The present disclosure relates generally to the field of knee implants, and more particularly to tibial components for endoprosthetic knee implants adapted for kinematic alignment, anatomic alignment, and methods of implantation thereof.
Knee arthroplasties are procedures in which an orthopedic surgeon replaces portions of severely diseased knee joints with an artificial endoprosthetic implant that is intended to restore joint function and alleviate pain. The procedure itself generally consists of the surgeon making a vertical midline anterior incision on the bent knee (i.e., a knee in flexion). The surgeon then continues to incise tissue to access the joint capsule. Once pierced, the patella is retracted and the distal condyles of the femur, the cartilaginous meniscus, and the proximal tibial plateau are exposed.
The surgeon then removes the cartilaginous meniscus and may use instrumentation to measure and resect the distal femur and the proximal tibia to accommodate the endoprosthetic knee implant. The endoprosthetic knee implant generally comprises three primary components: a femoral component, a tibial component, and a meniscal insert component that is disposed between the installed femoral and tibial components.
The resections themselves often remove areas of diseased bone. These resections also necessarily modify the profiles of the remaining distal femur and proximal tibia to better accommodate complementary shapes of the associated implant component. That is, the resected distal femur will eventually fit into a complementary femoral component. Likewise, the resected proximal tibia will eventually support a complementary tibial component.
The tibial component of the endoprosthetic implant typically includes a unitary keel descending downwardly and perpendicularly from a lower surface of a tibial base plate. When installed on the resected proximal tibia, the keel extends into a bore in the intramedullary canal of the tibia. The keel of an installed tibial component can be thought of as being disposed in a coronal plane and is oriented perpendicularly to the lower surface of the tibial base plate.
In the field of knee arthroplasties, there are several schools of thought concerning the angles at which resection of the distal femoral condyles and the proximal tibia should be made. The angles of resection largely determine how the implant components will sit in the joint and can influence how the artificial joint performs over time.
One school of thought is the anatomic alignment method. In the anatomic alignment method, the surgeon resects the tibia at 3 degrees of varus because this is believed to be the average angle of the native joint line. Femoral resections and ligament releases are then performed to keep a straight hip-knee-ankle axis of the limb.
Another school of thought is the mechanical alignment method. The priority in mechanical alignment is to resect the tibia perpendicular to the length or axis of the tibial shaft (i.e., parallel to the transverse body plane). A mechanically resected tibial plateau would have a 0 degree varus tilt. The distal femur is then adjusted to account for the 0 degree varus tilt of the resected tibia and any necessary ligament releases are performed to maintain a straight hip-knee-ankle axis.
By contrast, with the kinematic alignment method, the surgeon seeks to restore the patient's specific natural pre-diseased joint line based on data made available to the surgeon both pre-operatively and intra-operatively. Most kinematic alignment techniques start with referencing the distal femur and generally adjusting the slope of the tibial resections to be parallel to the distal femoral resection when the knee is in extension, and parallel to the posterior resections of the femoral condyles when the knee is in flexion.
The utility of traditional tibial components can be severely limited when the proximal tibia is resected at an angle. On average, a unitary tibial component may have a keel having a length in the range of about 35 millimeters (“mm”) to about 65 mm. When the tibial base plate is disposed at an angle on the resected tibia, the keel is likewise disposed at an angle relative to the longitudinal axis of the operative tibia. If the angle of the tibial resection is too great, or if the keel is too long, the keel will abut the medial or lateral inner cortical wall of the tibia. In extreme cases, repeated pressure of the keel on the inner cortical wall could weaken or penetrate the cortex (i.e., the compact, generally non-spongy outer wall of the bone).
Shortening the keel excessively is usually not possible. A shortened keel risks ineffective force transfer from the knee into the tibia during normal use. This thereby increases the risk that the tibial component may become unseated during normal activity.
The problem of having the keel abut the inner cortical wall is particularly pronounced in revision or trauma cases. In such cases, the surgeon typically resects more of the proximal tibia to expose heathy bone. For context, in revision cases, the prior-installed implant is usually cemented to the tibia. The surgeon removes the prior-installed implant by resecting the underlying bone. As a result, there is often less healthy bone available for the surgeon to work with after the prior-installed implant has been removed. In trauma cases, complex fractures may encourage resecting the tibial below the complex fracture area to simplify reconstruction. However, the tibia tapers distally. This causes a narrowing of the intramedullary canal (particularly in the metaphysis and diaphysis) and of the abutting inner cortical walls. Stated simply, with available tibial components, the more that the surgeon resects the proximal tibia, the less room the surgeon has when setting the resection angle of the tibia. If the angle it too steep, the keel of the tibial component will abut or penetrate the tibial cortex.
To avoid this problem, surgeons may choose to resect the tibia at 0 degrees varus and proceed with a mechanical alignment procedure. The mechanical alignment technique can provide good stability when the patient's leg is in extension (e.g., when the patient is standing), but the implants that are commonly used with this technique often require the release of the anterior cruciate ligament (“ACL”). In some circumstances, the posterior cruciate ligament (“PCL”) may also be released. The ACL normally prevents the tibia from sliding too far anteriorly and from rotating too far relative to the femur. The absence of either of these ligaments can lead to feelings of weakness when the leg is in flexion. Furthermore, changing the location of the patient's natural joint line can lead to feelings of discomfort. Patients who alter their gait to accommodate the new joint line may chronically stress the remaining muscles, which can further exacerbate the feelings of discomfort and contribute to additional musculoskeletal problems in the future.
The problem of the limited range of motion for tibial components of endoprosthetic knee implants in situations in which the proximal tibia is resected at an angle relative to a transverse plane is mitigated by a tibial component of an endoprosthetic knee implant comprising: a tibial baseplate; and a keel extending from a lower surface of the tibial baseplate, wherein a keel axis extends axially through the keel, wherein the tibial baseplate is disposed at a keel posterior angle relative to the keel axis, and wherein the tibial baseplate is disposed at a keel varus angle relative to the keel axis.
