Rotating hinge knee subassemblies

Abstract

To provide rotating hinge implants for revision and primary knees and methods of implantation thereof.SOLUTION: There are provided assemblies 10, systems, kits and methods related to a prosthetic rotating hinge assembly 1. Exemplary embodiments disclosed herein can comprise a preassembled rotating hinge subassembly 10 having a hingedly rotating femur box 80 configured to be mechanically engaged to a femoral component 205 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 1

Description

[Background technology]

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

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

[0003] 3. Related technologies Rotating hinge knee implants are typically used in revision knee surgery in situations where the patient's natural ligaments and other supporting anatomical structures are severely compromised. Non-rotating hinge knee implants were initially used to replace the stabilizing function of the missing posterior cruciate ligament ("PCL"). However, surgeons soon recognized that simple hinge knees were prone to accelerated wear and failure. This problem was addressed by providing a rotating hinge feature so that the tibia rotates about a tibial axis that is generally perpendicular to the femur during flexion. Several designs have been used for this purpose. See, for example, U.S. Pat. No. 6,773,461 and U.S. Pat. No. 10,682,236.

[0004] Some drawbacks of conventional rotating hinge knees include the hinge pins often being inserted laterally, requiring multiple incisions into the leg. Some rotating hinge assemblies, such as those disclosed in U.S. Patent No. 6,773,461, must be assembled during surgery. This design prolongs the duration of the procedure, which in turn increases the risk of infection and other complications due to time under anesthesia. Other designs, such as the rotating hinge assembly disclosed in U.S. Patent No. 10,682,236, require multiple locking mechanisms. These mechanisms also prolong installation and overall procedure time. Complex locking mechanisms are also difficult to reverse if the patient undergoes future revision surgery.

[0005] Furthermore, the devices disclosed in both U.S. Patent No. 6,773,461 and U.S. Patent No. 10,682,236 have retention elements inserted and positioned around the tibial axis of rotation. During operation, lateral load-bearing elements, such as threads, positioned around the tibial axis of rotation generally experience significant compressive forces from the femur. This, combined with the torsional forces that threads may experience during normal knee joint flexion and rotation, can lead to premature failure of these threaded elements (or their associated components). Premature implant failure can result in further revision surgery that could be avoided with other methods to fix or replace the implant. Replacing the entire implant often involves cutting the bone to which the implant is attached. Rotating hinge assemblies are frequently used in patients who already suffer from significant bone deterioration. If insufficient bone remains, further correction of a failed rotating hinge assembly may not be possible. Summary of the Invention

[0006] Therefore, there is a need for an improved rotating hinge knee having the properties, features, and functionality described herein.

[0007] The problems of long and cumbersome surgical installation procedures, as well as the problem of rotating hinge implants prematurely failing due to mechanical wear of the internal tibial alignment implant fasteners, can be alleviated by an exemplary knee joint prosthetic assembly that includes a rotating hinge subassembly having a femoral box that can hingeably articulate about a tibial yoke (e.g., via a lateral hinge pin), the femoral box configured to be mechanically engaged to a femoral component via a femoral fastener that is non-axially aligned with the axis of rotation of the tibia when the knee is in flexion or extension, and the lateral hinge pin of the rotating hinge subassembly is not mechanically engaged to the femoral component in the installed configuration.

[0008] It is contemplated that certain exemplary embodiments disclosed herein may allow for the implantation of a rotating hinge knee through a single incision.

[0009] It is further contemplated that certain exemplary embodiments according to the present disclosure may provide a rotating hinge knee having a pre-assembled rotating hinge subassembly that is not pre-assembled with the femoral component or the tibial component of a prosthetic implant.

[0010] Certain exemplary embodiments according to the present disclosure may provide a rotating hinge knee having one femoral fastener for securing the rotating hinge subassembly to a prosthetic femoral component, the femoral fastener engaging the femoral component in the parasagittal plane.

[0011] It is further contemplated that certain exemplary embodiments according to the present disclosure do not permit the need for excessive dislocation of the distal femur relative to the proximal tibia during installation and assembly of the prosthetic implant, which may minimize resection of surrounding soft tissue, thereby contributing to a faster patient recovery.

[0012] Further exemplary embodiments disclosed herein may provide a rotating hinge knee having an extension stop for interacting with the femoral component.

[0013] The foregoing objects are achieved by providing a rotating hinge knee implant assembly having the features described herein. [Brief explanation of the drawings]

[0014] The foregoing will be apparent from the following more particular description of exemplary embodiments of the disclosure, as illustrated in the accompanying drawings, which are not necessarily to scale, emphasis instead being placed upon illustrating disclosed embodiments.

[0015] [Figure 1] FIG. 1 is a front view of an exemplary embodiment of a prosthetic rotating hinge knee implant assembly in an assembled state (i.e., installed configuration). [Figure 2A] FIG. 1 illustrates a front perspective view of one exemplary embodiment of the femoral and tibial components of a prosthetic rotating hinge knee implant assembly. [Figure 2B] FIG. 1 illustrates a front perspective view of one exemplary embodiment of a rotating hinge subassembly for use in a prosthetic rotating hinge knee implant assembly. [Figure 2C] 1 illustrates a front perspective view of one exemplary embodiment of a rotating hinge knee implant assembly showing insertion of the rotating hinge subassembly into the tibial component. [Figure 2D] FIG. 1 illustrates a front perspective view of one exemplary embodiment of a prosthetic rotating hinge knee implant assembly showing the attachment of the rotating hinge subassembly to the femoral component. [Figure 3A] 1 illustrates a cross-sectional side view of one exemplary embodiment of a prosthetic rotating hinge knee implant assembly in extension, where the cross-section is taken from a parasagittal plane bisecting the exemplary prosthetic rotating hinge implant assembly. FIG. [Figure 3B]1 illustrates a cross-sectional side view of one exemplary embodiment of a prosthetic rotating hinge knee implant assembly in flexion, where the cross-section is taken from a parasagittal plane bisecting the exemplary prosthetic rotating hinge implant assembly. [Figure 4] 1A-1C illustrate an exploded view of one embodiment of an exemplary prosthetic rotating hinge knee implant assembly and an exploded view of an exemplary rotating hinge knee subassembly. [Figure 5] 1 illustrates a perspective view of one embodiment of a femoral box for use in an exemplary rotating hinge subassembly. [Figure 6] 1 illustrates a perspective view of one embodiment of a femoral box bearing member for use with an exemplary prosthetic rotating hinge knee implant assembly. [Figure 7A] 1 illustrates a side view of one embodiment of an exemplary tibial yoke for use in a prosthetic rotating hinge subassembly. [Figure 7B] 7B depicts a front view of the exemplary embodiment of the tibial yoke depicted in FIG. 7A. [Figure 7C] 7C depicts a top view of the exemplary embodiment of the tibial yoke depicted in FIGS. 7A and 7B. [Figure 7D] FIG. 7D is a bottom view of the exemplary embodiment of the tibial yoke depicted in FIGS. 7A, 7B, and 7C. [Figure 8A] FIG. 14 illustrates a top perspective view of one embodiment of a modular extension stop used in a rotating hinge subassembly. [Figure 8B] FIG. 10 shows a side view of one embodiment of a modular extension stop used in a rotating hinge subassembly. [Figure 8C] FIG. 10 illustrates a front view of one embodiment of a modular extension stop used in a rotating hinge subassembly. [Figure 9] FIG. 1 shows a perspective view from the leading end to the trailing end of one embodiment of a femoral fastener for use with a rotating hinge knee implant assembly. [Figure 10A] FIG. 14 shows a top perspective view of another embodiment of an extension stop for use with a rotating hinge knee implant assembly. [Figure 10B] 14A shows a side view of another embodiment of a modular extension stop for use with a rotating hinge knee implant assembly. [Figure 10C] 14A shows a front view of another embodiment of a modular extension stop for use with a rotating hinge knee implant assembly. [Figure 11A] FIG. 1 is a perspective view of an exemplary prosthetic rotating hinge knee implant assembly showing the rotating hinge subassembly prior to being secured to the femoral component via a femoral fastener. [Figure 11B] FIG. 1 is a perspective view of an exemplary prosthetic rotating hinge knee implant assembly showing the rotating hinge subassembly in an engaged position. [Figure 12] FIG. 1C is a cross-sectional side view of an exemplary embodiment of a rotating hinge knee implant assembly in extension showing an alternative modular extension stop, where the cross-section is taken from a parasagittal plane bisecting the exemplary prosthetic rotating hinge implant assembly. [Figure 13] 1 is a schematic perspective view of an anatomical plane for a human. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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 present invention. The present embodiments were chosen and described in order to best explain the principles of the invention and its practical application. Those skilled in the art will recognize that many modifications can be made to the invention disclosed herein without departing from the scope and spirit of the invention.

[0017] Unless otherwise stated, like reference numerals designate corresponding parts throughout the several views. While the drawings depict embodiments of various features and components according to the present disclosure, 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.

[0018] Unless expressly stated otherwise herein, (a) all words used herein should be construed in gender or number (singular or plural) as such context requires; (b) the singular terms "a," "an," and "the" used in this specification and the appended claims include plural references unless the context clearly dictates otherwise; (c) the antecedent term "about" applied to a recited range or value indicates approximation of the deviation from the measured value to a range or value that is known or expected in the art; and (d) the terms "herein," "hereby," and "this" are used interchangeably. The following rules of construction apply herein: (a) the words "hereto," "hereinbefore," "hereinafter," and similarly introductory words refer to the specification as a whole and not to any particular paragraph, claim, or other subdivision, unless otherwise expressly stated; (b) descriptive headings are for convenience only and shall not control or affect the meaning of any portion of this specification; and (c) "or" and "any" are not exclusive, and "include" and "including" are not limiting. Furthermore, the terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to").

[0019] References herein to "one embodiment," "embodiment," "exemplary embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments may necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted 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.

[0020] To the extent necessary to provide explanatory support, the subject matter and / or text of the appended claims are incorporated herein by reference in their entirety.

