torsional forces that the threads may be subject to during normal flexion and rotation of the knee joint, can cause components having these threaded elements to fail prematurely, thereby requiring further revision surgery to replace either the worn components or the entire implant.

[0043] Furthermore, some other rotating hinge knees are not configured to limit five of the six degrees of freedom of the femoral and tibial components during implantation. The exemplary embodiments disclosed herein are intended to facilitate the alignment process by allowing a surgeon to align the femoral component with the rotating hinge subassembly without focusing on potential rotation of the femur or tibia during the alignment process (see FIGS. 2C, 10).

[0044] To reduce the implantation time compared to existing rotating hinge knees, an exemplary embodiment of the rotating hinge subassembly 10 described herein (see, e.g., FIG. 2C) can be pre-assembled into a self-contained module configured to be mechanically secured to the femoral component using a single femoral fastener 210.

[0045] As shown in the assembled front view of FIG. 1, a rotational hinge knee prosthesis implant assembly 1 according to the present disclosure generally includes a femoral component 205, a tibial component 105, a meniscus insert 150 disposed between the femoral component 205 and the tibial component 105, and a rotational hinge sub-assembly 10. In FIG. 1, many of the rotational hinge sub-assembly components are not clearly visible by the femoral component 205 and the tibial component 105, but some components, such as the femoral box 80 disposed in the femoral box cavity 280 (FIG. 2A) of the femoral component 205 and the head 24 of the tibial yoke 40, are visible. The bearing 60 is disposed between the head 24 and the femoral box 80 to facilitate the hinge movement of the rotational hinge knee prosthesis implant assembly 1. The femoral fastener 210 extends through the femoral box fixing bore 81 in the femoral box 80 and the femoral fixing bore 87 (FIG. 2A) in the femoral component 205 to fixedly engage the rotational hinge sub-assembly 10 with the femoral component 205. In the described embodiment, the femoral fastener 210 is a tapered screw, and the femoral box fixing bore 81 and the femoral fixing bore 87 are threaded to engage the corresponding screws of the tapered screw. In other exemplary embodiments, it is not necessary for either the femoral fixing bore 87, the femoral box fixing bore 81, or both the femoral fixing bore 87 and the femoral box fixing bore 81 to be threaded. An extension stop 30 may be provided to prevent excessive extension of the rotational hinge knee prosthesis implant assembly 1. In certain exemplary embodiments, the extension stop 30 may be a modular extension stop 30. That is, the surgeon can select and install one of the various extension stoppers available based on the specific anatomical structure of the patient.

[0046] The femoral component 205 includes an inner implant peg 218 disposed distally from the outer implant peg 219. FIG. 1 depicts each implant peg 218, 219 resting on the articular surface 151 (FIG. 2A) of the meniscus insert 150. The meniscus insert 150 is typically made of medical grade polyethylene (e.g., ultra-high molecular weight polyethylene (“UHMWPE”)) or other suitable clinically tested biocompatible materials. The base portion 101 of the tibial component 105 supports the meniscus insert 150. The base portion 101 is configured to rest on the resected tibial plateau of the patient (103, FIG. 2C). The tibial component 105 can be made of a biocompatible material such as a cobalt-chromium-molybdenum alloy, a titanium alloy, or other clinically proven high-strength biocompatible material. The tibial stem 102 extends downwardly from the distal side 106 of the tibial base portion 101. The tibial stem 102 is configured to be inserted into the intramedullary bore of the tibia 100 (see the depicted notch 109). The keel 127 facilitates the installation and fixation of the tibial component 105 into the intramedullary bore (see FIG. 2C) of the tibia 100 within the tibia 100. The depicted notch 109 is provided to show how the tibial component 105 can be accommodated within and on the proximal tibia 100 when installed. In practice, the depicted notch 109 should generally not be present. It will be appreciated that other tibial components 105 compatible with the exemplary assemblies described herein may lack the keel 127. In certain exemplary embodiments, the tibial stem 102 can be modularly configured to have different lengths of extension to accommodate intramedullary bores of different lengths, angles, or offsets relative to the cross-section 198 (FIG. 2D). In further exemplary embodiments, the keel 127 can be a modular component configured to engage fixedly with the tibial component 105.As can be better seen in FIG. 4, the tibial stem 102 is substantially hollow at least at its upper / proximal end and has an axial bore 104 configured to receive the longitudinal tibial axis post 20 of the rotary hinge subassembly 10 as further described below.

[0047] Desirably, the sleeve 120 is inserted into the axial bore 104 prior to insertion of the tibial axis post 20. The sleeve 120 prevents the tibial axis post 20, typically made of a biocompatible metal alloy, from rubbing inside the tibial stem 102, also typically made of a biocompatible metal alloy. In the absence of the sleeve 120, it is envisioned that repeated friction of the tibial axis post 20 moving towards the inside of the tibial stem 102 could generate metal debris that could compromise the effectiveness and integrity of the prosthesis. The sleeve 120 is contemplated to be made from ultra-high molecular weight polyethylene (UHMWPE), polyetheretherketone ("PEEK"), or other clinically proven biocompatible polymers. In other exemplary embodiments, the sleeve 120 can be made from ceramic materials including, but not limited to, zirconia toughened alumina ("ZTA") ceramic. In yet other exemplary embodiments, the sleeve 120 can be manufactured from a cobalt-chromium-molybdenum alloy, or a titanium alloy and coated with zirconium oxide or niobium nitride to further reduce the coefficient of friction between the articulating components and enhance durability. In this way, the sleeve 120 effectively creates a barrier between the inner wall of the tibial stem 102 and the outer wall of the tibial axis post 20.

[0048] Figures 2A - 2D provide a series of perspective views showing the major steps of implantation of the rotary hinge knee prosthesis assembly 1.

[0049] Figure 2A depicts the femoral component 205 oriented in a flexed manner with respect to the tibial component 105. The femoral box cavity 280 is disposed between the outer implant bead 219 adjacent to the inner implant bead 218. The femoral box cavity 280 is configured to receive the femoral box 80, as described below. In the depicted embodiment, the femoral component 205 includes a femoral fixation bore 87 that is exposed within the femoral box cavity 280. The femoral fixation bore 87 is secured to a transverse surface 92 that extends between the inner surface of the inner implant bead 218 and the outer implant bead 219. The meniscus insert 150 is disposed on the base 101 of the tibial component 105 in a rotatable or movable bearing configuration (see FIG. 3A for a discussion of an exemplary rotational bearing arrangement). Various configurations may be used for the connection between the meniscus insert 150 and the tibial base portion 101.

[0050] The femoral component 205 can be made from a biocompatible material such as a cobalt-chromium-molybdenum alloy, a titanium alloy, or other suitable high-strength biocompatible material. The articular surfaces (i.e., the inner implant bead 218 and the outer implant bead 219) can be optimally coated with a durable biocompatible material having a low coefficient of friction to provide a smooth articular bearing surface. Examples of such coatings include zirconium oxide or niobium nitride.

[0051] Figure 2B provides a perspective view of the rotational hinge subassembly 10 in the disengaged position, where the first articulating element (e.g., the femur box 80) is completely separated from the thigh component 205. One advantage of the exemplary embodiments of the present disclosure is that the rotational hinge subassembly 10 can be fully assembled before being inserted into the patient's knee, thus facilitating the implantation procedure and contributing to a reduction in surgical time. The pre-assembled rotational hinge subassembly 10 includes a yoke 40 and a femur box 80 that articulates in a hinged manner around the head 24 of the yoke 40. The femur box 80 depicted includes a femur box fixing bore 81. It will be appreciated that the femur box fixing bore 81 is an example of a thigh fastening mechanism that can be used to selectively engage the femur box 80 in the femur box cavity 280 of the thigh component. In other exemplary embodiments, the thigh fastening mechanism may include protrusions, recesses, receptacles, multiple protrusions, multiple recesses, multiple receptacles, part of a protrusion-receptacle locking mechanism, magnets, clamps, hooks, lips, welding agents, binders, adhesives, or combinations thereof. In other exemplary embodiments, the thigh fastening mechanism can include a pin inserted through the femur box fixing bore 81 and the femur fixing bore 87. In such exemplary embodiments, the surgeon can use a small hammer to deform the distal end of the inserted pin within the femur fixing section, thereby fixedly engaging the thigh fastening mechanism to the thigh component in the parasagittal plane z (see also FIGS. 11A and 13). In such embodiments, the femur fixing bore 87 may have a maximum diameter larger than the maximum diameter of the femur box fixing bore 81. The increase in volume of the femur fixing bore 87 relative to the femur box fixing bore 81 may allow the distal end of the pin to deform within the femur fixing bore 87, thereby locking the pin-femur fastener in a protrusion-receptacle locking manner. Without being bound by theory, it is contemplated that the elimination of threaded elements within the thigh fastener 210 may further mitigate the possibility of premature failure resulting from any small incidence of torsional force transfer to the thigh fastener 210.

