Patent Application
20170056190
This disclosure generally relates to orthopedic medical implant devices for surgical joint fusion. More particularly, the disclosed subject matter generally relates to a joint fusion implant for the bones of the human foot, especially the subtalar joint.
Orthopedic implant devices have been utilized to fully or partially replace existing skeletal joints in humans. There are many joints in the human foot, such as the subtalar joint, which frequently suffer from abnormal wear or other defects.
A subtalar fusion is a common surgical procedure for correction of calcaneal fractures, abnormal wear of the subtalar joint, flatfoot deformity, and/or other abnormalities in the subtalar joint. Fusion of the subtalar joint is generally achieved with calcaneal screws. Current solutions do not correct angular deformities that may be present in the subtalar joint, for example, in patients with flatfoot deformities.
In various embodiments, a subtalar implant is disclosed. The subtalar implant includes a body having a sidewall defining an outer perimeter of the body. The sidewall defines an inner volume. A porous material is disposed within the inner volume. The porous material has a porosity configured to promote bone ingrowth. The porosity of the porous material can be about 30% to about 70% by volume. The sidewall can be a smooth, solid structure configured to prevent bone in-growth.
In some embodiments, a subtalar implant system is disclosed. The subtalar implant system includes an implant and a bone screw. The implant includes a body having a solid sidewall defining an outer perimeter of the body. The solid sidewall defines an inner volume. The implant further includes a porous metal material disposed within the inner volume, the porous metal material having a porosity of about 30% to about 70% by volume. The bone screw is sized and configured for fusing a subtalar joint.
In some embodiments, a method of correcting a subtalar joint deformity is disclosed. The method includes preparing a subtalar joint for receiving an implant. The implant includes a body having a sidewall defining an outer perimeter of the body. The sidewall defines an inner volume. A porous material is disposed within the inner volume. The porous material has a porosity configured to promote bone ingrowth. The implant is positioned in the prepared subtalar joint. A screw is driven through a first bone of the subtalar joint into a second bone of the subtalar joint to fuse the first and second bones.
The features and advantages of the present invention will be more fully disclosed in, or rendered obvious by the following detailed description of the preferred embodiments, which are to be considered together with the accompanying drawings wherein like numbers refer to like parts and further wherein:
This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivative thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.
In the present disclosure the singular forms “a,” “an,” and “the” include the plural reference, and reference to a particular numerical value includes at least that particular value, unless the context clearly indicates otherwise. When values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. As used herein, “about X” (where X is a numerical value) preferably refers to ±10% of the recited value, inclusive. For example, the phrase “about 8” preferably refers to a value of 7.2 to 8.8, inclusive. Where present, all ranges are inclusive and combinable. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, “2-5”, and the like. In addition, when a list of alternatives is positively provided, such listing can be interpreted to mean that any of the alternatives may be excluded, e.g., by a negative limitation in the claims. For example, when a range of “1 to 5” is recited, the recited range may be construed as including situations whereby any of 1, 2, 3, 4, or 5 are negatively excluded; thus, a recitation of “1 to 5” may be construed as “1 and 3-5, but not 2”, or simply “wherein 2 is not included.” It is intended that any component, element, attribute, or step that is positively recited herein may be explicitly excluded in the claims, whether such components, elements, attributes, or steps are listed as alternatives or whether they are recited in isolation.
For brevity, “orthopedic implant devices,” “orthopedic implant,” “implant” and the like are used interchangeably in the present disclosure. References to “orthopedic implants,” or “implants” made in the present disclosure will be understood to encompass any suitable device configured to fuse, fix or partially replace a joint between two bones, including but not limited to a subtalar implant.
References to “solid” or “substantially solid” are made relative to references to “porous” and “substantially porous.” Unless expressly indicated otherwise, references to “solid” or “substantially solid” made below will be understood to describe a material or structure having 0-5% by volume (e.g., 0-2% by volume) of porosity. A small amount of pores, particularly closed pores, may be embedded inside a solid or substantially solid material.
Unless expressly indicated otherwise, references to “porous” or” substantially porous” made below will be understood to describe a material or structure having a significant amount of pores, for example, higher than 5% by volume of porosity. A porous or substantially porous materials may have pores, particularly open pores on the surface. The porosity on or adjacent to the surface may be higher than 5% by volume in some embodiments. When a material monolith is porous, the porosity may be in the range from 20-95% (e.g., 50-80%) by volume.
