Patent Application
20150093283
Embodiments described herein relate to devices and methods for manufacturing implants, implant components and/or related tools using additive metals technologies, including SLM (selective laser melting) technologies. More specifically, various embodiments described herein include methods for improving the SLM manufacture of femoral implant components forming a portion of a patient-adapted knee joint implant.
Historically, diseased, injured or defective joints, such as, for example, joints exhibiting osteoarthritis, were repaired using standard off-the-shelf implants and other surgical devices. Surgical implant systems that employed a one-size-fits-all approach to implant design (and even those that utilized a “few-sizes-fit-all” approach, including modularly assembled systems) did not typically require highly accurate information about the patient's anatomy. Instead, such systems utilized gross anatomical measurements such as the maximum bone dimensions at the implant site, as well as the patient weight and age, to determine a “suitable” implant. The surgical procedure then concentrated on altering the underlying bony anatomical support structures (e.g., by cutting, drilling and/or otherwise modifying the bone structures) to accommodate the existing contact surfaces of the pre-manufactured implant. With these systems, varying quantities of implants and/or implant components would be manufactured and stockpiled. Once a potential patient was identified, an appropriate implant and/or component would be selected, transported to the surgical location and utilized in the patient's surgical procedure.
More recently, the joint replacement field has come to embrace the concept of “patient-adapted” (i.e., “patient-specific” and/or “patient-engineered”) implant systems. With such systems, the surgical implants, associated surgical tools and procedures are designed or otherwise modified to account for and accommodate the individual anatomy of the patient undergoing the surgical procedure. Such systems typically utilize non-invasive imaging data, taken of the individual pre-operatively, to guide the design and/or selection of the implant, surgical tools, and the planning of the surgical procedure itself. Various objectives of these newer systems include (1) reducing the amount of bony anatomy removed to accommodate the implant, (2) designing/selecting an implant that replicates and/or improves the function of the natural joint, (3) increasing the durability and functional lifetime of the implant, (4) simplifying the surgical procedure for the surgeon, (5) reducing patient recovery time and/or discomfort, and (6) improving patient outcomes.
Because “patient-specific” and “patient-engineered” implant systems are created using anatomical information from a particular patient, such systems are generally created after the patient has been designated a “surgical candidate” and undergone non-invasive imaging. But, because such systems are not generally pre-manufactured and stockpiled in multiple sizes (as are traditional systems), there can be a considerable delay between patient diagnosis and the actual surgery, much of which is due to the amount of time necessary to design and manufacture the “patient-specific” and/or “patient-engineered” implant components using patent image data.
A significant portion of any delay between patient diagnosis/imaging and actual surgery can often be attributed to the time needed to manufacture each “patient-specific” and/or “patient-engineered” implant system to a particular patient's anatomy. Usually, such implants are manufactured individually or in small batches, using a 3rd party vendor, which can greatly increase the cost of creating such implant components as compared to the large batch manufacturing used with traditional non-custom implants.
In addition, because “patient-specific” and/or “patient-engineered” implant systems are manufactured in limited quantities, a fracture, failure or sufficient discrepancy identified at any point in the manufacturing process can have significant consequences, including the non-availability of implant components when needed and/or a requirement to remanufacture implant components and/or ordering implants on an expedited (and much more expensive) basis to meet deadlines.
Accordingly, there is a need in the art for advanced methods, techniques, devices and systems to ensure the availability of “patient-specific” and/or “patient-engineered” implant components for a scheduled surgery in a cost effective and efficient manner.
The embodiments described herein include advancements and improvements in or related to the use of additive manufacturing techniques, including Selective Laser Melting (SLM) manufacturing techniques, in the design, selection, development, manufacturing and/or finishing of patient-specific and/or patient-engineered implant components. Various embodiments described herein facilitate the production of “patient-specific” or “patient-engineered” implants in a more cost effective and/or efficient manner.
Various embodiments described herein include methods for improving the strength, quality, performance and/or durability of implant components manufactured using SLM or similar material-additive manufacturing techniques.
Various embodiments described herein include methods of improving and/or simplifying the post-manufacture processing and/or “finishing’ of an implant component manufactured using SLM or similar material-additive manufacturing techniques.