[0052] In yet another exemplary embodiment, the thigh fastening mechanism may include magnetic elements of opposite polarities, where a first magnetic element is disposed within the femur box 80, and a second magnetic element of a polarity opposite to that of the first magnetic element is disposed within a lateral surface 92 extending between the inner implant beads 218 and the inner surfaces of the outer implant beads 219 of the thigh component 205.

[0053] The exemplary rotational hinge subassembly 10 may further include a modular extension stop 30 configured to snap-fit onto the extension stop portion 28 (FIG. 3A) of the yoke 40. One or more bearing members 60 are pivotally connected to a head 24 (e.g.) of the yoke 40 via a lateral hinge pin 50 (FIG. 4). The end 53 of the lateral hinge pin 50 is visible in FIG. 2B. The lower or bottom portion of the body 45 of the yoke 40 includes a tibial axial post 20 configured to be disposed within a tibial component 105 in a rotational relationship. The tibial axial post 20 includes a distal end 26. Details regarding these components are provided herein. It will be understood that in other exemplary embodiments, one bearing member 60 may be used. In yet other exemplary embodiments, three or more bearing members 60 can be used.

[0054] FIG. 2C depicts the thigh component 205 being fixed to the distal femur 200 and the tibial component 105 being fixed to the proximal tibia 100 of the patient's knee joint using the resection and implantation techniques described above. FIG. 2C shows the rotational hinge subassembly 10 immediately prior to insertion and attachment to the implant assembly (i.e., the thigh component 205, the meniscus insert 150, and the tibial component 105). As shown, the tibial axial post 20 is inserted into an axial bore (104, FIGS. 3A, 4) within the tibial stem 102. The femur box cavity 280 is sized and configured to allow the tibial axial post 20 to be inserted in a generally forward or upward to downward orientation when the femur 200 is flexed.

[0055] Figure 2D shows the rotary hinge sub - assembly 10 attached to the hinge femoral component by the femoral fastener 210. As can be understood from Figure 2D, with the knee in a flexed state, the tibial - axis post 20 of the yoke 40 (see also Figure 4) is inserted into the axial bore 104 of the tibial stem 102 in a rotational relationship R, and the femoral box 80 is seated within the femoral - box cavity 280. The femoral fastener 210 is inserted through the femoral - fixation bore 87 (i.e., the second joint element) within the femoral component 205 via the fixation bore 81 within the femoral box 80, and in this way, the femoral box 80 (i.e., the first joint element) is fixed to the femoral component 205. When the femoral fastener 210 fixes the femoral box 80 to the femoral component 205, the first joint element is in an engaged position. That is, the first joint element (e.g., the femoral box 80) is disposed within the femoral component 205 and engages the femoral component 205 in a projection - receiving - part locking manner.

[0056] In this way, the rotary hinge sub - assembly 10 is fixed to the femoral component 205 and can be said to be "fixedly engaged" with the femoral component 205. Selectively mechanically engaging the first joint element of the rotary hinge sub - assembly 10 with the femoral component 205 in a projection - receiving - part locking manner, a magnetic - locking manner, a clamp - locking manner, a coupling - locking manner, an adhesive - locking manner, or a combination thereof can also be said to "fixedly engage" the rotary hinge sub - assembly 10 with the femoral component 205.

[0057] The length of the tibial axis post 20 (see FIG. 3A), the surrounding soft tissue of the unexcised knee (e.g., the medial collateral ligament "MCL" and the lateral collateral ligament "LCL"), and the position of the femoral component 205 relative to the tibial component 105 effectively fix the tibial axis post 20 within the tibial component 105 while allowing the tibial axis post 20 to rotate about the tibial axis of the axis of rotation A during use. In this way, it can be said that the rotary hinge subassembly 10 is disposed in a hinged and rotatable configuration within the rotary hinge knee prosthesis implant assembly 1. That is, the rotary hinge knee prosthesis implant assembly 1 is enabled to pivot about the hinge component (i.e., "hinged joint movement", see also the hinge direction H of rotation about the lateral hinge pin 50 in FIG. 3B), thereby enabling the rotary hinge knee prosthesis implant assembly 1 to flex and extend as is readily apparent in normal use, and the femur 200 is also enabled to rotate slightly axially about the generally vertical tibial axis A of rotation as the rotary hinge knee prosthesis implant assembly 1 undergoes flexion and extension. The length L (FIG. 7A) of the tibial axis post 20 and the surrounding soft tissue prevents the yoke 40 from dislocating from the axial bore 104 of the tibial stem 102 when the knee is fully flexed. However, the distance between this distal end 26 of the tibial axis post 20 and the bottom of the tibial axis stem 102 can increase when the knee is fully flexed.

[0058] This axial rotation R of the femur 200 relative to the tibia 100 approximates the natural movement of the knee joint. Thus, the rotary hinge knee prosthesis implant assembly 1 avoids some of the wear forces that a fixed hinge knee would be expected to experience during normal use. The rotary hinge knee prosthesis implant assembly 1 better approximates the natural movement of a normal knee compared to a fixed hinge design, and thus the rotary hinge knee can improve the patient's postoperative comfort.

[0059] In other exemplary embodiments, the tibial axial post 20 can be fixedly engaged to the inside of the tibial stem 102 or the sleeve 120 (FIG. 4) to prevent dislodgment of the tibial axial post 20 from the axial bore 104 of the tibial stem 102. In such embodiments, the tibial axial post 20 can comprise an expandable element that can selectively extend radially away from the tibial axial post 20 to engage the inner surface of the tibial stem 102 or the sleeve 120 (whichever is present). In yet other exemplary embodiments, the inner side of the tibial axial post 20, the tibial stem 102, or the inner and outer sides of the sleeve 120 can have protrusions that abut adjacent elements when the tibial axial post 20 is installed inside the tibial stem 102 and fixedly engages a post member therein. In yet other exemplary embodiments, the tibial axial post 20 and the adjacent structure (e.g., the inside of the sleeve 120 or the tibial stem 102) can comprise magnets of opposite polarities.

[0060] Without being bound by theory, it is contemplated that such embodiments may be desirable in patients troubled by ligament laxity. Typically, the length L (FIG. 7A) of the installed tibial axial post 20 is combined with the tension from the relatively nominal surrounding soft tissues (including the MCL and LCL) to prevent the tibial axial post 20 from dislocating from the axial bore 104 of the tibial stem 102 when the knee is fully flexed. However, in patients suffering from ligament laxity, the MCL and LCL (and other surrounding soft tissues) may not exhibit sufficient tension to prevent dislodgment of the depicted tibial axial post 20 from the depicted sleeve 120 or from the inside of the tibial stem 102. Thus, fixedly engaging the tibial axial post 20 to the inside of the tibial stem 102 or engaging the sleeve 120 in the described manner may be desirable to prevent dislodgment.

[0061] Returning to FIG. 2D for reference, the depicted femur fastener 210 is a tapered screw. The depicted tapered screw is generally shorter than fasteners used in other rotating hinge knees. Further, the tapered screw having the threads disclosed in the exemplary embodiment is fixed to the femoral component 205, while some other rotating hinge assemblies are threaded to the tibial component.

[0062] Without being bound by theory, the significant compressive and torsional loads experienced by the tibia 100 and tibial component 105 during normal use of the knee can contribute to loosening of such tibial fastener elements and ultimately are assumed to potentially compromise the future stability and effectiveness of the prosthesis. In designs where the tibial fastener screw is locked, normal compressive and torsional forces can ultimately wear the threads, thereby also loosening the rotating hinge component and potentially compromising the effectiveness of the implant.

[0063] In embodiments according to the present disclosure, the condyles 218, 219 preferably transfer a majority of the femoral load (including the compressive load of the body described above, the femoral load including femoral and torsional loads) to the condyle pads 228, 229 of the meniscal insert 150. This is typically known as "condylar loading". The meniscal insert 150 then transfers the femoral load through the tibial component 105, the tibia 100, and ultimately to the patient's foot during normal use. In this way, the disclosed embodiments preferably avoid transferring excessive forces from the femur to the rotating hinge subassembly 10.

[0064] However, in reality, it is assumed that not all of the femoral loads are transferred to the knobs 228, 229 of the meniscal insert 150. Some of the compressive and torsional loads, as well as other loads such as varus, valgus, hyperextension, flexion, and anterior-posterior drawer forces, can be transferred from the femur 200 through the rotary hinge subassembly 10. In such cases, the femoral loads are assumed to be transferred from the femur 200 and the femoral component 205 to the femoral box 80 (i.e., the first joint element) and then through the lateral hinge pin 50 (FIG. 3A) to the head 24 and body 45 of the yoke 40 (FIG. 7A). The portion of the yoke body 45 disposed within the meniscal insert 150 then transfers these forces to the tibial component 105, the tibia 100, and ultimately to the patient's foot during normal use. Without being bound by theory, even in situations where forces are transferred to the rotary hinge subassembly 10, the lateral hinge pin 50 and the yoke 40 are assumed to transfer these forces through the remainder of the leg while avoiding transferring these forces to the femoral fastener 210. That is, the femoral loads are transferred through the femoral box 80, and in some cases, through the lateral hinge pin 50, rather than through the femoral fastener 210, as further described below. Embodiments according to the present disclosure contemplate that by positioning the femoral fastener 210 such that it mechanically engages the first joint element (e.g., the femoral box 80) with the femoral component 205 while removing the femoral fastener 210 from the force transfer chain, signs of cross-threading or other premature wear that would result from normal use of the fastener can be avoided. In certain exemplary embodiments, the position of the femoral fastener 210 or other femoral fastening mechanism that mechanically engages the femoral component 205 with the first joint element may desirably be coaxial with the tibial rotation axis A when the knee is extended (see FIG. 3A). Without being bound by theory, it is assumed that having the femoral component 205 coaxial with the tibial rotation axis A can further minimize torsion and other secondary loads on the femoral fastener 210 or other femoral fastening mechanism.