In these and other situations, it would be advantageous to have a tibial component of an endoprosthetic knee implant that is configured to provide a built-in varus tilt (i.e., keel varus angle) and a built-in posterior slope (i.e., keel posterior angle).
It would therefore be unique and advantageous to have tibial component of an endoprosthetic knee implant that is adapted to kinematic and/or anatomic knee arthroplasty techniques having the characteristics and features described herein.
It is contemplated that certain exemplary embodiments in accordance with the present disclosure may provide tibial components of endoprosthetic knee implants that are particularly adapted for use in kinematic or anatomic knee arthroplasty procedures.
It is further contemplated that certain exemplary embodiments in accordance with the present disclosure can include exemplary instruments for surgically installing exemplary tibial components of an endoprosthetic knee implants that are particularly adapted for use in kinematic or anatomic knee arthroplasty procedures.
It is still further contemplated that certain exemplary embodiments in accordance with the present disclosure can include kits comprising the exemplary tibial components, exemplary instruments therefore, or a combination thereof.
It is still further contemplated that the exemplary tibial components, instruments therefore, and kits thereof may be useful in revision procedures and primary procedures and of the primary procedures, particularly in stemmed primary procedures.
The foregoing will be apparent from the following more particular description of exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the disclosed embodiments.
The following detailed description of the preferred embodiments is presented only for illustrative and descriptive purposes and is not intended to be exhaustive or to limit the scope and spirit of the invention. The embodiments were selected and described to best explain the principles of the invention and its practical application. One of ordinary skill in the art will recognize that many variations can be made to the invention disclosed in this specification without departing from the scope and spirit of the invention.
Similar or the same reference characters indicate corresponding parts throughout the several views unless otherwise stated. Although the drawings represent 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 exemplifications are not to be construed as limiting the scope of the present disclosure.
Except as otherwise expressly stated herein, the following rules of interpretation apply to this specification: (a) all words used herein shall be construed to be of such gender or number (singular or plural) as such circumstances require; (b) the singular terms “a,” “an,” and “the,” as used in the 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 denotes an approximation with the deviation in the range or values known or expected in the art from the measurements; (d) the words, “herein,” “hereby,” “hereto,” “hereinbefore,” and “hereinafter,” and words of similar import, refer to this specification in its entirety and not to any particular paragraph, claim, or other subdivision, unless otherwise specified; (e) descriptive headings are for convenience only and shall not control or affect the meaning of construction of part of the specification; and (f) “or” and “any” are not exclusive and “include” and “including” are not limiting. Further, the terms, “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including but not limited to”).
References in the specification to “one embodiment,” “an embodiment,” “an exemplary embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, 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 skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether explicitly described.
To the extent necessary to provide descriptive support, the subject matter and/or text of the appended claims are incorporated herein by reference in their entirety.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range of any sub-ranges there between, unless otherwise clearly indicated herein. Each separate value within a recited range is incorporated into the specification or claims as if each separate value were individually recited herein. Where a specific range of values is provided, it is understood that each intervening value, to the tenth or less of the unit of the lower limit between the upper and lower limit of that range and any other stated or intervening value in that stated range of sub range thereof, is included herein 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 specifically and expressly excluded limit in the stated range.
It should be noted that some of the terms used herein are relative terms. For example, the terms, “upper” and, “lower” are relative to each other in location, i.e., an upper component is located at a higher elevation than a lower component in each orientation, but these terms can change if the orientation is flipped.
The terms, “horizontal” and “vertical” are used to indicate direction relative to an absolute reference, i.e., ground level. However, these terms should not be construed to require structure to be absolutely parallel or absolutely perpendicular to each other. For example, a first vertical structure and a second vertical structure are not necessarily parallel to each other.
Throughout this disclosure, various positional terms, such as “distal,” “proximal,” “medial,” “lateral,” “anterior,” and “posterior,” will be used in the customary manner when referring to the human anatomy. More specifically, “distal” refers to the area away from the point of attachment to the body, while “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, whereas the proximal femur refers to the portion of the femur near the hip. The terms, “medial” and “lateral” are also essentially opposites. “Medial” refers to something that is disposed closer to the middle of the body. “Lateral” means that something is disposed closer to the right side or the left side of the body than to the middle of the body. Regarding “anterior” and “posterior,” “anterior” refers to something disposed closer to the front of the body, whereas “posterior” refers to something disposed closer to the rear of the body.”
However, when referring to any component of the exemplary endoprosthetic implant or instruments described herein (e.g., an exemplary tibial component), particularly when such components are in an uninstalled or unassembled configuration, the various positional terms such as “distal,” “proximal,” “medial,” “lateral,” “anterior,” and “posterior,” absolute terms that refer to the associated position depicted in the accompanying figures and that do not change relative to the component's orientation is space. For example, a “proximal end” of a modular keel refers to the end indicated in the accompanying figures regardless of the orientation such “proximal end” relative to a reference (e.g., a person or the surface of the Earth).
“Varus” and “valgus” are broad terms and include without limitation, rotational movement in a medial and/or lateral direction relative to the knee joint.
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.
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, which is just above the ankle.
The term, “anatomic axis” refers to an imaginary line drawn lengthwise down the middle of femoral shaft or tibial shaft, depending upon use. The mechanical axis of the tibia and the anatomic axis of the tibia are generally considered to be co-linear.
Referring to
To initiate a typical revision knee arthroplasty, the surgeon makes a vertical midline incision on the anterior side of the operative knee. The incision is generally made with the knee in flexion at or below the tibial tuberosity and may extend several inches above the patella.