Various embodiments described herein include methods of assessing and/or optimizing SLM manufacturing methods and/or modifying implant design features to accommodate different limitations associated with SLM manufacturing techniques and processes.
It is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.
Objects, aspects, features, and advantages of various embodiments will become more apparent and may be better understood by referring to the following description, taken in conjunction with the accompanying drawings, in which:
Additional figure descriptions are included in the text below. Unless otherwise denoted in the description for each figure, “M” and “L” in certain figures indicate medial and lateral sides of the view, respectively; “A” and “P” in certain figures indicate anterior and posterior sides of the view, respectively; and “S” and “I” in certain figures indicate superior and inferior sides of the view, respectively.
A number of significant challenges face the widespread adoption of patient-specific implants and associated surgical procedures, many of which relate to the amount of time required to manufacture the implant, as well as the significant costs associated with creating a unique implant for each individual surgical patient. Unlike standard and/or modular implants, which can be manufactured in bulk and stored for use as needed, patient-specific implants are generally created after a patient has been identified as a surgical candidate, and the implant is designed and/or selected using imaging data taken of the intended patient's anatomy. The process of designing, manufacturing and finishing the implant can involve a number of steps, typically involving multiple vendors, and this process must result in an acceptable implant before the surgery can occur. In some cases, traditional methods of creating of a patient-specific implant from patient imaging data can require more than 4 to 7 weeks, which is a significant delay for both the surgeon and the patient.
An additional challenge facing the acceptance of patient-specific implants relates to the significant costs associated with creating a unique implant for each individual patient. The unique nature of each patient-specific implant does not lend their creation to bulk manufacturing methods including high-volume casting techniques. Rather, individual implant components are generally designed and investment cast on an individual basis, or can be designed and machined from bulk raw materials, which can be a time-consuming and expensive process.
An additional concern relating to the use of patient-specific implants relates to the availability of processing and manufacturing equipment, as well as the assurance that the implant components will be processed and available for the surgical procedure. Because each patient-specific implant is unique, and because a significant amount of time and effort is required to create each implant, it is typical practice to manufacture multiple copies (e.g., a primary and a backup implant) of an implant for a single patient, to ensure that at least one implant survives the manufacturing, finishing and testing processes prior to surgical use. However, because such backup implants are only needed where the primary implant has failed, the constant creation of backup implants leads to unused inventory and unnecessary costs where the primary implant does not get damaged. In addition, creating a backup patient-specific implant often leads to significant wastage where the primary implant is deemed acceptable (which occurs in the vast majority of cases), as the backup implant is generally useless for any other patient and/or procedure and is typically scrapped. Moreover, there are occasions where the primary and back-up implant castings are both damaged, fractured and/or undergo processing missteps that render both implants useless, and there may not be an opportunity to remanufacture another suitable implant within a desired timeframe (or at a desired cost without significant expedited processing fees) for a variety of reasons, which can include a lack of personnel, equipment and/or unavailability of raw materials to create a replacement.
Various technologies appropriate for manufacturing implants and tools are known in the art, for example, as described in Wohlers Report 2009, State of the Industry Annual Worldwide Progress Report on Additive Manufacturing, Wohlers Associates, 2009 (ISBN 0-9754429-5-3), available from the web www.wohlersassociates.com; Pham and Dimov, Rapid manufacturing, Springer-Verlag, 2001 (ISBN 1-85233-360-X); Grenda, Printing the Future, The 3D Printing and Rapid Prototyping Source Book, Castle Island Co., 2009; Virtual Prototyping & Bio Manufacturing in Medical Applications, Bidanda and Bartolo (Eds.), Springer, Dec. 17, 2007 (ISBN: 10: 0387334297; 13: 978-0387334295); Bio-Materials and Prototyping Applications in Medicine, Bártolo and Bidanda (Eds.), Springer, Dec. 10, 2007 (ISBN: 10: 0387476822; 13: 978-0387476827); Liou, Rapid Prototyping and Engineering Applications: A Toolbox for Prototype Development, CRC, Sep. 26, 2007 (ISBN: 10: 0849334098; 13: 978-0849334092); Advanced Manufacturing Technology for Medical Applications: Reverse Engineering, Software Conversion and Rapid Prototyping, Gibson (Ed.), Wiley, January 2006 (ISBN: 10: 0470016884; 13: 978-0470016886); and Branner et al., “Coupled Field Simulation in Additive Layer Manufacturing,” 3rd International Conference PMI, 2008 (10 pages).