[0021] The recitation of ranges of values ​​herein is intended merely as a shorthand method of individually referring to each separate value falling within any subrange therebetween, unless expressly indicated otherwise herein. Each separate value within a recited range is incorporated into the specification or claims as if each separate value were individually recited herein. When a specific range of values ​​is provided, it is understood that each intervening value is included herein, to the nearest tenth of the unit of the lower limit between the upper and lower limits of that range, and to any other stated or intervening value within that stated range of that subrange, 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 express and expressly excluded limits in the stated range.

[0022] It should be noted that some of the terms used herein are relative terms. For example, the terms "upper" and "lower" are relative to one another in position, i.e., the upper component is at a higher elevation than the lower component in each orientation, although these terms may change if the orientation is reversed. The terms "inlet" and "outlet" are relative to the fluid flowing through them with respect to a given structure, e.g., fluid flows 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 fluid flows through various components before flowing through the downstream component.

[0023] The terms "horizontal" and "vertical" are used to indicate orientation relative to an absolute reference, i.e., ground level. However, these terms should not be interpreted as requiring structures to be absolutely parallel or absolutely perpendicular to one another. For example, a first vertical structure and a second vertical structure are not necessarily parallel to one another. The terms "top" and "bottom" or "base" are used to refer to an absolute reference, i.e., a position or surface where the top is always higher than the bottom or base, relative to the Earth's surface. The terms "upward" and "downward" are also relative to an absolute reference; upward flow is always against the Earth's gravity.

[0024] Throughout this disclosure, various location terms, such as "distal," "proximal," "medial," "lateral," "anterior," and "posterior," are used in a conventional manner when referring to human anatomy. More specifically, "distal" refers to the area away from the point of attachment to the body, and "proximal" refers to the area 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 that is disposed closer to the center of the body. "Lateral" means something is disposed closer to the right or left side of the body than the center of the body. With respect to "anterior" and "posterior," "anterior" refers to something that is disposed closer to the front of the body, and "posterior" refers to something that is disposed closer to the back of the "body."

[0025] "Varus" and "valgus" are broad terms that include, but are not limited to, medial and / or lateral rotational movements relative to the knee joint.

[0026] 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.

[0027] 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.

[0028] The term "anatomical axis" refers to an imaginary line drawn longitudinally down the middle of the femoral shaft or tibial shaft, depending on use.

[0029] The hinge knee assemblies, systems, and methods herein can be configured to be implanted in the same manner as currently available primary and revision surgical techniques.

[0030] During primary or revision surgery, the surgeon generally makes a vertical midline incision on the anterior side of the operative knee. The incision is generally made with the knee flexed at or below the tibial tubercle and may extend several inches above the patella.

[0031] In primary TKA, the surgeon continues to dissect the fatty tissue to expose the anterior surface of the joint capsule. The surgeon then performs a medial parapatellar arthrotomy, penetrating the joint capsule and resecting the medial patellar retina. A retractor is then typically used to displace the patella generally laterally, exposing the distal femoral condyle and the cartilaginous meniscus resting on the proximal tibial plateau. The surgeon then removes the meniscus and uses instruments to measure and resect the distal femur and proximal tibia to accommodate the investigational implant. The investigational implant is generally a trial prosthesis with the same functional dimensions as the actual prosthesis, but it is designed to be temporarily installed and removed for the purposes of evaluating the fit of the actual prosthesis and assessing knee joint kinematics. Once the surgeon is satisfied with the size of the investigational implant and the kinematic characteristics of the knee joint, the investigational implant is removed and the actual implant is installed.

[0032] In a revision procedure, after the surgeon makes an initial incision, the surgeon may release the scar tissue around the patellar tendon. The surgeon then generally laterally displaces the patella or patellar implant (i.e., pre-subluxes) to expose the pre-installed implant, which typically includes a femoral component installed on the distal femur, a tibial component installed on the proximal tibia, and a meniscal insert disposed between the femoral and tibial components. The surgeon then removes the pre-installed implant.

[0033] It should be understood that the type of pre-installed implant may vary from case to case. Pre-installed implants may include static spacers inserted into aligned intramedullary tunnels in the distal femur and proximal tibia to stabilize the knee joint, or complex implants used to reconstruct portions of a traumatized knee joint. However, typical previously installed implants include implants installed during a primary TKA or previously revised implants. While various factors influence the decision to replace a previously installed implant with a rotating hinge knee implant, common factors may include excessive wear or inactivity, the presence of trauma, progression of bone degenerative disease, underlying bone integrity, and severe varus / valgus deformity. Common bone degenerative diseases include rheumatoid arthritis and osteoarthritis.

[0034] Previously placed implants may be bonded to bone in a variety of ways. Press-fit implants typically have porous, rough surfaces on the mating sides of the femoral and tibial components. The porous surfaces allow bone to regrow into these holes over time. Another very common bonding technique involves the use of antibiotic-infused grout, commonly known by those in the orthopedic industry as "bone cement." It will be understood that "bone cement" is a term used in the art, even though bone cement itself generally does not possess adhesive properties. Bone cements generally rely on a tight mechanical interlock between the irregular surface of the bone and the mating surface of the prosthesis. Common bone cements include polymethyl methacrylate ("PMMA"), calcium phosphate cement ("CPC"), and glass polyalkenoate isomer cement ("GPIC").

[0035] Removal of a previously placed implant generally involves cutting the bone underlying the bone cement, or in the case of a press-fit implant, the bone underlying the press-fit implant. This resection exposes fresh bone that can receive a revision press-fit or bone-cemented implant. Removing bone to remove a previously placed implant can result in joint line shifting if the revision implant is not sized to replace the newly resected bone.

[0036] This tibial resection is typically coplanar, with a transverse body plane perpendicular to the anatomical axis of the tibia. Once resected, the resected area of ​​the tibia may be known as the "tibial plateau." After the previously installed implant is removed, a series of differently sized intramedullary reamers may be used to prepare or extend the intramedullary holes in both the tibia and femur to accommodate the tibial and femoral components of the revision implant, respectively. After reaming, the surgeon may use instruments to further measure and resect the proximal tibial plateau. The surgeon may then place the investigational tibial component onto the resected proximal tibial plateau. Surgeons typically use different instruments to measure and resect the distal femoral condyles for the purpose of placing the investigational femoral component. If the investigational component is not properly seated, the surgeon may use additional instruments to measure and resect the femoral condyles and / or tibial plateau until the desired seating is achieved.

[0037] Rotating hinge knees typically have a femoral box cavity (see Figure 2A, 280) in the femoral component of the prosthetic implant (see Figure 2A, 205). To accommodate the femoral box cavity, additional resection of the lateral side of the medial condyle and the medial side 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.

[0038] Next, the surgeon typically inserts a trial meniscal insert between the trial tibial tray and the trial femoral component to test the trial implant for knee flexion and extension, total body stability, and patellar tracking. Metal blocks called "augments" can be attached to the tibial or femoral components to replace missing or damaged bone. Once satisfied with the trial and motion characteristics, the surgeon can permanently fixate the actual tibial and femoral components of the prosthetic implant using a new, uncured, antibiotic-infused bone cement, or, if desired, use a press-fit implant, avoiding the use of bone cement.

[0039] Other rotating hinge knee systems differ from the present disclosure in that many other rotating hinge knee systems require intraoperative lateral assembly of the hinge components. This intraoperative assembly requires additional resection of the lateral surface of one or more femoral condyles to provide access to the hinge components (usually pins). 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 be appreciated that additional, but unnecessary, lateral and / or posterior condylar resections prolong the patient's recovery time, introduce new areas of potential infection, and introduce areas of structural weakness, especially in the presence of existing bone deterioration. Any area of ​​structural weakness increases the risk of catastrophic implant failure during normal use.

[0040] Also, intraoperative assembly of the rotating hinge knee prolongs the procedure and increases the risk of infection and other complications resulting from increased time under anesthesia.

[0041] Some other rotating hinge knees use threaded retention elements configured to be inserted and disposed about the tibial axis of rotation. Without being bound by theory, it is postulated that in operation, lateral load-bearing elements disposed about the tibial axis of rotation generally experience significant compressive forces from the femur. This, combined with the torsional forces that the threads may be subjected to during normal flexion and rotation of the knee joint, can cause premature failure of components with these threaded elements, thereby requiring further revision surgery to replace either worn components or the entire implant.

[0042] Additionally, other rotating hinge knees are not configured to restrict five of the six degrees of freedom of the femoral and tibial components during installation. It is contemplated that the exemplary embodiments disclosed herein can further facilitate the alignment process by allowing the 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).

[0043] To reduce installation time compared to existing rotating hinge knees, the exemplary embodiment of the rotating hinge subassembly 10 described herein (see, e.g., FIG. 2C ) can be pre-assembled into a self-contained module that is configured to be mechanically secured to the femoral component using a single femoral fastener 210.

[0044] As shown in the assembled anterior view of Figure 1, a rotating hinge knee prosthetic implant assembly 1 according to the present disclosure generally includes a femoral component 205, a tibial component 105, a meniscal insert 150 disposed between the femoral component 205 and the tibial component 105, and a rotating hinge subassembly 10. While many of the rotating hinge subassembly components are obscured by the femoral component 205 and the tibial component 105 in Figure 1, several components are visible, such as the femoral box 80 disposed in the femoral box cavity 280 (Figure 2A) of the femoral component 205 and the head 24 of the tibial yoke 40. A bearing 60 is disposed between the head 24 and the femoral box 80 to facilitate hinge motion of the rotating hinge knee prosthetic implant assembly 1. The femoral fastener 210 extends through the femoral box fixation bore 81 in the femoral box 80 and the femoral fixation bore 87 in the femoral component 205 ( FIG. 2A ) to fixedly engage the rotating hinge subassembly 10 to the femoral component 205. In the depicted embodiment, the femoral fastener 210 is a tapered screw, and the femoral box fixation bore 81 and the femoral fixation bore 87 are threaded to engage corresponding threads of the tapered screw. In other exemplary embodiments, either the femoral fixation bore 87, the femoral box fixation bore 81, or both the femoral fixation bore 87 and the femoral box fixation bore 81 need not be threaded. An extension stop 30 may be provided to prevent overextension of the rotating hinge knee prosthetic implant assembly 1. In one particular exemplary embodiment, the extension stop 30 may be a modular extension stop 30. That is, the surgeon can select and place one of a variety of available extension stops based on the patient's particular anatomy.

