Patent Application
20170049576
The disclosure relates generally to orthopedic medical implant devices for surgical joint fusion. More particularly, the disclosed subject matter relates to a joint fusion implant for the bones of the human foot, especially the metatarsophalangeal joints.
Orthopedic implant devices have been utilized to fully or partially replace existing skeletal joints in humans. There are many joints in the human foot, and the metatarsophalangeal (MTP) joint is one joint causing frequent problems.
The MTP joint is the joint between the head of a metatarsal bone and the base of a proximal phalange in a foot. A number of efforts have been made to partially or fully replace this joint. A metatarsophalangeal (MTP) implant is used for replacing a metatarsophalangeal joint. The efforts include partial or full replacement of the joint using silicone based materials or metal implant devices.
The present disclosure provides an orthopedic implant device for surgical joint fusion. More particularly, the present disclosure provides an implant such as a metatarsophalangeal (MTP) implant, and a method for making the implant. The present disclosure also provides a method of using the implant including surgical procedure for implanting the implant, for example, in a foot of a patient. These include, but are not limited to, the following aspects and embodiments.
In one aspect, an orthopedic implant device (or an implant) is provided. An exemplary implant is described in details in
In some embodiments, the inner layer and the outer layer have a solid or substantially solid structure, or closed nonporous structure to prevent soft tissue in-growth. Each of the inner layer and the outer layer comprises a metal, for example, titanium, titanium alloy, or stainless steel. In some embodiments, such a metal is titanium, or titanium alloy.
In some embodiments, the middle layer comprises two portions: the at least one portion of the middle layer providing the two nubs, and a portion (“middle portion” or “sandwiched portion”), which extends from the first end to the second end of the cylindrical portion, and is sandwiched between the inner layer and the outer layer. At least one portion of the middle layer providing the two nubs is porous. The “middle portion” (or “sandwiched portion”) can be porous or solid. The two portions of the middle layer are one unitary layer comprising a porous material in some embodiments. The middle layer may comprise porous titanium or titanium alloy. The porous material in the middle layer may have pores of any suitable size. The pore size may be in the range of from about 1 micron to about 2000 microns in diameter. In some embodiments, the pore size is higher than 5 microns, for example, from about 5 microns to about 100 microns in diameter, or from about 50 microns to about 1000 microns in diameter, or from about 400 microns to about 600 microns in diameter.
In some embodiments, the middle layer has at least one exposed surface having a predetermined surface roughness and configured to promote bone fixation through friction and bone ingrowth. In some embodiments, the middle layer may have a region with a smooth surface adjacent to the tip of the nubs or the end surfaces of the inner layer.
Examples of the implant provided in the present disclosure include but are not limited to a metatarsophalangeal (MTP) implant configured to fuse, fix or partially replace a metatarsophalangeal joint of a patient. Such an implant may be any other suitable implant configured to fuse, fix or partially replace a joint between two bones.
In another aspect, a method for making the implant described above is also provided. In some embodiments, the method comprises the following steps: forming an article for the implant using the technique of additive manufacturing, and optionally sintering the article at an elevated temperature to provide the implant. During the step of additive manufacturing, the method may comprises selective laser sintering, in which at least one portion of the article is sintered. In some embodiments, the method comprises a step of cleaning the article to remove excessive particles before an optional step of sintering the article at the elevated temperature.
In another aspect, the present disclosure also provides a method of using an implant, for example, the implant as described above, to fuse, fix or partially replace a joint of a patient between a first bone having a head and a second bone having a base. For example, an exemplary method is described in
The method further comprises a step of implanting an implant between the head of the first bone and the base of the second bone. The implant comprises a body having a cylindrical portion extending from a first end to a second end, a first nub extending from the first end of the cylindrical portion, and a second nub extending from the second end of the cylindrical portion. In the step of implanting the implant, the implant is inserted between the first bone and the second bone so that the two nubs of the implant are inserted into the two intramedullary canals, and two surfaces of the cylindrical portion on the first and the second ends are disposed on cortical rims of the first bone and the second bone.
In some embodiments, the method further comprises fixing the implant using a set of plates and screws during or after the step of implanting the implant. In an exemplary surgical procedure, a wire (for example, k-wire) may be inserted into the inner layer during the step of implanting the implant. In some embodiments, the implant is configured to fuse a metatarsophalangeal joint. The first bone may be a metatarsal bone. The second bone may be a proximal phalange in the same toe of the patient.