In a primary knee arthroplasty, the surgeon then continues to incise the fatty tissue to expose the anterior aspect of the joint capsule. The surgeon may then perform a medial parapatellar arthrotomy to pierce the joint capsule and resect the medial patellar retinaculum. A retractor is then commonly used to move the patella generally laterally to expose the distal condyles of the femur and the cartilaginous meniscus resting on the proximal tibial plateau. The surgeon then removes the meniscus and uses instrumentation to measure and resect the distal femur and proximal tibia to accommodate trial implants. Trial implants are test endoprostheses that generally have the same functional dimensions of the actual endoprostheses, but trial implants are designed to be temporarily installed and removed for the purposes of evaluating the fit of the actual endoprostheses and for the purposes of evaluating the knee joint's kinematics. The surgeon removes the trial implants and installs the actual implants once the surgeon is satisfied with the trial implant's sizing and the knee joint's kinematics.
Measurement and installation methods differ. Surgeons generally execute a mechanical alignment, anatomic alignment, or kinematic alignment technique according to preference, patient anatomy, the state of the operative joint, and available instruments.
To highlight the kinematic alignment technique and by way of example, a surgeon may proceed as described in U.S. Pat. No. 11,246,603 to Steensen et. al. The principle of kinematic alignment is that the surgeon uses instrumentation and implants to ascertain and restore the patient's natural pre-diseased joint line. The instruments described in U.S. Pat. No. 11,246,603 solve several issues encountered in kinematic techniques, such as allowing: the angle of the current or natural joint surface to be measured on both the femur and tibia; a wear factor to be used so that the measured amount of bone resection restores the joint surface to its pre-diseased level on both the femur and tibia; the surgeon to resect a specific amount of bone from the medial and lateral aspects of the joint surface on both the femur and tibia; the surgeon to visualize the angle of resection; the angle of resection to float infinitely, rather than in specific increments (within an acceptable range on both the femur and tibia); the surgeon to selectively lock the angle if desired; and the surgeon to measure the resection of the medial and lateral femoral condyles or of the medial and lateral tibial hemi-plateaus.
To summarize the distal resection step, the surgeon may ascertain the amount of cartilage wear on the distal condyles of the femur, attach a movable resection guide instrument to the exposed distal femur, and adjust the resection guide instrument to account for the measured loss of articular cartilage and the size of the implant. For example, if the implant is 10 mm in size and if the surgeon measures 2 mm of missing cartilage on the medial distal femoral condyle and 1 mm of missing cartilage on the lateral femoral condyle, the surgeon can adjust the resection guide instrument to position a resection slot to resect 8 mm of bone on the medial condyle and 9 mm of bone of the lateral condyle. The surgeon then inserts a saw or other cutting instrument through the resection slot to create the distal resection surface 5 at the desired angle and location.
By resecting the distal femur at this angle, the surgeon creates the first mating surface for the femoral component at an angle that is consistent with the angle of the patient's natural pre-diseased joint line when the knee is in extension (i.e., as depicted in
The surgeon may then place the knee in flexion (i.e., bend the knee) and repeat the measurement and resection process to create the posterior resection surface 3.
After creating the distal resection surface 5 and possibly the posterior resection surface 3, the surgeon may place a four-in-one cutting block (or separate resection guides) on the distal resection surface 5 to create the chamfer resection surfaces 8a, 8b, the anterior resection surface 2, and the posterior resection surface 3 if not made previously. The femoral component 30 has complementary faces that are disposed against the respective resection surfaces 5, 8a, 8b, 2, and 3 when the femoral component 30 is disposed in an installed configuration as shown in
It will be appreciated that the presence of the respective resection surfaces 5, 8a, 8b, 2, and 3 and the complementary mating faces of the femoral component 30 are the primary means by which the femoral component 30 is “configured to be engaged” to the resected distal end 12 of the femur 10. It will be further appreciated that the engagement side of the femoral component 30 may further comprise one or more projections (e.g., spikes) designed to be inserted into any one of the resection surfaces 5, 8a, 8b, 2, and 3 to further facilitate the engagement of the femoral component 30 to the resected distal end 12 of the femur 10. By way of further example, press-fit femoral components typically have a porous roughened surface on the engagement side. The porous surface permits regrowth of the bone into these pours over time.
Surgeons can also apply biocompatible “bone cement” to help secure the femoral component 30 to the resected distal end 12 of the femur 10. It will be appreciated that “bone cement” is a term of art used by people in the orthopedic industry even though bone cements themselves generally do not have adhesive properties. Bone cements generally rely on a close mechanical interlock between the irregular surface of the bone and the surface of the connective side of the endoprosthesis. Bone cements may or may not be laden with antibiotics depending upon the intended use. Common bone cements include polymethyl methacrylate (“PMMA”), calcium phosphate cements (“CPCs”), and glass polyalkenoate isomer cements (“GPICs”) . It will be appreciated that when present, the use of projections, porous roughened surfaces, and/or “bone cement” to further facilitate engaging the femoral component 30 to the distal end 12 of the femur 10 and can therefore also fall within the scope of the “femoral component 30 configured to be engaged to the resected distal end 12 of the femur 10” language. Bone cement is difficult to remove once cured. Bone cement's presence is a significant factor that contributes to the need to resect the supportive bone in revision procedures.
Creating the resected proximal end 13 of the tibia 20 can be completed before or after the femur 10 is resected. A cutting guide is typically placed on the anterior surface of the tibia 20, and the surgeon can adjust the varus and valgus angle of resection and optionally the posterior slope of resection depending upon the elected knee alignment method (e.g., anatomic, mechanical, or kinematic). Once the resection angle is set, the surgeon inserts a saw or other cutting instrument through a resection slot in the tibia resection guide to create the resected tibial surface 23. For example, in a kinematic operation, the tibial longitudinal axis LA (i.e., a projected stem axis) is determined and the tibia 20 is resected relative to the tibial longitudinal axis LA. The tibia 20 is resected at a varus tilt 90 -δ sloping down from the lateral L to the medial M side, commonly at about three degrees relative to the keel longitudinal axis KLA. The tibia is further resected at a posterior slope 90−θ that slopes down from the anterior side A to the posterior side P of the patient's tibia 20, commonly at about three degrees relative to the keel longitudinal axis KLA. The surgeon may then use the exemplary punch guide 83 described further below to insert a reamer and/or punch (see 73,
The keel 43 is then inserted into the cavity (see
In a revision procedure (i.e., a subsequent knee arthroplasty in which the surgeon removes and replaces a prior installed endoprosthetic knee implant), the surgeon may release scar tissue around the patellar tendon after the surgeon has performed the initial incision. The surgeon can then move (i.e., preform a subluxation of) the patella or patellar implant generally laterally to expose the prior-installed implant, which usually has a femoral component installed on the distal femur, a tibial component installed on the proximal tibia, and a meniscal insert disposed between the femoral component and the tibial component. The surgeon then removes the prior-installed implant.