[0045] The femoral component 205 includes a medial implant condyle 218 disposed distally from a lateral implant condyle 219. FIG. 1 depicts each implant condyle 218, 219 resting on the articular surface 151 (FIG. 2A) of a meniscal insert 150. The meniscal insert 150 is typically made from medical-grade polyethylene (e.g., ultra-high molecular weight polyethylene (UHMWPE)) or other suitable clinically proven biocompatible material. A base portion 101 of the tibial component 105 supports the meniscal insert 150. The base portion 101 is configured to rest on the patient's resected tibial plateau (103, FIG. 2C). The tibial component 105 may be made from a biocompatible material such as a cobalt-chromium-molybdenum alloy, a titanium alloy, or other clinically proven, high-strength biocompatible material. A tibial stem 102 depends inferiorly from the distal side 106 of the tibial base portion 101. The tibial stem 102 is configured to be inserted into an intramedullary bore (see depicted notch 109) of the tibia 100. The keel 127 facilitates installation and fixation of the tibial component 105 into the intramedullary bore (see 109) in the tibia 100 (see FIG. 2C ). The depicted notch 109 is provided to illustrate how the tibial component 105 may be seated in and on the proximal tibia 100 when installed. In practice, the depicted notch 109 should generally not be present. It will be understood 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 may be modularly configured with different length extensions to accommodate intramedullary bores of different lengths, angles, or offsets relative to the transverse plane 198 ( FIG. 2D ). In a further exemplary embodiment, the keel 127 may be a modular component configured to fixedly engage with the tibial component 105 .As better seen in FIG. 4 , the tibial stem 102 is substantially hollow at least on its upper / proximal end and has an axial bore 104 configured to receive the longitudinal tibial axial post 20 of the rotating hinge subassembly 10, as further described below.

[0046] Desirably, the sleeve 120 is inserted into the axial bore 104 prior to insertion of the tibial axial post 20. The sleeve 120 prevents the tibial axial post 20, which is typically made from a biocompatible metal alloy, from rubbing against the inside of the tibial stem 102, which is also typically made from a biocompatible metal alloy. Without the sleeve 120, repeated friction of the tibial axial post 20 could cause it to move toward the inside of the tibial stem 102, generating metal debris that could compromise the effectiveness and integrity of the prosthesis. It is contemplated that the sleeve 120 may be made from UHMWPE, polyetheretherketone (“PEEK”), or other clinically proven biocompatible polymers. In other exemplary embodiments, the sleeve 120 may be made from a ceramic material, including, but not limited to, zirconia-toughened alumina (“ZTA”) ceramic. In yet another exemplary embodiment, the sleeve 120 may be fabricated from a cobalt-chromium-molybdenum alloy or a titanium alloy and may be coated with zirconium oxide or niobium nitride to further reduce the coefficient of friction between the articulating components and increase durability. In this manner, the sleeve 120 effectively creates a barrier between the inner wall of the tibial stem 102 and the outer wall of the tibial axial post 20.

[0047] 2A-2D provide a series of perspective views illustrating the major steps of implantation of the rotating hinge knee prosthetic implant assembly 1.

[0048] FIG. 2A depicts the femoral component 205 oriented in flexion relative to the tibial component 105. A femoral box cavity 280 is disposed between the medial implant condyle 218 and the adjacent lateral implant condyle 219. 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 exposed to the femoral box cavity 280. The femoral fixation bore 87 is secured to a lateral surface 92 extending between the inner surfaces of the medial implant condyle 218 and the lateral implant condyle 219. The meniscal insert 150 is disposed on the base 101 of the tibial component 105 in a rotating or movable bearing configuration (see FIG. 3A for a discussion of an exemplary rotating bearing arrangement). Various configurations may be used for the connection between the meniscal insert 150 and the tibial base portion 101.

[0049] 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 medial implant condyle 218 and the lateral implant condyle 219) can be optimally coated with a durable biocompatible material with a low coefficient of friction to provide a smooth articular bearing surface. Examples of such coatings include zirconium oxide or niobium nitride.

[0050] FIG. 2B provides a perspective view of the rotating hinge subassembly 10 in a disengaged position, with the first articulating element (e.g., femoral box 80) completely separated from the femoral component 205. One advantage of the exemplary embodiment of the present disclosure is that the rotating hinge subassembly 10 can be fully assembled before being inserted into a patient's knee, thus facilitating the implantation procedure and contributing to reduced surgical time. The pre-assembled rotating hinge subassembly 10 includes a yoke 40 and a femoral box 80 that hingeably articulates about the head 24 of the yoke 40. The depicted femoral box 80 includes a femoral box fixation bore 81. It will be appreciated that the femoral box fixation bore 81 is an example of a femoral fastening mechanism that can be used to selectively engage the femoral box 80 with the femoral box cavity 280 of the femoral component. It will be understood that in other exemplary embodiments, the femoral fastening mechanism may include a protrusion, a recess, a receiver, multiple protrusions, multiple recesses, multiple receivers, part of a protrusion-receptor locking mechanism, a magnet, a clamp, a hook, a lip, a welding agent, a bonding agent, an adhesive, or a combination thereof. In other exemplary embodiments, the femoral fastening mechanism may include a pin inserted through the femoral box fixation bore 81 and the femoral fixation bore 87. In such exemplary embodiments, the surgeon may use a small hammer to deform the distal end of the inserted pin in the femoral fixation section, thereby securely engaging the femoral fastening mechanism with the femoral component in the parasagittal plane z (see also FIGS. 11A and 13 ). In such embodiments, the femoral fixation bore 87 may have a maximum diameter greater than the maximum diameter of the femoral box fixation bore 81. The increased volume of femoral fixation bore 87 relative to femoral box fixation bore 81 may allow the distal end of the pin to deform within femoral fixation bore 87, thereby locking the pin femoral fastener in a lug-receptacle locking manner. Without being bound by theory, it is contemplated that the elimination of threaded elements within femoral fastener 210 may further mitigate the likelihood of premature failure resulting from any small incidence of torsional force transfer to femoral fastener 210.

[0051] In yet another exemplary embodiment, the femoral fastening mechanism may include magnetic elements of opposite polarity, where a first magnetic element is disposed within the femoral box 80 and a second magnetic element of opposite polarity to the first magnetic element is disposed within the lateral surface 92 extending between the inner surfaces of the medial implant condyle 218 and the lateral implant condyle 219 of the femoral component 205.

[0052] The exemplary rotating hinge subassembly 10 may further include a modular extension stop 30 that may be configured to snap-fit ​​into the extension stop portion 28 (FIG. 3A) of the yoke 40. One or more bearing members 60 are pivotally connected to the head 24 (for example) of the yoke 40 via a lateral hinge pin 50 (FIG. 4). An end 53 of the lateral hinge pin 50 is visible in FIG. 2B. A lower or inferior portion of the body 45 of the yoke 40 includes a tibial axial post 20 configured to be disposed within the 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 still other exemplary embodiments, three or more bearing members 60 may be used.

[0053] FIG. 2C depicts the femoral component 205 secured to the distal femur 200 and the tibial component 105 secured to the proximal tibia 100 of the patient's knee joint using the resection and implantation techniques described above. FIG. 2C shows the rotating hinge subassembly 10 immediately prior to insertion and attachment to the implant assembly (i.e., the femoral component 205, meniscal insert 150, and tibial component 105). As shown, the tibial axial post 20 is inserted into the axial bore (104, FIGS. 3A, 4) in the tibial stem 102. The femoral box cavity 280 is sized and configured to allow the tibial axial post 20 to be inserted in a generally anterior or superior-inferior orientation when the femur 200 is in flexion.

[0054] FIG. 2D shows the rotating hinge subassembly 10 attached to the hinge femoral component by a femoral fastener 210. As can be seen in FIG. 2D, with the knee flexed, the tibial axial post 20 (see also FIG. 4) of the yoke 40 is inserted into the axial bore 104 of the tibial stem 102 in rotational relationship R, and the femoral box 80 is seated within the femoral box cavity 280. The femoral fastener 210 is inserted via the fixation bore 81 in the femoral box 80 through the femoral fixation bore 87 in the femoral component 205 (i.e., the second articular element), in this manner securing the femoral box 80 (i.e., the first articular element) to the femoral component 205. When the femoral fastener 210 secures the femoral box 80 to the femoral component 205, the first articular element is in an engaged position. That is, the first articulating element (eg, femoral box 80) is disposed within the femoral component 205 and engages the femoral component 205 in a projection-receptor locking manner.

[0055] In this manner, the rotating hinge subassembly 10 is secured to the femoral component 205 and is said to be "fixedly engaged" to the femoral component 205. Other methods of selectively mechanically engaging the first articulation element of the rotating hinge subassembly 10 to the femoral component 205, such as by projection-receptor locking, magnetic locking, clamp locking, bond locking, adhesive locking, or combinations thereof, also may be said to "fixedly engage" the rotating hinge subassembly 10 to the femoral component 205.