The implant provided in the present disclosure provides optimal shape and size, and excellent alignment with bones, and also provides excellent biocompatibility. For example, the implant allows bone growth from one end of the implant and the other end without interference of any soft tissue. The porous structure and/or rough surface described above promote bone ingrowth and fixation while the solid structure and smooth surface described above prevent tissue ingrowth.
The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not necessarily to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like reference numerals denote like features throughout specification and drawings.
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,” “implant” and the like are used interchangeably in the present disclosure. References to “prosthetic implant devices,” or “implant” 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 MTP 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.
All the 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.
Referring to
Based on the material composition or physical structure, body 11 includes an inner layer 18, an outer layer 22, and a middle layer 20. Inner layer 18, outer layer 22, and middle layer 20 may be made of the same material having the same chemical composition but different physical structures in some embodiments. Inner layer 18 has a first length (L1) extending from a tip 14-1 of the first nub 14 to a tip 16-1 of the second nub 16, and has a first central axis (C1) that is collinear with a central longitudinal axis (CL) of implant 10. Outer layer 22 provides an outer surface 22-1 of implant 10. As shown in
Middle layer 20 is disposed between inner layer 18 and outer layer 22. Middle layer 20 comprises a porous material in some embodiments. The inner layer 18 and at least part of middle layer 20 collectively provide the two nubs 14, 16. As shown in
In some embodiments, inner layer 18 and outer layer 22 have a solid or substantially solid structure. For example, inner layer 18 and outer layer 22 can be made of a material having no porosity or a porosity of less than 5% by volume (e.g., 0-2%). Outer layer 22 has an outer circumferential surface 22-1 that is substantially smooth, for example, having a roughness parameter smaller than 5 microns. Inner layer 18 has an inner circumferential surface 18-1 and two end surfaces 18-2 substantially smooth, for example, having a roughness parameter smaller than 5 microns. Each of inner layer 18 and outer layer 22 comprises a metal such as, for example, titanium, titanium alloy, or stainless steel to list only a few possible metals. In some embodiments, such a metal is titanium, or titanium alloy. The titanium can be of high purity, for example, 95-100%. In some embodiments, each of inner layer 18 and outer layer 22 is made of pure and solid titanium, or solid titanium alloy. In some embodiments, outer layer 22 has two end surfaces being rough. The end surfaces of outer layer 22 may be knurled, matted or patterned in some embodiments. The end surfaces of outer layer 22 may have some small protuberances.
In some embodiments, middle layer 20 comprises two portions. As best seen in
In some embodiments, the whole middle layer 20 is made of porous titanium such as, for example, BIOFOAM® material available from Wright Medical Inc, although other porous materials can be used. BIOFOAM® material is made of 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. Such porous titanium may have a compression strength, for example, in the range of from about 50 to about 100 MPa.
Middle layer 20 may have a closed nonporous structure to promote bone fixation through friction and bone ingrowth. In some embodiments, middle layer 20 has at least one exposed surface having a predetermined surface roughness, which might be in any suitable range. The surface roughness parameter may be equal to or higher than 5 micron, or higher than 10 or 20 microns. In some embodiments, the middle layer may have a region 24 with a smooth surface adjacent to the tip 14-1, 16-1 of nubs 14, 16, which is also adjacent to the end surfaces 18-2 of the inner layer 18 as best seen in
Implant 10 described above can be used as a metatarsophalangeal (MTP) implant configured to fuse a metatarsophalangeal joint of a patient. However, one of ordinary skill in the art will understand that implant 10 can be used to fuse, fix or partially replace another joint between two adjacent bones.
The implant can be of any suitable size, which can be determined by the size of the joint and associated bones. Table 1 lists some examples of implants for MTP joint fusion.
Referring now to
At step 42, an article for an implant 10 is prepared. In some embodiments, the article for implant is prepared using a suitable method, for example, using an additive manufacturing technique. The article can be also made through three-dimensionally (3-D) printing. The article is similar to or about the same as the final implant 10, with consideration of possible shrinkage in the later sintering processes. Computer-aided design (CAD)/Computer-aided manufacturing (CAM) technologies can be used in combination with the additive manufacturing technique. An exemplary implant 10 can be designed using CAD. A model including related design parameters can be output from a computer. The related design parameters for implant 10 as a final product include shape, configuration, dimensions, porosity, and surface roughness of each portion of implant 10.