It will be appreciated that the type of prior-installed implant can vary from case to case. Prior-installed implants can include static spacers that have been inserted into aligned intramedullary bores in the distal femur and proximal tibia to immobilize the knee joint, or complex implants that have been used to reconstruct portions of the knee joint that had undergone trauma. However, common prior-installed implants include implants installed during a primary total or partial knee arthroplasty, or prior revision implants.
Removal of the prior-installed implants generally involves cutting away the bone underlying the bone cement—or in the case of press-fit implants, the bone underlying the press-fit implant. This resection exposes fresh bone capable of receiving a revision press-fit or bone cement bondable implant. Removing bone to remove the prior-installed implant would move the joint line if the revision implant was not sized to replace the newly resected bone.
In the depicted embodiment, the resected tibial surface 23 of a given tibia 20 is not perfectly symmetrical. Moreover, the left tibia is chiral to the right tibia. In the depicted embodiment, a given baseplate 45 is typically designed for either the left tibia or the right tibia. The anterior side A, posterior side P, medial side M, and the lateral side L of a given baseplate 45 are desirably sized and shaped to closely approximate the profile (i.e., perimeter) of the resected tibial surface 23 (see
In the exemplary embodiments shown in
In general, the femoral component 30, tibial component 40, and meniscal insert 50 can be made from any biocompatible material designed to withstand the stress of repeated and normal use of the knee. In practice, the femoral component 30 and tibial component 40 are frequently made from cobalt-chromium alloys, titanium, titanium alloys, zirconium, zirconium alloys, nickel, or nickel alloys. In certain embodiments, these components, particularly the femoral component 30, may have a ceramic coating (or may comprise an outer ceramic layer) on the articular surface. In other embodiments, the entire femoral component 30 can be made from ceramic. In still other embodiments, the entire tibial component 40 can be made from ceramic. The meniscal insert 50 is typically made from ultra-high molecular weight polyethylene (“UHMWPE”) or from a ceramic.
Reference is made to
As shown in
For the purposes of this disclosure, a “keel posterior angle” θ is the acute angle defined by the intersection between the anterior-posterior line A-P of the baseplate plane BPP (represented by BPP in
A “posterior slope” in this context is a term of art that typically refers to the anterior to posterior orientation of the resected tibial surface 23. A “posterior slope” is typically thought of as the angle of the anterior-posterior line A-P of the resected tibial surface 23 relative to an intersecting transverse plane TRP. Because the lower surface 41 of the baseplate 45 is desirably disposed on the resected tibial surface 23 and oriented parallel to the resected tibial surface 23 in an installed configuration, the “posterior slope” can also refer to the anterior to posterior orientation of the baseplate 45 of the exemplary tibial components 40 described herein regardless of orientation; however, this relationship is especially pronounced when said baseplate 45 is oriented as it would be in the installed configuration.
For the purposes of this disclosure, a “keel varus angle” δ can be described as the acute angle defined by the intersection between the medial lateral line M-L of the baseplate plane BPP (represented by BPP in
A “varus tilt” in this context is a term of art that refers to the medial to lateral orientation of the resected tibial surface 23. A “varus tilt” is typically thought of as the angle of the medial-lateral line M-L of the resected tibial surface 23 relative to an intersecting transverse plane TRP. Because the lower surface 41 of the baseplate 45 is desirably disposed on the resected tibial surface 23 and oriented parallel to the resected tibial surface 23 in an installed configuration, the “varus tilt” can also refer to the medial to lateral orientation of the baseplate 45 of the exemplary tibial components 40 described herein regardless of orientation; however, this relationship is especially pronounced when said baseplate 45 is oriented as it would be in the installed configuration.
In this manner, the compound angle for the exemplary tibial components 40 described herein can also be said to comprise a posterior slope (90−θ) and a varus tilt (90−δ).
The exemplary tibial component 40 of an endoprosthetic knee implant 1 can be provided in a unitary (i.e., non-modular; unibody; comprising a single piece) embodiment. In other exemplary embodiments, the keel 43 and the baseplate 45 can be modular, as described below.
The tibial component 40 includes a baseplate 45 (which is also known as a “tibial tray”) and a unitary keel 43 extending downwardly from a lower surface 41 of the baseplate 45. The keel 43 can comprise one or more fins 46 extending outwardly from the keel 43. The fins 46 are typically disposed in the transverse plane TRP when the tibial component 40 is in the installed configuration. In exemplary embodiments, the fins 46 can be disposed at a compound angle relative to the baseplate plane BBP, wherein the compound angle comprises a keel posterior angle and a keel varus angle as described herein. In other exemplary embodiments, the fins 46 can be oriented relative to the keel 43 as the fins 46 would be for a mechanically aligned tibial component.
