Augments and methods for implanting hip prostheses

A method of securing an orthopedic hip prosthesis to an acetabulum of a living being. The prosthesis can be a shell or a cup, and the surgery can be a total hip arthroplasty such as a revision total hip arthroplasty. In some examples the method can include placing an augment at a bone surface of the acetabulum, applying a layer of fixation material over the bone surface in an amount sufficient to cover the augment, and then implanting the prosthesis over the layer of fixation material to secure the prosthesis to the layer of fixation material. In various aspects of the method, the augment can be an anchor or a spacer.

TECHNICAL FIELD

This document pertains generally, but not by way of limitation, to augments and methods for implanting orthopedic devices. The augments can include anchors and spacers to be used with acetabular implants for total hip arthroplasty, including revision total hip arthroplasty.

BACKGROUND

A total hip arthroplasty (THA) procedure can be performed to repair a diseased or damaged hip joint and replace it with a hip prosthesis. Sometimes, as with any other mechanical device, a total hip replacement can be subject to various forms of mechanical or biological issues. When issues occur, a reoperation of the hip replacement can be necessary to resolve the issues. Such a reoperation of a THA is called a revision THA. This is usually done several years after the original implantation and is more common in patients who had the initial THA performed at a young age and the patient chose to have a very active physical lifestyle.

One of the challenges of a revision THA is how to securely implant the hip prosthesis, and in particular, how to securely implant an acetabular cup or shell of the prosthesis into the remaining bone of the patient, especially in the presence of poor bone quality or bone loss. Another challenge is achieving a uniform fixation material thickness (e.g., bone cement mantle thickness) between the prosthesis and the bone.

DETAILED DESCRIPTION

As discussed above, one of the challenges of a total hip arthroplasty (THA), and especially in a revision THA, is how to securely implant the hip prosthesis. It can be difficult to secure an acetabular revision shell of the prosthesis into the remaining bone of the patient, especially in the presence of poor bone quality or bone loss. A second related challenge is how to achieve a uniform thickness of a fixation material (e.g., cement mantle thickness) between the prosthesis and the bone. Conventional methods that rely on the presence of substantially good bone may not be able to provide as strong of an attachment as desired when the patient has poor bone quality or bone loss. The present disclosure addresses these challenges through the use of augments in the form of anchors and spacers, and methods of using these augments to implant a prosthesis.

To improve the quality of the implantation of the prosthesis to the bone when the patient has poor bone quality or bone loss, the present disclosure includes a method of recreating the acetabulum. Recreating the acetabulum is accomplished by securing augments in the form of anchors to good bone, and then applying a layer of fixation material (e.g., a bed of cement) over the anchors and behind a shell or cup of the prosthesis that is physiologically oriented in the acetabulum. This method of recreating the acetabulum can eliminate the need for an expensive revision shell and permit a cup to be directly implanted over the layer of fixation material.

To solve the second challenge of achieving a target fixation material thickness, some conventional acetabular shells incorporate integral spacers therein. However, this limits the surgeon to using the fixation material thickness dictated by the integral spacers. The integral spacers do not provide the surgeon with the option to tailor the fixation material thickness between the bone and the shell of the prosthesis. Variables including patient anatomy, quality of the bone, bone loss and surgeon preferences may result in the surgeon wanting to adjust the fixation material thickness irrespective of the particular shell being used, or to control or adjust the thickness in a uniform or a variable manner across the acetabulum. In shells that incorporate integral spacers, adjusting the thickness in any manner is difficult, if not impossible.

To improve the fixation material thickness control and provide adjustability to the surgeon, the present disclosure includes a method of using augments in the form of spacers that allow the surgeon to adjust and control (e.g., variably or uniformly) the thickness of the fixation material that helps secure the prosthesis to the bone. In general, achieving a target thickness of the fixation material is accomplished by applying a layer of fixation material to the acetabulum, inserting one or more spacers into the cement, and inserting a shell or cup of the prosthesis into the acetabulum until it bottoms out on the spacers.

The anchors, spacers and methods described herein help to correctly orient a shell or a cup in an acetabulum, simplify revision surgeries and reduce operating time. The anchors, spacers and methods can also allow cemented cups, including poly, ceramic and metal dual mobility cups, to be directly implanted in the acetabulum without the shell. This can eliminate the need for expensive acetabular shells altogether. The various anchors, spacers and methods described herein can be used alone or together.

FIG. 1is a perspective view of a hip bone1including illustrative augments (e.g.,100,200) arranged at am implant site10proximate a portion of the hip bone1, in accordance with at least one example. To solve the challenge of securely implanting a hip prosthesis in the situation where the patient suffers from poor bone quality or bone loss, one or more augments, such as an anchor100can be secured to the bone1with a fastener900.FIG. 1shows three such anchors100, although any number of anchors100may be provided, including a single anchor100, as will be described below for clarity.