Exemplary Techniques for Forming or Altering a Patient-Specific and/or Patient-Engineered Implant Component for a Patient's Anatomy
In the pursuit of patient-specific and/or patient-engineered implants, it would be extremely advantageous if one could employ 3-dimensional printing technology (also known as Solid Freeform Fabrication or “SFF”) to create solid, physical implant components from an electronic or computerized data file (e.g., a CAD file). At first limited to the use of photo-curable polymers to create relatively fragile objects, 3D printing techniques have evolved over the past decades to allow the creation of prototypes, mould masters and/or “models” that could be used in metal casting techniques (e.g., lost-wax casting or investment casting). More recently, 3D printing techniques such as Selective Laser Sintering (SLS) and Selective Laser Melting (SLM—also known as Direct Metal Laser Sintering—DMLS—or LaserCusing) have been developed and refined to allow the creation of durable metallic objects, and it has been proposed that such techniques may allow the creation of biocompatible metal objects that could themselves directly serve as implant components.
As with any manufacturing process, including traditional processes such as the casting and/or forging of metals, the various advantages of different metal 3D printing techniques typically are accompanied by some disadvantages inherent with each of the manufacturing techniques. For example, while SLS allows a range of metallic systems and polymeric material choices in the creation of the physical object, SLS parts typically (1) have a rough grainy and porous surface finish, (2) experience a relatively large shrink rate causing the part to warp, bow or curl, and (3) have a surface feature detail that is relatively coarse. While a wider variety of materials is available for use in the SLM process, the technique as currently refined also comes with some associated disadvantages, including (1) high temperature gradients resulting in a build-up of thermal stresses, (2) a rapid solidification, leading to the occurrence of segregation phenomena and the presence of non-equilibrium phases, (3) the stability, dimensions and behavior of the particle “melt pool” determines to a great extent the porosity and surface roughness, and (4) the object has a surface roughness created by the layer-wise building techniques (e.g., the “staircase effect”).
The steps of designing an implant component and/or guide tool, and associated methods of manufacturing such objects using additive material technologies such as SLM and SLS, as described herein, can include both configuring one or more features, measurements, and/or dimensions of the implant and/or guide tool (e.g., derived from patient-specific data from a particular patient and adapted for the particular patient), manufacturing and finishing the implant/tool. In certain embodiments, manufacturing can include making the implant component and/or guide tool from starting materials, for example, metals and/or polymers or other materials in solid (e.g., powders or blocks) or liquid form. In addition or alternatively, in certain embodiments, manufacturing can include altering (e.g., machining) an existing implant component and/or guide tool, for example, a standard blank implant component and/or guide tool or an existing implant component and/or guide tool (e.g., selected from a library), as well as post-manufacture machining and/or processing of an implant after manufacture by SLM techniques. The manufacturing techniques to making or altering an implant component and/or guide tool can include any techniques known in the art today and in the future. Such techniques include, but are not limited to additive as well as subtractive methods, i.e., methods that add material, for example to a standard blank, and methods that remove material, for example from a standard blank, as well as combinations thereof (i.e., using both additive and subtractive techniques on a single object). The design of an implant component and/or guide tool can include manufacturing, for example, using CAM software and additive, subtractive and/or casting manufacturing techniques as described herein.
In various embodiments, the design of an implant component and/or other manufactured object (e.g., a guide tool) may be altered or modified to accommodate advantages and/or limitations of a specific manufacturing process, such as SLM, which may result in differing designs for a single anatomical situation (e.g., for a single patient anatomy) based on differing manufacturing methods. The various design changes, which can (but not necessarily must) have varying degrees of impact on the ultimate performance and/or reliability of the implant, can be incorporated to accommodate a wide variety of considerations, including tolerancing and dimensioning limitations of specific manufacturing methodologies and/or equipment, design limitations and/or object feature (e.g., surface and/or subsurface feature) orientation and/or shape requirements, ease of object removal from manufacturing equipment and/or fixtures, ease of removing support surfaces or other ancillary artifacts from the manufacturing processes, improvements in manufacturing performance and/or manufacturability of multiple implants and/or implant components in a single machine “run” or batch, minimizing object and/or feature deformation and/or “warpage” during and subsequent to the manufacturing process, improving the repeatability and reliability of implant manufacturing processes and methods, and/or simplifying and/or improving the implant design to facilitate finishing and polishing of the object.