It will be appreciated that the “non-modular” or “unitary” embodiments described herein can refer to tibial components 40 that have been manufactured as a single piece (e.g., by casting, machining, additive manufacturing, etc.) and to tibial components 40 that have been manufactured as separate pieces (e.g., a baseplate portion 45 and keel portion 43) but that are fixedly engaged to each other in a non-readily-removable manner when made available to the surgeon for the operative procedure (for modular embodiments, see
In certain exemplary embodiments, the distal end 44 of the keel 43 is preferably rounded. The rounded distal end 44 reduces the risk of unnecessarily shaving off of proximate cancellous bone and bone marrow during the installation process. In other exemplary embodiments, the distal end 44 of the keel 43 can be substantially straight, wedge shaped, wedge shaped with a rounded end, conical, conical with a rounded end, frustoconical, frustoconical with a rounded end, pyramidal, pyramidal with a rounded end, frustopyramidal, frustopyramidal with a rounded end, or combinations thereof. Shapes that have a generally convex profile are generally preferable to reduce the risk of unnecessarily ablating cancellous bone and bone marrow during the installation process. All shapes having a generally convex profile are considered to be within the scope of this disclosure. An upper surface 42 of the baseplate is configured to selectively secure the meniscal insert 50 to the baseplate 45. The keel 43 has a keel longitudinal axis KLA extending lengthwise therethrough (i.e., the keel longitudinal axis KLA is disposed parallel to the height h dimension of the keel 43). Unlike prior tibial components 40, the baseplate 45 is not oriented perpendicular to the keel 43 but is instead oriented at a compound angle comprising a keel posterior angle θ and a keel varus angle δ. Without being bound by theory, it is thought that such embodiments can assist in kinematic or anatomic alignment procedures. Moreover, it is contemplated that use of the exemplary tibial components 40 described herein may permit a surgeon to use kinematic alignment or anatomic alignment procedures in revision knee arthroplasties that might not otherwise have been possible using conventional tibial components.
As can be seen in the side view of
Stated differently, the intersection of the anterior-posterior line A-P line of the baseplate plane BPP and a transverse plane TRP defines a posterior slope (90θ).
The transverse plane TRP can be imagined to be disposed perpendicular to the keel longitudinal axis KLA of the keel 43 in both the coronal plane CP (
Stated differently, the medial-lateral line M-L of the baseplate plane BPP intersects the transverse plane TRP at the medial side M to define a varus tilt 90−δ. The varus tilte 90−δ may be greater than zero degrees to less than or equal to seven degrees. However, in many applications, the varus tilt 90−δ is set at about three degrees. It will be appreciated that tibial components 40 having different combinations of preset keel varus 90−δ and keel posterior angles θ (and therefore corresponding present varus tilts 90−δ and posterior slopes 90−θ) are considered to be within the scope of this disclosure.
Without being bound by theory, it is contemplated that by having a sloped baseplate 45 relative to the keel longitudinal axis KLA in the manner described, that extends into the intramedullary canal 27 when the tibial component 40 is in the installed configuration such that the keel 43 is substantially aligned with (i.e., is coaxial with) the longitudinal axis LA of the tibia 20 and such that the keel 43 is disposed perpendicular to a sagittal plane SP (see
However, it will be appreciated that the exemplary tibial components 40, when in the installed configuration, do not necessarily need to have the keel longitudinal axis KLA to be fully aligned with the longitudinal axis LA of the tibia 20. In such embodiments, the keel 43 is not necessarily disposed perpendicular to both the sagittal plane SP and the coronal plane CP (see
As a result, and without being bound by theory, it is contemplated that the exemplary embodiments disclosed herein may permit the surgeon to insert longer keels 43 into the tibia 20 than was previously possible, especially in cases where the resected proximal end 13 of the tibia 20 was disposed at a slope (particularly at a compound angle comprising a varus tilt 90−δ and a posterior slope 90−θ). The longer keels 43 can more firmly stabilize and secure the tibial component 40 to the tibia 20 in kinematic alignment procedures and in anatomic alignment procedures over what was previously possible. It is still further contemplated that by aligning the keel longitudinal axis KLA with the longitudinal axis LA of the tibia 20, the force vectors that result from the natural ambulatory movement of the knee can be more stably transferred through the tibial component 40 to the tibia 20 and thereby prolong the useful life of the endoprosthetic knee implant 1. For example, when a person is standing, it is thought that the force exerted on the tibial component 40 from the mass of the person above the tibial component 40 can be more stably transferred to the feet of the person because the keel 43 of the tibial component 40 is desirably oriented closer to the mechanical axis of the tibia 20 (i.e., the longitudinal axis LA). The tibia has naturally evolved to distribute the force of the mass of a person generally along the mechanical axis toward the feet. By substantially aligning the keel longitudinal axis KLA with the longitudinal axis of the tibia, it is thought that the exemplary embodiments described herein may preserve the natural force distribution and kinematics of a pre-diseased natural knee over what was previously possible.
In the depicted embodiment, the distal end 44 of the keel 43 comprises a tapered bore, the bore is sized to closely receive a tapered extension on the proximal end 49 of the distal stem extension 100, in a press-fit secured configuration. As can be seen in
Although
As can be seen in the side view of
The distal stem extension 100 may have grooves 98 disposed generally parallel to the keel longitudinal axis KLA when installed on the keel 43. These grooves 98 can facilitate the installation of the distal stem extension 100 into the intermedullary canal 27 (
The distal end 51 of the distal stem extension 100 can be selected from a variety of shapes. In certain exemplary embodiments, the distal end 51 of the distal stem extension 100 can be rounded, substantially straight, wedge shaped, wedge shaped with a rounded end, conical, conical with a rounded end, frustoconical, frustoconical with a rounded end, pyramidal, pyramidal with a rounded end, frustopyramidal, frustopyramidal with a rounded end, or combinations thereof. Shapes that have a generally convex profile are generally preferable to reduce the risk of unnecessarily ablating cancellous bone and bone marrow during the installation process. All such shapes having a generally convex profile and considered to be within the scope of this disclosure.