As shown inFIG. 1, the anchor100can include a body having a first surface110and a second surface120opposite and spaced apart from the first surface110. A third surface140can extend from the first surface110to the second surface120(as shown in the cross-section ofFIG. 2C). The anchor100can also include an opening130(FIG. 2A) extending from the first surface110to the second surface120. The opening130can be sized and shaped to accept insertion of a fastener900through the opening130so that the fastener900can be secured to the hip bone1(e.g., the acetabulum2and surrounding bone). All or a portion of the anchor100can be formed of a layer of porous material that promotes boney ingrowth. While the anchor100inFIG. 1is depicted as being generally planar or cuboid shaped, the anchor100can take on other forms and features, including but not limited to the example anchors ofFIGS. 4, 5A, 5B, 6A, 6B, 7A, 7B, 8A and 8B, which will be described in further detail below. Additional details of the anchor100and other anchors will be described in further detail following a description of illustrative methods of using the anchor100.

Also with reference toFIG. 1, to solve the second challenge of controlling fixation material thickness, one or more augments in the form of a spacer200can be provided. The spacer200can be a spherical spacer200(e.g., a substantially spherical spacer) that is inserted in a layer of fixation material50to control a thickness52(FIG. 2E).FIG. 1shows three such spacers200, although any number of spacers200may be provided, including a single spacer200.

While the anchors100and the spacers200are shown used together inFIG. 1and an illustrative method ofFIGS. 2A-2E, the anchors and spacers can also be used independent of one another. For example, one or more anchors100can be used separately or together with one or more spacers200, in any number and combination.

Additional details of the spacer200will be described in further detail following a description of illustrative methods.

An illustrative method300of securing a shell or cup of an orthopedic hip prosthesis60to a hip bone1using augments such as the anchors100and spacers200shown inFIG. 1, will be described with reference toFIGS. 2A-2EandFIG. 3.FIGS. 2A-2Eshow cross-sectional views, as taken along line A-A′ inFIG. 1, of steps of the method300.FIG. 3includes an illustrative flow chart outlining the steps of the method300depicted inFIGS. 2A-2E, in accordance with at least one example.

As shown inFIG. 2A, the method300can include placing an augment such as anchor100at a bone1. The bone may include a surface of an acetabulum2. Step310can include the surgeon identifying and selecting a target bone location3for placing the anchor100by determining what portion of the bone1is strong enough to support the prosthesis60and the functional loads it will incur. Step310may include identifying good bone that will serve as the target bone location3. Identifying good bone may be done by visual identification during surgery or by an analysis of imaging data obtained on the patient. As shown inFIG. 2B, step320can include placing the anchor100at the target bone location3. Step330can also include inserting a fastener900through an opening130in the anchor100and attaching the fastener900to the good bone at the target bone location3in order to secure the anchor100to the bone1. In some examples, this area of good bone that makes up the target bone location3can be adjacent to areas of poor or missing bone.

As shown inFIG. 2C, once the anchor100is secured to the target bone location3, step340can include the surgeon applying a layer of fixation material50, such as a bone cement, over the anchor100and the bone surface in an amount sufficient to cover the anchor100. In some examples, the exposed surface area of the anchor100that is not attached to the bone1is covered (e.g., completely covered, substantially completely covered) by the fixation material50. A sufficient amount of fixation material can be described as a layer of fixation material50that is at least as thick as the thickness of the anchor100. In some preferred examples, a sufficient amount of fixation material can be described as layer of fixation material50that is thicker than a thickness of the anchor100. The thickness of the anchor100can be described as the distance from the first surface110of the anchor100to a second surface120of the anchor100. In some examples this may be the maximum thickness of the anchor100. In some examples the layer of fixation material50forms a surrogate bone surface for the target bone location3and/or bone surrounding the target bone location3. This surrogate bone surface can provide a stronger attachment of the prosthesis60to the bone1than if the prosthesis60was attached to the bone1alone.

Steps310,320,330and340can be repeated as desired to secure additional anchors100to the bone1and cover the anchors100with the fixation material52. Once the desired number of anchors100are attached and sufficiently secured to the bone1and the fixation material50is layered over the anchor100and the bone1, the prosthesis60can be implanted over the fixation material50(e.g., skip step350and go to step360).

Alternatively, if it is desired to control a target thickness52of the fixation material50, step350can include placing another type of augment, such as a spacer, at the bone1surface to facilitate controlling a target thickness52of the fixation material50, before implanting the prosthesis60over the fixation material50.