[0056] The length of the tibial axial post 20 (see FIG. 3A ), the surrounding unresected soft tissue of the knee (e.g., the medial collateral ligament "MCL" and lateral collateral ligament "LCL"), and the position of the femoral component 205 relative to the tibial component 105 effectively fixate the tibial axial post 20 within the tibial component 105 while allowing the tibial axial post 20 to rotate about the tibial axis of rotation A during use. In this manner, the rotating hinge subassembly 10 is said to be disposed in a hinged and rotating configuration within the rotating hinge knee prosthetic implant assembly 1. That is, the rotating hinge knee prosthetic implant assembly 1 is now able to pivot about the hinge component (i.e., "hinge articulation," see also hinge direction H of rotation about the lateral hinge pin 50 in FIG. 3B ), thereby allowing the rotating hinge knee prosthetic implant assembly 1 to flex and extend as is readily apparent in normal use, and the femur 200 is also now able to rotate slightly axially about the generally vertical tibial axis of rotation A as the rotating hinge knee prosthetic implant assembly 1 undergoes flexion and extension. The length L of the tibial axial post 20 and surrounding soft tissue ( FIG. 7A ) prevents the yoke 40 from dislocating from the axial bore 104 of the tibial stem 102 when the knee is in full flexion. However, the distance between this distal end 26 of the tibial axial post 20 and the bottom of the tibial axial stem 102 may increase when the knee is in full flexion.

[0057] This axial rotation R of the femur 200 relative to the tibia 100 approximates the natural motion of the knee joint. Thus, the rotating hinge knee prosthetic implant assembly 1 avoids some of the wear forces that a fixed hinge knee would be expected to experience during normal use. Because the rotating hinge knee prosthetic implant assembly 1 better approximates the natural motion of a normal knee compared to fixed hinge designs, the rotating hinge knee may provide improved post-operative comfort for the patient.

[0058] In other exemplary embodiments, the tibial axial post 20 may be fixedly engaged to the medial side of the tibial stem 102 or to the sleeve 120 ( FIG. 4 ) to prevent dislocation of the tibial axial post 20 from the axial bore 104 of the tibial stem 102. In such embodiments, the tibial axial post 20 may include 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 sleeve 120 (whichever is present). In yet other exemplary embodiments, the tibial axial post 20, the medial side of the tibial stem 102, or the medial and lateral sides of the sleeve 120 may have protrusions that abut adjacent elements when the tibial axial post 20 is seated inside the tibial stem 102 and fixedly engages the post members therein. In yet other exemplary embodiments, the tibial axial post 20 and adjacent structures (e.g., the sleeve 120 or the medial side of the tibial stem 102) may include magnets of opposite polarity.

[0059] Without being bound by theory, it is envisioned that such an embodiment may be desirable in patients suffering from ligamentous laxity. Typically, the length L ( FIG. 7A ) of the installed tibial axial post 20, combined with relatively nominal tension from the surrounding soft tissue (including the MCL and LCL), prevents 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 ligamentous laxity, the MCL and LCL (and other surrounding soft tissue) may not exhibit sufficient tension to prevent dislocation of the depicted tibial axial post 20 from the depicted sleeve 120 or from the medial side of the tibial stem 102. Thus, securely engaging the tibial axial post 20 to the medial side of the tibial stem 102, or engaging the sleeve 120 in the manner described, may be desirable to prevent dislocation.

[0060] 2D, the depicted femoral fastener 210 is a tapered screw. The depicted tapered screw is generally shorter than the fasteners used in other rotating hinge knees. Furthermore, the threaded tapered screw disclosed in the exemplary embodiment is secured to the femoral component 205, while some other rotating hinge assemblies are secured to the tibial component with a thread.

[0061] Without being bound by theory, it is postulated that the significant compressive and torsional loads experienced by the tibia 100 and tibial component 105 during normal use of the knee may contribute to loosening of such tibial fastener elements, ultimately compromising the future stability and effectiveness of the prosthesis. In designs where the tibial fastener screws are locked, the normal compressive and torsional forces may eventually wear the threads, thereby loosening the rotating hinge component as well and compromising the effectiveness of the implant.

[0062] In embodiments according to the present disclosure, the condyles 218, 219 desirably transfer a majority of the femoral loads (including the body compressive loads described above, as well as the femoral and torsional loads) to the condylar pads 228, 229 of the meniscal insert 150. This is typically known as "condylar loading." The meniscal insert 150 then transfers the femoral loads through the tibial component 105, the tibia 100, and ultimately the patient's foot during normal use. In this manner, the disclosed embodiments desirably avoid transferring excessive forces from the femur to the rotating hinge subassembly 10.

[0063] However, it is contemplated that in practice, not all femoral loads will be transferred to the condylar pads 228, 229 of the meniscal insert 150. A portion of the compressive and torsional loads, as well as other loads such as varus, valgus, hyperextension, flexion, and anterior-posterior pull-out forces, may be transferred from the femur 200 through the rotating hinge subassembly 10. In such cases, it is contemplated that femoral loads are transferred from the femur 200 and femoral component 205 to the femoral box 80 (i.e., the first articular element), through the lateral hinge pin 50 (FIG. 3A), and to the head 24 and body 45 (FIG. 7A) of the yoke 40. 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, it is envisioned that even in situations where forces are transferred to the rotational hinge subassembly 10, the lateral hinge pin 50 and yoke 40 transfer these forces through the rest of the leg while avoiding transferring these forces to the femoral fastener 210. That is, femoral loads are transferred through the femoral box 80 and possibly the lateral hinge pin 50, as described further below, rather than through the femoral fastener 210. By placing the femoral fastener 210 in a position that allows it to mechanically engage the first articular element (e.g., the femoral box 80) on the femoral component 205 while removing the femoral fastener 210 from the force transfer chain, it is contemplated that embodiments according to the present disclosure may avoid fastener cross-threading or other signs of premature wear that would result from normal use. In certain exemplary embodiments, the location of the femoral fastener 210 or other femoral fastening mechanism that mechanically engages the femoral box 80 to the femoral component 205 may desirably be in a position that is coaxial with the tibial axis of rotation A when the knee is in extension (see FIG. 3A ). Without being bound by theory, it is envisioned that having the femoral component 205 coaxial with the tibial axis of rotation A may further minimize torsion and other secondary loads on the femoral fastener 210 or other femoral fastening mechanism.

[0064] FIG. 3A provides a transverse cross-sectional extension view that allows further aspects of the interconnections between components to be visualized. The cross-section is taken along a parasagittal plane separating the implants (see 400 in FIG. 13). The knee is shown in full extension (i.e., zero degrees of flexion). In the depicted embodiment, the tibial axis of rotation A is substantially aligned (i.e., collinear) with the central axis F of the femoral fastener when the rotating hinge knee prosthetic implant assembly 1 is in extension, but is misaligned when the rotating hinge knee prosthetic implant assembly 1 is in flexion (see the central axis F of the femoral fastener relative to the tibial axis of rotation A in FIG. 3B). The vector of the central axis F of the femoral fastener moving toward the femoral component 205 can represent an engagement direction. The vector of the central axis F of the femoral fastener moving away from the femoral component 205 can represent a disengagement direction.

[0065] A modular extension stop 30 is provided. As 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. The extension stop is generally used to prevent recurrence. It is envisioned that by modularizing the extension stop 30, the surgeon can select the modular extension stop 30 that best suits the patient's needs. Additionally, in some embodiments, the modular extension stop 30 can be omitted, and instead an extension stop fixed to the rotating hinge subassembly 10 in a fixed configuration can be provided. In such cases, the degree of potential hyperextension is limited by the patient's anatomy and the interaction between the condyles 218, 219 of the femoral component 205 and the raised anterior surface of the meniscal insert 150.

[0066] As shown in FIG. 3A , the femoral box 80 is secured to the femoral component 205 by femoral fasteners 210 extending through the femoral box fixation bores 81. Furthermore, the femoral box 80 and bearing member 60 are hinged to the head 24 of the yoke 40 by the transverse hinge pin 50. In this manner, the femur 200 rotates relative to the head 24 of the yoke 40 about a single transverse axis TR (see H in FIG. 3B ). With the tibial axial post 20 seated in the axial bore 104 of the tibial stem 102, the femur 200 is also free to rotate relative to the tibial component 105 about a generally midline tibial axis of rotation A. The degree of rotation is limited by the patient's anatomy and the interaction between the meniscal insert 150 and the tibial component 102, as further described below. In the embodiment of Figure 3A, the tibial axial post 20 passes through a through bore 108 (Figure 4) formed in the meniscal insert 150 and into the axial bore 104 of the tibial stem 102. In this manner, the rotating hinge subassembly 10 in the engaged position secures the meniscal insert 150 to the rotating hinge knee prosthetic implant assembly 1. In the embodiment of Figure 3A, the modular extension stop 30 is configured to snap fit into the extension stop portion 28 within the body 45 of the yoke 40 in a fixed arrangement.

[0067] 3A further depicts the base portion 101 of the tibial component 105, which further includes an anterior hook 128 and a medial hook 129. Each hook 128, 129 defines a negative space between the bottom of the hook 128, 129 and the surface of the tibial base portion 101. The meniscal insert 150 has an anterior protrusion 131 and a medial protrusion 133 disposed on the base 111 of the meniscal insert. The anterior protrusion 131 and the medial protrusion 133 desirably fill the negative space defined by the bottom of the anterior hook 128 and the medial hook 129 when the meniscal insert 150 is installed on the tibial base portion 101. In this manner, not only is the meniscus insert 150 configured to snap fit onto the tibial base portion, but the arrangement of the hooks 128, 129 and protrusions 131, 133 also allows and limits rotational sliding of the meniscus insert 150 about the approximately midline tibial axis of rotation A during normal flexion and extension of the rotating hinge knee prosthetic implant assembly 1.

[0068] It will be appreciated that if the surgeon chooses not to dislocate the entire length of the tibial axial post 20 from the tibial stem 102, the presence of the hinge subassembly 10 in the engaged position will prevent the meniscal insert 150 from sliding out of the tibial component 105 as the knee flexes and lifts during movement. Other methods of securing the meniscal insert 150 to the tibial base 101 so that the meniscal insert 150 is rotatable about the approximately midline tibial axis of rotation A are considered within the scope of this disclosure. Optionally, but desirably, a sleeve 120 may be disposed on the tibial stem 102 between the tibial axial post 20 and the tibial stem 102. The sleeve 120 may be tightly fitted to the inner diameter of the tibial stem 102 and the outer diameter of the tibial axial post 20.