The production of parts using SLM has many difficulties. Many processing issues arise due to the use of a high power laser to fully liquefy material from a powder bed. High heat input often causes an increase in material vaporization and spatter generation during processing. Surface roughness is another SLM issue that is influenced by particle melting, melt pool stability and re-solidifying mechanisms. In addition, because the process involves the creation of localized melting and bonding of particles in a row, line by line, the possibility exists for “track instability” and/or “breaking up” of tracks associated with the formation of agglomerates and/or pores in the surface.
Various embodiments described herein include designs and methods to mitigate, reduce and/or eliminate structural and/or processing challenges and/or concerns posed by SLM manufacturing of implant components. In addition, various embodiments further include designs and methods that improve, maximize and/or take advantage of structural and/or processing benefits conferred by SLM manufacturing of implant components. In addition, various additional techniques, such as laser polishing or laser rescanning in parallel and/or perpendicular scanning directions (including remelting of previously formed surfaces and/or structures), hot isostatic processing (HIP) processing of manufactured implants, annealing and/or coating (e.g., titanium nitride coating and/or titanium aluminum nitride coating) are contemplated for use with the various embodiments disclosed herein.
In various embodiments, the SLM raw material comprises a CrCo powder having an average particle size of between 34 and 54 microns, although larger and/or smaller particles may used with varying degrees of utility (as well as the use of differing size particles in creating a single implant component). In various embodiments, the deposed particle layer may be approximately 60 microns thick, which, when melted, consolidated and cooled, can create a solid structural layer of approximately 20 microns thickness.
Some significant features of various embodiments described herein include various methods, techniques and/or processes to align, orient and/or otherwise position implants or other objects to be manufactured relative to a known “home” or “zero” location and orientation of the SLM manufacturing equipment or portions thereof (e.g., the laser source and/or scanning mechanism). Consistent orientation and location relative to a known position can facilitate the reliable and repeatable manufacturing of implant components in a single machine and/or across multiple machines, and can further assist with identification and/or alleviation of process and/or design defects discovered during or after the manufacturing process. Moreover, proper alignment and/or location of a manufactured object relative to the manufacturing machinery allows a designer and/or operator to predict and/or accommodate for various manufacturing advantages and/or disadvantages inherent in the chosen manufacturing processes.
In one embodiment, an electronic design file (such as a CAD file, for example) for a knee implant component (in this example, a “total knee” implant component for replacing femoral surfaces) can be loaded into SLM processing equipment or otherwise accessed to facilitate manufacture of the component by the SLM equipment. The CAD design file can include a wide variety of information about the component, including desired outer surfaces for the implant. In some embodiments, the implant design can include information regarding various surfaces and/or other features of the implant, one or more of which can be designated as “reference parameters” for use in aligning and/or positioning the design and/or object relative to the SLM equipment.
For example, in manufacturing a femoral component of a “total knee” implant, one embodiment (shown in
In various embodiments, the identification and employment of such datum in conjunction with SLM manufacturing equipment can ensure consistency throughout multiple “runs” of manufactured implants (in the same or different machines) and can significantly reduce time and/or effort (and possibly obviate a need for human intervention) required for “set up” of an individual SLM machine for creating a given implant design. Moreover, because various properties of the implant and its component material(s) can be dependent upon the direction and/or orientation of the implant feature(s) being created by the SLM equipment, due to a wide variety of factors, information regarding the proposed alignment of the object may be highly relevant to the implant design.
By choosing relative measures for alignment (e.g., bone-facing planar surfaces of the implant), various embodiments can define a repeatable alignment technique for the manufacture of patient specific implants of differing sizes and/or shapes via SLM techniques, which allows the designer to anticipate and/or accommodate various manufacturing considerations, limitations and/or advantages in designing and/or orienting the implant for manufacture.