[0065] Figure 3A provides a cross-sectional extension view that can visualize a further aspect of the interconnection between components. The cross-section is taken along a parasagittal plane that separates the implant (see 400 in FIG. 13). The knee is shown fully extended (i.e., when the flexion degree is zero). In the described embodiment, when the rotating hinge knee prosthesis implant assembly 1 is extended, the tibial rotation axis A is substantially aligned (i.e., collinear) with the central axis F of the femoral fastener, but is not aligned when the rotating hinge knee prosthesis implant assembly 1 is flexed (see the central axis F of the femoral fastener with respect to the tibial rotation axis A in FIG. 3B). The vector of the central axis F moving towards the femoral component 205 of the femoral fastener can represent the engagement direction. The vector of the central axis F of the femoral fastener moving away from the femoral component 205 can represent the disengagement direction.

[0066] A modular extension stop 30 is provided. As will be discussed in more detail below, the modular extension stop 30 can be configured to snap-fit onto the extension stop portion 28 of the yoke 40. Extension stops are generally used to prevent recurrence. By modularizing the extension stop 30, it is envisioned that the surgeon can select the modular extension stop 30 that is most suitable for the patient's needs. Additionally, in some embodiments, the modular extension stop 30 may be omitted, and instead an extension stop fixed to the rotating hinge subassembly 10 in a fixed configuration may be provided. In such a case, the degree of potential hyperextension is limited by the patient's anatomical structure and the interaction between the beads 218, 219 of the femoral component 205 and the raised front surface of the meniscus insert 150.

[0067] As shown in FIG. 3A, the femur box 80 is fixed to the thigh component 205 by a femur fastener 210 that extends through a femur box fixing bore 81. Further, the femur box 80 and the bearing member 60 are hinged to the head 24 of the yoke 40 by a lateral hinge pin 50. In this way, the femur 200 rotates about a single lateral axis TR with respect to the head 24 of the yoke 40 (see H in FIG. 3B). With the tibial axis direction post 20 resting in the axial bore 104 of the tibial stem 102, the femur 200 can also rotate freely about the tibial rotation axis A, which is approximately the midline, with respect to the tibial component 105. The degree of rotation is limited by the patient's anatomical structure and the interaction between the meniscus insert 150 and the tibial component 102, which will be further described below. In the embodiment of FIG. 3A, the tibial axis direction post 20 passes through a through bore 108 (FIG. 4) formed in the meniscus insert 150 and enters the axial bore 104 of the tibial stem 102. In this way, the rotary hinge sub-assembly 10 in the engaged position fixes the meniscus insert 150 to the rotary hinge knee prosthesis implant assembly 1. In the embodiment of FIG. 3A, the modular extension stop 30 is configured to snap fit into an extension stop portion 28 in the body 45 of the yoke 40 in a fixed arrangement.

[0068] Figure 3A further depicts the base portion 101 of the tibial component 105, which further includes a front hook 128 and an intermediate hook 129. Each hook 128, 129 defines a negative space between the bottom of the hooks 128, 129 and the surface of the tibial base portion 101. The meniscus insert 150 has a front projection 131 and an intermediate projection 133 disposed on the base 111 of the meniscus insert. The front projection 131 and the intermediate projection 133 preferably fill the negative space defined by the bottoms of the front hook 128 and the intermediate hook 129 when the meniscus insert 150 is installed on the tibial base portion 101. In this way, the meniscus insert 150 is not only configured to snap-fit onto the tibial base portion, but also the arrangement of the hooks 128, 129 and the projections 131, 133 allows and restricts a rotational slide of the meniscus insert 150 about the approximate midline tibial axis of rotation A during normal flexion and extension of the rotating hinge knee prosthesis assembly 1.

[0069] If the surgeon selects such that the full length of the tibial axis post 20 is not dislocated from the tibial stem 102, the presence of the hinge subassembly 10 in the engaged position prevents the meniscus insert 150 from slipping out of the tibial component 105 when the knee is flexed and lifted during movement. Other ways of fixing the meniscus insert 150 to the tibial base 101 such that the meniscus insert 150 is rotatable about the approximate midline tibial axis of rotation A are considered to be within the scope of the present disclosure. The sleeve 120 can optionally, but preferably, be disposed on the tibial stem 102 between the tibial axis post 20 and the tibial stem 102. The sleeve 120 can fit snugly to the inner diameter of the tibial stem 102 and the outer diameter of the tibial axis post 20.

[0070] Figure 3B provides a side cross-sectional deep flexion view that can visualize a further aspect of the interconnection between components. The rotary hinge subassembly 10 can be configured to provide a deep flexion in the range of about 100 degrees to about 138 degrees, which is ideal for a revision knee. In certain exemplary embodiments, the range can be from about 100 degrees to about 125 degrees. In deep flexion, the maximum rotation of the tibial axial post 20 relative to the tibial component 105 is achieved, but is also limited by the hooks 128, 129, and the projections 131, 133 of the meniscus insert 150 and the tibial component 102. In addition to the pivotal movement, the femur 200 continues to hinge around the tibial axial post 20 only along the axis of the lateral hinge pin 50.

[0071] As shown in the side cross-sectional views of FIGS. 3A and 3B, the degree of translation of the tibial axial post 20 within the axial bore 104 during flexion is determined by the configuration of the condyles 218, 219 of the femoral component 205. If the condyles 218, 219 have a single fixed radius, the tibial axial post 20 does not translate significantly during flexion. Similarly, if the condyles 218, 219 have more than one radius, the tibial axial post 20 translates upward within the axial bore 104 during flexion.

[0072] Now, consider the aspects and features of the individual components of the rotary hinge knee prosthesis implant assembly 1.

[0073] Figure 4 provides an exploded view of one exemplary embodiment of the rotary hinge knee prosthesis implant assembly 1. Most of these components have been discussed above. However, additional components can be visualized in the exploded view that were not clear or visible in previous images. For a detailed overview of the components, refer to the other drawings.

[0074] Femoral box FIG. 5 shows a perspective view of one embodiment of a femur box 80 (i.e., an exemplary first joint element) for use with the rotational hinge knee prosthesis implant assembly 1 of the present disclosure. In the embodiment of FIG. 5, the femur box 80 generally has a clevis configuration. The femur box 80 includes a main body portion 91 on a front end portion 61 and a pair of opposing arms 82, 86 that extend rearwardly therefrom toward a rear end portion 52. In the depicted embodiment, the arms 82, 86 are in the form of clevis arms. The pair of opposing arms 82, 86 define a gap 57 between inner surfaces 90 of the opposing arms 82, 86. The gap 57 is sized to accommodate the width of the head 24 of the yoke 40 and desirably the width of any attached bearing member 60. The main body portion 91 of the femur box 80 is provided with a femur box fixing bore 81 that extends therethrough. Additionally, each of the opposing arms 82, 86 is provided with an arm bore 85, 88 (i.e., the first arm 82 defines a first arm bore 85 and the second arm 86 defines a second arm bore 88) that extends therethrough for receiving a lateral hinge pin 50 (FIG. 4). The arm bores 85, 88 are formed in their respective arms 82, 86. The pair of arm bores 85, 88 are substantially axially aligned with each other (along a lateral axis TR), thereby providing a continuous hinge pin bore across the opening between the arms 82, 86.

[0075] In certain exemplary embodiments, the femoral box 80 can be made from a durable, clinically proven biocompatible material that can support repeated force transfer from the femoral fixation mechanism over the life of the prosthetic implant 1. Exemplary materials include cobalt chromium molybdenum alloys and titanium alloys. In other exemplary embodiments, the femoral box 80 can be made from polyetheretherketone "PEEK", an organic thermoplastic polymer. PEEK is hydrophobic and reduces the risk of the thermoplastic resin fusing with bone. Such properties can contribute to reducing wear of the PEEK component over time. PEEK is also radiolucent and non-magnetic, thereby rendering the PEEK component transparent on radiographs and being compatible with magnetic imaging techniques.