[0069] FIG. 3B provides a lateral cross-sectional deep flexion view that allows further aspects of the interconnections between the components to be visualized. The rotating hinge subassembly 10 can be configured to provide deep flexion ranging from approximately 100 degrees to approximately 138 degrees, which is ideal for revision knees. In certain exemplary embodiments, the range may be approximately 100 degrees to approximately 125 degrees. In deep flexion, 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 meniscal insert 150 and the prongs 131, 133 of the tibial component 102. In addition to pivotal motion, the femur 200 continues to hinge around the tibial axial post 20 only along the axis of the lateral hinge pin 50.

[0070] 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 to a significant extent during flexion. Similarly, if the condyles 218, 219 have two or more radii, the tibial axial post 20 translates upward within the axial bore 104 during flexion.

[0071] Aspects and features of the individual components of the rotating hinge knee prosthetic implant assembly 1 will now be discussed.

[0072] FIG. 4 provides an exploded view of one exemplary embodiment of a rotating hinge knee prosthetic implant assembly 1. Most of these components have been discussed above. However, additional components are visible in the exploded view that were not apparent or visible in previous images. Please refer to other drawings for a detailed overview of the components.

[0073] femoral box FIG. 5 illustrates a perspective view of one embodiment of a femoral box 80 (i.e., an exemplary first joint element) for use in the rotating hinge knee prosthetic implant assembly 1 of the present disclosure. In the embodiment of FIG. 5, the femoral box 80 has a generally clevis configuration. The femoral box 80 includes a main body portion 91 on the anterior end 61 and a pair of opposing arms 82, 86 extending rearward therefrom toward the posterior end 52. In the depicted embodiment, the arms 82, 86 take 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 femoral box 80 defines a femoral box fixation bore 81 extending therethrough. Additionally, the opposing arms 82, 86 each define an arm bore 85, 88 (i.e., the first arm 82 defines the first arm bore 85, and the second arm 86 defines the second arm bore 88) extending therethrough for receiving the lateral hinge pin 50 (FIG. 4). The arm bores 85, 88 are formed in each arm 82, 86. The pair of arm bores 85, 88 are substantially axially aligned with one another (along the lateral axis TR), thereby providing a continuous hinge pin bore spanning the opening between the arms 82, 86.

[0074] In certain exemplary embodiments, the femoral box 80 can be made from a durable, clinically proven, biocompatible material capable of supporting repeated force transfer from the femoral fastening mechanism over the life of the prosthetic implant 1. Exemplary materials include cobalt-chromium-molybdenum alloy and titanium alloy. In other exemplary embodiments, the femoral box 80 can be made from polyetheretherketone (PEEK), an organic thermoplastic polymer. PEEK is hydrophobic, reducing the risk of the thermoplastic fusing with bone. These properties may contribute to reduced wear of the PEEK components over time. PEEK is also radiolucent and non-magnetic, making the PEEK components transparent on radiographs and compatible with magnetic imaging techniques.

[0075] In other exemplary embodiments, it is contemplated that the femoral box 80 may 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 fabricated from metal, it is further contemplated that the femoral box 80 may be optionally 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 coating the outer surfaces of the femoral box 80, including the outer surfaces of the arms 82, 86, may be desirably coated to further reduce the coefficient of friction. For clarity, the femoral wall defining the box fixation bore 81 should not be coated with a friction-reducing substance, as such a substance would facilitate removal of the femoral fastener 210 during normal use.

[0076] As shown in the drawings, the femoral 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 fit flush with the outer surfaces of the arms 82, 86. In one exemplary embodiment, the edges 63 of the femoral box 80 are rounded for non-occluding assembly to the femoral implant.

[0077] Without being bound by theory, it is envisioned that sizing the lateral hinge pin 50 to have its end 53 disposed flush or nearly flush with the outer surfaces 89 of the arms 82, 86 enables the femoral component 205 to transfer any torsional forces from the femur 200 to the femoral box 80 over the combined surface areas of the outer surfaces 89 of the arms 82, 86 and the respective ends 53 of the lateral hinge pin 50. It will be understood that "flush" or "flushly" as used in this context means that the end 53 of the lateral hinge pin 50 is disposed substantially coplanar with a plane coextensive with the outer surfaces 89 of one or both of the arms 82, 86.

[0078] It is contemplated that transferring any torsional forces in this manner may distribute the torsional load over a larger area, thereby reducing the concentration of the torsional load in any one area. It is further contemplated that distributing any torsional load over a wider area may 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 disposed flush with the outer surfaces 89 of the arms 82, 86. Rather, one or both ends 53 of the lateral hinge pin 50 may extend into the pair of arm bores 85, 88, allowing the femoral 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 surfaces 89 of the arms 82, 86. It is envisioned that such embodiments may still provide the advantage of distributing torsional forces over a larger surface area than previously known.

[0079] While the lateral hinge pin 50 is depicted as a separate element throughout the figures (see, for example, FIG. 4 ), it will be understood that in other exemplary embodiments, the medial side 90 of the arms 82, 86 may comprise a portion of the lateral hinge pin 50. In such exemplary embodiments, the medial end of the portion of the lateral hinge pin 50 extends away from the inner surface 90 of the first arm 82 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 hingeably engaging the first arm 82 of the femoral box 80 to the yoke 40. Similarly, such exemplary embodiments may further comprise a second portion of the lateral hinge pin 50 extending away from the inner surface 90 of the second arm 86 (not visible in FIG. 5 , but 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 hingeably engaging the second arm 86 of the femoral box 80 to the yoke 40. In such an exemplary embodiment comprising this modified femoral box 80, the femoral box 80 is said to be a "press fit" or "interference fit" within the lateral hinge bore 25 of the yoke 40. Furthermore, in such an exemplary embodiment, the arm bores 85, 88 may not be present.

[0080] Bearing materials FIG. 6 depicts an exemplary bearing member 60 sized to have a bearing surface extending into the lateral hinge bore 25 of the head 24 of the tibial yoke 40. When disposed in an installed position, the bearing member 60 can freely rotate within the femoral box 80 and around the yoke head 24 and lateral hinge pin 50 (see FIG. 2). It can be appreciated that certain exemplary embodiments can include two or more bearing members 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 manner, 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 manner, the femoral box 80 is configured to hinge rotate about the lateral axis TR of the rotating hinge subassembly 10. Other embodiments achieve hinge 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.

[0081] It is understood that in other exemplary embodiments, the inner side of the bearing member 60 may include 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 of the bearing member 60. In the assembled configuration, the portion of the lateral hinge pin 50 extends into at least one arm bore 85 and into the lateral hinge bore 25 of the head 24 of the yoke 40, thereby hingeably engaging the bearing member 60 to the femoral box 80 and the yoke 40. Multiple bearing members 60, each having a portion of the lateral hinge pin 50 extending from the inner surface, are also contemplated. In such exemplary embodiments with this modified bearing member 60, the portion of the lateral hinge pin 50 is referred to as a "press fit" or "interference fit" into the bearing member 60.

[0082] In embodiments in which 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 a medial hinge portion disposed opposite from the lateral hinge portion, the medial and lateral hinge portions being coaxially aligned with the lateral rotation axis TR in the assembled configuration. The lateral hinge portion is disposed within the arm bore 88 of the arm 86 of the femoral box 80, and the medial hinge portion is disposed within the lateral hinge bore 25 of the yoke 40, thereby hingeably engaging the femoral box 80 to the yoke 40. Such embodiments may further include a second bearing member 60 described to hingeably engage the other arm 82 of the femoral box 80 to the yoke 40. In all such exemplary embodiments, the end 53 of the lateral hinge pin 50 desirably does not extend into the femoral component 205 in the installed configuration.

[0083] In certain exemplary embodiments, it is contemplated that the bearing member 60 may be made from biocompatible, clinically proven articulating materials, including ceramic materials, including, but not limited to, cobalt-chromium-molybdenum alloy, titanium alloy, UHMWPE, PEEK, and zirconia-toughened alumina ("ZTA") ceramic. Furthermore, if the bearing member 60 is fabricated from a metal, it is contemplated 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 components and improve durability. In such exemplary embodiments, it is contemplated that a coating on the outer surface of the bearing member 60 may desirably be coated 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 may desirably substantially reduce the likelihood of metal debris being generated as a result of normal use, which may result from two metal components exerting shear forces relative to one another during normal movement.

[0084] tibial yoke FIG. 7A shows a side view of one embodiment of a prosthetic tibial yoke 40 (i.e., an exemplary second articular element) for use in the rotating hinge knee prosthetic implant assembly 1. In one exemplary embodiment, the tibial yoke 40 is a unibody (i.e., 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 head 24, may be separately manufactured into components that are desirably assembled into the tibial yoke 40 prior to insertion into the rotating hinge knee prosthetic implant assembly 1.

[0085] As seen in the side view of FIG. 7A , the body member 45 extends away from the lateral rotation axis TR, providing 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 a specific exemplary embodiment, the inner diameter of the lateral hinge bore 25 is sized to receive and articulate with the outer diameter of the region 97 of the bearing member 60 that defines the bearing bore 75. The bearing bore 75 receives the lateral hinge pin 50, as described elsewhere herein. It will be understood that other methods of using the bearing member 60 to reduce the coefficient of friction between the femoral box 80 and the lateral hinge pin 50 are within the scope of the present disclosure. In a specific exemplary embodiment, the edges of the body member 45 are radial.

[0086] The tibial axial post 20 further includes a distal end 26 disposed distally from the second end 77 of the body member 45. The distal end 26 may be chamfered or otherwise configured to facilitate insertion of the tibial axial post 20 into the axial bore 104 of the tibial stem 102. In certain exemplary embodiments, the distal end 26 may include a conical tip. In other exemplary embodiments, the distal end 26 may be substantially hemispherical. In still other exemplary embodiments, the distal end 26 may be selected from a group of shapes including a generally convex shape, a chamfered shape, a convex conical shape, a convex hemispherical shape, and a convex frustoconical shape. In certain exemplary embodiments, the tibial axial post 20 may define a post member chamber 23, thereby being hollow (see FIG. 7C ).