As shown inFIG. 2D, the augment used in step350can be one or more of the substantially spherical spacers200ofFIG. 1. In some examples, a single spacer200can be used, but as shown in the example ofFIG. 1, three spacers200can be provided in a spaced apart relationship to help in properly orienting the shell or cup of the prosthesis60to the acetabulum2. This spaced apart relationship can be a triangular relationship as shown. The spacers200are not limited to being used as a set of 3 spacers. Other numbers and arrangements of spacers200can also be used, such as one or more, a plurality, or three or more.

As shown inFIG. 2D, step350can include inserting the one or more substantially spherical spacers200into the layer of fixation material50. In at least one example, the layer of fixation material50should be at least as thick as, or thicker than, the diameter of the spacers200. The spacers200provide control or guidance for achieving a target thickness (e.g.,52,FIG. 2E) of the fixation material50. Step360can include implanting the orthopedic prosthesis60into the fixation material50by orienting the shell or cup of the prosthesis60at the implantation location (e.g., acetabulum2) and applying a force until the prosthesis60bottoms out on the spacers200(FIG. 2E). In other words, when the prosthesis60is fully seated, the spacers200should be contacting both the bone1surface and the prosthesis60surface, and the gap (e.g.,52) between the bone1surface and the prosthesis60surface can be occupied by the fixation material50(e.g., substantially or completely filled with the fixation material). This is beneficial because the surgeon is able to determine when the prosthesis60is fully seated because the prosthesis60will not move any further. The surgeon can also be able to visually determine that enough fixation material has been provided by the movement of excess fixation material50being secreted out of the gap between the acetabulum2and the prosthesis60. In other words, the surgeon is able to determine that the gap is filled with fixation material. Furthermore, over-seating of the prosthesis, where the surgeon displaces an excessive amount of fixation material50, which can result in a smaller fixation material50thickness52than was intended, can also be prevented. The illustrative method300reduces challenges in conventional methods where there is no spacer and setting the fixation material50thickness52is a blind operation for the surgeon. Method300also provides more customization options for the surgeon to tailor the fixation material50thickness52.

In some examples of the method300, the surgeon may attempt to achieve a uniform or substantially uniform target thickness52of the fixation material50. In other examples, the surgeon may intentionally attempt to achieve a variable target thickness52. In some situations, the surgeon may simply not be able to achieve a uniform target thickness52due to variations in the bone1surface or the prosthesis60. This can lead the surgeon to create a variable target thickness52. In some examples, the target thickness52at or around a particular bone location that the spacer200is placed, can correspond to a diameter (e.g.,210a,FIG. 10) of the spacer200. Controlling or adjusting the target thickness52(e.g.,FIG. 2E), can include providing guidance, via the spacers200, in an attempt to achieve the target thickness52of the fixation material50at the spacers200, around the spacers, or across the acetabulum2(FIG. 1).

In some examples of the method300, the surgeon may intentionally try to achieve a variable target thickness52by using different sized spacers in different areas of the implant site. For example, as shown in the example ofFIG. 4, which will be described in further detail later, different sized spacers (e.g.,200a,200b) can include spacers of different diameters or volumes. In an example where a plurality of spacers are used, a first spacer200aof the plurality of spacers can include a first diameter, and a second spacer200bof the plurality of spacers can include a second diameter that is different from the first diameter. One reason a surgeon may use different sized spacers in different locations is to be able to use the fixation material50to fill in some of the gap (e.g.,FIG. 2E, target thickness52) between the bone surface1and the prosthesis60where there is bone loss. The methods and spacers200described herein can facilitate a more anatomically correct placement of the prosthesis60in relation to the acetabulum2and a more desirable fixation material50thickness52.

As described herein, substantially spherical can include spherical-type shapes such as a polyhedron having a substantially spherical form, including, but not limited to a dodecahedron, a spherical polyhedron, and other spherical type shapes. Irregular spacers having substantially spherical type base shapes can also be used.

The spacer200can be formed of biocompatible materials such as bone cement, however any suitable biocompatible material can be used to form the spacer200such as metals, polymers, ceramics, or the like.

Method300can be described as recreating the acetabulum2. In some examples, recreating the acetabulum is primarily accomplished by the fixation material50surface that adjoins the prosthesis, as opposed to the anchor100serving as the primary component that recreates the acetabulum. For example, the anchor100can serve primarily as an anchor for the layer of fixation material50, while the fixation material50fills in voids and provides the new acetabular surface that supports the prosthesis60.

