Anti-dislocation device for constrained artificial knees

Abstract

To provide anti-luxation devices for a constrained prosthetic knee.SOLUTION: The techniques described herein relate to a prosthesis assembly. The prosthesis assembly may include a femoral component, a tibial bearing component engaged by the femoral component, and a tibial baseplate. The tibial baseplate can include a bushing received in a recess in the tibial baseplate, and a hinge post coupled to the femoral component and the bushing. The hinge post can be at least partially received by the bushing. The prosthesis assembly may include a capture element coupled to the tibial baseplate. The capture element can be engaged by at least one of the bushing and hinge post to limit distraction of the femoral component from the tibial bearing component and tibial baseplate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] Priority claims This application claims the benefit of U.S. Provisional Patent Application No. 63 / 434,574, filed December 22, 2022, and the benefit of U.S. Provisional Patent Application No. 63 / 450,878, filed March 8, 2023. The benefit of priority claimed herein of each of these U.S. provisional patent applications, and each of these U.S. provisional patent applications, is incorporated herein by reference in its entirety.

[0002] The present subject matter relates to orthopedic prostheses, and more particularly to orthopedic prostheses used in constrained knee arthroplasty. [Background technology]

[0003] Orthopedic procedures and prostheses are widely used to repair and / or replace damaged bones and tissues within the human body. Generally, the knee is formed by a pair of condyles located on the distal portion of the femur. The inferior surfaces of these condyles rest on correspondingly shaped proximal plateaus on the tibia. The femur and tibia are connected by ligaments, such as the posterior cruciate ligament, lateral collateral ligament, medial collateral ligament, and anterior cruciate ligament. These ligaments provide stability to the knee joint.

[0004] A prosthetic knee joint can be considered constrained or unconstrained. For purposes of this discussion, a constrained prosthetic knee system includes a femoral prosthesis and a tibial prosthesis. These prostheses are mechanically linked, or constrained, to one another to limit relative motion between the femoral and tibial prostheses. Common mechanisms for such mechanical linkage include hinges, bands, or other linkage structures. An unconstrained prosthetic knee system includes a femoral prosthesis and a tibial prosthesis that are not mechanically linked. An unconstrained knee utilizes the patient's existing ligaments and other soft tissues to provide joint stability. With this in mind, a constrained prosthetic knee may be particularly applicable in cases where the patient is missing ligaments and / or existing ligaments do not provide sufficient support and stability to the knee.

[0005] Various constrained knee designs are known. One such design includes a hinge post. This hinge post configuration is positioned within (and has an end protruding from) the tibial baseplate and is connected to the femoral component. One hinge post configuration, for example, is the applicant's proprietary NexGen® Rotating Hinge Knee. Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure relates generally to an improved constrained knee prosthesis, and more particularly to a constrained knee prosthesis utilizing a hinge post. Some constrained knee prostheses with hinge posts utilize a design that allows the femoral component (and hinge post) to move freely in a generally proximal / distal direction relative to the tibial baseplate and tibial bearing component. This arrangement can allow for distraction of the knee joint. However, the inventors have recognized that certain segments of a patient receiving a constrained knee prosthesis with a hinge post may have insufficient soft tissue within the knee joint to prevent distraction of the femoral component from the tibial baseplate and tibial bearing component, and subsequently, to prevent dislocation. Dislocation can result in pain and other complications for the patient.

[0007] Thus, the inventors have recognized that for this particular segment of patients with insufficient soft tissue, distraction of the femoral component from the tibial baseplate and tibial bearing component should be limited. The inventors have recognized various techniques and devices, such as capture elements, that can interact with the hinge posts and bushings of a constrained knee prosthesis to limit distraction. As used herein, the terms "limiting distraction," "limit distraction," "limits distraction," "limited distraction," or similar terms include various prosthetic configurations, as discussed further herein. For example, one example of limited distraction allows the femoral component some proximal / distal movement (e.g., from a few millimeters to a few centimeters) relative to the tibial baseplate and tibial bearing component. However, this degree of motion is ultimately limited / arrested / stopped, preventing further proximal / distal motion of the femoral component, such as proximal / distal motion that could result in dislocation of the femoral component from the tibial baseplate and tibial bearing component. This configuration for a prosthesis should be contrasted with a configuration for a prosthesis that allows for “full distraction.” In a prosthesis that allows for “full distraction,” proximal / distal motion of the femoral component relative to the tibial baseplate and tibial bearing component is not ultimately limited / arrested / stopped by the components of the prosthesis, and, if insufficient soft tissue is present, dislocation of the knee joint may result. Terms such as “limiting distraction,” “limit distraction,” “limits distraction,” “limited distraction,” or similar terms include prosthesis configurations in which proximal / distal motion of the femoral component is substantially completely restricted aside from micromotion.The term "micromotion" refers to the small movements that may exist between prosthetic components, such as between the tibial baseplate and capture element, respectively, when a force is applied. Such small movements may occur as a result of material deformation in one or both of the interacting components, or may result from, for example, a small amount of space or clearance between the components. Micromotion is distinct from larger component movements, such as the proximal / distal movement of the femoral component relative to the tibial baseplate and tibial bearing components.

[0008] Additional features and advantages of the various embodiments provided herein are discussed and / or will become apparent to those skilled in the art.

[0009] To further illustrate the devices, systems, and methods disclosed herein, the following non-limiting examples are provided, hereafter referred to as techniques. These examples / techniques can be combined in any manner. [Means for solving the problem]

[0010] In some aspects, the technology described herein relates to a prosthetic assembly for a constrained knee including: a femoral component; a tibial bearing component engaged by the femoral component; a tibial baseplate having a distal surface, a proximal surface opposite the distal surface facing the tibial bearing component, an outer edge extending between the proximal and distal surfaces, and a keel extending distally from the distal surface; a bushing received within a recess in the tibial baseplate; a hinge post coupled to the femoral component and the bushing, the hinge post being at least partially received by the bushing; and a capture element coupled to the tibial baseplate, the capture element being engaged by at least one of the bushing or the hinge post to limit distraction of the femoral component from the tibial bearing component and the tibial baseplate.

[0011] In some aspects, the technology described herein relates to a prosthesis assembly wherein the capture element comprises one of a snap-fit ​​component or a threaded nut configured to be at least partially received within the recess of the tibial baseplate, the capture element having a through hole configured to allow at least a portion of the hinge post to pass through the capture element.

[0012] In some aspects, the technology described herein relates to a prosthetic assembly in which the capture element is spaced proximally from the bushing by a predetermined distance, the distance allowing a limited degree of distraction of the femoral component from the tibial bearing component and tibial baseplate.

[0013] In some aspects, the technology described herein relates to a prosthetic assembly in which the capture element is proximal to the bushing and adjacent to the proximal end of the bushing, thereby completely limiting distraction of the femoral component from the tibial bearing component and tibial baseplate.

[0014] In some aspects, the technology described herein relates to a prosthesis assembly in which a hinge post is coupled to the bushing by a first thread, the first thread interlocking with a second thread of the bushing.

[0015] In some aspects, the technology described herein relates to a prosthesis assembly, wherein the interlocking of the first thread and the second thread positions the bushing in a desired position relative to the capture element.

[0016] In some aspects, the technology described herein provides a prosthetic system for a constrained knee, the prosthetic system including: a femoral component; a tibial bearing component configured to articulate with the femoral component; a tibial baseplate having a distal surface, a proximal surface opposite the distal surface facing the tibial bearing component, an outer edge extending between the proximal and distal surfaces, and a keel extending distally from the distal surface; a bushing configured to be inserted into a recess in the tibial baseplate; and a prosthetic baseplate configured to couple with the femoral component and adapted to support the bushing. and a capture element configured to couple to the tibial baseplate, the capture element having a throughbore configured to allow at least a portion of the hinge post to pass through the capture element, the capture element configured to be engaged by at least one of the bushing or the hinge post to limit distraction of the femoral component from the tibial bearing component and the tibial baseplate when coupled to the tibial baseplate.

[0017] In some aspects, the technology described herein relates to a prosthetic system in which a hinge post is configured to couple to the bushing by a first thread, the first thread engaging a second thread of the bushing.

[0018] In some aspects, the technology described herein relates to a prosthetic system in which, when the first thread is coupled with the second thread, the bushing is positioned in a desired position relative to the capture element.

[0019] In some aspects, the technology described herein relates to a prosthetic system in which the capture element is configured to be adjacent to the bushing or spaced a predetermined distance from the bushing when the bushing is positioned in a desired location.