Without being bound by theory, it is contemplated that a removable distal stem extension 100 may permit surgeons to select from a group of available distal stem extensions 100 provided in a kit on the day of the procedure. Common of types of distal stem extensions 100 include press-fit stem extensions and cemented stem extensions. The surgeon or the technician can select from the provided group of available stem extensions 100 to effectively change the overall height of the tibial component 40 without having to rely on selectively testing and removing multiple unitary tibial components 40. The number of distal stem extensions 100 available to the surgeon can depend upon a number of factors, including the existence of a pre-operative measurements taken of the interior of the tibia 20 through radiography or other imaging methods.
Without being bound by theory, it is contemplated that by having a sloped baseplate 45 relative to the keel longitudinal axis KLA in the manner described that extends into the intramedullary canal 27 when the tibial component 40 is in the installed configuration such that the stem construct 143 is substantially aligned with the longitudinal axis LA of the tibia 20 and such that the stem construct 143 is disposed perpendicular to a sagittal plane SP (see
As a result, it is contemplated that the exemplary embodiments disclosed herein may permit the surgeon to insert longer stem constructs 143 into the tibia 20 than was previously possible in cases where the resected proximal end 13 of the tibia 20 was disposed at a slope (i.e., in a prior kinematic alignment or anatomic alignment procedure. Previously, stemmed revision-style tibial components were only usable with a revision mechanical alignment procedure regardless of whether the patient had undergone a primary kinematic alignment or a primary anatomic alignment procedure. Such procedures were previously not possible because of the amount of bone that had to be removed to extract the pre-existing implant and because the removal of existing bone necessarily reduced the amount of available volume (particularly the length and width dimensions) in the remaining intramedullary canal 27 in which to insert a stabilizing keel 43 or stem construct 143.
It is further contemplated that the exemplary embodiments described herein may permit a surgeon to perform a kinematic alignment or an anatomical alignment procedure in a revision procedure (i.e., a secondary surgery in which the original implant is removed) or in trauma cases that feature severely compromised tibial bone. Without being bound by theory, it is conceivable that a patient who underwent a mechanical alignment knee arthroplasty during a primary or prior revision procedure may now be able to benefit from a kinematic or anatomic alignment procedure.
Nothing in this disclosure limits the use of the exemplary tibial components and related instruments therefore to revision procedures, however. It is contemplated that such exemplary tibial components and/or exemplary instruments described herein can be used in primary procedures. It is believed that surgeons may especially benefit from the embodiments of the present disclosure in stemmed primary procedures.
Stemmed primary procedures are often used with patients with a high body mass index or that suffer from poor bone quality. It is thought that the use of a distal stem extension 100 in these cases can more reliably and more effectively distribute the stationary and ambulatory forces that a patient and the tibial component 40 with a stem construct 143 experiences.
In this manner, it is contemplated that the longer stem constructs 143 can more firmly stabilize and secure the tibial component 40 to the tibia 20 in kinematic alignment procedures and in anatomic alignment procedures over what was previously possible. It is still further contemplated that by aligning the keel longitudinal axis KLA with the longitudinal axis LA of the tibia 20, the force vectors that result from the natural ambulatory movement of the knee can be more stably transferred through the tibial component 40 to the tibia 20 and thereby prolong the useful life of the endoprosthetic knee implant 1.
As will be appreciated from the foregoing discussion, all embodiments of the tibial component 40 can be configured for use on right or left knees. In other exemplary embodiments, the exemplary tibial component can comprise a symmetric baseplate 45.
Referring to
It will be appreciated that the proximal end 61 of the modular keel can define a compound angle comprising a keel varus angle δ and a keel posterior angle θ. As a result, it is contemplated that the modular keel 43 can be chiral. That is, a left-sided modular keel 43 is configured to engage a left-sided baseplate 45 while a right-sided modular keel 43 is configured to engage a right-sided baseplate 45.
The modular keel 43 defines a compound angle at the proximal end 61, wherein the compound angle comprises a keel posterior angle θ (see
When viewed in the depicted orientation, the proximal end 61 of the keel 43 can also be imagined to be disposed at a varus tilt 90−δ relative to a transverse plane TRP. It will be appreciated that when the depicted modular keel 43 is assembled with a modular baseplate 45 (see
As with the unitary embodiments, the varus tilt 90−δ of the modular keel 43 embodiments can be about three degrees for most patients, but angles greater than zero and less than or equal to seven degrees are considered to be within the scope of this disclosure. Multiple modular keels 43 may be provided at the time of a surgical procedure. Of the provided modular keels 43, one or more provided keels may have different compound angles (including but not limited to, for the sake of example, provided keels 43 having different keel varus angles δ, different keel posterior angles θ, or combinations thereof).
When viewed in the depicted orientation, the proximal end 61 of the keel 43 can also be imagined to be disposed at a varus tilt 90−δ relative to a transverse plane TRP. It will be appreciated that when the depicted modular keel 43 is assembled with a modular baseplate 45 (
As with the unitary embodiments, the posterior slope 90−θ of the modular keel 43 embodiments can be about three degrees for most patients, but angles greater than zero and less than or equal to fifteen degrees are considered to be within the scope of this disclosure.
In certain exemplary embodiments, the modular keel 43 may have a distal end 44 that is not configured to engage a distal stem extension 100. In such embodiments, the distal end 44 of the modular keel 43 can be rounded, substantially straight, wedge shaped, wedge shaped with a rounded end, conical, conical with a rounded end, frustoconical, frustoconical with a rounded end, pyramidal, pyramidal with a rounded end, frustopyramidal, frustopyramidal with a rounded end, or combinations thereof. Shapes that have a generally convex profile are generally preferable to reduce the risk of unnecessarily ablating cancellous bone and bone marrow during the installation process. Such generally convex shapes can also reduce stress risers in the bone cement.