[0076] In other exemplary embodiments, it is envisioned that the femoral box 80 can be made from other biocompatible, clinically proven articulating materials including, but not limited to, UHMWPE and ceramic materials, including but not limited to, zirconia toughened alumina ("ZTA") ceramic. If the femoral box 80 is manufactured from metal, it is further contemplated that the femoral box 80 can optionally be coated with zirconium oxide or niobium nitride to further reduce the coefficient of friction between the articulating components and increase durability. In such exemplary embodiments, it is contemplated that the outer surface of the femoral box 80, including the outer surfaces of the arms 82, 86, can be coated, preferably, to further reduce the coefficient of friction. For clarity, the femoral wall defining the box fixing bore 81 should not be coated with a friction reducing substance as such substances would facilitate removal of the femoral fastener 210 during normal use.

[0077] As shown in the drawings, the femur box 80 is sized and configured to accommodate all components of the hinge function. In an embodiment, the lateral hinge pin 50 is sized to flush-fit with the outer surfaces of the arms 82, 86. In certain exemplary embodiments, the edge 63 of the femur box 80 is rounded for non-obstructive assembly to the femur implant.

[0078] Without being bound by theory, by sizing the lateral hinge pin 50 to have an end 53 disposed flush or substantially flush with the outer surfaces 89 of the arms 82, 86, it is envisioned that the thigh component 205 can transfer any torsional forces from the femur 200 to the femur box 80 over the combined surface area of the outer surfaces 89 of the arms 82, 86 and the respective ends 53 of the lateral hinge pin 50. As used in this context, "flush" or "flush with" is understood to mean that the end 53 of the lateral hinge pin 50 is disposed substantially coplanarly with a plane that is coextensive with the outer surface 89 of one or both of the arms 82, 86.

[0079] It is envisioned that transferring any torsional force in this manner can distribute the torsional load over a larger area, thereby reducing the concentration of torsional load in any one area. Further, it is contemplated that a wider area distribution of any torsional load can reduce torsional wear and generally extend the service life of the exemplary embodiments described herein. In other exemplary embodiments, one or both ends 53 of the lateral hinge pin 50 are not flush with the outer surface 89 of the arms 82, 86. Rather, one or both ends 53 of the lateral hinge pin 50 extend into a pair of arm bores 85, 88 to allow the femur box 80 to rotate about the lateral axis TR of the lateral hinge pin 50, but remain within the pair of arm bores 85, 88, such that one or both ends 53 of the lateral hinge pin 50 do not extend beyond the outer surface 89 of the arms 82, 86. Such embodiments are envisioned to still provide the advantage of distributing torsional forces over a larger surface area than previously known.

[0080] Although the lateral hinge pin 50 is depicted as a separate element throughout the drawings (see, e.g., FIG. 4), in other exemplary embodiments, it will be understood that the inner side surfaces 90 of the arms 82, 86 may comprise a portion of the lateral hinge pin 50. In such exemplary embodiments, the inner end of the portion of the lateral hinge pin 50 extends away from the inner surface 90 of the first arm 82 and into the gap 57 between the opposing arms 82, 86. In the assembled configuration, the portion of the lateral hinge pin 50 extends into the lateral hinge bore 25 of the head 24 of the yoke 40, thereby hinge-engaging the first arm 82 of the femur box 80 to the yoke 40. Similarly, such exemplary embodiments may further comprise a second portion of the lateral hinge pin 50 that extends away from the inner surface of the second arm 86 (not visible in FIG. 5, see 90) into the gap 57 between the opposing arms 82, 86. In the assembled configuration, the second portion of the lateral hinge pin 50 extends into the lateral hinge bore 25 of the head 24 of the yoke 40, thereby hinge-engaging the second arm 86 of the femur box 80 to the yoke 40. In such exemplary embodiments with this modified femur box 80, it can be said that the femur box 80 “press-fits” or “interference-fits” into the lateral hinge bore 25 of the yoke 40. Further, in such exemplary embodiments, the arm bores 85, 88 may not be present.

[0081] Bearing member Figure 6 depicts an exemplary bearing member 60 sized to have a bearing surface that extends into the lateral hinge bore 25 of the head 24 of the tibial yoke 40. This bearing member 60 can rotate freely about the femoral box 80 and about the yoke head 24 and the lateral hinge pin 50 when disposed in the installed position (see FIG. 2). It can be appreciated that certain exemplary embodiments can comprise more than one bearing member 60. The bearing member 60 defines a bearing bore 75 configured to closely receive the lateral hinge pin 50 (or a portion of the lateral hinge pin 50). In this way, the lateral hinge pin 50 is supported by and rotates within the bearing bore 75. The end 53 of the lateral hinge pin 50 is disposed in the axially aligned arm bores 85, 88 of the femoral box 80. In this way, the femoral box 80 is configured to rotate hingedly about the lateral axis TR of the rotary hinge subassembly 10. Other embodiments achieve hinged rotation about the lateral rotation axis TR using a bearing sleeve that circumferentially abuts the lateral hinge pin 50 and extends through the arm bores 85, 88.

[0082] In other exemplary embodiments, it is understood that the inside of the bearing member 60 can include a portion of the lateral hinge pin 50. In such an exemplary embodiment, the inner end of the portion of the lateral hinge pin 50 extends away from the inner surface of the bearing member 60. In the assembled configuration, the portion of the lateral hinge pin 50 extends within at least one arm bore 85 and within the lateral hinge bore 25 of the head 24 of the yoke 40, thereby hingedly engaging the bearing member 60 to the femoral box 80 and the yoke 40. Also contemplated are multiple bearing members 60 each having a portion of the lateral hinge pin 50 extending from the inner surface. In such an exemplary embodiment with this modified bearing member 60, the portion of the lateral hinge pin 50 can be said to be a “press fit” or “interference fit” into the bearing member 60.

[0083] In an embodiment where the bearing member 60 is configured to be disposed between the side surface 84 of the yoke 40 and the inner surface 90 of the arm 86 of the femoral box 80, the bearing member 60 may include an inner hinge portion disposed on the opposite side from the outer hinge portion, and the inner hinge portion and the outer hinge portion are aligned coaxially with the transverse rotation axis TR in the assembled configuration. The outer hinge portion is disposed within the arm bore 88 of the arm 86 of the femoral box 80, and the inner hinge portion is disposed within the transverse hinge bore 25 of the yoke 40, thereby engaging the femoral box 80 hingedly with the yoke 40. Such an embodiment may further comprise a second bearing member 60 described as engaging the other arm 82 of the femoral box 80 hingedly with the yoke 40. In all such exemplary embodiments, the end 53 of the transverse hinge pin 50 preferably does not extend into the thigh component 205 in the installed configuration.

[0084] In certain exemplary embodiments, it is contemplated that the bearing member 60 may be made from a biocompatible clinically proven articulating motion material including, but not limited to, ceramic materials including cobalt chromium molybdenum alloy, titanium alloy, UHMWPE, PEEK, and zirconia toughened alumina ( "ZTA") ceramic. Further, if the bearing member 60 is manufactured from metal, it is envisioned that the bearing member 60 may optionally be coated with zirconium oxide or niobium nitride to further reduce the coefficient of friction between the articulating motion components and improve durability. In such exemplary embodiments, it is envisioned that the outer surface of the bearing member 60 may be coated, preferably, to further reduce the coefficient of friction. The bearing effectively creates a barrier between the femoral box 80 and the head 24 of the yoke 40. The zirconium oxide or niobium nitride coating preferably can substantially reduce the possibility of metal debris generated as a result of normal use that can occur by two metal components that generate shear forces relative to each other during normal movement.

[0085] Tibial yoke Figure 7A shows a side view of one embodiment of a prosthetic tibial yoke 40 (i.e., an exemplary second joint element) for use with a rotating hinge knee prosthetic implant assembly 1. In certain exemplary embodiments, the tibial yoke 40 has a unibody (i.e., a single continuous) structure having a body member 45 and a tibial axial post 20 extending downwardly from a second end 77 of the body member 45. The second end 77 of the body member 45 is disposed distally from a first end 67 of the body member 45. A head 24 extends from the first end 67 of the body member 45. The head 24 defines a lateral hinge bore 25 extending therethrough. In other exemplary embodiments, the tibial axial post 20 and the body member 45, or the body member and the head 24, may be separately manufactured components that are preferably assembled to the tibial yoke 40 prior to insertion into the rotating hinge knee prosthetic implant assembly 1.

[0086] As seen in the side view of FIG. 7A, the body member 45 extends away from a lateral rotation axis TR and provides an offset distance D between the lateral rotation axis TR of the lateral hinge bore 25 and the tibial rotation axis A of the tibial axial post 20. In certain exemplary embodiments, the inner diameter of the lateral hinge bore 25 is sized to receive the outer diameter of a region 97 of a bearing member 60 that defines a bearing bore 75 and is sized to articulate. The bearing bore 75 receives a lateral hinge pin 50 as described elsewhere herein. It will be understood that other ways of using the bearing member 60 to reduce the coefficient of friction between the femoral box 80 and the lateral hinge pin 50 are relevant to the scope of the present disclosure. In certain exemplary embodiments, the edge of the body member 45 is radial.