Many additive manufacturing processes and 3D printing methods require and/or prefer the use of support structures during part build. In many cases, the geometry cannot stand on its own, or the material requires support during melt and/or curing. In addition, the use of support structures can anchor the manufactured object within the manufacturing equipment, preventing the object from uncontrolled movement and/or rotation/displacement during the manufacturing process, which could potentially ruin and/or degrade the quality of the part. While various developers have experimented with supportless SLM manufacturing techniques, including the use of eutectic system alloys (materials which solidify at sharp temperature points), such processes have not yet been successful in high melt-temperature materials, including most medical-grade metals.
While support structures may be necessary during the manufacture of implant components, the supports are generally removed after manufacture and prior to finishing of the implant. Various embodiments described herein include improvements and/or modifications to standard SLM anchoring and/or support structures to facilitate the separation of the implant from the SLM equipment and/or substrate, the removal of such structures from the implant itself, and the design and/or placement of such support structures to minimize their impact on part quality and/or performance as well as any effects on finishing of the implant or other part.
In various embodiments, the location of support structures and their respective attachment points can be positioned to avoid and/or minimize contact with specific portions of the implant, if possible. For example, the inner, bone-facing surfaces of a femoral implant component (including the inner surfaces of the “cement pockets” and/or bone ingrowth surfaces) are often structures that do not require significant “finishing” after manufacture (and/or the need for such finishing is not desired by the manufacturer). Where SLM support structures contact and/or extend outward of such component surfaces, their detachment and removal may necessitate additional processing and/or finishing of such surfaces, which may be difficult to perform (e.g., the surfaces may recessed and/or obstructed by other surfaces and/or structures) or simply involve additional, unnecessary expense. By avoiding support contact with such non-finished or minimally-finished surfaces, the time and expense associated with implant manufacture can be minimized.
In various embodiments, the location of support structures and their respective attachment points can be positioned to avoid and/or minimize contact with surfaces intended for implant articulating or other surfaces where surface dimensionality and/or shape are critical or important features of the implant. For example, the outer, joint facing surfaces of a femoral implant component (especially those directly opposite to the inner, bone-facing surfaces) typically form articulating surfaces that interact with polymer and/or metal surfaces of opposing implant components. Where SLM support structures contact and/or extend outward of such articulating surfaces, their detachment and removal may necessitate additional processing and/or finishing of such surfaces, especially where the presence of the support structures have increased the local porosity of the material. Moreover, removal of the support structures and finishing of the articulating surfaces may necessitate the removal and polishing off of significantly more implant material, potentially altering the carefully designed shape of the articulating surface as well as involving additional, unnecessary expense. By avoiding support contact with such non-finished surfaces, the time and expense associated with implant manufacture can be minimized.
In various embodiments, the support structures and their respective attachment points can be positioned adjacent to peripheral edges of the implant, as well as between adjacent peripheral edges of the medial and lateral condylar portions of the implant. In this manner, the effects of the support structures on critical aspects of the implant (e.g., intended articulating surfaces and/or bone-facing surfaces), and the amount of effort required to remove and finish surfaces associated with support structures, can be minimized. Moreover, in various embodiments, support structures may not be used (or may be used sparingly) (1) in confined areas (e.g., deep within the intercondylar notch) or (2) in areas having surface features that render removal of the support structures and subsequent finishing difficult or time consuming (e.g., along highly curved surfaces or within recessed areas).
In various embodiments, the support structures can incorporate various design features to simplify their removal from the manufactured implant. For example,
The support structure arrangement of
In various embodiments, the manufactured object may be supported a desired distance above the substrate or platform, to allow sufficient clearance for a wide variety of cutting and/or removal tools. For example, where a pair of “tin-ships” or other similar cutting devices (e.g., metal shears, dikes, pliers, etc.) are used to sever the support structure between a femoral implant component and the substrate, it may be desirous to ensure that a spacing of 1 cm or more of clearance exists between the substrate and the lowest point of the implant.
In certain embodiments, various design features of the implant and/or its supporting structures may be altered, modified or particularized for a desired manufacturing method. For example, in the case of a femoral implant component manufactured using SLM manufacturing techniques, it may be desirous to modify the peg or post designs to include regular-shaped pegs with few voids or inclusions therein (e.g., cross-shaped, cylindrical, triangular, rectangular and/or other regular geometric peg shapes). Alternatively, it may be desirous to incorporate complex peg designs that include varying quantities of voids and/or inclusions for a wide variety of reasons, including to act as bone ingrowth and/or bone cement retention structures and/or surfaces.