In addition to the illustrative example ofFIG. 1previously described,FIGS. 4, 5A, 5B, 6A, 6B, 7A, 7B, 8A and 8Balso show example anchors (400a,400b,400c,500,600,700and800). The features of any of the anchors described herein can be used in any combination, and features can be added or eliminated.

FIG. 4is a perspective view of another example of illustrative augments that are arranged at an implant site40of a hip bone1, in accordance with at least one example. The anchors400a,400band400cshown inFIG. 4can be similar to the anchors100shown inFIG. 1in many respects. However, while the anchors100shown in the example ofFIG. 1are generally planar and are depicted with a single hole130, anchors400a,400band400ccan have a curved shape and can have a plurality of openings430. Anchors400a,400band400ccan include a body that is shaped to approximate a surface of an acetabulum2, or is conformable to approximate a portion of a surface of an acetabulum2.

In some examples, the anchor400a,400band400ccan be tailored to conform to and cover at least a portion of an acetabulum2of a particular living being. This can be accomplished using imaging data obtained for the particular living being, and by ordering, selecting or manufacturing an anchor tailored to the particular living being. Manufacturing can be done, for example, by 3D printing. The shape of the anchor400a,400b,400ccould also be tailored to the specific living being by manipulating a standard sized anchor400by hand or machine, or by selecting from a range of standard sizes, or an average or other mathematical value of a range of sizes. The shape of the anchor can also be formed by taking a sheet of suitable material and trimming or breaking off portions of the material to create the appropriate shape for the application. The material that is trimmed can have openings already extending there through for receiving the fasteners. The material can be trimmed based on the application and the anatomy.

FIGS. 5A and 5Bare top and side views of another illustrative augment in the form of an anchor500, in accordance with at least one example. Like the anchors400ofFIG. 4, the anchor500shown inFIGS. 5A and 5Bcan also be similar to the anchors100ofFIG. 1in many respects.

The anchor500can include a body having a first surface510and a second surface520opposite and spaced apart from the first surface510(FIG. 5B). The anchor500acan also include an opening530extending from the first surface510to the second surface520. The opening530can be sized and shaped to accept insertion of a fastener900(FIG. 9) through the opening530so that the fastener900can be secured to the bone1. The fastener900can be any fastener, including the example fasteners900a,900band900cwhich will be shown and described with reference toFIG. 9.

All or a portion of the anchor500, and any of the other anchors described herein can be formed of a layer of porous material that promotes boney ingrowth. In some examples, the anchor500(or any other anchor) can be formed entirely of a porous material that promotes bone ingrowth. In some examples, both the first surface510and the second surface520can include the porous material that supports boney ingrowth. In other examples, only one of the first and second surfaces510,520include the porous material that supports boney ingrowth.

In some examples, instead of the anchor being entirely formed of the porous material that promotes boney ingrowth, the anchor500can be formed only partially of a porous material that promotes boney ingrowth. For example, the anchor500could be formed of a composite of layers, where one of the layers is a solid layer and the porous material is located adjacent to the solid layer on one or more sides. In some examples, the anchor500can be formed of the same porous material but with different levels of porosity in different regions of the anchor500, such as a high porosity at the second surface520and a low porosity at the first surface510. In some examples, there can be a porosity gradient where the porosity is higher at the second surface520and decreases towards the first surface510, or vice-versa.

In some examples, the anchor500can be formed having a first surface510that includes gripping formations512to promote adhesion of the first surface510to a fixation material50(e.g.,50,FIG. 2E), while the second surface520includes the porous material that promotes boney ingrowth for improved attachment to the bone1. In some examples including examples that incorporate the gripping formation512, the first surface510can be less porous than the second surface520.

As shown in the example ofFIGS. 5A and 5B, the anchor500can include a first portion560having a first opening530and a second portion562including a second opening532. The first and second openings530,532can extend from the first surface510to the second surface520. In the present example, where there is more than one opening530,532,534in the anchor500, step330of the previously described method300(FIG. 3) can further include inserting a second fastener900(e.g.,FIG. 9) through the second opening532, and attaching the second fastener900to the bone1at a second target bone location to secure the second portion562of the anchor500to the bone1. An example of the first and second target bone locations can be understood by reference to anchor400cinFIG. 4where a plurality of fasteners900can attach the anchor400cto the bone1.

Also shown in the example ofFIG. 5, the anchor500can further include one or more bendable hinge portions550, such as located between a first portion560and a second portion562, or between the second portion562and a third portion564. Likewise, the method300can include bending the anchor500at one of the hinge portions550and attaching two of the portions560,562,564to multiple target bone locations. In some examples, the hinge portion550can be located between the first portion560and the second portion562, or between the opening530and the second opening532. Any number of portions can be provided and the portions can be provided in any shape or arrangement to facilitate anchoring to an acetabulum.