[0087] FIG. 7D is a bottom view of an exemplary tibial yoke 40 depicting the distal end 26 of the tibial axial post 20, the body 45 of the yoke 40, and the first and second sides 83, 84.

[0088] In certain exemplary embodiments, the body member 45 includes an extension stop portion 28 (FIGS. 7B, 7C) extending from the top of the body member 45 between the head 24 and the tibial axial post 20. As shown in FIG. 7A, in this embodiment, the offset distance D between the tibial axis of rotation A at the midline of the tibial axial post 20 and a parallel axis P extending perpendicularly through the transverse axis TR of the transverse hinge bore 25 is approximately 12 mm to approximately 15 mm. The offset distance D defines the center of rotation of the femur 200 relative to the tibia 100. Certain exemplary embodiments may position the center of rotation of the revised femur slightly anteriorly relative to the center of rotation of the natural femur. In these exemplary embodiments, it has been discovered that allowing the femur to rotate more anteriorly can contribute to better condylar loading and force transfer away from the femoral fastening mechanism. In situations where multiple yokes 40 are provided, the multiple yokes 40 may have different size dimensions, including different offset distances D. The surgeon can select an appropriately sized yoke 40 having an appropriately sized offset distance D based on the size and integrity of the patient's particular anatomy. 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 a snap-fit ​​pocket 29 formed on the top surface of the modular extension stop portion 28 to receive matching locking tabs 32A, 32B (FIG. 8B) of the modular extension stop 30.

[0089] Modular extension stop 8A-8C show views of one embodiment of an extension stop 30 for use with an exemplary rotating hinge knee prosthetic implant assembly 1. The modular extension stop 30 can be in an uninstalled position, in which the modular extension stop 30 is not engaged with the rotating hinge subassembly 10. The modular extension stop 30 can also be in an engaged position, in which the modular extension stop is engaged with the extension stop portion 28 of the rotating hinge subassembly 10. In FIG. 8A, the modular extension stop 30 can be seen to have a posterior, substantially flat or planar top surface 34. In the embodiment depicted in FIG. 10, the top surface 34 rises into an abutment portion 36. The abutment portion 36 fits within the patellar groove of the femoral component 205 when the knee is in extension. In certain exemplary embodiments, the abutment portion 36 can have a concave anterior portion that continues the patellar groove of the femoral component 205 when the knee is in extension. In this manner, the exemplary modular extension stop 30 can be configured to fit within and continue the patellar groove defined by the femoral component 205, allowing for a smooth transition between extension and flexion (see FIG. 12 ). A dip 39 separates the top surface 34 from the abutment portion 36. This dip 39 prevents overextension of the femoral component 205 (e.g., negative flexion, or bending the knee in the wrong direction).

[0090] In FIG. 10C, a front view of one embodiment of a modular extension stop 30 for use in an exemplary rotating hinge knee implant assembly of the present disclosure is disclosed.

[0091] The modular extension stop 30 may be made of a durable plastic material, such as UHMWPE. The modular extension stop 30 may be provided in different configurations to allow for various degrees of hyperextension, such as -10°, -5°, -3°, and 0° hyperextension. In this way, the surgeon can easily customize the modular extension stop 30 for each individual patient.

[0092] In an embodiment, the modular extension stop 30 is configured to snap-lock into the extension stop portion 28 of the tibial axial post 20. In the embodiment 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 respective snap member stems 38A, 38B. The snap members 32A, 32B can fit into snap-fit ​​pockets 29 in 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 are not bendable around the snap-fit ​​stems 38. 10A, 10B, and 10C, snap members 32A, 32B of FIGS. 8A, 8B, and 8C can fit into snap-fit ​​pockets 29 in extension stop portion 28 of yoke 40 when modular extension stop 30 is in the installed position. All protrusion-receptacle locking structures capable of selectively mechanically engaging modular extension stop 30 with extension stop portion 28 of yoke 40 are considered within the scope of this disclosure.

[0093] 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 may be manufactured as part of the yoke 40, or the extension stop 30 may be permanently affixed to the extension stop portion 28 in a manner that prevents replacement of the extension stop 30 on the yoke 40 during surgery.

[0094] Tapered Head Fasteners 9 shows a top perspective view of one embodiment of a femoral fastener 210 for use in the rotating hinge knee prosthetic implant assembly 1 of the present disclosure. In the illustrated embodiment, the femoral fastener 210 includes a threaded tip 211, a tapered head 212 on a rear end 215, and a smooth shank portion 214 between the threaded tip 211 and the tapered head 212. The threads 216 are typically machined threads. The threads 216 of the threaded portion approaching the threaded tip 211 are desirably chamfered or tapered to facilitate installation of the femoral fastener 210 into the femoral box fixation bore 81. That is, the diameter of the femoral fastener 210 at the threaded tip 211 is desirably smaller than the inner diameter of the femoral fixation bore 87. By guiding the smaller diameter threaded tip 211 into the relatively larger diameter femoral fixation bore 87, the surgeon is able to initially insert the threaded tip 211 of the femoral fastener 210 into the femoral fixation bore 87 with less precision, thereby facilitating engagement of the femoral box 80 with the femoral component 205 via the femoral fastener 210.

[0095] To eliminate the possibility of cross-seating, the surgeon may desirably begin inserting the femoral fastener 210 (if the femoral fastener 210 has threads 216) by first rotating the femoral fastener 210 in the opposite direction from the engagement direction. This allows the leading threads of the femoral fastener 210 to eventually drop below the leading edge of the threads of the femoral fixation bore 87. This may produce an audible click, and the surgeon need only register the sudden change in position. Once the surgeon registers the click or thread engagement, the surgeon may then begin rotating the femoral fastener 210 in the engagement direction.

[0096] When the femoral fastener 210 threads into the femoral fixation bore 87 of the femoral component 205, the tapered head 212 automatically locks into the femoral box fixation bore 81 to prevent the femoral fastener 210 from backing out of the femoral component 205. The tapered locking configuration of the femoral fastener 210 enables distal assembly of the rotating hinge knee prosthesis implant assembly 1. By "distal assembly," we mean the assembly on the femoral component 205, which has been secured to the distal portion of the patient's resected femur 200 by this point in the installation procedure. It is envisioned that by flexing the knee during the subassembly installation procedure, the surgeon may have improved access to the femoral box cavity 280, particularly compared to other hinge knee prostheses that require the hinge component to be secured to the tibial component 105. The tibial component 105 may be more obstructed by the patient's soft tissue by this stage. In one particular exemplary embodiment, the self-locking taper angle is 8 degrees, although different tapers can be used, such as taper angles between 8 and 12 degrees, inclusive.

[0097] The femoral fastener 210 may be fabricated from any clinically proven biocompatible material, including, but not limited to, cobalt-chromium-molybdenum alloys and titanium alloys. It should be understood that the femoral fastener 210 may comprise any device configured to securely engage the femoral box 80 to the femoral component 205. Such devices may include, but are not limited to, pins with protruding elements, pins with negative elements configured to receive protruding elements from the femoral box 80 or other interlocking assemblies, bolts, rivets, clamps, interlocking teeth, interlocking hooks, and other protrusion-receptor locking mechanisms configured to securely engage the femoral box 80 to the femoral component 205 and prevent the femoral fastener 210 from receiving the load of the femur 200.

[0098] Furthermore, without being bound by theory, it is contemplated that the exemplary embodiments disclosed herein allow the femoral load of the femur (i.e., the weight of the femur and the body above the femur due to gravity) to be transferred primarily from the femur 200 and femoral component 205 to the condyle pads 228, 229 of the meniscus insert 150.

[0099] However, in situations where a subset of the femoral load is transferred to the rotating hinge subassembly 10, it is envisioned that the force is transferred from the femur 200 and femoral component 205 to the femoral 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 transferred 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 torsional loads experienced by the tibia during normal locomotion. The femoral load is not transferred to the femoral fastener 210. Therefore, the femoral fastener 210 may be shorter than a fastener configured to axially align with the tibial axis of rotation. In an exemplary embodiment, the length of the femoral fastener 210 may be, for example, approximately 14 mm. Other compatible femoral fasteners 210 can have lengths ranging from about 10 mm to about 18 mm.

[0100] Transferring femoral loads through a component other than the femoral fastener 210, which is configured to mechanically connect the rotating hinge subassembly 10 to the femoral component 205, can facilitate installation of the prosthesis as well as prolong the useful life of the prosthesis over 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 into the femoral component 205 through the femoral box 80, can contribute to an overall reduction in the time required to perform the surgical procedure.

[0101] Femoral component In embodiments, the femoral component 205 includes features for improved joint function. A femoral stem 155 is typically inserted into the femoral bore to seat the femoral component 205 on the resected femoral condyles. The femoral component 205 is configured to provide greater than 120 degrees of flexion. The femoral component 205 may be configured to provide uninterrupted patellar kinematics. In certain exemplary embodiments, a femoral box cavity 280 (FIG. 2A) approximately 16 to 18 mm in length is provided for the femoral box 80 of the rotating hinge subassembly 10. The femoral component 205 may be configured to be compatible with existing revision components, such as femoral augments, offset adapters, and modular stems, as well as the modular extension stop 30.

[0102] In certain embodiments, both condyles 218, 219 can have a constant radius of curvature, thus providing a ball and socket function on both sides. In other embodiments, the condyles 218, 219 can include multiple radii, thereby defining a J-curve.

[0103] Tibial component Referring to FIG. 4, the tibial component 105 includes a matching axial bore 104 for receiving the tibial axial post 20 .

[0104] The meniscal insert 150 can be adapted for a mobile bearing mechanism. The proximal / superior side of the tibial base portion 101 is provided with structural features for capturing the meniscal insert 150 in a mobile bearing relationship, such as a hook feature as further described with reference to Figures 3A and 3B.

[0105] How to use In operation, the rotating hinge knee prosthetic implant assembly 1 of the present disclosure is designed to allow distal fixation of the rotating hinge subassembly 10 using an anterior approach.