In a similar manner, the various manufacturing techniques described herein, such as SLS or SLM manufacturing, may be utilized to create complex geometries and/or surfaces that can be employed for a variety of functions, which could include the creation of textured and/or porous-walled cement pockets and/or bony ingrowth surfaces, for securing the implant to the patient's underlying bone. Various shapes could include defined micro-cavities and/or micro-protrusions on the implant surface.
In various embodiments, the pegs may be designed to obviate the need for manufacturing support structures, such as where the pegs are conically shaped or formed in similar shapes. If accuracy, shape and/or dimensions of the pegs are not a critical factor, or where post manufacturing machining of the pegs is performed (or where the pegs are installed in the post-manufacturing phase, such as by drilling and tapping the implant and installing threaded pegs), the use of support structures for the pegs may not be mandated and/or necessary.
In various embodiments, the design of a given implant component and/or various features therein can be further assessed and/or modified by including FEA modeling and/analysis, either alone or in combination with information relating to the specific manufacturing method chosen for creating the implant. For example, the creation of an implant using SLM manufacturing methods may produce an implant having differing density, porosity, durability, fatigue strength and/or other material properties than those of an implant created through traditional casting techniques. A finite element analysis (FEA) of an SLM implant and/or intended implant design may identify areas of the implant/design prone to increased and/or excessive loads, which may induce the designer to modify the design to better accommodate the anticipated loading (e.g., increase the local or global implant thickness and/or alter implant geometry or location of planar surfaces).
In various embodiments, the design and/or orientation of an implant may be modified and/or altered due to various features of the manufacturing method(s). For example, in SLM manufacturing, the mechanical properties in SLM parts can be anticipated to be anisotropic mainly due to the fact that part build-up is conducted with many melted tracks (or vectors) and layers melted onto each other. Solidification microstructure of SLM parts generally determines the strength properties, and the solidification microstructure essentially depends on the local solidification. Moreover, notable thermal stresses may exist in SLM parts because of the large temperature gradients caused by the rapid cooling during the SLM processing. In addition, SLM parts may have a greater level of elasticity within an individual layer than between layers, which may result in crack propagation and/or cleavage at layer contacts.
Various embodiments disclosed herein include the modification of implant designs, manufacturing orientations and/or manufacturing methods to accommodate mechanical properties of implant components manufactured using SLM methodologies. For example, in designing an implant component, and then orienting that component for manufacture using SLM, it may be desirous to minimize the potential for crack propagation and/or cleavage inducing a complete or catastrophic failure of the implant.
In various embodiments, the use of multiple alignments and/or orientations to create a single implant component is contemplated. For example, where FEA analysis of a part design and/or orientation identifies multiple regions of potential weakness, and redesign/reorientation of the design prior to SLM manufacture does not sufficiently alleviate strength and/or durability concerns, it may be desirous to reposition and/or reorient the object at one or more times part-way through the manufacturing process (e.g., pausing the layer deposition and laser melting process, moving/rotating the partly finished implant in some manner, and then continuing the layer deposition and laser melting process to complete the implant manufacture) to address localized fracture potential.
In various embodiments, the design and manufacture of an implant component using SLM manufacturing methods may include additional processing and/or finishing steps which are not mandated, required and/or are necessary to prepare the part for use and implantation when the part is manufactured using conventional methods (e.g., casting, wrought and/or machining, etc.). For example, if the surface porosity of an implant created via SLM manufacturing is unacceptable from a given application, it may be necessary to remove and/or fill the pores using a variety of additional manufacturing and/or finishing steps, which can include coating, filling, remelting, HIP-ping, annealing and/or machining, as well as potentially adding additional material to the implant surface to thereby allow for additional polishing and/or grinding to remove the undesired surface features. Various embodiments described herein include the use of such additional processes to “finish” a SLM part, including the use of such processes on a localize portion of the implant (e.g., performed only on the articulating surfaces or other implant surfaces having undesirable features or characteristics).
In various embodiments, a wide variety of standard finishing techniques used with cast or wrought implants, such as polishing, drag finishing, machining and/or bead/grit blasting, may be used to finish SLM parts as well, with varying results.