[0087] The tibial axis direction post 20 further comprises a distal end portion 26 disposed distally from the second end portion 77 of the main body member 45. The distal end portion 26 can be chamfered or otherwise configured to facilitate insertion of the tibial axis direction post 20 into the axial bore 104 of the tibial stem 102. In certain exemplary embodiments, the distal end portion 26 can include a conical tip. In other exemplary embodiments, the distal end portion 26 can be substantially hemispherical. In still other exemplary embodiments, the distal end portion 26 can be selected from a group of shapes including generally convex shapes, chamfered shapes, convex conical shapes, convex hemispherical shapes, and convex frustum shapes. In certain exemplary embodiments, the tibial axis direction post 20 can define a post member chamber 23, whereby it is hollow (see FIG. 7C).

[0088] FIG. 7D is a bottom view of an exemplary tibial yoke 40 depicting the distal end portion 26 of the tibial axis direction post 20, the main body 45 of the yoke 40, and the first and second side surfaces 83, 84.

[0089] In certain illustrative embodiments, the body member 45 includes an extension stop portion 28 (FIGS. 7B, 7C) that extends to the uppermost portion of the body member 45 between the head 24 and the tibial axis post 20. As shown in FIG. 7A, in an embodiment, the offset distance D between the tibial rotation axis A of the midline of the tibial axis post 20 and the parallel axis P that extends orthogonally through the transverse axis TR of the transverse hinge bore 25 is from about 12 mm to about 15 mm. The offset distance D defines the center of rotation of the femur 200 relative to the tibia 100. Certain illustrative embodiments may position the center of rotation of the modified femur slightly forward of the center of rotation of the native femur. In these illustrative embodiments, it has been discovered that enabling the femur to rotate more forwardly can contribute to better load sharing and force transfer away from the femur fixation mechanism. In situations where a plurality of yokes 40 are provided, the plurality of yokes 40 may have different size dimensions including different offset distances D. The surgeon may select an appropriately sized yoke 40 having an appropriate offset distance D based on the size and integrity of the patient's particular anatomical structure. The extension stop portion 28 is configured to receive and connect to a separate modular extension stop 30 as described herein. The mechanism for connecting to the modular extension stop 30 can include snap-fit pockets 29 formed in the upper surface of the modular extension stop portion 28 for receiving corresponding lock tabs 32A, 32B (FIG. 8B) of the modular extension stop 30.

[0090] Modular extension stop Figures 8A - 8C show views of one embodiment of an extension stop 30 for use with an exemplary rotating hinge knee prosthesis assembly 1. The modular extension stop 30 can be in an uninstalled position where the modular extension stop 30 is not engaged with the rotating hinge sub - assembly 10. The modular extension stop 30 can also be in an engaged position where the modular extension stop is engaged with the extension stop portion 28 of the rotating hinge sub - assembly 10. In FIG. 8A, it can be seen that the modular extension stop 30 has a substantially flat or flat uppermost surface 34 on the posterior side. In the embodiment depicted in FIG. 10, the uppermost surface 34 rises into the abutment portion 36. The abutment portion 36 fits into the patellar groove of the femoral component 205 when the knee is extended. In certain exemplary embodiments, the abutment portion 36 can have a concave front portion that continues the patellar groove of the femoral component 205 when the knee is extended. In this way, the exemplary modular extension stop 30 can be configured to fit into the patellar groove of the femoral component 205 and continue the patellar groove defined by the femoral component 205, which allows for a smooth transition between extension and flexion (see FIG. 12). The dip 39 separates the uppermost surface 34 from the abutment portion 36. This dip 39 prevents excessive extension of the femoral component 205 (e.g., negative flexion, or bending of the knee in the wrong direction).

[0091] In FIG. 10C, a front view of one embodiment of a modular extension stop 30 for use with an exemplary rotating hinge knee implant assembly of the present disclosure is disclosed.

[0092] The modular extension stop 30 can be made of a durable plastic material such as UHMWPE. The modular extension stop 30 can be provided in different configurations to allow for various degrees of hyperextension, such as - 10°, - 5°, - 3°, and 0° hyperextension. In this way, a surgeon can easily customize the modular extension stop 30 for an individual patient.

[0093] In an embodiment, the modular extension stop 30 is configured to snap-lock into the extension stop portion 28 of the tibial axis post 20. In the embodiments shown in FIGS. 10A, 10B, and 10C, the snap-lock mechanism can include a first snap member 32A disposed adjacent to a second snap member 32B. The snap members 32A, 32B can bend around their respective snap member stems 38A, 38B. The snap members 32A, 32B can fit into the snap-fit pocket 29 of the extension stop portion 28 of the yoke 40 when the modular extension stop 30 is in the installed position. FIGS. 8A, 8B, and 8C depict alternative snap-fit members 32A, 32B that do not bend around the snap-fit stem 38. Similar to the embodiments shown in the embodiments shown in FIGS. 10A, 10B, and 10C, the snap members 32A, 32B of FIGS. 8A, 8B, and 8C can fit into the snap-fit pocket 29 of the extension stop portion 28 of the yoke 40 when the modular extension stop 30 is in the installed position. All protrusion-receiving locking structures that can selectively and mechanically engage the modular extension stop 30 to the extension stop portion 28 of the yoke 40 are considered to be within the scope of the present disclosure.

[0094] In other exemplary embodiments, the extension stop 30 is not modular; rather, the extension stop 30 is always integrally connected to the yoke 40. In such embodiments, the extension stop 30 can be manufactured as part of the yoke 40 or the extension stop 30 can be permanently fixed to the extension stop portion 28 in a manner that prevents replacement of the extension stop 30 on the yoke 40 during surgery.

[0095] Tapered head fastener FIG. 9 shows a top perspective view of one embodiment of a femur fastener 210 for use with the rotational hinge knee prosthesis assembly 1 of the present disclosure. In the illustrated embodiment, the femur fastener 210 includes a threaded tip 211, a tapered head 212 on the rear end 215, and a smooth shank portion 214 between the threaded tip 211 and the tapered head 212. The thread 216 is typically a machined thread. The thread 216 of the threaded portion approaching the threaded tip 211 is preferably chamfered or tapered to facilitate the installation of the femur fastener 210 into the femur box fixing bore 81. That is, the diameter of the femur fastener 210 at the threaded tip 211 is preferably smaller than the inner diameter of the femur fixing bore 87. By guiding the threaded tip 211 of the femur fastener 210 with a relatively smaller diameter into the femur fixing bore 87 with a relatively larger diameter, it is made possible even with low accuracy when the surgeon first inserts the threaded tip 211 of the femur fastener 210 into the femur fixing bore 87, thereby facilitating the engagement of the femur box 80 to the femoral component 205 via the femur fastener 210.

[0096] To eliminate the possibility of cross-threading, the surgeon can preferably start inserting the femur fastener 210 (when the femur fastener 210 has the thread 216) by first rotating the femur fastener 210 in the direction opposite to the engagement direction. This allows the thread at the tip of the femur fastener 210 to finally fall under the edge of the tip of the thread of the femur fixing bore 87. Thereby, an audible click may occur and the surgeon only needs to register the sudden change in position. When the surgeon registers the click or the engagement of the thread, the surgeon can then start rotating the femur fastener 210 in the engagement direction.

[0097] When the femur fastener 210 is threaded into the femur fixation bore 87 of the femoral component 205, the tapered head 212 is automatically locked into the femur box fixation bore 81 to prevent the femur fastener 210 from backing out of the femoral component 205. The tapered locking configuration of the femur fastener 210 enables the distal assembly of the rotating hinge knee prosthesis implant assembly 1. The "distal assembly" means an assembly on the femoral component 205 that is fixed to the distal portion of the patient's resected femur 200 by this point in the implantation procedure. By bending the knee during the installation procedure of the subassembly, it is envisioned that the surgeon may have improved access to the femur box cavity 280 compared to other hinge knee prostheses that particularly require the hinge component to be fixed to the tibial component 105. The tibial component 105 may be more obstructed by the patient's soft tissue by this stage. In certain exemplary embodiments, the self-locking taper angle is 8 degrees, but different tapers such as taper angles between 8 and 12 degrees, including 8 and 12 degrees, can be used.

[0098] The femur fastener 210 can be manufactured from any clinically proven biocompatible material. Such materials include, but are not necessarily limited to, cobalt-chromium-molybdenum alloys and titanium alloys. It should be understood that the femur fastener 210 can comprise any device configured to fixedly engage the femur box 80 to the femoral component 205. Such devices can include pins with protruding elements, pins with negative elements configured to receive elements protruding from the femur box 80 or other interlocking assemblies, bolts, rivets, clamps, interlocking teeth, interlocking hooks, and other protrusion-receiving locking mechanisms configured to fixedly engage the femur box 80 to the femoral component 205 and configured such that the femur fastener 210 does not receive the load of the femur 200, but are not necessarily limited thereto.

[0099] Furthermore, without being bound by theory, the exemplary embodiments disclosed herein contemplate that the femoral load (i.e., the weight of the femur and the body above the femur due to gravity) is transferred primarily from the femur 200 and the femoral component 205 to the ball pads 228, 229 of the meniscus insert 150.