[0020] In some aspects, the technology described herein relates to a prosthetic system in which the capture element includes one of a snap-fit ​​component or a threaded nut configured to be at least partially received within the recess of the tibial baseplate.

[0021] In some aspects, the technology described herein relates to a prosthetic system in which the capture element, when assembled to the bushing, is spaced proximally from the bushing by a predetermined distance, the distance allowing a limited degree of distraction of the femoral component from the tibial bearing component and tibial baseplate.

[0022] In some aspects, the technology described herein relates to a prosthetic system in which, when assembled to the bushing, the capture element is located proximally relative to the bushing and abuts the proximal end of the bushing, thereby completely limiting distraction of the femoral component from the tibial bearing component and tibial baseplate.

[0023] In some aspects, the technology described herein relates to a method of assembling a prosthesis assembly for a constrained knee, the method including coupling a hinge post to a femoral component, inserting a bushing into a recess in a tibial baseplate, positioning a capture element in the recess of the tibial baseplate, inserting the hinge post into the recess through the capture element once coupled to the femoral component, coupling the hinge post with the bushing in the recess, and inserting a tibial bearing component between the femoral component and the tibial baseplate.

[0024] In some aspects, the technology described herein relates to a method in which positioning the capture element within the recess of the tibial baseplate includes biasing the capture element into engagement with one or more retention features of the tibial baseplate.

[0025] In some aspects, the technology described herein relates to a method in which positioning the capture element within the recess of the tibial baseplate includes inserting the capture element into a receptacle adjacent to and in communication with the recess, and moving the capture element laterally from the receptacle into the recess.

[0026] In some aspects, the technology described herein relates to a method in which positioning the capture element within the recess of the tibial baseplate includes threading the capture element into the tibial baseplate.

[0027] In some aspects, the technology described herein relates to a method whereby the connection between the hinge post and the bushing within the recess positions the bushing in a desired position relative to the capture element.

[0028] In some aspects, the techniques described herein relate to methods further including engaging the capture element with at least one of the bushing or the hinge post to limit distraction of the femoral component from the tibial bearing component and tibial baseplate.

[0029] In some aspects, the technology described herein relates to a prosthesis assembly in which the capture element is initially coupled to the bushing by a frangible bond, and the frangible bond is released by threading the hinge post and the bushing to separate the capture element from the bushing.

[0030] In some aspects, the technology described herein relates to a prosthetic system in which the capture element is initially coupled to the bushing by a frangible bond, and the frangible bond is released by threading the hinge post and the bushing to separate the capture element from the bushing.

[0031] In some aspects, the technology described herein relates to a method, wherein coupling the hinge post to the bushing within the recess disengages the capture element from the bushing.

[0032] In the drawings, which are not necessarily to scale, like reference numerals may represent like components in different drawings. Like reference numerals with different subscripts may represent different instances of like components. The drawings generally illustrate, by way of example, but in no way by way of limitation, various embodiments discussed in the present specification. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 illustrates a knee joint structure that provides a suitable environment in which a constrained prosthesis assembly according to one embodiment of the present application may be utilized. [Figure 2] FIG. 2 illustrates a knee joint structure that provides a suitable environment in which a constrained prosthesis assembly according to one embodiment of the present application may be utilized. [Figure 3] FIG. 3 shows a perspective view of a constrained knee prosthesis assembly according to one embodiment of the present application. [Figure 3A] 3A illustrates a perspective view of the constrained knee prosthesis assembly of FIG. 3 distracted by proximal / distal movement of the femoral component relative to the tibial baseplate and tibial bearing component according to one embodiment of the present application. [Figure 4] FIG. 4 shows an exploded view of the constrained knee prosthesis assembly of FIG. [Figure 5]FIG. 5 illustrates a cross-sectional view of a second embodiment of a constrained knee prosthesis assembly having a capture element configured to limit distraction of the femoral component relative to the tibial baseplate and / or tibial bearing component, according to one embodiment of the present application. [Figure 6] FIG. 6 illustrates a top view of the tibial baseplate and capture element of FIG. 5 with the capture element moved to a desired position within the recess of the tibial baseplate to limit distraction, according to one embodiment of the present application. [Figure 7] FIG. 7 shows various perspective views of an embodiment of a capture element according to one embodiment of the present application. [Figure 8] FIG. 8 illustrates a cross-sectional view along a sagittal plane of a tibial baseplate and tibial bearing component of a constrained knee prosthesis assembly similar to the embodiment of FIG. 5 but using another embodiment of a capture element that snaps into at least a portion of the recess in the tibial baseplate, according to one embodiment of the present application. [Figure 9A] FIG. 9A shows a cross-sectional view of the tibial baseplate and tibial bearing component of a third constrained prosthetic knee assembly having yet another embodiment of a capture element coupled to the tibial baseplate by a screw thread, according to one embodiment of the present application. [Figure 9B] FIG. 9B illustrates a perspective view of the capture element of FIG. 9A in isolation, with threads along the outer diameter, through-holes, and other features, according to one embodiment of the present application. [Figure 10] FIG. 10 shows a cross-sectional view of the tibial baseplate and tibial bearing component of a fourth constrained knee prosthesis assembly with a hinge post and bushing having a modified configuration compared to the previous embodiments. [Figure 11] FIG. 11 illustrates a cross-sectional view of the tibial baseplate and tibial bearing component of a fifth constrained knee prosthesis assembly in which at least the bushing has a modified configuration compared to the embodiment of FIG. 10, according to one embodiment of the present application. [Figure 11A] 11A shows a perspective view of the capture element and proximal portion of the bushing of FIG. 11. FIG. [Figure 11B] FIG. 11B illustrates a perspective view of the capture element and bushing of FIG. 11 separated and spaced apart to allow limited distraction, according to one embodiment of the present application. [Figure 12] FIG. 12 shows a cross-sectional view of the tibial baseplate and tibial bearing component of a sixth constrained knee prosthesis assembly in which at least the hinge post has a modified configuration compared to the previous embodiments to include an engagement mechanism. [Figure 13] FIG. 13 shows a perspective view of another embodiment of a hinge post that may be used with the constrained prosthetic knee assemblies discussed herein, including those shown in FIGS. 14-19. [Figure 14] FIG. 14 illustrates a perspective view of another embodiment of a capture element and bushing separated to allow limited separation, according to an embodiment of the present application. [Figure 15] FIG. 15 illustrates the process of converting a constrained prosthetic knee assembly from a bushing that allows full distraction to the bushing and capture element of FIG. 14 that provides limited distraction, according to one embodiment of the present application. [Figure 16] FIG. 16 is a perspective view of yet another embodiment of a capture element and bushing separated to allow limited separation according to an embodiment of the present application. [Figure 17] 17 is a cross-sectional view of the tibial baseplate and tibial bearing component of a seventh constrained knee prosthesis assembly having the hinge post of FIG. 13 and the hinge post and capture element embodiment of FIG. 16. [Figure 18] FIG. 18 is a perspective view of yet another embodiment of a capture element and bushing separated to allow limited separation according to an embodiment of the present application. [Figure 19] FIG. 19 illustrates a process for converting the components of a seventh constrained knee prosthesis from a bushing that allows full distraction to the bushing and capture element of FIG. 18 that provides limited distraction, according to one embodiment of the present application. [Figure 20] FIG. 20 shows a plan view of a hinge post that may be used with the constrained prosthetic knee assemblies discussed herein, including those of FIGS. 21A through 23. [Figure 21A] FIG. 21A illustrates a top view of another embodiment of a combined proximal capture element and bushing initially assembled together in accordance with an embodiment of the present application. [Figure 21B] FIG. 21B shows a perspective view of the capture element of FIG. 21A. [Figure 21C] FIG. 21C shows a cross-sectional view of the capture element of FIGS. 21A and 21B. [Figure 22] FIG. 22 illustrates a perspective view of the capture element and bushing of FIGS. 21A-21C now separated and spaced apart to allow limited distraction, according to one embodiment of the present application. [Figure 23] FIG. 23 shows a cross-sectional view of the tibial baseplate and tibial bearing component of an eighth constrained knee prosthesis assembly having the hinge post of FIG. 20 and the hinge post and capture element embodiment of FIG. 22 configured to limit distraction of the femoral component from the tibial baseplate and tibial bearing component. DETAILED DESCRIPTION OF THE INVENTION

[0034] This application relates to constrained tibial prosthesis assemblies and systems that include, among other components, a tibial baseplate, a capture element, a bushing, and a hinge post. This application focuses on limiting distraction of the femoral component relative to the tibial baseplate and / or tibial bearing component through various features, techniques, and components, including the capture element, discussed herein. Limiting distraction can prevent dislocation of the knee joint and the corresponding pain, discomfort, and possible need for medical intervention.