[0106] The rotating hinge subassembly 10 may be configured to be pre-assembled, as shown in FIG. 2B, rather than being pre-assembled with the femur or tibia as in previous systems.

[0107] After the femoral component 205 and the tibial component 105 are implanted, the rotating hinge subassembly 10 is inserted and rotated into place within the femoral component 205. A single tapered head femoral fastener 210 can then be inserted to connect the hinge subassembly 10 to the femoral component 205.

[0108] As can be seen from the foregoing description, exemplary embodiments of the present invention have various advantages over conventional implants and methods, including, but not limited to:

[0109] The rotating hinge subassembly 10 is configured to be pre-assembled by itself, rather than being 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 rotating hinge subassembly 10 is inserted into the axial bore 104 of the tibial component 105. The rotating hinge subassembly 10 can then be rotated into place, and the femoral box 80 can be fitted into the femoral 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 rotating hinge knee prosthetic implant assembly 1, which in turn allows for the preservation of more surrounding soft tissue. Preserving surrounding soft tissue may contribute to a shorter recovery time. An exemplary yoke 40 may have a post length L of approximately 40 mm to approximately 70 mm. Additionally, the implant configuration allows for a surgical method requiring only one incision to install the rotating hinged knee prosthetic implant 1 because lateral placement of the hinge pin is eliminated.

[0110] Without being bound by theory, it is contemplated that certain exemplary embodiments disclosed herein, when combined with surgical practice, can constrain five of six directions of movement of the tibial component 105 and the femoral component 205, thereby allowing the surgeon to pre-align the tibial component 105 and the femoral component 205 along a plane of motion for ease of installation. In practice, it will be understood that the femur 200 and the tibia 100 each include six cardinal directions of movement. That is, all movement of the femur 200 and the tibia 100 (and therefore any component disposed on the femur or tibia) can be reduced to the sum of movement along the six cardinal directions of movement.

[0111] 11A (and prior to installation of the rotating hinge subassembly 10), the femoral component 205 and the tibial component 105 can move relative to one another according to six cardinal directions of movement: the femoral component 205 can move laterally (and vice versa) with respect to the tibial component 105 (i.e., in the anterior-posterior direction x, in a rotational direction about the anterior-posterior axis AP, in a rotational direction about the medial-lateral direction y, in a rotational direction about the medial-lateral direction ML, in an inferior-superior direction z along the parasagittal plane, and in the transverse plane (see 198 in FIG. 2D ) along a rotational direction about the inferior-inferior axis UD).

[0112] An exemplary method involves placing the tibial axial post 20 of the yoke 40 into the axial bore 104 of the tibial stem 102 while the knee is in flexion. The practice of aligning the femoral box cavity 280 of the femoral component 205 with the femoral box 80 effectively constrains five of the six cardinal directions of motion of the femoral component 205 relative to the tibial component 105, to the extent that the femoral component 205 is typically movable primarily upward and downward along the parasagittal plane z. Any movement in the anterior-posterior direction x, or about the medial-lateral axis on the transverse plane b, is considered minimal, if any. Using hands and instruments, the range of motion of the femur and tibia can be constrained to align the femoral box cavity 280 of the femoral component 205 with the femoral box 80 of the rotational hinge subassembly 10.

[0113] 11B depicts the rotating hinge subassembly 10 in an engaged position, i.e., the first articulating element is disposed within the femoral component and engages the femoral component in a projection-receptor locking manner.

[0114] In embodiments, the modular extension stop 30 is configured to interface with the femoral component 205. The modular extension stop 30 can be variable in size and configured to snap-fit ​​into the body 45 of the yoke 40, allowing for reduced inventory. The variable size of the modular extension stop 30 can also be selected to accommodate a particular patient's anatomy (e.g., the modular extension stop 30 can be customized based on pre-operative images taken during the pre-operative planning phase, or the modular extension stop 30 can be selected from a pre-existing selection of modular extension stops 30 provided in a kit). Such modular extension stops 30 can be further selected to address specific deficiencies in the patient's anatomy and prevent recurrence. The modular extension stop 30 has locking tabs 32A, 32B extending from the bottom of the modular extension stop 30, which extend into snap-fit ​​pockets 29 in the extension stop portion 28 of the yoke 40 when the modular extension stop 30 is in the installed position.

[0115] A single tapered head femoral fastener 210 connects the rotating hinge subassembly 10 to the femoral component 205. The use of a single fastener simplifies assembly and reduces the risk of the components loosening relative to one another during use.

[0116] The components of the rotating hinge knee prosthetic 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 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 exemplary kit, an 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 arrangement and combination of tibial axial post lengths L and tibial yoke 40 body dimensions. Each rotating hinge subassembly 10 may desirably have a different offset distance D and post length L than the other rotating hinge subassemblies 10 in the kit.

[0117] An exemplary kit may include any suitable embodiment of the rotating hinge subassembly 10, variations of the rotating hinge subassembly 10 described herein, and any other rotating hinge subassembly 10 according to an embodiment. An exemplary kit may 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 within the scope of this 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 an embodiment are considered within the scope of this 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 an embodiment are considered within the scope of this disclosure.

[0118] The selection of the appropriate number or type of rotating hinge subassemblies 10, modular extension stops 30, tibial components 105, and femoral components 205 to include 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.

[0119] FIG. 12 depicts a cross-sectional side view of an exemplary embodiment including a different modular extension stop 30. The cross-sectional view is taken from a parasagittal plane that vertically bisects the rotating hinge knee prosthetic implant assembly 1. As can be seen, at zero degrees of flexion, the patellar groove 115 of the femoral component 205 is sized and configured to abut against the extension stop 30. In this manner, the rotating hinge knee prosthetic implant assembly 1 cannot move into hyperextension or exceed its built-in degree of hyperextension. In the exemplary embodiment of FIG. 12, the femoral fastener mechanism (i.e., in the depicted embodiment, the femoral fastener 210) is non-axially aligned with the tibial axis of rotation A when the rotating hinge knee prosthetic implant assembly 1 is in full extension. That is, the central axis F of the femoral fastener is not aligned with the tibial axis of rotation A. It is envisioned that this misalignment when the knee is in extension may further reduce the transfer of any torsional forces from the femur 200 to the femoral fastening mechanism, thereby reducing the incidence of wear on the femoral fastening mechanism during normal use.

[0120] FIG. 13 is a schematic perspective view of anatomical planes for a human 600. A transverse plane 198 is shown extending across the human 600. While the transverse plane 198 is shown as bisecting the human horizontally at the human's midpoint, it will be understood that the transverse plane 198 is an imaginary plane that can be imagined to lie horizontally anywhere on the human 600 between a medial point and a distally disposed lateral point along the shortest possible line. Thus, the transverse plane 198 can be said to divide the human 600 into superior and inferior portions. A sagittal plane 400 is shown as bisecting the human 600 vertically in the anterior-posterior direction through the midpoint. While the sagittal plane 400 is shown as bisecting the human, it will be understood that the sagittal plane 400 is an imaginary plane that can be imagined to lie vertically anywhere on the human 600 between a posterior point and a distally disposed anterior point along the shortest possible line. Thus, the sagittal plane 400 divides the human into left and right halves. A sagittal plane 400 that is not disposed at the center of the human 600 is commonly known as a sagittal plane (see z in FIG. 11A ). A coronal plane 500 is shown as vertically bisecting the human 600 through the midpoint. While the coronal plane 500 is shown as bisecting the human, it will be understood that the coronal plane 500 is an imaginary plane that can be imagined to lie vertically anywhere on the human 600 between a medial point and a distally disposed lateral point along the shortest possible line. Thus, the coronal plane 500 divides the human into an anterior portion and a posterior portion.

[0121] An exemplary knee joint prosthesis includes a tibial component, a femoral component, and a rotating hinge subassembly configured to be coupled to the femoral component and having a portion configured to be disposed on the tibial component while being rotatable about a rotation axis within the tibial component, the rotating hinge subassembly including a first articular element and a second articular element rotatable about the rotation axis and coupled to the first articular element, the first articular element being in an engaged position and being in a disengaged position relative to the first articular element. a first articulation element disposed within the femoral component and defining an engagement position in which the first articulation element engages the femoral component in a protrusion-receptor locking manner and a disengagement position in which the first articulation element is completely separated from the femoral component, the first articulation element defining an engagement direction, the first articulation element being movable relative to the femoral component to transfer the first articulation element from the disengagement position into the engagement position, the engagement direction running transverse to the axis of rotation, the protrusion and receiver element of the protrusion-receptor locking manner extending non-parallel to the engagement direction.

[0122] An exemplary rotating hinge subassembly includes a tibial yoke including a head defining a lateral hinge bore extending through first and second sides 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 from the tibial axial post by an offset distance; and a femoral box including first and second arms extending posteriorly from the main body portion. the main body portion defines a femoral box fixation bore extending therethrough, the first arm and the second arm defining axially aligned first and second bores, respectively, the first arm disposed adjacent a first side and the second arm disposed adjacent a second side, such that the first and second bores are axially aligned with the lateral hinge bore; and a lateral hinge pin extending through the lateral hinge bore and into the first and second bores.

[0123] An exemplary rotating hinge subassembly includes a tibial yoke including a head defining a lateral hinge bore extending through first and second sides 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 from the tibial axial post by an offset distance; and a femoral box including first and second arms extending posteriorly from a main body portion, the main body portion extending through the main body portion. a femoral box fixation bore extending across the femoral box arm, the first arm and the second arm defining axially aligned first and second bores, respectively, the first arm disposed adjacent the first side and the second arm disposed adjacent the second side, such that the first and second bores are axially aligned with the lateral hinge bore; and a lateral hinge pin extending through the lateral hinge bore and into the first and second bores, the lateral hinge pin not extending beyond the arms of the femoral box.