[0100] However, in situations where a subset of the femoral load is transferred to the rotational hinge subassembly 10, it is envisioned that the force is transferred from the femur 200 and the femoral component 205 to the femur box 80, the lateral hinge pin 50, and the head 24 and body 45 of the yoke 40. The bottom of the body 45 of the yoke 40 then transfers this load to the tibial component 105, the tibia 100, and ultimately to the patient's foot when standing or walking. The femoral load may also include the torsional loads that the tibia experiences during normal movement motions. The femoral load is not transferred to the femoral fastener 210. Thus, the femoral fastener 210 can be made shorter than to secure a fastener configured to be axially aligned with the tibial axis of rotation. In an exemplary embodiment, the length of the femoral fastener 210 can be, for example, about 14 mm. Other compatible femoral fasteners 210 can have lengths in the range of about 10 mm to about 18 mm.

[0101] Transferring the femoral load through components other than the femoral fastener 210 configured to mechanically connect the rotational hinge subassembly 10 to the femoral component 205 can, in addition to facilitating the placement of the prosthesis, extend the useful life of the prosthesis beyond conventional models. In some embodiments, the fact that the femoral fastener 210 can be a single femoral fastener 210 and that the femoral fastener 210 can be inserted through the femur box 80 into the femoral component 205 can contribute to an overall reduction in the time required to perform the surgical procedure.

[0102] Femoral component In an embodiment, the femoral component 205 has features for improved joint function. The femoral stem 155 is typically inserted into the femoral bore to mount the femoral component 205 on the resected femoral condyle. The femoral component 205 is configured to provide flexion beyond 120 degrees. The femoral component 205 may be configured to provide continuous patellar kinematics. In certain exemplary embodiments, a femoral box cavity 280 (FIG. 2A) having a length of about 16 to about 18 mm is provided for the femoral box 80 of the rotary hinge subassembly 10. The femoral component 205 may be configured to be compatible with existing revision components such as femoral augmentations, offset adapters, and modular stems, as well as modular extension stops 30.

[0103] In certain embodiments, both condyles 218, 219 can have a constant radius of curvature. Thus, ball and socket functions can be provided on both sides. In other embodiments, the condyles 218, 219 can include multiple radii, thereby defining a J-curve.

[0104] Tibial component Referring to FIG. 4, the tibial component 105 includes a mating axial bore 104 for receiving the tibial axial post 20.

[0105] The meniscal insert 150 can be adapted to a mobile bearing mechanism. Structural features for capturing the meniscal insert 150 in a mobile bearing relationship are provided on the proximal side / upper side of the tibial base portion 101, such as hook features further described with reference to FIGS. 3A and 3B.

[0106] Method of use During operation, the rotary hinge knee prosthesis implant assembly 1 of the present disclosure is designed to enable distal fixation of the rotary hinge subassembly 10 using an anterior approach.

[0107] The rotational hinge subassembly 10 can be configured to be pre-assembled rather than pre-assembled with the femur or tibia as in previous systems, as shown in Figure 2B.

[0108] After the femoral component 205 and the tibial component 105 are implanted, the rotational hinge subassembly 10 is inserted and rotated to a predetermined position within the femoral component 205. A single tapered head femur fastener 210 can then be inserted to connect the hinge subassembly 10 to the femoral component 205.

[0109] As can be seen from the foregoing description, the exemplary embodiments of the present invention have various advantages over conventional implants and methods, including but not limited to the following.

[0110] The rotational hinge subassembly 10 is configured to be pre-assembled by itself rather than assembled with the femoral or tibial component as in previous systems. The lateral hinge pin 50 has a single insertion point. After the femoral component 205 and the tibial component 105 are implanted, the tibial axial post 20 of the rotational hinge subassembly 10 is inserted into the axial bore 104 of the tibial component 105. The rotational hinge subassembly 10 can then be rotated to a predetermined position and the femur box 80 can be fitted into the femur box cavity 280 of the femoral component 205. This configuration allows for a large post length L of the tibial axial post 20 without requiring excessive repositioning of the femoral component 205 and the tibial component 105 of the rotational hinge knee prosthesis assembly 1, which in turn allows for more preservation of the surrounding soft tissue. Preserving the surrounding soft tissue can contribute to shortening the recovery time. The exemplary yoke 40 can have a post length L of about 40 mm to about 70 mm. Additionally, since the lateral placement of the hinge pin is eliminated, the implant configuration allows for a surgical method that requires only one incision to install the rotational hinge knee prosthesis 1.

[0111] Without being bound by theory, certain exemplary embodiments disclosed herein may be combined with surgical practice to constrain five of the six degrees of movement of the tibial component 105 and the femoral component 205, thereby enabling a surgeon to pre-align the tibial component 105 and the femoral component 205 along one plane of motion to facilitate implantation. In practice, it will be understood that the femur 200 and the tibia 100 each include six basic directions of movement. That is, all movements of the femur 200 and the tibia 100 (and thus any component disposed on the femur or tibia) can be reduced to a sum of movements along six basic directions of movement.

[0112] As shown in FIG. 11A (and prior to the installation of the rotary hinge subassembly 10), the femoral component 205 and the tibial component 105 can move relative to each other according to six basic directions of movement. That is, the femoral component 205 can move laterally (and vice versa) relative to the tibial component 105 (i.e., in the anteroposterior direction x, in the rotational direction a about the anteroposterior axis A-P, in the medial lateral direction y, in the rotational direction b about the medial lateral axis M-L, in the superior-inferior direction z along the parasagittal plane, and in the cross-section (see 198 in FIG. 2D) along the rotational direction c about the inferior-superior axis U-D of the parasagittal plane).

[0113] The exemplary method includes placing the tibial axis post 20 of the yoke 40 into the axial bore 104 of the tibial stem 102 while the knee is flexed. The practice of aligning the femoral box cavity 280 of the femoral component 205 with the femoral box 80 effectively restricts five of the six basic movement directions of the femoral component 205 with respect to the tibial component 105 to the extent that the femoral component 205 is typically movable mainly upward and downward along the parasagittal plane z. Any movement in the anterior-posterior direction x or about the medial-lateral axis on the cross-section b, if present, is considered to be minimal. The hands and instruments can be used to restrict the range of motion of the femur and tibia and align the femoral box cavity 280 of the femoral component 205 with the femoral box 80 of the rotary hinge subassembly 10.

[0114] FIG. 11B depicts the rotary hinge subassembly 10 in the engaged position. That is, the first joint element is disposed within the femoral component and engages the femoral component in a projection-receiving locking manner.

[0115] In an embodiment, the modular extension stop 30 is configured to interact with the thigh component 205. The modular extension stop 30 can have a variable size and is configured to snap fit into the body 45 of the yoke 40, enabling inventory reduction. The variable size of the modular extension stop 30 can also be selected to correspond to the anatomical structure of a particular patient (e.g., the modular extension stop 30 can be customized based on preoperative images taken during the preoperative planning phase, or the modular extension stop 30 can be selected from existing options of the modular extension stop 30 provided in the kit). Such a modular extension stop 30 can be further selected to address specific deficiencies in the patient's anatomical structure and prevent recurrence. The modular extension stop 30 has lock tabs 32A, 32B that extend from the bottom of the modular extension stop 30, and the lock tabs 32A, 32B extend into snap fit pockets 29 of the extension stop portion 28 of the yoke 40 when the modular extension stop 30 is in the installed position.

[0116] One tapered head femoral fastener 210 connects the rotary hinge subassembly 10 to the thigh component 205. The use of a single fastener simplifies the assembly and reduces the risk of components loosening from each other during use.

[0117] The components of the Rotating Hinge Knee Prosthesis Implant Assembly 1 may be provided in the form of a surgical kit. The kit components are preferably arranged in a convenient format such as a surgical tray or case. However, the kit components need not be packaged or shipped together, provided that they are assembled or collected together in the operating room for use during surgery. An exemplary kit may include nine Rotating Hinge Subassemblies 10. In one particular exemplary kit, the exemplary yoke 40 may have a tibial axial post 20 having one of three lengths L. Such an exemplary yoke 40 may have a body 45 having one of three sets of dimensions. The nine Rotating Hinge Subassemblies 10 represent an array and combination of tibial axial post lengths L and the dimensions of the body of the tibial yoke 40. Each Rotating Hinge Subassembly 10 may preferably have a different offset distance D and post length L than the other Rotating Hinge Subassemblies 10 within the kit.

[0118] Exemplary kits can include any suitable embodiment of the rotational hinge subassembly 10 according to one embodiment, variations of the rotational hinge subassembly 10 described herein, and any other rotational hinge subassembly 10. Exemplary kits can further include one or more modular extension stops 30, one or more tibial components 105, and one or more femoral components 205, although it is understood that a particular kit may lack some or all of these elements. Any suitable embodiment of the modular extension stop 30, variations of the modular extension stop 30 described herein, and any other modular extension stop 30 according to an embodiment are considered to be within the scope of the present disclosure. Any suitable embodiment of the tibial component 105, variations of the tibial component 105 described herein, and any other tibial component 105 according to one embodiment are considered to be within the scope of the present disclosure. Any suitable embodiment of the femoral component 205, variations of the femoral component 205 described herein, and any other femoral component 205 according to one embodiment are considered to be within the scope of the present disclosure.