[0035] To better understand knee replacement procedures, it may be useful to understand the relationship between bones and the bone cuts that may be made to orient the various provisional and permanent prosthetic components within the knee joint. Figures 1 and 2 illustrate several features of the anatomy and orientation of the knee joint. In Figure 1, a frontal view of a lower leg 102, including a femur 104 and a tibia 106, is shown to illustrate various lower leg axes. The femur 104 has an anatomical axis 108 that generally coincides with its intramedullary canal. The femur 104 also has a functional, or loading, axis 110 that extends from the center of the femoral head 112 to the center of the knee joint 114. The angle 116 between these two axes varies within patient populations but is generally on the order of 5 to 7 degrees (inclusive). Like the femur 104, the tibia 106 also has an anatomical axis that generally coincides with its intramedullary canal. The functional axis 118 of the tibia 106 extends from the center of the knee joint 114 to the center of the ankle region 120 and generally coincides with its anatomical axis.

[0036] A joint line 122, about which the knee joint 114 flexes, is generally parallel to a line passing through the medial and lateral femoral condyles 124 and to the tibial plateau 126. Although the joint line 122 is shown in FIG. 1 as being perpendicular to the functional axis 110 of the femur 104 and the functional axis 118 of the tibia 106, the joint line 122 can extend at a varus or valgus angle. Typically, during a partial or total knee replacement procedure, portions of the distal end of the femur 104 or the proximal end of the tibia 106 are resected parallel or nearly parallel to the joint line 122, which in turn is perpendicular to the functional axes 110 and 118, as indicated at 128 and 130, respectively.

[0037] FIG. 2 provides a closer view of the knee joint 114 and its coordinate system. In this view, the medial / lateral axis 202 corresponds approximately to the joint line 122 (see FIG. 1), the proximal / distal axis 204 corresponds approximately to the functional axes 110 and 118 (see FIG. 1), and the anterior / posterior axis 206 is approximately perpendicular to the other two axes. Position along each of these axes can be indicated by arrows. These arrows can represent the medial / lateral 208, anterior / posterior 210, and proximal / distal 212 positions of the inserted prosthetic component. Rotation about each of these axes can also be indicated by arrows. Rotation about the proximal / distal axis 204 can anatomically correspond to external rotation of the femoral component, while rotation about the anterior / posterior axis 206 can correspond to the extension plane tilt of the component, and rotation about the medial / lateral axis 202 can correspond to the varus / valgus angle of the component. Depending on the location of the proximal tibial cut 130 (see FIG. 1) made, the varus / valgus angle 214, extension plane angle 216, external rotation 218, or joint extension gap can be affected. Similarly, the location of the distal femoral cut 128 (see FIG. 1) can affect the location of the joint line 122, the extension gap, varus / valgus angle 214, or extension plane angle 216.

[0038] The terms "proximal" and "distal" as used herein should be given their commonly understood anatomical interpretation. The term "proximal" generally means a direction toward the patient's torso, and the term "distal" means a direction opposite to proximal, i.e., a direction away from the patient's torso. Of course, when the terms "proximal" and "distal" are used, they should be interpreted as if the patient were standing with the knee extended. The intent is to distinguish the terms "proximal" and "distal" from the terms "anterior" and "posterior." The terms "anterior" and "posterior" as used herein should be given their commonly understood anatomical interpretation. Thus, "posterior" means the back side of the patient, e.g., the back side of the knee. Similarly, "anterior" means the front side of the patient, e.g., the front side of the knee. Thus, "posterior" means the opposite direction of "anterior." Similarly, the term "lateral" means the opposite direction of "medial." The term "medial / lateral direction" means either from the inside to the outside or from the outside to the inside. The term "proximal / distal" means proximal to distal or distal to proximal. The term "anterior / posterior" means anterior to posterior or posterior to anterior.

[0039] As used herein, the "outer edge" of a tibial baseplate refers to any outer edge when viewed from a top view, e.g., in a generally lateral anatomical plane. Alternatively, the outer edge of a tibial baseplate can be any outer edge when viewed from a bottom view, e.g., in a generally lateral plane, and when viewed from a distal surface configured to contact the resected proximal surface of the tibia.

[0040] 3 shows a prosthesis assembly 300 for a constrained knee. The prosthesis assembly 300 may include a tibial baseplate 302, a tibial bearing component 304 (sometimes called a meniscal component, poly, articular component, or bearing), a femoral component 306, and a hinge post 308.

[0041] The tibial bearing component 304 can be coupled to and positioned on top of the proximal surface 310 of the tibial baseplate 302. The tibial bearing component 304 can be formed from a polymeric material, such as ultra-high molecular weight polyethylene ("UHMWPE"). The tibial bearing component 304 can be configured to articulate with the femoral component 306 through flexion and extension of the knee joint, as is known to those skilled in the art. The prosthesis assembly 300 includes the femoral component 306 and the tibial baseplate 302 that are mechanically linked to one another. This is achieved by a hinge post 308 and other components further shown and discussed in FIG. 4 . The hinge post 308 is coupled to the femoral component 306 and is received within a recess 309 in the tibial bearing component 304 and a recess 322 in the tibial baseplate 302 (see FIG. 4 ).

[0042] 3A illustrates a knee joint distraction. Specifically, the femoral component 306 is moved generally proximally / distally away from the tibial bearing component 304 and the tibial baseplate 302 (as indicated by arrow A1). If insufficient soft tissue remains within the knee joint to hold the femoral component 306 on the tibial bearing component 304 in the manner shown in FIG. 3, dislocation of the knee joint may occur. The movement between the femoral component 306, the tibial bearing component 304, and the tibial baseplate 302 creates a predetermined distance (gap) between the articular surfaces of the femoral component 306 and the tibial bearing component 304. Because the hinge post 308 remains at least partially retained within the recesses of the tibial baseplate 302 and / or tibial bearing component 304 in the embodiment of FIG. 3A, distraction of the femoral component 306 from the tibial bearing component 304 and tibial baseplate 302 occurs generally along the proximal / distal axis 204 and along the direction 212 shown in FIG. 2. However, if the hinge post 308 were to disengage from the recesses 309 and 322 (see FIG. 4), dislocation of the knee joint could result. Dislocation can be painful and may also result in other complications for the patient.

[0043] FIG. 4 shows an exploded view of the prosthesis assembly 300, tibial baseplate 302, tibial bearing component 304, femoral component 306, and hinge post 308, further showing hinge axle 312, poly box 314, axle bushing 316, shackle 318, and bushing 320.

[0044] The hinge post 308 is coupled to the femoral component 306 via a shackle 318, an axle bushing 316, and a hinge axle 312. A distal portion of the shackle 318 is received within a recess 309 of the tibial bearing component 304, which is threadably or otherwise coupled to the hinge post 308. The hinge post 308 extends distally through the recess 309 of the tibial bearing component 304 and is received within a recess 322 of the tibial baseplate 302. The recess 322 of the tibial baseplate 302 that receives the hinge post 308 may be formed at least in part by a keel 324 of the tibial baseplate 302. The hinge post 308 may be movable (e.g., rotatable and / or distractible as shown in FIG. 3A ) relative to the tibial bearing component 304 and / or the tibial baseplate 302. The hinge post 308 may be rotatably coupled to the femoral component 306 via a hinge axis 312. Thus, with the femoral component 306 and the tibial baseplate 302 mechanically linked, a longitudinal axis LA defining the centerline of the hinge post 308 may define a rotation / articulation axis ARA for the knee joint.

[0045] During assembly, the shackle 318 can be positioned between opposing walls of the poly box 314. During assembly on the hinge axle 312, the axle bushing 316 also sits within an opening in the proximal portion of the shackle 318. The shackle 318 and hinge post 308 can be formed from any suitable material, such as a titanium alloy, a cobalt-chromium alloy, or the like, while the axle bushing 316 and poly box 314 can be formed from a different material, such as a plastic, for example, UHMWPE. The axle bushing 316 acts as a bearing between the shackle 318 and the hinge axle 312. The poly box 314 acts as a bearing between the femoral component 306 and the shackle 318.