[0124] An exemplary knee joint prosthesis includes a tibial component and a femoral component, the femoral component having an area defining a femoral receiving bore, and a pre-assembled rotating hinge subassembly configured to rotatably couple the tibial component to the femoral component about an axis of rotation, the pre-assembled rotating hinge assembly including a first articular element and a second articular element rotatable about the axis of rotation and coupled to the first articular element, the first articular element having an area defining the first receiving bore, defines an engaged position, where the first joint element is disposed on the femoral component whereby the first receiving bore and the femoral receiving bore are aligned and the 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, the first joint element 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 transverse to the axis of rotation and the femoral bore extending in a non-parallel manner in the engagement direction.

[0125] In such an exemplary embodiment, the first articular element may be a femoral box. Such an exemplary embodiment may further include an extension stop.

[0126] An exemplary rotating hinge knee prosthetic implant assembly includes a rotating hinge subassembly having a femoral box configured to hingeably articulate 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 thereof, the second end of the body member being disposed distally from the first end thereof, the femoral box being configured to hingeably articulate about a tibial yoke via a femoral fastener. and configured to mechanically engage the femoral component, such that the femoral fastener is non-axially aligned with the axis of rotation of the tibia when the knee is in flexion (e.g., when the rotating hinge knee prosthetic implant is hinged about the lateral pin at flexion angles greater than 0 degrees) or extension (e.g., when the rotating hinge knee prosthetic implant is hinged about the lateral pin at flexion angles equal to or less than 0 degrees), and the laterally extending hinge pin of the rotating hinge subassembly does not mechanically engage the femoral component in the installed configuration.

[0127] An exemplary prosthetic tibial yoke for a rotating 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, wherein the head defines a lateral hinge bore extending through first and second lateral sides of the head, the lateral hinge bore defining a lateral axis extending laterally through the lateral hinge bore, the tibial axial post defining a midline axis extending longitudinally through the tibial axial post, a reference axis extending substantially perpendicularly through the lateral axis and substantially parallel to the midline axis, and an offset distance separating the midline axis from the reference axis.

[0128] In an exemplary embodiment of the tibial yoke, the tibial axial post, body member, and head are a single, continuous structure.

[0129] In an exemplary embodiment of the tibial yoke, the tibial axial post further includes a distal end disposed distally from the second end of the body member, and in such 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 frustoconical shape.

[0130] In an exemplary embodiment of the tibial yoke, the offset distance is selected from a range of distances consisting essentially of about 12 mm to about 15 mm.

[0131] In an exemplary embodiment of the tibial yoke, the tibial axial post further includes a post length, the post length having a value between about 40 mm and about 70 mm.

[0132] Exemplary tibial yokes may further include an extension stop portion extending between the head and the tibial shaft post, the extension stop portion including a snap-fit ​​pocket. In such exemplary embodiments, the tibial yoke may further include a modular extension stop having a locking tab extending from a bottom of the modular extension stop, the locking tab configured to extend into the snap-fit ​​pocket in the extension stop portion of the yoke when the modular extension stop is in the installed position.

[0133] An exemplary rotating hinge subassembly includes a tibial yoke including a head defining a lateral hinge bore extending through first and second sides 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 from the tibial axial post by an offset distance; and a femoral box including first and second arms extending posteriorly from a main body portion, the main body portion being adapted to engage with a femoral box component of a knee joint prosthesis. a femoral box having a femoral fastening mechanism configured to engage a lateral surface of a femoral box cavity of the component, the first arm and the second arm defining axially aligned first and second arm bores, respectively, the first arm being disposed adjacent a first side surface and the second arm being disposed adjacent a second side surface such that the first and second arm bores are axially aligned with the lateral hinge bore; and a lateral hinge pin extending through the lateral hinge bore and into the first and second arm bores.

[0134] In an exemplary embodiment of the rotating hinge subassembly, the rotating hinge subassembly is pre-assembled.

[0135] In an exemplary embodiment of the rotating hinge subassembly, the first arm and the second arm are disposed flush against a side of the head.

[0136] In an exemplary embodiment of the rotating hinge subassembly, the lateral hinge pin does not extend beyond the first and second arms of the femoral box.

[0137] In an exemplary embodiment of the rotating hinge subassembly, the rotating hinge assembly may further include a bearing disposed between the first side of the head and the first arm.

[0138] In an exemplary embodiment of the rotating hinge subassembly, the femoral box is made from a material from a 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 articulating materials.

[0139] In an exemplary embodiment of the rotating hinge subassembly, the femoral fastening mechanism is selected from the group consisting essentially of a femoral box fixation bore configured to receive a femoral fastener, a protrusion, a receiver, a plurality of protrusions, a plurality of receivers, a magnet, a clamp, a hook, a lip, a bonding agent, an adhesive, and combinations thereof.

[0140] An exemplary rotating hinge subassembly includes a tibial yoke, the 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 first and second lateral sides of the head, the lateral hinge bore defining a lateral axis extending laterally through the lateral hinge bore, the tibial shaft post defining a midline axis extending longitudinally through the tibial shaft post, a reference axis extending orthogonally through the lateral axis and parallel to the midline axis, an offset distance separating the midline axis from the reference axis, and a femoral box, the first arm extending posteriorly from the main body portion, and a second arm extending posteriorly from the main body portion. a second arm extending posteriorly from the first arm, the second arm opposing the first arm, the main body portion defining a femoral fastening mechanism configured to engage a lateral surface of a femoral box cavity of a femoral component of a knee joint prosthesis, the first arm defining a first bore, the second arm defining a second bore, the first bore axially aligned with the second bore, the first arm disposed adjacent the first side and the second arm disposed adjacent the second side, such that the first and second bores are axially aligned with the lateral hinge bore; and a lateral hinge pin extending through the lateral hinge bore and into the first and second bores, thereby hingeably engaging the femoral box with the head of the yoke.

[0141] An exemplary knee joint prosthesis comprises a tibial component, a femoral component, and a rotating hinge subassembly having a first joint element configured to be coupled to the femoral component while being rotatable about an axis of rotation within the tibial component while having a second joint element configured to be disposed on the tibial component, the rotating hinge subassembly comprising the first joint element and the second joint element hingedly coupled to the first joint element, the first joint element defining an engaged position, where the first joint element is disposed within and lockingly engages the femoral component, and a disengaged position, where the first joint element is completely separated from the femoral component, the first joint element defining an engagement direction, the first joint element being movable relative to the femoral component to transfer the first joint element from the disengaged position into the engaged position, the engagement direction running sagittal to the axis of rotation.

[0142] In an exemplary knee joint prosthesis, the locking scheme is a projection-receiver locking scheme, where the projections and receiver elements of the projection-receiver locking scheme are disposed coplanar with a parasagittal plane extending non-parallel to the engagement direction. In such an exemplary knee joint prosthesis, the projection-receiver locking scheme may include a first articular element having an area defining a first receiving bore, and a femoral component having an area defining a femoral receiving bore, where 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.

[0143] In the exemplary knee prosthesis, the parasagittal plane extends through the midpoint of the femoral component.

[0144] In an exemplary knee joint prosthesis, the locking mechanism is a bonded or magnetic locking mechanism.

[0145] While the present invention has been described in terms of specific embodiments, it is anticipated that alterations and modifications thereof will no doubt become apparent to those skilled in the art. It is, therefore, intended that the following claims be interpreted to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Claims

1. the tibial yoke (40) having a body member (45) with a head (24) disposed at a first end (67); a tibial axial post (20) extending from a second end (77) of the body member (45), the second end (77) being distally disposed from the first end (67); a head (24) defining a lateral hinge bore (25) extending through the first and second sides; the lateral hinge bore (25) defining a transverse axis (TR) extending across it; the tibial axial post (20) defining a median axis extending longitudinally therethrough; a reference axis extending substantially perpendicular to the transverse axis (TR) and substantially parallel to the median axis; an offset distance (D) separating the median axis from the reference axis, the offset distance (D) being selected from a range of distances consisting essentially of 12 mm to 15 mm; a femoral box (80); a first arm (82) and a second arm (86) extending rearward from a main body portion (91); a 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 endoprosthesis; a lateral hinge pin (50) extending through said lateral hinge bore (25) into said first arm bore (85) and said second arm bore (88); a first bearing (60) disposed between the first side surface of the head (24) and the first arm (82); a second bearing (60) disposed between the second side of the head (24) and the second arm (86); Equipped with the first arm (82) and the second arm (86) define axially aligned first and second arm bores (85, 88), respectively, the first arm (82) disposed adjacent the first side surface and the second arm (86) disposed adjacent the second side surface, the first arm bore (85) and the second arm bore (88) being axially aligned with the lateral hinge bore (25); the first arm (82) and the second arm (86) are disposed on opposite sides of the first and second sides of the head (24), and the lateral hinge pin (50) does not extend beyond the first arm (82) and the second arm (86) of the femoral box (80); One of the first bearing and the second bearing is made of polyetheretherketone. Rotating hinge knee subassembly (10).

2. 2. The rotating hinge knee subassembly (10) of claim 1, wherein the tibial axial post (20), the body member (45), and the head (24) are a single, continuous structure.

3. The rotating hinge knee subassembly (10) of claim 1, wherein the tibial shaft post (20) further comprises a post length (L), the post length (L) having a value between about 40 mm and about 70 mm.

4. an extension stop portion (28) extending between the head (24) and the tibial axial post (20); The extension stop portion (28) has a snap-fit ​​pocket (29), 2. The rotating hinge knee subassembly of claim 1, wherein the tibial yoke further comprises a modular extension stop including a locking tab extending from a bottom of the modular extension stop, the locking tab configured to extend into a snap-fit ​​pocket in an extension stop portion of the yoke when the modular extension stop is in an attached position.

5. 2. The rotating hinge knee subassembly of claim 1, wherein the femoral box is formed from a material from a 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 and clinically proven joint materials.

6. 2. The rotating hinge knee subassembly (10) of claim 1, wherein the femoral fixation mechanism is selected from the group consisting essentially of a femoral box fixation hole (81) configured to receive a femoral fixator (210), a protrusion, a receiver, a plurality of protrusions, a plurality of receivers, a magnet, a clamp, a hook, a lip, an adhesive, a bonding material, and combinations thereof.

Images