Although the anchor500is shown as a rectangular anchor extending in a single direction, the anchor500can be formed in an L-shape or even an irregular shape. The hinge portions550do not necessarily need to be parallel to one another as shown in the example. The anchor500can be formed in complex shapes to match the anatomy of an acetabulum. For example, instead of having generally square first, second and third portions560,562,564separated by parallel hinge portion550, the anchor500could have triangular or other shaped first, second and third portions560,562,564and non-parallel hinge portions550, or any combination thereof.

FIGS. 6A, 6B, 7A, 7B, 8A and 8Bshow additional embodiments of anchors having a variety of characteristics that can be used in combination or alone with one another, or with any other embodiment.

FIGS. 6A and 6Bshow an anchor600similar to the example ofFIGS. 5A and 5B.FIGS. 6A and 6Bshow an illustrative example of hinge portions650in the form of living hinges. A general thickness of anchor600can be described as a distance from the first surface610to the second surface620, with opening630extending therethrough to accept one or more fasteners900(e.g., fasteners shown inFIG. 9). The thickness at the hinge portions650can be described as a distance extending from a first hinge surface610ato a second hinge surface620a. The thickness of the anchor600at the hinge portion650can be less than the thickness of the anchor600in other parts of the anchor600. In some examples, instead of a difference in thickness, or in addition to a difference in thickness, the material at the hinge portions650may include different material characteristics. For example, the hinge portions650may be more bendable, ductile, or more susceptible to bending than other portions of the anchor600.

FIGS. 7A and 7Bshow an example of a curved disk-shaped anchor700having one or more openings730extending through a body from a first surface710to a second surface720. The openings730can be adapted to accept one or more fasteners (e.g., fasteners900shown inFIG. 9). The first and/or second surfaces710,720of anchor700can be curved to have a consistent radius, or can have a varied curved surfaces to match with the shape of a particular location on a bone or prosthesis.

FIGS. 8A and 8Bshow an example of an anchor800that has a planar disk-shaped body having one or more openings830extending through the body from a first surface810to a second surface820to accept one or more fasteners (e.g., fasteners900shown inFIG. 9). The second surface820of anchor800can include one or more spikes834(e.g., protrusions) that can engage with bone when implanted to enhance fixation to the bone1. The spikes834can be of various shapes, sizes and lengths. Conical shaped spikes are shown, but any suitable shape can be provided, including but not limited to: columnar spikes having a blunt or pointed tip, and pyramidal spikes. In some examples, the body and/or the spikes834of anchor800can be formed of a porous material to promote boney ingrowth. In some examples, the body can include the porous material to promote boney ingrowth, while the spikes834are formed of a solid material.

FIG. 9is a side view of illustrative anchors in the form of fasteners900a,900band900cthat can be used alone or together with any of the anchors100,400a,400b,400c,500,600,700and800(FIGS. 1, 4, 5A, 5B, 6A, 6B, 7A, 7B and 8) to anchor a prosthesis to a bone, in accordance with at least one example.

The fasteners900a,900band900ccan be formed to include at least a section that has a porous material to promote boney ingrowth. For example, the porous material can be included anywhere along the elongate body910of the fastener900that extends between a tip920and a head930of the fastener900. In some examples the tip920and/or head930can include less porous, or solid sections. For example, a solid portion932can be useful for maintaining integrity of the fastener900during insertion. In some examples, a solid head930can be useful for attachment to fixation material50. Various features of the fastener900can include threads922or buttress formations924. The threads922and buttress formation924can act as gripping formations and facilitate better attachment to the bone, and/or better engagement with the fixation material50(e.g.,FIG. 2E) covering the fasteners900.

Any of the fasteners900a,900b,900cdescribed inFIG. 9can be used with the method300ofFIG. 3. The fastener can be inserted until it is flush with the anchor100, or the fastener can be inserted such that it is left proud of the anchor100to provide additional engagement with the fixation material50(FIG. 2E). The fasteners900a,900b,900cofFIG. 9can also be used alone (e.g., omitting the anchor100as shown inFIG. 2E). If the fasteners900a,900b,900care used alone and as the only anchor, they can be left proud of the bone1surface so that when the layer of fixation material50(e.g., step340) is applied over the fastener900and the bone1, a greater surface area of the fastener is engaged with the fixation material50to create a surrogate bone surface for the prosthesis60to be secured to.