[0046] The prosthesis assembly 300 of FIG. 4 illustrates a system 326 of components in which knee distraction is not limited by capture elements or other mechanisms of the prosthesis assembly 300. In this manner, the system 326 provides components configured for full distraction when assembled. Therefore, as previously described, the soft tissue of the knee is relied upon to limit distraction between the femoral component 306, the tibial baseplate 302, and the tibial bearing component 304. The bushing 320 can be configured for insertion into at least the recess 322 of the tibial baseplate 302. In some embodiments, the bushing 320 can also be inserted into or through the recess 309 (see FIG. 3 ) of the tibial bearing component 304. The bushing 320 can be configured to receive at least a portion of the hinge post 308. The bushing 320 can act as a bearing between the hinge post 308 and the tibial baseplate 302. The hinge post 308 may be movable in a generally proximal / distal direction relative to the bushing 320, such as during distraction depicted in FIG. 3A.

[0047] Whether complete joint release is desirable is determined based on the patient's anatomical characteristics. This determination process may include determining the condition, function, and quantity of soft tissue within the knee joint, including the number and condition of remaining ligaments. The determination process may also include physician-directed release of the knee joint, performing a predetermined range of motion of the knee joint, measuring gaps between the bones and / or soft tissue within the knee joint, such as measuring the extension gap discussed in connection with FIGS. 1 and 2, or the like. Some or all of these determinations may be performed before or after implantation of the femoral component, tibial bearing component, tibial baseplate, and / or other components.

[0048] If the physician determines, based on the patient's anatomical characteristics, that the knee joint is sufficient to maintain the femoral component mechanically linked to the tibial baseplate during full distraction (e.g., knee dislocation is unlikely), the physician can implement a first constrained prosthetic assembly configured to allow full distraction of the femoral component from the tibial bearing component and / or tibial baseplate. Alternatively, if the physician determines that the knee joint is insufficient to maintain the femoral component mechanically linked to the tibial baseplate during full distraction (e.g., knee dislocation is possible), the physician can implement a second constrained prosthetic assembly configured to allow limited distraction of the femoral component from the tibial bearing component and / or tibial baseplate.

[0049] According to one embodiment, a method of assembling a prosthesis assembly for a constrained knee is discussed and presented herein and may include coupling a hinge post to a femoral component, inserting a bushing into a recess in a tibial baseplate, positioning a capture element in the recess in the tibial baseplate, inserting the hinge post into the recess and through the capture element once coupled to the femoral component, coupling the hinge post with the bushing in the recess, and inserting a tibial bearing component between the femoral component and the tibial baseplate.

[0050] Optionally, in this method, positioning the capture element within the recess of the tibial baseplate may include biasing the capture element to engage one or more retention features of the tibial baseplate. Positioning the capture element within the recess of the tibial baseplate may include inserting the capture element into a receptacle adjacent to and communicating with the recess and moving the capture element laterally from the receptacle into the recess. Positioning the capture element within the recess of the tibial baseplate may include threading the capture element into the tibial baseplate. A hinge post may be coupled to the bushing within the recess to position the bushing in a desired position relative to the capture element. Engaging the capture element with at least one of the bushing or the hinge post may limit distraction of the femoral component from the tibial bearing component and the tibial baseplate.

[0051] It should be noted that the step of inserting the tibial bearing component between the femoral component and the tibial baseplate may be performed before or after the steps of coupling the hinge post to the femoral component, inserting the bushing into the recess of the tibial baseplate, positioning the capture element in the recess of the tibial baseplate, and / or inserting the hinge post into the recess and through the capture element once coupled to the femoral component, and coupling the hinge post with the bushing in the recess. Thus, the above-described method need not be limited to the order of the steps described.

[0052] 5 shows a cross-sectional view of a prosthesis assembly 400 having a similar structure to the previously described prosthesis assembly 300. However, the prosthesis assembly 400 differs in that it includes a capture element 401 that limits distraction of the femoral component 306 from the tibial bearing component 304 and the tibial baseplate 302. At least the tibial baseplate 302 can be configured to receive and / or couple with the capture element 401, as discussed further herein.

[0053] The cross-sectional view of FIG. 5 shows the distal surface 330 of the tibial baseplate 302, as well as the proximal surface 310 and outer edge 332. The outer edge 332 extends around the tibial baseplate 302 between the proximal surface 310 and the distal surface 330. A keel 324 extends distally from the distal surface 330 of the tibial baseplate 302. The keel 324 at least partially defines a recess 322 that receives the hinge post 408 and the bushing 420. The keel 324 can be integral (monolithic) with the remainder of the tibial baseplate 302 or can be attached thereto (e.g., via threads or another mechanical coupling mechanism). The keel 324 can be configured to extend distally and can be shaped to fit within the intramedullary canal of the tibia 106 (see FIG. 1 ) to provide fixation for the tibial baseplate 302.

[0054] The distal surface 330 can include features such as threaded openings for attachment of pegs, augments, or other components known to those skilled in the art. The distal surface 330 (and other features of the tibial baseplate, such as the keel 324) can be formed from porous or highly porous materials that promote bone ingrowth. Highly porous biomaterials are useful as bone substitutes and as cell and tissue receptive materials. The porosity of highly porous biomaterials can be as low as 30%, 55%, or as high as 70%, 80%, 85%, or 90%. The average pore size of highly porous materials can be, for example, 100 microns to 1000 microns. However, the use of highly porous biomaterials is not contemplated in all embodiments. For example, materials such as bone cement can be utilized as an alternative to highly porous biomaterials.

[0055] One example of such a porous or highly porous material is OsseoTi®, publicly available from Zimmer Biomet Inc. of Warsaw, Indiana. The material can include titanium or titanium alloys, and may also include other materials. Such materials (including relatively non-porous or non-porous biocompatible materials) can be manufactured using additive manufacturing processes, such as laser sintering or the like. OsseoTi® is highly biocompatible, highly corrosion-resistant, and contains a highly interconnected pore architecture that mimics the porous structure of human cancellous bone, which may enhance bone integration and ingrowth. The porous or highly porous material can be fabricated to be layered on or structured with / on a relatively non-porous or non-porous biocompatible material, such as titanium, titanium alloys, stainless steel, or other materials known to those skilled in the art.

[0056] Another example of such porous or highly porous materials is manufactured using Trabecular Metal Technology®, publicly available from Zimmer Biomet Inc. of Warsaw, Indiana. Such materials may be formed from a reticulated vitreous carbon foam substrate. This substrate is infiltrated and coated with a biocompatible metal, such as tantalum, by chemical vapor deposition (CVD) in the manner disclosed in detail in U.S. Pat. No. 5,282,861 to Kaplan, the entire disclosure of which is expressly incorporated herein by reference. In addition to tantalum, other metals may be used, such as niobium, or alloys of tantalum and niobium with each other or with other metals. Porous tantalum structures may be formed in various densities to selectively tailor the structure to specific applications. Specifically, as discussed in the above-incorporated U.S. Pat. No. 5,282,861, porous tantalum can be fabricated to virtually any desired porosity and pore size, thus matching the natural bone at the periphery to provide an improved matrix for bone ingrowth and mineralization.

[0057] Generally, the contemplated porous material structure can include multiple ligaments defining open spaces between them, with each ligament generally comprising a core covered by a thin metal film. The open spaces between the ligaments constitute a matrix of continuous channels with no dead ends, so that cancellous bone growth through the porous tantalum structure is not inhibited. Porous or highly porous materials may contain up to 70%, 85%, or more void space. Thus, porous or highly porous materials are lightweight, strong porous structures that are substantially uniform and consistent in composition, closely resembling the structure of natural cancellous bone, thereby providing a matrix into which cancellous bone can grow to enable fixation of the tibial baseplate to the patient's bone.

[0058] FIG. 5 illustrates that the prosthesis assembly 400 may include a modified hinge post 408 and bushing 420 compared to the hinge post 308 and bushing 320 of the embodiment of FIG. 4 . The bushing 420 may be configured to receive at least a portion of the hinge post 408 therein. The hinge post 408 may include engagement features 407, such as threads 409. These engagement features 407 may be configured to interlock with corresponding engagement features 411, such as threads 413, of the bushing 420. The hinge post 408 and bushing 420 may be coupled for movement together via the engagement features 407, 411. This configuration may differ from the configuration of the hinge post 308 and bushing 320 of the embodiment of FIG. 4 , which are not coupled for movement together. As such, the hinge post 308 and bushing 320 do not include engagement features such as threads. The hinge post 308 may be movable relative to the bushing 320.