[0119] The selection of the number or type of rotational hinge subassembly 10, modular extension stop 30, tibial component 105, and femoral component 205 suitable for inclusion in a kit according to a particular embodiment can be based on various considerations such as the procedure intended to be performed using the components included in the kit.

[0120] FIG. 12 depicts a cross-sectional side view of an exemplary embodiment with different modular extension stops 30. The cross-sectional view is obtained from a parasagittal plane that vertically bisects the rotating hinge knee prosthesis assembly 1. As can be seen, at zero flexion, the patellar groove 115 of the femoral component 205 is sized and configured to abut against the extension stop 30. In this way, the rotating hinge knee prosthesis assembly 1 cannot move into hyperextension or exceed the built-in degree of hyperextension. In the exemplary embodiment of FIG. 12, the femoral fixation mechanism (i.e., the femoral fastener 210 in the depicted embodiment) is misaligned non-axially with the rotational tibial axis A when the rotating hinge knee prosthesis assembly 1 is fully extended. That is, the central axis F of the femoral fastener is not aligned with the rotational tibial axis A. This misalignment when the knee is extended is expected to further reduce the transfer of any torsional forces from the femur 200 to the femoral fixation mechanism, thereby reducing the occurrence of wear in the femoral fixation mechanism during normal use.

[0121] Figure 13 is a schematic perspective view of anatomical planes relative to human 600. Cross-sectional plane 198 is shown as extending across human 600. Cross-sectional plane 198 is shown as horizontally bisecting human 600 at the midpoint of the human, but it should be understood that cross-sectional plane 198 is an imaginary plane that can be imagined as horizontally existing anywhere on human 600 between a medial point and a lateral point disposed distally along the shortest possible line. Thus, cross-sectional plane 198 can be said to divide human 600 into an upper portion and a lower portion. Sagittal plane 400 is shown as vertically bisecting human 600 in the anterior-posterior direction through the midpoint. Sagittal plane 400 is shown as bisecting the human, but it should be understood that sagittal plane 400 is an imaginary plane that can be imagined as vertically existing anywhere on human 600 between a posterior point and an anterior point disposed distally along the shortest line. Thus, sagittal plane 400 divides the human into left and right. A sagittal plane 400 that is not disposed at the center of human 600 is generally known as a sagittal plane (see z in FIG. 11A). Coronal plane 500 is shown as vertically bisecting human 600 through the midpoint. Coronal plane 500 is shown as bisecting the human, but it should be understood that coronal plane 500 is an imaginary plane that can be imagined as vertically existing anywhere on human 600 between a medial point and a lateral point disposed distally along the shortest possible line. Thus, coronal plane 500 divides the human into an anterior portion and a posterior portion.

[0122] An exemplary knee prosthesis comprises a tibial component, a femoral component, and a rotating hinge sub-assembly. The rotating hinge sub-assembly is configured to be coupled to the femoral component and disposed on the tibial component, and is rotatable about a rotation axis within the tibial component. The rotating hinge sub-assembly includes a first joint element and a second joint element that is rotatable about the rotation axis and coupled to the first joint element. The first joint element defines an engagement position where the first joint element is disposed within the femoral component and engages the femoral component in a projection-receiving locking manner, and a disengaged position where the first joint element is completely separated from the femoral component. The first joint element defines an engagement direction and is movable relative to the femoral component to transfer the first joint element from the disengaged position to the engagement position. The engagement direction runs transversely to the rotation axis, and the projection and receiving elements of the projection-receiving locking manner extend non-parallel to the engagement direction.

[0123] An exemplary rotating hinge sub-assembly includes a tibial yoke defining a lateral hinge bore extending through a first side surface and a second side surface of a head, a tibial axial post extending away from the head, and a body member disposed between the head and the tibial axial post, the body member separating the head by an offset distance from the tibial axial post; a femoral box including a first arm and a second arm extending rearward from a main body portion, the main body portion defining a femoral box fixing bore extending through the main body portion, the first arm and the second arm respectively defining a first bore and a second bore that are axially aligned, the first arm being disposed adjacent to a first side surface and the second arm being disposed adjacent to a second side surface such that the first bore and the second bore are axially aligned with the lateral hinge bore; and a lateral hinge pin extending through the lateral hinge bore into the first bore and the second bore.

[0124] An exemplary rotational hinge subassembly includes a tibial yoke comprising a head defining a lateral hinge bore extending through a first side surface and a second side surface of the head, a tibial axial post extending away from the head, and a body member disposed between the head and the tibial axial post, the body member separating the head by an offset distance from the tibial axial post; a femoral box comprising a first arm and a second arm extending rearwardly from a main body portion, the main body portion defining a femoral box fixing bore extending through the main body portion, the first arm and the second arm defining a first bore and a second bore that are axially aligned, the first arm being disposed adjacent to the first side surface and the second arm being disposed adjacent to the second side surface such that the first bore and the second bore are axially aligned with the lateral hinge bore; and a lateral hinge pin extending through the lateral hinge bore into the first bore and the second bore, the lateral hinge pin not extending beyond the arms of the femoral box.

[0125] An exemplary knee prosthesis includes a tibial component and a femoral component, the femoral component having a region defining a femoral receiving bore, and a pre-assembled rotational hinge sub-assembly configured to couple the tibial component to the femoral component for rotation about a rotational axis. The pre-assembled rotational hinge assembly includes a first joint element and a second joint element rotatable about the rotational axis and coupled to the first joint element. The first joint element has a region defining a first receiving bore. The first joint element has an engaged position where the first joint element is disposed in the femoral component such that the first receiving bore and the femoral receiving bore are aligned and a fastener extends through the first receiving bore and the femoral receiving bore, and a disengaged position where the first joint element is completely separated from the femoral component. The first joint element defines an engagement direction, and the first joint element is movable relative to the femoral component to move the first joint element from the disengaged position into the engaged position. The engagement direction runs transverse to the rotational axis, and the femoral bore extends in a non-parallel manner in the engagement direction.

[0126] In such an exemplary embodiment, the first joint element can be a femoral box. Such an exemplary embodiment can further include an extension stop.

[0127] An exemplary rotational hinge knee prosthesis implant assembly includes a rotational hinge subassembly having a femoral box configured to articulate hingedly about a tibial yoke via a laterally extending hinge pin, the tibial yoke comprising a body member having a head disposed at a first end thereof, and a tibial axial post extending from a second end of the body member, the second end of the body member being disposed distally from the first end of the body member, the rotational hinge subassembly further comprising a femoral box configured to mechanically engage with a femoral component via a femoral fastener, the femoral fastener being configured to be non-axially aligned with the axis of rotation of the tibia when the knee is flexed (e.g., when the rotational hinge knee prosthesis implant is hingedly rotating about the lateral pin at a flexion angle greater than 0 degrees) or extended (e.g., when the rotational hinge knee prosthesis implant is hingedly rotating about the lateral pin at a flexion angle less than or equal to 0 degrees), and the laterally extending hinge pin of the rotational hinge subassembly being configured not to mechanically engage with the femoral component in the installed configuration.

[0128] An exemplary prosthetic tibial yoke for a rotational hinge subassembly includes a body member having a head disposed at a first end thereof, and a tibial axial post extending from a second end of the body member, the second end being disposed distally from the first end, the head defining a lateral hinge bore extending through a first side surface and a second side surface of the head, the lateral hinge bore defining a lateral axis extending laterally therethrough, the tibial axial post defining a midline axis extending longitudinally therethrough, a reference axis extending substantially orthogonally through the lateral axis and being substantially parallel to the midline axis, and an offset distance separating the midline axis from the reference axis.

[0129] In an exemplary embodiment of the tibial yoke, the tibial axial post, the body member, and the head are of a single continuous structure.

[0130] In an exemplary embodiment of the tibial yoke, the tibial axis post further comprises a distal end disposed distally from the second end of the body member. In such an exemplary embodiment, the distal end can have a shape selected from the group consisting of an essentially convex shape, a chamfered shape, a convex conical shape, a convex hemispherical shape, and a convex frustum shape.

[0131] In an exemplary embodiment of the tibial yoke, the offset distance is essentially selected from the range of distances consisting of about 12 mm to about 15 mm.

[0132] In an exemplary embodiment of the tibial yoke, the tibial axis post further includes a post length, and the post length has a value of about 40 mm to about 70 mm.

[0133] An exemplary tibial yoke can further include an extension stop portion extending between the head and the tibial axis post, and the extension stop portion includes a snap-fit pocket. In such an exemplary embodiment, the tibial yoke can further include a modular extension stop having a lock tab extending from the bottom of the modular extension stop, and the lock tab is configured to extend into the snap-fit pocket of the extension stop portion of the yoke when the modular extension stop is in the installed position.