To facilitate boney ingrowth, any of the anchors (100,400a,400b,400c,500,600,700and800) ofFIGS. 1, 4, 5A, 5B, 6A, 6B, 7A, 7B, 8A and 8B, and the fastener900ofFIG. 9, can be formed of a three-dimensional structure that supports boney ingrowth. For example, a highly porous, three-dimensional metallic structure can be provided that incorporates one or more of a variety of biocompatible metals such as but not limited to titanium, a titanium alloy, cobalt chromium, cobalt chromium molybdenum, tantalum, a tantalum alloy, niobium, or alloys of tantalum and niobium with one another or with other metals. Such structures are particularly suited for contacting bone and/or soft tissue, and in this regard, can be useful as bone substitutes and other implants and implant components that are receptive to cell and tissue ingrowth, for example, by allowing boney tissue or other tissue to grow into the porous structure over time to enhance fixation (e.g., osseointegration) between the structure and surrounding bodily structures. According to certain examples of the present disclosure, an open porous metal structure, or a portion thereof, can have a bulk porosity as low as 55%, 65%, or 75% or as high as 80%, 85%, or 90%, or within any range defined between any pair of the foregoing values, and in this regard, such structures can provide lightweight, yet strong porous implants. Certain porous metal structures, despite having such high porosities, are capable of withstanding extreme mechanical loads at the time of implantation and over long periods of time, for example, where a highly porous, three-dimensional metallic structure is forcefully impacted and press fit into a bone, by itself or connected to another implant, and maintains its shape during impaction and following many months or years of service in the body. Such structures can be manufactured according to any suitable technique or process. An example of an open porous metal structure is produced using Trabecular Metal™ Technology available from Zimmer, Inc., of Warsaw, Ind. Trabecular Metal™ is a trademark of Zimmer, Inc. Such a material can be formed from a reticulated vitreous carbon foam substrate which is infiltrated and coated with a biocompatible metal, such as tantalum, by a chemical vapor deposition (“CVD”) process in the manner disclosed in detail in U.S. Pat. No. 5,282,861 and in Levine, B. R., et al., “Experimental and Clinical Performance of Porous Tantalum in Orthopedic Surgery”, Biomaterials 27 (2006) 4671-4681, the disclosures of which are expressly incorporated herein by reference.

In some instances, a highly porous, three-dimensional metallic structure will be fabricated using a selective laser sintering (SLS) or other additive manufacturing-type process such as direct metal laser sintering or electron beam melting. In one example, a three-dimensional porous article is produced in layer-wise fashion from a laser-fusible powder, e.g., a single-component metal powder, which is deposited one layer at a time. The powder is fused, remelted or sintered, by the application of laser energy that is directed to portions of the powder layer corresponding to a cross section of the article. After the fusing of the powder in each layer, an additional layer of powder is deposited, and a further fusing step is carried out, with fused portions or lateral layers fusing so as to fuse portions of previous laid layers until a three-dimensional article is complete. In certain examples, a laser selectively fuses powdered material by scanning cross-sections generated from a 3-D digital description of the article, e.g., from a CAD file or scan data, on the surface of a powder bed. Complex geometries can be created using such techniques, and in some instances, net shape and near net shape implants are constructed. In some examples, a non-porous or essentially non-porous base substrate will provide a foundation upon which a three-dimensional porous structure will be built and fused thereto using a selective laser sintering (SLS) or other additive manufacturing-type process. Such substrates can incorporate one or more of a variety of biocompatible metals such as any of those disclosed herein.

Generally, a highly porous, three-dimensional metallic structure will include a large plurality of ligaments that define open voids (e.g., pores) or channels between the ligaments. The open spaces between the ligaments form a matrix of continuous channels having few or no dead ends, such that growth of soft tissue and/or bone through the open porous metal is substantially uninhibited. According to some aspects of the present disclosure, exterior surfaces of an open porous metal structure can feature terminating ends of the above-described ligaments. Such terminating ends can be referred to as struts, and they can generate a high coefficient of friction along an exposed porous metal surface. Such features can impart an enhanced affixation ability to an exposed porous metal surface for adhering to bone and soft tissue. Also, when such highly porous metal structures are coupled to an underlying substrate, a small percentage of the substrate can be in direct contact with the ligaments of the highly porous structure, for example, approximately 15%, 20%, or 25%, of the surface area of the substrate can be in direct contact with the ligaments of the highly porous structure.