[0059] 5 shows the hinge post 408 coupled at its proximal end to a shackle 318. This coupling can be via a threaded engagement 415 between the hinge post 408 and the shackle 318. The threaded engagement 415 allows the hinge post 408 and the shackle 318 to be reversibly coupled and separated from one another, allowing for changes in the configuration of the hinge post (e.g., from hinge post 308 to hinge post 408 to facilitate limited distraction, for example). The shackle 318 and hinge post 408 can extend into and be received by a recess 309 in the tibial bearing component 304. The hinge post 408 can have an engagement feature 407 (here, threads 409) located along a central or distal portion of the hinge post 408. The threads 409 and 413 may be rope threads, knuckle threads, ACME threads, or other types of threads known to those skilled in the art. In some embodiments, the threads 409 may differ slightly in pitch or another geometric aspect from the threads 413 to provide a slight interference. This slight interference may attract the bushing 420 to a desired position within the recess 322 relative to the capture element 401. Such a position for the bushing 420 relative to the capture element 401 may allow a desired, limited amount of distraction between the femoral component 306, the tibial bearing component 304, and the tibial baseplate 302 before engaging the bushing 420 with the capture element 401.While the embodiment of FIG. 5 contemplates that engagement of the bushing 420 with the capture element 401 will stop / halt limited distraction (movement) of the femoral component 306 relative to the tibial bearing component 304 and the tibial baseplate 302, other embodiments, such as FIG. 12 and the embodiment described in the U.S. Provisional Patent Application entitled "ANTI-LUXATION DEVICES FOR A CONSTRAINED PROSTHETIC KNEE," filed on the same date (the entire contents of which are incorporated herein by reference), contemplate that engagement features (e.g., barbs, tabs, ribs, or other types of protrusions) are part of the hinge post, and that engagement of these engagement features with the capture element 401 will stop / halt distraction of the femoral component 306 relative to the tibial bearing component 304 and the tibial baseplate 302. Thus, the capture element 401 is engaged by at least one of the bushing 420 and / or hinge post 408 to limit distraction of the femoral component 306 from the tibial bearing component 304 and tibial baseplate 302 .

[0060] 5, the capture element 401 can be at least partially positioned within a recess 322 of the tibial baseplate 302, e.g., located proximal to the bushing 420. The capture element 401 can have a through-hole (see, e.g., FIGS. 6 and 7) configured to receive at least a portion of the hinge post 408. Indeed, the capture element 401 with a through-hole can be configured to allow the hinge post 408 to extend distally through the capture element to engage and couple with the bushing 420, as shown in FIG. 5. The capture element 401 can include components that can stop / limit movement of the hinge post 408 when positioned at least partially within the recess 322 and coupled to the tibial baseplate 302.

[0061] 5 shows that the capture element 401 can be ring-shaped and can be received in a groove 417 of the tibial baseplate 302. The groove 417 and capture element 401 can be located distal to the proximal surface 310 of the tibial baseplate 302 such that the capture element 401 is located distal to the tibial bearing component 304. The groove 417 can communicate with and extend outward from the recess 322. At least a portion of the capture element 401 can extend into the recess 322 and interface with the hinge post 408. The portion of the capture element 401 positioned within the recess 322 can be engaged by the bushing 420 during limited distraction as described above.

[0062] FIG. 6 shows a top view of the tibial baseplate 302, thus showing the proximal surface 310 and outer edge 332. The proximal surface 310 and outer edge 332 may have a certain asymmetry relative to the medial / lateral centerline. This shape is designed to maximize tibial coverage for most knee replacement candidates. The asymmetric shape results in the medial compartment of the tibial baseplate being relatively wider than the lateral compartment of the tibial baseplate 302. Maximized cortical bone coverage facilitates superior support for the tibial baseplate 302. The large area of ​​contact between the cortical and cancellous bone of the tibia facilitates secure, permanent fixation of the tibial baseplate 302 to the tibia.

[0063] 6 shows capture element 401 in the process of assembly with tibial baseplate 302 (including by insertion into recess 322). Hinge post 408, shackle, femoral component, and bushing 420 are not shown in FIG. 6 for clarity. The assembly process involves inserting capture element 401 into receptacle 419 adjacent to and in communication with recess 322 and groove 417 (see FIG. 5). This process involves moving capture element 401 generally in a medial or lateral direction (as indicated by arrow A2) from receptacle 419 into recess 322 (e.g., to the position of FIG. 5, fully into groove 417).

[0064] 6 further shows through-hole 421 in capture element 401. Through-hole 421 is formed to allow at least a portion of hinge post 408 (see FIG. 5) to pass through the through-hole into the remainder of recess 322 and into bushing 420 (see FIG. 5).

[0065] 7 illustrates various embodiments of capture elements 501A, 501B, 501C, 501D, and 501E, each formed as a snap-fit ​​component 502. Capture elements 501A, 501B, 501C, 501D, and 501E can be utilized in various embodiments of the present application in the form of capture element 401 described above for limiting distraction. Capture elements 501A, 501B, 501C, 501D, and 501E include a generally cylindrical main body portion 504 (see only with respect to capture element 501A). Some of capture elements 501A, 501B, 501C, 501D, and 501E, such as capture elements 501C and 501D, can include an outer opening 505 affixed to and in communication with through-hole 421. In addition to the main body portion 504, most of the capture elements 501A, 501B, 501C, 501D, and 501E can include legs 506 (referenced only with respect to capture element 501A) or other deflectable features configured to engage with mating features (grooves, protrusions, etc.) on a tibial baseplate (not shown). The legs 506 can include protrusions 508 and / or grooves or other features to facilitate a snap-fit ​​connection with the tibial baseplate shown in FIGS. 5 and 8.

[0066] FIG. 8 shows a cross-sectional view of a prosthesis assembly 400A including a tibial baseplate 302, a portion of a tibial bearing component 304, a hinge post 408, and a bushing 420. The hinge post 408 is not yet fully seated within the bushing 420 and is not yet fully threadedly coupled with the shackle 318, as was the case in the embodiment of FIG. 5. FIG. 8 shows a capture element 601 formed as a snap-fit ​​component 602 similar to that previously described in FIG. 7. The capture element 601 is at least partially positioned within a recess 322, with feet or prongs 603 and other features biased to engage one or more retention features 604 of the tibial baseplate 302. These one or more retention features 604 include protrusions 605 and grooves 607 positioned along the edges of the recess 322. The capture element 601 is configured to engage the tibial baseplate 302 to form a snap-fit ​​connection with the tibial baseplate 302 , thereby retaining the capture element 601 to the tibial baseplate 302 .

[0067] It should be noted that with reference to FIG. 8 , as the hinge post 408 is threaded onto the shackle 318, threads between the bushing 420 and a central portion of the hinge post 408 may engage. These threads may be configured in the form of threads described above with reference to FIG. 5 . Engaging the threads may reposition the bushing 420 within the recess 322 as desired. For example, the bushing 420 may be moved proximally, as indicated by arrow P, to define a desired gap G between the bushing 420 and the capture element 601. The size of the gap G may determine the amount of distraction of the femoral component (not shown) from the tibial bearing component 304 and tibial baseplate 302. As the bushing 420 moves proximally with the hinge post, contact between the bushing 420 (or hinge post 408) and the capture element 601 may limit (stop) distraction.

[0068] FIG. 9A is a cross-sectional view illustrating another embodiment of a capture element 701 for use with prosthesis assembly 700. Capture element 701 can include threads 703. Threads 703 are configured to interlock with corresponding threads 705 along recess 722 in tibial baseplate 702. When capture element 701 is threaded into the position shown in FIG. 9A, it is at least partially captured within recess 722. FIG. 9A additionally illustrates a further embodiment of hinge post 708 and bushing 720. Hinge post 708 can have a structure similar to that of hinge post 408, but can have threads 707 along its distal portion 709 rather than a central portion as in the embodiment of FIG. 5. Bushing 720 and hinge post 708 can be coupled to one another by engaging threads in a manner similar to FIG. 5.

[0069] 9B shows a capture element 701 with external threads 703 along its outer diameter along with a through hole 721 similar to those previously described. The through hole 721 may include a drive feature 723, such as a groove, lobe, or the like, for engagement with a driver or other tool used to thread the capture element 701 onto the tibial baseplate 702, thereby capturing the distal feature of the bushing 720 and / or hinge post 708.

[0070] 8, FIG. 9A illustrates a gap G between the bushing 720 and the capture element 701. The size of the gap G can dictate the amount of distraction of the femoral component (not shown) from the tibial bearing component 304 and tibial baseplate 702. As the bushing 720 moves proximally with the hinge post 708, contact between the bushing 720 (or hinge post 708) and the capture element 701 can limit (stop) distraction. The position of the bushing 720 within the recess 722 can be adjusted as described above (e.g., via small differences in thread pitch or other geometry) by the threaded engagement between the bushing 720 and the hinge post 708.