Implant components generated by different techniques can be assessed and compared for their accuracy of shape relative to the intended shape design, for their mechanical strength, and for other factors. In this way, different manufacturing techniques can supply another consideration for achieving an implant component design with one or more target features. For example, if accuracy of shape relative to the intended shape design is critical to a particular patient's implant component design, then the manufacturing technique supplying the most accurate shape can be selected. If a minimum implant thickness is critical to a particular patient's implant component design, then the manufacturing technique supplying the highest mechanical strength and therefore allowing the most minimal implant component thickness, can be selected. Branner et al. describe a method a method for the design and optimization of additive layer manufacturing through a numerical coupled-field simulation, based on the finite element analysis (FEA). Branner's method can be used for assessing and comparing product mechanical strength generated by different additive layer manufacturing techniques, for example, SLS, SLM, DMLS, and LC.
In certain embodiments, an implant can include components and/or implant component parts produced via various methods. For example, in certain embodiments for a knee implant, the knee implant can include a metal femoral implant component produced by casting or by an additive manufacturing technique and having a patient-specific femoral intercondylar distance; a tibial component cut from a blank and machined to be patient-specific for the perimeter of the patient's cut tibia; and a tibial insert having a standard lock and a top surface that is patient-specific for at least the patient's intercondylar distance between the tibial insert dishes to accommodate the patient-specific femoral intercondylar distance of the femoral implant.
As another example, in certain embodiments a knee implant can include a metal femoral implant component produced by casting or by an additive manufacturing technique that is patient-specific with respect to a particular patient's M-L dimension and standard with respect to the patient's femoral intercondylar distance; a tibial component cut from a blank and machined to be patient-specific for the perimeter of the patient's cut tibia; and a tibial insert having a standard lock and a top surface that includes a standard intercondylar distance between the tibial insert dishes to accommodate the standard femoral intercondylar distance of the femoral implant.
In a manner similar to the various embodiments described herein in connection with femoral implant components, a tibial tray component can be machined, molded, casted, manufactured through additive techniques such as laser sintering, selective laser melting or electron beam melting or otherwise constructed out of a metal or metal alloy such as cobalt chromium. Similarly, the insert component may be machined, molded, manufactured through rapid prototyping or additive techniques or otherwise constructed out of a plastic polymer such as ultra high molecular weight polyethylene. Other known materials, such as ceramics including ceramic coating, may be used as well, for one or both components, or in combination with the metal, metal alloy and polymer described above. It should be appreciated by those of skill in the art that an implant may be constructed as one piece out of any of the above, or other, materials, or in multiple pieces out of a combination of materials. For example, a tray component constructed of a polymer with a two-piece insert component constructed one piece out of a metal alloy and the other piece constructed out of ceramic.
While the various embodiments and teachings therein are described with regards to a knee joint, the various embodiments described herein can be applied to various other joints or joint surfaces in the body, e.g., a knee, hip, ankle, foot, toe, shoulder, elbow, wrist, hand, and a spine or spinal joints. For example, the material properties of a hip stem manufactured using SLM techniques may similar be dependent upon the orientation and/or alignment of the design during manufacture.
Any material known in the art can be used for any of the implant systems and component described in the foregoing embodiments, for example including, but not limited to metal, metal alloys, combinations of metals, plastic, polyethylene, cross-linked polyethylene's or polymers or plastics, pyrolytic carbon, nanotubes and carbons, as well as biologic materials.
Any fixation techniques and combinations thereof known in the art can be used for any of the implant systems and component described in the foregoing embodiments, for example including, but not limited to cementing techniques, porous coating of at least portions of an implant component, press fit techniques of at least a portion of an implant, ingrowth techniques, etc.
The entire disclosure of each of the publications, patent documents, and other references referred to herein is incorporated herein by reference in its entirety for all purposes to the same extent as if each individual source were individually denoted as being incorporated by reference.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting on the invention described herein. The true scope of the invention is thus indicated by the descriptions contained herein, as well as all changes that come within the meaning and ranges of equivalency thereof.
This application claims the benefit of U.S. Provisional Application Ser. No. 61/623,776, entitled “Devices and Methods for Additive Manufacturing of Implant Components” and filed Apr. 13, 2012, the disclosure of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US13/36505 | 4/13/2013 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61623776 | Apr 2012 | US |
