Patent Application
20140277553
Embodiments of the invention pertain to surgery for the repair of skeletal joints.
In the human arm, the side of the distal ulna articulates with the side of the distal radius, thereby allowing the hand pronation and supination. Disease or trauma sometimes requires replacement of the head of the distal ulna. Various materials and designs for replacement parts are known. However, there remains a need for better designs that will provide the surgeon with appropriate options during surgery while not requiring a large quantity and inventory of parts.
Referring now to
In a Type I joint, the surface of the articulation is substantially parallel to the ulnar centerline. In Type II joints, the surface of the articulation is inclined to the ulnar centerline in one direction. In Type III joints, the surface of the articulation is inclined to the ulnar centerline in the opposite direction.
All three of these spatial relationships occur in normal human anatomy, in different individuals. Based on a study of fifty cadaveric wrist specimens. Tolat et al (Tolat A R, Stanley J K, Trail I A, A cadaveric study of the anatomy of and stability of the distal radioulnar joint in the coronal and transverse planes, J Hand Surg. Vol. 21B, No. 5, October 1996) report the distribution of the three types as follows; Type I, 55%; Type II, 33% and Type III, 12%. In the Type I wrist the DRUJ angle was essentially zero. The distribution of the DRUJ angles for Type II and Type III wrists, as reported by Tolat, et al., are shown in Table 1. Type II DRUJ angles were predominantly in the 10 degree to 20 degree range whereas the Type III DRUJ angles were mainly in the 15 degree to 20 degree range.
Tolat et. al. report DRUJ angles ranges for all Types (I, II and III) as groupings of 0 degrees, and ranges of 10 to 15 degrees, 16 to 20 degrees and 21 to 24 degrees. The occurrence of DRUJ angles based on all fifty of the Tolat et. al. cadaver specimens and representing each range of DRUJ angles by its average is shown in Table 2. Furthermore, the information of Tables 1 and 2 is summarized in the graph of
Embodiments of the invention provide an orthopedic device comprising a stem and a head and a liner, wherein an external shape of the head is not symmetric with respect to its midplane, and wherein the head has a hole completely therethrough.
Embodiments of the invention provide an orthopedic device comprising a stern and a head and a liner, wherein the head can be assembled to the stem and the liner in a first configuration providing a first external shape and can be assembled to the stem and the liner in a second configuration providing a second external shape different from the first external shape.
Embodiments of the invention provide a kit comprising multiple ulnar heads that have different external shapes, and which can be mated with a common stem or common liner or both.
Embodiments of the invention are further described in the following illustrations.
Referring now to
Referring now to
Referring now to
In connection with the head 200, there may be described a bounding plane such that the bounding plane is perpendicular to the centerline 12, and the bounding plane touches the head from a given direction but does not intersect the head (i.e., the head 200 exists on one side of the bounding plane and touches the bounding plane but does not exist on the opposite side of the bounding plane).
More specifically, there may be a first bounding plane 210 that non-intersectingly touches the head 200 from a first direction the head contacts the plane but only from one direction, so that the head does not extend to the opposite side of the plane). Similarly, there may be a second bounding plane 212 that non-intersectingly touches the head 200 from a second direction opposed to the first direction. The first bounding plane 210 and the second bounding plane 212 are parallel to each other. Furthermore, a midplane 214 may be defined as a plane that is halfway between the first bounding plane 210 and the second hounding plane 212. The midplane 214 may be parallel to the first bounding plane 210 and to the second bounding Wane 212.
The head 200 may have an external surface 220 that has a portion that is either cylindrical (in the case of Type I anatomy) or frustoconical (in the case of Type II or Type III geometry). It is also possible that such surface 220 may be very gently curved. External surface 220 may define a tangent line 230. Tangent line 230 may coincide with a portion of the surface in the cylindrical or frustoconical situation, or more generally, tangent line 230 may be tangent to the external surface of the head 200 at the midplane of head 200. The angle between tangent line 230 and centerline 12 may match or approximately match the Distal Radioulnar Joint angle as discussed elsewhere herein. Generally, head 200 may have curved fillets to blend between adjacent geometric portions.
With respect to the midplane 214, the head 200 may be either symmetric or non-symmetric. More specifically, the external shape of the head 200 may be either symmetric or non-symmetric with respect to the midplane 214. If the had 200 is symmetric with respect to the midplane 214, such head 200 may be appropriate to be used for a Type I ulnar geometry. If the head 200 is non-symmetric with respect to the midplane 214, such head 200 may be appropriate to be used for a Type II or a Type III ulnar geometry.
The head 200 may comprise a retention feature that is suitable to interact with a complementary feature in another component to retain the head 200 to another component. For example, in its interior the head 200 may comprise a retention lip 240 that protrudes inwardly more than most of the rest of the internal surface of head 200. As illustrated in
The head 200, together with other parts described herein, may be such that the head 200 can be assembled to other parts of the implant 10 in either of two configurations for a given set of parts. For a given set of parts, one configuration can provide a slope of the external surface of head 200 in one direction, with respect to centerline 12, and the other configuration can provide a slope of the external surface of head 200 in the opposite direction.