[0134] An exemplary rotational hinge subassembly includes a tibial yoke defining a lateral hinge bore that extends through a first side surface and a second side surface of a head, a tibial axial post extending away from the head, and a body member disposed between the head and the tibial axial post, the body member separating the head by an offset distance from the tibial axial post; a tibial yoke; a femoral box having a first arm and a second arm extending rearwardly from a main body portion, the main body portion configured to engage a lateral surface of a femoral box cavity of a femoral box component of a femoral component of a knee prosthesis, the first arm and the second arm each defining a first arm bore and a second arm bore that are axially aligned, the first arm being disposed adjacent to the first side surface and the second arm being disposed adjacent to the second side surface, such that the first arm bore and the second arm bore are axially aligned with the lateral hinge bore; a femoral box; and a lateral hinge pin extending through the lateral hinge bore and into the first arm bore and the second arm bore.

[0135] In an exemplary embodiment of the rotational hinge subassembly, the rotational hinge subassembly is pre-assembled.

[0136] In an exemplary embodiment of the rotational hinge subassembly, the first arm and the second arm are disposed flush with the side surfaces of the head.

[0137] In an exemplary embodiment of the rotational hinge subassembly, the lateral hinge pin does not extend beyond the first and second arms of the femoral box.

[0138] In an exemplary embodiment of the rotational hinge subassembly, the rotational hinge assembly may further include a bearing disposed between the first side surface of the head and the first arm.

[0139] In an exemplary embodiment of the rotational hinge sub-assembly, the femur box is made of a material selected from the group of materials consisting essentially of cobalt-chromium-molybdenum alloy, titanium alloy, zirconia-reinforced alumina ceramic, ceramic material, ultra-high molecular weight polyethylene, polyetheretherketone, combinations thereof, and other biocompatible clinically proven joint movement materials.

[0140] In an exemplary embodiment of the rotational hinge sub-assembly, the femur fastening mechanism is selected from the group consisting essentially of a femur box fixing bore configured to receive a femur fastener, a protrusion, a receiving portion, a plurality of protrusions, a plurality of receiving portions, a magnet, a clamp, a hook, a lip, a binder, an adhesive, and combinations thereof.

[0141] An exemplary rotational hinge subassembly includes a tibial yoke having a body member with a head disposed at a first end, and a tibial axis post extending from a second end of the body member, the second end being disposed distally from the first end. The head defines a lateral hinge bore extending through a first side surface and a second side surface of the head, the lateral hinge bore defining a lateral axis extending laterally therethrough. The tibial axis post defines a midline axis extending longitudinally therethrough. A reference axis extends orthogonally through the lateral axis and is parallel to the midline axis. An offset distance separates the midline axis from the reference axis. The tibial yoke is provided. A femur box includes a first arm extending rearwardly from a main body portion and a second arm extending rearwardly from the main body portion. The second arm faces the first arm, and the main body portion is configured to engage a lateral surface of a femur box cavity of a femoral component of a knee prosthesis, thereby defining a femoral fastening mechanism. The first arm defines a first bore, the second arm defines a second bore, the first bore is axially aligned with the second bore, the first arm is disposed adjacent to the first side surface, and the second arm is disposed adjacent to the second side surface. Thus, the first bore and the second bore are axially aligned with the lateral hinge bore. The femur box is provided. A lateral hinge pin extends through the lateral hinge bore and into the first bore and the second bore, thereby engaging the femur box hingedly to the head of the yoke.

[0142] An exemplary knee prosthesis comprises a tibial component, a femoral component, and a rotational hinge subassembly having a first joint element configured to be coupled to the femoral component and a second joint element configured to be disposed in the tibial component, the rotational hinge subassembly being rotatable about a rotational axis within the tibial component. The rotational hinge subassembly comprises a first joint element and a second joint element hingedly coupled to the first joint element. The first joint element defines an engaged position in which the first joint element is disposed within the femoral component and engages the femoral component in a locking manner, and a disengaged position in which the first joint element is completely separated from the femoral component. The first joint element defines an engagement direction and is movable relative to the femoral component to transfer the first joint element from the disengaged position into the engaged position, the engagement direction running sagittally with respect to the rotational axis.

[0143] In the exemplary knee prosthesis, the locking manner is a projection-receiving locking manner, and the projection and receiving elements of the projection-receiving locking manner are disposed coplanarly with a parasagittal plane extending non-parallel to the engagement direction. In such an exemplary knee prosthesis, the projection-receiving locking manner may comprise a first joint element having a region defining a first receiving bore and a femoral component having a region defining a femoral receiving bore, the first receiving bore and the femoral receiving bore being aligned and a fastener extending through the first receiving bore and the femoral receiving bore.

[0144] In the exemplary knee prosthesis, the parasagittal plane extends through a midpoint of the femoral component.

[0145] In the exemplary knee prosthesis, the locking manner is a bonding or magnetic locking manner.

[0146] Although the present invention has been described from the perspective of specific embodiments, it is expected that modifications and alterations will be apparent to those skilled in the art. Accordingly, the following claims are intended to be construed to embrace all modifications and alterations that fall within the true spirit and scope of the present invention.

Claims

1. An artificial joint tibial yoke (40) for a rotating hinge sub-assembly (10), comprising: a body member (45) having a head (24) disposed at a first end (67); a tibial shaft post (20) extending from a second end (77) of the body member (45); a second end (77) disposed distally from the first end (67); a head (24) defining a transverse hinge bore (25) passing through its first outer side and second outer side; a transverse hinge bore (25) defining a transverse axis (TR) passing therethrough in the transverse direction; a tibial shaft post (20) defining a mid-axis passing therethrough in the longitudinal direction, wherein a reference axis is substantially orthogonal to the transverse axis (TR) and extends substantially parallel to the mid-axis; an offset distance (D) separates the mid-axis from the reference axis; the artificial joint tibial yoke (40) further comprises an extension stopper portion (28) extending between the head (24) and the tibial shaft post (20), and the extension stopper portion (28) comprises a snap-fit pocket (29); the tibial yoke (40) further comprises a modular extension stopper (30) having a lock tab extending from its bottom, and the lock tab is configured to extend into the snap-fit pocket (29) of the extension stopper portion (28) of the yoke (40) when the modular extension stopper (30) is in the installed position. An artificial joint tibial yoke for a rotating hinge sub-assembly (10).

2. The tibial yoke according to claim 1, wherein the tibial shaft post (20), the body member (45), and the head (24) are of a single continuous structure.

3. The tibial yoke according to claim 1 or claim 2, wherein the offset distance (D) is selected from a range of distances consisting of 12 mm to 15 mm.

4. The tibial yoke according to any one of claims 1 to 3, wherein the tibial shaft post further includes a post length (L), and the post length (L) has a value of 40 mm to 70 mm.

5. A rotating hinge sub-assembly (10), comprising: a tibial yoke (40) according to any one of claims 1 to 4; a femoral box (80); and the femoral box (80) includes: a first arm (82) and a second arm (86) extending rearward from a body portion (91); The main body portion (91) having a femoral fixation mechanism configured to engage a transverse surface (92) of a femoral box cavity (280) of a femoral component (205) of a knee joint prosthesis, The first arm (82) and the second arm (86) each define first and second arm bores (85, 88) that are axially aligned, The first arm (82) is disposed adjacent to a first side surface, the second arm (86) is disposed adjacent to a second side surface, and the first arm bore (85) and the second arm bore (88) are axially aligned with a lateral hinge bore (25), A lateral hinge pin (50) that passes through the lateral hinge bore (25) and extends into the first arm bore (85) and the second arm bore (88), A rotary hinge subassembly comprising.

6. The first arm (82) and the second arm (86) are flush with a side surface of the head (24), and the lateral hinge pin (50) does not extend beyond the first and second arms (82, 86) of the femoral box (80). The rotary hinge subassembly according to claim 5.

7. A first bearing (60) disposed between a first side surface of the head (24) and the first arm (82), and a second bearing (60) disposed between a second side surface of the head (24) and the second arm (86). The rotary hinge subassembly according to claim 5 or 6, further comprising.

8. The femoral box (80) is made of a material selected from the group consisting of cobalt-chromium-molybdenum alloys, titanium alloys, zirconia-reinforced alumina ceramics, ceramic materials, ultra-high molecular weight polyethylene, polyetheretherketone, combinations thereof, and other biocompatible and clinically proven joint materials. The rotary hinge subassembly according to any one of claims 5 to 7.

9. The femoral fixation mechanism is selected from the group consisting of a femoral box fixing bore (81) configured to receive a femoral fixture (210), a protrusion, a receiving portion, a plurality of protrusions, a plurality of receiving portions, a magnet, a clamp, a hook, a lip, a binder, an adhesive, and combinations thereof. The rotary hinge subassembly according to any one of claims 5 to 8.

10. Comprising the rotary hinge subassembly (10) according to any one of claims 5 to 9, The femur box (80) is configured to be mechanically engaged with the femur component (205) via a femur fastener (210), The femur fastener (210) is non-axis-aligned with the tibial axis of rotation (A) when the knee is flexed or extended, and the hinge pin (50) extending laterally of the rotary hinge sub-assembly (10) is not mechanically engaged with the femur component (205) in the installed configuration, a rotary hinge knee prosthesis implant assembly.

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