A highly porous, three-dimensional metallic structure can be fabricated such that it comprises a variety of densities in order to selectively tailor the structure for particular orthopedic applications, for example, by matching the structure to surrounding natural tissue in order to provide an improved matrix for tissue ingrowth and mineralization. Such structures can be isotropic or anisotropic. In this regard, according to certain examples, an open porous metal structure can be fabricated to have a substantially uniform porosity, density, void (pore) size, pore shape, and/or pore orientation throughout, or to have one or more features such as porosity, density, void (pore) size, pore shape, and/or pore orientation being varied within the structure, or within a portion thereof. For example, an open porous metal structure can have a different pore size, pore shape, and/or porosity at different regions, layers, and surfaces of the structure. The ability to selectively tailor the structural properties of the open porous metal enables, for example, tailoring of the structure for distributing stress loads throughout the surrounding tissue and promoting specific tissue ingrown within the open porous metal. In some instances, a highly porous, three-dimensional metallic structure, once formed, will be infiltrated and coated with one or more coating materials such as biocompatible metals such as any of those disclosed herein.

In some examples, the porous metal structure can be a formed from a titanium alloy using an additive manufacturing process, such as with OsseoTi™, which is commercially available from Biomet Manufacturing, LLC (Warsaw, Ind., USA). Briefly, however, OsseoTi™ is highly biocompatible, has high corrosion resistance and includes a highly interconnected porous architecture that mimics the porous structure of human cancellous bone, which can enhance bone integration and in-growth. In one exemplary implementation, OsseoTi™ can include a porous construct with a porosity.

FIG. 10depicts an illustrative system1000for controlling/adjusting a fixation material thickness during implantation of a cup or shell of a prosthesis, in accordance with at least one example. The benefit of the system1000ofFIG. 10is that it provides the ability to control and adjust fixation material50thickness52as shown inFIG. 2E. The system1000can include a first set1000aof three or more first spacers200aformed of a biocompatible material such as a bone cement material. The first set1000aof three or more first spacers200acan have a generally spherical shape as previously described, having a first diameter210athat is sized to control the target thickness52of the fixation material50(FIG. 2E) that supports the orthopedic hip prosthesis60to a first target thickness. In some examples, the first set1000aof three or more first spacers200aare inserted into or embedded in the fixation material50(e.g.,FIG. 2D). The spacers200abeing implanted before the shell or cup of the prosthesis60(e.g.,FIG. 2E). When the prosthesis60is implanted, the spacers may be located in a gap (e.g.,FIG. 2E, 52) between the bone1and the prosthesis60. This gap can be approximated as the distance between the prosthesis60and the bone1.

In some examples, the system1000can also include a second set1000bof three or more second spacers200bthat can be used in the same manner described for the first spacers200a. The second set of spacers1000bcan have a generally spherical shape and a second diameter210bsized to control a target thickness52of a fixation material50that supports the prosthesis60to a second target thickness. The second diameter210bcan be different from the first diameter210ain order to provide the surgeon more options for controlling and adjusting the fixation material50thickness.

In some methods, the surgeon may want to select and use only spacers200a,200bfrom the first set1000aor the second set1000b. In other methods, the surgeon may want to select and use a combination of spacers200a,200bfrom different sets (1000a,1000b, etc.) having different diameters210a,210b. This added customizability allows the surgeon to better tailor the fixation material50target thickness52to the needs of the particular living being.

VARIOUS NOTES AND EXAMPLES

To better illustrate the devices and methods disclosed herein, a non-limiting list of embodiments is provided herein.

Example 1 is a method of anchoring an orthopedic hip prosthesis including a shell or a cup to an acetabulum of a living being, the method comprising: placing an augment at a bone surface of the acetabulum; applying a layer of fixation material over the bone surface in an amount sufficient to cover the augment; and implanting the prosthesis over the layer of fixation material to secure the prosthesis to the layer of fixation material.

In Example 2, the subject matter of Example 1 optionally includes wherein the augment is an anchor having a body including a first surface opposite a second surface and an opening extending through the body from the first surface to the second surface, the method further including: identifying a target bone location; inserting a fastener through the opening; and attaching the fastener to the target bone location to secure the anchor to the acetabulum, wherein after attaching the fastener to the target bone location, applying the layer of fixation material includes covering the anchor and the bone surface with the layer of fixation material, wherein the layer of fixation material forms a surrogate bone surface for the target bone location and bone surrounding the target bone location to support the prosthesis.

In Example 3, the subject matter of Example 2 optionally includes wherein the anchor is formed of a layer of porous material that promotes boney ingrowth, and the layer of porous material is shaped to cover a portion of the acetabulum.

In Example 4, the subject matter of any one or more of Examples 2-3 optionally include wherein the anchor includes a porous material that promotes boney ingrowth and the anchor is generally planar in shape.