Any equipment suitable for additive manufacturing of metals can be used at step 42. Physical parameters of the article implant such as porosity and density of the material in each location can be correspondingly adjusted by the additive manufacturing equipment. Examples of the material used include but are not limited a metal powder such as titanium, titanium alloy, cobalt chromium alloy or stainless steel. Examples of a suitable additive manufacturing equipment is available from, for example, EOS of Germany and Arcam of Sweden to list only two possible examples. Selective laser sintering is applied while or right after each point or portion is printed. 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 46, the article is cleaned to remove excessive particles, which are not attached with or are loosely attached to the article. Step 46 may be optional, and may be performed by applying high pressure air or other gases to the surface of the article. The excessive particles can be blown away.
At step 48, which is optional, the article is sintered at an elevated temperature to provide the implant 10 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 10. Resulting implant 10 provides excellent strength and stiffness.
Referring now to
At step 52, an incision is performed proximal to and along the joint of the patient.
When a MTP implant is used in a MTP joint, a dorsal longitudinal or dorsal medial incision can be used as a surgical approach. The toe 70 to be operated upon can be grabbed by a hand 74 of a medical professional during the surgery. Tools such as retractors 72 also may be used. The incision can be made along a metatarsal bone. The incision can be made proximal to the interphalangeal joint, and extended over the dorsum of the MTP joint medial to the extensor hallucis longus (EHL) tendon. The incision may end on the medial aspect of the metatarsal, 2-3 cm proximal to the joint.
At step 54, the head 78 of the first bone 68 and the base 79 of the second bone 69 are exposed.
Collateral ligaments in the joint capsule 71 can be incised and released to expose the base of the proximal phalanx and the metatarsal head. The phalanx plantarly can be also displaced before exposing the metatarsal head 78. Suitable tools such as retractors 76 can be used to expose the head 78. With a powered drill, a K-wire (Kirschner wire) 80 is placed proximally through the center of the metatarsal head 78. With a Jacobs chuck, a Cannulated AO Quick Connect can be attached to the power driver and connect a female reamer 82. Reamer 82 is placed over K-Wire 80 and gently ream the metatarsal head until bleeding subchondral bone becomes visible on the joint surface. K-wires used in the present disclosure may not be the same K-wire in each step. Reamer 82 is used to prepare the intramedullary canal for the nub of the implant.
At step 56, the head 78 of the first bone 68 and the base 79 of the second bone 69 are reamed to prepare two intramedullary canals, including a first canal in the first bone 68 and the second canal in the second bone 69.
At step 58, implant 10 is implanted between the head of the first bone 68 and the base of the second bone 69.
At step 60, implant 10 is fixed using a set of fusion plates 90 and screws 92 in some embodiments.
At step 62, a wire (for example, k-wire) is inserted into the inner layer 18 or other locations. Step 62 may be optional, and may be performed during step 58 of implanting the implant 10. All K-wires are removed when plate 90 is securely fixed. Surgical closure is then performed in the normal fashion.
The implant described herein advantageously is the optimal shape and size for the MTP joint such that the implant provides better alignment with bones, and also provides better biocompatibility. For example, the implant allows bone growth from one end of the implant to the other end without interference of any soft tissue. The porous structure and/or rough surface described above promote bone ingrowth and fixation while the solid structure and smooth surface described above prevent tissue ingrowth.
In accordance with some embodiments, during an implanting surgery of an MTP implant, nubs 14, 16 of implant 10 are inserted into intramedullary canals in the metatarsal bone 68 and the base of the proximal phalange 69, and the surfaces of both ends of the middle body rests on the cortical rim of each bone. Solid inner layer 18 allows for easy insertion of a k-wire during the surgery and also enhances strength of the MTP implant. The nubs 14, 16 and both ends of body 11, which are made of porous titanium (e.g., BIOFOAM®), have a roughed surface to promote bone fixation through friction and bone ingrowth. This configuration allows bone growth from one end of the MTP implant to the other end without interference of any soft tissue. Solid outer layer of the body also prevents possible growth of soft tissue thereon. A set of plates and screws are used for fusion of the MTP joint in some embodiments. Fusion of this joint is most often performed for treatment of end-stage hallux rigidus, severe Hallux Valgus, rheumatoid and post-traumatic arthritis, and for revision of nonunions. The combination of plates and screws provides for a very stiff and stable construct, and ensures that the hallux is fused in proper anatomic alignment.
Exemplary method 50 provides rapid fusion of the joint without excessive shortening of the toe or removal of structural bone, and correct orientation of the MTP joint for natural gait biomechanics and footwear comfort. Exemplary method 50 also enables a high fusion rate and early return to function by creating a very stable fusion construct.
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.