In other exemplary embodiments comprising a modular keel 43, the distal end 44 can be configured to selectively engage a distal stem extension 100 in substantially the same manner as described above (see generally
Without being bound to theory, it is contemplated that combinations of the modular keel 43 and of the distal stem extensions 100 can allow the surgeon to select a constructed tibial component 40 that more closely matches the patient's anatomy after the tibia 20 has been resected at a compound angle (comprising a posterior slope 90−θ and a varus tilt 90−δ) than what was previously available. The modular keel 43 and distal stem extension 100 may allow the surgeon to insert the stem construct 143 of an optimal height such that the keel longitudinal axis KLA is substantially aligned with the tibial longitudinal axis LA while being disposed generally perpendicular to an intersecting sagittal plane SP and a coronal plane CP. In this manner, surgeons can practice kinematic and anatomic alignment methods without risking using a shorter keel 43 or stem construct 100 on the tibial component 40 and without risking the keel 43 or stem construct 100 contacting an inner cortical wall 25a, 25l, 25m, 25p of the tibia 20.
In the depicted embodiment, the projection 65 is a tapered projection and the receiver 56 is a tapered receiver that closely receives the tapered projection and, in this manner, “fixedly engages” the modular baseplate 45 to the modular keel 43. However, all methods of mechanically and securely engaging the modular keel 43 to the modular baseplate 45 are considered to be within the scope of this disclosure. Examples of such other mechanical engagement mechanisms include screws, pins, and any other locking projection and receiver mechanism known by those having ordinary skill in the art.
The embodiment of
The depicted embodiment shows the distal end of the keel 43 engaging a distal stem extension 100 to define a stem construct 143. However, in other exemplary embodiments, the distal end of the offset keel 43 can be generally rounded as described above. In other exemplary embodiments, the offset keel 43 can be modular and selectively attachable to the tibial baseplate 45. It is contemplated that modular offset keels 43 and unitary offset tibial components 40 can be provided in left knee and right knee configurations.
The tibial components 40 described herein can be provided in the form of a kit. For example, any of the tibial components 40, modular tibial baseplate 45, distal stem extensions 100, and modular keels 43 (including but not limited to non-offset modular keels and offset modular keels) can be provided with a plurality of different sizes. Chiral components can be provided for a left knee and a right knee. The tibial components 40 and/or the modular keels 43 can be provided in a number of different compound angles, wherein of the number of different compound angles, the compound angles differ by at least one of a difference in keel posterior angle θ and/or keel varus angle S. Optionally, exemplary kits may further comprise offset adaptors, angle adaptors, augments, meniscal inserts, femoral components, trial components, or combinations of any thereof. The components of the kit are preferably arranged in a convenient format, such as in a surgical tray or case. However, the kit components do not have to be packaged or delivered together, provided that they are assembled or collected together in the operating room for use at the time of surgery.
An exemplary kit can include any suitable embodiment of an exemplary tibial component 40, variations of the exemplary tibial components 40 described herein, and any other exemplary tibial component 40 according to an embodiment (including sub-components thereof such as a modular keel 43 and a modular baseplate 45). While it is contemplated that an exemplary kit may include one or more tibial components 40 and one or more distal stem extensions 100, it will be appreciated that certain kits may lack some or all of these components.
Any suitable embodiment of a tibial baseplate 45, variations of the tibial baseplates 45 described herein, and any other tibial baseplate 45 according to an embodiment are considered to be within the scope of this disclosure.
Likewise, any suitable embodiment of a modular keel 43, variations of the modular keels 43 described herein, and any other modular keel 43 according to an embodiment are considered to be within the scope of this disclosure.
Still further likewise, any suitable embodiment of a distal stem extension 100, variations of the distal stem extensions 100 described herein, and any other distal stem extension 100 according to an embodiment are considered to be within the scope of this disclosure.
Selection of a suitable number or type of tibial components 40, tibial baseplates 45, modular keels 43, and distal stem extensions 100 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.
The punch guide 83 has a guide distal end 84 distally disposed from a guide proximal end 81 along a guide body 88. As seen more clearly in
The center portion of the through channel 85 of the depicted punch guide is further sized and dimensioned to guide a reamer into the tibial intramedullary canal 27. As seen in
In practice, when the exemplary instruments are arranged in an assembled and installed configuration (discussed further below), the surgeon can first insert a reamer (which generally resembles a large threaded drill bit) through the through channel 85 to create an initial intramedullary cavity. Depending upon the size of the patient's tibia, multiple reamers of progressively larger sizes may be inserted through the through channel 85 to iteratively enlarge the dimensions of the initial intramedullary cavity. After the initial intramedullary canal has been reamed to the desired dimensions, the surgeon can remove the reamer and then insert an exemplary keel punch 73 through the through channel 85 to define an intramedullary cavity that is generally complementary to the profile of the keel punch 73. In certain exemplary procedures, multiple keel punches 73 of progressively larger sizes may be inserted through one or more punch guides 83 to define an intramedullary cavity that is generally complementary to the profile of the desired size of an exemplary keel 43 of an exemplary tibial component 40. It is contemplated that multiple exemplary punch guides 83 may be provided in different sizes at the time of the surgical procedure.
Referring back to the structure of the depicted exemplary punch guide 83 with particular reference to
Moreover, as better seen in
The keel punch 73 can be affixed to the distal end of a broach handle. The surgeon can insert the keel punch 73 through the through channel 85, which guides the keel punch 73 into the resected surface 23 of the tibia 20 at the desired keel posterior angle θ and keel varus angle δ. The surgeon may use a mallet to hammer the proximal end of the broach handle to insert the keel punch 73 into the resected surface 23 of the tibia 20. In this manner, the surgeon can create a keel cavity in the intramedullary canal 27 of the tibia 20 at the desired keel posterior angle θ and keel varus angle δ to accommodate an exemplary keel 43 of an exemplary tibia component 40.
It will be appreciated that the keel punch 73 and the punch guide 83 can be provided in different sizes. A surgeon may insert and remove successively larger sizes of the punch guide 83 and keel punch 73 to iteratively create a successively larger keel cavity in the intramedullary canal 27 until the desired size of the keel 43 of the tibial component 40 is achieved. Upon achieving the desired size and optionally evacuating any residual material from the keel cavity, the surgeon may insert the keel 43 of any of the exemplary tibial components 40 described herein into the keel cavity at the desired angle and position.