[0071] FIG. 10 shows a cross-sectional view of a prosthesis assembly 800 including the tibial baseplate 702, a portion of the tibial bearing component 304, and a capture element 701, previously shown in FIG. 9A . However, the embodiment of FIG. 10 includes a hinge post 808 and a bushing 820 having a modified shape from those of FIG. 9A . Accordingly, FIG. 10 further illustrates a further embodiment of the hinge post 808 and bushing 820. The hinge post 808 can have a structure similar to that of the hinge post 408, but can have threads 807 along its distal portion 809 of a smaller diameter rather than the central portion as in the embodiments of FIGS. 5 and 8 . The bushing 820 can have a counterbore or configuration that provides a reduced volume at the distal portion compared to the proximal portion. Thus, the distal recess 822A can have a smaller diameter compared to the more proximal recess 822B of the recess 822. The hinge posts 808 can be coupled together by engaging threads 811 of bushings 820 in a manner similar to that shown in FIG.

[0072] 10 , the bushing 820 can be configured to completely limit distraction of the femoral component (not shown) from the tibial bearing component 304 and tibial baseplate 702. Therefore, distraction of the femoral component is almost impossible. This is a result of the bushing 820 being formed long relative to the length of the recess 822 so that the bushing 820 can abut the capture element 701 as shown. Therefore, there is no gap G (see FIGS. 8 and 9A ) between the bushing 820 and the capture element 701. Contact between the bushing 820 (or hinge post 808) and the capture element 701 limits (stops) distraction.

[0073] FIG. 11 shows a cross-sectional view of a prosthesis assembly 900 including the tibial baseplate 702, a portion of the tibial bearing component 304, the hinge post 808, and the capture element 701 previously shown in FIGS. 9A and 10 . However, the embodiment of FIG. 11 includes a bushing 920 having a modified shape from that of FIG. 10 . Specifically, the longitudinal length of the bushing 920 is shortened relative to the longitudinal length of the recess 822 to provide a gap G between the bushing 920 and the capture element 701. The size of the gap G determines the amount of distraction of the femoral component (not shown) from the tibial bearing component 304 and the tibial baseplate 702. As the bushing 920 moves proximally with the hinge post 708, contact between the bushing 920 (or hinge post 708) and the capture element 701 can limit (stop) distraction. The position of bushing 920 within recess 822 can be adjusted as described above by the threaded engagement between bushing 820 and hinge post 708 (e.g., via small differences in thread pitch or other geometry).

[0074] 11A shows a perspective view of capture element 701 and a proximal portion of bushing 920. Capture element 701 can have external threads 703 along its outer diameter along with a throughbore 721. Throughbore 721 can include the drive mechanism 723 described above. Recess 822 in bushing 920 is shown along with the counterbore configuration described above in FIG.

[0075] 11B shows the relative spacing of capture element 701 from bushing 920 (prior to limited distraction). Bushing 920 may include an anti-rotation feature 824 along its outer diameter 826. Anti-rotation feature 824 is shown, for example, as lobe 828. Anti-rotation feature 824 provides a stop against rotational movement of bushing 920. However, other types of anti-rotation features are contemplated, such as threads, projections, tabs, prongs, barbs, ribs, etc. Anti-rotation feature 824 may be used with any of the bushing designs shown and discussed herein (including bushing 320 of FIG. 4) and is therefore not limited to bushing 920.

[0076] FIG. 12 shows a cross-sectional view of a prosthesis assembly 1000 including the tibial baseplate 702, a portion of the tibial bearing component 304, a bushing 820, and a capture element 701, previously shown in FIGS. 9A and 10 . However, the embodiment of FIG. 12 includes a hinge post 1008 having a modified shape from that of FIG. 10 . Specifically, the hinge post 1008 can include one or more engagement features 1001 that can be configured to engage the capture element 701 after limited distraction by the femoral component (not shown). The one or more engagement features 1001 can be tabs, ribs, or other types of protrusions. The one or more engagement features 1001 can be threaded through the through-holes 721 ( FIG. 11A ), for example, by passing them along one or more of the drive mechanisms 723, and then clocked (rotated) to different positions shown in FIG. 12 . A gap G can exist between the one or more engagement features 1001 and the distal end of the capture element 701. The size of the gap G can dictate the amount of distraction of the femoral component (not shown) from the tibial bearing component 304 and tibial baseplate 702. Contact between the one or more engagement features 1001 (portions of the hinge post 1008) and the capture element 701 can limit (stop) distraction. In this manner, the configuration of the hinge post 1008 itself, rather than contact between the bushing 820 and the capture element 701, can limit distraction.

[0077] 13 shows a perspective view of a hinge post 1108 according to another embodiment. The hinge post 1108 can include a rear thread 1109P and a distal thread 1109D. The hinge post 1108 can additionally include a drive mechanism 1102 at a proximal end and an unthreaded middle section 1104. The threads 1109P and / or 1109D can be rope threads, round threads, ACME threads, or other types of threads known to those skilled in the art. The middle section 1104 can be positioned between the rear thread 1109P and the distal thread 1109D. The middle section 1104 and / or other sections can be slightly tapered, for example.

[0078] FIG. 14 shows a perspective view of the capture element 1201 and bushing 1220 in their relative spacing prior to limited distraction of the knee joint. The bushing 1220 includes threads 1211 configured to engage, for example, threads 1109D ( FIG. 13 ) of the hinge post 1108. The bushing 1220 further includes two anti-rotation features 1224A and 1224B. The capture element 1201 can include external threads 1203, a through bore 1221, a drive mechanism 1223, and two anti-rotation features 1225A and 1225B. The capture element 1201 can have external threads 1203 along its outer diameter along with the through bore 1221. The through bore 1221 can include the drive mechanism 1223 as described above.

[0079] The two anti-rotation features 1224A and 1224B can be configured to engage with two corresponding anti-rotation features 1225A and 1225B. Such engagement can occur during distraction and / or rotation of the femoral component, hinge post 1108 (see FIG. 13 ), and bushing 1220. The anti-rotation features 1224A and 1224B can be proximally extending prongs or other features that can be inserted into appropriately shaped recesses 1202A and 1202B during limited distraction of the hinge post 1108 (see FIG. 13 ) and bushing 1220. This limited distraction can bring the bushing 1220 closer to the capture element 1201 than the spacing shown in FIG. 14 . Suitably shaped recesses 1202A and 1202B can be configured between the two anti-rotation features 1225A and 1225B. Similarly, the two anti-rotation features 1225A and 1225B can be inserted into suitably shaped recesses 1204A and 1204B in the bushing 1220 during limited distraction of the hinge post 1108 (see FIG. 13 ) and bushing 1220. The recesses 1202A and 1202B can be shaped and sized relative to the anti-rotation features 1224A and 1224B, and the recesses 1204A and 1204B can be shaped and sized relative to the anti-rotation features 1225A and 1225B, to allow a desired limited rotation (e.g., 30 degrees or less) of the hinge post 1108 (see FIG. 13 ), bushing 1220, and femoral component (not shown). Such rotation may be stopped by engagement between two or more of the anti-rotation features 1224A, 1224B, 1225A and / or 1225B.

[0080] The spacing between the capture element 1201 and the bushing 1220 can include the aforementioned gap G. The size of the gap G dictates the amount of proximal distraction of the femoral component (not shown) from the tibial bearing component and tibial baseplate. Additionally, rotational gaps can be provided between the anti-rotation features 1224A, 1224B, 1225A, and 1225B to limit rotation of the femoral component. Proximal and / or rotational movement of the bushing 1220 with the hinge post 1108 ( FIG. 13 ) can limit (stop) distraction by contact between the bushing 1220 and the capture element 1201.

[0081] 15 illustrates a process for converting a constrained knee prosthesis from a bushing 1320 (shown on the viewer's left) that allows full distraction to a bushing 1220 and capture element 1201 (shown on the viewer's right) that provides limited distraction according to an embodiment of the present application. The method 1300 may include removing the hinge post 1108 from the bushing 1320 from the tibial baseplate 702 in step 1302. The method 1300 removes the bushing 1320 configured for full distraction of the knee joint from the tibial baseplate 702 in step 1304. The bushing 1220 and capture element 1201 are inserted into the tibial baseplate 702 in step 1306. Then, in step 1308, the hinge post 1108 is connected to the shackle 318 and reinserted back into the tibial baseplate 702 connecting with the bushing 1220 and capture element 1201 to provide the limited distraction of the knee joint discussed herein.

[0082] 16 shows a perspective view of the capture element 1401 and bushing 1420 in their relative spacing prior to limited distraction of the knee joint. The bushing 1420 includes threads 1411 formed to engage, for example, the threads 1109D (FIG. 13) of the hinge post 1108. The bushing 1420 may be configured in the form of the bushing 1220 described above in FIGS. 14 and 15. The bushing 1420 may differ in that a single anti-rotation feature 1424 is utilized. The capture element 1401 may include a single anti-rotation feature 1425.