Data of pore size and porosity were measured following the FDA's guidance: “Guidance Document for Testing Orthopedic Implants With Modified Metallic Surfaces Apposing Bone or Bone Cements,” 1994. Each part was sectioned using electric discharge machining to produce smooth and even surfaces that represent cross-sections through the porous material. Green modeling clay was used to fill the pores of the cut face. A razor blade was used to remove any excess modeling clay from the cross section. Images were taken at 75× magnification using a Zeiss microscope with a camera attachment. Parts were oriented in a way to give best possible color contrast between the titanium and the modeling clay. Simagis image analysis software (Smart Imaging Technology, Houston, Tex.) was used to determine the percent porosity, strut diameter, interconnecting pore diameter and pore cell diameter. The pore size (or interconnecting pore size) was defined as the approximately circular pore opening that connects larger pore cells.
In various embodiments, the present disclosure generally provides an orthopedic implant for use in a joint, such as a subtalar joint, during bone fusion. The implant comprises a sidewall defining a predetermined shape having an inner volume. The inner volume is filled with a porous material. The sidewall defines at least one opening configured to expose a portion of the porous material. The porous material has a predetermined porosity to facilitate bone ingrowth where desired. The sidewall is configured to support at least a portion of a load experienced by the joint.
In some embodiments, the sidewall 6 defines a perimeter of the body 4 having at least one opening, such as, for example, an open top edge 10 and/or an open bottom edge 12. For example, in the illustrated embodiment, the sidewall 6 of the body 4 defines a horse-shoe shape having an open top edge 10 and an open bottom edge 12. In some embodiments, the sidewall 6 can partially and/or completely cover the top edge 10 and/or the bottom edge 12 of the body 4. In other embodiments, a portion of the sidewall 6 may be omitted to expose a section of the internal volume 8 along the perimeter of the sidewall 6.
In some embodiments, the sidewall 6 comprises a solid material, such as, for example, a solid metal. For example, in some embodiments, the sidewall 6 comprises a metal having a porosity of less than about 5% by volume. In some embodiments, the sidewall 6 comprises a substantially smooth surface. The material of the sidewall 6 may be selected to inhibit soft tissue ingrowth onto and/or through the sidewall 6. Suitable exemplary biocompatible materials include, but are not limited to, titanium, titanium-alloys, steel, and/or alloy steel.
In some embodiments, the internal volume 8 defined by the sidewall 6 is filled with a porous material 14. The internal volume 8 may be partially and/or completely filled with the porous material 14. The porous material 14 may have pores of any suitable size or ranges. For example, The pore size may be in the range of from about 1 micron to about 2000 microns in diameter, for example, from about 100 microns to about 1000 microns in diameter, or in the range of from about 400 microns to about 600 microns in diameter. The pores can be continuous and open. The porosity can be in the range from about 30% to about 70% by volume in some embodiments, such as, for example, from about 50% to 70%, from about 55% to about 65%, and/or any other suitable range. The porous material 14 may comprise any suitable biocompatible material.
In some embodiments, the porous material 14 is made of porous titanium such as, for example, BIOFOAM® available from Wright Medical Inc., although other porous materials can be used. BIOFOAM® is made of commercially pure titanium and has pores, for example, of roughly 500 microns in diameter. The porosity can be up to 70% by volume. Such porous titanium has continuous and open pores. The porous titanium or titanium alloy mimics the strength and flexibility of human bone, and also has a high surface coefficient of friction.
In some embodiments, the porous material 14 has at least one exposed surface having a predetermined porosity and is configured to promote bone fixation through friction and bone ingrowth. In various embodiments, pore size may be in the range of from about 1 micron to about 2000 microns in diameter, for example, from about 100 microns to about 1000 microns in diameter, or in the range of from about 400 microns to about 600 microns in diameter. In some embodiments the porous material 14 has exposed surfaces at the top edge 10 and/or bottom edge 12 of the sidewall 6. The exposed surfaces of the porous material 14 are positioned to interact with an implantation site to promote bone ingrowth through the internal volume 8. In some embodiments, a bone-growth agent is included within the porous material 14 to encourage bone ingrowth.
In some embodiments, the implant 2 is configured to support a predetermined load. The predetermined load can correspond to a load experienced by a joint and/or a bone into which the implant 2 is inserted. For example, in some embodiments, the implant 2 is a subtalar implant configured to support a maximum force experienced by a subtalar joint of a patient. In other embodiments, the implant 2 is configured to support some multiple of the force experienced by the joint and/or the bone, such as, for example, 1.5 times the maximum force, twice the maximum force, three times the maximum force, and/or any other suitable multiple. The solid sidewall 6 and the porous material 14 allow the implant 2 to support loads greater than the strength of the porous material 14 alone while providing the flexibility and bone ingrowth of a porous material 14. The porous material 14 is configured to contact bone at the implantation site to promote bone ingrowth and increase the strength of the implant/bone connection. The sidewall 6 prevents compression and/or distortion of the porous structure 14 when a force greater than the compression force of the porous material 14 is experienced at the implantation site.