The exemplary instrument assemblies 70 described herein can be provided in the form of a kit. For example, the exemplary keel punch 73 and exemplary punch guide 83 can be provided with a plurality of different sizes. Chiral components can be provided for a left knee and a right knee. The keel punch 73 and/or punch guide 83 can be provided in a number of different compound angles, wherein of the number of different compound angles, the compound angles differ by at least one of a difference in keel posterior angle θ and/or keel varus angle δ. Optionally, exemplary kits may further comprise mallets, trial tibial baseplates, broach handles, or combinations of any thereof. The components of the kit are preferably arranged in a convenient format, such as in a surgical tray or case. However, the kit components do not have to be packaged or delivered together, provided that they are assembled or collected together in the operating room for use at the time of surgery.
An exemplary kit can include any suitable embodiment of an exemplary keel punch 73, variations of the exemplary keel punches 73 described herein, and any other exemplary keel punch 73 according to an embodiment. While it is contemplated that an exemplary kit may further include one or more trial tibial baseplates 45, it will be appreciated that certain kits may lack some or all of these components.
Any suitable embodiment of a punch guide 83, variations of the punch guides 83 described herein, and any other punch guide 83 according to an embodiment are considered to be within the scope of this disclosure.
Selection of a suitable number or type of keel punches 73 and punch guides 83 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.
An exemplary tibial component of an endoprosthetic knee implant comprises: a tibial baseplate; and a keel extending from a lower surface of the tibial baseplate, wherein a keel longitudinal axis extends axially through the keel, wherein the tibial baseplate is disposed at a keel posterior angle relative to the keel longitudinal axis, and wherein the tibial baseplate is disposed at a keel varus angle relative to the keel longitudinal axis.
In an exemplary tibial component, the keel posterior angle can be less than 90 degrees and can be greater than or equal to about 75 degrees.
In an exemplary tibial component, the keel varus angle can be less than 90 degrees and can greater than or equal to about 83 degrees.
In an exemplary tibial component, a distal stem extension can be removably engaged to the keel.
In an exemplary tibial component, the keel can be a modular keel, and wherein the modular keel is removably engaged to the tibial baseplate.
In an exemplary tibial component, the keel longitudinal axis can be aligned with the longitudinal axis of the tibia in both the sagittal plane and the coronal plane when the tibial component is disposed in an installed configuration.
An exemplary tibial component comprises: a tibial baseplate having an upper surface, a lower surface, an anterior side distally disposed from a posterior side, and a medial side distally disposed from a lateral side, wherein a first line connecting the anterior side and the posterior side, defines an anterior-posterior line, wherein a second line connecting the medial side to the lateral side defines a medial-lateral line, and wherein the anterior-posterior line is disposed perpendicular to the medial-lateral line on a tibial baseplate plane; and a keel descending from the lower surface of the tibial baseplate, wherein the anterior-posterior line of the tibial baseplate is disposed at a posterior slope relative to a transverse plane intersecting the tibial component, and wherein the medial-lateral line of the tibial baseplate is disposed at a varus tilt relative to the transverse plane intersecting the tibial component.
In an exemplary tibial component, the posterior slope can be greater than zero degrees and can be less than or equal to about 15 degrees.
In an exemplary tibial component, the varus tilt can be greater than zero degrees and can be greater than or equal to about 7 degrees.
In an exemplary tibial component, a keel longitudinal axis can extend along a height of the keel, the keel longitudinal axis can be aligned with the longitudinal axis of the tibia when the tibial component is in an installed configuration.
In an exemplary tibial component, the tibial baseplate plane can be parallel to the anterior-posterior line and the medial-lateral line.
An exemplary modular keel comprises: a keel body; and a keel proximal end, wherein a keel longitudinal axis extends axially through the keel body, wherein the keel proximal end is disposed at a keel posterior angle relative to the keel longitudinal axis, and wherein the keel proximal end is disposed at a keel varus angle relative to the keel longitudinal axis.
An exemplary modular keel can further comprise fins extending transversely from the keel body.
An exemplary modular keel can further comprise a receiver in the keel proximal end, wherein the receiver is configured to selectively fixedly engage a complementary projection extending from a lower end of a tibial baseplate.
An exemplary modular keel can further comprise a projection in the keel proximal end, wherein the projection is configured to selectively engage a complementary receiver defined by a tibial baseplate.
An exemplary instrument assembly can comprise: a keel punch, the keel punch having a punch proximal end distally disposed from a punch distal end along a body, wherein the punch proximal end is disposed at a keel posterior angle relative to a keel longitudinal axis extending along a height dimension of the keel punch, and wherein the punch proximal end is disposed at a keel varus angle relative to the keel longitudinal axis extending along the height dimension of the keel punch; and a punch guide configured to closely receive the keel punch, the punch guide having a guide distal end distally disposed from a guide proximal end along a guide body, wherein the guide distal end is disposed at a guide posterior angle relative to a guide longitudinal axis extending along a height dimension of the punch guide, and wherein the guide distal end is disposed at a guide varus angle relative to a guide longitudinal axis extending along the height dimension of the punch guide.
An exemplary instrument assembly can further comprise a trial tibial baseplate, wherein the guide distal end further comprises spikes configured to extend through holes in the trial tibial baseplate.
An exemplary instrument assembly can further comprise a reamer extending through a through channel defined by an inner wall of the guide body of the punch guide to from the guide proximal end to the guide distal end.
Although 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 as covering all alterations and modifications that fall within the true spirit and scope of the invention.
This application claims the benefit of priority to U.S. Provisional Application No. 63/264,332 filed on Nov. 19, 2021. The disclosure of this related application is hereby incorporated into this disclosure in its entirety.
Number | Date | Country | |
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63264332 | Nov 2021 | US |