[0083] The anti-rotation feature 1424 can be configured to engage a corresponding anti-rotation feature 1425. The anti-rotation feature 1424 can be a proximally extending prong or other feature that can be inserted into a suitably shaped recess 1402 in the capture element 1401 during limited distraction of the hinge post 1108 (see FIG. 13 ) and the bushing 1420. This limited distraction can bring the bushing 1420 closer to the capture element 1401 than the spacing shown in FIG. 16 . The suitably shaped recess 1402 can oppose the anti-rotation feature 1424 and can be defined in part by an opposing edge of the anti-rotation feature 1425. Similarly, the anti-rotation feature 1425 can be inserted into a suitably shaped recess 1404 in the bushing 1420 during limited distraction of the hinge post 1108 (see FIG. 13 ) and the bushing 1420. Recess 1402 can be shaped and sized relative to anti-rotation feature 1424, and recess 1404 can be shaped and sized relative to anti-rotation feature 1425, to allow a desired limited rotation (e.g., 30 degrees or less) of hinge post 1108 (see FIG. 13), bushing 1220, and femoral component (not shown). Engagement of anti-rotation feature 1424 with anti-rotation feature 1425 can stop rotation and thus provide limited distraction of the knee joint.

[0084] 17 illustrates that the spacing between the capture element 1401 and the bushing 1420 can include the aforementioned gap G. The size of the gap G dictates the amount of proximal distraction of the femoral component (not shown) from the tibial bearing component and tibial baseplate. Additionally, a rotational gap (see FIG. 16 ) can be provided between the anti-rotation features 1424 and 1425 to limit rotation of the femoral component. As the bushing 1420 moves proximally and / or rotates with the hinge post 1108, contact between the bushing 1420 and the capture element 1401 can limit (stop) distraction.

[0085] Figure 18 shows the capture element 1501 and bushing 1520 in their relative spacing prior to limited distraction of the knee joint. The bushing 1520 and capture element 1501 are configured in a manner very similar to the embodiment of Figure 16. The size of the anti-rotation feature 1524 has been modified to be smaller than the embodiment of Figure 16, while the anti-rotation feature 1525 has been enlarged. The anti-rotation features 1524 and 1525 can be sized appropriately to provide the desired control of knee joint distraction and / or rotation.

[0086] 19 illustrates a process for converting a constrained knee prosthesis from a bushing 1320 (shown on the viewer's left) that allows full distraction to a bushing 1520 and capture element 1501 (shown on the viewer's right) that provides limited distraction according to an embodiment of the present application. The method 1600 may include removing the hinge post 1108 from the bushing 1520 and from the tibial baseplate 702 in step 1602. The method 1600 removes the bushing 1520 configured for full distraction of the knee joint from the tibial baseplate 702 in step 1604. The bushing 1520 and capture element 1501 are inserted into the tibial baseplate 702 in step 1606. Then, in step 1608, the hinge post 1108 is connected to the shackle 318 and reinserted back into the tibial baseplate 702 connecting with the bushing 1520 and capture element 1501, thereby providing the limited distraction of the knee joint discussed herein.

[0087] FIG. 20 shows a perspective view of a hinge post 1708 according to another embodiment. The hinge post 1708 can include a rear thread 1709P and a distal thread 1709D. The hinge post 1708 can additionally include an unthreaded middle section 1704 having a first diameter portion 1704A and a smaller second diameter portion 1704B. The threads 1709P and / or 1709D can be rope threads, round threads, ACME threads, or other types of threads known to those skilled in the art. The middle section 1704 can be positioned between the rear threads 1709P and the distal threads 1709D. The middle section 1704 and / or other sections can be slightly tapered, for example. The distal end 1701 of the hinge post 1708 may not have threads and may be configured to pass through a capture element (see subsequent figures) and space the capture element from the distal end of the recess in the tibial baseplate as shown in FIG. 22.

[0088] 21A-21C show another embodiment of capture element 1801, which combines both a proximal capture element 1801P and a distal element 1801D, which may act as bushing 1820. Capture element 1801 initially exists as a single component that includes scoring, gaps, or other features to separate (space) proximal capture element 1801P from distal element 1801D, but may also have an intermediate linking element 1825 that connects proximal capture element 1801P with distal element 1801D. FIGS. 21A-21C show capture element 1801 prior to threaded engagement, first with a hinge post (e.g., hinge post 1708) and then with a tibial baseplate. In FIGS. 21A and 21B, capture element 1801 is a single component with a frangible or severable connection provided by intermediate connection element 1825 between proximal capture element 1801P and distal element 1801D.

[0089] As shown in the cross-sectional view of Figure 21C, distal element 1801D, bushing 1820, has internal threads 1811 formed to engage with, for example, threads 1709D (see Figure 20) of hinge post 1708. Proximal capture element 1801P has external threads 1803, throughbore 1821 (shared with distal capture element 1801D), and drive mechanism 1823. Throughbore 1821 can include drive mechanism 1823 formed in the manner described above.

[0090] FIG. 22 shows the capture element 1801 with the proximal capture element 1801P separated from the distal element 1801D. This separation process occurs when the capture element 1801 is partially seated into the recess of the tibial baseplate and then engaged by threading the hinge post 1708 into the distal element 1801D (e.g., distal threads 1709D (FIG. 20) engage with internal threads 1811 (see FIG. 21C)). This threaded engagement acts to separate the proximal capture element 1801P from the distal element 1801D (disengaging / breaking / severing the intermediate connection element 1825 in FIGS. 21A and 21B). The distal element 1801D, threaded onto the hinge post 1708, is then carried distally further into the recess of the tibial baseplate, where it acts as a bushing 1820 similar to that previously described herein. The proximal capture element 1801P and bushing 1820 can terminate with the relative spacing shown in FIG. 22 to allow for some limited distraction of the knee joint.

[0091] Such limited distraction may allow the bushing 1820 to be relatively closer to the proximal capture element 1801P than the spacing shown in Figure 22. The recess 1802 may be shaped and sized to allow the desired limited distraction of the hinge post 1708 (see Figure 20), the bushing 1820, and the femoral component (not shown).

[0092] 23 shows that the spacing between the proximal capture element 1801P and the bushing 1820 can include the aforementioned gap G. The size of the gap G determines the amount of proximal distraction of the femoral component (not shown) from the tibial bearing component and tibial baseplate. As the bushing 1820 moves proximally with the hinge post 1108, contact between the bushing 1820 and the proximal capture element 1801P can limit (stop) distraction.

[0093] Additional notes The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as "embodiments." Such embodiments may include elements in addition to those shown or described. However, the inventors also contemplate embodiments in which only the elements shown or described are provided. Furthermore, the inventors also contemplate embodiments using combinations or permutations of the illustrated and described elements (or one or more aspects thereof) with respect to the specific embodiment (or one or more aspects thereof) shown or described, or with respect to other embodiments (or one or more aspects thereof).

[0094] In this document, the terms "generally," "substantially," and "about" mean within 15 percent (±) of the provided value. The terms "a" or "an," as common in patent documents, are used to include one or more than one, independent of any other instance or use of "at least one" or "one or more." In this document, the term "or" means a non-exclusive or, whereby "A or B" is used to include "A but not B," "B but not A," and "A and B," unless otherwise specified. In this document, the terms "including" and "in which" are used as plain English equivalents of the terms "comprising" and "wherein," respectively. Also, in the claims that follow, the terms "including" and "comprising" are open-ended, i.e., systems, devices, articles, compositions, formulations, or processes that include elements in addition to those recited after such terms in a claim are still considered to be within the scope of that claim. Furthermore, in the claims that follow, the terms "first," "second," "third," etc. are used merely as labels and do not impose numerical requirements on their objects.