Referring now to
Referring now to
The dimensions of various features of the stem 100, the head 200 and the liner 300 may be such that, assuming there has been pre-assembly of head 200 with liner 300, the liner 300 may be slid over the post 130 of stem 100 during a final assembly process in such a way that there is only a relatively small amount of tensile stress created in the head 200 during the process of sliding liner 300 over post 130. For example, such assembly might require only localized bending in liner 300 near the midplane of liner 300. More specifically, inward protrusion 334 may deflect radially outward, and the corresponding depression 330 on the outer surface of liner 330 may deflect similarly, to allow liner 300 with head 200 already engaged with liner 300) to slide into its assembled position with respect to post 130. Liner 300 may have a midplane that is defined similarly to the midplane 214 of head 200, and which in the assembled configuration may coincide with midplane 214 of head 200. Such bending could temporarily urge regions of liner 130 into empty interior localized space (depression 336) between liner 300 and head 200 to accomplish the snapping-in, and this bending could be relieved when the radially inward bulge 334 of liner 300 cooperates with groove 134 in post 130 of stern 100. Similarly, the dimensions of various features of the head 200 and the liner 300 may be such that, during a process of assembling head 200 with liner 300, there is only a relatively small amount of tensile stress created in the head 200 during that process. During this process, external bulges 324 of liner 300 may be compressed inward as needed to avow liner 300 to pass into its engaged position with respect to head 200. In regard to the process of sliding or snapping liner 300 into the interior of head 200, it is possible that that process could be performed while the exterior of head 200 is restrained or even compressed, so as to avoid or minimize tensile stresses in head 200 during the snapping. All of these considerations can be useful in minimizing risk to the integrity of the head 200, because in some embodiments head 200 may comprise a material that is brittle. It can be understood that a small magnitude of tensile stress may be created in head 200 during snapping-together of various components, and an even smaller magnitude of tensile stress may exist during frictional retention of the various components after snapping-together has been completed. However, this magnitude is tolerable and is smaller than would result from a assembly based on wedges or frustoconical shapes such as a Morse locking taper such as is described in U.S. Pat. No. 6,997,958. Related designs of possible engagement features are illustrated in commonly assigned U.S. Pat. Nos. 8,034,116 and 8,366,780, which are incorporated herein by reference.
According to the design of liner 300 illustrated in
It is possible that rounded corners may be provided in certain appropriate places on stem 100, head 200 and liner 300, and sharper corners may be provided in other appropriate places, so that snapping-together at the various parts can be performed relatively easily, but disassembly is more difficult. It is even possible that such features could be designed so that disassembly is impossible unless one or more of the parts is destroyed.
It is further possible that the dimensions of various features of the stem 100, the head 200 and the liner 300 may be such that when all three of them are assembled, there is friction among the various components so that the head 200 does not rotate freely with respect to either liner 300 or stem 100. It is possible that the relevant features of stem 100, the head 200 and the liner 300 might all be axisymmetric so that there is no preferred angular orientation and in such a situation rotation would be possible if dimensions permitted. However, in the present design it is possible that there could be sufficient friction to resist rotation, east for the conditions likely to be experienced during the activities of a patient who has received an implant.
In an embodiment of the invention, there may be provided a kit that comprises a stern 100, a head 200 and a liner 300, wherein the head 200 is annular and has a hole therethrough as described elsewhere herein and permits assembly in two different configurations for a given set of parts. The head 200 may be non-symmetric with respect to a midplane 214, as described elsewhere herein. The kit may further include another head 200 that is symmetric with respect to the midplane 214. Such a kit may provide the surgeon with a lame number of configuration choices for a given number of parts. Such elements and assemblies are illustrated in
The head 200 may have, on its external surface 220, a material that may be selected for its properties of biocompatibility and resistance to wear. Such a material may be in the form of a coating that covers a substrate material making up the bulk of head 200. As an example, the coating material may be pyrolytic carbon (pyrocarbon) and the substrate material may be graphite. Graphite and pyrolytic carbon both are brittle materials, and as such are only able to tolerate a limited amount of tensile or bending stress before breaking. This stress limit can be taken into account in the design of the implant such as in features relating to the snapping-together action described elsewhere herein.