In some embodiments, the implant 2 is sized and configured for implantation at a joint, such as, for example, a subtalar joint. The implant 2 may be configured to correct one or more defects of the subtalar joint, such as, for example, a flatfoot deformity. However, one of ordinary skill in the art will understand that implant 2 can be used to fuse, fix, and/or partially replace another joint between two bones.
The implant 2 can be of any suitable size, which can be determined by the size of the joint and associated bones. Table 1 lists some exemplary embodiments of implants for subtalar joints.
In some embodiments, one or more of the dimensions of the implant 2 may be variable. As shown in
The implant 2 is located within the subtalar joint 30 to correct angular deformities of the subtalar joint 30, such as a flatfoot deformity. The sidewall 6 of the implant 2 provides for angular correction of the subtalar joint 30 while providing the mechanical strength necessary to hold full ankle loading. In some embodiments, the implant 2 is paired with a bone screw 36 configured to fuse the subtalar joint 30. In some embodiments, the body of the implant 2 includes a shape configured to allow implantation of the bone screw 36 according to one or more known implantation techniques. For example, in some embodiments, the implant 2 has a horse-shoe shape sized and configured to allow for implantation of the bone screw 36 according to one or more known methods.
In some embodiments, the implant 2 is positioned in the joint 30 such that at least one open side 10, 12 of the implant 2 is in contact with the talus 32 and/or the calcaneus 36. The open side(s) 10, 12 allows a porous material 14 located within a cavity 8 to contact the surface of bones 32, 34 to promote bone ingrowth. As discussed above, the porous material 14 has a predetermined porosity and surface roughness parameter configured to promote bone ingrowth. For example, in some embodiments, the porous material 14 includes a BIOFOAM® material having a porosity of up to 70% by volume.
During surgery, the trial system 40 is used to determine an appropriately sized implant for insertion into a resected joint. After the joint has been prepared by the surgeon, the surgeon selects a trial 50 corresponding to an implant having predetermined dimension, such as, for example, one of the implant sizes in Table 1 above. The trial 50 is inserted into the prepared joint. After inserting the trial 50, the surgeon can determine whether the trial 50 is properly sized for the resected joint. If the selected trial 50 is the proper size, the surgeon can proceed with installing the implant. If the selected trial 50 is the wrong size, the surgeon can select a larger/smaller trial. This process can be repeated until the proper trial 50 has been identified. The surgeon can then select an implant 2, 102, 202 size corresponding to the selected trial 50.
In step 304, the joint is distracted. The joint may be distracted using any suitable technique and/or device as known in the art.
An additive manufacturing system suitable for metal generation, such as, for example, a 3D printing process or a selective laser sintering process, can be used at step 404 to convert the model into an implant based on the related design parameters. Physical parameters of the implant such as porosity and density of the material in each location can be correspondingly adjusted by the additive manufacturing system based on the model. Examples of the material used include but are not limited a metal powder such as titanium, titanium alloy or stainless steel. In some other embodiments, each portion of an implant 2 may be molded separately and then combined together to form a complete implant. The molding may be achieved through compression molding of metal powders.
At an optional step 406, at least one portion of the implant is sintered. In some embodiments, step 406 is performed using a laser during step 404 of the additive manufacturing process of the implant such that the sintering at step 406 may be performed concurrently with step 404. Laser sintering is applied while or right after each point or portion is manufactured. Direct laser sintering or selective later sintering may be used. One of ordinary skill in the art will understand that other sintering methods can be used.
At step 408, the implant is cleaned to remove excessive particles, which are not attached with or are loosely attached to the implant. Step 408 may be optional. In some embodiments, step 408 is performed before step 406 of sintering the implant at the elevated temperature. The step 408 of cleaning may be performed by applying high pressure air or other gases to the surface of the implant. The excessive particles can be blown away.
At step 410, the implant is sintered at an elevated temperature to provide the implant 2 described above. Such a sintering can be performed in an oven or furnace. The heat sintering can be performed at any suitable temperature. The heat sintering of titanium may be performed at a temperature, for example, in the range from about 1000 to about 1500° C. The temperature and time can be selected to control the physical parameters of final implant.
Although the subject matter has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.