[0095] The above description is intended to be illustrative, not limiting. For example, the above embodiments (or one or more aspects thereof) can be used in combination with each other. Other embodiments can be used, for example, by one of ordinary skill in the art, upon review of the above description. The Abstract is provided to comply with U.S.C. § 1.72(b) to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Furthermore, the grouping of various features in the above Detailed Description serves to simplify the disclosure. This should not be construed as intending that a non-claimed feature is essential to any claim. Rather, inventive subject matter lies in less than all features of a particular disclosed embodiment. Accordingly, the following claims are herein incorporated into the Detailed Description as examples or embodiments. Each claim stands on its own as a separate embodiment, and such embodiments can be combined with each other in various combinations or permutations. The scope of the present invention should be determined by reference to the appended claims, along with the full range of equivalents to which such claims are entitled. According to aspect (1), there is provided a prosthesis assembly for a constrained knee, comprising: a femoral component; a tibial bearing component engaged by the femoral component; a tibial baseplate having a distal surface, a proximal surface opposite the distal surface and facing the tibial bearing component, an outer edge extending between the proximal and distal surfaces, and a keel extending distally from the distal surface; a bushing received within a recess in the tibial baseplate; a hinge post coupled to the femoral component and the bushing, the hinge post being at least partially received by the bushing; a capture element coupled to the tibial baseplate, the capture element engaged by at least one of the bushing or the hinge post to limit distraction of the femoral component from the tibial bearing component and the tibial baseplate; A prosthesis assembly for a constrained knee, comprising: According to aspect (2), the capture element includes one of a snap-fit ​​component or a threaded nut configured to be at least partially received within the recess of the tibial base plate, and the capture element has a through hole configured to allow at least a portion of the hinge post to pass through the capture element. According to aspect (3), the capture element is spaced proximally from the bushing by a predetermined distance, the distance allowing a limited degree of distraction of the femoral component from the tibial bearing component and tibial base plate. According to aspect (4), the capture element is proximal to the bushing and adjacent to the proximal end of the bushing, thereby completely limiting separation of the femoral component from the tibial bearing component and tibial base plate. According to aspect (5), the hinge post is connected to the bushing by a first thread, and the first thread connects with a second thread of the bushing. According to aspect (6), the coupling of the first thread and the second thread positions the bushing in a desired position relative to the capture element. According to aspect (7), the capture element is initially connected to the bushing by a frangible bond, and the frangible bond is released by threading the hinge post and the bushing to separate the capture element from the bushing. According to aspect (8), there is provided a prosthesis system for a constrained knee, comprising: a femoral component; a tibial bearing component configured to articulate with the femoral component; a tibial baseplate having a distal surface, a proximal surface opposite the distal surface and facing the tibial bearing component, an outer edge extending between the proximal and distal surfaces, and a keel extending distally from the distal surface; a bushing configured to be inserted into a recess in the tibial baseplate; a hinge post configured to couple with the femoral component and configured to couple with the bushing; a capture element configured to couple with the tibial baseplate, the capture element having a throughbore configured to allow at least a portion of the hinge post to pass through the capture element, the capture element configured to be engaged by at least one of the bushing or the hinge post when coupled to the tibial baseplate to limit distraction of the femoral component from the tibial bearing component and the tibial baseplate; A prosthetic system for a constrained knee, comprising: According to aspect (9), the hinge post is configured to be coupled to the bushing by a first thread, and the first thread engages with a second thread of the bushing. According to aspect (10), when the first thread is coupled with the second thread, the bushing is positioned at a desired position relative to the capture element. According to aspect (11), the capture element is configured to be adjacent to the bushing or spaced a predetermined distance from the bushing when the bushing is positioned at the desired position. According to aspect (12), the capture element includes one of a snap-fit ​​component or a threaded nut configured to be at least partially received within the recess of the tibial baseplate. According to aspect (13), the capture element, when assembled to the bushing, is spaced a predetermined distance proximally from the bushing, the distance allowing a limited degree of distraction of the femoral component from the tibial bearing component and the tibial base plate. According to aspect (14), when assembled to the bushing, the capture element is located proximally relative to the bushing and adjacent to the proximal end of the bushing, thereby completely limiting separation of the femoral component from the tibial bearing component and tibial base plate. According to aspect (15), the capture element is initially connected to the bushing by a frangible bond, and the frangible bond is released by threading the hinge post and the bushing to separate the capture element from the bushing. According to aspect (16), there is provided a method of assembling a prosthesis assembly for a constrained knee, the method comprising: The hinge post is connected to the femoral component, Inserting a bushing into the recess of the tibial baseplate; Positioning a capture element within the recess of the tibial baseplate; When coupled to the femoral component, inserting the hinge post into the recess through the capture element; connecting the hinge post with the bushing in the recess; inserting a tibial bearing component between the femoral component and the tibial baseplate; A method of assembling a prosthesis assembly for a constrained knee, comprising: According to aspect (17), positioning the capture element within the recess of the tibial base plate includes one of biasing the capture element to engage one or more retention features of the tibial base plate or threading the capture element into the tibial base plate. According to aspect (18), positioning the capture element within the recess of the tibial base plate includes inserting the capture element into a receptacle adjacent to and communicating with the recess, and moving the capture element outward from the receptacle into the recess. According to aspect (19), connecting the hinge post and the bushing in the recess further includes engaging the capture element with at least one of the bushing or the hinge post to position the bushing in a desired position relative to the capture element and limit distraction of the femoral component from the tibial bearing component and tibial base plate. According to aspect (20), the connection between the hinge post and the bushing in the recess disengages the connection between the capture element and the bushing.

Claims

1. 1. A prosthesis assembly for a constrained knee, comprising: a femoral component; a tibial bearing component engaged by the femoral component; a tibial baseplate having a distal surface, a proximal surface opposite the distal surface and facing the tibial bearing component, an outer edge extending between the proximal and distal surfaces, and a keel extending distally from the distal surface; a bushing received within a recess in the tibial baseplate; a hinge post coupled to the femoral component and the bushing, the hinge post being at least partially received by the bushing; a capture element coupled to the tibial baseplate; Including, 1. A prosthesis assembly for a constrained knee, wherein the capture element is spaced proximally from the bushing by a predetermined distance, the hinge post is connected to the bushing by a first thread, the first thread interlocking with a second thread on the bushing, the distance allowing a limited degree of distraction of the femoral component from the tibial bearing component and the tibial baseplate, and the connection between the first thread and the second thread positions the bushing in a desired position relative to the capture element and allows a limited degree of distraction.

2. 2. The prosthesis assembly of claim 1, wherein the capture element includes one of a snap-fit ​​component or a threaded nut configured to be at least partially received within the recess of the tibial baseplate, the capture element having a throughbore configured to allow at least a portion of the hinge post to pass through the capture element.

3. 2. The prosthesis assembly of claim 1, wherein the capture element is proximal to the bushing and abuts the proximal end of the bushing, thereby completely limiting distraction of the femoral component from the tibial bearing component and the tibial baseplate.

4. 2. The prosthesis assembly of claim 1, wherein the capture element is initially coupled to the bushing by a frangible bond, the frangible bond being configured to be released by threading the hinge post and the bushing to separate the capture element from the bushing.

5. 1. A prosthesis system for a constrained knee, comprising: a femoral component; a tibial bearing component configured to articulate with the femoral component; a tibial baseplate having a distal surface, a proximal surface opposite the distal surface and facing the tibial bearing component, an outer edge extending between the proximal and distal surfaces, and a keel extending distally from the distal surface; a bushing configured to be inserted into a recess in the tibial baseplate; a hinge post configured to couple with the femoral component and configured to couple with the bushing; a capture element configured to couple with the tibial baseplate, the capture element having a throughbore configured to allow at least a portion of the hinge post to pass through the capture element, the capture element configured to be engaged by at least one of the bushing or the hinge post when coupled to the tibial baseplate to limit distraction of the femoral component from the tibial bearing component and the tibial baseplate; Including, A prosthetic system for a constrained knee, wherein the capture element, when assembled to the bushing, is spaced proximally from the bushing by a predetermined distance, the distance allowing a limited degree of distraction of the femoral component from the tibial bearing component and the tibial baseplate.

6. The prosthesis system of claim 5 , wherein the hinge post is configured to be coupled to the bushing by a first thread, the first thread engaging a second thread of the bushing.

7. The prosthesis system of claim 6 , wherein when the first threads are coupled with the second threads, the bushing is positioned in a desired position relative to the capture element.

8. The prosthesis system of claim 7 , wherein the capture element is configured to be adjacent to or spaced a predetermined distance from the bushing when the bushing is positioned in the desired position.

9. The prosthetic system of claim 5 , wherein the capture element comprises one of a snap-fit ​​component or a threaded nut configured to be at least partially received within the recess of the tibial baseplate.

10. 6. The prosthetic system of claim 5, wherein the capture element, when assembled to the bushing, is located proximally relative to the bushing and abuts the proximal end of the bushing, thereby completely limiting distraction of the femoral component from the tibial bearing component and the tibial baseplate.

11. 6. The prosthesis system of claim 5, wherein the capture element is initially coupled to the bushing by a frangible bond, and the frangible bond is released by threading the hinge post and the bushing to separate the capture element from the bushing.

Images