In Example 5, the subject matter of any one or more of Examples 2-4 optionally include wherein the anchor includes a first portion having the opening and a second portion including a second opening, the second opening extending from the first surface to the second surface, the method further including inserting a second fastener through the second opening, and attaching the second fastener to the acetabulum at a second target bone location to secure the second portion of the anchor to the bone.

In Example 6, the subject matter of Example 5 optionally includes wherein the augment includes a hinge portion located between the first portion and the second portion, and the method further includes bending the augment at the hinge portion before anchoring the second portion to the second target bone location.

In Example 7, the subject matter of any one or more of Examples 1-6 optionally include wherein placing an augment at a bone surface includes placing three or more substantially spherical spacers at the bone surface after applying the layer of fixation material to the bone surface, and wherein placing the three or more substantially spherical spacers includes inserting the three or more spacers into the layer of fixation material in a triangular arrangement, the method further including pressing the prosthesis into the layer of fixation material until the prosthesis bottoms out on the three or more substantially spherical spacers.

In Example 8, the subject matter of Example 7 optionally includes wherein the layer of fixation material is a bone cement and wherein a presence of the three or more substantially spherical spacers in the bone cement controls a target thickness of the bone cement that supports the prosthesis.

In Example 9, the subject matter of Example 8 optionally includes wherein the target thickness of the bone cement is variable along the acetabulum.

In Example 10, the subject matter of any one or more of Examples 8-9 optionally include wherein a first spacer of the three or more spacers includes a first diameter, and a second spacer of the three or more spacers includes a second diameter that is different than the first diameter.

In Example 11, the subject matter of any one or more of Examples 1-10 optionally include wherein the augment is a substantially spherical spacer, and wherein placing the augment at the bone surface includes inserting a plurality of the substantially spherical spacer into the layer of fixation material after applying the layer of fixation material, and wherein implanting the prosthesis includes applying a force to the prosthesis to push the prosthesis into the layer of fixation material until the prosthesis bottoms out on the plurality of spacers.

In Example 12, the subject matter of Example 11 optionally includes wherein the plurality of the substantially spherical spacers includes three or more substantially spherical spacers, and wherein placing the plurality of spacers at the bone surface includes placing the plurality of spacers in a triangular arrangement.

In Example 13, the subject matter of Example 12 optionally includes wherein the layer of fixation material is a bone cement and wherein a presence of the plurality of spacers in the layer of fixation material controls a thickness of the layer of fixation material that supports the prosthesis.

In Example 14, the subject matter of Example 13 optionally includes wherein a target thickness of the bone cement corresponds to a diameter of the spacers.

Example 15 is a system for controlling fixation material thickness during implantation of an orthopedic hip prosthesis to an acetabulum of a living being, the system comprising: a set of three or more first spacers formed of a biocompatible material, the set of three or more first spacers having a generally spherical shape and a first diameter sized to control a target thickness of a fixation material that supports the orthopedic hip prosthesis when the set of three or more first spacers are embedded in the fixation material, wherein the fixation material occupies a gap between the orthopedic hip prosthesis and the acetabulum.

In Example 16, the subject matter of Example 15 optionally includes a second set of three or more second spacers, the set of second spacers having a generally spherical shape and a second diameter sized to control a target thickness of a fixation material that supports the orthopedic hip prosthesis when implanted, wherein the second diameter is different from the first diameter.

In Example 17, the subject matter of any one or more of Examples 15-16 optionally include wherein the set of three or more spacers, and the second set of three or more spacers are formed of a bone cement material.

Example 18 is an anchor for placement between a shell or cup of an orthopedic hip prosthesis and an acetabulum of a living being, the anchor comprising: a body having a first surface and a second surface opposite and spaced apart from the first surface, the body including a porous material that promotes boney ingrowth; and an opening extending from the first surface to the second surface, the opening sized and shaped to accept insertion of a fastener through the opening to be secured to the acetabulum.

In Example 19, the subject matter of Example 18 optionally includes wherein the first surface includes gripping formations to promote adhesion of the first surface to a fixation material, and the second surface includes the porous material that promotes boney ingrowth, and wherein the first surface is less porous than the second surface.

In Example 20, the subject matter of any one or more of Examples 18-19 optionally include wherein both the first surface and the second surface include the porous material that promotes boney ingrowth.

In Example 21, the subject matter of any one or more of Examples 18-20 optionally include wherein the body is a layer of porous material that supports boney ingrowth and is conformable to approximate a surface of an acetabulum of the living being.

In Example 22, the subject matter of Example 21 optionally includes wherein the body includes a first portion having the opening and a second portion including a second opening, the second opening extending from the first surface to the second surface, the anchor further comprising a hinge portion located between the first portion and the second portion, and wherein the anchor is bendable at the hinge portion.