It has been found that pyrolytic carbon-coated, graphite substrates can be used to create prostheses having a modulus of elasticity that is within about 150% of the modulus of elasticity of natural bone; thus, this is considered to be an advantageous material for manufacturing such prostheses. A particular pyrocarbon is marketed as On-X® carbon (On-X Life Technologies, Inc. Austin, Tex.) (see U.S. Pat. Nos. 5,641,324 and 5,262,104). Pyrocarbon has advantageous properties for use in orthopedic prostheses such as are described herein, particularly when such is coated upon a substrate of istropic, fine grain graphite. The result is the creation of a strong prostheses that has excellent biomechanical properties. Because pyrocarbon is both physiologically inert and biochemically compatible with bone, and because the elastic modulus of such a pyrocarbon-coated graphite substrate is very close to that of cortical bone, such a prosthesis is highly biomechanically compatible and may be effectively used in such orthopedic implants, particularly those at joints within the human body where its articular surface is important. In addition to its highly compatible modulus of elasticity, pyrocarbon, provides excellent wear characteristics at its interface with bone and also with cartilage, resulting in an implant which is highly bone compatible. This is discussed in “Wear characteristics of the canine acetabulum against different femoral prostheses, ” by Stephen D. Cook, Kevin A. Thomas, Marcus A. Kester (J. Bone Joint Surg [Br] 1989; 71-B:189-97) vol. 71-B, No. 2, March 1989.
The liner 300 may be made of UHMWPE (ultra high molecular weight polyethylene). Such a material is biocompatible and has softness appropriate to allow snapping-together of the described parts without imposing a large tensile or bending stress in the head 200, which, as described elsewhere herein, might be brittle and might have limitations on the allowable tensile or bending stress. Of course, other polymeric materials and other materials generally are also possible. Washer 400 also may be made of UHMWPE. Washer 400 could be made of either the same material as liner 300 or a different material.
The stem 100 may comprise a biocompatible metal such as titanium or a titanium alloy such as is known in the art. Other materials are also possible. In general, any of the components described herein may be made of any biocompatible material having desired mechanical properties. Categories of materials for such components include metals, ceramics, polymers, and various forms of carbon as described herein or as known in the art.
It is possible to create a kit that contains heads 200 representing more than one external angle. For example, a kit may comprise one head 200 that has an external surface that is essentially parallel to the centerline 12, and it may further contain one or more heads 200 that have external surfaces that are not parallel to the centerline 12. Such heads 200 may be mountable in two opposite orientations as described elsewhere herein in order to address both Type II and Type III wrists. The number of such heads 200 provided in a kit may be determined by how finely one wishes to match external slope to a patient's anatomy. It is also possible that a kit might contain no head 200 that has its external surface exactly parallel to the centerline 12, but might contain a head 200 whose external surface angle is close to being parallel to the centerline 12, and might further contain other head(s) whose external surface has larger angle with respect to the centerline 12. Of course, a kit also might contain the described collection of head angles in several different dimensional sizes to address various overall body sizes of patients. It would be optional as to whether different dimensional sizes of heads 200 would be designed to require different dimensional sizes of other parts (stem 100, liner 300).
For the selection of a kit of drier head replacement devices having a invertible head 200 as described herein, one possible set of parts would be parts that provide four separate DRUJ angles so as to allow for treating essentially all wrist anatomies. A head portion with a DRUJ angle of 0 degrees would be appropriate for approximately 55% of patients (i.e., all of Type I wrists), a head portion with a DRUJ angle of 12.5 degrees would be appropriate for approximately 20% of patients. (81% of Type II and 2% of Type III wrists), a head portion with a DRUJ angle of 18 degrees would be appropriate for approximately 10% of patients (6% of Type II and 67% of Type III wrists) and a head portion with a DRUJ angle of 22.5 degrees would be appropriate for approximately 6% of patients (13% of Type II and 17% of Type II wrists). Further addressing issues of overall dimensions, an implant system with four DRUJ angles as just described and with three different head diameters would result in a total of 12 head components.
From a practical point of view, providing four differently-angled heads, for a given size scale or dimension, in a DRUJ kit might result in an undesirably large kit. As an alternative, it would be possible to produce a kit containing parts that provide three DRUJ angles, such as 4 degrees, 10 degrees and 16 degrees. The choice of 4 degrees, 10 degrees and 16 degrees was somewhat arbitrary and would be intended to cover a broad range of the patients represented in Table 2 and to provide prototype device that can be handled and observed to appreciate what the DRUJ angle variations look like in actual form. It should be noted that a DRUJ angle of 4 degrees was chosen to represent the Type I joint anticipating that there is some actual variation about the zero degree Type I angle. In such a situation there would not be provided a head whose external surface angle is exactly zero degrees or whose external surface is exactly cylindrical.
With use of the designs presented herein, a head 200 may be mated with the liner 300 and the stern 100 in a first configuration and in a second configuration, with the two configurations providing different external surface angle characteristics.
Alternatively, as illustrated in
All patents, patent applications and publications referred to herein are incorporated by reference in their entirety. The various features disclosed herein can be combined in any combination. Although the invention has been disclosed with various embodiments, the invention is not limited thereby, and is to be limited only the scope of the appended claims.
While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
The indefinite, articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases end disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements): etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of,” “Consisting essentially, ” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended. i.e., to mean including but not limited to.
| Number | Date | Country | |
|---|---|---|---|
| 61783553 | Mar 2013 | US |
